ELECTROCHEMICAL TREATMENT OF WASTEWATERS DRIVEN BY REVERSE ELECTRODIALYSIS PROCESSES

Wastewater treatment technology is undergoing a transformation due to more restrictive regulations governing the dischar ge and disposal of hazardous pollutants. Electrochemical based technologies are very promising methods for treating wastewaters containing organic and inorganic pollutants resistant to biological processes or toxic for microorganisms. These methods present numerous advantages including the utilisation of a green reagent such as the electron, very high removal of numerous recalcitrant pollutants, efficient disinfection, high flexibility and no necessity to transport or stock chemical oxidants or reducents. O n the other hand, a wide utilisation of such methods is likely to…

Electrochemical conversion of carbon dioxide: effect of the cell and of the operating parameters on the performances of the process.

Recycling technologies of CO2 allow to introduce renewable energy in the chemical and energy chain, storing a renewable energy in the chemical form. In this context, electrochemical conversion of CO2 is considered one of the more interesting approaches, using excess electric energy from intermittent renewable sources. (1) Furthermore, products can be selectively controlled by changing the operating conditions of electrolysis. In particular, in the last years, an increasing attention has been devoted to the electrochemical conversion of CO2 to formic acid or formate in water. (2,3,4) The main hurdle of the reduction of CO2 from water solution is the low CO2 solubility in water. In this work,…

Effect of transition metals and homogeneous hydrogen producers in the hydrothermal liquefaction of sewage sludge

Hydrothermal liquefaction (HTL) of sewage sludge (SS) was performed in the presence of metallic Zn, Fe and Ni to investigate their effect on the performances of the process in terms of product yields and quality. Experiments were performed in subcritical water at 350 ◦C for 10 min using each metal individually and in the presence of homogenous hydrogen producers like formic acid (FA) and KOH. Interesting results were obtained with Zn that when used alone or in the presence of KOH, increased the cumulative biocrude (BC) yields and resulted in energy recoveries (ER) higher than 100% with respect to initial energy content of the biomass, thus indicating that HTL of SS is globally endothermic. …

Towards the simultaneous generation of electric energy and the abatement of organic pollutants by reverse electrodialysis processes

In reverse electrodialysis (RED) processes, electrical energy is directly extracted from chemical potential gradients arising from salinity differences, especially from sea and river water [1]. In RED there are at least four complementary elements: (1) electrodes, where electron transfer reactions occur to allow the transformation of the charge carrier from ion to electron; (2) ion selective exchange membranes, which allow the selective transport of ions; (3) solvents, which make a continuum for ion transport; (4) electrolytes, i.e. the current carriers between cathode and anode. The redox process is usually chosen in order to limit the energetic losses, the cost of redox specie and electro…

Optimization of selectivity for the electrocarboxylation of chloroacetonitrile

Electrocarboxylation of benzyl halides at silver cathodes

Anodic abatement of organic pollutants in water in micro reactors

The electrochemical oxidation of oxalic acid (OA) was performed in a micro flow cell equipped with a boron doped diamond (BDD) anode. This preliminary study demonstrates that a flow cell with a micrometric distance between the cathode and the anode can be used to perform the electrochemical treatment of waters contaminated by organic pollutants in the absence of added supporting electrolytes with high abatements. The effect of the distance between the cathode and the anode, the flow rate and the current density on the abatement of oxalic acid and on the current efficiency was in particular studied.

ELECTROCHEMICAL CONVERSION OF CARBON DIOXIDE TO FORMIC ACID IN A PRESSURIZZED FILTER PRESS CELL

To limit the negative effect of carbon dioxide as a greenhouse gas, an interesting approach is the utilization of Carbon Capture and Conversion (CCC) methodology, which is focused on the use of CO2 waste as a feedstock to produce added-value product by using the excess electric energy from renewable source [1]. In this framework, an increasing attention has been devoted in the electrochemical conversion of carbon dioxide to formic acid in water [2,3], which is considered one of the more attractive pathway to convert CO2. Since the main hurdle of the CO2 reduction from aqueous solution is the low CO2 solubility in water, in this work, the effect of some operating parameters, including pressu…

Energy generation and abatement of Acid Orange 7 in reverse electrodialysis cells using salinity gradients

Abstract The simultaneous generation of electric energy and the treatment of wastewaters contaminated by an organic pollutant resistant to conventional biological processes, Acid Orange 7 (AO7), was achieved for the first time using proper redox processes by reverse electrodialysis using salinity gradients. The stack was fed with two aqueous solutions with different concentrations of NaCl and a synthetic wastewater contaminated by AO7. Various electrochemical approaches including electro-Fenton, electrogeneration of active chlorine (IOAC) and coupled process were performed in a stack equipped with 40–60 cell pairs and studied by focused electrolyses. The effect of the number of cell pairs a…

Electrochemical Incineration of Dichloroethane. Influence of the anode material

Electrochemical Abatement of Organic Pollutants in Continuous-Reaction Systems through the Assembly of Microfluidic Cells in Series

The electrochemical treatment of wastewater contaminated by organic pollutants was performed under a continuous mode by using, for the first time, various micro-electrochemical cells in series. A synthetic solution of acid orange 7 (AO7), a largely used azoic dye, was chosen as model wastewater. Both the electro-Fenton (EF) method with a cheap compact graphite cathode and electrochemical oxidation (EO) at a boron-doped diamond (BDD) anode were used. EO gave higher abatement of total organic carbon (TOC), but drastically higher energetic consumptions than EF. It is worth mentioning that very different operating conditions were set for EF and EO to optimize their performances. The utilization…

Investigation of electrode material – Redox couple systems for reverse electrodialysis processes. Part I: Iron redox couples

Abstract The performances of electrodialysis (ED) and reverse electrodialysis (RED) processes depend on several factors, including the nature of the electrode material and of the redox couple adopted to make possible the conversion between electric power and chemical potential. In this paper, the possible utilization of iron-based redox couples (FeCl3/FeCl2, hexacyanoferrate(III)/hexacyanoferrate(II) and Fe(III)-EDTA/Fe(II)-EDTA) on graphite and DSA electrodes for RED processes was studied by a detailed experimental investigation. The hexacyanoferrate(III)/hexacyanoferrate(II) system was stable for long time (more than 12 days) in the absence of light and oxygen at high redox couple concent…

Hydrothermal liquefaction of microalgae in the presence of transition metal salts

Electrochemical incineration of organic pollutants: effect of the nature of the pollutants and of the operative conditions

Chimica supramolecolare della beta-ciclodestrina nell'anidride carbonica supercritica: studi spettroscopici

Interesterification of rapeseed oil catalysed by a low surface area tin (II) oxide heterogeneous catalyst

Abstract The interesterification of rapeseed oil was performed in a batch reactor using for the first time low surface area massive tin(II) oxide as heterogeneous catalyst and methyl acetate as acyl acceptor. The effect of reaction temperature, methyl acetate to oil molar ratio and catalyst loading on the performances of the process were investigated. Yields in fatty acid methyl esters (FAMEs) and triacetin (TA) up to 90% and 70% respectively, were achieved after 4 h of reaction time at 483 K in the presence of 0.69 mol of SnO per mole of rapeseed oil using a methyl acetate to oil molar ratio of 40. Quite interestingly, the catalyst performances improved when water was added to the reaction…

Effect of air pressure on the electro-generation of H2O2 and the abatement of organic pollutants in water by electro-Fenton process

Abstract The electro-generation of H 2 O 2 and the abatement of the model organic pollutant Acid Orange 7 (AO7) in water by an electro-Fenton process were performed under moderate air pressures (up to 11 bar) for the first time to our knowledge. An increase of the pressure gave rise to a drastic enhancement of the concentration of hydrogen peroxide. In systems pressurized with air at 11 bar, the electro reduction of oxygen at a graphite cathode gave rise to a concentration of H 2 O 2 of about 12 mM, about one order of magnitude higher than that achieved at atmospheric pressure. This result is attributed to the mass transfer intensification induced by the higher local concentration of molecu…

Catalytic hydrothermal liquefaction of municipal sludge assisted by formic acid for the production of next-generation fuels

Abstract Hydrothermal liquefaction (HTL) of municipal sludge (MS) was studied at 325 °C and 30 min at 10 and 30% w/w concentration of MS using formic acid (FA) as a green liquid hydrogen donor both in the absence and in the presence of heterogeneous catalysts. Pellets of commercial NiMo/Al2O3, CoMo/Al2O3 and felt of activated carbon ACF 1600 were used as catalysts. The addition of FA at high MS loading allowed to increase the yields in BC from 41 to 62% and its H/C ratio from 1.80 to 2.01 leading to energy recovery (ER) higher than 100%.When heterogeneous catalysts were used together with FA, a marked improvement of BC yields and quality was obtained at 10% MS loading. This behavior was not…

HOST-GUEST INCLUSION COMPLEXES BETWEEN PERACETYLATED B-CYCLODEXTRIN AND DIPHENYL(4-PHENYLPHENYL)PHOSPHINE IN SUPERCRITICAL CO2: COMPUTATIONAL STUDIES

Gamma radiation induced polymerization of vinyl monomers in dense CO2

Abstract The dispersion polymerization of methyl methacrylate in dense carbon dioxide, initiated by γ-rays, utilizing different polysiloxanes as polymeric stabilizers, was investigated. The progress of the reaction, as a function of the irradiation dose, was also studied and the occurrence of a gel effect has been detected. For comparison, the dispersion polymerization has been carried out in supercritical conditions ( T =65°C and 38 MPa) in the presence of 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. High molecular weight polymer (M w > 1000 kg/mol) with narrow molecular weight distribution has been obtained both with γ-rays and AIBN. The electron scanning micrographs show that regul…

Copolymerization of Vinylidene Fluoride and Acrylic Acid in Supercritical Carbon Dioxide

The free-radical copolymerization of vinylidene fluoride (VDF) and acrylic acid (AA) was carried out in supercritical carbon dioxide using both precipitation and dispersion techniques in the presence of an ammonium carboxylate perfluoropolyether compound. Formation of a copolymer was confirmed by variable contact time CP MAS NMR spectroscopy. Macromolecular matrices were significantly enriched in AA with respect to the initial feed composition and we found that the nonfluorinated monomer has a much higher reactivity ratio with respect to VDF. The cumulative concentration, crystallinity, and water affinity of the synthesized copolymers could be modified changing the initial feed composition,…

Effect of mode of operation, substrate and final electron acceptor on single-chamber membraneless microbial fuel cell operating with a mixed community

Abstract Waste minimization and circular thinking are to be achieved in order to cope with the limited amount of resources of our planet. In this perspective, bio-electrochemical systems (BESs) can contribute to the global balance with their ability to extract chemical residual energy from wastewater and transform it directly into electrical current. BESs development has been limited by the cost connected to reactor design, in which membranes and cathode catalyst constituted a major drawback. In this paper we report the optimization process of a simple reactor without membranes or precious catalyst that produced 47.1 mW m−2, which is more than what achieved with configurations including mem…

Influence of the methodology of inoculation in the performance of air-breathing microbial fuel cells

In this work, four air-breathing microbial fuel cells (AB-MFC) were operated for 1 month in order to determine if the methodology of inoculation affects the steady-state performance of this type of MFCs. For this purpose, anaerobic and aerobic sludge were fed to two identical AB-MFCs without any external carbon source into a tight sealed environment during the first three days of start-up. For comparison purposes, other two AB-MFCs were operated mixing the initial sludge and an amount of sodium acetate as substrate. Results point out that the inoculation procedure does not affect the steady-state treatment capacity of the cells but it affects very seriously the production of electricity. On…

A New Simple Static Method for the Determination of Solubilities of Condensed Compounds in Supercritical Fluids

Abstract A simple static method based on gravimetric measurements has been adopted to measure the solubility of benzenecarboxylic acid, 2-hydroxy-benzenecarboxylic acid, 4-hydroxy-benzenecarboxylic acid and 1,8-dihydroxyanthraquinone along several isotherms in the temperature range 318–357 K and the pressure interval 7–23 MPa. Solubility data have been correlated with the Zieger–Eckert approach, using the Fedor atomic and group contribution method to estimate the solubility parameter and the molar volume of the solutes. A good agreement was obtained between data reported in the literature and those determined using the proposed method which allows one to measure solubility mole fraction as …

Metodologie di fabbricazione di microreattori elettrochimici

A one-pot method to enhance dissolution rate of low solubility drug molecules using dispersion polymerization in supercritical carbon dioxide

The surfactant assisted polymerization of 1-vinyl-2-pyrrolidone in supercritical carbon dioxide in the presence of Piroxicam, selected as a model of a low aqueous solubility drug, was studied in order to prepare in a single step a polymeric composite to enhance the rate of dissolution of the pharmaceutical compound. Reactive entrapping was carried out at 65 degrees C in the P range 21-38MPa. Under proper operative conditions we obtained the composite under the form of sub-micron spherical particles with relatively narrow particle size distribution. Drug loadings higher than 12% (w/w) were obtained and XRD and Raman spectroscopy suggest that the anti-inflammatory agent is dispersed in the ma…

Thermally Regenerative Ammonia Batteries for Waste-Heat Exploitation

It is widely accepted that one of the most important issue to be faced by the scientific community is how to sustain the modern way of living and the related energy demand. While a long term target is the transition to a full-renewable energy system, a closer exigency is the optimization of the processes already existing. It has been calculated that about 370.41 TWh of potential energy is annually lost in Europe in the form of waste-heat from the industrial sector [1]. Waste heat comprises all the thermal energy with a temperature below 130 °C [2] (or 300 °C [1]), that hardly can find a useful application with the state of the art industrial technologies. Indeed, electrochemical technologie…

Ionizing radiation induced synthesis of polymers and blends with different structures

A Gas Chromatographic Method To Measure Sorption of Supercritical Carbon Dioxide in Poly(vinylidenefluoride): a Comparison between two Different Techniques.

Incineration of oxalic acid at boron doped diamonds. In: Giornate dell'elettrochimica italiana

Grafting of vinyl monomers on PVC and PVDF by ATRP

ATRP (atom transfer radical polymerization) has been recently used to prepare graft copolymers with regularly-spaced polymer chains from polymeric macroinitiators that have pendant chemical groups containing radically transferable halogen atoms [1]. The halogen atom serves as initiation site for the polymerization of side chains. ATRP employs the equilibrium between dormant alkyl halides and active propagating radicals to maintain a low concentration of active species. The activated radical species can either propagate or be deactivated to reform the dormant species. This process is catalyzed by a transition metal compound such as Cu-based species. The continuous development of more active …

Inclusion complexes of triphenylphosphine derivatives and peracetylated -beta- cyclodextrin in supercritical carbon dioxide.

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: Experimental Analysis of the Reaction Loci

Free radical copolymerization reactions of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) were carried out in supercritical carbon dioxide at T=50 °C. When ammonium carboxylate perfluoropolyether surfactants were used, the formation of polymer particles was observed provided that HFP mole fraction in the feed was not larger than 0.30. Under these conditions, the effect of the total interphase area of the polymer phase, Ap, on the product propertieswas investigated by comparing experiments with largely different amounts of stabilizer, i.e., ranging from precipitation (smaller Ap) to dispersion (larger Ap) polymerization systems. We found that the copolymer molecular weight distribut…

Supercritical-fluid extraction of chlorofluoroalkanes from rigid polyurethane foams

Abstract Preliminary results about a process for recovering expanding agents chlorofluoroalkanes (CFCs) both trapped in the cavities and dissolved in the polymer from rigid polyurethane foams are reported. The performances of liquid and supercritical carbon dioxide, and of CO2-propane supercritical mixtures were compared. Better results in terms of extraction time and amount of extracted CFCs were obtained with finely ground materials and supercritical propane-carbon dioxide fluids.

Pressurized CO2 Electrochemical Conversion to Formic Acid: From Theoretical Model to Experimental Results

To curb the severely rising levels of carbon dioxide in the atmosphere, new approaches to capture and utilize this greenhouse gas are currently being investigated. In the last few years, many researches have focused on the electrochemical conversion of CO2 to added-value products in aqueous electrolyte solutions. In this backdrop, the pressurized electroreduction of CO2 can be assumed an up-and-coming alternative process for the production of valuable organic chemicals [1-3]. In this work, the process was studied in an undivided cell with tin cathode in order to produce formic acid and develop a theoretical model, predicting the effect of several operative parameters. The model is based on …

Electrochemical Processe s and Apparatuses for the Abatement of Acid Orange 7 in Water

We have studied the electrochemical treatment of aqu eous solutions contaminated by Acid Orange 7 (AO7) by electro-Fenton process (EF). The main object ive was to evaluate how the electrochemical route affects the performances of the d egradation process. EF process was carried out in a number of very different reactors: conventional bench scale electrochem ical cell, microfluidic electrochemical reactor, microbial fuel cell and stack for reverse electrodialysis processes. The utilisation of micro devices allowed to work without the addition of a supporting elec trolyte and improved the performances of EF. Microbial fuel cell did not need the supply of electric energy bu t our device requir…

Advances and Perspectives of Supercritical Fluid Technology

1 Dipartimento di Ingegneria Industriale, Universita di Salerno, Salerno, 84084 Fisciano, Italy 2 Departamento de Ingenieŕia Quimica, Universidad de Castilla-La Mancha, 13004 Ciudad Real, Spain 3 Department of Agricultural, Food & Nutritional Sciences, University of Alberta, Edmonton, AB, Canada T6G 2P5 4Dipartimento di Ingegneria Chimica, Gestionale, Informatica, Meccanica, Universita di Palermo, 90128 Palermo, Italy

Electrocatalytic carboxylation of chloroacetonitrile at a silver cathode for the synthesis of cyanoacetic acid

Abstract The electrocatalytic carboxylation of chloroacetonitrile to cyanoacetic acid performed at silver cathodes was investigated both theoretically and experimentally. Silver exhibits powerful electrocatalytic activities towards the reduction of chloroacetonitrile. In CO 2 -saturated CH 3 CN, reduction of NCCH 2 Cl occurs at potentials that are about 0.7 V more positive than those observed at glassy carbon and gives cyanoacetic acid in good yields. Theoretical considerations on the effect of operative parameters on the performances of the process were confirmed by electrocarboxylation experiments performed in undivided cells equipped with sacrificial anodes both in a bench-scale electroc…

Polymerization of vinylidene fluoride with perfluoropolyether surfactants in supercritical carbon dioxide as a dispersing medium

The heterogeneous polymerization of vinylidene fluoride (VDF) was investigated at 50 °C with supercritical carbon dioxide (scCO 2 ) as a dispersing medium and diethylperoxidicarbonate as an initiator in the presence of different perfluoropolyether surfactants. When FLK 7004A ammonium carboxylate salts were used at a 5% (w/w) concentration with respect to VDF, with an initial pressure of 31-45 MPa and with an olefin concentration of about 5.5 mol/L, monomer conversions up to 63% were obtained, corresponding to a final solid content higher than 200 g/L, and the polymer was collected at the end of the process in the form of a white powder completely composed of microspheres. The effects of the…

Electrochemical Treatment of Synthetic Wastewaters Contaminated by Organic Pollutants at Ti 4 O 7 Anode. Study of the Role of Operative Parameters by Experimental Results and Theoretical Modelling

In the last years, an increasing attention has been devoted to the utilization of anodic oxidation (AO) technologies for the treatment of wastewater polluted by recalcitrant organics. Recently, Ti4O7 was proposed as a promising anode for AO for the treatment of various organics. Here the potential utilization of commercial Ti4O7 anodes has been evaluated considering the electrochemical treatment of synthetic wastewater contaminated by three very different organic molecules (namely, oxalic acid, phenol and Acid Orange 7), all characterized by a very high resistance to AO. The performances of Ti4O7 were compared with that of two largely investigated anodes: Boron-doped diamond (BDD), which is…

Dispersion Polymerization of Vinylidene Fluoride in Supercritical Carbon Dioxide

The dispersion polymerization of vinylidene fluoride in supercritical carbon dioxide is investigated using two ammonium carboxylate perfluoropolyether stabilizers of different molecular weights. Under suitable operating conditions a polymer made of well-dispersed spherical particles has been obtained up to relatively high conversion. The experimental data of polymerization rate and molecular weight distribution are in good agreement with the predictions of a model previously developed. Such an agreement supports the conclusion that the polymerization kinetics is dominated by the interphase transport of the active radicals between the continuous phase and the polymer particles.

Grafting of Maleic Anhydride onto Isotactic Polypropylene in the Presence of Supercritical Carbon Dioxide as a Solvent and Swelling Fluid

Grafting of maleic anhydride (MA) onto isotactic polypropylene (iPP) was carried out by thermal decomposition of dicumylperoxide (DCP) using supercritical carbon dioxide (scCO2) as a solvent and swelling fluid. Provided that the initial concentration of anhydride dissolved in scCO2 is higher than 1% w/w, the grafting occurs without significant molecular weight modification of the polymer, and with a proper selection of the operative conditions, a grafting level higher than 0.5% w/w with respect to the polymer mass was obtained. The amount of grafted MA was determined by FT-IR spectroscopy and polymer degradation was monitored by dynamic mechanical tests in the melt state. The effect of MA a…

Electrochemical oxidation of organics at metal oxide electrodes: The incineration of oxalic acid at IrO2-Ta2O5 (DSA-O2) anode

Abstract The electrochemical incineration of oxalic acid (OA) at Ti/IrO2–Ta2O5 (DSA-O2) anode was investigated to find the influence of the operative parameters on the performances of the process. Polarization curves and chronoamperometric measurements indicate the probable occurrence of a direct electrochemical oxidation of OA at the surface of the DSA anode. In incineration electrolyses, the performances of the process in terms of OA conversion and current efficiency dramatically depend on the adopted operative conditions. Interestingly, very high OA removal and current efficiency were obtained when the process was performed at relatively high temperatures (50 °C) or in the presence of Na…

Liquid hot water pretreatment of Arundo Donax: a comparison between batch and a flow-through systems

Two electrochemical methodologies for the synthesis of cyanoacetic acid

Electrochemical incineraton of oxalic acid at boron doped diamond electrodes: influence of operative parameters

The influence of aluminium cations on electrocarboxylation processes in undivided cells with Al sacrificial anodes

Abstract The influence of Al cations on the electrochemical carboxylation of acenaphthylene ( 1 ), benzophenone ( 2 ), 6-methoxy-2-acetonaphthone ( 3 ), and benzyl chloride ( 4 ) has been investigated in dimethylformamide at a glassy carbon cathode. The Al 3+ ions were either added at the beginning of the experiment or were released from the anode during electrocarboxylation. It has been found that when Al cations are added to the reaction medium, they strongly influence the reduction process, in most cases leading to a complete change of the mechanism. For example, in the case of 1 , the radical anion ( 1 − ) formed upon 1e − reduction rapidly reacts with Al 3+ to give an Al(III) adduct, w…

Electrochemical conversion of CO2 to HCOOH at tin cathode in a pressurized undivided filter-press cell

Abstract The electrochemical reduction of carbon dioxide to formic acid was performed for the first time in a pressurized filter-press cell with a continuous recirculation of the electrolytic solution (0.9 L) at a tin cathode. It was shown that the performances of the system are comparable or slightly better than that of a batch system with a smaller volume (0.05 L). The selection of proper values of both current density and CO2 pressure allowed to achieve quite high values of faradaic efficiencies. Long-time electrolyses have shown that the system is stable and that it can allow to generate quite high concentrations of HCOOH (about 0.4 M).

Continuous dispersion Polymerization of methyl methacrylate in scCO2

Complexation of phosphine ligands with peracetylated β-cyclodextrin in supercritical carbon dioxide: Effect of temperature and cosolvent on the equilibrium constant

Abstract The interaction between peracetylated-β-cyclodextrin and tert-butyl and adamantyl functionalized triphenylphosphine derivatives was studied in supercritical carbon dioxide (scCO 2 ) based solvent media by UV–vis spectroscopy. The equilibrium constant for a 1:1 complexation reaction was obtained from titration spectra both in pure carbon dioxide and in the presence of methanol as a cosolvent in the temperature range 308–323 K to estimate the internal energy and entropy of the inclusion equilibrium. The values of the equilibrium constants were found significantly smaller than those obtained in aqueous solution with analogous phosphines and substantially independent of the nature of t…

Biorefinery process for hydrothermal liquefaction of microalgae powered by a concentrating solar plant: A conceptual study

Abstract A conceptual analysis of coupling a concentrating solar power plant with a biorefinery process consisting in the hydrothermal liquefaction (HTL) of microalgae to biocrude was performed. The configuration of the CSP-HTL plant was designed to allow continuous operation considering 10 kT of microalgae processed each year using, for the first time, a ternary nitrate mixture as heat transfer fluid and storage medium in the temperature range of 340–410 °C. With adopted models, the capital and operating costs of the solar plant marginally affect the minimum fuel selling prize (MFSP) of biocrude that decreases with the size of the solar field and of the thermal storage system provided that…

Dispersion polymerization of methyl methacrylate in supercritical carbon dioxide stabilized with poly(ethylene glycol)-b-perfluoroalkyl compounds

Abstract In this work selected components of an easily synthesible class of poly(ethylene glycol)-perfluoroalkyl block compounds were tested as stabilizers for the dispersion polymerization of methyl methacrylate in scCO 2 . As already observed in the case of different block surfactants the anchor soluble balance (ASB) of the stabilizer is the crucial parameter affecting the efficacy of the stabilization and the kinetics of the polymerization process. When stabilizers with appropriate ASB were used, high molecular weight poly(methyl methacrylate) was synthesized under the form of microspherical polymer particles with yields ranging up to 80%. In these experiments the occurrence of a gel-eff…

Polymer Synthesis in Supercritical Carbon Dioxide

It is current opinion of most of the people involved in supercritical fluids (SCFs) technology that as the end of the twentieth century has been devoted to enlarge exploitation of compressed gases in separation processes the beginning of the twenty-first will be mainly aimed to improve their utilisation as solvents for reactions.

Integrated production of fresh water, sea salt and magnesium from sea water

Seawater desalination is becoming an important source of fresh water in several countries all around the world. One of the main drawbacks of desalination processes, however, is related to the disposal of large quantities of concentrated brine, which is an always-present by-product of the process. An integrated production of fresh water and salts may be achieved using the discharge brine from a desalination plant as a feed for conventional salt ponds, with the advantages of using brine more concentrated than sea water and, in the case of thermal desalination plants, warmer than sea water. By doing so, the process is faster as a consequence of the enhancement of evaporation rate on the surfac…

Hydrothermal liquefaction of sewage sludge: towards the effects of transition metals in the presence of homogeneous hydrogen producers

Waste carbonaceous matrices, such as sewage sludge (SS) seem to have a great potential, because they are namely costless matrices compared to the microalgae and hydrothermal liquefaction (HTL) can be considered an interesting route to dispose and valorize them [1-5]. However, SS are characterized by high amount of non-biogenic fractions, such as plastics, salts and metals. In particular SS contains a high amount of inorganics [5], such as Al, Ba, Ca, Cr, Cu, Fe, Ni, K, Mg, Mn, Na, P, S, Ti, Zn, Si which are distributed in the products at the end of the reaction. The presence of heavy metals represent a big challenge for the implementation of HTL on the industrial scale as they can affect pr…

Hydrothermal co-liquefaction of sewage sludge and formic acid

The biocrude produced by non-catalytic hydrothermal liquefaction (HTL) has a too high heteroatom content to be used directly as a fuel [1-3]. Several studies found that different H2 initial pressures during HTL experiments were ineffective in improving the biocrude yield [4-6], nevertheless it was observed that higher initial pressures of H2 brought an improvement of the concentration of light compounds in the biocrude, decreasing the average molecular weight of biocrude oil. To date H2 is mainly generated from fossil sources and realization of a possible hydrogen economy from alternative sources presents many challenges. The use of a liquid hydrogen storage media could represent for the HT…

Oxidation of carboxylic acids in water at IrO2-Ta2O5 and Boron Doped Diamond anodes

Abstract A detailed study was dedicated to the anodic oxidation of three carboxylic acids (namely, oxalic, formic and maleic acid) with the objective to evaluate in a systematic way the effect on the oxidation of carboxylic acids of numerous relevant parameters, including the nature and the concentration of the carboxylic acid, the alimentation regime (potentiostatic vs. amperostatic), the current density and the working potential values, the flowdynamic regime, the temperature and the nature of the electrode material. It was observed that the effect of some operative parameters strongly depends on the nature of the electrode and of the carboxylic acid. As an example, the efficacy of abatem…

Experimental P-T-ro Measurements of Supercritical Mixtures of Carbon Dioxide, Carbon Monoxide, and Hydrogen and Semiquantitative Estimation of Their Solvent Power Using the Solubility Parameter Concept

The P-T-ρ behavior of the CO2-CO-H2 system was studied in the supercritical region under operative conditions close to those adopted to perform hydrogenation and hydroformylation reactions in dense CO 2, thus providing new interesting information on this fluid mixture. Experiments were performed in a fixed volume reactor in the temperature range from 298 K to 343 K changing the density and the composition of the fluid phase. The one-component (Hildebrand) solubility parameter of the mixture was estimated from experimentally measured P vs T profiles, and its dependence on the density and composition of the system was analyzed to study the antisolvent effect of the permanent gases. We have fo…

The Use of t-Bu Functionalized Phosphine Ligands for Hydroformylation of High Molecular Weight Olefins in scCO2

Electrochemical incineration of 1,2-dichloroethane: Effect of the electrode material

The electrochemical incineration of 1,2-dichloroethane (EDC) at Pt, Au, boron-doped diamond (BDD), Ebonex, stainless steel, Ti/IrO2–Ta2O5 and PbO2 has been studied in acid media by cyclic voltammetry and bulk electrolysis. It has been shown that the performances of the process dramatically depend on the anodic material. Higher current efficiencies were obtained at BDD. In particular, at proper values of applied current density, it is possible to obtain the almost complete conversion of EDC to CO2 at BDD with current efficiencies higher than 40%.

Sterilization of macroscopic poly(l-lactic acid) porous scaffolds withdense carbon dioxide: Investigation of the spatial penetration of thetreatment and of its effect on the properties of the matrix

Abstract In this work the sterilization with dense carbon dioxide of poly( l -lactic acid) (PLLA) porous scaffolds intended for tissue engineering applications was investigated with the main objective of confirming the three-dimensional efficacy of the treatment and of analysing the scaffold properties after CO2 treatment. For this purpose the scaffold was contaminated with a conventional bacterium (Escherichia coli) and with spores (Streptomyces coelicolor), a species more fascinating and difficult to inactivate. Contamination was performed in such a way to soak the whole matrix with bacteria and spores. The effect of pressure and treatment time on the efficacy of the sterilization was eva…

Abatement of Acid Orange 7 in macro and micro reactors. Effect of the electrocatalytic route

Abstract The electrochemical treatment of aqueous solutions contaminated by Acid Orange 7 (AO7) was widely studied with the main objective to evaluate as the electrocatalytic route affects the performances of the degradation process in macro and microfluidic cells. Direct anodic oxidation (EO), electro-Fenton (EF), electro-generation of active chlorine (IOAC) and coupled processes were investigated in macro and microfluidic reactors in order to select more effective conditions for the treatment of such compound. The effect of numerous operative parameters (such as nature of the electrode materials, coupling of processes, flow rate, current density and inter-electrode distance) on the perfor…

Electrochemical treatment of paper mill wastewater by electro-Fenton process

Abstract The electrochemical oxidation of organics in paper mill wastewater belonging to Halfa industries (Tunisia) was performed by galvanostatic electrolyses using electro-Fenton (EF) process. The effect of several operating parameters, such as applied current density, electrodes material, air pressure and the presence of sodium chloride (NaCl) was evaluated. In particular, carbon felt (CF), modified carbon felt (MCF) and gas diffusion electrode (GDE) were used as cathode while Ti/IrO2-Ta2O5 and Boron Doped Diamond (BDD) as anode. Total Organic Carbon (TOC) measure was chosen as reference parameter to assess the extent of the treatment. The experimental results show that, by adopting the …

High-pressure synthesis of CO and syngas from CO2 reduction using Ni-N-doped porous carbon electrocatalyst

Abstract Electrochemical conversion of CO2 to CO or syngas (CO/H2 mixture) is considered one of the most promising approaches to valorise waste-CO2. To develop the process on industrial scale, it would be necessary to use selective and inexpensive electrodes and to obtain high productivities with low energy consumption. In this frame, Ni−NC catalysts are considered among the most interesting ones because of their relatively low cost, high faradaic efficiency in CO ( F E C O ), and high stability. However, up to now, quite low productivities were obtained as a result of low current densities achieved in aqueous electrolytes. In this work, we have evaluated the performances of a Ni−NC electro…

Heterogeneous polymerization of 1-vinyl-2-pyrrolidone in scCO2 in the presence of Ibuprofen: a one pot process for the preparation of controlled release systems

Investigation of Multicomponent Gas Sorption in Polymers: the Case of the Carbon Dioxide, Vinylidene Fluoride, PVDF System.

Mass swelling of PVDF exposed to supercritical carbon dioxide

Electrocarboxylation of chloroacetonitrile to cyanoacetic acid

Transesterification of rapeseed oil over acid resins promoted by supercritical carbon dioxide

The methanolysis of rapeseed oil catalyzed by commercial styrene-divinylbenzene macroporous acid resins was performed in a batch reactor at 100-140 °C and 10-46 MPa to study the effect of supercritical carbon dioxide (scCO2) on the performances of the process. Reaction temperatures of 120-140 °C were necessary to obtain high enough yields of fatty acid methyl esters. Upon addition of scCO2 faster transesterification kinetics was obtained also at the lowest investigated operating pressure (10-11 MPa), working in two fluid phase systems. Experiments performed changing the reaction time indicated that most of the esters were formed during the first 3 h. When the pressure was increased at 38-46…

Electroreduction of aliphatic chlorides at silver cathodes in water

The effect of water on the reduction of aliphatic chlorides at silver cathodes was investigated by cyclovoltammetric experiments in acetonitrile, water and their mixture and focused electrolyses in water solutions. The addition of water to acetonitrile gives rise to the formation of new peaks and/or the displacement of pre-existent peaks at dramatically less negative potentials. In a water medium, silver shows a very large electrocatalytic effect towards the reduction of chlorinated aliphatic compounds belonging to the classes of chloromethanes, chloroethanes and chloroethenes, dramatically higher than that observed in aprotic solvents such as dimethylformamide (DMF) or acetonitrile (ACN). …

Electrochemical Conversion of CO2 to HCOOH at Tin Cathode: Development of a Theoretical Model and Comparison with Experimental Results

The electrochemical reduction of pressurized carbon dioxide at tin cathode is considered a very promising process for the production of formic acid. Here, the process was studied in an undivided cell with the aim of developing a simple theoretical model. First, a large series of polarization and electrolyses was performed in order to evaluate the kinetic of the process. According to the literature, experimental results can be described by a simple reaction mechanism, which involves the following key stages: (i) mass transfer of CO2 to the cathode; (i) its adsorption described by a Langmuir equation; (iii) the reduction of adsorbed CO2. A simple model was developed based on the cathodic conv…

Utilization of Poly(vinylchloride) and Poly(vinylidenefluoride) as Macroinitiators for ATRP Polymerization of Hydroxyethylmethacrylate. Electroanalytical and Graft-Copolymerization Studies

The utilization of poly(vinylchloride) (PVC) and poly(vinylidenefluoride) (PVDF) as macroinitiators for atom transfer radical polymerization (ATRP) of hydroxyethylmethacrylate (HEMA) was studied performing electroanalytical investigations and “grafting from” experiments in order to achieve information on the possibility of modifying such commercial polymers by this controlled free radical polymerization technique. This study was performed changing various operating parameters such as the nature of the copper salt, the ligand, the solvent, the temperature and the reaction time. Electroanalytical data suggest that PVC can be easily activated by both CuCl/ Tris(2-pyridylmethyl)amine (TPMA) and…

Incenerimento elettrochimico di acido ossalico in presenza di NaCl

Electrochemical treatment of real wastewater with low conductivity

In the last years, many efforts have been devoted to the development of electrochemical processes for the effective treatment of wastewater contaminated by organic pollutants resistant to conventional biological processes and/or toxic for microorganisms [1–5]. It was shown that some electrochemical approaches, including the direct anodic oxidation at suitable anodes such as boron-doped diamond (BDD) and/or electro-Fenton (EF) at suitable operating conditions and cells [1–6] could allow treating effectively a very large number of organic pollutants. However, most of the investigations were performed using synthetic wastewater. Hence, it is now mandatory to study the problems connected to the…

Modeling Heterogeneous copolymerization of fluorinated monomers in scCO2

In recent years the use of supercritical carbon dioxide (scCO2) in polymer processing and reaction has emerged as a “green” alternative to replace both environmentally hazardous organic solvents and water, whose utilization involves the production of large amount of waste streams. Moreover, scCO2 is non-toxic, inexpensive, and often exhibits intense plasticizing effect on polymers. In this work, the copolymerization of fluorinated monomers in scCO2 is explored. Batch free-radical copolymerization reactions of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) have been carried out at temperature of 50 C and pressure of 400 bar using DEPDC as initiator and different amounts of stabilize…

Influence of operative parameters on the electrochemical incineration of oxalic acid.

Sterilization of three-dimensional tissue engineering scaffolds by supercritical carbon dioxide

Medical devices, implants or patient-care equipment that will come into intimate contact with a patient must be effectively decontaminated to prevent infection or disease transmission. Non-sterile devices have significant ramifications for patient morbidity and mortality and two processes must be undertaken in order to make an item acceptable for use or implantation: cleaning and disinfection (or sterilization) [1]. Sterilization is the destruction of living organisms, and must be done without damaging the material surface and without compromising the bulk material strength or biocompatibility of implantable device. Common sterilization processes include steam autoclaving, gamma irradiation…

The rate of polymerization in two loci reaction systems: VDF-HFP precipitation copolymerization in supercritical carbon dioxide

When the copolymerization of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) is carried out in supercritical carbon dioxide (scCO 2) under heterogeneous conditions, the reaction occurs both in the continuous CO 2-rich phase and in the dispersed polymer-rich phase. The two phases being characterized by different values of reactant concentrations and kinetic parameters, one would expect that the reaction kinetics is affected by the polymer phase holdup in the reactor. However, the reaction rate is almost insensitive to the amount of produced polymer, at least at specific reaction conditions. This apparent contradiction is discussed and clarified in this paper by a series of comparativ…

SELECTION OF REDOX SYSTEMS FOR REVERSE ELECTRODIALYSIS PROCESSES

In reverse electrodialysis (RED) processes, electrical energy is directly extracted from chemical potential gradients arising from salinity differences, especially from sea and river water. In RED there are at least four complementary elements: (1) electrodes, where electron transfer reactions occur to allow the transformation of the charge carrier from ion to electron; (2) ion selective exchange membranes, which allow the selective transport of ions; (3) solvents, which make a continuum for ion transport; (4) electrolytes, i.e. the current carriers between cathode and anode. Studies on RED processes were mainly focused on membranes but also on several other aspects including electrolyte co…

Electrochemical incineration in a micro flow reactor: influence of operative parameters

Electrochemical processes for the treatment of chlorinated ethanes in water solutions

In the present work, the electrochemical treatment of water solutions containing chloro ethanes was performed by cathodic reduction, anodic oxidation and coupled processes with the aim of evaluate the effectiveness of these methodologies.

ELECTROCHEMICAL CONVERSION OF DICHLOROACETIC ACID TO CHLOROACETIC ACID IN A MICROFLUIDIC STACK AND IN A SERIES OF MICROFLUIDIC REACTORS

The electrochemical conversion of dichloroacetic acid to chloracetic acid was performed in three different micro devices: a simple micro fluidic cell; a microfluidic stack equipped with various electrode chambers in series and three micro fluidic cells in series. The electrochemical synthesis of chloracetic acid was performed successfully with high yields and selectivity under a single-pass mode without supporting electrolyte at low cell voltages. An increase of the productivity and of the final concentration of the target product was achieved by using a stack with two or three electrode chambers in series. The utilization of three micro reactors in series open interesting new perspectives,…

INFLUENCE OF THE EXPERIMENTAL SYSTEM AND OPTIMIZATION OF THE SELECTIVITY FOR THE ELECTROCARBOXYLATION OF CHLOROACETONITRILE TO CYANOACETIC ACID

The electrocarboxylation of chloroacetonitrile (ClACN) to cyanoacetic acid in undivided cells equipped with sacrificial anodes was investigated both in a bench-scale electrochemical batch reactor and in a continuous batch recirculation reaction system equipped with a parallel-plate electrochemical cell. Selectivity and faradaic yields higher than 90% were obtained by working under anhydrous conditions with low halide concentrations and at more negative potentials. It was found that the instantaneous selectivity in the carboxylate compound depends mainly on the [CO 2 ]/[ClACN] ratio at high substrate concentration and is close to 100% for low ClACN concentration. These results were consisten…

Electrochemical oxidation of organics in water: Role of operative parameters in the absence and in the presence of NaCl

The electrochemical oxidation of organics in water was investigated theoretically and experimentally to determine the role of several operative parameters on the performances of the process in the presence and in the absence of sodium chloride. Theoretical considerations were used to design the experimental investigation and were confirmed by the results of the electrochemical oxidation of oxalic acid (OA) at boron doped diamond (BDD) or IrO(2)-Ta(2)O(5) (DSA-O(2)) anodes in a continuous batch recirculation reaction system equipped with a parallel plate undivided electrochemical cell. Polarization curves and chronoamperometric measurements indicated that, in the presence of chlorides, the a…

A Novel Gas Chromatographic Method to Measure Sorption of Dense Gases into Polymers

A novel experimental approach to determine the solubility of gaseous compounds inside polymers is here described. The method is based on the gas chromatographic determination of the composition of the fluid phase at equilibrium with the polymer. To take into account the effect of the volume swelling on the measurement a suitable probe, nonabsorbable by the polymer, was added to the fluid phase. Under the adopted configuration the apparatus can operate up to 35 MPa and 80°C. This experimental technique has been used to determine the solubility of carbon dioxide in poly(vinylidene fluoride) using argon as a probe. The latter was chosen because it is negligibly absorbed by the polymer and does…

Midinfrared FT-IR as a Tool for Monitoring Herbaceous Biomass Composition and Its Conversion to Furfural

A semiquantitative analysis by means of midinfrared FT-IR spectroscopy was tuned for the simultaneous determination of cellulose, hemicellulose, and lignin in industrial crops such as giant reed (Arundo donaxL.) and switchgrass (Panicum virgatumL.). Ternary mixtures of pure cellulose, hemicellulose, and lignin were prepared and a direct correlation area/concentration was achieved for cellulose and lignin, whereas indirect correlations were found for hemicellulose quantification. Good correspondences between the values derived from our model and those reported in the literature or obtained according to the official Van Soest method were ascertained. Average contents of 40–45% of cellulose, 2…

Ring opening polymerization of $\varepsilon$-caprolactone in the presence of wet $\beta$-cyclodextrin: Effect of the operative pressure and of water molecules in the $\beta$-cyclodextrin cavity

International audience; The ring opening polymerization (ROP) of $\varepsilon$-caprolactone (CL) in the presence of $\beta$-cyclodextrin ($\beta$-CD) wasperformed in batch reactors both at room pressure and with the reaction system pressurized with CO$_2$, N$_2$ orAr. Significant enhancements of the polymerization rate was observed when the ROP was carried out withwet $\beta$-CD under pressure. For example, after 24 hours at 120° C with a $\beta$-CD/CL molar ratio of about1/100, the monomer conversion increased from 4 to 98–99% when the pressure was changed from 0.1to 12.5–13.0 MPa independent of the nature of the compressing gas. MALDI-TOF analyses indicated thata major fraction of polymer…

Crosslinking of polymers activated by electrogenerated hydroxyl radicals.

Nanogels (NGs) are systems created by crosslinking of polymers taking nanosized dimensions and they have been proposed for biomedical and pharmaceutical applications due to their soft consistency, biocompatibility and good chemical properties that make them excellent drug delivery agents (1). Differently from typical hydrogels, nanogels are able to dissolve in solvents and to swell releasing the drug molecules loaded in the nano-vector. Furthermore, if properly functionalized with reactive groups, these materials can represent a very interestingly vector for different pharmacological treatments (2). Several methods have been investigated to prepare polymeric nanogels starting from preformed…

Mechanism of the palladium-catalysed electrosynthesis of diethyl carbonate from carbon monoxide and ethanol

Abstract A mechanism is proposed for the PdBr2(PPh3)2-catalysed electrosynthesis of diethyl carbonate from carbon monoxide and ethanol, proceeding at room temperature and atmospheric CO pressure. The mechanism is investigated by cyclic voltammetry and 31P NMR spectroscopy. The active Pd0 complex able to coordinate CO is generated by the chemical reduction of PdBr2(PPh3)2 by EtO– ions generated from EtOH at the cathode. After reaction of EtO– ions with Pd0(PPh3)2(CO), the ensuing anionic complex [(PPh3)2Pd0–COOEt]– is oxidized at the anode in a key step leading to BrPdII–COOEt(PPh3)2. A nucleophilic attack of ethoxide on the latter generates diethyl carbonate and the Pd0 complex active in th…

ELECTROCHEMICAL MICROREACTORS FOR SYNTHESIS OF CHEMICALS AND ABATEMENT OF ORGANIC POLLUTTANTS

Electrochemical methods can offer new sustainable routes for both the synthesis of chemicals and the abatement of organic pollutants resistant to biological processes. These methods use a clean reagent, the electron, and very mild operative conditions (ambient temperature and atmospheric pressure) with limited operative costs. However, electrochemical processes present some important disadvantages when performed in conventional reactors. In particular, to achieve reasonable cell voltages when the medium has not an adequate conductivity, one needs adding to the system a supporting electrolyte. This is certainly a main obstacle for a wide application of electrochemical tools. Indeed, adding c…

Electrochemical Treatment of Wastewater by ElectroFenton, Photo-ElectroFenton, Pressurized- ElectroFenton and Pressurized Photo ElectroFenton: A First Comparison of these Innovative Routes

In the last few years increasing attention has been devoted to the utilization of electroFenton (EF) and EF based technologies for the treatment of wastewater polluted by recalcitrant organics. It has been shown that the performances of EF can be strongly improved using ultraviolet (UV) irradiation, e.g., by the photo-electroFenton (PEF) method, or pressurized air or oxygen, e.g., by the pressurized-electroFenton (PrEF) one. Although several studies were carried out on the degradation of many organic pollutants using EF, PEF or PrEF, a systematic comparison between PEF and PrEF was never reported as well as the possibility to couple the irradiation with pressurized air. In this study the pe…

Electrochemical oxidation of tetramethoxy precursor as a key step for the synthesis of coenzyme Q10

The feasibility of electrosynthesis of coenzyme Q10 (1) by electrooxidation of tetramethoxy precursor (2) has been investigated at carbon, Pt and BDD anodes in a divided cell. The process strongly depends on the applied potential, anode material and water content of the solvent. At carbon anodes in CH3CN/CH2Cl2 + 0.15 M Bu4NBF4 at proper operative conditions high faradic efficiency (>60%) and excellent selectivity (95–97%) of the target product were obtained. Keywords: Electrosynthesis, Coenzyme Q10, Anodic oxidation

Free radical copolymerization of vinylidene fluoride and acrylic acid in supercritical carbon dioxide

Electroactivation of Transition Metal Redox Couples for the Carbonylation of Alcohols to Dialkylcarbonates

Electrochemical systems which promote the carbonylation of methanol to dimethylcarbonate, based on the anodic activation of transition metal redox couples, or the Br−/Br2 couple, are poorly active for the carbonylation of ethanol to diethylcarbonate at room temperature and atmospheric pressure. Positive results have been obtained by combined addiction of PdBr2 and Bu4NBr to the system. In this way yields up to 50% in diethylcarbonate were obtained, with very good conductivities in long range electrolyses.

Conceptual study of the coupling of a biorefinery process for hydrothermal liquefaction of microalgae with a concentrating solar power plant

A conceptual analysis of the coupling of a concentrating solar power plant with a chemical process for hydrothermal liquefaction (HTL) of microalgae to biocrude was performed. The two plants were considered coupled by molten salt recirculation that granted energetic supply to the chemical process. Preliminary estimations have been done considering a solar field constituted by 3 linear parabolic solar collectors rows, each 200 m long, using a ternary molten salts mixture as heat transfer fluid, and a chemical plant sized to process 10 kT/y of microalgae. Under adopted conditions, we have estimated a minimum selling prize of the biocrude that is similar to that achieved in non-solar HTL proce…

Removal of Phenol from Water in the Presence of NaCl in Undivided Cells Equipped with Carbon Felt or Ni Cathodes: Effect of Air Pressure

Recently, the electrochemical treatment of wastewater polluted by recalcitrant organics and containing chlorides was shown to be significantly improved adopting proper operative conditions such as suitable anodes and cathodes and low current density. In particular, the use of suitable cathodes such as carbon felt or silver could increase the removal of TOC and reduce the formation of chlorinated by-products. In this study, attention was focused on the utilization of carbon felt cathodes with the main aim to evaluate the effect of air pressure on the process using phenol as model organic pollutant. It was shown that, in the presence of carbon felt cathode, the use of pressurized air allows b…

Interesterification of triglycerides with methyl acetate for biodiesel production using a cyclodextrin-derived SnO@γ-Al2O3 composite as heterogeneous catalyst

International audience; Particle morphology and surface properties of metal oxides are topics of great importance in the field of heterogeneous catalysis. Herein, we have developed a molecular-colloidal coassembly approach combined with an ultrasonic-assisted precipitation method to fabricate SnO@γ-Al2O3 composites with tuneable pore size and well-defined octahedral-shape crystal structure. The supramolecular assemblies formed between the randomly methylated β-cyclodextrin (RaMeβCD) and Pluronic F127 were employed as template to tailor the size and shape of γ-Al2O3 nanoparticles and direct their assembly almost exclusively on the surface of micrometer-sized SnO single …

A continuous reaction system to investigate dispersion polymerization of vinyl monomers in supercritical carbon dioxide

A laboratory-scale continuous reaction system using a stirred tank reac- tor was assembled in our laboratory to study the dispersion polymerization of vinyl monomers in supercritical carbon dioxide (scCO2). The apparatus was equipped with a suitable downstream separation section to collect solid particles entrained in the effluent stream from the reactor, whose monomer concentration could be measured online with a gas chromatograph. The dispersion polymerization of methyl methacry- late in scCO2 was selected as a model process to be investigated in the apparatus. The experiments were performed at 65 8C and 25 MPa with 2,2 0 -azobisisobutyroni- trile as the initiator and a reactive polysilox…

Assisted reverse electrodialysis for CO2 electrochemical conversion and treatment of wastewater: A new approach towards more eco-friendly processes using salinity gradients

Abstract In this paper, the utilization of assisted reverse electrodialysis (A-RED), recently used for pre-desalination, is proposed as a general method to reduce the energy requirements of electrolysis processes and evaluated for two model processes: (i) the cathodic conversion of carbon dioxide to formic acid; (ii) the anodic treatment of water contaminated by organics. In A-RED, two solutions with different salt content and an external potential difference, applied in the direction of the natural salinity gradient, are both used to drive redox processes. It was shown, for the first time, that the cathodic conversion of CO2 to formic acid can be performed by both reverse electrodialysis (…

A Novel Gas Chromatographic Method to Measure Solubility of Volatile Compounds in Polymers

Synthetic Application of Homogeneous Charge Transfer Catalysis in the Electrocarboxylation of Benzyl Halides

The results of an investigation on the performances of some outer sphere electron transfer homogeneous catalysts in the electrocarboxylation of 1-(p-isobutyl-phenyl)-1-chloroethane to 2-(p-isobutyl-phenyl)-propionic acid (Ibuprofen), using as catalysts the esters of benzoic and o-, m-, and p-phtalic acids, are reported. The performances of the catalysts are evaluated on the basis of the following parameters: faradic yields of the carboxylation and decomposition of the catalyst. The performances of dimethylisophtalate have been examined in greater detail. The rate of decomposition of the catalyst is related to the molar ratio [halide]/[catalyst].

Development of a membrane-less microfluidic thermally regenerative ammonia battery

Thermally regenerative ammonia battery is a promising approach to make use of waste heat and generate electrical energy. However, according to literature, the price of the energy obtained by this device is much higher than alternative renewable technologies (such as wind, solar, geothermal, etc.). To make the process more viable for applicative purposes, it would be necessary to reduce dramatically the cost of the membrane or to avoid it. Hence, the aim of the present work is to increase the economic figures of thermally regenerative ammonia battery avoiding the use of membranes. It was concluded that this result can be obtained by developing the process in a microfluidic flow cell with lam…

Treatment of aqueous solutions of oxytetracycline by different electrochemical approaches: anodic oxidation, pressurized electro-Fenton and oxidation by electrogenerated active chlorine

The tetracycline group (TCs) includes the most common antibiotics for treatment of both human and animal infections. TCs are resistant to biological degradation; hence, conventional wastewater treatments are unable to remove these contaminants. Here, the utilization of different electrochemical processes, such as electro-Fenton (EF), direct anodic oxidation (AO) and indirect oxidation by electrogenerated active chlorine (EAC), for the treatment of aqueous solutions of oxytetracycline (OTC), which is one of the TCs, was studied. The effect of various operating conditions was evaluated to optimize the selected processes. EAC gave the fastest abatement of OTC, but the lowest removal of TOC and…

Autohydrolysis pretreatment of Arundo donax: a comparison between microwave-assisted batch and fast heating rate flow-through reaction systems

Background: Autohydrolysis of lignocellulosic biomass in liquid hot water has been widely studied owing to its high efficiency and relatively low cost. In the perspective of industrial applications, continuous or semi-continuous processes are more interesting than batch systems. Moreover, microwave heating of pretreatment systems has been proposed to intensify the kinetics of the process. In this study, the autohydrolysis of Arundo donax was performed in pure liquid hot water using a microwave-heated batch reactor and a semi-continuous flow-through reaction system with fast heating rate at the same operating conditions with the aim of performing a systematic comparison between the two diffe…

Towards the electrochemical conversion of CO2 to formic acid at an applicative scale: technical and economic analysis of most promising routes

In the last decade, the electrochemical conversion of CO 2 to formic acid, FA, using Sn‐based cathodes, was widely investigated. In this work, the technical feasibility and economic viability of this process were evaluated considering the most promising electrochemical routes reported in the literature. Five case studies, based on the utilisation of GDE technologies or high CO 2 pressures, were analysed. The cost for producing FA by the electrochemical route was compared with that of the conventional chemical route. Several scenarios were envisioned finding the target figures of merit, the potential bottlenecks (including low FA concentration, GDE cost and high energy consumption) of each t…

Dispersion Copolymerization of Vinyl Monomers in Supercritical Carbon Dioxide.

The thermally initiated free-radical dispersion copolymerization of methyl methacrylate (MMA) and N,N-dimethylacrylamide (DMA) in supercritical carbon dioxide has been studied in the presence of polysiloxane surfactants. The formation of a stable latex seems to be related to the presence of at least one reactive end group in the surfactant macromolecule, thus suggesting that anchoring of the stabilizer to the surface of the growing polymer particles occurs through chemical grafting. In the case of a molar ratio of DMA to MMA lower than 0.40, microspherical copolymer particles with yields ranging from 81 to 97% were collected from batch polymerizations carried out at 65 °C and 23-28 MPa usin…

Surfactant Assisted Polymerization of Tetrafluoroethylene in Supercritical Carbon Dioxide with a Pilot Scale Batch Reactor.

Chain-free radical polymerization of tetrafluoroethylene (TFE) was carried out in supercritical carbon dioxide (scCO2), at 50 °C and 121–133 bar, with tertiary-amyl-per-pivalate as a free radical initiator, using a 5-L pilot scale batch reactor. Experiments were carried out both in the absence and in the presence of perfluoropolyether (PFPE) carboxylate surfactants. Stabilizers were employed under the free acid form and as sodium and calcium salts. An expanded fibrillated poly(TFE) was obtained in all experiments. In the case of surfactant-free polymerizations, the product was mainly constituted by irregular shape macroparticles having size in the range 200–500 μm. Quite interestingly, when…

ELECTROCHEMICAL ABATEMENT OF ORGANIC POLLUTANTS IN WATER IN MICROFLUIDIC DEVICES

Atom transfer radical polymerization with different halides (F, Cl, Br, and I): Is the process "living" in the presence of fluorinated initiators?

Atom transfer radical polymerization (ATRP) is often used for grafting from fluorinated polymers. Nevertheless, the possibility to initiate an ATRP from a C-F functionality and the activity of the catalysts in the presence of fluoride anions are essentially unexplored. Therefore, we investigated the thermodynamics and kinetics of C-F bond activation by ATRP catalysts and compared it with other halide systems. The ATRP equilibrium constant was estimated to be small for the reaction between [CuITPMA]+ and benzyl fluoride (TPMA = tris(2-pyridylmethyl)- amine). However, [CuITPMA] + could react with the more active initiator diethyl fluoromalonate (DEFM). With DEFM as initiator and CuIBr/TPMA as…

Electro-generation of H2O2 and abatement of organic pollutant in water by an electro-Fenton process in a microfluidic reactor

The electro-generation of H2O2 and the abatement of the model organic pollutant Acid Orange 7 (AO7) in water by an electro-Fenton process were performed both in a conventional undivided macro cell and, for the first time, in a microfluidic reactor. Under optimized operative conditions, the reduction of oxygen in the microdevice gave rise, using graphite cathode, to a concentration of H2O2 of about 6 mM, one order of magnitude higher than that achieved in conventional cells. Similarly, when electro-Fenton was performed in the microfluidic reactor a dramatic increase of the abatement of COD was achieved with respect to that obtained in a conventional cell. Keywords: Wastewater treatments, Mic…

Electrochemical reduction of macrocyclic polysulfonamides for the synthesis of polyazamacrocycles

ELECTROCHEMICAL REDUCTION OF CARBON DIOXIDE TO FORMIC ACID AT TIN CATHODE IN DIVIDED AND UNDIVIDED CELLS: EFFECT OF OPERATING PARAMETERS

The electrochemical reduction of carbon dioxide is considered a relevant topic for both the synthesis of chemicals and the decrease of global warming. Electrochemical processes could utilize excess energy from intermittent renewable sources to convert carbon dioxide in various products such as CO, formate and formic acid, methane and ethylene in water and oxalic acid, formic acid, CO as well as carboxylic acids (by reaction with suitable reagents such as aromatic ketones or benzylic halides) in aprotic solvents [1-3]. It has been shown that the selectivity of the process dramatically depends on the nature of the cathode. Four distinct classes of metal catalysts have been identified on the b…

Modeling Heterogeneous copolymerization in scCO2

ScCO2 as polymerization medium for high value polymers: two recent cases

In recent years the use of supercritical carbon dioxide (scCO2) in polymer processing and polymerization reactions has merged as a “green” alternative to replace both organic solvents, environmentally hazardous (VOCs), and water, which use involves the production of large amount of waste streams. ScCO2 is non-toxic, inexpensive, and often exhibits high solubility in polymer matrixes. Moreover, it causes polymer plasticization, thus favoring the diffusion of low MW species (monomers, initiators or additives) in the polymer phase. In this work, the use of scCO2 as polymerization medium for two different special polymers is discussed. Fluorinated copolymers mainly find application in environme…

Electrochemical incineration of oxalic acid in a micro-gap flow cell

INVESTIGATION OF ELECTRODE MATERIAL-REDOX COUPLE FOR REVERSE ELECTRODYALISIS PROCESSES. PART I: IRON REDOX COUPLES.

The performances of electrodialysis (ED) and reverse electrodialysis (RED) processes depend on several factors, including the nature of the electrode material and of the redox couple adopted to make possible the conversion between electric power and chemical potential. In this paper, the possible utilization of iron-based redox couples (FeCl3/FeCl2, hexacyanoferrate(III)/hexacyanoferrate(II) and Fe(III)-EDTA/Fe(II)-EDTA) on graphite and DSA electrodes for RED processes was studied by a detailed experimental investigation. The hexacyanoferrate(III)/hexacyanoferrate(II) system was stable for lonf time (more than 12 days) in the absence of light and oxygen at high redox couple concentrations a…

HYDROTHERMAL LIQUEFACTION OF MICROALGAE IN THE PRESENCE OF HOMOGENEOUS AND HETEROGENEOUS CATALYSTS

The continuous raise in the prices of fossil fuels and the awareness of the society challenges related to their use has recently driven a strong growth of interest on the investigation of different biochemical or thermochemical processes for the production of liquid biofuels .

Investigation of Multicomponent Sorption in Polymers from Fluid Mixtures at Supercritical Conditions:  The Case of the Carbon Dioxide/Vinylidenefluoride/Poly(vinylidenefluoride) System

The simultaneous sorption of carbon dioxide and vinylidene fluoride (VDF) in poly(vinylidenefluoride) from their supercritical (sc) mixtures was studied using an experimental method, already described in a previous publication, based on the gas-chromatographic determination of the equilibrium composition of the fluid phase in contact with the polymer. Argon was added to the system as a nonabsorbable molecular probe in the polymer to take into account the effect of the volume swelling on the measurement. Sorption behavior has been studied at 50 °C by changing the composition and the density of the supercritical phase. We have found that VDF dissolves in its polymer with concentrations much l…

Electrochemical reduction and carboxylation of halobenzophenones

Abstract The electrochemical reduction of a series of halogenated benzophenones XC6H4COC6H4Y (1) was studied in aprotic solvents, in the absence and presence of CO2, by cyclic voltammetry (CV) and controlled-potential electrolysis. The mechanism of electroreduction in dimethylformamide (DMF) has been investigated in some detail. Most of the compounds undergo reductive carbonhalogen bond cleavage in the time window of CV. The radical anions derived from difluorobenzophenones (X=Y=4-F; X=2-F, Y=4-F) as well as from the 3-chloro derivative are quite stable with a cleavage rate constant (kc) of the order of 10−2 s−1 or less. With 4-chloro-, 2-chloro-, 4,4′-dichloro- and 2,4′-dichorobenzophen…

Un unexpected ring carboxylation in the electrocarboxylation of substituted aromatic ketones

Recovery of Perfluoropolyether Surfactants from PVDF and PTFE by Supercritical carbon Dioxide Extraction

Elettrocarbossilazione di alogenuri benzilici su scala preparativa tramite catalisi omogenea di trasferimento di carica e catalisi eterogenea su argento

Dispersion Polymerization of Vynilidene Fluoride in scCO2: Effect of Perfluoropolyether Surfactants on the Molecular weight of the Polymer and Modelling of the Polymerization Kinetics

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: A Robust Approach for Modeling Precipitation and Dispersion Kinetics

A kinetic model is developed for the heterogeneous free-radical copolymerization of vinylidene fluoride and hexafluoropropylene in supercritical CO2. The model accounts for polymerization in both the dispersed (polymer-rich) phase and in the continuous (polymer-free) supercritical phase, for radical interphase transport, diffusion limitations, and chain-length-dependent termination in the polymer-rich phase. A parameter evaluation strategy is developed and detailed to estimate most of the kinetic parameters a priori while minimizing their evaluation by direct fitting. The resulting model predictions compare favorably with the experimental results of conversion and MWD at varying monomer fee…

Effective recovery of perfluoropolyether surfactants from PVDF and PTFE by supercritical carbon dioxide extraction

Abstract The extraction of ammonium carboxylate perfluoropolyether surfactants from poly(vinylidenefluoride) (PVDF) and poly(tetrafluoroethylene) (PTFE) was performed with supercritical carbon dioxide. When proper conditions in terms of temperature, pressure and flow rate were used, extraction recoveries higher than 90% were obtained. For PVDF (with a concentration of surfactant of 5% w/w), at low pressure (12 MPa) and 40 °C, more than 100 min are necessary to have a quantitative extraction. On the other hand, at higher pressure (20 MPa) a quantitative recovery was obtained after few minutes. A strong influence of the temperature on the extraction recovery was also found. In the case of PTF…

Synthesys of coenzymes Qn by electrochemical oxidation of tetramethoxy precursor

Electrochemical detosylation of macrocyclic polysulfonamides for the synthesis of cyclen

Polymerization process

Effect of air pressure on the electro-Fenton process at carbon felt electrodes

Abstract The effect of air pressure on electro-Fenton (PrEF process) was evaluated using two organic substances (maleic acid and Acid Orange 7) as model organic pollutants. First experiments were performed using a conventional carbon felt (CF) cathode. At room pressure, a slow removal of maleic acid was obtained, together with the generation of formic acid. Conversely, using pressurized air, the removal of maleic acid was dramatically accelerated and the formation of formic acid was not detected. The utilization of a carbon felt modified by the deposition of carbon black + PTFE mixture (MCF) and of pressurized air allowed to achieve even faster and almost total (>95%) removal of total organ…

Electrochemical conversion of CO2 to formic acid using a Sn based cathode: Combined effect of temperature and pressure

Electrochemical conversion of CO2 in the aqueous electrolyte into value-added chemicals is considered one of the most promising strategies to valorize waste-CO2. In the last decade, high attention was focused on the electro- chemical synthesis of formic acid (FA) via CO2 reduction using Sn cathodes. To improve the final concentration of FA in aqueous electrolytes, several approaches, including the utilization of different technologies (i.e. pressurized CO2 reactor, a gas diffusion electrode, divided cell etc...) and different operative conditions (i.e. pH, current densities, temperature, mixing rate, etc...) were investigated in detail. To date, the effect of temperature (T) on the electroc…

Reverse electro dialysis processes. Selection of redox processes and electrodes.

ELECTROSYNTHESIS IN MICROFLUIDIC CELLS: PRELIMINARY INVESTIGATIONS

Innovative chemical processes for the treatment of water polluted by recalcitrant organic substances

In the last years, many research groups have focused their attention on the innovative chemical processes adopted for the treatment of water effluents polluted by recalcitrant organic substances, i.e., substances resistant to biological treatment. The electrochemical oxidation is one of the most studied technologies because it presents high versatility and low cost, it is realized under mild conditions of pressure and temperature and generally it does not involve the use of toxic substances [1]. In this work, the comparative performance of different electrochemical approaches such as direct oxidation processes, oxidation by means of electrogenerated chlorine and electro-Fenton was investiga…

Electrochemical production and use of chlorinated oxidants for the treatment of wastewater contaminated by organic pollutants and disinfection

Abstract In the last years, an increasing attention has been devoted to the use of electrogenerated chlorinated oxidants for the treatment of wastewater polluted by recalcitrant organics and/or for the disinfection of water contaminated by pathogen microorganisms. In this review, more recent and relevant findings were presented and critically discussed. The main advantages and disadvantages of this technique were commented, including the potential formation of toxic chlorinated organic specie and of chlorate and perchlorate or the difficult selection of proper operative parameters, as well as the key points that should be addressed to enhance the use on an applicative scale.

ELECTROCHEMICAL ABATEMENT OF AZO 7 IN WATER SOLUTION IN MACRO AND MICRO CELLS

Copolymerization of vinylidene fluoride and acrylic acid in supercritical carbon dioxide

The free-radical copolymerization of vinylidene fluoride (VDF) and acrylic acid (AA) was carried out in supercritical carbon dioxide using both precipitation and dispersion techniques in the presence of an ammonium carboxylate perfluoropolyether compound. Formation of a copolymer was confirmed by variable contact time CP MAS NMR spectroscopy. Macromolecular matrices were significantly enriched in AA with respect to the initial feed composition and we found that the nonfluorinated monomer has a much higher reactivity ratio with respect to VDF. The cumulative concentration, crystallinity, and water affinity of the synthesized copolymers could be modified changing the initial feed composition,…

On the regeneration of thermally regenerative ammonia batteries

In the past few years, thermally regenerative ammonia battery (TRAB) has been proposed as an effective tool to recover waste heat at temperatures below 130 °C. Most of the literature available is devoted to the power production step, with less attention being given to the regeneration step (e.g. the removal of ammonia from the anolyte). In this paper, the TRAB is analyzed with particular attention to the regeneration step and to the study of various generation of energy-regeneration cycles. It was shown that approximately 90 °C is necessary for the regeneration step due to the fact that ammonia is present in the anolyte mainly as a complex. Various cycles were performed with success, demons…

Hydrothermal liquefaction of wet biomass in batch reactors: Critical assessment of the role of operating parameters as a function of the nature of the feedstock

A scientometric analysis of articles published from 1986 to 2022 on batch hydrothermal liquefaction of microalgae, macroalgae, lignocellulosic biomass, sewage sludge and organic wastes in water was performed. We found that biocrude yield can be correlated with the kinetic severity factor (KSF) and scattering of experimental data increases in the supercritical region probably for uncertainty in the medium density affecting the kinetics of reactions involved in the process. The level of correlation and the yield increased when fast heating rates of the reactor, higher than 25 ◦C/min, were adopted. Energy recovery of biocrude obtained in fast heating experiments changes linearly with biocrude …

Improvement of the desorption kinetics and thermodynamics from CaH2+AlB2 system by NbF5 doping

Electrochemical processes in macro and microfluidic cells for the abatement of chloroacetic acid from water

Loading carbonaceous materials with silver for the treatment of chloro-organic compounds in aqueous phase

Many electrochemical technologies, either based on novel concepts (such as microbial fuel cells), experimental setups (such as photoelectrochemical or solar photoelectro-Fenton reactors) or materials (mainly focused on the use of large O2-overpotential anodes like BDD) have been devised in recent years for water remediation. Special attention has been paid to highly toxic, biorefractory organic pollutants such as the chlorinated hydrocarbons, which conjugate toxicity with chemical stability, bioaccumulation and long-range diffusivity [1]. Electroreduction at silver cathodes becomes an interesting alternative to degrade chloro-organic compounds, but it may lead to the accumulation of reactio…

Modification of Poly(vinilydenefluoride) Porous Membranes by Grafting of Acrylic Acid Assisted by Supercritical Carbon Dioxide

Aim of this work is to study the preparation of pH sensitive membranes for biomedical applications via thermally induced graft polymerization of acrylic acid (AA) on poly(vinilydenefluoride) (PVDF) assisted by supercritical carbon dioxide (scCO2). Using scCO2 as a solvent and swelling agent, the monomer and the initiator (benzoyl peroxide) could diffuse faster into the polymer matrix, distribute more uniformly and allows a better control of the final molecular architecture promoting grafting reactions rather than chain degradation processes. As polymer matrixes we are using commercial hydrophobic porous PVDF membranes. Grafted polymers are characterized by Fourier transform infrared spectro…

Electrocarboxylation of Benzyl Halides through Redox Catalysis on the Preparative Scale

The electrocarboxylation of benzyl halides to the corresponding carboxylic acids through homogeneous charge-transfer catalysis was investigated both theoretically and experimentally to determine the influence of the operative parameters on the yield of the process and on the catalyst consumption. Theoretical considerations, based on fast kinetics of redox catalysis, were confirmed by the electrocarboxylation of 1-phenyl-1-chloroethane catalyzed by 1,3-benzenedicarboxylic acid di methyl ester performed at a carbon cathode under different operative conditions. We obtained high yields of the target carboxylic acid and experienced a low catalyst consumption by operating with optimized [RX]bulk/…

Oxidation of organics in water in microfluidic electrochemical reactors: Theoretical model and experiments

The electrochemical oxidation of organics in water performed in micro reactors on boron doped diamond (BDD) anode was investigated both theoretically and experimentally in order to find the influence of various operative parameters on the conversion and the current efficiency CE of the process. The electrochemical oxidation of formic acid (FA) was selected as a model case. High conversions for a single passage of the electrolytic solution inside the cell were obtained by operating with proper residence times and low distances between cathode and anode. The effect of initial concentration, flow rate and current density was investigated in detail. Theoretical predictions were in very good agr…

ChemInform Abstract: Photoinduced Single Electron Transfer on 5-Aryl-1,2,4-oxadiazoles: Some Mechanistic Investigations in the Synthesis of Quinazolin-4-ones.

The photochemistry of some 5-aryl-3-methoxy- (or 5-aryl-3-phenyl-) 1,2,4-oxadiazoles irradiated in the presence of different sensitizers [such as diphenylacetylene (DAC), 9,10-diphenylanthracene (DAN), or triphenylene (TPH)] or ground-state donors such as triethylamine (TEA) has been investigated. Intermediates arising from breaking of the ring O-N bond develop both into quinazolin-4-ones (by a heterocyclization reaction involving the aryl at the C-5 of the oxadiazole nucleus) and into open-chain products (corresponding to a reduction at the ring O-N bond), in different ratios depending on their structures and photoreaction conditions. A reasonable explanation considers sensitization by pho…

Robust Mesoporous CoMo/γ-Al2O3 Catalysts from Cyclodextrin-Based Supramolecular Assemblies for Hydrothermal Processing of Microalgae: Effect of the Preparation Method

Hydrothermal liquefaction (HTL) is a promising technology for the production of biocrude oil from microalgae. Although this catalyst-free technology is efficient under high-temperature and high-pressure conditions, the biocrude yield and quality can be further improved by using heterogeneous catalysts. The design of robust catalysts that preserve their performance under hydrothermal conditions will be therefore very important in the development of biorefinery technologies. In this work, we describe two different synthetic routes (i.e., impregnation and cyclodextrin-assisted one-pot colloidal approach), for the preparation in aqueous phase of six high surface area CoMo/γ-Al2O3 catalysts. Cat…

Electrochemical abatement of chloroethanes in water: Reduction, oxidation and combined processes

An electrochemical route, based on the anodic oxidation to carbon dioxide coupled with the cathodic reduction to de-halogenated hydrocarbons, was proposed for the treatment of waters contaminated by chloroethanes. The electrochemical abatement of two model compounds, namely 1,2-dichloroethane and 1,1,2,2-tetrachloroethane, was carried out by cathodic reduction at silver, anodic oxidation at boron doped diamond (BDD) and combined processes. The anodic oxidation gives rise to a high abatement of the concentration of both these compounds and of COD. The reduction of 1,1,2,2-tetrachloroethane proceeds also with high abatement but with the formation of some halogenated intermediates and final pr…

Electrochemical incineration of organic pollutants: effect of the nature of the pollutants and of the temperature

The electrochemical oxidation of some organic pollutants, including three carboxylic acids (oxalic, formic and maleic), at boron doped diamond (BDD) and DSA anodes, using galvanostatic alimentation, was investigated in order to study the effect of the temperature and of the nature of the pollutants on the process. In incineration electrolyses, the performances of the process in terms of carboxylic acid conversion and current efficiency dramatically depend on the adopted operative conditions. The abatement of the organic pollutant depends on the nature of the carboxylic acid. Quite interestingly, the opposite effect of the nature of the substrate on the performances of the process was observ…

Catalytic systems based on transition metals for the carbonylation of methanol to dimethylcarbonate

Abstract The results of an investigation on catalytic systems arising from the electrochemical activation of salts and complexes of several transition metals for the carbonylation of methanol to dimethylcarbonate (DMC) are reported. Metals were tested as inorganic salts or complexes with ligands such as 2,2′-bipyridine (bipy), 1,6-bis (2-oxyphenyl)-2,5-diaza-1,5-hexadiene (salen), 2,4-pentanedionate (acac), triphenylphosphine (TPP) in methanol at room temperature saturated with carbon monoxide at atmospheric pressure. Best faradic yields vs DMC were observed as follows: CuCl(bipy): 84.8%; PdCl 2 (bipy): 64.0%; CoCl 2 : 26.0%; RhCl 3 : 25.0%; AgBF 4 (bipy): 10.2%; AuCl 3 : 9.4%; Cr(acac) 3 :…

STUDIO DI PROCESSI ELETTROCHIMICI PER L’ABBATTIMENTO DI INQUINANTI ORGANICI IN ACQUA IN MACRO E MICRO REATTORI

Modification of PVDF nanoparticles by controlled free radical graft copolymerization in supercritical carbon dioxide

PVDF (polyvinylidenefluoride) membranes are widely used in microfiltration (MF) and ultrafiltration (UF) due to their excellent processability, chemical resistance, well-controlled porosity, and good thermal properties [1]. Moreover this polymer is also frequently adopted in bio-medical devices owing to its good biocompatibility [2]. On the other hand, the use of PVDF membranes in biomedical applications is limited to some extent by the hydrophobicity of their exposed area, which mainly arises from the nature of the pore surface. Prompted by these considerations in the present work we have studied the modification of PVDF nanoparticles with hydroxyethylmethacrylate (HEMA) thus obtaining a m…

Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one-pot route for the preparation of controlled delivery systems

The polymerization of 1-vinyl-2-pyrrolidone in supercritical carbon di- oxide in the presence of ibuprofen as a model drug was investigated as a new one-pot process for the preparation of polymer-based drug delivery systems (DDSs). The com- posites were prepared at 65 � C and P ¼ 31-42 MPa by changing the initial con- centration of the drug and the concentration of a crosslinking agent and that of a hydrophobic comonomer. The effects of these parameters on the performances of the polymerization and on the in vitro release kinetics of ibuprofen were studied. In all the experiments, part of the drug was entrapped inside the polymer particles and dissolved more slowly with respect to the pure …

Dispositivi microfluidici per lo studio di reazioni elettrochimiche

Supercritical carbon dioxide induces sterilization of PLLA scaffolds contaminated by E. coli.

The common sterilization techniques are based on physical processes that involve, for example, the use of autoclaves or systems to radiation such as γ-rays that can cause a structural change of the polymer treated. Therefore, the use of supercritical carbon dioxide (scCO2) is an excellent alternative, as it does not induce any variation of biomaterials treated (Perrut M., 2012). It's a good candidate because is readily available at low cost, non-toxic and non-flammable, it has an easily accessible critical point (7.38 MPa and 304.2 K) and excellent transport properties and wettability (White A. et al., 2005). We report the development of a supercritical CO2 based process capable of steriliz…

ELECTROCHEMICAL MICROREACTORS FOR THE ABATEMENT OF ORGANIC POLLUTANTS IN WATER SOLUTION

Electrochemical methods can offer new sustainable routes for the abatement of organic pollutants resistant to biological processes. These methods use a clean reagent, the electron, and very mild operative conditions (ambient temperature and atmospheric pressure) with limited operative costs. However, electrochemical processes present some important disadvantages when performed in conventional reactors. In particular, to achieve reasonable cell voltages when the medium has not an adequate conductivity, one needs adding to the system a supporting electrolyte. This is certainly a main obstacle for a wide application of electrochemical tools. Indeed, adding chemicals is often a problematic issu…

Electrochemical synthesis of coenzymes Qn by oxidation of tetramethoxy precursors

The electrochemical oxidation of tetramethoxy precursors (2) to coenzymes Q (n) (1) at a carbon anode was investigated both in a bench-scale batch electrochemical reactor and in a continuous recirculation reaction system equipped with a parallel-plate electrochemical divided cell. High faradic efficiency (> 60%) and excellent selectivity (> 90%) in coenzymes Q (n) were obtained in CH3CN or CH3CN/CH2Cl2 + 0.15 M Bu4NBF4 under potentiostatic or amperostatic alimentation.

Preparation of pH sensitive poly(vinilydenefluoride) porous membranes by grafting of acrylic acid assisted by supercritical carbon dioxide

Aim of this work is to study the preparation of pH sensitive membranes for biomedical applications via thermal induced graft polymerization of acrylic acid (AA) on poly(vinilydenefluoride) (PVDF) assisted by supercritical carbon dioxide (scCO2). Using scCO2 as a solvent and swelling agent, the monomer and initiator (benzoyl peroxide) could diffuse faster and distribute more uniformly into the polymer matrix. A better control of the final molecular architecture should be achieved because bimolecular grafting reactions are accelerated with respect to chain degradation processes. Commercial hydrophobic PVDF porous matrixes were selected as model membranes. Grafted polymers were characterized b…

Electrochemical Synthesis of d,l-Homocysteine Thiolactone Hydrochloride in a Batch Continuous Recirculation Reactor Equipped with Carbon Felt Cathodes:  A Study for the Optimization of the Process

The electrochemical reduction of D,L-homocystine hydrochloride to the corresponding cysteine was performed in a batch continuous recirculation reaction system that was equipped with a FM01-LC electrochemical reactor. Electrolyses were performed under amperostatic conditions, using carbon felt cathodes and DSA anodes divided by Nafion 324 cationic membranes. A simple reactor mathematical model was used to assess the effect of operative parameters (the initial substrate concentration, the reaction temperature, the current density, and the linear velocity of the catholyte) on the performances of the process, with the objective of determining the optimized conditions to perform the electrosynth…

Electrochemical conversion of CO2 to formic acid using a Sn based electrode: A critical review on the state-of-the-art technologies and their potential

Abstract The electrochemical conversion of carbon dioxide is considered one of the most promising strategies to convert waste-CO2 into value-added chemicals. This review focuses on the synthesis of formic acid/formate in aqueous electrolyte using Sn-based cathodes; this material is considered relatively cheap and shows promising results in terms of faradaic efficiency. In order to be suitable at an industrial scale, the process should present simultaneously high current densities, faradaic efficiencies close to 100%, high concentrations of formic acid and long-term stability. Analysing the main results reported in the literature, it was observed that to date further studies are necessary to…

Electrocarboxylation of aromatic ketones: Influence of operative parameters on the competition between ketyl and ring carboxylation

Abstract The purpose of this work is to investigate the effect of operational parameters on the competition between the formation of the target 2-hydroxy-2-arylpropanoic acid and ring carboxylation in the electrocarboxylation of aromatic ketones. For the investigated ketones, this competition has been found to be dramatically influenced by different parameters such as the water content and the ratio between the carbon dioxide and the ketone concentrations (q = [CO2]/[ketone]). In particular, the target carboxylic acid formation can be favoured with respect to ring carboxylation by operating at high q ratios or by addition of small amounts of H2O to the reaction medium. An increase of the wa…

Reduction of oxygen to H2O2 at carbon felt cathode in undivided cells. Effect of the ratio between the anode and the cathode surfaces and of other operative parameters

Abstract In the last years, the electrochemical conversion of oxygen to hydrogen peroxide at carbon felt has been largely studied in order to define a new route for the production of H2O2 and to optimize the electro-Fenton process, which is based on the cathodic generation of H2O2. In particular, many studies regarding electro-Fenton process were carried out in undivided cells in order to avoid the costs of the separator and to reduce the cell potentials. Hence, in order to optimize the cathodic conversion of oxygen to H2O2 in undivided cells, the effect of many parameters linked to the anodic process were here evaluated. In particular, it was demonstrated that the performances of the proce…

Polymerization of methyl methacrylate through ionizing radiation in CO2-based dense systems

Herein, we report the use of ionizing radiation to induce a dispersion polymerization reaction in dense CO2. As a model system, the polymerization of methyl methacrylate in the presence of poly(dimethylsiloxane) stabilizers was investigated. It was demonstrated that the dose plays the key role in the progress of the reaction and in the morphology of the resulting polymer. Dispersion polymerization carried out in the presence of mono- and bifunctionalized surfactants gave differently structured polymers. The polymers obtained have been characterized by scanning electron microscopy, solubility tests, and gel permeation chromatography, and the molecular structure has been related to dynamic me…

Electrochemical treatment of wastewater contaminated by organics and containing chlorides: Effect of operative parameters on the abatement of organics and the generation of chlorinated by-products

Abstract In the last years, large attention has been devoted to the electrochemical treatment of wastewater polluted by recalcitrant organics and containing chlorides. However, the utilization on an applicative scale of this route is limited by the fact that usually it is not possible to achieve high removals of organics without the generation of significant amounts of chlorinated by-products. Here, the role of several operative parameters on the performances of the process was systematically evaluated using phenol as a model organic pollutant. It was shown that the removal of phenol and TOC and the generation of many by-products including chlorophenols, chloroacetic acids, chlorate and per…

Electrochemical reduction of carbon dioxide to formic acid at a tin cathode in divided and undivided cells: effect of carbon dioxide pressure and other operating parameters

Abstract The reduction of carbon dioxide to formic acid at a tin cathode was studied in both divided and undivided cells. In the first stage of the study, the effect of some operating parameters, including the working potential and the nature of the supporting electrolyte and of the cathode, on both the cathodic reduction of CO2 and the anodic oxidation of formic acid was investigated in a divided cell. In a second stage, the reduction of carbon dioxide was performed in an undivided cell with the aim of studying the effect on the generation of formic acid of various operating parameters such as current density, cathode to anode area ratio, mixing rate and nature of the anode and of the supp…

Development of a process for the treatment of synthetic wastewater without energy inputs using the salinity gradient of wastewaters and a reverse electrodialysis stack.

Abstract Electrochemical processes are considered very effective methods for the treatment of wastewater contaminated by organics resistant to conventional biological processes and various inorganic pollutants. Large sites that treat wastewaters usually deal with a large number of waters often characterized by different salinity contents, that could be potentially used to provide the energy necessary for the electrochemical remediation. Hence, in this work a reverse electrodialysis (RED) process for the treatment of synthetic wastewaters contaminated by organics, without energy inputs, using the salinity gradient of different wastewaters, was studied, for the first time. It was found that t…

Hydrothermal liquefaction of wet waste biomass: a practical assessment to achieve an integral valorization of municipal sludge

Hydrothermal liquefaction of municipal sludge was conducted to perform a practical assessment to achieve an integral valorization of this wet waste biomass. Experiments were done to investigate the effects of sub- and supercritical water and of the fluid dynamic regime on the energy recovery of the process and on the quality of the products. Experimental runs were performed at two different temperatures (350°C and 400°C) changing reaction time in order to work at the same kinetic severity of the process (LogR0=8.9, calculated as in ref. [3]). An improvement of the C % in the solid residues and of the ration of H/C of the biocrude was obtained when stirred reactor was used both in sub- and s…

Complexation of phosphine ligands with peracetylated β-cyclodextrin in supercritical carbon dioxide: spectroscopic determination of equilibrium constants

The interaction between peracetylated beta-cyclodextrin and several triphenyl phosphine derivatives was studied in supercritical carbon dioxide (scCO2) by UV-visible spectroscopy. The equilibrium constant for a 1:1 complexation reaction was obtained from titration spectra and calculated using two established mathematical models. The values of the equilibrium constants are 1-3 orders of magnitude smaller than those obtained in aqueous solution with analogous phosphines. This is likely due to the absence in scCO2 of the hydrophobic effect, which is replaced by a corresponding, but weaker, CO2-phobic effect. The largest value of Kf was found for complexes of diphenyl(4-adamantylphenyl)phosphin…

Influence of the nature of the substrate and of operative parameters in the electrocarboxylation of halogenated acetophenones and benzophenones

Abstract The electrocarboxylation of halogenated acetophenones and benzophenones to the corresponding hydroxycarboxylic acids has been carried out in undivided cell equipped with aluminium sacrificial anode and using 1-methyl-2-pyrrolidinone (NMP) as the solvent. The radical anion generated by the electro-reduction of the aromatic ketone is involved in several competitive reactions which lead to the formation of the target hydroxycarboxylic acid, the corresponding alcohol and pinacol and the de-halogenated parent ketone. If sufficiently negative working potentials are imposed, the latter is reduced to the corresponding carboxylate, pinacol and alcohol. Very different results in terms of sel…

Investigation of electrode material – redox couple systems for reverse electrodialysis processes. Part II: Experiments in a stack with 10–50 cell pairs

Abstract The performances of reverse electrodialysis depend on several factors, including the nature of the electrode material and of the redox processes adopted to make possible the conversion between chemical potential and electric power. In this paper the possible utilization of various redox processes (reduction/oxidation of iron species, oxidation and reduction of water, oxidation of chlorine and reduction of water) was studied in a stack equipped with 10–50 cell pairs and by focused electrolyses in a three compartment cell. The effect of selected redox processes on power density output and eventual contamination of saline solutions flowing in the stack was evaluated in detail. The eff…

Effect of Pressure on the Electrochemical Conversion of CO2 to CO

To minimize the negative effect of carbon dioxide as a greenhouse gas and introduce renewable energy in the chemical and energy chain, an interesting approach is the Carbon Capture and Conversion. In this context, one of more appealing conversion strategies is the el Ectrochemical reduction of CO2, which could combines the utilization of excess electric energy from intermittent renewable sources with CO2 (1). Furthermore, CO2 can be selectively converted into various useful chemicals by changing the operating conditions of electrolysis. In particular, an increasing attention has been devoted to the electrochemical conversion of carbon dioxide to carbon monoxide (2,3). The main obstacle of t…

Electrochemical Oxidation of Carboxylic Acids in Water at Boron-Doped Diamond (BDD) Anodes in the Range of Potential of Oxygen Evolution: Detection Measurements and Studies on the Reaction Mechanism

The electrochemical oxidation in water solutions of selected carboxylic acids (namely oxalic, formic, acetic, maleic, and succinic) at boron-doped diamond (BDD) anodes was investigated by polarization and chronoamperometric measurements. In the presence of low concentrations of carboxylic acids, current densities changed approximately linearly with the acid concentrations. Furthermore, when the current densities were plotted as a function of the chemical oxygen demand, a similar response was observed for all the investigated acids with the exception of oxalic acid. For high carboxylic acid concentrations, the linear variation is often loosen and different behaviors are observed depending on…

Electrochemical incineration of oxalic acid in a micro gap flow cell

ELECTROCHEMICAL PROCESSES FOR THE TREATMENT OF CHLORINATED ALIPHATIC HYDROCARBONS IN WATER SOLUTIONS

Electrochemical Synthesis of D,L-Homocysteine Thiolactone Hydrochloride in Batch Continuous Recirculation Reactor Equipped with Carbon Felt Cathodes: a Study for the Optimization of the Process.

A one-pot method to enhance dissolution rate of low solubility drug molecules using dispersion polymerization in supercritical carbon dioxide

ELECTROCHEMICALLY ASSISTED ATOM TRANSFER RADICAL GRAFT COPOLYMERIZATION. PRELIMINARY STUDIES

Atom transfer radical polymerization (ATRP) is a versatile technique for exerting precise control over polymer molecular weights, molecular weight distributions, and complex architectures. It has been recently shown that an externally applied electrochemical potential can reversibly activate the copper catalyst for this process by a one-electron reduction of an initially added air-stable cubric species (Cu(II)/Ligand) [1-2]. In particular Gennaro and co-authors have shown that the polymerization kinetic can be changed modulating the external potential [1-2]. In the last years, an increasing interest has been devoted to synthesis of graft copolymers obtained from commercial polymers for inco…

Influence of operative parameters on the electrocarboxylation of benzyl halides at silver cathodes

γ-radiation-initiated polymerization of vinylidene fluoride in dense carbon dioxide

The γ-ray-initiated batch polymerization of vinylidene fluoride (VF2) has been investigated in dense carbon dioxide under relatively mild operative conditions (T ≤ 40 °C and P < 25 MPa). When the initial VF2 molar concentration was increased from 3.4 to 6.4 mol/L, monomer conversion increased from 20 to 73%; a similar trend was observed for the number-average molecular weight and the molecular complexity of synthesized poly(vinylidene fluoride) (PVDF) as determined from rheological measurements. Under all adopted experimental conditions, a synthesized PVDF polymer was collected in the form of a white powder. Despite the inherent heterogeneous character of the polymerization process, a homog…

CO2 as a C1-organic building block: Electrocarboxylation of aromatic ketones. A quantitative study of the effect of the concentration of substrate and of carbon dioxide on the selectivity of the process

The purpose of this work is to establish and discuss quantitative relationships between the selectivity in preparative scale electrolysis and intrinsic and operational parameters for the electrocarboxylation of aromatic ketones. For the investigated ketones, under appopriate experimental conditions the selectivity of the process is mainly determined by the competition between carboxylation and protonation, de-halogenation reactions (when an halogenated ketone is involved), and possibly dimerizations involving the electrogenerated radical anion. A simple model was proposed to account for these unwanted side paths which allows to predict the dependence of the selectivity as a function of the …

A single-chamber membraneless microbial fuel cell exposed to air using Shewanella putrefaciens

Abstract Microbial Fuel Cells (MFCs) are bio-electrochemical devices which convert the chemical energy content of organic fuels into electricity, thanks to the ability of anode respiring bacteria to give electrons to the anode. This result is usually achieved under anaerobic conditions, obtained with a sealed anode chamber. Despite this, Shewanella oneidensis has been recognized by many authors to obtain the same results in presence of air. Furthermore, another member of the Pseudomonaceae family, Shewanella putrefaciens, has also shown the capability to catalyze the cathodic oxygen reduction. In this work the capability of S. putrefaciens to work under both anaerobic and micro-aerobic cond…

Effect of pressure on the electrochemical generation of hydrogen peroxide in undivided cells on carbon felt electrodes

The electrochemical generation of H2O2can be performed in aqueous solutions by cathodic reduction at carbonaceous cathodes of oxygen coming from air. The performances of the process in terms of concentration of H2O2and current efficiency (CE) are limited by the low solubility of oxygen in water at atmospheric pressure. However, the solubility of oxygen can be increased upon enhancing the air pressure. The effect of pressure on the electrochemical generation of hydrogen peroxide was studied in undivided cells changing the pressure from 0 to 30 relative bar and the current density from 1 to 100 mA cm−2. Simple carbon felt and compact graphite cathodes were first used. A dramatic effect of…

Valorization of alginate for the production of hydrogen via catalytic aqueous phase reforming

Abstract Alginate, a carbohydrate abundant in the outer cell wall of macroalgae, was subjected to catalytic aqueous phase reforming (APR) to produce hydrogen using a 3% Pt/C commercial catalyst. The performance of the process was evaluated according to the conversion of the carbon to gas, the hydrogen yield and the hydrogen selectivity. The catalyst and feed amount, temperature, reaction time, pH and the presence of H2 were modified to understand the dependence of the outcome of the process on these parameters. The presence of the catalyst was fundamental in order to increase the hydrogen yield compared to the uncatalyzed reaction, and it can be reused without activity loss. In addition, it…

Host–guest inclusion complexes between peracetylated β-cyclodextrin and diphenyl(4-phenylphenyl)phosphine : computational studies

PM3 and molecular dynamic calculations were performed upon the inclusion complexation of peracetylated β-cyclodextrin (Per-Ac-β-CD) with diphenyl(4-phenylphenyl)phosphine (DBP). Results show that the 4-phenylphenyl part of the DBP phosphine fits tightly in the cavity of the Per-Ac-β-CD, leading to the formation of stable inclusion complexes. Complexation energies indicate that the complex formed via the primary side of the Per-Ac-β-CD is more stable than that formed via the secondary side. Electrostatic potential mapping and frontier orbital analysis suggest that van der Waals interaction constitute a major driving force in the complexation of the DBP and Per-Ac-β-CD.

Effect of interfacial area on heterogeneous free radical grafting of vinyl monomers in supercritical carbon dioxide: Grafting of acrylic acid on poly(vinylidenefluoride) nanoparticles

The role of the polymer interfacial area on free radical grafting of acrylic acid (AA) onto poly(vinylidenefluoride) (PVDF) was studied at 65°C using supercritical carbon dioxide (scCO2) as a solvent and swelling agent, benzoylperoxide (BPO) as chemical initiator and PVDF nanoparticles as polymer matrix. Under adopted conditions PVDF particles do not melt neither dissolve in the reaction medium and FTIR analyses performed on carefully washed nanoparticles confirmed the achievement of high grafting levels. The mass fraction of grafted AA increased with the grafting time and the BPO concentration while it decreased when the density of the fluid phase was enhanced. Collected results suggest th…

Experimental investigation and modelling of sorption phenomena in high pressure CO2/VDF/PVDF ternary systems

Electrochemical treatment of aqueous solutions of catechol by various electrochemical advanced oxidation processes: Effect of the process and of operating parameters

Abstract Catechol, one of the most abundant compounds in olive mills wastewaters, which is generated in the Fenton degradation of various aromatic compounds, is a toxic, possible carcinogen, persistent pollutant and it is not readily biodegradable. Hence, its degradation requires the utilization of advanced oxidation processes (AOPs). Here, the electrochemical treatment of aqueous solutions of catechol was investigated. The utilization of various electrochemical processes, such as electro-Fenton (EF), direct anodic oxidation (AO), indirect oxidation by electro-generated active chlorine and coupled processes was investigated. Furthermore, the effect of various operating conditions (including…

Synthesis of hydrophilic polymers in supercritical carbon dioxide in the presence of a siloxane-based macromonomer surfactant: Heterogeneous polymerization of 1-vinyl-2 pyrrolidone

Batch free radical polymerization of 1-vinyl-2-pyrrolidone (VP) in super- critical carbon dioxide (scCO2) was studied in the presence of a reactive polysiloxane surfactant (PDMS-mMA). Phase behavior investigation showed that when the initial concentration of the surface active macromonomer was higher than 2.5% w/w with respect to the monomer, the reaction mixture, in the absence of efficient stirring, was initially opaque to the visible light, and it slowly turned to an orange tint. Polymeriza- tion experiments carried out with surfactant concentration higher than the aforemen- tioned value proceeded with a fast kinetics, and led to the formation of spherical nanoparticles with almost quant…

Electrochemical conversion of carbon dioxide to formic acid: on the road to applicative scale

In this context, electrochemical reduction of CO2 is considered one of the more attractive pathway to convert CO2, because the products can be selectively controlled by changing the operative conditions of the electrolysis. In the last years, an increasing attention has been devoted on the electrochemical conversion of CO2 to formic acid in water [2,3]. The main hurdle of the reduction of CO2 from water solution is the low CO2 solubility in water. In this work, the effect of some operating parameters, including pressure, current density, and flow rate, on the conversion of CO2 at tin flat cathodes to formic acid was studied using a pressurized filter-press cell with a continuous recirculati…

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: A Robust Approach for Modeling Precipitation and Dispersion Kinetics

A kinetic model is developed for the heterogeneous free-radical copolymerization of vinylidene fluoride and hexafluoropropylene in supercritical CO 2. The model accounts for polymerization in both the dispersed (polymer-rich) phase and in the continuous (polymer-free) supercritical phase, for radical interphase transport, diffusion limitations, and chain-length-dependent termination in the polymer-rich phase. A parameter evaluation strategy is developed and detailed to estimate most of the kinetic parameters a priori while minimizing their evaluation by direct fitting. The resulting model predictions compare favorably with the experimental results of conversion and MWD at varying monomer fe…

Cathodic reduction of CO2 to formic acid: Effect of the nature of the cathode for pressurized systems

Electrochemical conversion of CO2 into formic acid (FA) in an aqueous electrolyte is considered a promising strategy to valorise waste-CO2. Some studies, mainly performed using Sn cathodes, have shown that the performance of the process can be strongly improved using pressurized systems. On the other hand, other studies, usually carried out in non-pressurized systems, have indicated that the nature of the cathode can strongly affect the process. Hence, in this work, we have investigated the coupled effect of nature of the cathode and CO2 pressure (PCO2 ) on the electrochemical conversion of CO2 to FA. Four electrodes (Sn, Sn/C-NP, Bi, Bi/C-NP) have been used as model cathodes. The results o…

Synthesis of polymer nanogels by electro-Fenton process: investigation of the effect of main operation parameters

Recently, electro-Fenton (EF) process has been shown as a promising, facile, effective, low cost and environmentally-friendly alternative for synthesizing polymer nanogels suitable as biocompatible nanocarriers for emerging biomedical applications. Here, the electrochemically-assisted modification of poly(vinylpyrrolidone) (PVP) by EF process was studied to assess the role of key operation parameters for a precise modulation of polymer crosslinking and its functionalization with [sbnd]COOH and succinimide groups. The dimensions of the nanogels, in terms of hydrodynamic radius (Rh) and weight-average molecular weight (Mw), can be tuned up by controlling the electrolysis time, current density…

Sorption of high pressure fluid mixtures into semi-crystalline polymers: investigation of the system carbon dioxide/vinylidenefluoride/poly(vinylidenefluoride)

A novel experimental apparatus for measuring gas absorption has been adopted to study sorption of carbon dioxide CO2 and vinylidenefluoride (VDF) in a semi crystalline polymer, namely poly(vinylidenefluoride) (PVDF). The experimental technique allows to calculate simultaneous absorption of different components in the polymer phase, through a gas chromatographic determination of the composition of the fluid phase. To take into account indirectly the polymer swelling, a suitable not-absorbable probe, namely argon, has been added to the fluid phase. Concentrations of molecules absorbed in the polymer phase were simply calculated through mass balance equations written for each component in the …

Photoinduced Single Electron Transfer on 5-Aryl-1,2,4-oxadiazoles:  Some Mechanistic Investigations in the Synthesis of Quinazolin-4-ones

The photochemistry of some 5-aryl-3-methoxy- (or 5-aryl-3-phenyl-) 1,2,4-oxadiazoles irradiated in the presence of different sensitizers [such as diphenylacetylene (DAC), 9,10-diphenylanthracene (DAN), or triphenylene (TPH)] or ground-state donors such as triethylamine (TEA) has been investigated. Intermediates arising from breaking of the ring O-N bond develop both into quinazolin-4-ones (by a heterocyclization reaction involving the aryl at the C-5 of the oxadiazole nucleus) and into open-chain products (corresponding to a reduction at the ring O-N bond), in different ratios depending on their structures and photoreaction conditions. A reasonable explanation considers sensitization by pho…

Utilization of impedance spectroscopy to investigate the self-assembly behavior of amphiphiles soluble in supercritical carbon dioxide: Preliminary results

Abstract A mixture of CO 2 , water, methyl orange (MO) and Dynol 604 surfactant was analyzed at 309 K and 20 MPa simultaneously by impedance and UV–vis spectroscopy. A plot of the static dielectric constant as a function of the surfactant concentration was obtained using a suitable equivalent circuit to elaborate impedance data. Experimental points can be fitted by two different straight lines whose intersection occurs at about 0.13% (w/w) concentration of Dynol. When the surfactant concentration crossed the aforementioned value, a peak was detectable in the UV–vis spectrum at a wavelength range corresponding to the absorption of MO; absorbance of the peak increased with the surfactant conc…

Synthesis of cyanoacetic acid by electrocatalytic carboxylation of chloroacetonitrile at a silver cathode

Hydroformylation of 1-Octene in scCO2 with Rh Catalyst in the Presence of Non-fluorinated Ligands

Facile crosslinking of poly(vinylpyrrolidone) by electro-oxidation with IrO2-based anode under potentiostatic conditions

Abstract: The modification of polymer architectures by reaction with chemically adsorbed hydroxyl radicals has been thoroughly investigated by electrolyzing dilute aqueous solutions of the biocompatible polymer poly(vinylpyrrolidone) (PVP), using an undivided electrolytic cell with a Ti/IrO2–Ta2O5(DSA®) anode. Several electrolyses were performed to assess the influence of the applied potential, the circulated charge and the PVP concentration, which was always kept low to avoid chain overlapping. From the results obtained, it can be concluded that the electro-oxidation of PVP solutions using a cheap anode is an effective method to crosslink initially isolated polymer chains, eventually incre…

Direct electrochemical detosylation of tetratosylcyclen to cyclen with carbon cathodes

The electrochemical detosylation of tetratosylcyclen to cyclen (1,4,7,10-tetraazacyclododecane) in aprotic solvents at a carbon cathode was investigated both in a bench-scale batch electrochemical reactor and in a continuous batch recirculation reaction system equipped with a parallel-plate electrochemical cell. Yields and faradaic efficiency in cyclen, respectively, of 80 and 55% were obtained in the bench-scale reactor working in acetonitrile. It was found that the faradaic efficiency in cyclen depends on the competition between the reduction of the tetratosylcyclen and parasitic processes as the reduction of the tetraalkylammonium cations present in the supporting electrolyte. We have ob…

Sewage sludge as cheap alternative to microalgae as feedstock of catalytic hydrothermal liquefaction processes

Abstract Production of biocrude through hydrothermal liquefaction (HTL) of sewage sludge (SS) and Chlorella vulgaris was investigated. NiMo/Al2O3 (KF 851), CoMo/Al2O3 (KF 1022) and activated carbon felt, tested as catalysts at 598 K for 30 min, did not change the biocrude yield but significantly improved its quality. Quantitative sulfur removal and lower oxygen content were found in biocrude when KF 851 and KF 1022 were used with C. vulgaris. The same catalysts decreased O/C and S/C ratio of the biocrude from SS. The highest HHV (38.19 MJ/kg) and H/C ratio (1.65) and the lowest O/C (0.11) of the biocrude from SS were obtained with the cheaper activated carbon felt. A new product phase, prob…

Interesterification of rapeseed oil catalyzed by tin octoate

The interesterification of rapeseed oil was performed for the first time by using tin octoate as Lewis acid homogeneous catalysts and methyl or ethyl acetate as acyl acceptors in a batch reactor, within the temperature range 393e483 K. The yields in fatty acid ethyl esters (FAEE) and triacetin (TA) after 20 h of reaction time increased from 8% and 2%eto 61% and 22%, respectively, when the reaction temperature increased from423 to 483 K. An optimum value of 40 for the acyl acceptor to oil molar ratio was found to be necessary to match good fatty acid alkyl ester yields with high enough reaction rate. The rate of generation of esters was significantly higher when methyl acetate was used as acyl …

Continuous dispersion polymarization of vinyl monomers in supercritical carbon dioxide

Electrochemical Incineration of oxalic acid at boron doped diamonds

An unexpected ring carboxylation in the electrocarboxylation of aromatic ketones

The electrocarboxylation of various aromatic ketones, carried out in N-methyl-2-pyrrolidone (NMP) in a diaphragmless cell equipped with a carbon cathode and an aluminium sacrificial anode, yielded, among the products, the target hydroxy acids, the corresponding alcohols and pinacols and, quite surprisingly, detectable amounts of substituted benzoic acids and cycloexene carboxylic acids. These compounds arise from a never reported before electrocarboxylation on the aromatic ring, respectively, for substitution of an aromatic hydrogen and from an addition reaction. For example, the electrocarboxylation of acetophenone gave rise to the substituted benzoic acids in ortho, para and meta position…

ABATEMENT OF POLLUTANTS IN WATER BY DIFFERENT ELECTROCHEMICAL APPROACHES

Synthesis of fluoropolymers in supercritical carbon dioxide: relevance for industrial applications

Electrochemical Abatement of Organic Pollutants in Water by Electro- Fenton with Natural Heterogeneous Catalysts Under Pressure

In recent decades, electrochemical advanced oxidation processes (EAOPs) have proved as alternative technologies to conventional processes. Indeed, EAOPs can often allow to treat wastewater containing toxic and POPs. Among them, electro-Fenton (EF) is considered particularly promising for the treatment of recalcitrant organics, since it presents various advantages, including high abatements for many organic pollutants, simplicity of equipment and operations, relatively low cost and low consumption of chemicals. Recently, the utilization of some natural heterogeneous catalysts was proposed in order to avoid some disadvantages of the conventional EF process. In this frame, in this work EF proc…

STUDY OF CAPACITIVE ELECTRODES FOR REVERSE ELECTRODIALYSIS PROCESSES

It has been calculated that the energy dissipated wherever the rivers get to the sea this corresponds to an amount of about 2 TW of power [1]. Recovering part of this energy could attenuate the dependency of our economic system from fossil fuels. The techniques conceived to exploit this blue energy are grouped within the family of the salinity gradient technologies, where pressure-retarded osmosis (PRO) and reverse electrodialysis (RED) are regarded as the most established technologies [2]. Nevertheless, their power is limited respectively by various factors including the kinetics of electrodes reactions. Conversely, the use of capacitive electrodes proposed by Brogioli in 2009, does not se…

Optimization of the selectivity for the electrocarboxylation of chloroacetonitrile to cyanoacetic acid

Inclusion complexes of triphenylphosphine derivatives and peracetylated-β-cyclodextrin in supercritical carbon dioxide

The supramolecular chemistry of peracetylated-β-CD (perAc-β-CD) as a host for triphenyphosphine derivatives has been studied in supercritical (scCO2) using UV absorption spectroscopy. It was found that the association constant in scCO2 at 40°C and 300 bar is 10 to 1000 times smaller compared to analogous systems in aqueous solvent. Studies of the thermodynamics of the inclusion process found an enthalpy of association of -30 kJ/mole and an entropy of -55 J/moleK. This difference with respect to water is attributed to the absence of the hydrophobic effect in scCO2 due to the much smaller polarity of scCO2 versus water. To further explore the effect of the solvent on the association constant,…

Effective Removal and Mineralization of 8-Hydroxyquinoline-5-sulfonic Acid through a Pressurized Electro-Fenton-like Process with Ni−Cu−Al Layered Double Hydroxide

Ni−Cu−Al layered double hydroxide (Ni−Cu−Al LDH) was proposed as an electro‐Fenton‐like catalyst for 8‐hydroxyquinoline‐5‐sulfonic acid (8‐HQS) removal in water. The properties of the prepared catalysts were characterized by using X‐ray, SEM and EDAX analyses. The effect of numerous operative parameters on the removal of 8‐HQS and total organic carbon (TOC) was studied. Very high level removal of both 8‐HQS and TOC (87 and 79 %, respectively) were obtained by using a pressurized electro‐Fenton‐like process (PrEFL‐LDH) at P=10 bars, using a Ti/IrO2‐Ta2O5 anode for 6 h. The process presented good performances in a large range of pH (3–10) and gave better removals of 8‐HQS and TOC with respect…

Electrochemical conversion of Carbon Dioxide: effect of operating parameters and of the reactor on the performances of the process.

Influence of the methodology of inoculation in the performance of air-breathing microbial fuel cells

n this work, four air-breathing microbial fuel cells (AB-MFC) were operated for 1 month in order to determine if the methodology of inoculation affects the steady-state performance of this type of MFCs. For this purpose, anaerobic and aerobic sludge were fed to two identical AB-MFCs without any external carbon source into a tight sealed environment during the first three days of start-up. For comparison purposes, other two AB-MFCs were operated mixing the initial sludge and an amount of sodium acetate as substrate. Results point out that the inoculation procedure does not affect the steady-state treatment capacity of the cells but it affects very seriously the production of electricity. Onl…

Modification of Polymers in Supercritical Carbon Dioxide

The interaction of scFluids and polymers are governed by the intermolecular forces between solvent-solvent, solvent-polymer segment, and polymer segment-segment pairs. Because of its symmetry, within reasonable pressure values, CO2 does not have a dipole moment, but it does have a quadrupole moment significant over a much shorter distance than dipolar interactions. The quadrupole moment and the Lewis acidity of CO2 imparts to the carbon dioxide the peculiarity to be a solvent for selected classes of polymers like perfluorinated polyacrylates, polysiloxanes and polyether-polycarbonate diblock copolymers [1–3].

Modeling of Electrochemical Process for Water Treatment Using Diamond Films

Crosslinking of poly(vinylpyrrolidone) activated by electrogenerated hydroxyl radicals: a first step towards a simple and cheap synthetic route of nanogel vectors

A facile electrosynthesis route for the preparation of polymer nanogels based on the in situ production of hydroxyl radicals is reported for the first time. Electro-Fenton process with continuous H2O2 electrogeneration and Fe2+ regeneration performs better than electro-oxidation with a boron-doped diamond or dimensionally stable anode for promoting crosslinking of poly(vinylpyrrolidone). Keywords: Electrogenerated hydroxyl radicals, BDD, DSA, Electro-Fenton, Polymer modification, Nanogel

A Gas Chromatographic Method to Measure Sorption of Supercritical Carbon Dioxide in Polymers

effect of the temperature on the electrochemical incineration of organic pollutants

Electrochemical Conversion of Dichloroacetic Acid to Chloroacetic Acid in Conventional Cell and in Two Microfluidic Reactors

The electrochemical conversion of dichloroacetic acid to chloracetic acid is investigated in conventional cells and in microreactors. Two different microreactors are used: the first is a filter press cell equipped with PTFE micrometric spacers, easy to assemble and disassemble and available for a large variety of electrodes and solvents; the second is made using an adhesive spacer, micromilling and press and could easily be developed on an industrial scale. The electrochemical synthesis is performed successfully in the microreactors equipped with a graphite cathode under proper operative conditions. The performance of the process strongly depends on the nature of the cathode and, for micror…

Special applications of reverse electrodialysis

Reverse electrodialysis (RED) is a process for direct electricity production from salinity gradients, based on the use of suitable exchange membranes. To develop the RED process on an applicative scale and to add value to the overall process, a key role is entrusted to the selection of electrodic system, redox species, and electrode materials. In particular, it was shown that a proper selection of redox processes allows the use of a RED cell for the wastewater treatment of organic and inorganic pollutants resistant to conventional biological methods and for the synthesis of chemicals without energy supply. The utilization of microbial reverse electrodialysis cells was also proposed to incre…

Peracetylated β‐cyclodextrin as solubilizer of arylphosphines in supercritical carbon dioxide

Abstract Effect of peracetylated β-cyclodextrin on the solubility of diphenyl(4-phenylphenyl)phosphine in supercritical carbon dioxide medium has been investigated. As shown by gravimetric measurements, the presence of cyclodextrin (CD) (1 equivalent) allows to increase the solubility of phosphine (P) in supercritical carbon dioxide (scCO 2 ) (40 °C, 35.2 MPa, nominal system density 0.89 g/mL). This solubility enhancement was attributed to host–guest interactions in scCO 2 as the P was recovered in the form of an inclusion complex. Furthermore, a diffuse reflectance spectroscopy study on the samples recovered after the experiments and on various CD/P solid mixtures obtained by co-grinding i…

Ring opening polymerization of cyclic esters with metal free catalysts

Polimerizzazione eterogenea di monomeri fluorurati in biossido di carbonio supercritico: sintesi di polivinilidenfluoruro

Electrochemical treatment of aqueous solutions of organic pollutants by electro-Fenton with natural heterogeneous catalysts under pressure using Ti/IrO2-Ta2O5 or BDD anodes

The treatment of toxic organic pollutants by electro-Fenton (EF) presents some drawbacks such as the necessity to work at low pH and the low solubility of oxygen in water contacted with air or oxygen at room pressure that results often in slow and relatively low abatements. Here, the coupled adoption of natural heterogeneous catalysts and of relatively high pressure was proposed in order to improve the performances of EF for the treatment of organic pollutants. Caffeic acid (CA) and 3-chlorophenol were used as model resistant organic pollutants. EF process was performed using both conventional homogeneous FeSO4 and natural heterogeneous catalysts (pyrite, chalcopyrite, Fe2O3 and Fe3O4) as i…

Supramolecular Chemistry of Cyclodextrins in Supercritical Carbon Dioxide: Spectroscopic Investigations

Interesterification of rapeseed oil catalyzed by tin octoate

The interesterification of rapeseed oil was performed for the first time by using tin octoate as Lewis acid homogeneous catalysts and methyl or ethyl acetate as acyl acceptors in a batch reactor, within the temperature range 393–483 K. The yields in fatty acid ethyl esters (FAEE) and triacetin (TA) after 20 h of reaction time increased from 8% and 2%–to 61% and 22%, respectively, when the reaction temperature increased from 423 to 483 K. An optimum value of 40 for the acyl acceptor to oil molar ratio was found to be necessary to match good fatty acid alkyl ester yields with high enough reaction rate. The rate of generation of esters was significantly higher when methyl acetate was used as a…

Premio di Laurea “Ametek Scientific Instruments”: Electrochemical Conversion of Carbon Dioxide to Formic Acid. Study of the Effect of the Operating Parameters

Electrochemical conversion of CO2 is considered one of the more appealing approaches to introduce renewable energy in the chemical and energy chain and to mitigate the greenhouse gases effect. In this work, the reduction of carbon dioxide was performed in undivided electrochemical cell to produce formic acid, which is one of the highest value-added chemicals and economically feasible for large-scale applications (1). It is well known that the main hurdle of the reduction of CO2 from water solution is the low CO2 solubility in water. In order to overcome this obstacle, a specific investigation on the effect of the CO2 pressure and other operating parameters at tin flat cathodes was carried o…

Two electochemical methodologies for the synthesis of cyanoacetic acid

Electrochemical treatment of real wastewater. Part 1: Effluents with low conductivity

Abstract The treatment of a real wastewater characterized by low conductivity was performed by anodic oxidation at boron doped diamond (BDD) in both conventional and microfluidic cells. The electrolyses carried out in conventional cells without supporting electrolyte were characterized by very high TOC removals but excessively high energetic consumptions and operating costs. The addition of sodium sulphate, as supporting electrolyte, allowed to strongly reduce the cell potentials and consequently the energetic consumptions and the operating costs. However, under various operating conditions, the addition of Na2SO4 caused a lower removal of the TOC. The best results in terms of both TOC remo…

Electrochemical incineration of oxalic acid at boron doped diamond anodes: Role of operative parameters

The electrochemical incineration of oxalic acid (OA) at boron doped diamond (BDD) anodes was investigated both theoretically and experimentally in order to find the influence of the operative parameters on the performances of the process. Polarization curves and chronoamperometric measurements indicate the probable occurrence of a direct electrochemical oxidation of OA at the surface of the BDD anode at low pH and of a hydroxyl radical-mediated reaction at high pH. When incineration electrolyses are performed at low pH with potentiostatic alimentation, a dramatic influence of the potential is observed. In amperostatic incineration, high CE are obtained when most part of the process was unde…

Development of an Electrochemical Process for the Simultaneous Treatment of Wastewater and the Conversion of Carbon Dioxide to Higher Value Products

Many researchers have shown that selected anodic processes allow effective treatment of a very large amount of wastewater contaminated by pollutants resistant to biological processes. In the meantime, various authors have also shown that carbon dioxide can be converted into higher value products, such as formic acid or synthesis gas, by cathodic reduction at suitable cathodes. These two processes present interesting economic potential that, however, still needs to be improved for further development at an industrial level. Herein, these two kinds of process are combined in the same cell to improve their economic feasibility. In particular, the anodic treatment of wastewater at a boron-doped…

Cathodic abatement of Cr(VI) in water by microbial reverse-electrodialysis cells

Abstract For the first time a microbial reverse electrodialysis cell (MRC) was used for the treatment of water contaminated by Cr(VI). It has been recently shown that both inorganic and organic pollutants can be removed by reverse electrodialysis processes (RED) using water with different salinity without the supply of electric energy. However, a high number of membrane pairs is usually necessary for the treatment of wastewater by RED. Here, it was showed that a lower number of membranes can be used by the utilization of a MRC (i.e., a RED cell with a biotic anode) for such purposes. Indeed, the abatement of Cr(VI), chosen as model pollutant, was successfully achieved by cathodic reduction …

Investigation of Dense Gas Sorption in Polymers by a Gas Chromatographic Method

Hydroformylation of 1-Octene in Supercritical Carbon Dioxide: Can Alkylation of Arylphosphines with tertButyl Groups Lead to Soluble and Active Catalytic Systems?

Abstract The possibility of increasing the solubility and activity of rhodium catalysts in the hydroformylation of 1-octene in supercritical carbon dioxide (scCO2) by attachment of tertbutyl (tBu) groups to the triarylphosphine ligand was investigated. The solubility of the parent and monoalkylated ligands in a mixture of gaseous components (CO2/CO/H2) was evaluated by visual observation in a view cell. In the case of triphenylphosphine, introduction of one tertbutyl group does not seem to affect the solubility of the phosphine. When the behaviour of (diphenyl)biphenylphosphine and (para-tertbutyldiphenyl)biphenylphosphine was compared a clear solubilising effect of the tBu group was observ…

Electrocarboxylation of benzyl chlorides at silver cathode at the preparative scale level

Abstract The electrocarboxylation of benzyl chlorides to the corresponding carboxylic acids performed at silver cathodes was investigated both theoretically and experimentally in order to find the influence of the operative parameters on the selectivity and on the Faradic efficiency of the process. Theoretical considerations were confirmed by the electrocarboxylation of 1-phenyl-1-chloroethane performed in undivided cells equipped with sacrificial anodes both in a bench-scale electrochemical batch reactor and in a continuous batch recirculation reaction system equipped with a parallel plate electrochemical cell. Selectivity and Faradic yields higher than 80% and 70%, respectively, were obta…

Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one-pot route for the preparation of controlled delivery systems

Electrochemical conversion of pressurized CO2 at simple silver-based cathodes in undivided cells: study of the effect of pressure and other operative parameters

Abstract Electrochemical reduction of pressurized CO2 is proposed as an interesting approach to overcome the main hurdle of the CO2 electrochemical conversion in aqueous solution, its low solubility (ca. 0.033 M), and to achieve good faradaic efficiency in CO using simple sheet silver cathodes and undivided cells, thus lowering the overall costs of the process. The effect on the process of CO2 pressure (1–30 bar), current density, nature of the supporting electrolyte and other operative conditions, such as the surface of the cathode or the mixing rate, was studied to enhance the production of CO. It was shown that pressurized conditions allow to improve drastically the current efficiency o…

Electrochemical treatment of organic pollutants in macro and micro reactors

Electrochemical treatment of real wastewater with low or high conductivity

In the last years, many efforts have been devoted to the development of electrochemical processes for the effective treatment of wastewater contaminated by organic pollutants resistant to conventional biological processes and/or toxic for microorganisms [1–5]. It was shown that some electrochemical approaches, including the direct anodic oxidation at suitable anodes such as boron-doped diamond (BDD) and/or electro-Fenton (EF) at suitable operating conditions and cells [1–6] can allow to treat effectively a very large number of organic pollutants. However, most of the investigations were performed using synthetic wastewater. Hence, it is now mandatory to study the problems connected to the p…

Abatement of AO7 in a divided microbial fuel cells by sequential cathodic and anodic treatment powered by different microorganisms

Abstract Microbial fuel cells (MFCs) can allow the treatment of organic pollutants resistant to conventional biological processes by electro-Fenton (EF) process performed in the cathodic compartment. However, EF usually results in a partial mineralization of pollutants. Here, we have studied the possible treatment of such organics in a MFC by a sequential cathodic and anodic treatment. In particular, the treatment of an aqueous solution of Acid Orange (AO7), a largely used azoic dye resistant to conventional biological processes, was performed in the cathodic compartment of a divided MFC by EF. The process allowed the total removal of the color and the partial removal of the TOC, due mainly…

Utilization of dense carbon dioxide as an inert solvent for chemical syntheses

ABATEMENT OF ACID ORANGE 7 IN WATER BY DIFFERENT ELECTROCHEMICAL APPROACHES

Very large amounts of synthetic dyes are discharged in the environment from industrial effluents [1]. Due to their large-scale production and extensive application, synthetic dyes can cause considerable nonaesthetic pollution and are serious health-risk factors [2]. Dyes are commonly classified from their chromophore group. The majority of these compounds consumed at industrial scale are azo (–N=N–) derivatives that represent more than 50% of the all dyes used in textile industries, although antraquinone, indigoide, triphenylmethyl, xanthene, sulphur and phtalocyanine derivatives are frequently utilized [3]. Since dyes usually present high stability under sunlight and resistance to microbia…

Study of Atrp Process for the Grafting of Vinyl Monomers on PVC and PVDF

STUDY OF ATRP PROCESS FOR THE GRAFTING OF VINYL MONOMERS ON PVC AND PVDF Sonia Lanzalaco, Onofrio Scialdone, Alessandro Galia, Rosalia Mauro, Flavia Lazzano Dipartimento di Ingegneria Chimica, Gestionale, Informatica, Meccanica, Viale delle Scienze, Palermo e-mail: sonia.lanzalaco@unipa.it ATRP (atom transfer radical polymerization) has been recently used to prepare graft copolymers with regularly-spaced polymer chains from polymeric macroinitiators that have pendant chemical groups containing radically transferable halogen atoms [1]. The halogen atom serves as initiation site for the polymerization of side chains. Furthermore, Matyjaszewsky and Gennaro showed that an externally applied ele…

Influence of operative parameters on the electroChemical incineration of oxalic acid at boron-doped diamond electrodes

Electrochemical processes in macro and microfluidic cells for the abatement of chloroacetic acid from water

Abstract The remediation of solutions contaminated with monochloroacetic acid (CAA), which is one of the most resistant haloacetic acids (HAAs) to chemical degradation, dramatically depends on the adopted electrochemical approach: (i) CAA is only poorly oxidized either by homogeneous hydroxyl radical in electro-Fenton (EF), electrogenerated active chlorine or electro-oxidation on Pt anode; (ii) it is moderately abated by direct reduction on silver or compact graphite cathodes (from 30% in macro cells to 60% in the microfluidic devices); (iii) it is quantitatively removed by direct electro-oxidation on a boron-doped diamond (BDD) anode. The use of a microreactor enables operation in the abse…

Synthesis of cyanoacetic acid by carbon dioxide and electrogenerated acetonitrile anion in undivided cells equipped with sacrificial anodes

The electrochemical synthesis of cyanoacetic acid was performed by cathodic reduction of tetraalkylammonium salts (R4NX) in acetonitrile in undivided cells equipped with sacrificial anodes with concomitant or subsequent addition of carbon dioxide. These syntheses avoid the use of dangerous reagents, yield cyanoacetic acid in moderate faradic yields and confirm that the cathodic reduction of tetraalkylammonium salts in the presence of acetonitrile leads to the formation of the anion CNCH2-.

Heterogeneous polymerization of vinylidene fluoride in scCO2 in the presence of perfluoropolyether surfactants

Particle Forming polymerization of 1-Vinyl-2-Pyrrolidone in SCCO2 in the Presence of Ibuprofen: a One Pot Process for the Preparation of Controlled Release Systems

Asymmetric hydrogenation of ethyl pyruvate over aqueous dispersed Pt nanoparticles stabilized by a cinchonidine-functionalized β-cyclodextrin

International audience; Cinchonidine-functionalized &beta;-cyclodextrin was used as stabilizing agent for platinum nanoparticles dispersed in water, but also as chiral modifier for the asymmetric hydrogenation of ethyl pyruvate at 30 °C under 40 bar of hydrogen. This functionalized cyclodextrin allowed getting more stable, more catalytically active and also more enantioselective Pt nanoparticles compared to control catalytic systems. NMR and MALDI-MS analyses clearly showed the reduction of the vinyl group of the cinchonidine graft during the nanoparticles preparation. Under hydrogen pressure, the hydrogenation of the quinolinic moiety was also proven and can be responsible for the difficul…

Preparation of drug-polymer composites by polymerization in supercritical carbon dioxide: a new method to increase the dissolution rate of bioactive compounds with low aqueous solubility

ABATEMENT OF POLLUTANTS IN AQUEOUS SOLUTIONS BY REVERSE ELECTRODIALYSIS PROCESSES

Electrochemistry-based technologies are very promising methods for treating wastewaters containing organic and inorganic pollutants that are either resistant to biological processes or toxic for microorganisms [1]. On the other hand, in the reverse electrodialysis (RED), the electrical energy is directly extracted from chemical potential gradients arising from salinity differences [2], especially between brine solution and sea water. RED can be potentially used for the simultaneous generation of electrical energy and the treatment of waters contaminated by recalcitrant pollutants. The advantages of using the RED process for such dual purpose are: the utilization of a green reagent such as t…

Electrochemical treatment of aqueous solutions containing one or many organic pollutants at boron doped diamond anodes. Theoretical modeling and experimental data

The electrochemical oxidation of organics in water at boron doped diamonds (BDD) was experimentally investigated with the aim to discuss the correlations among the conversion of the pollutants and the instantaneous current efficiency ICE with the operative conditions. A simple theoretical model previously developed for the oxidation of oxalic acid accounting for the cases of mass transfer control, oxidation reaction control and mixed kinetic regimes was adopted and extended to challenge its predictive capability in the case of organics of different nature and in systems with more pollutants. A quite good agreement, between theoretical predictions and experimental data pertaining to the elec…

Abatement of 1,1,2,2-tetrachloroethane in water by reduction at silver cathode and oxidation at boron doped diamond anode in micro reactors

The treatment of aqueous solutions of 1,1,2,2-tetrachloroethane was performed by anodic oxidation at boron doped diamond (BDD), cathodic reduction at silver and coupled processes. Experiments were performed in macro and micro reactors with an interelectrode distance lower than 100. μm. Drastically higher abatements of the chlorinated compound and current efficiencies were obtained in microdevices that, furthermore, allowed to perform the electrolyses with low cell voltages in the absence of supporting electrolyte. When reduction and oxidation processes were carried out simultaneously in the microreactor, a higher abatement of pollutants was obtained with the same amount of the passed charge…

Sintesi del coenzima Q10

Liquefazione idrotermica di fanghi di depurazione dalle acque reflue in presenza di acido formico come co-solvente

A causa del progressivo impoverimento delle risorse di combustibili fossili e dell’impatto negativo che il loro utilizzo ha sull'ambiente, la produzione di carburanti da fonti alternative, come le biomasse, ha ricevuto negli ultimi anni una notevole e crescente attenzione. Questo studio è incentrato sulla liquefazione idrotermica (HTL) dei fanghi provenienti dalla depurazione delle acque reflue civili. Tale tipo di biomassa oltre ad avere un alto tasso di umidità, ha un elevato contenuto organico e per essere smaltita è necessario che gli impianti di depurazione investano un ingente capitale [1]. L’HTL tradizionale prevede l’utilizzo dell’acqua, in parte già contenuta nella biomassa, come s…

Preparation of pH sensitive poly(vinilydenefluoride) porous membranes by grafting of acrylic acid assisted by supercritical carbon dioxide

Free radical grafting of acrylic acid (AA) on poly(vinilydenefluoride) (PVDF) porous membranes was studied at 65°C using supercritical carbon dioxide (scCO 2) as a solvent and delivery agent. The process was initiated by the thermal decomposition of benzoylperoxide (BPO). Spectroscopic analyses confirmed the presence of poly(AA) chains linked to treated membranes. The mass fraction of grafted AA increased with grafting time and BPO concentration while it decreased when the density of the fluid phase was enhanced. A not-monotonic trend was obtained when the effect of the initial AA concentration was studied. The grafting process was accompanied by a reduction of the crystallinity of the PVDF…

Electrochemical processes for the treatment of dichloroethane in water solutions

ELECTROCHEMICAL TREATMENT OF WASTE WATERS CONTAMINATED BY ORGANIC POLLUTANTS: A LOOK ON SOME NEW APPROACHES

Recent researches have demonstrated that electrochemical methods offer an attractive alternative to traditional routes for treating wastewaters containing toxic or/and refractory organic pollutants. These methods use a clean reagent, as the electron, very mild operative conditions (ambient temperature and pressure) and can be run with limited operative costs. Despite of the above mentioned advantages, electrochemical processes present some important disadvantages such as: • the cost of some electrodic materials such as silver (for reduction processes) and boron doped diamond (for oxidation ones). On the other hand, the cost of silver based electrodic materials can be considerably lowered by…

Gamma radiation induced maleation of polypropylene using supercritical CO 2 : preliminary results

Abstract The charging of maleic anhydride (MA) and dicumyl peroxide (DCP) into polypropylene matrices has been carried out by CO2 in supercritical conditions. The grafting of MA into polymer chains was done through gamma irradiation in CO2 atmosphere (0.1 MPa, 25°C). The grafting was successful and the amount of grafted anhydride was dependent on the amount of MA and DCP charged into the polypropylene matrix. The presence of grafted succinic anhydride was shown by FT-IR spectroscopy and its amount was determined through a calibration curve derived from standard samples. The effect of swelling due to supercritical CO2, maleic anhydride grafting and gamma irradiation on the molecular structur…

Reverse electrodialysis performed at pilot plant scale: Evaluation of redox processes and simultaneous generation of electric energy and treatment of wastewater

Abstract This paper describes the experimental campaign carried out with a reverse electrodialysis (RED) demonstration plant (Marsala, Italy) with the main aims of: (i) evaluating the effect of various operating parameters, including the redox processes, on the system performances; (ii) using the plant for the simultaneous generation of electric energy and treatment of wastewater. The prototype (44 × 44 cm2, 500 cell pairs) was tested using both real (brackish water and brine) and artificial solutions. Tests with two different electrode rinse solutions (with or without iron redox couples) were performed. In agreement with the data obtained in the laboratory, the presence of iron ions contri…

Hydrothermal liquefaction of waste biomass in stirred reactors: One step forward to the integral valorization of municipal sludge

Abstract Hydrothermal liquefaction (HTL) of municipal sludge (MS) was performed at 350 °C for 30 min (subcritical water) and at 400 °C for 0 min (supercritical water) at fixed kinetic severity (LogR0 = 8.9) in static and stirred batch reactors to study the effect of the flow regime on the energy recovery (ER) of the process and on the quality of the products. With adopted experimental procedures it was possible to reduce to less than 10% the yield of lost organic compounds, termed volatiles (VT), and to collect and quantify a liquid hydrocarbon fraction (HC) separated from the biocrude (BC). The highest value of the HC yield, 25% w/w, was obtained in supercritical conditions. The C content …

Cathodic reduction of hexavalent chromium coupled with electricity generation achieved by reverse-electrodialysis processes using salinity gradients

Abstract A new approach for the simultaneous generation of electric energy and the treatment of waters contaminated by recalcitrant pollutants using salinity gradients was proposed. Reverse electrodialysis allows for the generation of electric energy from salinity gradients. Indeed, the utilization of different salt concentrations gives a potential difference between the electrodes which allows the generation of electric energy by using suitable electrolytes and an external circuit. The simultaneous generation of electric energy and the treatment of waters contaminated by Cr(VI) was successfully achieved for the first time by reverse electrodialysis processes using salinity gradients and pr…

Electrochemical oxidation of carboxylic acids at boron doped diamonds

Melt phase ring opening polymrization of lactide and glycolide assisted by supercritical carbon dioxide

Electrochemical treatment of wastewater containing NaCl. Methods to increase the removal of organic pollutants and minimize the formation of toxic by-products

In many cases, wastewater can contain both organic pollutants and NaCl. Electrochemical methods allow to treat very effectively organic pollutants in the presence of NaCl. However, the utilization on an applicative scale of this route is limited by the fact that usually the high removals of organics is coupled with the generation of significant amounts of chlorinated by-products. The role of several operative parameters on the performances of the process was systematically evaluated using phenol as a model organic pollutant. It was shown that the removal of phenol and TOC and the generation of many by-products including chlorophenols, chloroacetic acids, chlorate and perchlorate dramaticall…

Functional (per)fluoropolyethers as surfactant for CO2 polymerization

Idroformilazione dell'1-ottene in scCO2 con sistemi catalitici a base di rh e fosfine funzionalizzate non-fluorurate

Catalytic hydrothermal liquefaction of municipal sludge in subcritical water

In the last decades, the dwindling of the fossil sources of energy coupled with the growth of energy demand and of waste production prompted the research in developing novel industrial technologies for renewable energy production and waste valorization. Hydrothermal liquefaction (HTL) is a good alternative to transform wet biomasses as microalgae, macroalgae, agricultural residues, food waste, and municipal sludge (MS) into value-added products with high efficiency and decreasing the amounts that has to be disposed of. HTL takes place in an aqueous environment, without the energy cost of drying the biomass, at 300-400°C and pressure of 10-40 MPa [1,2]. At these operative conditions, an inte…