Environmentally Friendly Photocatalytic Oxidation of Aromatic Alcohol to Aldehyde in Aqueous Suspension of Brookite TiO(2)

WOS: 000260509000008

Nature of Interactions at the Interface of Two Water-Saturated Commercial TiO2 Polymorphs

Two commercial TiO2 samples, a 100% anatase and a 100% rutile, were used for the fast field cycling NMR experiments. The results showed a different behavior between the different samples. In particular, water molecules were unbonded to the solid surface for the rutile sample, whereas they appeared to chemically interact with the surface through H-bond formation with the anatase sample. The above findings accord with the generally lower activity of rutile with respect to anatase reported in literature for photocatalytic oxidation reactions in water. The difficulty of water to interact with rutile surface, indeed, could hinder the formation of OH radicals, which are the most important oxidant…

Photocatalytic oxidation of aromatic alcohols to aldehydes in aqueous suspension of home prepared titanium dioxide: 2. Intrinsic and surface features of catalysts

Some intrinsic electronic properties of home prepared (HP) TiO2 catalysts were investigated by diffuse reflectance spectroscopy and quasi-Fermi level measurements. These powders were used for carrying out the photocatalytic oxidation of benzyl alcohol to benzaldehyde and CO2 in water; the selectivity for aldehyde formation was enhanced by the addition of small amounts of ethanol, a typical hole trap. The values of band gap, valence band and conduction band edges are almost identical for all the HP samples in which anatase phase is predominant, whereas appreciable differences can be noticed for an HP sample containing high amount of rutile phase. A comparative ATR-FTIR study of the HP cataly…

TiO2 thin films: preparation, characterisation and their photocatalytic activity

Photocatalytic Selective Oxidation of 5-(Hydroxymethyl)-2-furaldehyde to 2,5-Furandicarbaldehyde in Water by Using Anatase, Rutile, and Brookite TiO2 Nanoparticles

5-(Hydroxymethyl)-2-furaldehyde (HMF) was selectively oxidized to 2,5-furandicarbaldehyde (FDC) in; aqueous medium by using home prepared (HP) anatase, rutile, and brookite TiO2 nanoparticles. HP samples were prepared via a sol-gel method by using TiCl4 as the TiO2 precursor. Commercial TiO2 catalysts were also used for, comparison. All samples were characterized by BET specific surface area, XRD, TGA, and SEM, and the reactivity results showed that HP catalysts are predominantly amorphous and give rise to selectivities toward FDC more than twice that of commercial and well crystallized catalysts.

Oxidation of aromatic alcohols in irradiated aqueous suspensions of commercial and home-prepared rutile TiO(2): a selectivity study.

WOS: 000256241700021

Alcohol-Selective Oxidation in Water under Mild Conditions via a Novel Approach to Hybrid Composite Photocatalysts

Abstract The oxidation of alcohols to carbonyl compounds in a clean fashion (i.e., with water as a solvent or under solvent‐free conditions, and using O2 or H2O2 as the primary oxidant) is the subject of considerable research efforts. A new approach for the selective oxidation of soluble aromatic alcohols in water under mild conditions via a novel composite photocatalyst has been developed. The catalyst is synthesized by grafting 4‐(4‐(4‐hydroxyphenylimino)cyclohexa‐2,5dienylideneamino)phenol and silver nanoparticles onto the surface of moderately crystalline titanium dioxide. The titanium dioxide‐based composite was first extensively characterized and then employed in the catalytic oxidati…

Polymer leaf of expanded material coated with titanium dioxide exhibiting photocatalytic activity, container and package for foodstuffs obtained from said polymer leaf

Adsorption and Photocatalytic Degradation of Acetonitrile on TiO2: FTIR and Kinetic Studies

Photocatalytic and photoelectrocatalytic H2 evolution combined with valuable furfural production

In this work the photocatalytic (PC) and photoelectrocatalytic (PEC) reforming of furfuryl alcohol (FA) under environmental friendly conditions was investigated. Both H2 evolution and partial oxidation to furfuraldehyde were followed. For the first time TiO2 based photocatalysts were studied and the photocatalytic activity of home prepared photocatalysts was compared with that of commercial ones under both UVA and simulated solar irradiation. PEC tests were performed by using home prepared TiO2 nanotubes (TiO2 NTs) as photoanode and Pt free Ni foam as cathode to improve the Hydrogen Evolution Reaction (HER). Both the partial FA oxidation reaction rate and H2 evolution rate were normalized f…

Ossidazione mediante fotocatalisi e ozonizzazione dello ione ossalato in soluzioni acquose contenenti biossido di titanio

Selective heterogeneous photocatalysis: examples of green photosyntheses

Degradation of Drugs in Aqueous Medium: Photocatalytic oxidation of Lincomycin

Photocatalytic selective oxidation of 4-methoxybenzyl alcohol to aldehyde in aqueous suspension of home-prepared TiO2 catalyst

The photocatalytic oxidation of 4-methoxy-benzyl alcohol to p-anisaldehyde (PAA) was performed in water with organic-free suspensions of home-prepared and commercial titanium dioxide (TiO2) catalysts. The nanostructured TiO2 samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl4), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4-methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5 % mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116 %. A comparison with two commercial TiO2 samples showed that all the home-prepared catalysts …

Special needs and characteristic features of (photo)catalytic reactors with a review of the proposed Solutions

Abstract In the present chapter, the analogies between photocatalytic systems and the systems where the more common thermally activated reactions take place are highlighted. The objective is to propose a unified approach for the analysis and the design, which, however, must take into account how and why photocatalytic reactors differ from reactors with thermal reactions. The necessity of absorbing photons to activate the photocatalytic process adds complexity to the system, but some approaches are presented to simplify the problems and make easier their solution.

Titania Photocatalysts for Selective Oxidations in Water

Heterogeneous photocatalysis by polycrystalline semiconductor oxides is an unconventional technology that has been mainly applied for the degradation of organic and inorganic pollutants in both the vapor and liquid phase. The application of photocatalysis in synthetic routes has also been researched in recent years, demonstrating its viability as an alternative route in organic chemistry. This work illustrates the main findings in the application of heterogeneous photocatalysis to the oxidation of organic compounds dissolved in water, free of any organic co-solvent. Two main aspects of the oxidative process have been studied: the first one is the partial oxidation of various mono-substitute…

Strategy assessment to mediate between purification targets and bromate production during purification of bromide containing water by means of photocatalytic ozonation

Adsorption and photocatalytic degradation of acetonitrile: FT-IR investigation

Abstract The photocatalytic degradation of acetonitrile was carried out in liquid–solid regime in a batch reactor by using two types of commercial TiO 2 powders (Merck and Degussa P25) as photocatalysts. The concentration of acetonitrile and non-purgeable organic carbon (NPOC) were monitored. The initial rate of acetonitrile conversion was found higher on TiO 2 Merck than on TiO 2 P25. FT-IR spectroscopy was used to investigate the molecular features of the adsorption and photo-oxidation of acetonitrile on the two TiO 2 powders in a fully surface hydrated form. Acetonitrile was found adsorbed on Ti 4+ surface ions and hydroxyl groups for both types of TiO 2 . This interaction appeared fully…

Photoelectrocatalytic Selective Synthesis of p-Anisaldehyde in Water by TiO2 Supported on Ti Anodes

Photocatalytic oxidation of toluene on irradiated TiO2: comparison of degradation performance in humidified air, in water and in water containing a zwitterionic surfactant

Photocatalytic degradation of toluene was carried out both in gas–solid and in liquid–solid regime by using polycrystalline samples of TiO2 Merck and TiO2 Degussa P25. For the gas–solid regime two types of continuous photoreactor were used, a fixed bed one of cylindrical shape and a Carberry type photoreactor, both irradiated by near-UV light. The inlet reacting mixture consisted of air containing toluene and water vapours. The influence of the gas flow rate and the presence of water vapour on the photocatalytic process was investigated. CO2 and benzaldehyde were the toluene degradation products detected in the gas phase by using TiO2 Merck. In the presence of water vapour this catalyst exh…

Production of Aldehydes by Oxidation in Aqueous Medium with Selective Recovery of the Product by Means of Pervaporation

Heterogeneous Photocatalysis for Selective Formation of High-Value-Added Molecules: Some Chemical and Engineering Aspects

This review deals with the parameters that influence heterogeneous photocatalysis (PC) for selective synthesis of high-value chemicals by itself or in combination with other technologies. In particular, the parameters related to the photocatalysts, such as crystallinity degree, type of polymorph, surface acid-base properties, exposure of particular crystalline facets, coupling of different semiconductors, position of the valence and conduction band edge, addition of doping agents, and those related to the reaction system, such as setup configuration and reactor geometry, type of solvent, type and amount of photocatalyst, affecting the selectivity toward specific products are described and d…

Photocatalytic degradation of paraquat Combined with a genotoxicity Study of the Intermediate Products

Photocatalytic membrane reactors

Combination of different advanced oxidation processes and activated carbons for treatment of salt water

Bilgewater is a corrosive polluted effluent from the bilge of ships that mainly originates from seawater infiltration and leakage of engine oil and fuel. Each year, thousands tons of hydrocarbons from bilge are discharged at sea. In order to prevent hydrocarbon discharge at sea from the bilge of ships, the Internation Maritime Organization (IMO) enacted the MARPOL 73/78 convention in which effluents are now limited to those with maximun oil content of 15 ppmv.

Azo-Dyes Photocatalytic Degradation in Aqueous Suspension of TiO2 Under Solar Irradiation

Abstract The photodegradation of two common and very stable azo-dyes, i.e. methyl-orange (C14H14N3SO3Na) and orange II (C16H11N2SO4Na), is reported. The photocatalytic oxidation was carried out in aqueous suspensions of polycrystalline TiO2 irradiated by sunlight. Compound parabolic collectors, installed at the “Plataforma Solar de Almeria” (PSA, Spain) were used as the photoreactors and two identical reacting systems allowed to perform photoreactivity runs for the two dyes at the same time and under the same irradiation conditions. The disappearance of colour and substrates together with the abatement of total organic carbon content was monitored. The main sulfonate-containing intermediate…

Optical Properties and Quantum Yields Determination in Photocatalytic Suspensions

Ferulic Acid Oxidation Through Visible Light Induced TiO2 Photocatalysis

Kinetics of 4-Methoxybenzyl Alcohol Oxidation in Aqueous Solution in a Fixed Bed Photocatalytic Reactor

WOS: 000280384800004

Process for the production of bromine

A process for the preparation of molecular bromine, by means of advanced oxidation processes or their combination is disclosed

Photocatalytic partial oxidation of phenenthrene in green organic solvents

Heterogeneous photocatalytic aqueous succinic acid formation from maleic acid reduction

This study reports the anaerobic reduction of maleic acid to succinic acid in aqueous dispersion of different TiO2 based photocatalysts. Some home prepared and commercial solids containing different polymorphic phases of TiO2 and loaded with Pt and Ru were compared at different acidic pHs. The aim of the work was to verify the feasibility of the process and to determine the best samples and the optimal experimental conditions of the reaction. The best selectivity towards succinic acid was 23.2 % at 70 % of maleic acid conversion. Fumaric acid was also formed as another high added value compound, and its quantity was related to the experimental conditions and the photocatalyst used.

Graphite-supported TiO2 for 4-nitrophenol degradation in a photoelectrocatalytic reactor

WOS: 000274769500044

Photocatalytic degradation of organic pollutants by using polycrystalline TiO2: case studies for environment remediation

A Dialysis Photocatalytic Reactor for the Green Production of Vanillin

In the present work, dialysis was used to recover vanillin while being produced by partial photocatalytic oxidation of ferulic acid in an aqueous solution at ambient temperature. The relatively high value of the permeate flux through a dense polyether-block amide membrane allowed continuously extracting vanillin from the reacting solution, thus avoiding its successive oxidation. The rate of vanillin formation was improved, compared to other reactor configurations, because intermediate compounds permeated from the reacting solution and did not hinder the reaction, while ferulic acid permeated in the opposite direction to partially replenish the reactor with the substrate. The photocatalytic …

Photodegradation of lincomycin in aqueous solutions

The role of H2O in the photocatalytic oxidation of toluene in vapour phase on anatase TiO2 catalyst

Abstract Photocatalytic oxidation of toluene has been carried out in a gas–solid regime by using polycrystalline anatase TiO2 in a fixed-bed continuous reactor. Air containing toluene and water vapours in various molar ratios was fed to the photoreactor irradiated by a medium pressure Hg lamp. Toluene was mainly photo-oxidised to benzaldehyde, and small amount of benzene, benzyl alcohol and traces of benzoic acid and phenol were also detected. In the presence of water, no decrease of photoreactivity was observed at steady-state conditions. By removing water vapour from the feed, the conversion of toluene to benzaldehyde was almost completely inhibited, and an irreversible deactivation of th…

Photocatalytic oxidation of nitrobenzene and phenylamine: Pathways and kinetics

WOS: 000245150800018

Photocatalytic degradation of 4-nitrophenol in a continuous reactor containing titanium dioxide supported on glass beads

WOS: 000258975200009

Photocatalysis in dimethyl carbonate green solvent: degradation and partial oxidation of phenanthrene on supported TiO2

Dimethyl carbonate (DMC) is here proposed – for the first time – as a green organic solvent for photocatalytic synthesis. In this work, the photocatalytic partial oxidation of phenanthrene in dimethyl carbonate (DMC) by using anatase TiO2 as the photocatalyst is described as paradigmatic example of a green synthetic process starting from polycyclic aromatic hydrocarbons (PAHs). For comparison, the same reaction carried out also in ethanol, 1-propanol or 2-propanol is reported. The use of DMC as the solvent allowed us to achieve 19% and 23% selectivity towards 9-fluorenone and 6H-benzo[c]chromen- 6-one, respectively. The proposed approach may represent both a new green synthetic process and …

Sintesi di Piperonale tramite fotocatalisi eterogenea in condizioni green

Process intensification in a photocatalytic membrane reactor: Analysis of the techniques to integrate reaction and separation

Abstract Different methods to integrate reaction and separation in a membrane reactor are studied in the present work, with the aim being to highlight the pros and cons of the different alternatives and the effects of the intervening parameters. The coupling of the two processes can take place inside a single apparatus or using separate units. If a single apparatus is utilized, the coupling is more direct, but separate units offer higher degrees of freedom for the design with more opportunities to optimize the system without constraints. However, when using separate units, the integration of the two unit operations depends largely on the parameters intervening in the coupling procedure. The…

Photocatalytic inactivation of Legionella Pneumophila and aerobic bacteria consortium in water over TiO2/SiO2 fibres in a continuous reactor

A continuous photoreactor, working in a total recycle mode and irradiated by a low-pressure Hg lamp, has been used to study the bactericidal effect of a photocatalyst, formed by TiO2 embedded in SiO2 fibres, on Legionella pneumophila and a consortium of common gram-negative aerobic bacteria: (Escherichia coli, Klebsiella sp., Pseudomona sp. and Proteus sp.) in water. The kinetic modeling of the inactivation process, carried out with the measured values of viable bacteria concentration at the outlet of photoreactor, evidenced that for each pass inside the photoreactor the ratio between the outlet and inlet cell concentrations was of order of 0.01 for the inactivation of L. pneumophila. For t…

Photocatalytic ozonation: Maximization of the reaction rate and control of undesired by-products

Abstract In the so-called photocatalytic ozonation (PO) synergistic effects between photocatalysis and ozonation enhance the rate of oxidation of organic compounds, therefore this integrated process is very promising for use in water treatment. In the present work, it is demonstrated that the improvement that can be obtained by the integrated process in comparison with the uncoupled processes depends on the relative weight between photocatalysis and ozonation. In this respect, it has been found that a relatively low rate of photocatalysis (0.3 times the rate of ozonation) is sufficient to get the highest synergy and to maximize the performances in the oxidation of formate, the adopted model…

Synthesis and Characterization of TiO2 Based Inorganic-Organic Hybrid Photocatalysts for Enhancing the Selective Formation of 4-Methoxy-benzaldehyde from 4-Methoxybenzyl alcohol

The oxidation of alcohols to carbonyl compounds in a clean fashion (i.e., with water as a solvent or under solvent-free conditions, and using O2 or H2O2 as the primary oxidant) is the subject of considerable research efforts. A new approach for the selective oxidation of soluble aromatic alcohols in water under mild conditions via a novel composite photocatalyst has been developed. The catalyst is synthesized by grafting 4-(4-(4- hydroxyphenylimino)cyclohexa-2,5dienylideneamino)phenol and silver nanoparticles onto the surface of moderately crystalline titanium dioxide. The titanium dioxide-based composite was first extensively characterized and then employed in the catalytic oxidation of 4-…

Comparison of Different Photocatalytic Systems for Acetonitrile Degradation in Gas-Solid Regime

Water Depollution by Advanced Oxidation Technologies

This chapter deals with water treatments by advanced oxidation processes (AOPs) based on chemical and photochemical reactions. The most used processes are described, and for each of them, the main reaction mechanisms, principles, advantages, drawbacks, performances and formation of by-products, coupled with technologies and their applications to waters and wastewater depollution, have been analysed, supporting the main results of studies published in the pertinent literature.

ChemInform Abstract: Membranes for Photocatalysis in Water and Wastewater Treatment

Abstract: The chapter reports the basic principles of heterogeneous photocatalysis together with a brief presentation of the types of membranes and membrane operations most widely used in this type of application. Coupling the two technologies with the aim of obtaining synergistic effects for conversion in liquid–solid systems is discussed and the relevant papers together with some case studies in pollutants abatement and reaction of synthesis are highlighted.

Selective photocatalytic oxidation of 4-substituted aromatic alcohols in water with rutile TiO2 prepared at room temperature

WOS: 000264978500012

Preparation, Characterization of rutile obtained by hydrolisis of TiCl4

Photocatalytic oxidation of gaseous toluene on polycrystalline TiO2: FT-IR investigation of surface reactivity of different types of catalysts

Commercial TiO 2 Merck and TiO 2 Degussa P25 powders were employed as the catalysts for the photo-oxidation of toluene. By using TiO 2 Merck benzaldehyde was found in gas phase as the main product of the toluene partial oxidation. After an initial transient period, this catalyst exhibited a high stability in the presence of water vapour in the gaseous mixture, whereas the photoproduction of benzaldehyde sharply decreases after removal of H 2 O from the feed IR spectra of the used catalyst revealed that in the absence of water vapour benzaldehyde is molecularly held on the catalyst surface. This feature was confirmed by co-adsorbing benzaldehyde and water on the fresh catalyst. By contrast, …

Heterogeneous photocatalytic degradation of pharmaceuticals in water by using polycrystalline TiO2 and a nanofiltration membrane reactor

Abstract A study of the photodegradation of different pharmaceuticals [furosemide, ranitidine (hydrochloride), ofloxacine, phenazone, naproxen, carbamazepine and clofibric acid] in aqueous medium at various pHs by using a batch photoreactor and a photocatalytic membrane reactor working in recirculation regime was carried out. Polycrystalline TiO 2 was used as the photocatalyst, and different membranes (NTR 7410, PAN GKSS HV3/T, N 30 F, NF PES 10) were tested. A different adsorption of the substrates onto the catalyst surface was observed owing to the hydrophilic/hydrophobic character of the catalyst, depending on the pH. The photodegradation of the seven molecules in the batch reactor was s…

A quantitative method of photoadsorption determination for irradiated catalyst in liquid–solid system

WOS: 000266963000002

Film di TiO2 da idrolisi di TiCl4: preparazione, caratterizzazione e fotoattività

TiO2-H2O Interactions by Fast Field Cycling (FFC) NMR Relaxometry

Synthesis of vanillin in water by TiO2 photocatalysis

Abstract The photoproduction of vanillin is studied in aqueous medium starting from trans-ferulic acid, isoeugenol, eugenol or vanillyl alcohol by using both commercial and home prepared TiO2 samples as photocatalysts and batch Pyrex photoreactors. The photo-oxidation at room temperature of these compounds produces vanillin with a selectivity ranging from 1.4 to 21 mol% with respect to the converted substrate. An investigation on the intermediates was performed in the case of trans-ferulic acid; for this substrate the most important intermediates were homovanillic acid, vanillyl mandelic acid, trans-caffeic acid, formic acid, acetic acid, and oxalic acid. The carbon mass balance, including …

Preparazione di TiO2 nanostrutturato a partire da TiCl4.

Telloruro di Cadmio: Eldorado del fotovoltaico o insidia ambientale?

Photocatalytic ozonation for a sustainable aquaculture: A long-term test in a seawater aquarium

Abstract A long-term test at a laboratory scale with a closed system (a coral reef aquarium) has been carried out to study the potentialities of photocatalytic ozonation and photocatalysis for the removal of noxious organic compounds in recirculating systems (aquaria and recirculating aquaculture systems) working with a minimum make up of new water. Attention has been focused not only on the depuration capabilities but also on possible negative phenomena, some of which could become apparent only at long times. After having tuned the system by setting appropriate operating conditions and procedures, positive results were obtained. In particular, it was observed that the alternation of photoc…

Coupling of membrane and photocatalytic technologies for selective formation of high added value chemicals

Abstract This review presents a survey of some heterogeneous photocatalytic processes for the synthesis of high-value added compounds carried out in photocatalytic membrane reactors (PMRs). The two technologies can be easily integrated due to the similar conditions at which they usually operate. Furthermore, significant advantages derive from the coupling and in some cases also synergistic effects can be observed. These features have been highlighted for the photocatalytic syntheses reviewed along with engineering and design aspects investigated for some industrially relevant high-value added compounds. Notably, photocatalytic syntheses carried out in PMRs are still rare mainly because inte…

Photodegradation of lincomycin in aqueous solution

Aqueous solutions of lincomycin were irradiated with UV light in homogeneous and heterogeneous systems. Lincomycin disappeared in both systems but the presence ofTiO2noticeably accelerated the degradation of the antibiotic in comparison with direct photolysis. The rate of decomposition was dependent on the concentration of lincomycin and followed a pseudo-first-order kinetics. Photolysis involved only the oxidation of lincomycin without mineralization. Differently, the treatment withTiO2and UV light resulted in a complete mineralization of the antibiotic. The degradation pathways involved S- and N-demethylation and propyldealkylation. The mineralization of the molecule led to the formation …

Photocatalytic CO2 reduction in gas-solid regime in the presence of bare or Cu-loaded TiO2 and water

On the Photoisomerization of Caffeic Acid in the Presence of Nanostructured TiO2

Photocatalytic Ozonation: from Science to Aquaculture Applications

Demographic growth and management of water and food resources are probably the most challenging issues of the coming years. In this scenario, intensive aquacultura will be increasingly important in the near future

4-Nitrophenol Oxidation in a Continuous Fixed Bed Photoreactor Containing Titanium Dioxide Supported on Glass Beads

Selectivity of hydroxyl radical in the partial oxidation of aromatic compounds in heterogeneous photocatalysis

Abstract The photocatalytic oxidation of different benzene derivatives has been investigated in order to understand how the substituent group affects the selectivity to hydroxylated compounds. Experimental runs were performed by using TiO2 (Merck) aqueous suspensions at natural pH irradiated by near-UV light. The organic molecules used as substrate contained an electron withdrawing group (EWG) (nitrobenzene, cyanobenzene, benzoic acid, 1-phenylethanone), an electron donor one (EDG) (phenol, phenylamine, N-phenylacetamide) or both an EWG and an EDG (4-chlorophenol). The results clearly indicated that the primary photocatalytic oxidation of aromatic compounds containing an EDG gives rise main…

Hydroxilation of benzoic acid and phenol in the presence of TiO2 photocatalysts: selectivity and kinetics

Photodegradation of paraquat in aqueous suspension of polycrystalline TiO2 : genotoxicity by using ames test

VOC's abatement: Photocatalytic oxidation of toluene in vapour phase on anatase TiO2 catalyst

Publisher Summary The photocatalytic oxidation of toluene in the presence of water was performed in the gas–solid regime at room temperature by using TiO2. It has been found that the presence of water was beneficial to achieve the almost complete photo-oxidation of toluene to CO2 and H2O, in fact, only very small amounts of benzaldehyde vapor that is the main product of toluene partial oxidation, were detected. Volatile organic compounds, VOC's, are an important class of air pollutants usually found in the atmosphere of all urban and industrial areas. Toluene is one of these compounds, and because of its noxious nature several strategies have been identified to reduce its presence in indoor…

Photocatalytic oxidation of aromatic alcohols to aldehydes in aqueous suspension of home-prepared titanium dioxide

Abstract Oxygenated aqueous suspensions of home-prepared (HP) and commercial TiO2 catalysts were used in a batch photoreactor for carrying out the oxidation of benzyl alcohol (BA) and 4-methoxybenzyl alcohol (MBA) under different operative conditions. HP catalysts were synthesized from TiCl4 and underwent a hydrolysis treatment of different times under mild conditions. The textural characterization of catalysts was carried out with XRD, SEM observations, BET surface area and porosity measurements. For both alcohols the main oxidation products were the corresponding aromatic aldehydes and CO2. The HP catalysts exhibited selectivity values towards the aldehyde production up to 28% (BA convers…

Sequential biological and photocatalysis based treatments for shipboard slop purification: A pilot plant investigation

This study investigated the treatment of a shipboard slop containing commercial gasoline in a pilot plant scale consisting of a membrane biological reactor (MBR) and photocatalytic reactor (PCR) acting in series. The MBR contributed for approximately 70% to the overall slop purification. More precisely, the biological process was able to remove approximately 40%, on average, of the organic pollution in the slop. Nevertheless, the membrane was capable to retain a large amount of organic molecules within the system, amounting for a further 30% of the influent total organic content removal. However, this affected the membrane fouling, thus resulting in the increase of the pore blocking mechani…

TiO2-induced photoisomerization of caffeic acid

Clean by Light Irradiation: Practical applications of supported TiO2

Front Cover: (Photo)electrocatalytic Versus Heterogeneous Photocatalytic Carbon Dioxide Reduction (ChemPhotoChem 9/2021)

Arbeitsmethoden und Versuche: Abschnitte 8.4.2 (Versuche 37 - 43) - 8.6

Ozone enhanced activity of aqueous titanium dioxide suspensions for photocatalytic oxidation of free cyanide ions

The ozonization and the heterogeneous photocatalytic method are contemporarily applied for the oxidation of free cyanide ions. A batch photoreactor with immersed lamp was used for treating aqueous suspensions containing polycrystalline TiO2 powders irradiated in the near-UV region. Air or ozone–air mixtures were used as oxidation reactants. At the used experimental conditions, the photoreaction proceeds at a measurable rate until low values of cyanide concentration. In the presence of ozone (O3) several parallel reaction routes are contributing to the overall cyanide degradation: (i) homogeneous oxidation by ozone; (ii) heterogeneous catalytic reaction by ozone; (iii) photocatalytic degrada…

ChemInform Abstract: Elemental Bromine Production by TiO2Photocatalysis and/or Ozonation.

Significant production of elemental bromine (Br2 ) was observed for the first time when treating bromide containing solutions at acidic pH, with TiO2 photocatalyst, ozone, or a combination thereof. Br2 selectivities up to approximately 85 % were obtained and the corresponding bromine mass balance values satisfied. The process is general and may be applied at a laboratory scale for green bromination reactions, or industrially as a cheap, safe, and environmentally sustainable alternative to the currently applied bromine production methods.

TiO2 Nanomaterials Used as Photocatalysts for Selective Heterogeneous Syntheses of Alcohols to Aldehydes in Water

Photocatalytic membrane reactors: configurations, performance and applications in water treatment and chemical production

Abstract: The configurations and performance of photocatalytic membrane reactors (PMRs) assembled with membranes (also photocatalytic type) and/or suspended photocatalyst are described. Examples of the application of PMRs in water/wastewater treatment as well as in photocatalytic synthesis are shown. An outline of the modeling of PMRs is presented with a brief economic analysis; future trends in PMRs are also discussed.

Preparation, Characterization, and Photoactivity of Polycrystalline Nanostructured TiO2 Catalysts.

Various preparations of nanostructured TiO2 starting from Ti(iso-OC3H7)4 or TiCl4 are reported. The samples were characterized by X-ray diffractometry, specific surface area and porosity determinations, scanning and transmission electron microscopy, and diffuse reflectance spectroscopy. 4-Nitrophenol photodegradation in aqueous medium was employed as a probe reaction to test the photoactivity of the catalysts. The photoactivity of some samples derived from Ti(iso-OC3H7)4 was found comparable with that of commercial powders. Calcination after the hydrolysis process was necessary to achieve crystallization of the particles before using them as photocatalysts for the reaction studied. The samp…

A Method for Determining Optical Properties and Quantum Yields of Photocatalytic Suspensions

Photocatalytic oxidatioon of acetonitrile : degradation performance in gas-solid and liquid-solid systems

A facile way to synthesize noble metal free TiO2 based catalysts for glycerol photoreforming

In this work anaerobic heterogeneous photocatalytic solar/UV light reforming of glycerol in aqueous media was performed with Pt-photodeposition and noble metal free modified TiO2 photocatalysts prepared through ball milling, a very simple and cheap coupled catalyst preparation method. Different amounts of Cu2O or 3% CuO were loaded on TiO2 using ball milling and during each run glycerol conversion, hydrogen and CO2 formed in the gas phase and 1,3-dihydroxyacetone (DHA) and glyceraldehyde (GA) in the liquid phase were determined. The results were compared with the aim to verify the effectiveness of Cu2O in replacing Pt. Using noble metal free photocatalysts, 33% glycerol conversion, 10.3% an…

Visible-light-induced oxidation of trans-ferulic acid by TiO2 photocatalysis

Abstract The oxidation of trans-ferulic acid (C10H10O4) in aqueous TiO2 dispersion occurs via the formation of a charge-transfer complex on the TiO2 surface that is able to absorb visible light (λ ⩾ 400 nm). The main product is CO2, whereas secondary oxidation products are organic species such as vanillin, caffeic acid, homovanillic acid, and vanillylmandelic acid. Oxidation through the formation of a charge-transfer complex occurs only in the presence of specific TiO2 samples. Experiments in the absence of oxygen, in the presence of bromate ions and by using a phosphate-modified TiO2, have been carried out for investigating the reaction mechanism. In order to study the interaction between …

Photocatalytic oxidation of cyanide in aqueous TiO2 suspensions irradiated by sunlight in mild and strong oxidant conditions

Abstract The photocatalytic oxidation of free cyanide ions was carried out in aqueous aerated suspensions containing polycrystalline TiO2 (anatase) irradiated by sunlight. The influence of the presence of an organic compound (phenol) or of a strong oxidant (H2O2) on the photoprocess was also studied. The dependence of cyanide photo-oxidation rate on the following parameters: (1) cyanide concentration; (2) catalyst amount; and (3) phenol concentration was investigated. At the used experimental conditions, the kinetics of cyanide photo-oxidation is independent of the initial cyanide concentration and of the catalyst amount while it is affected by the phenol concentration and by the presence o…

TiO2 based Inorganic-Organic Hybrid Photocatalysts for Highly Selective Alcohol Partial Oxidation

An integrated approach to develop a composite hybrid material made of titanium dioxide functionalized with an organic conjugated phenol (DIOL) and silver NPs suitable for the selective oxidation of water soluble aromatic alcohols to aldehydes in water under UV irradiation and very mild conditions was used. The 86% selectivity observed for the Rutile/DIOL/Ag composite is, to the best of our knowledge, the highest thus far reported for partial oxidation of aromatic alcohols to aldehydes in water suspensions of titanium dioxide. The method is general as it relies on the concomitant easier adsorption of the aromatic alcohol and more facile release of the aldehyde, coupled to fast interfacial el…

Studio di processi fotocatalitici: dalla preparazione del fotocatalizzatore alla comprensione della cinetica e del meccanismo di reazione

Sintesi di Vanillina tramite Reazione di Ossidazione Fotocatalitica con TiO2 in Fase Acquosa

Photocatalytic Oxidation of Acetonitrile

Photocatalytic Degradation of Paraquat and Genotoxicity of its Intermediate Products

Abstract The photocatalytic degradation of paraquat (1,1-dimethyl-4,4′-bipyridylium dichloride) aqueous solutions in the presence of polycrystalline TiO2 Degussa P25 irradiated by near-UV light was investigated. The substrate and total organic carbon concentrations were monitored by UV spectroscopy and TOC measurements, respectively: the complete photocatalytic mineralization of paraquat (20 ppm) was achieved after ca. 3 h of irradiation by using 0.4 g l−1 of catalyst amount at natural pH (ca 5.8). On the contrary no significant photodegradation of paraquat was observed in the absence of TiO2 under similar experimental conditions. To evaluate the genotoxicity of paraquat and its intermediat…

Photocatalytic synthesis of piperonal in aqueous TiO2 suspensions

Heat transfer by using TiO2 nanofluids

Abstract In the last decades, nanofluids have been proposed as thermo-vector fluids thanks to their interesting properties of thermal conduction and stability, which allow interesting performance in heat transfer applications. Consequently, different studies on the thermal properties, the potential benefits, and the possible applications of nanofluids appeared in the scientific literature. This chapter deals with heat transfer characteristics of TiO2 nanofluids, which nowadays appear to be almost ready for practical applications. Particular attention has been given to the preparation, the characterization, and the effects of different parameters on heat transfer. Moreover, challenges and op…

Home-prepared anatase, rutile, and brookite TiO2 for selective photocatalytic oxidation of 4-methoxybenzyl alcohol in water: reactivity and ATR-FTIR study

5th European Meeting on Solar Chemistry and Photocatalysis -- OCT 04-08, 2008 -- Palermo, ITALY

Heterogeneous photocatalysis from fundamentals to possible applications

This special issue of Catalysis Today Journal, is dedicated to the career of Prof. Vincenzo Augugliaro, University of Palermo, Italy, in the occasion of his retirement in 2015. Prof. Vincenzo Augugliaro was Full Professor of Transport Phenomena at the University of Palermo (Italy) since 1994. He contributed to the fol- lowing research fields: chemical absorption kinetics, biochemical reactor modelling, diffusional kinetics in metallizing alloys and heterogeneous photocatalysis; in this last field he investigated on chemical kinetics of heterogeneous photocatalytic systems, modelling of heterogeneous photoreactors, radiation field in absorbing-reacting media and application of heterogeneous …

Oxidación Fotocatalítica de Acetonitrilo en Regimen Gas-Sólido y Líquido-Sólido

Oxidation of Azo-Dyes in Water by Means of Heterogeneous Photocatalysis in a Membrane Reactor

Heterogeneous photocatalysis: guidelines on experimental setup, catalyst characterization, interpretation, and assessment of reactivity

Soon after the publication of the first pioneering works on heterogeneous photocatalysis, the number of papers on this topic continuously increased. This intriguing field of research is very complex as it endows with an interdisciplinary overview that involves different aspects of chemistry, physics, material and environmental sciences. Even if photocatalytic applications in real processes are often difficult to be implemented and scaled-up, investigations at laboratory scale are easy to be performed, and in some cases they may give rise to misconceptions. For this reason, the present work aims to sum up most of the common experimental techniques and procedures generally used in heterogeneo…

Study on a photocatalytic membrane reactor for water purification

Abstract Some results obtained in a photocatalytic membrane reactor, to be used for degradation of toxic organic species dissolved in water, are reported. The catalyst, TiO 2 P25 Degussa, was immobilised by means of a flat sheet polymeric membrane and 4-Nitrophenol (4-NP) was used as a model molecule to evaluate the reactor performance. A preliminary investigation of the stability, under UV irradiation, of some eligible polymeric membranes was carried out by using scanning electron microscopy (SEM), optical microscopy (OM), determinations of water permeation flux (WPF) and total organic carbon (TOC). These tests showed that commercial membranes made of fluoride + PP (FS 50 PP-Dow), polysulp…

Photocatalytic Oxidation of Aromatic Alcohols to Aldehydes in Aqueous Suspension of Home Prepared Titanium Dioxide. 1 Selectivity Enhancement by aliphatic alcohols

Oxygenated aqueous suspensions of home-prepared (HP) and commercial TiO2 catalysts were used in a batch photoreactor for carrying out the oxidation of benzyl alcohol (BA) and 4-methoxybenzyl alcohol (MBA) under different operative conditions. HP catalysts were synthesized from TiCl4 and underwent a hydrolysis treatment of different times under mild conditions. The textural characterization of catalysts was carried out with XRD, SEM observations, BET surface area and porosity measurements. For both alcohols the main oxidation products were the corresponding aromatic aldehydes and CO2. The HP catalysts exhibited selectivity values towards the aldehyde production up to 28% (BA conversion: 50%)…

Enhanced one-component spray polyurethane foams via sol-gel microspheres doped with aqueous glycerol

The sol-gel microencapsulation of aqueous glycerol in silica-based microspheres affords functional materials that can be used to cure one-component polyurethane foams (OCF) formulations affording better and greener foam formation. These findings are important and may open the route to more sustainable materials, such as foams, coatings, adhesives, and sealants that are widely utilized in many industrial sectors. © 2013 American Chemical Society.

Heterogeneous Photocatalysis and Photoelectrocatalysis: From Unselective Abatement of Noxious Species to Selective Production of High-Value Chemicals

Heterogeneous photocatalysis and photoelectrocatalysis have been considered as oxidation technologies to abate unselectively noxious species. This article focuses instead on the utilization of these methods for selective syntheses of organic molecules. Some promising reactions have been reported in the presence of various TiO2 samples and the important role played by the amorphous phase has been discussed. The low solubility of most of the organic compounds in water limits the utilization of photocatalysis. Dimethyl carbonate has been proposed as an alternative green organic solvent. The recovery of the products by coupling photocatalysis with pervaporation membrane technology seems to be a…

Photocatalytic Selective Oxidation of 4-Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home-Prepared Titanium Dioxide Catalyst

WOS: 000246040000026

Photocatalytic degradation of toluene in aqueous suspensions of polycrystalline TiO2 in the presence of the surfactant tetradecyldimethylamino-oxide

The heterogeneous photocatalytic method has been used for carrying out the toluene oxidation in synthetic aqueous solutions containing also a zwitterionic surfactant, i.e. tetradecyldimethylamino-oxide (C 14 DMAO). A batch photoreactor with immersed lamp and two kinds of polycrystalline TiO 2 catalysts were used. The results indicate a substantial increase of the toluene degradation rate in the presence of the surfactant; the complete photo- oxidation of toluene was achieved in a few hours of irradiation at the used experimental conditions; at higher irradiation times also C 14 DMAO was completely degraded. The main intermediates of toluene degradation were p-cresol (4-methyiphenol) and ben…

Kinetics of photocatalytic degradation of pharmaceuticals in aqueous TiO2 suspension

Studio della Fotodegradazione di Antibiotici in Ambiente Acquoso

Photocatalytic Oxidation of Cyanides in Aqueous Titanium Dioxide Suspensions

The photocatalytic oxidation of free cyanides in aqueous suspensions containing polycrystalline TiO2(anatase) powders irradiated in the near-UV region has been investigated. The rate of cyanide photooxidation has been studied by varying the following operative parameters: (i) initial cyanide concentration; (ii) catalyst concentration; (iii) initial pH; (iv) power of irradiation; and (v) chloride ion concentration in the reacting mixture. Under the used experimental conditions the photoreaction proceeded at a measurable rate until the complete disappearance of cyanides. The kinetics of cyanide photooxidation is affected by the catalyst concentration, the chloride ion concentration, and the p…

Preparation and photoactivity of nanostructured TiO2 particles obtained by hydrolysis of TiCl4

This work reports the preparation of nanostructured polycrystalline TiO2 photocatalysts obtained by hydrolysis of TiCl4 in very mild conditions. Several samples were prepared as suspensions or colloidal dispersions by using TiCl4/H2O volume ratios ranging between 1:1 and 1:100. The samples were characterised by X-ray diffraction analysis, specific surface area determination, diffuse reflectance spectroscopy and scanning electron microscopy. 4-Nitrophenol photodegradation was used as probe reaction to test the photoactivity of the catalysts. Some samples revealed a photoactivity higher than that of Degussa P25 in similar experimental conditions and the most photoactive one was that prepared …

Photocatalytic thin films of TiO2 formed by a sol-gel process using titanium tetraisopropoxide as the precursor

Abstract Thin TiO 2 films were prepared with the dip-coating technique by using sols deriving from titanium tetraisopropoxide. TiO 2 films were formed on glass substrates previously covered by a SiO 2 layer obtained from a tetraethylortosilicate sol. The films, after a thermal treatment at 673 K, mainly consisted of TiO 2 anatase. The samples were characterised by X-ray diffraction, UV–Vis spectroscopy, scanning electron microscopy and atomic force microscopy. The photoactivity of the various films was tested by using as probe reaction the photo-oxidation of 2-propanol in gas-solid regime. The photoreactivity results indicated that the TiO 2 films were efficient for degrading 2-propanol und…

Photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde in a fixed bed continuous reactor,

Formation of high added value chemicals by photocatalytic treatment of biomass

The depletion of fossil fuel requires the search for alternative renewable feedstock and environmentally friendly methods for the production of high value-added compounds and fuels. In this context, the efficient use of biomass has emerged as a significant research field as it represents an alternative green and renewable carbon source. Various technologies have been explored for this purpose and heterogeneous photocatalysis represents a valid alternative to the catalytic methods since it can be carried out under mild experimental conditions without the addition of harmful oxidizing agents. Different biomass components have been used as the starting materials, and many valuable chemicals h…

Green Organic Reactions by TiO2 Photocatalysis

This contribution gives an account of TiO2-based selective photocatalysis as a green synthetic tool for the production of organics. Some case studies of the most common transformations carried out by means of photocatalytic reactions are illustrated.

Synthetic Green Chemistry through Heterogeneous Photocatalysis

This contribution deals with a short review of some application of TiO2 to green organic synthesis. In particular to selective oxidation of aromatic alcohols under mild conditions.

Selective Photocatalytic Production of Aldehydes

A reactor for photoelectrocatalytic oxidation of aromatic alcohols

Overview on oxidation mechanisms of organic compounds by TiO2 in heterogeneous photocatalysis

This review provides the reader with a general overview on heterogeneous photocatalytic oxidation mechanisms in the presence of TiO2, with a special address to conversion of aliphatic and aromatic organic species. The aim was to clarify the steps of the photo-oxidation of the various classes of compounds and to relate them with the properties of the catalysts and the experimental conditions used. Reactions carried out to perform complete degradation and photocatalytic partial oxidations have been deeply discussed. Recent isotopic studies highlighted new reaction pathways concerning partial oxidation of alcohols to aldehyde and oxidation of benzene while EPR investigations confirmed that not…

Preparation and characterization of Al2O3 supported TiO2 catalysts employed for 4-nitrophenol photodegradation in aqueous medium

Abstract In this paper the preparation and some bulk and surface characterizations of set of Al2O3 supported TiO2 photocatalysts are reported. The powders were home prepared by a wet impregnation method using titanium (IV) isopropylate. The impregnation was followed by thermal treatments and this procedure was repeated several times in order to obtain samples with different amounts of TiO2. The solids were characterized by X-ray diffraction, specific surface area determination, scanning electron microscopy coupled with an electron microprobe used in an energy-dispersive mode and diffuse reflectance spectroscopy. Moreover, all of them were tested as photocatalysts by using different kinds of…

Preparation and characterisation of TiO2 (anatase) supported on TiO2 (rutile) catalysts employed for 4-nitrophenol photodegradation in aqueous medium and comparison with TiO2 (anatase) supported on Al2O3

Abstract In this paper the preparation of two sets of polycrystalline photocatalysts prepared by supporting TiO2 (anatase) on TiO2 (rutile) or Al2O3 is reported. The powders were prepared by a wet impregnation method using titanium(IV) isopropylate. The impregnation was followed by thermal treatment and this procedure was repeated several times in order to obtain samples with progressively increasing amounts of TiO2 (anatase). The photocatalytic activity of all of the specimens was tested by carrying out the 4-nitrophenol photodegradation, used as a “probe” reaction, in aqueous medium and in different kinds of batch photoreactors. The solids were characterised by X-ray diffraction (XRD), sp…

Enhancing Selectivity In Photocatalytic Formation Of P-Anisaldehyde In Aqueous Suspension Under Solar Light Irradiation Via Tio2 N-Doping

The photocatalytic partial oxidation of 4-methoxybenzyl alcohol to the corresponding aldehyde (p-anisaldehyde) was performed under simulated solar irradiation by using home prepared N-doped TiO2 catalysts. The photocatalysts were prepared by a sol–gel method, using TiCl4 as TiO2 precursor and NH4Cl, urea or NH4OH as N-doping sources. A commercial TiO2 (Degussa P25) was also used for comparison aims. The prepared catalysts were characterized by BET specific surface area, XRD, ESEM and UV-vis spectroscopy. The reactivity results show that (i) the doped catalysts are predominantly amorphous, and they show selectivity values far higher than those of the corresponding undoped ones and of well cr…

"Caratterizzazione ottica di sospensioni acquose di fotocatalizzatori utilizzati in processi di abbattimento di inquinanti organici

Snuff.La morte sul set

Influence of Adsorbed Water on the Activation Energy of Model Photocatalytic Reactions

Two commercial (Merck and Sigma-Aldrich) and two home prepared (HP05 and HP05C) powdered TiO2 photocatalysts were investigated by fast field cycling nuclear magnetic resonance experiments in order to explore the nature of the interactions between water and the solid surfaces. The results were related to the activation energies determined at temperatures ranging from 303 to 353 K for the photocatalytic oxidation in water of three model molecules presenting different interactions with the solid surface (catechol, phenol, and metylbenzoate). The photoactivity results at different temperatures were comparable to each other because the runs were carried out while keeping constant the concentrati…

Photoactivity under visible light of metal loaded TiO2 catalysts prepared by low frequency ultrasound treatment

Abstract Visible-light responsive bare and metal loaded (Pt, Ag, Rh, Pd) TiO 2 photocatalysts were prepared by using a simple ultrasound treatment. This method induced bulk oxygen deficiency resulting in a narrowing bandgap (from 3.18 to 3.04 eV) and in visible light absorption. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area (SSA) and pore size distribution (PSD), UV–vis diffuse reflectance spectroscopy (DRS), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the samples was evaluated by using the 4-nitrophenol oxidation reaction and the photocatalytic oxidation of glucose w…

Photodegradation kinetics of aniline, 4-ethylaniline, and 4-chloroaniline in aqueous suspension of polycrystalline titanium dioxide

The photodegradation process of aniline, 4-ethylaniline, and 4-chloroaniline in aqueous suspension of irradiated TiO2 (anatase) powder has been investigated. A batch photoreactor with immersed lamp irradiating in the near-UV region has been used for carrying out the reactivity experiments. For each substrate the influence of the initial concentration of organic compound and of pH on the degradation rate has been investigated. The main intermediates and the end products have been identified and determined, the total mass balance being satisfied. The kinetic modelling of the series of reactions occurring in the system has been satisfactorily carried out with a Langmuir-Hinshelwood rate law. T…

A reaction engineering approach to kinetic analysis of photocatalytic reactions in slurry systems

Abstract The knowledge of the rate equation is fundamental for the assessment of the activity of the photocatalytic material and for the study, design and optimization of photocatalytic reactors. In the case of photocatalytic reactions, the local volumetric rate of photon absorption (LVRPA) affects the reaction rate and its inherently uneven distribution within a “slurry” reactor makes complex a correct kinetic analysis. In the present work it is shown which are the critical aspects of the kinetic analysis in slurry reactors and how to carry out photocatalytic experiments to minimize the misinterpretations of the experimental results. In particular, the influence of the type of illumination…

Mechanistic aspects of oxalic acid oxidation by photocatalysis and ozonation

Photoadsorption determination for irradiated catalyst in liquid-solid system

Two-Dimensional Modeling of an Externally Irradiated Slurry Photoreactor

Abstract A batch cylindrical photocatalytic reactor, externally irradiated by 1–6 UV fluorescent lamps and containing a stirred slurry of polycrystalline TiO2, was modeled by coupling a modified Langmuir–Hinshelwood kinetics together with a two-dimensional light intensity field. The radiation field has been determined on the main assumptions of diffuse radiation, isotropic scattering and negligible backward reflected photon flow. The model has been applied to the photocatalytic oxidation of organic substrates which do not undergo homogeneous photochemical degradation. The model is characterized by the following four parameters: the kinetic constants of substrate adsorption, desorption and d…

Preparazione, Caratterizzazione e Fotoattività di Film di TiO2

Preparation and characterization of photocatalytic TiO2 films

Performance of a Continuousfixed Bed Photocatalytic Reactor for Selective Oxidation of 4-Methoxybenzyl Alcohol to Aldehyde in Organic-free Water

Process Intensification through Coupled Photocatalysis-Ozonation of Contaminated Bromide Containing Waters

Properties of titanium dioxide

"Properties of titanium dioxide" presents a survey of the main physicochemical properties of TiO2 upon which rely all of the applications of this material. Structures and morphologies of titanium dioxide have been taken into account, also in correlation with thermodynamic properties. Bulk and surface defectivity has been described in detail, because of its relevant consequences in terms of catalytic activity. The basic mechanisms of interaction between photons and TiO2 have been discussed on the basis of the optoelectronic features of the semiconductor. Finally, electrical, mechanical, and rheological properties of TiO2 have been presented.

Degradazione Fotocatalitica Eterogenea di Acetonitrile e Toluene in Regime Gas-Solido e Liquido-Solido

Photocatalytic oxidation of aromatic alcohols to aldehydes in aqueous suspension of home prepared titanium dioxide

In this paper some intrinsic electronic properties of home prepared (HP) TiO2 catalysts were investigated by diffuse reflectance spectroscopy and quasi-Fermi level measurements. These powders were used for carrying out the photocatalytic oxidation of benzyl alcohol to benzaldehyde and CO2 in water; the selectivity for aldehyde formation was enhanced by the addition of small amounts of ethanol, a typical hole trap. The values of band gap, valence band and conduction band edges are almost identical for all the HP samples in which anatase phase is predominant, whereas appreciable differences can be noticed for an HP sample containing high amount of rutile phase. A comparative ATR-FTIR study of…

Determination of Photoadsorption Capacity of Polychrystalline TiO2 Catalyst in Irradiated Slurry

WOS: 000322711800002

ChemInform Abstract: Advances in Selective Conversions by Heterogeneous Photocatalysis

Selective photocatalytic conversions are offering an alternative green route for replacing environmentally hazardous processes with safe and energy efficient routes. This paper reports the most recent advances in the application of heterogeneous photocatalysis to synthesize valuable compounds by selective oxidation and reduction.

Study on TiO2 Photocatalytic Membrane Reactors for Purification of Aqueous Media

Nanochemistry Aspects of Titania in Dye Sensitized Solar Cells

We analyze the main nanochemistry factors affecting photovoltaic performance in TiO2 employed as wide bandgap semiconductor in dye-sensitized solar cells (DSCs). What is the best morphology of the oxide? Which processes yield the required structures? Finally, putting the discussion in the context of the rapid evolution of photovoltaic technologies, we argue that new titania nanostructures will form the basic component of second-generation solar modules based on dye solar cells.

Validation of a two-dimensional modeling of an externally irradiated slurry photoreactor

Abstract A two-dimensional model describing the behavior of a batch cylindrical photoreactor has been validated through a series of photocatalytic reactivity runs. The light intensity radiation field produced by 1–6 external UV fluorescent lamps was modeled together with Langmuir–Hinshelwood kinetics and 4-nitrophenol (NP) and Degussa P25 TiO 2 were used as the probe molecule and the catalyst, respectively. The experiments were carried out under different conditions of light intensity, photocatalyst amount and substrate concentration. The model parameters were the kinetic constant of substrate adsorption, desorption and degradation and the exponent of the power law expressing the kinetics d…

Preparation and Photoactivity of Rutile Obtained by Hydrolysis of TiCl4

DINAMICA DELL’ACQUA SULLA SUPERFICIE DI UN BIOSSIDO DI TITANIO NANOSTRUTTURATO SINTETIZZATO IN LABORATORIO

Un campione biossido di titanio sintetizzato in laboratorio è stato ottenuto mediante idrolisi di TiCl4 in acqua deionizzata (rapporto in volume 1:10) a temperatura ambiente. Dopo 12 h di agitazione la soluzione trasparente è stata portata all’ebollizione per 0.5 h per ottenere la sospensione finale. La sospensione è stata quindi seccata alla temperatura di 50°C per ottenere il catalizzatore in polvere. Successivamente, la polvere così ottenuta è stata lavata e centrifugata diverse volte allo scopo di ridurre fino a valori trascurabili la concentrazione di ioni cloruro nell’acqua di lavaggio. Il catalizzatore così ottenuto è stato denominato HP0.5 (Home Prepared bollito per 0.5 h) [1]. Un g…

Combination of ozonation and photocatalysis for purification of aqueous effluents containing formic acid as probe pollutant and bromide ion

The treatment by advanced oxidation processes (AOPs) of waters contaminated by organic pollutants and containing also innocuous bromide ions may generate bromate ions as a co-product. In the present work heterogeneous photocatalysis and ozonation have individually been applied and in combination (integrated process) to degrade the organic compounds in water containing also bromide anions. The results show that: i) the sole photocatalysis does not produce bromate ions and in the case of its presence, it is able to reduce bromate to innocuous bromide ions; ii) the integration of photocatalysis and ozonation synergistically enhances the oxidation capabilities; and iii) in the integrated proces…

Photocatalytic process intensification by coupling with pervaporation

The integration of photocatalysis with a membrane separation process, in particular pervaporation, permits the recovery of valuable intermediate compounds (aromatic aldehydes) while they are produced avoiding their further degradation in the reactive ambient. In this way the yield and the conversion are enhanced. The coupling of the two processes is straightforward and the integration is complete even maintaining pervaporation and photocatalysis in two separate apparatuses provided that the process stream is continuously recycled at a sufficiently high flow rate. Additional advantages are: higher degree of purification of the aldehyde in the powder-free product stream, semicontinuous produc…

Economical aspects, toxicity, and environmental fate of cerium oxide

Abstract The present chapter reports some economical aspects of the cerium oxide market. Porter’s and PESTEL analyses have been used to evidence the strengths and weaknesses of the ceria market, along with the potentiality and opportunities within the years to come. The wide use of CeO2 nanoparticles in many applications requires to consider also issues related to their toxicity and environmental fate. In this regard, some contradictory reports in the relevant literature have been surveyed, thus highlighting the need for further and detailed investigation on these topics in order to propose effective strategies of risk assessment and environmental remediation.

Process Intensification by Using Ozonation Coupled with TiO2 Photocatalysis for Treating Bromide and/or Bromate Ions Containing Water: The Role of Co-present Model Organic Compounds

(Photo)electrocatalytic Versus Heterogeneous Photocatalytic Carbon Dioxide Reduction

The present review summarizes some of the main results achieved in electrochemical, photocatalytic, and (photo)-electrocatalytic systems for the reduction of carbon dioxide. After a preliminary survey of the electrocatalytic and photocatalytic systems in terms of materials used, efficiencies, operating conditions, and product distribution, it is shown how the combination of the two approaches affords often higher efficiency than the single technologies and allows better control of the product distribution. In fact, the peculiar energetic distribution at the interface of irradiated semiconductors under opportune electrical bias enables enhancement of the spatial separation of the photogenera…

Photodegradation of Lincomycin in aqueous TiO2 suspension by using artificial or solar light

Modelling of a recirculating photocatalytic microreactor implementing mesoporous N-TiO2 modified with graphene

Abstract The use of microreactors in (photo)catalytic processes offers new possibilities for studying and optimizing many mass and photon transfer limited reactions. In this study, we propose a scalable computational fluid dynamics (CFD) model for the prediction of photocatalytic degradation of a model pollutant (4-nitrophenol) using immobilized N-doped TiO2 grown over reduced graphene oxide (N-TiO2/rGO) in a photocatalytic microreactor working in continuous flow-recirculation mode. The mode of operation used in this study allows the reduction of mass transfer limitations inherent to heterogeneous photocatalytic reactions taking place on immobilized catalysts. A CFD model was developed for …

Degradation of Lincomycin in Aqueous Medium: Coupling of Solar Photocatalysis and Membrane Separation

Preparation, thermal analysis and photoactivity of TiO2 samples

TiO2 Heterogeneous Photocatalysis as a Selective Tool for Organic Green Syhtneses

Elemental Bromine Production by TiO2 Photocatalysis and/or Ozonation

Significant production of elemental bromine (Br2 ) was observed for the first time when treating bromide containing solutions at acidic pH, with TiO2 photocatalyst, ozone, or a combination thereof. Br2 selectivities up to approximately 85 % were obtained and the corresponding bromine mass balance values satisfied. The process is general and may be applied at a laboratory scale for green bromination reactions, or industrially as a cheap, safe, and environmentally sustainable alternative to the currently applied bromine production methods.

Influence of the Substituent on Selective Photocatalytic Oxidation of Aromatic Compounds in Aqueous TiO2 Suspensions.

Experimental results are reported showing that the photocatalytic oxidation of aromatic compounds containing an electron-donor group (EDG) gives rise mainly to ortho- and para-monohydroxy derivatives while in the presence of an electron-withdrawing group (EWG) all the monohydroxy derivatives are obtained.

Photocatalytic Isomerization of Caffeic Acid and its Cyclization to Esculetin

tThe photoisomerization of trans-caffeic acid to cis-caffeic acid has been studied in the presence of N2in homogeneous aqueous solutions and in suspensions of various TiO2catalysts. The results supportedthe hypothesis of an energy transfer process from TiO2 to the substrate due to the recombination of the photogenerated electron–hole pairs.

Partial photocatalytic oxidation of glycerol in TiO2 water suspensions

2nd European Conference on Environmental Applications of Advanced Oxidation Processes -- SEP 09-11, 2009 -- Nicosia, CYPRUS

Photocatalytic abatement of organic compounds using home prepared TiO2 as photocatalysts

Pervaporation membrane reactors (Chapter 3)

Photocatalytic oxidation of gaseous toluene on anatase TiO2 catalyst: Mechanistic aspects and FT-IR investigation

Abstract Photo-oxidation of toluene has been carried out in gas–solid regime by using polycrystalline anatase TiO2 as the catalyst. The reacting gaseous mixture was toluene, air and water in various molar ratios. A pyrex fixed-bed continuous photoreactor irradiated by a medium pressure Hg lamp was used for performing the photoreactivity experiments. The main oxidation product was benzaldehyde but benzene, benzyl alcohol and traces of benzoic acid, phenol and unidentified compounds were also detected. The molar conversion to benzaldehyde with respect to the initial amount of toluene was ca. 20% in the best experimental conditions. Benzene was produced only as a transient product during the f…

Green synthesis of bromine by TiO2 heterogeneous photocatalysis and/or ozone: A kinetic study

Abstract Elemental bromine is an industrially relevant compound traditionally produced from bromide ions by using chlorine as the oxidizing agent. Problems related to transportation and handling of the corrosive, expensive and toxic chlorine make green synthetic alternatives highly desirable. In this paper the green synthesis of bromine from bromide in aqueous solutions under mild conditions by means of TiO2 photocatalysis and/or ozonation has been investigated from a kinetic point of view. The ozonation in the absence of the photocatalyst follows a first order kinetic with respect to both ozone and bromide. The kinetics of the reactions in the presence of the photocatalyst has been describ…

Photodegradation of Pharmaceuticals in Water Catalyzed by Polycrystalline TiO2 Powder in a Nanofiltration Membrane Reactor

Improvement of membrane performances to enhance the yield of vanillin in a pervaporation reactor.

In membrane reactors, the interaction of reaction and membrane separation can be exploited to achieve a “process intensification”, a key objective of sustainable development. In the present work, the properties that the membrane must have to obtain this result in a pervaporation reactor are analyzed and discussed. Then, the methods to enhance these properties are investigated for the photocatalytic synthesis of vanillin, which represents a case where the recovery from the reactor of vanillin by means of pervaporation while it is produced allows a substantial improvement of the yield, since its further oxidation is thus prevented. To this end, the phenomena that control the permeation of bot…

Oxidacíon fotocatalítica de alcoholes aromáticos. Influencia de la adicíon de atrapadores de huecos en la selectividad a aldehídos

Photocatalytic ozonation:Maximization of the reaction rate and control of undesired by-products

In theso-calledphotocatalyticozonation(PO)synergisticeffectsbetweenphotocatalysisandozonation enhance therateofoxidationoforganiccompounds,thereforethisintegratedprocessisverypromising for useinwatertreatment.Inthepresentwork,itisdemonstratedthattheimprovementthatcanbe obtained bytheintegratedprocessincomparisonwiththeuncoupledprocessesdependsontherelative weight between photocatalysis and ozonation. In this respect, it has been found that a relatively low rate of photocatalysis (0.3 times the rate of ozonation)issufficienttogetthehighestsynergyandtomaximize the performancesintheoxidationofformate,theadoptedmodelorganiccompound.Thebenefitsof the couplingofphotocatalysistoozonationarenotlimi…

Selective Heterogeneous Photocatalysis: Achievements and Challenges

Removal of drugs in aqueous systens by photoassisted degradation

Aqueous solutions of tetracycline, lincomycin and ranitidine were irradiated with UV light in homogeneous and heterogeneous systems. Two commercial polycrystalline TiO2 powders (Degussa P25 and Merck) were used as photocatalysts. After 5A h, an appreciable photolytic degradation of tetracycline and ranitidine was observed while the degradation of lincomycin was noticeably lower. As far as the mineralization is concerned, a small decrease of the TOC values was measured in the case of tetracycline whereas negligible variations were found for lincomycin or ranitidine. The presence of the photocatalysts greatly enhanced the degradation rates of the drugs with respect to those observed during th…

Pervaporation membrane reactors

Pervaporation is a peculiar membrane separation process which is now considered for the integration with some types of reactions in new promising and interesting applications. Indeed, pervaporation membrane reactors are suitable to some specific utilizations also in sustainable chemistry, which is an area currently characterized by a growing interest. The fundamentals of this type of membrane reactors are presented and the advantages and the difficulties in many applications are discussed and reviewed with particular attention to the opportunities for future developments.

Photo-oxidation of Azo-dyes in Water Catalyzed by TiO2 in a Membrane Reactor

Preparation, characterisation and photoactivity of nanostructured TiO2 catalysts

Optical characterization of TiO2 suspensions: influence of some operational parameter on mean particle size

Photodegradation of pharmaceutical drugs in aqueous TiO2 suspensions: mechanism and kinetics

WOS: 000251165800003

Photocatalytic oxidation of acetonitrile in aqueous suspension of titanium dioxide irradiated by sunlight

The photocatalytic oxidation of acetonitrile (CH3CN) was carried out in aqueous suspensions of polycrystalline TiO2 P25 Degussa irradiated by sunlight. A plug flow photoreactor in a total recycle loop was used for carrying out reactivity experiments in which the concentrations of acetonitrile, of its intermediate oxidation products and of not-purgeable organic carbon (NPOC) were monitored. The influence of the presence of strong oxidant species (H2O2, S2O82−, ClO−) on the process rate was studied. The dependence of acetonitrile photo-oxidation rate on the substrate concentration and on the catalyst amount was also investigated. The photodegradation rate of substrate and NPOC followed first …

Photocatalytic green synthesis of piperonal in aqueous TiO2 suspension

Abstract Piperonal (heliotropine or 3,4-methylenedioxybenzaldehyde) has been synthesized by oxidizing piperonyl alcohol in aqueous UV-irradiated TiO2 suspensions. This compound was identified by GC–MS chromatography, 1H NMR and melting point determination. The other products of the photoprocess were 1,3-bis(3,4-(methylenedioxy)benzyl) ether (found in traces) and CO2, derived from the parallel pathway of photo-mineralization. Commercial and home-prepared TiO2 samples have been tested and the best selectivity (ca. 35%) was obtained by using the home-prepared ones. The reported green process allows to obtain an added value product (piperonal), upon partial oxidation of a cheap reagent.

Photocatalytic Oxidation of Drugs by Using Artificial and Solar Irradiation

Photocatalytic CO2 Reduction in Gas-Solid Regime in the Presence of Bare, SiO2 Supported or Cu-Loaded TiO2 Samples

Both commercial and home prepared (HP) TiO2 samples have been tested for the photocatalytic reduction of CO2. (HP) TiO2 powders were prepared by using TiCl4 or Ti(OC4H9)4 as the precursors to obtain HP1 and HP2 samples, respectively. Also HP Cu-loaded and SiO2 supported TiO2 powders were prepared. The HP samples were more active than the commercial ones for the photoreduction of CO2 with and without water vapour. HP1 produced mainly formaldehyde, HP2 principally methane. Acetaldehyde was found to be the primary product obtained when HP1 was supported on SiO2. The addition of Cu increased the photocatalytic reactivity either of bulk and SiO2-supported HP1. In particular, 1 wt % of Cu improve…

Selective Photocatalytic Oxidation of 4-Methoxybenzyl Alcohol to p-Anisaldehyde in Organic-Free Water in a Continuous Annular Fixed Bed Reactor

Photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde was performed in water organic-free solutions by using a fixed bed continuous photoreactor containing Pyrex beads on which a TiO2 home prepared photocatalyst was supported. The influence of liquid flow rate, inlet alcohol concentration and catalyst amount on the photoprocess was studied. The highest selectivity to p-anisaldehyde was about 47% being CO2, the other main oxidation product; traces of 4-methoxybenzoic acid were also detected. The radiation field inside the photoreactor has been modelled by applying the Monte Carlo method thus allowing the determination of the local volumetric rate of photon absorption (LVRPA).…

Ossidazione selettiva di alcoli aromatici ad aldeidi in sospensioni acquose di TiO2 anatasio e rutilo

Influenza del Sostituente sulla Ossidazione Fotocatalitica Selettiva di Composti Aromatici

Selective aqueous oxidation of aromatic alcohols under solar light in the presence of TiO2 modified with different metal species

AbstractA set of metals modified TiO2 photocatalysts were prepared starting from titanium tetraisopropoxyde and different metal precursors to study the influence of the addition of the various foreign agents on the physico-chemical and photocatalytic properties of the catalysts. The powders were characterized by X-ray diffraction, Raman spectroscopy, specific surface area measurements, scanning electron microscopy, energy dispersive X-ray spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence, temperature programmed desorption after CO2 adsorption. The photocatalytic activity was evaluated using as probe reactions the partial oxidation of three aromatic alcohols: benzyl al…

Photocatalytic membrane reactors: fundamentals, membrane materials and operational issues

Abstract: This chapter reports the properties of semiconductor materials used in heterogeneous photocatalysis together with a comparison of heterogeneous photocatalytic systems and a brief description of the types of membranes that can be used. Some aspects of membrane operations, such as fouling, separation of a photocatalyst and effectiveness of photodegradation on permeate quality are discussed.

Photochemical and photocatalytic isomerization of trans -caffeic acid and cyclization of cis -caffeic acid to esculetin

Abstract The photoisomerization of trans-caffeic acid to cis-caffeic acid has been studied in the presence of N2 in homogeneous aqueous solutions and in suspensions of various TiO2 catalysts. The results supported the hypothesis of an energy transfer process from TiO2 to the substrate due to the recombination of the photogenerated electron–hole pairs. The differences among the measured photostationary [cis]/[trans] ratios have been attributed to the different physico-chemical properties of the catalysts. In particular, the lowest ratio measured in the presence of Merck TiO2 was ascribed to the very low adsorption of trans-caffeic acid onto the surface of this sample. In the presence of O2 a…

Enhancing Selectivity of Photocatalytic Synthesis of p-Anisaldehyde in Water under Solar Irradiation by N- Doped TiO2

A PERVAPORATION PHOTOCATALYTIC REACTOR FOR THE GREEN SYNTHESIS OF VANILLIN

Abstract Pervaporation is the ideal membrane separation process to be coupled with photocatalysis for the green synthesis of vanillin from ferulic acid. In fact the operative conditions of the two processes are absolutely congruent and the integration is straightforward even operating with separate equipments. The utilization of a highly selective membrane allows the continuous recovery of vanillin by pervaporation from the reacting solution, so that its oxidative degradation is largely avoided and the yield is substantially enhanced. The effects of the main parameters are analyzed resorting to a mathematical model, which is validated by a comparison with the experimental data. In particula…

Visible Light Induced Oxidation of Ferulic Acid by TiO2 Photocatalysis

Oxidation of ferulic acid (C10H10O4) in aqueous medium occurs by using both commercial and home prepared TiO2 samples under visible light irradiation. Among the oxidation products vanillin was found with a selectivity ranging from 1 to 2% with respect to the converted substrate. By considering that TiO2 is unable to absorb visible light and ferulic acid does not react in the absence of TiO2, the observed photoactivity may be explained by the formation of a charge-transfer complex between ferulic acid and TiO2, being the complex able to absorb visible light. Among all the tested semiconductor oxides, only Merck anatase TiO2 does not perform the oxidation of ferulic acid under visible light i…

Heterogeneous photocatalysis: optical characterisation of polycrystalline photocatalysts for pollutant degradation in aqueous medium

Photocatalytic Membrane Reactors: Case Studies and Perspectives

Photocatalysis by polycrystalline semiconductor oxides is being successfully applied to the abatement of organic and inorganic pollutants both in gas and in liquid phase. In order to increase the efficiency of this method, the coupling of this technology with the membrane separation process has been the object of sound investigation. In this combination, the membrane may act in different ways: to confine the photocatalytic powder in the reacting suspension, to selectively separate the photoreaction products, or to be the support of photocatalyst. This article reports recent studies in which different types of membranes (such as distillation, dialysis, nanofiltration, pervaporation and osmos…

Nanomateriali a base di TiO2 come fotocatalizzatori per sintesi selettive di alcoli ad aldeidi in fase acquosa

Green Production of Aldehydes from Alcohols by Heterogeneous Photocatalysis

Advances in selective conversions by heterogeneous photocatalysis

Selective photocatalytic conversions are offering an alternative green route for replacing environmentally hazardous processes with safe and energy efficient routes. This paper reports the most recent advances in the application of heterogeneous photocatalysis to synthesize valuable compounds by selective oxidation and reduction.

Autocatalytic Photo-Oxidation of 2-Methoxybenzyl Alcohol and O2 Quenching therein

PMRs Utilizing Non–Pressure-Driven Membrane Techniques

In the present chapter it is shown how photocatalytic membrane reactors utilizing membrane processes, which are not pressure driven, can exploit various mechanisms to obtain a substantial improvement of the process. The fundamentals of this particular type of membrane reactors are reviewed including the effects of the most important parameters and the methods and rules of coupling photocatalysis and membrane separation. The survey of the studies on photocatalytic membrane reactors (PMRs) utilizing pervaporation, dialysis, membrane contactors and membrane distillation offers the opportunity of discussing the advantages with respect to PMRs adopting pressure driven membrane processes. Indeed,…

REWAQUA: an advanced technology for water purification in sustainable aquaculture based on photocatalytic ozonation

The present study has been undertaken in order to test the real potential of photocatalytic ozonation in a bench-scale recirculating aquaculture system working on a 180 L reef coral aquarium. Notably, this choice may be considered representative. In fact, (i) the system is virtually closed so that fresh water turnover is practically negligible, (ii) the presence of living organisms is highly diversified (corals, fishes, molluscs, echinoderms and crustaceans) and some of them are particularly sensitive to water quality, (iii) high salinity strongly puts a strain on the purification system. The hereby presented purification method has been named REWAQUA, which stands for REcycling Water for A…

Preparation, characterization and photocatalytic activity of TiO2 rutile

Room Temperature Home Prepared TiO2 Rutile Used for Selective Photocatalytic Oxidation of Aromatic Alcohols to Aldehydes in Aqueous Medium

Photocatalytic Oxidation of Acetonitrile in Aqueous Suspension of Titanium Dioxide Irradiated by Sunlight

Oxidación Fotocatalítica del Acetonitrilo en Régimen Gas-Sólido y Líquido-Sólido

Nanostructured rutile TiO2 for selective photocatalytic oxidation of aromatic alcohols to aldehydes in water

WOS: 000253100100022

Photoelectrocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B3 by TiO2 nanotubes

In this paper, the first photoelectrocatalytic (PEC) 3-pyridinemethanol oxidation to 3-pyridinemethanal and vitamin B-3 was investigated. To meet this aim, efficient nanotube structured TiO2 on a Ti plate as a photoanode was prepared by an anodic oxidation method in ethylene glycol and characterized by XRD, SEM, and photocurrent techniques. The effect of nanotube morphology, applied potential, Na2SO4 concentration, stirring speed of solution, and pH on the reaction activity and product selectivities were investigated. The TiO2 phase of all of the anodes was mainly the anatase one. The PEC activity, the intensity of the XRD peak and the photocurrent increased by increasing the nanotube lengt…

Oxidation of oxalate ion in aqueous suspensions of TiO2 by photocatalysis and ozonation

Abstract Oxalate anion has been oxidized in aqueous alkaline solution by using ozonation and photocatalysis in the presence of TiO 2 . A batch annular reactor has been used for carrying out reactivity runs in the presence of air/ozone, air/ozone/near UV irradiation, air/ozone/TiO 2 , air/near UV-irradiated TiO 2 and air/ozone/near UV-irradiated TiO 2 . The Langmuir–Hinshelwood kinetic model adequately describes the photocatalytic results obtained at different reaction conditions and allows determining the values of the kinetic and equilibrium adsorption constants. The contemporary presence of photocatalysis and ozonation shows a significant improvement of the process performance as the oxid…

Optical Characterisation of Semiconductors Used as Photocatalysts for the Degradation of Organic Pollutans in Acqueous Medium

Preparazione di Fotocatalizzatori Nanostrutturati a Base di TiO2

Guidelines for the assessment of the rate law of slurry photocatalytic reactions

Abstract The assessment of the rate law of slurry photocatalytic reactions appears to be a hard task, mainly because in this type of reactions the average rate of reaction, which is experimentally observed in a real reactor, could be very different from the “true” (intrinsic) rate of reaction, which cannot be measured directly. In the present work, it is shown how a proper mathematical model allows the utilization of the differential and/or the integral methods of kinetic analysis. The mathematical model must take into account not only the momentum and the mass balances, but also the radiative transfer equation. However, the discrimination among different proposed kinetic laws remains diffi…

Optical properties and quantum yield determination in photocatalytic suspensions

Knowledge of the optical properties of photocatalytic suspensions is vital for a correct comparison of their energetic efficiency. In this work, the determination of both absorption and scattering coefficients of aqueous suspensions of commercial TiO2 powders irradiated by monochromatic light was carried out by measuring only one quantity—the transmitted photon flow—as a function of the catalyst mass and by applying an asymptotic form of the Kubelka–Munk solution of the radiative transfer equation. Applying a nonlinear fitting procedure the evaluation of the actual values of absorption and scattering coefficients was carried out. The limit for optically thick media of the Kubelka–Munk equat…

Selective Gree-Syntheses of Flavour-Molecules through TiO2 Photocatalysis in Aqueous Suspension

Photocatalytic Active Polymer Expanded Materials Coated with TiO2 Used as Package for Foodstuffs

Photocatalytic Ozonation of Bromide Containing Waste Water: Related Problems and Kinetics Based Strategy Evaluation

In the so-called photocatalytic ozonation (PO) synergistic effects between photocatalysis and ozonation enhance the rate of oxidation of organic compounds, therefore this integrated process is very promising for use in water treatment. In the present work, it is demonstrated that the improvement that can be obtained by the integrated process in comparison with the uncoupled processes depends on the relative weight between photocatalysis and ozonation. In this respect, it has been found that a relatively low rate of photocatalysis (0.3 times the rate of ozonation) is sufficient to get the highest synergy and to maximize the performances in the oxidation of formate, the adopted model organic …

P46: ADSORPTION AND PHOTOCATALYTIC DEGRADATION OF ACETONITRILE ON TiO2: FT-IR AND KINETIC STUDIES

Proprietà ottiche e determinazione della resa quantica per sospensioni fotocatalitiche

Heterogeneous Photocatalysis: a Promising Tool for Green Organic Syntheses

The present work deals with a short review of some applications of photocatalysis to green organic synthesis of valuable products in mild experimental conditions and in the presence of water as solvent.

Selective photooxidation of ortho-substituted benzyl alcohols and the catalytic role of ortho-methoxybenzaldehyde

It has been recently reported by Palmisano et al. (2015) [1] that the oxidation of 2-methoxybenzyl alcohol (2-MBA) to 2-methoxybenzaldehyde (2-MBAD) proceeds in water under near-UV light with an unexpected catalytic effect of 2-MBAD. In order to investigate the catalytic role of aldehyde in photolytic oxidation of ortho-substituted benzyl alcohols (OSBAs), reactivity runs were carried out with 2-methylbenzyl alcohol (2-MeBA), 2-nitrobenzyl alcohol (2-NBA), 2-hydroxybenzyl alcohol (2-HBA) and 2-chlorobenzyl alcohol (2-CIBA) in the absence and in the presence of their corresponding aldehyde. None of those alcohols showed a measurable oxidation rate even in the presence of their aldehydes but …

Combination of advanced oxidation processes and active carbons adsorption for the treatment of simulated saline wastewater

Abstract In the present work, an integrated process combining three different technologies, i.e. heterogeneous photocatalysis, homogeneous ozonation and adsorption on granular activated carbon (GAC) was used for the treatment of a synthetic solution simulating saline wastewater. The synergistic effects between the different methods enhance the oxidation rate of the organic compounds in the integrated process, so that its use may result sustainable. It has been found that a relatively low oxidation rate is sufficient to obtain the highest synergy between the three technologies and to maximize the performances. In particular, coupling ozonation and photocatalysis resulted in 20% enhancement i…

Preparazione e caratterizzazione di film fotocatalitici

Solar Eneergy Conversion to Chemical Photocatalytic Selective Oxidation of 5-(Hydroxymethyl)-2-furaldehyde to 2,5-furandicarbaldehyde in Water by Using TiO2 Nanoparticles

The role of water in the photocatalytic degradation of acetonitrile and toluene in gas-solid and liquid-solid regimes

Photocatalytic degradation of acetonitrile and toluene was carried out both in gas-solid and in liquid-solid regimes by using commercialTiO2samples (Merck and Degussa P25). The investigation was mainly aimed to study the influence of water present in the reaction environment on the mechanism and degradation rate of two probe molecules. In gas-solid regime, the reacting mixture consisted of toluene or acetonitrile, oxygen, nitrogen, and water vapour. The main degradation product of toluene wasCO2with small amounts of benzaldehyde. In the presence of water vapour, the activity ofTiO2Merck remained stable but greatly decreased if water was absent.TiO2Degussa P25 continuously deactivated, even …

Combination of Photocatalysis and Ozonation for the treatment of Contaminated Water Containing Bromide Ions

TiO2 Nanocristalline samples used to photo-oxidize aromatic alcohols to aldehydes

Efecto de la Fotocatálisis Heterogenea y la Ozonización sobre la Oxidación del Ion Oxalato en Suspensión Acuosa de TiO2

Degradation of Lincomycin in aqueous medium: coupling of solar photocatalysis and membrane separation

Abstract The photocatalytic oxidation of a common antibiotic, the lincomycin was carried out in aqueous suspensions of polycrystalline TiO 2 Degussa P25 irradiated by sunlight. In order to improve the performance of the lincomycin degradation a hybrid system consisting of a solar photoreactor with the photocatalyst in suspension coupled with a membrane module, used to confine both photocatalyst and pollutants in the reaction environment, was tested. A preliminary study was carried out in order to determine some kinetics parameters of the drug photodegradation. The influence of initial substrate concentration on the lincomycin photooxidation rate was investigated. The photooxidation rate fol…

Extruded Expanded Polystyrene Sheets Coated by TiO2 as New Photocatalitic Materials for Foodstuffs Packaging

Nanostructured, photoactive anatase TiO2 sol prepared under very mild conditions using titanium tetraisopropoxide as the precursor is used to functionalise extruded expanded polystyrene (XPS) sheets by spray-coating resulting in stable and active materials functionalised by TiO2 nanoparticles. Photocatalytic tests of these sheets performed in a batch reactor in gas-solid system under UV irradiation show their successful activity in degrading probe molecules (2-propanol, trimethylamine and ethene). Raman spectra ensure the deposition of TiO2 as crystalline anatase phase on the polymer surface. The presence of TiO2 with respect to polymer surface can be observed in SEM images coupled to EDAX …

Optical properties of TiO2 suspensions: Influence of pH and powder concentration on mean particle size

WOS: 000250584100025

Photocatalytic degradation of dyes by using a membrane reactor

Abstract Dyes are organic compounds used in textile, food and drug industries, and their abatement represents one of the main problems in the treatment processes because generally they are very stable toxic compounds. In this work, two commercial azo-dyes, i.e. Congo Red (C32H22N6Na2O6S2) and Patent Blue (C27H31N2NaO6S2), in aqueous solution were degraded in a photocatalytic membrane reactor by using TiO2 Degussa P25 as the catalyst. Different system configurations and irradiating sources were studied, and the influence of some operational parameters such as the pressure in the membrane cell and the initial concentration of the substrates was determined. A comparison between suspended and e…

Three-Dimensional Calibration for Routine Analyses of Bromide and Nitrate Ions as Indicators of Groundwater Quality in Coastal Territories

Nitrate and bromide ions are generally considered indicators of anthropogenic pollution and seawater intrusion, respectively, in the groundwater of coastal territories. The analysis of these species is generally carried out with routine chromatographic analyses which generally afford partially merged or poorly resolved peaks. In the present paper a simple method for the correct evaluation of their concentration in water is reported. This method does not imply utilization of other instruments or technologies, only the mathematical elaboration of the data obtained from routine analysis of standard solutions containing the two species. Standard binary solutions of nitrate and bromide ions at d…

Visible-light driven oxidation of gaseous aliphatic alcohols to the corresponding carbonyls via TiO2 sensitized by a perylene derivative

Sensitized P25 TiO2 was prepared by wet impregnation with a home-prepared perylene dye, i.e., N,N?-bis(2-(1- piperazino)ethyl)-3,4,9,10-perylene-tetracarboxylic acid diimide dichloride (PZPER). Energy levels of PZPER were found to be compatible with those of TiO2 allowing fast electron transfer. The obtained catalyst has been characterized and used in the gas-phase partial oxidation of aliphatic primary and secondary alcohols, i.e., methanol, ethanol, and 2- propanol. The reaction was carried out under cut-off (?> 400 nm) simulated solar radiation in O2 atmosphere. The perylene derivative allowed a good absorbance of visible radiation thanks to its low optical energy gap (2.6 eV) which was …

A Collection of Chemical Reaction Engineering Solutions in Photocatalysis

There are problems in photocatalysis that researchers cannot disregard in a rigorous study of photocatalytic systems. The purpose of the present work is to show how chemical reaction engineering can answers to the previous questions, thus helping scientists to face researches on photocatalysis more successfull and consistenty

Selective oxidation of phenol and benzoic acid in water via home-prepared TiO2 photocatalysts: Distribution of hydroxylation products

Abstract The hydroxylation of phenol (a substrate containing an electron donor group) and of benzoic acid (a substrate containing an electron withdrawing group) has been carried out by the photocatalytic method in aqueous suspensions containing commercial or home prepared TiO2 samples. The aim of the work was to study the distribution of hydroxylation products when different photocatalysts were used and to correlate the selectivity to some physico-chemical features of the powders. The samples were characterized by X-ray diffraction, thermogravimetry, determination of crystalline phase percentage, specific surface area and zero charge point. The photoreactivity results indicate that the prod…

Photodegradation of Pharmaceuticals in Water by Using a Nanofiltration Membrane Reactor

Carbon and nitrogen-doped TiO2: preparation, characterisation and visible light photocatalytic activity

Optimization of coupled advanced oxidation processes and activated carbons for purification of salt water

Photocatalysis, ozonation and activated carbons were investigated separately and in combination as tools for the purification of polluted salt water. Coupling different processes enables to overcome many drawbacks related to the use of the single technologies and at the same time to exploit possible synergistic effects. In this work a kinetic analysis was performed for modelling the degradation of 4-nitrophenol (4NP) as a probe pollutant molecule in synthetic seawater. Thus, the optimum synergistic conditions of the three processes acting together were determined and discussed.

Aqueous selective photocatalytic oxidation of salicyl alcohol by TiO2 catalysts: Influence of some physico-chemical features

Abstract Partial photocatalytic oxidation of salicyl alcohol (2-hydroxybenzyl alcohol) to salicylaldehyde in water was investigated under environmental friendly conditions in the presence of home-prepared and commercial TiO2 (Merck and Aeroxide P25) samples under UVA irradiation. The photocatalysts were characterized by using BET, XRD, SEM and/or TEM techniques. The effects of crystallinity degree, pH (3–11) and presence of a hole trap (ethanol) on the photocatalytic activity and product selectivity were investigated. 4-Hydroxybenzyl alcohol was also used to study the influence of the position of the substituent group in the aromatic ring. High alcohols conversion and product selectivity va…

Guidelines for the Assessment and the Validation of the Rate Law of Slurry Photocatalytic Reactions

The assessment of the rate law of slurry photocatalytic reactions appears to be a hard task, mainly because in this type of reactions the average rate of reaction, which is experimentally observed in a real reactor, could be very different from the “true” (intrinsic) rate of reaction, which cannot be measured directly. In the present work, it is shown how a proper mathematical model allows the utilization of the differential and/or the integral methods of kinetic analysis. The mathematical model must take into account not only the momentum and the mass balances, but also the radiative transfer equation. However, the discrimination among different proposed kinetic laws remains difficult sinc…

Membranes for photocatalysis in wastewater treatment

Tuning The Selectivity To Aldehyde Via Ph Regulation In The Photocatalytic Oxidation Of 4-Methoxybenzyl Alcohol And Vanillyl Alcohol By Tio2 Catalysts

Abstract The influence of pH on the photocatalytic partial oxidation of 4-methoxybenzyl alcohol (MBA) and vanillyl alcohol (VA) to their corresponding aldehydes in aqueous suspension under UVA irradiation was investigated by using poorly crystalline home-prepared and crystalline commercial TiO2 (BDH, Merck and Degussa P25) photocatalysts. The results clearly show as tuning pH can strongly impart selectivity and activity to photocatalytic processes which are often quite unselective in aqueous suspensions. It was found that pH effect on reaction rate and product selectivity strongly depended on TiO2 crystallinity and substrate type. In the case of MBA oxidation, photoreactivity and selectivit…

N-Doped Anatase/Rutile Photocatalysts for the Synthesis of Aromatic Aldehydes Under Ultraviolet and Solar Irradiation

N-doped anatase/rutile photocatalysts were prepared by a sol-gel method, using TiCl4 as TiO2 precursor and urea as N-dopant source. The catalysts required a thermal treatment at temperature higher than 300 degrees C to achieve actual nitrogen doping; this treatment also allowed obtaining crystalline and hydrophobic samples. Moreover, nitrogen doping modified the surface of samples by increasing the anatase to rutile phase ratio and hydrophilicity. The catalysts were characterized by BET specific surface area, XRD, ESEM, TGA, FT-IR, DRS and XPS measurements, with particular attention to the assessment of the N-doping effect. It was found that XPS analysis should be used together with DRS and…

Photolytic and TiO2-Assisted Photodegradation of Aqueous Solutions of Tetracycline

Aqueous solutions of tetracycline were UV-irradiated in homogeneous and heterogeneous systems. Tetracycline disappeared in both systems, but the presence of TiO2 accelerated the photodegradation of the antibiotic in comparison with direct photolysis. The rate of decomposition was dependent on the concentration of tetracycline and its degradation on the surface of TiO2 can be described by means of a pseudo-first order kinetics. Photolysis involved only the photodeamination of tetracycline and a partial mineralization. Unlikely, the treatment with TiO2 and UV-light resulted in a complete mineralization of the antibiotic drug.

Membranes for photocatalysis in water and wastewater treatment

Abstract: The chapter reports the basic principles of heterogeneous photocatalysis together with a brief presentation of the types of membranes and membrane operations most widely used in this type of application. Coupling the two technologies with the aim of obtaining synergistic effects for conversion in liquid–solid systems is discussed and the relevant papers together with some case studies in pollutants abatement and reaction of synthesis are highlighted.

A method for determining optical properties of photocatalytic suspensions

Kinetic Aspects of Heterogeneous Catalytic Versus Photocatalytic Reactions

Abstract Kinetics aspects of heterogeneous catalysis and photocatalysis are reported together with the most used models developed for both fields. The chapter describes the main mechanisms involved in the different processes and the parameters used to determine their performances. A comparison of the behaviors and kinetics features of heterogeneous catalysis and photocatalysis is presented.

Home-prepared anatase, rutile, and brookite TiO2 catalysts for selective photocatalytic oxidation of p-methoxybenzyl alcohol in water: reactivity and ATR-FTIR study

Photoelectrocatalytic selective oxidation of 4-methoxybenzyl alcohol in water by TiO2 supported on titanium anodes

The photoelectrocatalytic partial oxidation of 4-methoxybenzyl alcohol in aqueous solution irradiated by near-UV light was carried out in a three-electrode batch reactor. TiO2 films were either deposited by dip-coating of a TiO2 sol onto a Ti foil and subsequent calcination or generated on Ti plates by thermal oxidation in air at 400-700 degrees C. The effects of the anode preparation method and bias potential values on conversion and selectivity to the corresponding aldehyde were investigated. The photoelectrocatalytic results were compared with the photocatalytic and electrocatalytic ones. The results indicated that no reaction occurred during the electrocatalytic experiments, whereas the…

RIDUZIONE FOTOCATALITICA DI CO2 IN SISTEMI GAS-SOLIDO IN PRESENZA DI TiO2 PURO E DROGATO CON RAME

Unexpectedly ambivalent O-2 role in the autocatalytic photooxidation of 2-methoxybenzyl alcohol in water

An unusual autocatalytic photooxidation of 2-methoxybenzyl alcohol has been observed under UV irradiation in aqueous medium. The homogeneous oxidation is catalyzed by the corresponding aldehyde that is also the main oxidation product. The trend of alcohol disappearance rate matches the typical shape of an autocatalytic process, where a crucial and ambivalent role is played by the presence of molecular oxygen. Low oxygen concentrations give rise to a zero-order reaction since the beginning of irradiation, while higher amounts of oxygen reduce the alcohol oxidation rate until the aldehyde reaches a concentration high enough to speed up the alcohol's conversion. Experiments performed by varyin…

Photocatalytic oxidation of acetonitrile in gas–solid and liquid–solid regimes

Il programma NON mi ha consentito di scaricare il PDF di questo articolo. Se lo volete ditemi come inviarlo ABSTRACT Photocatalytic degradation of acetonitrile was carried out in both gas–solid and liquid–solid regimes using two commercial TiO2 catalysts (Merck and Degussa P25). For the gas–solid regime, a continuous annular photoreactor was used. The influence on photodegradation kinetics of the gas flow rate and concentrations of acetonitrile, oxygen, and water was investigated. Acetonitrile degradation products detected in the gas phase included carbon dioxide and hydrogen cyanide. The same photoactivity was exhibited in the presence and in the absence of water vapour. The liquid–solid reg…