Capacità sequestrante di acido alginico e fulvico nei confronti di composti di triorganostagno(IV)

Multi-doped Brookite-Prevalent TiO2 Photocatalyst with Enhanced Activity in the Visible Light

© 2018 Springer Science+Business Media, LLC, part of Springer Nature Abstract: Enabling solar and/or visible light-driven photocatalysis is a crucial step to access innovative applications in environmental science and sustainable energy. Titanium dioxide is the most used photocatalyst because of its low cost and toxicity, however it is also limitedly active under visible light irradiation due to its wide band gap. Among its polymorphs, brookite holds promising optoelectronic properties for visible light photocatalysis, which have to the best of our knowledge been limitedly exploited. Here, a C,S,N-doped brookite-based TiO2has been prepared via a rapid one-pot sol–gel synthesis. Besides subs…

Sequestering ability of polyaminopolycarboxylic ligands towards dioxouranium(VI) cation

Abstract In the present paper, some results of an investigation (at t = 25 °C by potentiometry, ISE-H+ glass electrode) on the sequestering ability of five different polyaminopolycarboxylic ligands [Nitrilotriacetate (NTA), ethylenediamine-N,N,N′,N′-tetraacetate (EDTA), ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetate (EGTA), diethylenetriamine-N,N,N′,N″,N″-pentaacetate (DTPA), triethylenetetraamine-N,N,N′,N″,N′′′,N′′′-hexaacetate (TTHA)] towards dioxouranium(VI) cation in sodium chloride aqueous solutions, at I = 0.7 mol L−1 are reported. Calculations performed on potentiometric data gave evidence of the formation of the following species (log β in parenthesis): UO2(NTA)H0 (12…

Protein aggregates for water purification

Water pollution is the contamination of water bodies including lakes, rivers, oceans and it is a leading global risk factor for illness and death for people, plants and living organisms. A principal source of water pollution is industry, from which increasing amounts of toxic pollutants are released including heavy metals such as cobalt, lead and copper. Today various technologies for purifying contaminated water can be applied, a lot of them being typically expensive, ion specific and characterised by low efficiency. For these reason, the search of new biocompatible materials with increased capabilities is strongly needed.Protein aggregates have already revealed their potential as environm…

Sequestration of organometallic compounds by natural organic matter. binding of trimethyltin(IV) by fulvic and alginic acids

The binding capacity of fulvic and alginic acids towards trimethyl tin(IV) cation was quantitatively determined in order to evaluate the sequestering ability of toxic organometallic compounds by natural organic matter. Investigations were performed in the pH range of natural waters (5–8.5) where the carboxylate groups, largely present in both sequestering agents, are the main binding sites. A chemical interaction model, according to which both the protonation of polyelectrolyte ligands and the hydrolysis of the organotin cation in NaCl aqueous solution were considered, was used to define the speciation of the systems under investigation. Measurements performed at different ionic strength va…

Thermodynamics of interaction between risedronic acid and metal cations: investigations in solution and in the solid state

Risedronic acid (see Figure 1) belongs to the class of biphosphonates (BP), widely used in the medical field to treat bone disorders. Bisphosphonates (BPs, e.g., alendronate, risedronate, and ibandronate) help to maintain bone mass, to inhibit osteoclast-mediated bone resorption, and to reduce the risk of both vertebral and non-vertebral fractures. The clinical efficacy of BPs is mainly based on two key properties: their capacity to strongly bind hydroxyapatite crystals of bone, and their inhibitory effects on osteoclast precursors and mature osteoclasts. Interaction of risedronate with metal cations is poorly investigated. Qualitatively, it is indicated that adsorption of risedronate is in…

INTERAZIONE DI COMPOSTI DI METILSTAGNO(IV) CON LEGANTI CARBOSSILICI

Lead(II) ions adsorption onto amyloid particulates: An in depth study

The production of new cost-effective biocompatible sorbent sustainable materials, with natural origins, able to remove heavy metals from water resources is nowadays highly desirable in order to reduce pollution and increase clean water availability. In this context, self-assembled protein materials with amyloid structures seem to have a great potential as natural platform for a broader development of highly-tunable structures. In this work we show how protein particulates, a generic form of protein aggregates, with spherical micro sized shape can be used as adsorbents of Pb2+ ions from aqueous solution. The effect of pH, ionic medium, ionic strength and temperature of the metal ion solution…

Sequestering ability of some chelating agents towards methylmercury(II).

A study on the interactions between CH3Hg+ and some S, N and O donor ligands (2-mercaptopropanoic acid (thiolactic acid (H2 TLA)), 3-mercaptopropanoic acid (H2 MPA), 2-mercaptosuccinic acid (thiomalic acid (H3 TMA)), d,l-penicillamine (H2 PSH), l-cysteine (H2 CYS), glutathione (H3 GSH), N,N′-bis(3-aminopropyl)-1-4-diaminobutane (spermine (SPER)), 1,2,3,4,5,6-benzenehexacarboxylic acid (mellitic acid (H6 MLT)) and ethylenediaminetetraacetic acid (H4 EDTA)) is reported. The speciation models in aqueous solution and the possible structures of the complexes formed are discussed on the basis of potentiometric, calorimetric, UV spectrophotometric and electrospray mass spectrometric results. For t…

3D MICROSIZED PROTEIN AMYLOID PARTICULATES AS EFFECTIVE BIOADSORBERS FOR Pb2+ IONS

The production of new cost-effective biocompatible sorbent sustainable materials, with natural origins, able to remove heavy metals from water resources is nowadays highly desirable in order to reduce pollution and increase clean water availability. In this context, self-assembled protein materials with highly ordered amyloid structures, stabilised by H-bonds, seems to have a great potential as natural platform for a broader development of highly-tunable structures. By suitably varying solution conditions it is possible to tune aggregate size, surface area and morphologies as well as their physicochemical (hydrophobicity, hydrophilicity, swelling/deswelling properties) and mechanical proper…

Sequestration of Pd2+ by polyamino-polycarboxylic ligands

The increase of the worldwide demand of “Platinum group elements” (PGE) for application in several fields such as industry, medicine, jewellery and, especially, in catalyst converter production, caused a noticeable increasing of PGE concentration in the environment. Though palladium, among the anthropogenic PGE, is not the most abundant one, it is the most hazardous since it undergoes easily and quickly oxidation to palladium(II) when in contact with soils, with a consequent increase of its mobility in the environment. The presence of complexing agents, which form soluble complex species with palladium(II), favours the mobility of the ion with an increase of its availability to plants, anim…

Modeling ATP protonation and activity coefficients in NaClaq and KClaq by SIT and Pitzer equations.

Abstract The acid–base properties of Adenosine 5′-triphosphate (ATP) in NaCl and KCl aqueous solutions at different ionic strengths (0  I  / mol L − 1  ≤ 5 for NaCl aq , 0  I  / mol L − 1  ≤ 3 for KCl aq ) and at t  = 25 °C were investigated. A selection of literature data on ATP protonation constants and on activity isopiestic coefficients was performed, together with new potentiometric measurements (by ISE-H + , glass electrode). Both literature and new experimental data were used to model the dependence on ionic strength and ionic medium of ATP protonation by SIT (Specific ion Interaction Theory) and Pitzer equations. In addition to values of first and second ATP protonation constants in…

Complexes of dioxouranium(VI) ion with glutamic and aspartic acids in NaCl aqueous solution

LEAD(II) AND CADMIUM(II) REMOVAL FROM AQUEOUS SOLUTIONS USING HAZELNUT AND ALMOND SHELLS SORBENT MATERIALS

Removal of toxic metal ions from natural and waste waters is of great importance for the health of living organisms and for environmental protection. Alternatively to the conventional chemical treatments, such as precipitation, reverse osmosis, etc, biosorption shows a growing interest for toxic metal ions removal from contaminated aqueous solutions. The sorption ability of every type of biomass towards metal ions depends on many variables that characterize the solution. Among these, the ionic strength (I) is one of the most important and cannot be neglected during an accurate adsorption study. For this reason and with the aim of quantitatively define the influence of I, here are reported t…

Palladium(II) Complexes of Aminopolycarboxylic Ligands in Aqueous Solution

Thebindingcapacityof fiveaminopolycarboxylicligands(APCs)(nitrilotriacetate(NTA),ethylenediamine-N,N,N 0 , N 0 -tetraacetate (EDTA), (S,S)-ethylenediamine-N,N 0 -disuccinic acid (S,S-EDDS), diethylenetriamine-N,N,N 0 ,N 00 ,N 00 -pentaacetate (DTPA), and triethylenetetraamine-N,N,N 0 ,N 00 ,N 000 ,N 000 -hexaacetate (TTHA)) toward the palladium(II) ion was studied by potentiometric titrations (ISE-H + electrode) in NaNO3 and in NaClO4/NaI (at different molar ratios) solutions and by spectrophotometric titrations (only in NaClO4), at I = 0.1 mol 3 kg � 1 and at T = 298.15 K. The high stability of Pd 2+ -complexones species inhibits the formation of sparingly soluble hydroxo species until pH …

Solubility and acid-base properties and activity coefficients of chitosan in different ionic media and at different ionic strengths, at T=25°C

Studies on the acid-base properties and solubility of a polyammonium polyelectrolyte (chitosan) with different molecular weights (MW 310 and 50 kDa), were performed at T=25 °C, in the pH range 2.5–7. The protonation of chitosan was investigated by potentiometry ([H+]-glass electrode) in NaCl, NaNO3 and mixed NaNO3+Na2SO4 ionic media, at different ionic strengths. Protonation constants were calculated as a function of dissociation degree α by means of two different models, namely, a simple linear model and the modified Henderson–Hasselbalch equation. Experimental data were also fitted using a model independent of α (Diprotic-like model), according to which the acid-base properties can be sim…

Evaluation of adsorption ability of Cyclodextrin-Calixarene Nanosponges towards Pb2+ ion in aqueous solution

Abstract Different cyclodextrin-calixarene nanosponges (CyCaNSs) have been characterized by means of FFC-NMR relaxometry, and used as sorbents to remove Pb2+ ions from aqueous solutions. Considering that the removal treatments may involve polluted waters with different characteristics, the adsorption experiments were performed on solutions without and with the addition of background salts, under different operational conditions. The adsorption abilities and affinities of the nanosponges towards Pb2+ ions were investigated by measuring the metal ion concentration by means of Inductively Coupled Plasma Emission Spectroscopy (ICP-OES) and Differential Pulse Anodic Stripping Voltammetry (DP-ASV…

Recovery of magnesium hydroxide from real bitterns

Risedronate complexes with Mg2+, Zn2+, Pb2+, and Cu2+: Species thermodynamics and sequestering ability in NaCl(aq) at different ionic strengths and at T = 298.15 K

Abstract In this paper, potentiometry and calorimetry were used to determine the thermodynamics of interaction between risedronate and four bivalent metal cations, namely: Mg2+, Zn2+, Pb2+, and Cu2+ in aqueous NaCl solutions at different ionic strengths and at T = 298.15 K. The data analysis allowed us to ascertain that the main species formed were the MLH2, MLH, ML and M2L; however scarcely soluble species precipitated at acidic pH values, between 4 and 7 depending on the metal cation involved, probably due to the formation of the neutral M2L(s) species. Comparison of the stability constants with other similar ligands suggests that metal complexation occurs through the phosphonate with an …

Interaction of UO2(2+) with ATP in aqueous ionic media.

Interaction of dioxouranium(VI) (uranyl) ion with ATP was studied by ligand/proton and metal/hydroxide displacement technique, at very low ionic strength and at I=0.15 mol L(-1), in aqueous Me4NCl and NaCl solutions, at t=25 degrees C. Measurements were carried out in the pH range 3-8.5, before the formation of precipitate. Computer analysis allowed us to find the quite stable species UO2(ATP)H2(0), UO2(ATP)H-, UO2(ATP)2-, UO2(ATP)2(6-), UO2(ATP)2H2(4-) and UO2(ATP)(OH)3- whose formation constants are (at I=0 mol L(-1)) logbeta(112)=18.21, logbeta(111)=14.70, logbeta(110)=9.14, logbeta(120)=12.84, logbeta(122)=24.82, and logbeta(11-1)=2.09, respectively. Different values were obtained in th…

Modeling the acid-base properties of molybdate(VI) in different ionic media, ionic strengths and temperatures, by EDH, SIT and Pitzer equations

This paper reports the results of a study on the determination of the protonation constants of MoO42 −, in NaClaq, NaNO3aq, KClaq, at different ionic strengths (0 < I/mol dm− 3 ≤ 5.0 in NaClaq, 0 < I/mol dm− 3 ≤ 3.0 in NaNO3aq and KClaq) and temperatures (278.15 ≤ T/K ≤ 318.15 in NaClaq, only 298.15 K in NaNO3aq and KClaq), by potentiometric (ISE-H+ glass electrode) and spectrophotometric (UV/Vis) titrations. After a critical analysis of results and literature findings, the proposed speciation model takes into account the formation of two monomeric and four heptameric species, namely: MoO4H−, MoO4H2, (MoO4)7H86 −, (MoO4)7H95 −, (MoO4)7H104 − and (MoO4)7H113 −. Due to the complexity of…

Palladium(II) sequestration by phytate in aqueous solution. Speciation analysis and ionic medium effects.

Environmental context.In the last 20 years, the demand for palladium and other platinum-group elements has intensified, causing a significant increase in their concentration in the environment, with particular accumulation in urban areas. Knowledge about Pd2+ speciation in aqueous media is fundamental for the understanding of its biological and environmental activity in contaminated areas. Phytic acid appears to be a good sequestering agent towards Pd2+ under various conditions, indicating its potential use in the remediation of contaminated sites. Abstract. Palladium(II) speciation in the presence of phytate (Phy12–) was studied by H+ ion selective electrode (ISE) potentiometry at 25°C in…

Complex species formation of Cu and Cd metal ions with polyacrylate, polymethacrylate and alginate ligands. Potentiometric investigation by ISE-H+ and Ise-Me2+ electrodes

Thermodynamic and spectroscopic study of the binding of dimethyltin(IV) by citrate at 25°C

Thermodynamic (potentiometric and calorimetric) and spectroscopic ( 1 H NMR, 119 Sn Mossbauer) studies were performed in aqueous solution in order to characterize the interaction of dimethyltin(IV) cation with citrate ligand. Six species {(CH 3 ) 2 Sn(cit) - ; [(CH 3 ) 2 Sn] 2 (cit) 2 2- ; (CH 3 ) 2 Sn(cit)H 0 ; (CH 3 ) 2 Sn(cit)OH 2- ; [(CH 3 ) 2 Sn] 2 (cit)OH 0 ; [(CH 3 ) 2 Sn] 2 (cit)(OH) 2 - } were found. All the species formed in this system are quite stable and formation percentages are fairly high. For example, at pH = 7.5 and C (CH3)2Sn = C cit = 10 mmol l -1 , E% for [(CH 3 ) 2 Sn] 2 (cit)(OH) 2 - and (CH 3 ) 2 Sn(cit)OH 2- species reaches 65%. Overall thermodynamic parameters obta…

Enhancement of adsorption ability of calcium alginate gel beads towards Pd(II) ion. A kinetic and equilibrium study on hybrid Laponite and Montmorillonite–alginate gel beads

Abstract The adsorption ability of hybrid Montmorillonite and Laponite–calcium alginate gel beads towards Pd 2 + ion was studied in the pH range 2–4, in pure water and in aqueous NaCl solution at I = 0.01 mol L − 1 and T = 25 °C. The pseudo second order kinetic equation and the Langmuir and Freundlich isotherms were used to fit the kinetic and thermodynamic experimental data. A comparison of the results already published on the adsorption capacity of calcium alginate gel beads at the same experimental conditions was made. Enhancement of palladium(II) adsorption by alginate beads with the addition of the two clay minerals was obtained, with increments higher than 50% of Pd(II) ion recovered/…

Understanding the Solution Behavior of Epinephrine in the Presence of Toxic Cations: A Thermodynamic Investigation in Different Experimental Conditions

The interactions of epinephrine ((R)-(&minus

The solution behavior of dopamine in the presence of mono and divalent cations: A thermodynamic investigation in different experimental conditions

The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop-)] with methylmercury(II) (CH3Hg+), magnesium(II), calcium(II), and tin(II) were studied in NaCl(aq) at different ionic strengths and temperatures. Different speciation models were obtained, mainly characterized by mononuclear species. Only for Sn2+ we observed the formation of binuclear complexes (M2L2 and M2LOH (charge omitted for simplicity)

Capacità sequestrante di leganti poliammino policarbossilici nei confronti dello ione uranile

Evaluation of the sequestering ability of different complexones towards Ag+ ion

Abstract The interaction between Ag+ cation and different ligands was evaluated as a function of temperature and ionic strength by means of potentiometric techniques. Six aminopolycarboxylic (APCs) and aminopolyphosphonic (APPs) ligands were chosen, namely four APCs: nitrilotriacetic acid (NTA), ethylene-glycol-bis(2-aminoethylether)-N,N,N’,N’-tetraacetic acid (EGTA), ethylenediamine-N,N,N’,N’-tetraacetate (EDTA) and diethylenetriamine-N,N,N’,N”,N”-pentaacetic acid (DTPA)] and two APPs: [(1-hydroxyethane-1,1-diyl)bis(phosphonic acid) (HEDP) and [[(Phosphonomethyl)imino]bis[2,1-ethanediylnitrilobis(methylene)]] tetrakis-phosphonic acid (DTPP). Different mononuclear species with general formu…

Effect of pH Variations on the Properties of Cyclodextrin‐Calixarene Nanosponges

The pH-responsive properties of cyclodextrin-calixarene nanosponge co-polymeric materials have been investigated. In particular, ISE-H+ potentiometric titrations were carried out in order to evaluate the acid-base properties and the actual amount of ionizable sites present in the materials. Moreover, the relevant pH-dependent adsorption abilities were evaluated towards a set of selected model organic pollutant molecules by means of adsorption tests and by studying the corresponding adsorption isotherms. The latter ones could be suitably described by means of the Freundlich model. The whole of the experimental results enabled us to clarify some general aspects of the microscopic behavior of …

Speciation Studies of Bifunctional 3-Hydroxy-4-Pyridinone Ligands in the Presence of Zn2+ at Different Ionic Strengths and Temperatures

The acid&ndash

Mercury(II) removal from aqueous solution by sorption onto alginate, pectate and polygalacturonate calcium gel beads. A kinetic and speciation based equilibrium study

Abstract Gel beads of calcium alginate, pectate and polygalacturonate salts have been tested as sorbent materials for mercury(II) removal from aqueous solutions. Physico-chemical properties of gel beads, defined by SEM–EDX, TGA and texture and density analysis, were correlated with gel beads sorption capacity towards Hg 2+ ion. A speciation study in aqueous solution was carried out to define the strength of interaction of mercury ion with the polymers investigated and to assess the more suitable experimental conditions to achieve the best effectiveness of Hg 2+ sorption by gel beads. On the basis of the speciation study, pH values in the 3–5.5 pH range were considered appropriated for mercu…

Activated Biochar From Posidonia Oceanica. A New Adsorbent Material of Hydrocarbons from Wastewater

Environmental pollution by petroleum derivatives is a very current topic. In particular, low concentration of this kind of pollutants can seriously compromise the life of animals and plants of aquatic ecosystems (Yu, 2017). The current legislation provides that bilgewater, wastewater produced by boats, can be discharged directly into the sea only if the total hydrocarbon concentration not exceds 15 mg L-1. In this work, new activated carbons were tested as adsorbent materials of oil / hydrocarbons from wastewater. Moreover, an instrumental technique able to quickly measure the required low hydrocarbons concentration is also proposed. The new activated carbons were obtained from bio-oil prod…

Palladium nanoparticles immobilized on halloysite nanotubes covered by a multilayer network for catalytic applications

The synthesis of pure fine chemicals for industrial purposes is one of the most attractive challenges of chemical research. The use of catalytic pathways mediated by palladium nanoparticles (PdNPs) for C-C bond formation is a useful way to obtain these kinds of compounds. To achieve this objective, the PdNPs can be efficiently loaded on a functionalized natural nanostructured support such as halloysite nanotubes (HNTs). Hybrid materials based on thiol functionalized halloysite nanotubes and highly cross-linked imidazolium salts were successfully developed and used for the stabilization of PdNPs. The HNT/Pd hybrids were thoroughly characterized from a physico-chemical point of view and teste…

HYDROCARBONS REMOVAL FROM BILGE WATER BY ADSORPTION ONTO ACTIVATED BIOCHAR FROM POSIDONIA OCEANICA

The normal operations carried out on the boats during navigation generate waste waters such as oily bilge water. The latter is the aqueous mixture of potential pollutants of different origins and types: oily fluids, lubricants and greases, cleaning fluids and other wastes that accumulate in the lower part of the vessel [1,2]. The current legislation provides that they can be discharge directly into the sea if the concentrations of some components are below the expected limits. In particular, with regard to oil / hydrocarbons contamination, the current regulatory limit is 15 mg L-1 of total hydrocarbons. The present work starts from a public/private partnership funded by a grant of the Minis…

Functionalized Halloysite for enhanced removal of toxic metal ions from aqueous solutions

During the last years several nanomaterials have been extensively used in the heavy metal ions removal from aqueous solutions. Among them, clay minerals have gathered particular interest owing to their unique features (e.g., high specific surface area, low toxicity and natural availability at low price). Halloysite nanotubes (Hal) are particular clay minerals with a predominantly hollow tubular structure. In this work Hal and their derivatives, Hal-NH2 and Hal-SH, were used as adsorbent materials of lead(II) and mercury(II) ions from aqueous solutions. The adsorption ability of clay nanomaterials towards toxic metal ions has been studied takeing into account important variables of the metal…

Sequestration of organomettalic compounds by synthetic and naturally occuring polycarboxylate ligands. Binding of monomethylmercury(II) by polyacrylic and alginic acids.

The sequestering capacity of synthetic and naturally occurring polycarboxylate ligands towards mono- methylmercury(II) was evaluated by stability quantitative data on the interaction of CH3Hgþ with different molecular weight synthetic polyacrylates (2 and 20 kDa average M.wt) and alginate (70– 100 kDa) extracted from brown algae Macrocystis pyrifera. The influence of ionic medium was evaluated by measurements on the CH3Hgþ-polyacrylate systems in NaNO3 medium at different ionic strengths (0.10, 0.25, 0.50 and 0.75mol Lÿ1), and a Debye–Hu¨ ckel type equation was used for the dependence of complex formation constants on ionic strength. Measurements on the CH3Hgþ - alginate system were carried…

Formation and Stability of Cadmium(II)/Phytate Complexes by Different Electrochemical Techniques. Critical Analysis of Results

In the present work the stability constants of various cadmium(II)/phytate (Phy) species were determined at T = 298.15 K in NaNO3(aq) at I = 0.1 mol·L−1 by DP-ASV (Differential Pulse Anodic Stripping Voltammetry) and by potentiometric titrations using an ISE-Cd2+. Cyclic voltammograms were also recorded to check the electrochemical behavior of cadmium in the presence of phytate. The results were analyzed together with previous data determined by ISE-H+ measurements. Data obtained were used to provide an exhaustive speciation scheme for the phytate/cadmium(II) system at different conditions, as well as a comprehensive representation of the binding ability of phytate toward cadmium(II). Diffe…

Protonation Constants of Halloysite Clay Nanotubes

Halloysite is one of the most interesting nano-structured clay materials. It is similar to kaolin but has a hollow tubular structure that can be attributable to particular crystallization conditions. Typically, halloysite nanotubes (HNTs) are formed by 15 – 20 aluminosilicate layers, has a length of 1 ± 0.5 μm and inner and outer diameters of 1 - 30 and 30 - 50 nm, respectively [1,2]. In each layer the SiOH and the AlOH groups are disposed on the external and the internal surfaces, respectively. The particular structure of HNTs makes this kind of material very useful for different purposes in several fields. Among the various applications, worth of mention are: i) their use as additive for …

Analisi critica dei parametri termodinamici del sistema acido fitico/Cadmio(II) determinati con differenti tecniche elettrochimiche

Sequestering ability of landfill leachate towards toxic metal ions

The great part of municipal solid wastes is worldwide stored in sanitary landfills. The interaction of organic and inorganic wastes with rainwater produces in the landfill a leachate of extremely variable composition. It depends on several variables such as the type of wastes, the age of landfill, the pH, the redox potential, etc [1-2]. Four are the recognized categories of pollutants in landfill leachate: inorganic macrocomponents, dissolved organic matter (DOM), heavy metals and xenobiotic organic compounds [3]. In particular, heavy metals (arsenic, cadmium, copper, lead, mercury, etc.) are usually present at concentration of few ppb and up to some ppm. A variable but consistent fraction …

Sequestration of alkyltin(IV) cations by complexation with amino-polycarboxylic chelating agents

Abstract The binding capacity of four amino-polycarboxylic ligands (APCs) [nitrilotriacetate (NTA), ethylenediamine- N , N , N′ , N′ -tetraacetate (EDTA), (S,S)-ethylenediamine- N , N ′-disuccinic acid (S,S-EDDS) and diethylenetriamine- N , N , N′ , N″ , N″ -pentaacetate (DTPA)] towards mono-, di- and tri-alkyltin(IV) cations [(CH 3 )Sn 3 + , (CH 3 ) 2 Sn 2 + , (C 2 H 5 ) 2 Sn 2 + , (CH 3 ) 3 Sn + or (C 2 H 5 ) 3 Sn + ] was studied, in aqueous solutions, by ISE-H + potentiometry, at I  = 0.1 mol L − 1 (NaCl) and at T  = 298.15 K. In all the systems R x Sn (4 − x)+  − APC (R = CH 3 or C 2 H 5 ) a strong 1:1 species is formed together with protonated, hydroxo and dinuclear complexes. The valu…

Acid−Base Properties of Synthetic and Natural Polyelectrolytes: Experimental Results and Models for the Dependence on Different Aqueous Media

Protonation constants of several natural and synthetic humates and fulvates were determined by ISE-H+ potentiometry in different ionic media (alkali metal halides and tetraethylammonium iodide) at different ionic strengths and T ) 298.15 K. Experimental data obtained in previous studies of different synthetic (polyacrylates, polymethacrylates, polyacrylate-co-maleate) and naturally occurring (alginate, humic substances) polycarboxylates were also taken into account in the general analysis of acid-base properties of polyelectrolytes. Protonation constants were expressed as a function of the dissociation degree (R) using three models, namely, a simple linear model, the Ho¨gfeldt three-paramet…

Special issue “chemical speciation of organic and inorganic components of environmental and biological interest in natural fluids: Behaviour, interaction and sequestration”

Several different definitions were in the past proposed to describe the term chemical speciation, and some of them were accepted from the scientific community [...]

Advances in the study of phytate-cation interactions

Complex species formation in chitosan-phosphate and chitosan-nucleotide systems in NaCl aqueous solution.

CHEMICAL CHARACTERIZATION OF ANCIENT LITURGICAL VESTMENT (CHASUBLE) BY ICP-OES

Functionalized halloysite nanotubes for enhanced removal of lead(II) ions from aqueous solutions

In this study, environmental friendly halloysite nanotubes and their amino derivatives were used as adsorbent materials for lead(II) ions. The adsorption ability of both nanomaterials towards Pb2+ ions has been studied in NaClaq, at I = 0.1 mol L−1, in the pH range 3–6. Moreover, the effect of ionic strength on the adsorption process was evaluated at the pH of maximum efficiency of the adsorbent materials. Kinetic and equilibrium experiments were carried out by using the Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique to check the metal ion concentration in solution after contact with the two adsorbents. Different isotherm and kinetic equations were used to fit the experi…

Modelling the dependence on medium and ionic strength of molybdate acidbase properties, and its interactions with phytate

The importance of molybdenum from a biological, environmental and technological point of view is very well known since many decades [15]. In particular, it is mainly present in aqueous solutions as molybdate (MoO42), which is the biologically active form, entering in the cells by active transport systems. Though molybdate is the major species in neutral to basic pH conditions, at lower pH it undergoes protonation and, chiefly, polymerization, even at millimolar concentration levels [2]. Consequently, the modelling of its speciation and acidbase properties is not very simple, as demonstrated by the nonhomogeneity of available literature data. In this light, our group has started a systematic…

The Effect of Metal Cations on the Aqueous Behavior of Dopamine. Thermodynamic Investigation of the Binary and Ternary Interactions with Cd2+, Cu2+ and UO22+ in NaCl at Different Ionic Strengths and Temperatures

The interactions of dopamine [2-(3,4-Dihydroxyphenyl)ethylamine, (Dop−)] with cadmium(II), copper(II) and uranyl(VI) were studied in NaCl(aq) at different ionic strengths (0 ≤ I/mol dm−3 ≤ 1.0) and temperatures (288.15 ≤ T/K ≤ 318.15). From the elaboration of the experimental data, it was found that the speciation models are featured by species of different stoichiometry and stability. In particular for cadmium, the formation of only MLH, ML and ML2 (M = Cd2+; L = dopamine) species was obtained. For uranyl(VI) (UO22+), the speciation scheme is influenced by the use of UO2(acetate)2 salt as a chemical; in this case, the formation of ML2, MLOH and the ternary MLAc (Ac = acetate) species in a …

Thermodynamics of Proton Binding of Halloysite Nanotubes

In this paper, new information on physical and chemical properties of the widely used nanostructured Halloysite mineral are reported. Given that the Halloysite has a tubular structure formed by a variable number of wrapped layers containing Si-OH and Al-OH groups, their proton binding affinity was measured at different ionic strengths and ionic media by means of potentiometric measurements in heterogeneous phase. One protonation constant for the Si-OH groups and two for the Al-OH groups were determined. The protonation constant values increase with increasing of the ionic strength in all the ionic media. This suggests that the presence of a background electrolyte stabilizes the protonated s…

Clay nanotubes for designing eco-compatible smart materials

Studio della capacità sequestrante della biomassa nei confronti dello ione rame (II)

Acid-base properties and sequestering abilities towards toxic metal ions of cyclodextrin-calixarene co-polymers

Smart materials with stimuli-responsive properties represent an interesting research area considering both their potential applications and the conceptual issues implied. They might be successfully employed in various fields, such as drug carrier/delivery devices to sensors, environment remediation, active packaging [1-2]. In this contest, we have recently synthesized various pH-responsive pre- and post-modified cyclodextrin-calixarene nanosponges (CyCaNSs) with 1,2,3-triazole linker units (ACNSs) able to vary their sequestering abilities towards organic and inorganic compounds. In particular, their adsorption properties were varied changing the molar ratio between the co-monomers, and the …

Complex formation of copper(II) and cadmium(II) with pectin and polygalacturonic acid in aqueous solution. An ISE-H + and ISE-Me 2+ electrochemical study

The acid-base properties of pectin and its ability to complex with copper(II) or cadmium(II) were quantitatively determined in order to define the ability of this natural polyelectrolyte to sequester metal ions. Potentiometric measurements carried out at different ionic strengths (0.1 - 0.7 mol L-1, in Na+ ionic medium) allowed us to define the acid-base properties of pectin together with the dependence of the protonation constants on ionic strength and to calculate the protonation constant at infinite dilution. The formation of complex species between pectin and copper(II) or cadmium(II) was investigated potentiometrically (using H+, Cu2+ and Cd2+ Ion Selective Electrodes, ISEs) in NaNO3 a…

Interactions of Dioxouranium(VI) with Amines in Aqueous Solution

The interaction of the dioxouranium(VI) ion with five low molecular weight polyamines (ethylenediamine, putrescine, cadaverine, spermidine, and spermine) and with poly(allyl)amine (15 kDa) was studied potentiometrically (ISE-H + glass electrode) at T ) 298.15 K. Investigations were carried out in NaNO3 ionic medium, at I ) 0.1 mol · L -1 (and 0.5 mol · L -1 for poly(allyl)amine only), in the pH range 3.5 to 5.5, before the formation of uranyl insoluble species. The results gave evidence for the formation of two species, namely, UO2L 2+ and UO2L(OH) + for the diamine systems (ethylenediamine, putrescine, cadaverine), UO2L 2+ and UO2LH 3+ for spermidine, and UO2LH 3+ and UO2LH2 4+ for spermin…

Use of amino–polycarboxylic chelating agents for the sequestration of (CH3)Hg+ ion in aqueous solution

Among the mercury organic derivatives, mono-methylmercury (MMHg) is by far the most toxic form of mercury because of its high capacity to enter biological membranes and accumulate in living organisms [1], as shown by the biomagnification factors: ~104 from water to edible shell-fish (mussels), and 106 –108 from water to big fishes (e.g. tuna fish) at the top of food chain [2]. The presence of complexing agents in the environment, which form soluble complex species with MMHg, favours the mobility of the ion in the aquatic ecosystems. Among anthropogenic complexing molecules, the most used ones are the aminopolycarboxylic chelating agents (usually called with the acronym APC) which are employ…

Sorption of Pd(II) ion by calcium alginate gel beads at different chloride concentrations and pH. A kinetic and equilibrium study

Abstract A kinetic and thermodynamic study on the sorption ability of calcium alginate gel beads towards Pd(II) ion was made in aqueous solution at different pH and chloride concentrations. The experimental conditions adopted in the sorption experiments were established on the basis of a speciation study on the Pd 2+ -AA system in which all the side reactions, such as the hydrolysis of Pd(II), the protonation of alginate and the interactions of the ligand and the metal ion with ions of ionic medium were taken into account. In the pH range 2–5 and at chloride concentration in the range 0 ⩽ C Cl - /mmol L −1  ⩽ 10 the gel beads showed good sorption ability towards Pd(II) ion as confirmed by k…

Studio della sequestrazione dello ione cadmio da parte di leganti s-donatori

La presenza in natura del cadmio è dovuta principalmente al suo uso in svariati settori dell’industria [1] ed in misura minore al suo rilascio durante i processi di demineralizzazione delle rocce. La elevata tossicità dello ione cadmio [2] nei confronti degli esseri viventi, animali e vegetali, è dovuta alla elevata affinità che questo catione mostra nei confronti della maggior parte dei gruppi leganti presenti nelle molecole biologicamente attive. In particolare i leganti tiolici presenti nei residui amminoacidici, soprattutto quelli a basso peso molecolare rappresentano i vettori principali attraverso il quale avvengono i fenomeni di trasporto e di distribuzione del cadmio nell’organismo …

Interazione di UO22+, Cd2+, Zn2+, Cu2+ con acido poliacrilico ed acidi fulvici

The importance of chemical speciation studies in the characterization of natural waters

Biochar from byproduct to high value added material – A new adsorbent for toxic metal ions removal from aqueous solutions

Abstract An activated biochar coming from pyrolysis of dead Posidonia oceanica residues has been tested as adsorbent material for Cd2+, Pb2+ and Cu2+ ions. The biomass, the activated and the non activated biochars were previously characterized by using several instrumental techniques. The pH of metal ion solution in kinetic and thermodynamic adsorption experiments was fixed at 5 whilst, the dependence on ionic medium, ionic strength and temperature have been evaluated carrying out batch experiments at different experimental conditions. Differential Pulse Anodic Stripping Voltammetry and Inductively Coupled Plasma Optical Emission Spectroscopy have been used to measure the metal ion concentr…

Sequestration of (CH3)Hg+ by amino‐polycarboxylic chelating agents

Abstract The speciation of mono-methylmercury(II) cation (MeHg+) in the presence of Nitrilotriacetate (NTA), Ethylenediamine-N,N,N′,N′-tetraacetate (EDTA), diethylenetriamine-N,N,N′,N″,N″-pentaacetate (DTPA) and (S,S)- Ethylenediamine-N,N′-disuccinic acid (S,S-EDDS) was investigated at I = 0.1 mol L− 1 (NaCl) with the aim to assess a trend of sequestering capacity of the amino‐polycarboxylic (APCs) ligand class towards this cation in aqueous solution. The results obtained gave evidence for the formation of a mononuclear [MeHg(APC)] complex species, differently protonated MeHg(HiL) species (i = 1 to 3, depending on the APC considered), a mixed hydroxo species [MeHg(APC)(OH)] and a binuclear …

A study on the acid-base properties of pectin and poly-galacturonic acid

Binding of fluoride and carbonate by open chain polyammonium cations

The formation of open chain polyammonium cation-fluoride and -carbonate complexes was studied by potentiometric and calorimetric techniques at t=25 degrees C. Several species of H(i)AL (A=amine; L=F(-), CO(3)(2-)) are formed in both systems with a mean stability log K=1.0zeta (zeta=|z(anion)xz(cation)|) and log K=2.0zeta for fluoride and carbonate, respectively. The comparison with analogous systems (chloride and acetate for fluoride and hydrogenphosphate, sulfate and malonate for carbonate) showed that fluoride and carbonate form the most stable species with open chain polyammonium cations, among low molecular weight anions. The N-alkyl substitution does not play negligible role in the sta…

Hydrolysis of dioxouranium(VI): a calorimetric study in NaClaq and NaClO4aq, at 25°C

Abstract We report the results of a calorimetric study on the hydrolysis of UO 2 2+ in different ionic media (NaClO 4 aq , NaCl aq ) at 25 °C. Experiments in NaCl were performed at different ionic strength, at I ≤1 mol l −1 . The species considered in both ionic media were UO 2 (OH) + , (UO 2 ) 2 (OH) 2 2+ and (UO 2 ) 3 (OH) 5 + , and in addition (UO 2 ) 3 (OH) 4 2+ and (UO 2 ) 3 (OH) 7 − in NaCl aq . The dependence on ionic strength of enthalpy changes in NaCl aq was expressed by the simple linear equation Δ H pq =Δ H ° pq + aI 1/2 ( a , empirical parameter). Comparison with literature findings is given and some recommended values are reported.

Uranium(VI) sequestration by polyacrylic and fulvic acids in aqueous solution

Stability data on the formation of dioxouranium(VI) species with polyacrylic (PAA) and fulvic acids (FA) are reported with the aim to define quantitatively the sequestering capacity of these high molecular weight synthetic and naturally occurring ligands toward uranium(VI), in aqueous solution. Investigations were carried out at t = 25 °C in NaCl medium at different ionic strengths and in absence of supporting electrolyte for uranyl–fulvate (\( {{\text{UO}}_{2}}^{2+} \)–FA) and uranyl–polyacrylate (\( {{\text{UO}}_{ 2}}^{ 2+ } \)–PAA, PAA MW 2 kDa) systems, respectively. The experimental data are consistent with the following speciation models for the two systems investigated: (i) UO2(FA1),…

Hydrocarbons removal from synthetic bilge water by adsorption onto biochars of dead Posidonia oceanica.

AbstractBilge waters are wastewaters produced on boats during navigation and usually contain hydrocarbons and oils. They cannot be directly released into the sea if not below a hydrocarbons concentration limit set by current legislation. Appropriate oil in water separator (OWS) systems can be installed on board boats to remove hydrocarbons from bilge water allowing their spillage into the sea. These systems may contain an adsorption step on a suitable adsorbent. Here, biochars produced from pyrolysis of dead Posidonia oceanica, pristine or chemically activated, have been tested as hydrocarbons adsorbents. Adsorption experiments with aqueous dispersions simulating bilge waters containing a m…

Effect of seawater salt on the protonation of some classes of ligands

Acid-base properties of halloysite clay nanotubes in NaCl medium

Interaction of methyltin(IV) compounds with carboxylate ligands. Part 1: formation and stability of methyltin(IV)–carboxylate complexes and their relevance in speciation studies of natural waters.

Quantitative data on the stability of mono-, di- and trimethyltin(IV)-carboxylate complexes (acetate, malonate, succinate, malate, oxydiacetate, diethylenetrioxydiacetate, tricarballylate, citrate, butanetetracarboxylate and mellitate) are reported at t=25°C and I → 0 mol l - 1 . Several mononuclear, mixed proton, mixed hydroxo and polynuclear species are formed in these systems. As expected, the stability trend is mono- > di- > trimethyltin(IV) and mono < di < tri < tetra < hexa for the organotin moieties and carboxylate ligands investigated, respectively. Moreover, ligands containing, in addition to carboxylic,-O-and-OH groups show a significantly higher stability with respect to analogou…

Interaction of methyltin(IV) compounds with carboxylate ligands. Part 2: Formation thermodynamic parameters, predictive relationships and sequestering ability.

Thermodynamic data of mono-, di- and tri-methyltin(IV)-carboxylate complexes (acetate, malonate, succinate, oxydiacetate, diethylenetrioxydiacetate, malate, citrate, 1,2,3-tricarballylate, 1,2,3,4-butanetetracarboxylate, 1,2,3,4,5,6-benzenehexacarboxylate) in aqueous solution are reported at t = 25 °C and I = 0 mol l−1. Thermodynamic parameters obtained were analysed to formulate empirical predictive relationships as a function of different parameters, such as the number of carboxylate groups of the ligand and the charge of the alkyltin(IV) cation. Sequestration diagrams of citrate and 1,2,3-tricarballylate towards alkyltin(IV) cations at different pH values are also reported and discussed.…

Sustainable soy protein microsponges for efficient removal of lead (II) from aqueous environments

Protein-based materials recently emerged as good candidates for water cleaning applications, due to the large availability of the constituent material, their biocompatibility and the ease of preparation. In this work, new adsorbent biomaterials were created from Soy Protein Isolate (SPI) in aqueous solution using a simple environmentally friendly procedure. Protein microsponge-like structures were produced and characterized by means of spectroscopy and fluorescence microscopy methods. The efficiency of these structures in removing Pb2+ ions from aqueous solutions was evaluated by investigating the adsorption mechanisms. The molecular structure and, consequently, the physico-chemical propert…

Sequestering Ability of Aminopolycarboxylic (APCs) and Aminopolyphosphonic (APPs) Ligands Toward Palladium(II) in Aqueous Solution

The binding capacity of three aminopolycarboxylates [nitrilotriacetic acid (NTA), ethylene-glycol-bis(2-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA), and diethylenetriamine-N,N,N,NN-pentaacetic acid (DTPA)] and two aminopolyphosphonates {(1-hydroxyethane-1,1-diyl)bis(phosphonic acid) (HEDP) and [[(phosphonomethyl)imino]bis[2,1-ethanediylnitrilobis(methylene)]] tetrakis-phosphonic acid (DTPP)} toward palladium(II) ion was studied by potentiometric and spectrophotometric titrations at different temperatures (283.15 ≤ T/K ≤ 318.15) and ionic strengths (0.1 ≤ I/mol·dm -3 ≤ 1.0) in NaClO4. The hydrolysis of Pd2+ and the protonation of ligands were always taken into account in the speciation…

Evaluation of the Purity of Magnesium Hydroxide Recovered from Saltwork Bitterns

Magnesium has been listed among the 30 critical raw materials by the European Union. In recent years, many green and sustainable alternative Mg2+ sources have been sought to satisfy the EU’s demand and to avoid mineral ore consumption. In this context, saltwork bitterns, the by-products of solar sea salt production, have attracted much attention thanks to their high Mg2+ concentrations (up to 80 g/L) and low Ca2+ and bicarbonate contents (&lt;0.5 g/L). Although investigations on Mg2+ extraction from bitterns in the form of Mg(OH)2(s) have already been performed, product purity has never been properly addressed. Mg(OH)2(s) is a chemical compound of great interest and extensive utility in num…

Speciation of vanadium in urban, industrial and volcanic soils by a modified Tessier method

Vanadium (V) concentrations in industrial, urban and volcanic soils were sequentially extracted using a modified Tessier's method. The voltammetric technique was used to determine V concentrations in solutions obtained from the various extraction steps. At the reference stations, the V concentrations (sum of four individual fractions) in soils ranged from 0.72 to 0.24 g kg(-1) dry weight (d.w.) with a mean value of 0.18 g kg(-1) d.w. V concentrations in soils of the Palermo urban area ranged from 0.34 to 2.1 g kg(-1) d.w., in the Milazzo (industrial) area between 0.26 and 5.4 g kg(-1) d.w. and in the volcanic area near Mt. Etna from 0.91 to 2.9 g kg(-1) d.w. When the V concentrations around…

Modelling of protonation constants of halloysite clay nanotubes in various aqueous media, at different ionic strengths

In the last decade nanoparticles have assumed more and more importance because of their particular properties mainly due to the nanometer-scale dimensions that confer them a large surface/volume ratio. Among nanomaterials one of the most studied is the halloysite that, as well as the other natural clay minerals is safe for human and environmental friendly. Halloysite is abundant and cheap and is present in large deposits worldwide like those in New Zealand, France, Belgium and China [1,2]. It is similar to kaolin but has a hollow tubular structure that can be attributable to particular crystallization conditions. Typically, halloysite nanotubes (HNTs) are formed by 15 – 20 aluminosilicate l…

SORPTION OF CD2+ AND CU2+ IONS FROM AQUEOUS SOLUTIONS BY ALGINATE AND ALGINATE/PECTIN GEL BEADS.

Removal of toxic metal ions from natural waters, wastewaters and contaminated sites is of great importance for the health of living organism and for environmental protection (1). Alternatively to the conventional chemical treatments, such as precipitation, reverse osmosis, etc, that are expensive and of high environmental impact, the use of low cost and environmental friendly sorbent materials is a very promising new technology for meal ions removal (2,3). The most investigated sorbent materials are of organic origin derived from the natural biomass (algae, fungi, bacteria) and from industrial processes, such as wood, agriculture, fishery, textile manufacturing, etc. Also some inorganic mat…

Interactions UO22+ - amines

On the Complexation of Cu(II) and Cd(II) With Polycarboxyl Ligands. Potentiometric Studies With ISE-H+, ISE-Cu2+, and ISE-Cd2+

The interaction of Cu2+ and Cd2+ ions with polyacrylates (PAA, 2 kDa and 100 kDa), polymetacrylate(PMA, 5.4 kDa), and alginate (AA, 70 kDa to 100 kDa) was studied by potentiometry, using ISE-Cu2+, ISE-Cd2+, and ISE-H+ electrodes. The investigations were performed in NaNO3 aqueous solutions, in the ionic strength range 0.10 e I (mol ·L-1) e 0.75, at T ) 298.15 K. The “diprotic-like model” was used to explain the acid-base behavior of the polycarboxylates under investigation (for this model, the monomeric unit of the polyelectrolyte is considered as a dicarboxylate). The results give evidence for the formation of the ML species in all the systems investigated. In addition, the MLH species was…

SALMO and S3M: A Saliva Model and a Single Saliva Salt Model for Equilibrium Studies.

A model of synthetic saliva (SALMO, SALiva MOdel) is proposed for its use as standard medium inin vitroequilibrium and speciation studies of real saliva. The concentrations come out from the literature analysis of the composition of both real saliva and synthetic saliva. The chief interactions of main inorganic components of saliva, as well as urea and amino acids, are taken into account on the basis of a complex formation model, which also considers the dependence of the stability constants of these species on ionic strength and temperature. These last features allow the modelling of the speciation of saliva in different physiological conditions deriving from processes like dilution, pH, a…

Kinetic and equilibrium study for cadmium and copper removal from aqueous solutions by sorption onto mixed alginate/pectin gel beads

Abstract Kinetic and equilibrium studies have been carried out to evaluate Cd(II) and Cu(II) sorption from aqueous solution by calcium alginate and new synthesized hybrid calcium alginate/pectate gel beads with different alginate/pectate concentration ratios. Physical and chemical properties of the beads were characterized by different techniques (SEM, EDX, TGA). The best experimental pH conditions were selected on the basis of a study on the acid–base properties of pectin and alginate in aqueous solution and their ability to act as sequestering agents for copper(II) and cadmium(II) ions. Calcium released during the sorption process was determined in order to elucidate a possible ion exchan…

Acid-base behaviour of fulvic acids in seawater at different salinities

Chemical characterization of ancient liturgical vestment (chasuble) by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP–OES)

Abstract This paper presents the chemical characterization of the yarns of an ancient liturgical vestment (chasuble). The samples have been analyzed for Al, Ag, Au, Cd, Co, Cr, Cu, Ni, Pb and Zn using amounts always less than 1 mg by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES). Except a sample, silver is the most abundant element in all the yarns. In the samples containing silver, it ranged from 68 to 97%. Only two samples contain aluminum. Although the investigated chasuble is recorded in the inventory as an artifact of the XV century, a part of the yarns is composed of materials attributed to later period. In fact, the voluntary use of aluminum in metal alloys is du…

Mercury(II) removal from aqueous solutions by alginate and pectin sorbent materials. Kinetic and equilibrium study

Complex species formation in the pectin-cadmium(II) and pectin-copper(II) systems in aqueous solution.

Kinetic and equilibrium study for Pd(II) removal from aqueous solution by sorption onto calcium alginate gel beads

The more and more increasing use of catalytic converters to reduce the dangerous NOx and CO emission in the atmosphere by vehicle traffic produces a corresponding increase of palladium in the environment [1]. Among the so-called “platinum group Elements” (PGE), elemental palladium seems to be the most hazardous one because it can be easily and quickly oxidized to palladium(II) when put in contact with soil. The presence of palladium oxidized form is of great concern owing to its recognized toxicity towards plants, animals and humans. Therefore, as for the classical “heavy metals”, a removal of this element from the environment is needed and a subsequent recovery for its potential re-use is …

Sequestration of toxic metal ions and organometallic cations by poly-electrolyte ligands

FUNCTIONALIZED HALLOYSITE NANOTUBES FOR ENHANCED REMOVAL OF Hg2+ IONS FROM AQUEOUS SOLUTIONS

AbstractWater is essential for humans, animals, and plants; pollutants, usually derived from anthropogenic activities, can have a serious effect on its quality. Heavy metals are significant pollutants and are often highly toxic to living organisms, even at very low concentrations. Among the numerous removal techniques proposed, adsorption onto suitable adsorbent materials is considered to be one of the most promising. The objective of the current study was to determine the effectiveness of halloysite nanotubes (HNT) functionalized with organic amino or thiol groups as adsorbent materials to decontaminate polluted waters, using the removal of Hg2+ ions, one of the most dangerous heavy metals…

Thermodynamic Study For The Protonation Of Halloysite

The Halloysite (Al2Si2O5(OH)4·2H2O) is an abundant and cheap clay and is considered one of the most promising nano structured and naturally occurring clay mineral. Large deposits of this material are present in France, Belgium, China, New Zealand and USA [1,2]. Among the spheroidal, tubular or platy morphologies, the tubular is the most common and abundant one. Typically, halloysite nanotubes (HNTs) are formed by 15 – 20 aluminosilicate layers, having a length of 1 ± 0.5 μm, and inner and outer diameters of 10 – 15 nm and 50 -70 nm, respectively [1]. In each layer, the SiOH and the AlOH groups are disposed on the external and the internal surfaces, respectively. As consequence, in each nano…

Reduced graphene oxide/silver nanoparticles/β-cyclodextrin nanosponges composites with improved photocatalytic activity

Significant activity improvement was achieved by associating graphene oxide-silver composite photocatalysts with cyclodextrin-based nanosponge materials, due to the synergistic effect provided by the supramolecular host abilities of the nanosponge. Three photocatalysts were prepared, fully characterized (FT-IR, ss-NMR, Raman, XRD, SEM, EDX, AFM, ICP, TGA, potentiometric titration), and tested for the oxidative photodegradation of some dyes and phenols, chosen as model organic pollutants. Compared to the unsupported photocatalyst, the nanosponge-based materials showed enhanced performances (being able to carry out the degradation even of dyes which do not react in the presence of the unsuppo…

Bio-char from dead Posidonia oceanica residues as adsorbent towards toxic metal ions

Recently, the pyrolysis of biomass from different algal species and from the Mediterranean sea plant Posidonia oceanica have been proposed for renewable fuel production with a maximum oil yield of 54.97% at 500°C, and high heating values of 24-32 MJ kg-1[1,2]. The pyrolysis produces a large amount of bio-char and the accumulation of this byproduct may cause solid waste pollution problems. Although the composition and properties of bio-char depend on the raw material and on the carbonization process, it is on average composed of amorphous carbon with a highly functionalized surface, which makes it reactive towards inorganic and organic compounds [3]. Considering the reactivity of bio-char, t…

8-Hydroxyquinoline-2-Carboxylic Acid as Possible Molybdophore: A Multi-Technique Approach to Define Its Chemical Speciation, Coordination and Sequestering Ability in Aqueous Solution.

8-hydroxyquinoline-2-carboxylic acid (8-HQA) has been found in high concentrations (0.5&ndash

Pb(II) adsorption by a novel activated carbon - alginate composite material. A kinetic and equilibrium study.

The adsorption capacity of an activated carbon – calcium alginate composite material (ACAA-Ca) has been tested with the aim of developing a new and more efficient adsorbent material to remove Pb(II) ion from aqueous solution. The study was carried out at pH = 5, in NaCl medium and in the ionic strength range 0.1–0.75 mol L−1. Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique was used to check the amount of Pb(II) ion removed during kinetic and equilibrium experiments. Different kinetic (pseudo first order, pseudo second order and Vermuelen) and equilibrium (Langmuir and Freundlich) models were used to fit experimental data, and were statistically compared. Calcium alginate …

Interaction of Dioxouranium(VI) ion with aspartate and glutamate in NaClaq at different ionic strengths

The formation of complexes species of the dioxouranium(VI) ion with aspartic and glutamic acids was studied in the pH range of 3 to 6 at 25 °C by potentiometric measurements (H+-glass electrode). Results gave evidence for the formation of the following species: (UO2)A0, (UO2)AH+, and (UO2)2A(OH)2 0 (A2- ) a glutamic or aspartic ligand). Investigations were carried out in a NaCl ionic medium at I (0.1, 0.25, 0.5, and 1.0) mol L-1. The dependence on ionic strength of the formation constants was analyzed by the specific ion interaction theory (SIT) model. The formation constants at infinite dilution, obtained using this model, are log â110 ) 8.53 ( 0.03, 8.37 ( 0.05; log â111 ) 13.60 ( 0.05, 1…

One-pot synthesis of ZnO nanoparticles supported on halloysite nanotubes for catalytic applications

Abstract A versatile catalyst based on halloysite and zinc oxide (HNT@ZnO) was prepared, for the first time, starting from ZnO commercial bulk form as Zn precursor source, in a one-pot procedure. This strategy gives the possibility to obtain small ZnO nanoparticles loaded on the HNT surface without the use of inorganic salts which envisage the removal of undesired anions and therefore a calcination process at high temperature. It was found that the presence of halloysite improved the UV–vis spectral absorption ability of ZnO. The hybrid was successful used as photocatalyst for the methylorange and rhodamine B degradation. In addition, after eight consecutive cycles for the methylorange phot…

Formazione di complessi di Cu(II) e Cd(II) con leganti policarbossilici. Studio potenziometrico con ISE-H+, ISE-Cu2+ e ISE-Cd2+.

Polycarboxylic acids in sea water: acid–base properties, solubilities, activity coefficients, and complex formation constants at different salinities

This paper reports the results of the investigations carried out in synthetic sea water at different salinities for different classes of polycarboxylic acids. The investigations can be summarized as follows: (a) Determination of the protonation constants in such multicomponent solution in a salinity range 15 ≤ S ≤ 45, at t = 25 °C, for the linear dicarboxylic acids HOOC-(CH2) n –COOH (0 ≤ n ≤ 8), and aromatic polycarboxylic acids (o-phthalic and 1,2,4-benzenetricarboxylic acids). For malonic, succinic, 1,2,3-benzenetricarboxylic, and 1,2,3,4-benzenetetracarboxylic acids, investigations were also carried out at t = 10 and 37 °C; (b) Determination of the total and intrinsic solubility (S T an…

A critical approach to the toxic metal ion removal by hazelnut and almond shells

The adsorption capacity of ground hazelnut (HS) and almond (AS) shells towards Pb(II) and Cd(II) has been studied at pH = 5, in NaNO3 and NaCl ionic media, in the ionic strength range 0.05-0.5 mol L-1. Kinetic and equilibrium experiments were carried out by using the Differential Pulse Anodic Stripping Voltammetry technique to check the amount of the metal ion removed by HS and AS materials. Different kinetic and equilibrium equations were used to fit experimental data and a statistical study was done to establish the suitable model for the data fitting. A speciation study of the metal ions in solution was also done in order to evaluate the influence of the ionic medium on the adsorption pr…

A novel thermodynamic approach for the complexation study of toxic metal cations by a landfill leachate

Landfill leachates can contaminate nearby aquifers. The hazards deriving from this contamination also depend on the chemical speciation of various contaminants. A novel approach is proposed here to face this problem from a chemical thermodynamics point of view. The complexing ability of the soluble fraction of a landfill leachate (collected from Bellolampo, Palermo, Italy) towards Pb2+, Cd2+ and Cu2+ has been investigated at T = 298.15 K in NaClaq at I = 0.1 mol dm−3. The soluble fraction of the landfill leachate was first characterized by different analytical techniques. Then, its acid–base properties were studied by ISE-H+ potentiometric titrations and modelled by the so-called diprotic-l…

Advances in the investigation of dioxouranium(VI) complexes of interest for natural fluids

Abstract The interactions of dioxouranium(VI) cation with different organic and inorganic ligands of environmental and biological interest were carefully examined with the aim to draw a chemical speciation picture of this ion in natural aquatic ecosystems and in biological fluids. Since UO22+ ion shows a significant tendency to hydrolyze, particular attention was paid in considering the hydrolysis species formation both in the presence and in absence of ligands. The results reported in the literature show that formation of the hydrolytic species assumes a great importance in the complexation models for all the UO22+-ligand systems considered. In particular, the following ligands have been t…

Interazioni UO2 – ATP in soluzione acquosa

Capacità sequestrante di leganti policarbossilici naturali e di sintesi nei confronti dello ione (CH3)Hg+