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…
Palladium(II) sequestration by natural and synthetic chelating agents
Palladium belongs to the so called “Platinum group elements” (PGE), and it is normally present at very low concentration in the environment. In the last twenty years, there has been an increasing PGE demand in different fields such as medicine, electronics, jewellery and car industry. Moreover, palladium (and other PGE) is broadly used as catalyst in a wide number of reactions. The high catalytic properties of PGE favoured their use in the production of catalytic converters. Unfortunately, this caused a noticeable increasing of PGE concentration in the environment, mainly constituted by platinum, with a particular accumulation in urban areas. However, since 1993 platinum has been increasing…
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…
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…
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…
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)
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 of trialkyltin(IV) cations in natural fluids
The hydrolysis of (CH(3))(3)Sn(+), (C(2)H(5))(3)Sn(+) and (C(3)H(7))(3)Sn(+) has been studied in a Synthetic Seawater (SSW) ionic medium simulating the major composition of natural seawater, at different salinities (5 less than or equal to S less than or equal to 45), and at t = 25 degreesC. Interactions with anionic components of SSW, considered as single sea salt, are determined by means of a complex formation model. By potentiometric measurements (ISE-H(+) and ISE-F(-) electrodes), the model has been extended to also consider interactions of organotins with carbonate and fluoride ions, which are other important components of seawater. Literature and new values of hydrolysis constants in …
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…
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…
Hydrolysis and chemical speciation of dioxouranium(VI) ion in aqueous media simulating the major ion composition of seawater
Abstract The hydrolysis and chemical speciation of the dioxouranium(VI) ion at 25 °C was studied in a number of binary electrolytes (LiCl, NaCl, MgCl2, CaCl2, Na2SO4) and some mixtures (NaCl–Na2SO4, NaNO3–Na2SO4, CaCl2–MgCl2) as well as artificial seawater (SSWE) as a function of ionic strength. The results in LiCl, CaCl2 and MgCl2 solutions confirmed the formation of (UO2)2(OH)22+, (UO2)3(OH)42+, (UO2)3(OH)5+ and (UO2)3(OH)7− species (at I=0 mol l−1: log Tβ22=−5.76, log Tβ34=−11.82, log Tβ35=−15.89 and log Tβ37=−29.26). For NaNO3, NaCl and artificial seawater the hydrolysis constant for the formation of the UO2(OH)+ species was also determined (at I=0 mol l−1: log Tβ11=−5.19). The results …
Hydrolysis and chemical speciation of (C2H5)2Sn2+, (C2H5)3Sn+ and (C3H7)3Sn+ in aqueous media simulating the major composition of natural waters
The hydrolysis of (C 2 H 5 ) 2 Sn 2+ , (C 2 H 5 ) 3 Sn + and (n-C 3 H 7 ) 3 Sn + has been studied, by potentiometric measurements ([H + ]-glass electrode), in NaNO 3 , NaCl, NaCl/Na 2 SO 4 mixtures and in a synthetic seawater (SSWE), as an ionic medium simulating the major composition of natural seawater, at different ionic strengths (0 ≤ I ≤ 5 mol dm -3 ) and salinities (15 ≤ S ≤ 45), and at t = 25 °C. Five hydrolytic species for (C 2 H 5 ) 2 Sn 2+ , three for (C 2 H 5 ) 3 Sn + and two for (C 3 H 7 ) 3 Sn + are found. Interactions with the anion components of SSWE, considered as single-salt seawater, are determined by means of a complex formation model. A predictive equation for the calcul…
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…
Modeling S-carboxymethyl-L-cysteine protonation and activity coefficients in sodium and tetramethylammonium chloride aqueous solutions by SIT and Pitzer equations
Solubility and acid–base properties of S-carboxymethyl-l-cysteine (carbocysteine, ccys) in NaClaq and tetramethylammonium chloride, (CH3)4NClaq ,a tt =2 5 ◦ C and at different ionic strengths were investigated. Solubility was studied at 1.0 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 1.0 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq, while potentiometric measurements (by ISE-H + , glass electrode) were performed at 0.1 ≤ I (mol L −1 ) ≤ 5.0 for NaClaq and 0.5 ≤ I (mol L −1 ) ≤ 3.0 for (CH3)4NClaq. Solubility data allowed us to determine Setschenow constants and activity coefficients of neutral carbocysteine (H2ccys). Dependence on ionic strength and ionic medium of protonation constants and activity coeff…
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…
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 …
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…
Speciation of tin(II) in aqueous solution: thermodynamic and spectroscopic study of simple and mixed hydroxocarboxylate complexes
This contribution reports the results of potentiometric and Mossbauer investigations on the formation, stability, and structure of binary and ternary mono- and binuclear complexes of Sn2+ with three hydroxocarboxylic ligands (namely L = tartrate, malate, and citrate) and chloride at T = 298.15 K in different ionic media and ionic strengths (0.15 and 1.00 mol dm−3 in NaCl(aq) and 1.00 mol dm−3 in NaNO3(aq)). The stability constants of various simple Sn i H j L (2+−) and mixed Sn i H j L k Cl (2+−−) species obtained in the different experimental conditions are reported, and various speciation diagrams of the simple and mixed systems are shown in different conditions. The sequestering ability …