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This work is focused on the design and preparation of polymer inclusion membranes (PIMs) for potential applications for stannous cation sequestration from water. For this purpose, the membranes have been synthesized employing two polymeric matrices, namely, polyvinylchloride (PVC) and cellulose triacetate (CTA), properly enriched with different plasticizers. The novelty here proposed relies on the modification of the cited PIMs by selected extractants expected to interact with the target cation in the membrane bulk or onto its surface, as well as in the evaluation of their performances in the sequestration of tin(II) in solution through chemometric tools. The composition of both the membrane and the solution for each trial was selected by means of a D-Optimal Experimental Design. The samples such prepared were characterized by means of TG-DTA, DSC, and static contact angles investigations; their mechanical properties were studied in terms of tensile strength and elastic modulus, whereas their morphology was checked by SEM. The sequestering ability of the PIMs toward stannous cation was studied by means of kinetic and isotherm experiments using DP-ASV. The presence of tin in the membranes after the sequestration tests was ascertained by μ-ED-XRF mapping on selected samples. [ABSTRACT FROM AUTHOR]

Abstract Metal pollution, coming from both natural and anthropogenic sources, has become one of the most serious environmental problems. Various strategies have been tested with the aim of removing heavy metals from environment. In this contribution, containing a robust experimental work together with a critical literature analysis, the sequestering ability of a variety of ligands towards Sn2+ cation will be evaluated in the conditions of several natural fluids, i.e. sea water, fresh water, human blood plasma, urine and saliva. 13 structural and 11 thermodynamic descriptors will be selected for a total of thirty-eight molecules belonging to different classes (carboxylic acids, amines, amino acids, phosphonates, polyelectrolytes etc. …). For the filling of those missing data relative to the 11 thermodynamic descriptors, different strategies will be adopted, including simple correlations and Nipals algorithm. The evaluation of the sequestering ability of the ligands is assessed in terms of estimation of pL 0.5 (total concentration of ligand required to bind the 50% of metal in solution), an empirical parameter that takes into account all the side reactions in solutions and does not depend on the speciation scheme. Partial least square calculations were performed to model the pL 0.5 and to determine its correlation with the abovementioned descriptors. The possibility to design and build up new tailor-made molecules capable of effectively sequester Sn2+ in various conditions is crucial for practical applications in biosphere, hydrosphere and lithosphere. Graphical abstract Unlabelled Image Highlights • The data published for the interaction of Sn2+ with 38 molecules are surveyed. • A chemometric approach for the estimation of unknown thermodynamic data is given. • Amino groups and thiols are important for the efficient sequestration of Sn2+. • The work is useful for applications in biosphere, hydrosphere and lithosphere. • PLS coefficients help in design new ligands for the efficient sequestration of Sn2+. [ABSTRACT FROM AUTHOR]

The sequestration of Al 3+ by etidronic acid (1‑Hydroxyethane‑1,1‑diyil)bis(phosphonic acid) ( HEDPA ), nitrilotriacetic acid and its phosphonic derivatives, namely N ‑(phosphonomethyl)iminodiacetic acid (PMIDA, NTAP ), N , N ‑bis‑(phosphonomethyl)glycine ( NTA2P ) and [bis(phosphonomethyl)amino]methylphosphonic acid ( NTA3P ) was studied in aqueous solution at T = 298.15 K and I = 0.15 mol L −1 in NaCl. Formation constants and speciation models are discussed on the basis of potentiometric results. The speciation models found for all the systems include MLH, ML and MLOH species, in addition for Al 3+ - NTA system ML(OH) 2 and M 2 L 2 (OH) 2 , for NTAP system ML 2 , for NTA2P and NTA3P systems MLH 2 species, for HEDPA system ML 2 and ML 2 OH species were detected as well. The formation constant values for ML species show the trend NTA < NTAP < HEDP < NTA2P < NTA3P . Investigations using 1 H NMR spectroscopy were also performed for the study of Al 3+ - NTAP system. The 1 H NMR findings are in agreement with the speciation model obtained by potentiometry, confirming the stabilities of the main species. The dependence of formation constants on ionic strength over the range I = 0.15 to 1 mol L −1 in NaCl is also reported for NTA , NTAP , NTA2P systems. Enthalpy change values obtained by titration calorimetry at T = 298.15 K and I = 0.15 mol L −1 in NaCl, for the main Al 3+ - NTA, -NTAP, -NTA2P and NTA3P species, are mainly endothermic, as typical for hard-hard interactions. The sequestering ability of the ligands under study towards Al 3+ was also evaluated, under different pH conditions by the empirical parameter pL 0.5 . [ABSTRACT FROM AUTHOR]

The interaction of Al 3+ and nucleotide ligands, namely adenosine-5′-monophosphate, ( AMP ), adenosine-5′-diphosphate, ( ADP ), adenosine-5′-triphosphate, ( ATP ), has been studied in aqueous solution at T  = 298.15 K and I  = 0.15 mol L −1 in NaCl (only for Al 3+ - ATP system at I  = 0.1 mol L −1 ). Formation constants and speciation models for the species formed are discussed on the basis of potentiometric results. The speciation models found for the three systems include ML and ML 2 species in all the cases, and for Al 3+ - ADP and ATP systems, MLH, MLOH and ML 2 OH species as well. The formation constant value for ML species shows the trend, AMP  <  ADP  <  ATP . 1 H NMR spectroscopy was also employed for the study of Al 3+ - ATP system. The 1 H NMR results are in agreement with the speciation model obtained from analysis of potentiometric titration data, confirming the stabilities of the main species. Enthalpy change values were obtained by titration calorimetry; for the main Al 3+ - ATP species (at T  = 298.15 K and I  = 0.1 mol L −1 in NaCl), they resulted always higher than zero, as typical for hard-hard interactions. The dependence of formation constants on ionic strength over the range I  = 0.1 to 1 mol L −1 in NaCl is also reported for Al 3+ - ATP system. The sequestering ability of the nucleotides under study towards Al 3+ was also evaluated by the empirical parameter pL 0.5 . [ABSTRACT FROM AUTHOR]

The speciation of Al 3+ in aqueous solutions containing organic and inorganic ligands important from a biological (citrate ( Cit 3− ), gluconate ( Gluc - ), lactate ( Lac - ), silicate (H 2 SiO 4 2− ), carbonate (CO 3 2− ), fluoride (F − )) and industrial (Gantrez ® ; polymethyl-vinyl-ether- co -maleic acids; GTZ S 95 and GTZ AN 169) point of view is reported. The stability constants of Al 3+ / L z− complexes ( L z− = ligand with z − charge) were determined by potentiometry at T = 298.15 K and 0.10 ≤ I /M ≤ 1.00 in NaCl (aq) (in NaNO 3(aq) only for Al 3+ / GTZ S 95 and Al 3+ / Gluc − acid systems). For Al 3+ / Cit 3− , Al 3+ / Lac - and Al 3+ / GTZ AN 169 4− systems, the investigations were also carried out at 283.15 ≤ T /K ≤ 318.15. The dependence of the thermodynamic parameters on ionic strength and temperature was modelled with a Debye-Hückel type equation. Different speciation schemes of Al 3+ / L z- systems were obtained, including protonated, simple metal-ligand, polynuclear and hydrolytic mixed species. At I → 0 M and T = 298.15 K the stability trend for the Al L (3−z) species is: 14.28 ± 0.02, 13.99 ± 0.03, 10.16 ± 0.03, 3.16 ± 0.08, 2.84 ± 0.10 for GTZ S 95, GTZ AN 169, Cit 3− , Gluc − and Lac − , respectively. From the investigations at different temperatures, it results that the entropic contribution is the driving force of the reactions. The sequestering ability of the ligands towards Al 3+ was investigated determining the pL 0.5 parameter at different experimental conditions, finding the following trend: Cit 3− » Gluc - > GTZ S 95 4− > GTZ AN 169 4− > Lac - for the organic ligands, and pL 0.5 : F − » CO 3 2− > H 2 SiO 4 2− for the inorganic ones. [ABSTRACT FROM AUTHOR]

A potentiometric, UV and 1 H NMR study on Cu 2+ -ampicillin [(2 S ,5 R ,6 R )-6-([(2 R )-2-amino-2-phenylacetyl]amino)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid] and -amoxicillin [(2 S ,5 R ,6 R )-6-{[(2 R )-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid] systems in NaCl aqueous solution at I = 0.15 mol L −1 and t = 25 °C is reported. On the basis of potentiometric results two speciation models were proposed for each system. It was found that spectrophotometric and 1 H NMR measurements are essential for selecting the most reliable speciation models. They included ML, MLOH and ML(OH) 2 species in both systems and, only for Cu 2+ -ampicillin, also MLH species. The stability constants obtained by UV and 1 H NMR titrations were comparable to the ones calculated by potentiometry. The sequestering ability of the ligands under study towards Cu 2+ by pL 0.5 empiric parameter (ligand concentration required to sequester 50% of the metal cation present in traces) at several pH values was calculated as well. For ampicillin and amoxicillin, pL 0.5 = 7.19 and 6.67, respectively, at physiological pH, I = 0.15 mol L −1 and t = 25 °C were obtained. [ABSTRACT FROM AUTHOR]

The interaction of Zn(II) with ampicillin [(2 S ,5 R ,6 R )-6-([(2 R )-2-amino-2-phenylacetyl]amino)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2- carboxylic acid] and amoxicillin [(2 S ,5 R ,6 R )-6-{[(2 R )-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid] in NaCl aqueous solution at different ionic strengths and at t = 25 °C was investigated by potentiometric, UV and 1 H NMR techniques. Fairly similar speciation models were obtained for the two systems. At I = 0.15 mol L − 1 , two different sets of measurements, at low and high concentrations, were carried out. For the Zn 2 + -amoxicillin system, the Zn 2 L 2 (OH) 2 species was obtained in the set of measurements at high concentration. The spectrophotometric and 1 H NMR results thus obtained are fully consistent with the speciation models found from potentiometric investigations, confirming the formation as well as the relative stability of the complex species. The dependence of the stability constants on the ionic strength was modeled by means of the Debye-Hückel and SIT (Specific ion Interaction Theory) approaches, and the parameter that accounts for the variation of the stability constants with the ionic strength and the specific ion interaction parameters were determined for all the ionic species. The sequestering ability of the ligands towards Zn 2 + was evaluated by determining the pL 0.5 parameter at different ionic strengths. It resulted that the sequestering ability of ampicillin is higher of ~ 0.5 order of magnitude with respect to amoxicillin. [ABSTRACT FROM AUTHOR]

The metal speciation behavior of the amino functionalized 1-(2′-diethylamino)ethyl-3-methylimidazolium-based ILs, bearing anions featured by different coordination properties (chloride, perchlorate, acetate) is reported. Sequestering ability of this family of ILs towards Hg 2 + , CH 3 Hg + , Sn 2 + , (CH 3 ) 2 Sn 2 + , UO 2 2 + , evaluated by the determination of pL 0.5 parameter, was found to be a function of the nature of anions and/or pH. The acetate IL displayed a high affinity towards Hg 2 + and CH 3 Hg + , both at acidic and basic conditions, with respect to chloride and perchlorate derivatives, suggesting that a cation-anion cooperation mechanism is operating in the sequestering process. Conversely, UO 2 2 + sequestration resulted a function of pH and independent on the nature of the anion. The extraction capabilities of hydrophobic 1-(2′-diethylamino)ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide towards Hg 2 + and CH 3 Hg + after treatment with acetate IL were also checked. AAS measurements showed the almost complete removal of both mercury species from water solution. [ABSTRACT FROM AUTHOR]

The estimation of thermodynamic parameters of N-Acetyl-L-cysteine (NAC) protonation were determined in NaCl (aq) , (CH 3) 4 NCl (aq) , (C 2 H 5) 4 NI (aq), employing various temperature and ionic strengths conditions, by potentiometric measurements. The interaction of NAC with some essential metal cations (e.g. , Ca2+, Mg2+ and Zn2+) was investigated as well at 298.15 K in NaCl (aq) in the ionic strength range 0.1 ≤ I /mol dm−3 ≤ 1.0. The values of protonation constants at infinite dilution and at T = 298.15 K are: log K 1 H = 9.962 ± 0.005 (S H) and log K 2 H = 3.347 ± 0.008 (COO-H). In the presence of a background electrolyte, both log K 1 H and log K 2 H values followed the trend (C 2 H 5) 4 NI ≥ (CH 3) 4 NCl ≥ NaCl. The differences in the values of protonation constants among the three ionic media were interpreted in terms of variation of activity coefficients and formation of weak complexes. Accordingly, the determination of the stability of 4 species, namely: NaL−, NaHL0 (aq) , (CH 3) 4 NL−, (CH 3) 4 NHL0 (aq) was assessed. In addition, as regards the interactions of Mg2+, Ca2+ and Zn2+ with NAC, the main species where the ML0 (aq) , ML(OH)−, and ML 2 2−, that were found to be important in the chemical speciation of NAC in real multicomponent solutions. The whole set of the data collected may be crucial for the development of NAC-based materials for natural fluids selective decontamination from heavy metals. Unlabelled Image • Interaction of N-Acetyl-L-cysteine with H+, Na+, Ca2+, Mg2+ and Zn2+ is studied. • Data are modeled according to SIT and weak interaction models. • Complexation occurs through sulfur and oxygen. • Speciation of Zn2+ in sea water and blood plasma is proposed. • Results aid in the design of new materials to remove pollutants from natural fluids. [ABSTRACT FROM AUTHOR]