The nonexchange sorption of histidine by low-basicity anion exchangers

The experimental data showed that the nonexchange absorption of histidine by AN-221, AN-251, AN-31, and EDE-10P anion exchangers in the HCl form depended on the structure of the anion exchanger. The activity coefficients of the components of the sorbent phase, thermodynamic equilibrium constants, and standard Gibbs energies of nonexchange sorption of histidine by the low-basicity anion exchangers were calculated and discussed.     

Equilibrium sorption of methionine on carboxyl cation exchangers from solutions of various acidities

The influence of the acidity of solutions of methionine on methionine interaction with KB-2 and KB-4 carboxyl cation exchangers in the protonated and deprotonated forms was studied by the calorimetric, sorption, and spectroscopic methods. It was found that nonexchange methionine absorption occurred from acid solutions, and mixed ion exchange and nonexchange sorption, from alkaline solutions. The enthalpies of sorption of methionine at various external solution pH values were determined. Original Russian Text ? D.V. Ovsyannikova, L.P. Bondareva, V.F. Selemenev, S.I. Karpov, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 5, pp. 961–966.     

Ion exchange extraction of platinum(IV) and palladium(II) from hydrochloric acid solutions

Sorption concentration of platinum(II, IV) and palladium(II) from freshly prepared and aged two-yearold hydrochloric acid solutions by a series of anion exchangers with different functional groups and of different physical structure of Purolite and CYBBER grades was studied. The high sorption ability of the ion exchangers in relation to the extracted chlorocomplexes of noble metals is shown. It was demonstrated that palladium(II) from all tested ion exchangers can be completely desorbed with thiourea solutions acidified with hydrochloric acid, while complete desorption of platinum is achieved only from Purolite S 985 anion exchanger of the complexforming type and Purolite A 111 weak base anion exchanger.     

Performance of anion exchangers based on aniline,epichlorohydrin, and polyamines in sorption of molybdenum(VI) ions

Polyfunctional anion exchangers based on aniline, epichlorohydrin, and some polyamines were synthesized. The composition and structure of the anion exchangers were studied by IR spectroscopy and elemental analysis. Molybdenum sorption was studied by classical polarography, and dependences of the sorption of molybdenum(VI) ions on the solution acidity, concentration of metal ions, and time of contact of the resins with the Na₂MoO₄ solution were determined in batch experiments. These ion exchangers exhibit high performance in sorption of molybdenum ions. The developed sorbents with increased sorption ability can successfully solve problems of removing molybdenum(VI) ions from process effluents in nonferrous metallurgy.     

Sorption recovery of platinum(II, IV) from chloride and sulfate-chloride solutions

Sorption of platinum(II, IV) from chloride and sulfate-chloride solution on anion exchangers of varied chemical structure (various functional groups and varied basicity) was studied. It was found that sulfate-chloride systems have high efficiency comparable with that of chloride systems in sorption of platinum by AM-2B, Purolite S 985, and Lewatit MP 600 WS anion exchangers.     

Activity coefficients of components of the sorbent phase in the nonexchange sorption of chloride-containing electrolytes on AN-31 low-basicity anion exchanger in the Cl form

Activity coefficients of components of the sorbent phase in the nonexchange sorption of chloride-containing electrolytes (hydrochloric acid and potassium, sodium, and magnesium chlorides) on AN-31 low-basicity anion exchanger in the Cl form are calculated and analyzed. Peculiarities of the sorption of the investigated electrolytes on the anion exchanger are discussed.     

Preparation of Anion Exchanger for High-Efficiency Purification of Halogen-substituted Hydrocarbon Solvents Used To Clean Metal Optics

Phenomenon of rising sorption capacity of AV-17-8 anion exchanger upon an increase in its humidity due to the superequivalent absorption of Cl^– ions was revealed and substantiated. The purification of halogensubstituted hydrocarbon solvents to remove acids under dynamic conditions by the ion-exchange method and the dynamics of sorption by anion exchangers of halogen-substituted solvents from model solutions were studied. It was shown that AV-17-8 anion exchanger is stable in halogen-substituted solvents and, when present in the OH–form, raises their stability against destruction, and the equilibrium sorption capacity of the anion exchanger is 2–3 times its exchange capacity.     

Sorption of Nickel Ions from Aqueous Solutions by Ion Exchangers

Sorption of Ni²⁺ions from aqueous solutions by ion exchangers differed in their chemical nature and structure was studied. Based on the endothermic curves of ice melting obtained by a differential scanning calorimetry, the amounts of freezing and non-freezing water present in free volumes (pores) of the studied ion exchangers were calculated. Comparison of results obtained from the kinetic curves of nickel ion sorption with data on differential scanning calorimetry indicates a role of structural factor in the sorption of nickel ions. It was found that, depending on the total amount of freezing and non-freezing water, the KU-2-8 sulfonated cationite is the most preferable ion exchanger for the sorption of nickel ions from aqueous solutions. Therefore, sorbent efficiency in this case is determined by its structure rather than by chemical nature.     

The equilibrium sorption of sulfuric acid by weakly basic polyacrylic anion exchangers synthesized on the basis of polyamines

The equilibrium ion-exchange sorption of sulfuric acid by the free base form of weakly basic polyacrylic anion exchangers with the gel (Relite MG1) and porous (Relite MG1/P) structures was studied. It was proved that the bisulfate variety of the anion exchangers did not form. Solutions of resinates were found to be nonideal. Their nonideality was analyzed in terms of the theory of exchange equilibria to suggest a model of the exchange of doubly-charged anions on fixed polyamine exchange centers of Relite MG1 and Relite MG1/P anion exchangers. The type of the ion was found to have no effect on sorption parameters.     

Features of the sorption of phenylalanine by profiled ion-exchange membranes

Features of the equilibrium sorption of phenylalanine from neutral media by profiled ion-exchange membranes in a wide range of concentrations is studied under static conditions. The mechanism of phenylalanine sorption by ion-exchange membranes with profiled and smooth surfaces is discussed. It is shown that phenylalanine sorption is accompanied by the formation of spatial associative structures of the aminoacid in an external equilibrium solution, and in a solution of the membrane’s pore spaces or on its surface. The increased sorption capacity of the profiled membranes is explained by features of the microstructure of their surface and volume.     

Sorption of aliphatic amines by monocarboxycellulose from aqueous and water-ethanol solutions

The features of the sorption of hydrochlorides of lower aliphatic amines by monocarboxycellulose (MCC) from aqueous and water-ethanol solutions are studied. The ion exchange character of the sorption is shown by IR spectroscopy and potentiometry. It is found that the sorption of all studied salts of aliphatic amines by MCC from dilute aqueous and water-ethanol solutions is thermodynamically advantageous due to the great contribution of Coulomb interactions between cations and polyanions. The selectivity of sorption is predetermined by solvophobic (hydrophobic) interactions, which are thermodynamically disadvantageous at any compositions of the binary solvent due to the formation of dimeric associates of carboxyl groups in the phase of MCC, which hinder the contacts of hydrocarbon radicals of aliphatic amines with hydrophobic sites of the cellulose adsorbent matrix. At high concentrations of aliphatic amines in aqueous and water-ethanol solutions, the process of nonexchange sorption proceeds intensely through the hydrogen bonding between nitrogen atoms and hydroxyl groups of MCC.     

Study of Sorption Properties for Lead(II) Ions Exhibited by Anion Exchangers Synthesized on the Basis of Aromatic Hydrocarbons,Epichlorohydrin, and Polyethyleneimine

Aromatic hydrocarbons, epichlorohydrin, and polyethyleneimine were used to synthesize polyfunctional anion exchangers. IR spectroscopy and elemental analysis were used to examine their composition and structure. The method of classical polarography was employed to examine the process of extraction of lead ions and determine the dependences of the sorption of lead(II) ions in the static mode on the solution acidity, concentration of metal ions, and duration of contact between ion exchangers and a Pb(NO₃)₂ solution. It was found that the ion exchangers possess high sorption properties for lead ions.     

Quantum chemical simulation of low-basic AN-221(НСl) anion exchanger during the hydration and non-exchangeable absorption of phenylalanine

The formation of structures obtained during the hydration and non-exchangeable absorption of phenylalanine by a low-basic AN-221 ion exchanger in the НСl form is modeled in the work. Quantum chemical calculations are made using the Gaussian 03 program implementing the B3LYP hybrid density functional with the 6-31G++(d,p) basis set. The sequence of hydration and dissociation of functional groups of the ion exchanger is determined, the structure is optimized, and its formation energy during the non-exchangeable sorption of phenylalanine by the AN-221 (НСl) anion exchanger is estimated.     

Ion exchange equilibria in simultaneous extraction of platinum(II,IV) and rhodium(III) from hydrochloric solutions

Regularities of sorption extraction of platinum(II, IV) and rhodium(III) by anion exchangers of various physical and chemical structure in the presence of hydrochloric media were studied. It is established that AM-2B, Purolite A 500, and Purolite S 985 ionites adsorb complex anions of platinum metals employing mixed mechanism. A high affinity of the studied anionites for the studied complex anions of platinum and rhodium is established.     

Application of the new thermodynamic approach to the description of superequivalent sorption by ion exchangers

Using the example of sorption systems with the participation of amino acids, it is shown that the novel thermodynamic approach to describing superequivalent sorption as a combination of ion exchange and nonexchangeable absorption allows us to adequately describe such equilibria. Results from calculating the activity coefficients of components of a sorbent phase and the thermodynamic constants of ion exchange equilibrium and the superequivalent absorption of phenylalanine by AV-17-8 anion exchange resin are presented.     

Kinetics of rhenium sorption from weakly basic macroporous and gel anion exchangers Purolite A170 and Purolite A172 from sulfuric acid solutions

Effect of the grain size of anion exchangers, agitation intensity, and temperature on the kinetics of rhenium sorption on weakly basic macroporous and gel anion exchangers Purolite A170 and Purolite A172 from a 1 M H₂SO₄ solution was studied.     

The dynamics of sorption of sulfuric acid by weakly basic polyacrylic anion exchangers

The nonequilibrium dynamics of sorption of sulfuric acid by free base forms of Amberlite IRA-67 and Lewatite VP.OC.1072 weakly basic anion exchangers is studied. It is established that, in hydrodynamic regimes of filtration, which are typical of OH filters of the first stage of water-desalting plants, the limiting stage of sorption kinetics is inside diffusion. It is concluded that the process is correctly described by an asymptotic solution to the inside-diffusion model of sorption dynamics. Original Russian Text ? A.V. Mamchenko, T.V. Kushnir, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 5, pp. 967–971.     

Reductive sorption of molecular oxygen from water on silver-KU-23 sulfo-cation exchanger nanocomposites in different ionic forms

New silver-containing nanocomposites different in their dispersity of metal were synthesized on the basis of strongly and weakly basic anion-exchange resins. The chemical activity of the nanocomposites with respect to oxygen dissolved in water was investigated. It was shown that silver nanoparticles in samples based on strongly basic anion exchangers and weakly basic anion exchangers in the NO₃⁻ salt form are not oxidized by oxygen; for weakly basic matrices in the free amine form, this process occurs to only a small extent. The resistance to oxygen is explained by inhibition of processes of formation of silver oxides. Nanocomposites based on strongly basic anion-exchange resins are recommended for testing as to catalytic activity.     

Minimizing losses of nonionic and anionic surfactants to a montmorillonite saturated with calcium using their mixtures

Losses of surfactants through sorption to soils/sediments, especially to clay minerals, by various chemical interactions such as sorption and precipitation threaten the success of surfactant in enhancing remediation of contaminated soil and groundwater. In this study, the behavior of mixtures of a nonionic surfactant (TX-100) and an anionic surfactant (SDBS) sorbed to a montmorillonite saturated with calcium (Ca-montmorillonite) was investigated, and compared with that of individual surfactants. It is shown that the amounts of both TX-100 and SDBS sorbed to Ca-montmorillonite are significant. However, the amount of either TX-100 or SDBS sorbed can be decreased and minimized when they are mixed with each other. Mixed micelle formation, which causes negative deviation of critical micelle concentrations (CMCs) from the ideal, is responsible for the decrease in sorbed TX-100 and sorbed SDBS in their mixtures. Because of their ability to minimize their amounts sorbed and thus enhance their active concentrations, as observed in mixed TX-100 and SDBS systems, mixed anionic-nonionic surfactants exhibit potential advantages in the area of enhanced soil and groundwater remediation.     

Effect of counter- and co-ions on the structural transport parameters of sulfoacid cationite membranes

The diffusion permeability and specific electroconductivity of MK-40 sulfoacid cationite and Nafion 425 membranes are studied experimentally in NaOH, NaCl, and HCl solutions with various concentrations. The resulting concentration dependences of the electrodiffusion characteristics and data on the nonexchange sorption of the electrolytes are used to calculate the structural transport parameters of the membranes in terms of a two-phase conduction model. Analysis of a set of parameters, including the electroconductivity and diffusion permeability of the membrane gel phase, the volume fractions of the conductive phases, and a parameter that reflects their relative positions, the Donnan constant, and the diffusion coefficients of counter and co-ions in the membrane gel phase reveals the effect the nature of counter- and co-ions has on the electrodiffusion, structural, and sorption characteristics of sulfoacid cationite membranes with different types of structure.