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.     

Long-term interactions in clay/electrolyte systems

The influence of long-term interactions on sorption of cesium on montmorillonite has been examined. After initial fast sorption due to ion-exchange, the additional two-step sorption as a result of dissolution of main clay constituents, changes in solution chemistry and readsorption and/or precipitation of resultant species, were observed.     

Preparation of sorbents based on chitosan and its sulfoethyl derivative for sorption of perrhenate ions

The ability of cross-linked chitosan to take up perrhenate ions was studied systematically. The degree of sorption from acetate buffer solution at pH in the interval 2.8–3.1 reaches 85% and more. N-Sulfoethylation decreases the sorption ability of chitosan, but expands the pH interval of sorption and shifts the optimum pH value toward higher acidities. The sorption materials exhibit higher sorption rate than standard synthetic ion exchangers do. The data obtained suggest predominant ion-exchange mechanism of sorption of perrhenate ions onto chitosan and its sulfoethyl derivative.     

Sorption of aluminate from alkaline solutions on D-403 anion exchanger

The sorption of aluminate from alkaline solutions on D-403 anion exchanger is studied. The sorption isotherm is described by the Langmuir and Freindlich classical equations and the Redlich-Peterson generalized equation. Thermodynamic parameters of sorption are determined using the Langmuir equation, modified to describe ion-exchange eqiulibria. A method for determining the type of the sorbed ion in the solid phases is proposed.     

Dynamic of Exchange Sorption of Transition Metal Ions on Phosphate Cationite KFP-12

The dynamics of ion-exchange sorption of double-charged metal ions on a phosphate cationite KFP-12 was studied. Theoretical calculations of stationary fronts were carried out, the motion velocity of the stationary fronts was calculated, and the rate constant of sorption was evaluated.     

Study of ion-exchange properties of tin(IV) phosphate modified with sodium hexanitrocobaltate

The interrelation between the chemical composition, structure, and ion-exchange properties of tin(IV) phosphate modified with sodium hexanitrocobaltate was studied. The sorption capacity was increased; the possibilities for lithium, rubidium, and cesium sorption were extended owing to change in the size of cavities in the structure.     

Chromatography of aromatic compounds on anion-exchange resins

Complex mixtures of aromatic compounds can be rapidly separated on anion-exchangers in the acetate form with acetic acid as eluent and determined automatically by recording the absorbance in the ultraviolet. Carboxylates are separated by ion-exchange. Hydrogen bonds between non-disso-ciated acids and the counter-ions influence the distribution coefficients. Hydrogen-bonding with the resin has a marked effect on the sorption of solutes containing phenolic protons. Intramolecular hydrogen-bonding depresses their sorption. Hydrophobic interactions have a predominant influence with hydrocarbons and with phenolic compounds containing non-polar aliphatic substituents. The relative importance of these interactions increases with a decreased ion-exchange capacity of the resin.     

Anion-exchange resin modified with bismuthiol-II, as a new functional resin for the selective collection of selenium(IV)

A functional resin for the collection of selenium(IV) has been prepared simply by the conversion of a common ion-exchange resin with bismuthiol-II which has three functional properties, namely the capabilities of selective reaction with selenium(IV), ion-exchange reaction with ion-exchange resin and strong physical sorption to the ion-exchange resin matrix. The binding ratio of selenium(IV) to bismuthiol-II on the resin was confirmed to be 1:4. The reaction was represented as follows: 4RSH + H(2)SeO(3)--> R-S-Se-S-R + R-S-S-R + 3H(2)O. Highly selective sorption of selenium(IV) was achieved, based on the formation of stable selenotrisulphide on the resin. Selenium(IV) sorbed on bismuthiol-II resin was eluted effectively with 8-13M nitric acid or some thiols, such as cysteine and penicillamine. In the cases of thiols, the elution of selenium was found to be also based on the formation of selenotrisulphide, and the bismuthiol-II resin was regenerated. Satisfactory results were obtained when this resin was applied to the determination of selenium(IV) in river, estuarine or sea water samples.     

Preparation and Ion-Exchange Properties of Mixed Zirconium(IV) Phosphate-Phosphonate Sorbents

Composite sorbents based on Zr(IV) phosphate-hydroxyethylidenediphosphonate with different phosphate-phosphonate ratio were prepared. These sorbents were characterized by elemental analysis, X-ray diffraction, and IR spectroscopy, and their ion-exchange sorption capacity for several transition metals and strontium was studied. The sorption capacity of these sorbents increases with increasing pH.     

Special Features of Sorption and Luminescence of Tb3+ Cations and Azomethine Bases in Perfluorosulfonic Membrane

Russian Journal of General Chemistry - The limiting value of ion-exchange sorption capacity of the perfluorosulfonic membrane with respect to Tb3+ is reproducible when the cation is in excess in...     

Sorption of U(VI) ions on sol-gel-synthesized amorphous spherically granulated titanium phosphates

The ion-exchange-precipitation mechanism of sorption was established for amorphous spherically granulated titanium phosphates. Under optimal conditions (pH 5.0?C6.0) uranium undergoes sorptive accumulation in amounts substantially exceeding the ion-exchange capacity of the sorbents. Under acidic and alkaline conditions, where ion exchange cannot proceed, uranium sorption follows the precipitation mechanism, which allows treatment of real uranium-containing solutions without optimized conditions. The ion-exchange-precipitation mechanism also operates in sorption of some heavy metals on amorphous spherically granulated titanium phosphates.     

Highly efficient iodine species enriching and guest-driven tunable luminescent properties based on a cadmium(II)-triazole MOF

The first example of highly efficient iodine enrichment based on a Cd(II)-triazole MOF (1) via both molecular sorption and ion-exchange approaches is reported.     

The application of microfine ionites for the improvement of the efficiency of sorption processes in drug production (Review)

Results of the application of microfine ionites of different classes for sorption methods in the production of versatile drugs are systemized. Kinetic and dynamic parameters of sorption isolation and chemical purification of drugs with participation of ion-exchanger of small graining are discussed; essential advantages of their application allowing intensification of ion-exchange technological processes of drugs production are determined. The review can be useful at elaboration of new sorption methods used for the production of the wide assortment of drugs and, first of all, antibiotics, enzymes, and vitamins.     

Effect of structural variation within sym-(R)dibenzo-16-crown-5-oxyacetic acid resins upon the selectivity and efficiency of alkali-metal cation sorption

Five new crown ether carboxyhc acid resins have been prepared by condensation polymerization of sym-(R)dibenzo-16-crown-5-oxyacetic acids with formaldehyde. Competitive alkali-metal cation sorption by these novel resins, which contain both ion-exchange and crown ether binding sites for metal ions, has been investigated. As the R-group was varied (methyl, ethyl, propyl, butyl, hexyl and decyl) both the alkali-metal cation sorption selectivity and efficiency were affected. The highest efficiency (loading) and Na⁺ sorption selectivity were obtained when R = methyl, ethyl and propyl. The longer alkyl groups were found to be detrimental to both sorption efficiency and selectivity.     

Equilibrium sorption of sulfuric acid by weakly basic polyacrylic anionites

The sorption of sulfuric acid on Amberlite IRA 67 and (2) Lewatit VP.OC.1072 weakly basic polyacrylic anionites in the free-base form was studied. It was demonstrated that the bisulfate form of the anionites was not produced. In contrast to the sorption of hydrochloric acid, the solution of resinates formed during the sorption of sulfuric acid is nonideal. A model of exchange of doubly charged anions on fixed singly charged ion-exchange sites of polyacrylic anionites was developed based on the theory of ion-exchange equilibria. The model was used to analyze the isotherms of equilibrium sorption of sulfuric acid on IRA 67 and Lewatit VP.OC.1072 anionites in the free-base form.     

Study of NaOH-treated clinoptilolites and their physical and ion-exchange characteristics with regard to Cs+ and Co2+

The ion-exchange ability of NaOH-treated clinoptilolites with regard to Cs⁺ and Co²⁺ have been studied by a radiochemical method, enabling to calculate the sorption coefficient. The surface characteristics, total cation exchange capacity and X-ray structural analysis were measured as well. The measurements were done on Slovak clinoptilolite. Comment are made on a possible explanation of increasing sorption coefficient.     

Application of neutron activation analysis for mercury species determination in scalp hair samples from Malaysia, Libya and Jordan

The sorption of Ba²⁺ ion on natural kaolinite and chlorite-illite clays was investigated at different initial concentrations and temperatures using the radiotracer method. The sorption data were well described by Freundlich and Dubinin-Radushkevich isotherms. Ba²⁺ sorption on both clays showed an exothermic behavior with ΔH° (kJ/mol) values being -7 and -5 for sorption on kaolinite and chlorite illite mixed clay, respectively. The ΔG° values indicate that the sorption was spontaneous with sorption energies corresponding to ion-exchange type sorption. X-ray diffraction studies showed that no significant change in the matrix of the clays occurred upon Ba²⁺ sorption. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and properties of strongly basic acrylate polyfunctional anion-exchange resin for uranium extraction

Some studies on the synthesis of strongly basic acrylate polyfunctional anion-exchange resins designed for the extraction of uranium from uranium ore leaching solutions were performed. The alkylation reaction conditions providing the synthesis of a polyfunctional anion-exchange resin with 55% of strongly basic groups were determined. Its sorption properties were studied using model solutions. The capacity of the alkylated polyfunctional anion-exchange resin with respect to uranium was shown to be highly competitive with foreign analogues using the comparative analysis of its ion-exchange characteristics with the parameters of known ion-exchange resins.     

Adsorption Characteristics of Natural Erionite, Clinoptilolite and Mordenite Zeolites from Mexico

Nitrogen sorption properties inherent to some natural zeolites from Mexico, such as erionites, clinoptilolites and mordenites, are determined and compared with corresponding sorption properties of homologous synthetic or acid modified forms. The mineralogies of natural zeolites are determined by X-ray analysis. N₂ low-pressure hysteresis loops are displayed by some substrata while are absent in others; key factors for this phenomenon to occur are the micropore structure and the ion-exchange treatment to which the natural precursors are subjected. Argon sorption at 76 K on selected samples evidence further the strong adsorption and the pore blocking effects at pore necks in the zeolites.     

Effect of thermal annealing on Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-doped silica powder prepared by the solgel process

A novel sorbent for the removal of heavy metals, hydroxyapatite/poly (vinyl alcohol) cryogel, was studied. The HAp/PVA cryogel was characteristic of macroporous structure. The experiments for Cd²⁺ sorption by HAp/PVA cryogel were conducted at various operating conditions such as sonication, sorption time, Cd²⁺ concentration, temperature, pH, and HAp/PVA mass ratio. It was concluded that the sorption was considerably affected by sorption time, Cd²⁺concentration, temperature and HAp/PVA mass ratio. Nevertheless, there was slight dependence of sorption on sonication and pH. The influences of different parameters were discussed in detail in the paper. The main mechanism was suggested to be ion-exchange.