V.I. Gorshkov

Ion-exchange separation of alkali and alkaline earth ions in concentrated solutions based on temperature changes

It is shown that, in the case of polyacrylic and polymethacrylic ion-exchangers, the influence of the temperature on selectivity is greater compared with sulfonic resins. Ion-exchange separation of alkali and alkaline earth ions from concentrated solution based on temperature changes using carboxylic resins is proposed. Experimental results are presented.

Selectivity of phenol–formaldehyde resins and separation of rare alkali metals

Abstract The sorption capacity and selectivity of the chemically stable, macroporous phenol–formaldehyde resins with phenolic ion-exchange groups only, towards alkali metal ions have been studied. The selectivity of these resins towards rubidium and cesium ions were found to be significantly greater than that of the sulfonic, carboxylic, phosphonic, nitrated sulfonic and sulfonic–phenolic ion-exchange resins. The contributions of the ion-exchange and molecular sorption mechanisms to the sorption capacity and the selectivity were determined. The synergetic action of the phenolic active groups on the properties of ion-exchange resins is discussed. The resins with phenolic ion-exchange groups only were found to be very efficient for separation of the rare alkali metal ions.

Heterophase model of swollen cross-linked polyelectrolyte

Abstract In this paper we describe the heterophase model of a swollen particle of cross-linked polyelectrolyte in water. We also propose a new definition of a solution of cross-linked polyelectrolyte. We demonstrate that the activity of water in a solution of cross-linked polyelectrolyte depends on two independent parameters: the number of cross-links in the solution of the polyelectrolyte and the activity of water in the equilibrium state. Using a three-dimensional coordinate system, we illustrate the effect of these parameters on the amount and activity of water in the solution of cross-linked polyelectrolyte. The equilibrium between a solution of low-molecular-mass electrolyte and a solution of cross-linked polyelectrolyte is described from the standpoint of classical thermodynamics. We also present methods to calculate amounts and activities of components in the solution of cross-linked polyelectrolyte. In order to describe a solution of cross-linked polyelectrolyte, in addition to the concept of ‘isotherm of sorption of water’, it is necessary to introduce and define the term ‘isotherm of sorption of electrolyte’. Examples of such isotherms are provided as an illustration. We propose methodologies to experimentally determine several parameters of the model and present the results of calculations of amounts and activities of the components in a solution of cross-linked polyelectrolyte.

The role of temperature in ion exchange processes of separation and purification

The evolution of ion exchange processes for separation and purification of substances by use of the influence of temperature both on the equilibrium and the dynamic properties of some ion exchange resins is discussed. Significant improvement of some ion exchange separations, diminishing of reagents consumption and waste quantities is achieved. In the same way, environmentally non-hazardous reagentless ion exchange methods of divalent and monovalent ionic mixtures separation are developed. This report is based on experimental studies of the equilibrium, dynamic and some other properties of ion exchange resins.

Interaction of cross-linked polyelectrolytes with solutions of low-molecular-weight electrolytes

We offer a method for calculation of the composition and the amount in solution of cross-linked polyelectrolyte. Methods to determine amounts and properties of the components in a solution of cross-linked polyelectrolyte are formulated from the viewpoint of a two-phase model and the law of interphase equilibria. An algorithm to calculate the composition of a solution of cross-linked polyelectrolyte was developed. We present the results of comparison of theoretical and experimental values and show that the heterophase model of the swollen gel can serve as a tool for description of such systems.

Influence of temperature on ion-exchange equilibrium accompanied by complex formation in resins

The paper deals with finding the correlation between the influence of temperature on the ionic selectivity of ion-exchange resins studied experimentally and their chemical structures. The effects of temperature on selectivity of resins are compared with the data for the soluble complexing reagents. The physicochemical basis of the influence of temperature on ion-exchange selectivity is considered.

ION-EXCHANGE METHODS FOR ULTRA PURIFICATION OF INORGANIC, ORGANIC AND BIOLOGICAL SUBSTANCES

ABSTRACT This paper represents a critical review of the applicability of different ion-exchange purification techniques for manufacture of high purity inorganic, organic and biological substances. The review considers both traditional ion-exchange purification methods, such as frontal separation, reverse frontal separation and displacement chromatography, and relatively new ion-exchange fractionation techniques based upon governing the separation process by the modulation of temperature, ionic strength, and some other thermodynamic parameters known to shift the equilibrium in an ion-exchange system to the desired direction. A special attention is payed to the reagentless purification methods, which allow for designing ecologically clean ion-exchange technologies in applying both fixed bed and counter-current modes of operation. The paper comprises numerous examples on ion-exchange ultra purification of rare alkali metals, rare earth metals, freons, liquid crystalline substances, amino acids, DNA, and othe...

Effect of the temperature on the thermodynamic characteristics of the ion-exchange separation of substances on ionites

The basic results on the effect of temperature on the equilibrium and thermodynamic characteristics of ion-exchange systems and the use of this effect in developing reagentless methods for ion-exchange separation are considered.

REAGENT-FREE ION-EXCHANGE SEPARATIONS

ABSTRACT This paper reviews the development of reagent-free (and therefore ecologically clean) ion-exchange separation techniques. These methods are based on the shift of the ion exchanger selectivity induced by the modulation of some physico-chemical parameters of the system such as temperature, solution concentration, pH, etc. This approach avoids the use of auxiliary reagents and additional operations such as the regeneration of ion-exchange resin and auxiliary chemicals for their reuse. It also minimizes the amount of toxic wastes produced.

Kinetics of ion exchange in polyphase systems including crystallizing substances

Abstract Kinetics of ion exchange has been investigated in triphase systems: (1) strong-base anion-exchanger AV-17 × 8 in the CO32− form-CaCI2 solution-CaCO3 precipitate; and (2) sulfonate cation-exchanger KU-2 × 8 in the Ca2+ form-Na2CO3 solution-CaCO3 precipitate, and in quadriphase systems: (1) AV-17 × 8 in the CO3− form-CaSO4 · 2H2O precipitate-CaSO4 saturated solution-CaCO3 precipitate; and (2) AV-17 × 8 in the CO32− form-KU-2 × 8 in the Ca2+ form-Na2CO3 solution-CaCO3 precipitate. It has been shown that in both tri- and quadri-phase systems, the rate of cation exchange is lower than that of anion exchange. The amount of the precipitate crystallizing on the surface of resin beads depends on the type of ion-exchange resin, its granulation and on the ratio of resin components in the case of quadriphase systems with a mixed bed. By varying this ratio and the granulation of the ion-exchangers it is possible to accomplish the precipitation mostly in the anion- or cation-exchanger. Under certain conditions the precipitation takes place mainly in the solution phase. The mathematical model of ion-exchange process accompanied by precipitation on the surface of the resin beads has been proposed. The rate of the ion-exchange process has been assumed to be controlled by diffusion within the porous layer of the precipitate fixed on the surface of the bead. As an example of practical application of the results obtained the method of simultaneous regeneration and separation of mixed bed resins exhausted in a water demineralization process has been proposed.