摘要:

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 other substances.

ISSN:0736-6299    

DOI:10.1080/07366299808934527

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The paper critically reviews the existing methods which are applied for the sorption purification of industrial effluents, waste waters and technological solutions from polyvalent metal ions (such as mercury, cadmium, calcium, copper, nickel and zinc), and also describes the novel purification processes developed recently by the authors. Particular attention is paid to the optimization of purification processes through the use of specially selected ion-exchange materials with the optimal equilibrium, kinetic, mechanical and other properties, application of the most effective apparatus design, and optimization of the process flowsheets. The approach proposed is illustrated by the results of both laboratory and the pilot-plant experiments including the final flowsheet of the purification processes. One of the examples given is the tailor-made modification of the commercial VP-1AP polyvinylpyridine resins with l,3-dichlor-5-dimethyl hydantoin, which combines high selectivity and oxidation capability towards different mercury species (including mercury organic compounds) in the same ion-exchange material. The paper includes also examples of purification of the native waste waters of different types from mercury and cadmium on organic and inorganic ion exchangers; deep purification of the NaCI brines from calcium on polyampholytes, purification of rinsing waters of electroplating industry from copper, nickel and zinc on mixed beds of ion exchangers, and other information which may be of interest for environmental and applied chemists.

ISSN:0736-6299    

DOI:10.1080/07366299808934528

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The paper describes the new phenomenon called Ion-Exchange Isothermal Supersaturahon (IXISS). This effect is observed for a number of ion-exchange systems, where frontal or reverse frontal separation is accompanied by the formation of stable supersaturated solutions of slightly soluble substances in the interstitial space of ion-exchange columns. After leaving the column a supersaturated solution crystallizes spontaneously, which allows for designing practically ideal ion-exchange process where a crystalline product is obtained right after the ion-exchange purification cycle. The paper comprises results on experimental investigation of IXISS of amino acids (e.g., such as glutamic, aspartic and some others), calcium and magnesium salts (sulfates and carbonates), and some other substances. The mechanisms of stabilization of supersaturated amino acid solutions in the interstitial space is proposed and confirmed experimentally. Methods for identification of substances exhibiting the IXISS effect and practical application of the IXISS phenomenon for separation and ion-exchange synthesis of substances and some other problems are discussed.

ISSN:0736-6299    

DOI:10.1080/07366299808934529

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper summarises the results obtained by studying a new phenomenon in the area of ion exchange and ion exchangers, namely, the formation of clathrate-like crystalline polyhydrates in the ion-exchanger phase. Interaction of swelling water molecules in ion exchangers of certain types (e.g., polyacrylic) has been shown to cause the formation of a clathrate (cellular) structures at temperatures above 273K which in turn leads to the formation of inclusion compounds. The polyhydrate structure can be described as a framework of water molecules arising through the combination of single or joined polyhedra (“host”) containing the matrix of the ion exchanger along with fixed- and counter-ions ( “guest”) in their cavities. The melting (decomposition) temperature of solid clathrate polyhydrate depends on the nature of “guest” components and, for the ion exchanger of a given type, also on the nature of the counter-ion. The paper reports the results obtained by studying clathrate formation, composition and structure of ion-exchanger hydrates by using DTA; DTA under pressure; NMR; electric conductivity techniques, and by absorption of “help gases”. The purposeful synthesis of clathrate-forming ion exchangers and their application for determination of swelling pressure in resin beads; for separation and purification of ionic and gaseous substances, and for solution of some other theoretical and practical problems of ion exchange are also described. An interpretation of Pauling theory of clathrate anaesthesia is discussed within the frame of the results obtained.

ISSN:0736-6299    

DOI:10.1080/07366299808934530

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper reviews the properties of complex forming ion exchangers (CFIE) and those of the ion exchanger complexes (IEC) with transition metal ions. It is mainly dedicated to the development of a novel approach in characterizing IEC which is based on the consideration of CFIE as three-dimensional polymeric ligands. The approach is illustrated by the results obtained by studying the specificity of complex formation with CFIE of different types, the structure, properties and possible applications of IEC as anion exchangers, as electron exchangers, as ligand exchangers and some others. A particular attention is paid to the tailored synthesis of the IEC with desired properties such as the composition of the statistically-average coordination center, the distribution of metal ions along the polymer chain, etc., and to their application as catalysts which combine the high selectivity and activity of the homogenous metal-complex catalysts with the technological convenience of the heterogeneous ones. The application of the IEC as convenient models for bio-catalysts (metalloenzymes) is also discussed.

ISSN:0736-6299    

DOI:10.1080/07366299808934531

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The diffusional model for the intraparticle ion exchange (IE) kinetics in selective ion exchangers is presented. The model develops the phenomenological formulation based on the irreversible thermodynamics and includes mass balance equations with description of ion fluxes by the Nernst-Plank relations. The model is based on the supposition that during the exchange RA+B = RB + A involving a chemical reaction of counter-ions (B and A) with the resin site R, diey can exist in the exchanger in two states, namely “free” and as the species formed by their combination with fixed groups R. Counter-ions B and A are considered to be immobile while “bound” and to move unimpeded while “free”. The mathematical formulation of the IE kinetic process in this case is described by a system of two nonlinear diffusion equations in partial derivatives where the effective self diffusion coefficients Diiand the cross interdiffusion coefficients Dijdepend on the concentration of the diffusing counter-ions (B and A) and coions Y, and also on the values of equilibrium constants KRB and KRA describing the stability of RB and RA complexes in the ion exchanger phase. As the result, the ion fluxes are described within the generalized Fick formulation. Fickian diffusivities Dijcompose 2×2 diffusional matrix with determining each of them through the individual diffusivity Diof the ions B, A and F. The set of diffusional equations along with the appropriate initial and boundary conditions solved by using a computer gives transient concentration profiles which compose concentration waves in the ion exchanger bead. For various combination of diffusional and selectivity factors the concentration waves in the bead have been presented in the pseudo 3dimensional space {concentration - radius - time}. This presentation simplifies the interpretation of the process and makes it visual. It is shown that the difference both in concentration waves profiles and rate between forward and reverse exchange of two counter-ions may arise not only from unequal diffusion coefficients but also from unequal dissociation constants of the complexes formed with the fixed groups.

ISSN:0736-6299    

DOI:10.1080/07366299808934532

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper reviews the results obtained by studying Surface Impregnated Sulfonate Ion Exchangers (SISIE) obtained by modification of macroporous or gel polysterene-divinylbenzene polymers with toluene solutions of dinonytnaphihalene sulfonic acids. Capacities of SISIE of the first type are directly proportional to the concentration of the modifying solution and to the specific surface area of the matrix. Capacities of gel SISIE are much less than those of macroporous samples and depend on the crosslinking of the matrix. Stabilization of SISIE capacity and improvement of their kinetic properties can be achieved using “wet drying ” technique. Successive impregnation of the same SISIE sample may be used to increase the capacity of the resin. The ion-exchange properties of SISIE are mainly determined by their micellar structure which also defines the areas of possible applications of these ion-exchange materials such as, e.g. ion chromatography and some others Several models have been successfully applied to describe the features of ion exchange processes on SISIE. Application of SISIE as convenient model systems to study aminecarboxylate interaction of amino acid molecules is illustrated by suspension effects measured in SISIE-zwitterlyte and SISIE-HCI suspensions and by the results obtained by the laser-acoustic study of these systems.

ISSN:0736-6299    

DOI:10.1080/07366299808934533

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor