摘要:

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.

ISSN:0736-6299    

DOI:10.1080/07366299908934634

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper reviews the results obtained by studying the dual-temperature ion-exchange fractionation (DTIXF) technique. The DTIXF is based on the use of different affinity at different temperatures of ion exchangers towards ions to be separated. This technique allows to design absolutely reagentless and, as a result, wasteless fractionation technology. The review considers the temperature dependencies of selectivity of commercially available ion-exchange (LX) resins towards components of ionic mixtures of different complexity starting from binary model systems up to naturally existing nonacomponent effluents. A novel approach for predicting the temperature sensitivity of a given LX system is presented and discussed. The same approach has been shown to be applicable for the design of IX resins with temperature-dependent selectivity. The paper also reports the results obtained in the practical application of DTIXF technique for concentration of magnesium from seawater and copper from acidic mine waters. The flowsheets of DTLXF processes are proposed and discussed.

ISSN:0736-6299    

DOI:10.1080/07366299908934635

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper reviews the results obtained by studying the sorption of physiologically active substances (PAS) of different types such as, amino acids, nucleotides and melanoidins on ion exchangers and non-ionogenic sorbents. The review is mainly focused upon die mechanisms of interaction of PAS molecules in the sorbent phase. The contribution of ion-ionic, ion-molecular and intermolecular interactions to the overall sorption effect is discussed. The results of studying ion-exchange isothermal supersaturation of amino acid solutions on anion exchangers are reported and discussed. The mechanisms of aging of ion-exchange materials in the course of recovery of PAS from fermentation broths and hydrolysates are proposed.

ISSN:0736-6299    

DOI:10.1080/07366299908934636

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The paper reviews the current state-of-the-art of the kinetics and dynamics of redox soiption. The comparison of existing and proposed theoretical models in description of experimental results obtained by studying different redox processes on redoxites, i.e. sorbents with functional redox centers, is presented and discussed. The practical application of the results obtained is demonstrated.

ISSN:0736-6299    

DOI:10.1080/07366299908934637

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper discusses a novel approach for description of ion-exchange processes accompanied by substantial sorption of coions by using the new generalized notations such as “the superequivalent ion exchange” and.“the superequivalent sorption”. The thermodynamic description of superequivalent exchange as a general case of ion-exchange process is based on the non-osmotic theory of ion exchange. The general methods for calculation of ion-exchange constants and activities of ions in the resin phase are considered and discussed. A new method for calculation of these quantities based on the necessaiy and sufficient thermodynamic description of an ion-exchange system is proposed. The method gives new possibilities to verify the thermodynamic compatibility of the experimental results. The proposed theory has been applied to treat experimental results obtained by studying the ion-exchange equilibrium in CaCl2- NaCl - H2O system on Dowex 50×8, KU-2×8 and Dowex 50×2 resin in a wide range of compositions. A new method for the graphical presentation of ion-exchange equilibrium data in the form of the isotherm cross-sections is proposed and discussed. The comparison of the description of ion-exchange equilibrium in the system under study in terms of the absolute and relative (“Gibbs excesses”) sorption values of all system components (including counterions, coions and water) has been carried out. The results of calculation of ion-exchange constants, activities and activity coefficients of resinates accomplished by different methods are presented and discussed. A possibility to model ion-exchange isotheims and activity coefficients of resinates is demonstrated and discussed.

ISSN:0736-6299    

DOI:10.1080/07366299908934638

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper discusses the problem of rigorous thermodynamic description of ionic systems in terms of ions as system constituents. This description can be based on die use of either electrochemical potentials (ECP) as a whole (without their division into chemical and electrical constituents), or twin chemical potentials (TCP) concept (introduced by the author) as thermodynamic driving forces of mass-transfer processes in ionic systems, including ion exchange. The main advantages of the approach proposed in comparison with traditional description of ionic systems is demonstrated and discussed.

ISSN:0736-6299    

DOI:10.1080/07366299908934639

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor