ADSORPTION BEHAVIOUR OF MERCURY AND SOME METAL IONS ON CATION EXCHANGE RESIN DOWEX 50 WX8 (NH4+ FORM) FROM AQUEOUS ACETONE-AMMONIUM PROPIONATE MEDIA.

Chemistry

In the field of inorganic separations, the incentive to explore the use of non-aqueous or mixed solvents has been the enhanced selectivity, discovered quite early in such media for Z eolites[1] and ion exchange resins [2]. The partial substitution of aqueous solution by organic solvent produces a number of changes in an exchange system, such as , change in the solution structure due to the interaction between water and the organic solvent, change in the hydration and salvation of the electrolyte, change in the solvent composition in the resin phase , change in the activity coefficients of the electrolyte in the solution phase as well as in the resin phase, change in the complexation of the metal ion and change in the extent of invasion by an electrolyte. All these changes are mutually dependent and affect the distribution of the metal ion. From the investigations of ion exchange in mixed solvents, it is apparent that the adsorption equilibrium depends markedly on the properties of the organic solvent and reactions with the resin and electrolytes which determine the equilibrium. A variety of complexing media have been used to study the metal ion exchange on cation exchangers and their uses has been done in many analytical separations. Almost the mineral acids and their salts from a class of complexing agents which has been used by many workers. As the presence of water miscible polar solvents proved to be advantageous in the metal ion exchange in complexing media. The use of mineral acids and their salts has been done in a variety of non awuous and mixed awueous solvent. Firtz et al [3] separated many metal ions using 0.1 or 1 M hydrofluoric acid as the eluting agent, the method of separation of Al3+, Ti4+ , V4+ and Nb5+ ions was studied by Dowex 50 WX8 resin in H + and ethylene di -ammonium forms. Yoshimo and Koiima[4] and Strelow [5] separated cadmium from zinc and other metal ions by eluting them with 0.5 M hydrochloric acid. Fritz et al separated Al3+,Cu2+, Cd, Co2+, Zn2+ and Th4+ by using nitric acid. The studies indicated that when nitric acid is used with non-aqueous solvent, larger volume of eluent is required for quantitative elution and a slower flow rate had to be employed. Strelow[6] Mann and Swanson [7] measured the equilibrium distribution coefficients which are a useful guide to possible cation exchange separations in aqueous solution.

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