STUDIES OF EXTRACTION EXCHANGE EQUILIBRIA - PB(II)-CD(II) EXCHANGE IN THE CCL4-XANTHATE/WATER SYSTEM

An extraction exchange equilibrium between cadmium xanthate in carbon tetrachloride and lead ions in water at pHs 5 and 7.5 was studied at 25+/-2 degrees C. The exchange isotherm was used to calculate the separation factor S-Pb/S-Cd. The thermodynamic equilibrium constant and corresponding free-energy change per mole of exchange were calculated using the relevant analytical data and activity coefficients of the electrolyte ions in the aqueous phase and of the xanthate bound ions in the carbon tetrachloride phase. Non-ideal behaviour of the CCl4-xanthate phase was also ascertained. From the present study it appears that the phenomenon may be treated similar to ion-exchange processes in synthetic organic ion exchangers.