Binary and ternary cation exchange on strong acid cation exchange resin involving Na, Mg, and Zn in single and binary backgrounds of chloride, perchlorate, and sulfate

A systematic study with the negatively charged cation-exchange resin Amberl ite 200 was performed to investigate the influence of anion type on cation exchange. A comprehensive data set was obtained for binary and ternary cati on exchanges involving Na, Mg, and Zn on a strongly acidic, sulfonate catio n-exchange resin in electrolyte systems with the single anions chloride, pe rchlorate, and sulfate, and with 1:1 mixtures of them at two total cation c oncentrations of 0.05 and 0.2 N. The binary and ternary cation exchange dat a exhibited internal consistency in that Mg and Zn were selected over Na to a comparable degree. The binary and ternary cation exchange data also indi cated clearly an effect of anion type, with reduction in selectivity of Mg and Zn relative to Na in the presence of more strongly complexing anions su ch as sulfate. The effects of anions in cation exchange may be ascribed in part to their association with cations in solution, as demonstrated by appl ication of conventional mass action models for ion exchange with considerat ion of solution-phase speciation. The ability of mass action models includi ng solution speciation to predict binary and ternary cation exchange in dif ferent anion backgrounds based on model parameters extracted only from data obtained in chloride background was also tested. The Gaines-Thomas model p rovided the best predictions of binary and ternary cation exchange on the s ulfonate resin for the different anionic media and ionic strengths. Mass ac tion models can account at least approximately for the effect of anion type on cation exchange if solution speciation and activity correction are prop erly considered.