Univalent cation-exchange in organic solvent water and organic solvent-water-phenol mixtures

Selectivity coefficients, K(H)(M), for the exchange of alkali metal ions and ammonium ions with the hydrogen form of ZeoKarb 225 cation-exchange resin have been determined in various organic solvent-water and organic solvent-water-phenol mixtures. There is an increase in K(H)(M) in passing from purely aqueous conditions to media of increasing organic solvent content, frequently with the effect of producing magnified differences and selectivity reversals between one ion and another. The results are discussed in terms of the relationship between K(H)(M) and the reciprocal of the dielectric constant of the medium and also in the light of free energies of transfer of cations between methanol-water systems. The effect of phenol giving a lowering of K(H)(Cs) in methanol-water, of K(H)(K) and K(H)(Na) in ethanol-water and of K(H)(Na) and K(H)(L1) in acetone-water systems cannot be fully reconciled with the mechanism involving bonding proposed by earlier workers.