The extraction of proline with a solution of dinonylnaphthalenesulfonic aci
d in octane, a liquid cation exchanger, from aqueous and aqueous salt-conta
ining solutions was investigated. It was shown that the dependence of the s
electivity coefficient on the equivalent fraction of proline in the liquid
cation exchanger phase is adequately described by a mathematical model prop
osed previously under the assumption that at least four nearest neighboring
ions affect the interaction energy of the cation and the anion of proline
on a given exchange site.