Salt permeation through cationic membranes with quaternary ammonium groups of different alkylchain lengths

Abstract

Cationic membranes were prepared by quaternizing poly(chloromethylstyrene-codivinylbenzene) membrane with triethyl, tri-n-propyl and tri-n-octyl amines. The permeabilities of NaCl, NaBr, NaI and NaNO 3 were measured. The dependence of the permeabilities on the upstream salt concentration was not of a simple Donnan exclusion type, which is unusual. The permeability of the membrane quaternized with triethylamine for NaI showed a marked decrease with upstream salt concentration up to ca. 0.1 mol/l and leveled off thereafter. The permeability of the membrane quaternized with tri-n-propylamine for NaCl, NaBr and NaNO 3 showed minima at relatively low upstream salt concentrations. These results, together with the sorption isotherms, were qualitatively discussed in terms of dual sorption and diffusion modes of the salts