Convective electrodiffusion processes through graft-modified charged porous membranes

Convective diffusion and electrophoresis across a charged porous membrane s howing variable permeability properties were studied. The membrane used was prepared by grafting poly(acrylic acid) (PAA) onto a porous polyvinylidene fluoride (PVDF) membrane. The degree of grafting was selected to be relati vely low, 18 wt%, to compromise between the ion selectivity and hydraulic p ermeability of the membrane. The possible electric field induced effects on the membrane permselectivity were examined after the membrane had been cha racterized by convective diffusion and concentration cell potential measure ments. The measured electrophoresis data, however, could be modelled using the extended Teorell-Meyer-Sievers theory, which indicates that the membran e studied shows no variable permeability behaviour with respect to a weak a pplied external electric field. This conclusion was also further confirmed by separation experiments carried out with ternary salt solutions. (C) 1999 Elsevier Science S.A. All rights reserved.