Understanding the impact of poly(allylamine) plasma grafting on the filtration performances of a commercial polymeric membrane

Abstract Commercial membranes often exhibit difficulties in rejecting specific ionic species, and especially multivalent cations, due to their usual negative charge. To face this drawback, it is proposed here to functionalize the membrane surface by allylamine plasma polymerization. The impact of this modification on both permeation flux and ion rejection is investigated for single salt solutions and ion mixtures. It is shown that the membrane behaves like a positive membrane from the point of view of cation rejection but the negative charge (and the corresponding electrical field) inside pores leads to high rejection of divalent anions like a negative membrane. This allows a high selectivi…