Effect of the Membrane Surface on Performance Improvements to Anion Exchange Membranes for Electrodialysis through Layer-by-layer Deposition

摘要

To investigate the effect of the membrane surface on improvements to monovalent anion selectivity and antifouling potential of anion exchange membranes for electrodialysis, a Neosepta ACS monovalent selective anion exchange membrane surface was modified by layer-by-layer (LbL) deposition. The modification used poly(sodium 4-styrene sulfonate, PSS) as the polyanion and poly(allylamine hydrochloride) as the polycation. The results were compared with those for a Neosepta AMX standard anion exchange membrane. For AMX, the monovalent selectivity increased with the number of layers and became constant above 15 layers, with the antifouling potential being a maximum at seven layers (PSS top layer). On the other hand, for ACS, the monovalent anion selectivity did not depend significantly on the number of layers. The antifouling potential was at a maximum with the first (PSS) layer. Thus, the effect of surface modification by LbL deposition on membrane performance depended on the membrane surface even if the membrane surface was treated by the same procedure. This behavior is due to the difference in the formation mechanisms of the polyelectrolyte multilayer in the first few layer pairs.