Electrolyte dialysis using charge-mosaic membranes

Abstract

Charge-mosaic membranes represent a subset of bipolar membranes. They contain anion- and cation-permeable domains. Anions and cations can pass through the membrane without violation of microscopic electrical neutrality. Consequently, much higher rates of transport of electrolytes compared to non-electrolytes of the same size are obtained. The ability of charge-mosaic membranes to separate low molecular weight electrolytes from non-electolytes of similar size could lead to applications such as desalination of amino acids and other organic species. Here we have determined rates of CoCl2 (2:1 electrolyte), CuSO4 (2:2 electrolyte), NiSO4 (2:2 electrolyte), and NiCl2 (2:1 electrolyte) transport through a charge-mosaic membrane made of microspheres under dialysis conditions. The results are compared to literature values for transport of KCl, a monovalent 1:1 electrolyte. Our results indicate that the mass flux of salt is the same for all four salts and for KCl. In all cases negative osmosis is observed where th...