Evaluation of the chemical stability of some membranes in vanadium solution

The chemical stability of Daramic®, modified Daramic® and several commercial ion exchange membranes was studied in the vanadium redox battery (VRB). The Selemion® CMV membrane showed the lowest chemical stability in the VRB, while Nafion® 112 and New Selemion® (type 2) showed excellent stability. The composite membrane prepared by crosslinking of Daramic® with divinylbenzene (DVB) showed good chemical stability similar to the Selemion® AMV membrane. Sulfonation of the composite membrane and AMV membrane did not improve their stability in the vanadium solution. It was found that the weight loss of the membranes is almost proportional to the conversion of V(v) ions to V(iv) ions in the test solution showing that the chemical degradation is associated with the oxidation of the polymeric membrane material by the V(V) ions in the positive half cell electrolyte. The Nafion® 112 membrane was found to be susceptible to fouling which can be reversed by simply soaking in H2SO4 solution.