CURRENT-VOLTAGE CURVES OF COMPOSITE BIPOLAR MEMBRANE IN ALCOHOL-WATERSOLUTIONS

The current-voltage curves of a composite bipolar membrane (CBM) were experimentally measured for the various mole fractions of methanol-wat er, ethanol-water, and n-propanol-water mixed solution systems. In eac h solution system, 0.1 mol/L LiCl was used as the electrolyte. The exp erimental results showed that a CBM has the characteristics of a bipol ar membrane. The current-voltage characteristics were analyzed using M afe and Ramirez's ion transport theory by applying the chemical reacti on model in the intermediate region, and the theoretical calculations were able to well explain the experimental results. The current-voltag e curves show that the maximum local effective value of a CBM resistan ce will increase with an increase in the mole fraction of alcohol. Thi s phenomenon is due to the fact that the dissociative ability of an al cohol is much weaker than that of water; thus, the current is mainly i nduced by the water splitting. However, methanol splitting was observe d in the case of the LiCl-methanol solution because of its somewhat la rge autoprotolysis constant.