A mathematical model was developed to predict changes in contaminant concentrations with time. and to estimate contaminant fluxes due to migration, diffusion, and convection in a laboratory-scale batch electrolysis cell for the regeneration of contaminated hard-chrome plating baths. The feed and extract compartments of the batch-cell were separated by a Nafion-117 diaphragm. The mathematical model was used to estimate process parameters and physical properties of Nafion-117 membrane from experimental results. assuming quasi-stationary operation. Best-fit ionic mobilities of Cu, Fe, and Ni through the Nafion-l 17 membrane were found to be 5.4, 1.7. and 5.2 x 10(-10) cm(2)/V s, respectively.