Current paths and electrolysis efficiency in bipolar packed-bed electrodes

Abstract

The characteristics of bipolar packed-bed electrodes were studied by using copper deposition reaction from a copper sulfate solution. Ferrite pellets were used as a particulate phase and were packed in three kinds of mode. The Faradaic current in the particulate phase, the by-pass current in the electrolyte phase and the short-circuiting current were measured separately. The minimum bipolar cell voltage was a function of decomposition voltage, distance between two plate electrodes, pellet diameter, and solid holdup. For regularly packed bipolar electrodes, the interaction between Faradaic and by-pass current was small, and a simplified parallel current model is proposed. For randomly packed bipolar electrodes, the interaction was not negligible at higher cell voltages. The minimum value of energy consumption was observed at a particular cell voltage which was a function of pellet size and packing mode. Because of increase in the short-circuiting current due to copper deposition, the energy consumption in the randomly packed bed increased with increase in electrolysis time. The regularly packed bed where the direction of current was parallel to the plain faces of the pellets was found to be the most efficient under the present experimental conditions. © 1982, The Society of Chemical Engineers, Japan. All rights reserved.