Validation of a vertical channel flow cell for scalable electrowinning studies

A two-compartment vertical channel cell with controlled electrolyte flow and planar cathode surface of adjustable height was constructed. Unlike small cells with only natural mixing, this arrangement allowed simulation of the effects of turbulence over the surface of industrial cathodes. A benchmark zinc electrowinning process has been used to evaluate the scalability of current efficiency performance in this cell. For a 200 cm² cathode, experiments simulating an industry benchmark process without organic additives gave a value for Wark's constant (W) identical to that calculated from previously reported plant data, at both high and low Reynolds numbers (Re). In addition, a uniform morphology was observed over the height of the cathode. In contrast, as the cathode size was reduced, the observed value of Wark's constant decreased from the value for full-scale plant cells and the deposit morphology became non-uniform. These effects were magnified at high Re. The 200 cm² channel cell is expected to be particularly useful for the study of cell additives, for which the effects of electrolyte flow over the cathode surface can be very important.