Electrodeposition of Zinc from Sodium Zincate/Hydroxide Electrolytes in a Spouted Bed Electrode

Zinc has been electrodeposited from sodium zincate/hydroxide electrolytes in a spouted bed electrode (SBE). The anticipated application is the removal of zinc from steel degalvanizing electrolytes. A number of short-term (2 to 3 hours) batch experiments have been carried out to determine the effect of design and operating parameters (e.g., current density and temperature) on cell performance, as reflected in the measured cell voltage and current efficiency. A significant effort was devoted to discovering a suitable diaphragm material. A combination of two materials was found to give a stable and acceptable cell voltage. In short-term runs, this combination gave DC energy consumptions of 2.3 to 2.5 kWh/kg zinc at current densities of 2500 to 4000 A/m2. Two long-term runs were carried out, the longer being of 82-hour duration to grow particles from 0.4 mm to approximately 1 mm (i.e., by roughly a factor of 15 in mass) and from 1 mm to approximately 3 mm (factor of 27). Current efficiencies and energy consumptions were comparable to those in the shorter runs; the particles produced had a metallic appearance and were not friable. Auxiliary experiments were carried out to probe the potential distribution in the SBE.