ELECTROWINNING OF NONNOBLE METALS WITH SIMULTANEOUS HYDROGEN EVOLUTION AT FLOW-THROUGH POROUS-ELECTRODES .3. TIME EFFECTS

The electrowinning of zinc from a recirculating alkaline zincate solut ion at a flow-through porous electrode was investigated. Experimental results were obtained to test the predictions of a mathematical model. The effects of electrolyte flow rate, cell current, and electrode thi ckness on the concentration-time relations and coulombic efficiency-ti me relations were studied. The experimental results show that the high est recovery rate was obtained at both high flow rates and cell curren ts. There is, however, a practical Limit for increasing both the cell current and the electrolyte flow rate. Reasonable agreement between th e model predictions and experimental results was obtained. A case stud y is presented to show how the model equations are used to predict the relationship between time, cell current, flow rate, and coulombs pass ed which are required to recover 95% of the zinc content of the electr olyte.