Modeling Zinc Electrowinning for Current Efficiency Prediction Based on Nernst-Plank Equation and Electrode Gas Evolution Reaction Kinetics

Abstract

Zinc electrowinning is by nature complex, involving the electrodeposition of Zn ions on cathode, oxygen evolution on the anode, as well as the hydrogen evolution on the cathode as a side reaction which decreases the current efficiency and increases the energy consumption while improving local mass transport. Because of the capital-intensive features and the low efficiencies of experimental research approaches, modeling and simulation have become a promising way to study the electrowinning processes. The coupling of gas-liquid two-phase flow from gas evolution with the electrochemistry process, however, is challenging to simulate. In this paper, an approach of building a comprehensive Zn electrowinning model based on COMSOL Multiphysics was introduced. Further, the basic model results in velocity field, concentration distribution, gas fractions, and current efficiency were demonstrated and discussed. In addition, validation of the current efficiency predictions from the model was performed through a comparison with experimental test data.