Influence of oxygen reduction in the electrowinning of zinc

Abstract

The electrodeposition of zinc from an acid zinc sulphate electrolyte similar to those used in commercial zinc electrowinning has been studied at a rotating aluminium cathode. The presence of dissolved oxygen is shown to lower the current efficiency for zinc deposition, and the influence of current density, rotation speed, and oxygen concentration indicates that the mass-transfer-controlled electrochemical reduction of oxygen is responsible. The mass-transport parameters of oxygen in the zinc electrolyte are deduced from voltammetric studies on carbon, aluminium, and platinum cathodes. The influence of dissolved oxygen on current efficiency in a practical electrowinning cell is estimated to be in the order of 1%, with the main uncertainties being in the mass-transfer coefficients and in possible oxygen supersaturation.