EFFECTS OF IRON AND MANGANESE IONS ON POTENTIOSTATIC CURRENT TRANSIENTS FOR COPPER ELECTRODEPOSITION

摘要

The effects of iron and manganese ions 6n potentiostatic current transients for copper electrodeposition are investigated by recording the current-time curves for acidic copper sulphate electrolyte solutions and a copper bioleaching solution. For copper electrodeposition from the acidic copper sulphate electrolyte solutions, the variation of the current density with time indicates the charging of the electrical double layer and the formation and growth of copper nuclei. The addition of Fe~(3+) ions inhibits the reduction of Cu~(2+) ions to Cu~+ ions in the solutions since the Cu~+ ions generated during copper electrodeposition are oxidized back to the Cu~(2+) ions by the Fe~(3+) ions. Likewise, the addition of Mn~(2+) ions hinders the formation and growth of copper nuclei. For copper electrodeposition from the bioleaching solution, the current density decreases to a minimum and then increases slightly when the applied potentials are 0.20 and 0.25 V. The copper electrodeposition process in the bioleaching solution experiences three steps: the formation of 2D copper clusters, the transition from the 2D copper clusters to 3D supercritical nuclei and the growth of the 3D supercritical copper nuclei.