Electrowinning of copper from sulfate electrolyte in presence of sulfurous acid

Abstract

The electrowinning of copper from acidic sulfate solution in the presence of sulfurous acid using a graphite anode was investigated. The effects of operating variables including sulfur dioxide concentration, copper concentration, sulfuric acid concentration, current density and temperature on the cell voltage, anode potential, power consumption, current efficiency, deposit quality, surface morphology, crystallographic orientations and polarisation characteristics were studied. Other anode materials such as Pb/Sb, Pb/Ag, Ti and Ti-IrO2, were also used to examine their effects on electrocatalytic activity for oxidation of SO2 and deposit quality. A rectangular stainless steel cathode of length 8 cm, width 5 cm and thickness 2 mm was used for copper electrowinning. Increases in SO2 concentration, copper concentration, sulfuric acid concentration and temperature lower the power consumption. These variables have no effect on the current efficiency of copper deposition. The presence of SO2 in the copper electrolyte affects both the cathodic and anodic polarisation curves. In addition, it causes shifting of preferred orientations from (220) (111) (200) (311) to (111) (200) (220) (311). Changes in crystallographic orientation are also seen in the surface morphology of deposited copper. It is found that minimum power consumption together with maximum current efficiency and improved surface morphology can be achieved using a graphite anode. (C) 2001 Elsevier Science B.V. All rights reserved.