Cathodic deposition of copper in the presence of aqueous sulfurous acid, bivalent aquacobalt ion, or both using a stainless steel cathode and a graphite anode

Abstract

A study on cathodic deposition of copper in acidic aqueous sulfate solution has been carried out using a stainless steel cathode and a graphite anode. The individual and the combined effects of added [H 2 SO 3и aq] and [Co 2ϩ и aq] on cathode potential, current efficiency, crystal orientations, and deposit morphology have been investigated and are compared. The maximum decrease of ഡ50 pct in cathode potential is more pronounced in the presence of ഡ10.25 g/L of H 2 SO 3 alone in the electrolyte than that (ഡ30 pct) in the presence of ഡ100 ppm of added Co 2ϩ (aq) alone; however, the presence of added Co 2ϩ (aq) along with H 2 SO 3 (aq) does not cause further decrease in cathode potential in comparison to that observed in the presence of only H 2 SO 3 (aq) in the electrolyte. The current efficiency is found to decrease in the presence of [H 2 SO 3и aq] in the range of 1.32 to 30.75 g/L or in the presence of added [Co 2ϩ и aq] in the range of ഡ10 ppm to 600 ppm, while the decrease of about 4 pct in current efficiency is more pronounced in the presence of only H 2 SO 3 (aq) in the electrolyte, it is about 2 pct in the presence of only added Co 2ϩ (aq) in the same electrolyte. The addition of Co 2ϩ (aq) to the electrolyte containing H 2 SO 3 (aq) does not alter the current efficiency (94 pct) of copper at the cathode. The linear sweep voltammetry (LSV) method was used to study the effect of added [H 2 SO 3и aq], [Co 2ϩ и aq], or both, on the copper deposition at the cathode. The presence of each of these two additives or both causes a depolarization effect; the extent of the depolarization depends on the concentration of H 2 SO 3 (aq), Co 2ϩ (aq), and the current density. X-ray diffraction (XRD) data suggest that there is a change in the order of the preferred crystal orientations (viz., from the (220) plane in the absence of added H 2 SO 3 (aq) and Co 2ϩ (aq) to the (111) plane in the presence of added H 2 SO 3 (aq) and Co 2ϩ (aq) in the electrolyte solution) due to a change in the preferred plane of relative crystal growth. Results of scanning electron microscopy (SEM) indicate that cathode deposits of better surface morphology due to small-sized crystallites are found in the presence of added H 2 SO 3 (aq) ϩ Co 2ϩ (aq) in the electrolyte solution.

Effects of Added Chloride Ion on Electrodeposition of Copper from a Simulated Acidic Sulfate Bath Containing Cobalt Ions

“…Although copper leaching and solvent extraction have achieved a state of advanced development, the commercial success of the process is dependent upon the ability to produce high-quality final product through the electrowinning process. The high power consumption associated with this process has been the subject of many investigations in the last few years [2][3][4][5][6]. The attempts made so far are [7] (a) improvement in mass transport for cell operation at higher-current density without significant increase in energy requirement, (e) replacement of the Pb-Sb anode by a catalytic anode for decreasing the oxygen overpotential and many similar aspects.…”