Electrowinning of Copper from Dilute Sulfate Leachate of Oxide Copper Ore from the Sepon Mine, Lao PDR

Abstract

Electrowinning of copper from dilute copper sulfate leachate (13.7 gCu/L) was performed in an electrolytic cell with stainless-steel as a cathode and lead-silver alloy as an anode. Effects of various parameters including cell voltage (2-4.5 V), time (1,800-9,000 s) and temperature (25-75 °C) on current efficiency, deposit quality and surface morphology of copper deposits were studied. Atomic adsorption spectroscopy (AAS) was used to analyze the electrowinning products such as copper sulfate solution, copper-cathode and spent electrolyte. The morphology of deposited copper on cathode was examined by using scanning electron microscopy (SEM). For single-stage electrowinning, the optimum condition was found at cell voltage of 3V, electrowinning time of 3,600 s and temperature of 55 °C, by which 98% current efficiency, 95% copper grade and 28% yield with relatively smooth deposit film of copper on the cathode were obtained. After that the efficiency, the copper grade and yield of second, third and final stages of electrowinning were sharply decreased from 96.7, 94.5 and 84.5% on the efficiency; 87.8, 87.6 and 80.3% grade; and 28.1, 27.4 and 24.5% yield in respectively. It was found that the overall stage of copper electrowinning was recommended with the total 94.4% yield of copper, and the remaining copper content in the tailing solution of 0.76 gCu/L. Moreover, surface morphology results that the surface roughness tented to increase with decreasing the temperature. Found that the temperature is a key parameter for both grade and formation of crystal copper at the cathode. Suggested that to increase the copper cathode purity, a solvent extraction should be used by increasing the sulfate concentration, say 50 g/L, prior to win the copper metal effectively.