Pulsed electrolysis: An efficient approach to enhancing purity from 4N to 6N copper

Abstract

The conventional direct-current (DC) electrorefining process is widely used for the purification of blister copper to achieve high-purity grades. However, this process typically requires extended operational cycles and exhibits limitations in removing trace impurities such as silver and tin. To address these challenges, a pulsed electro-refining method is proposed that achieves enhanced impurity removal efficiency and shorter purification time. The experimental results showed that higher impurities removal efficiency and better appearance of high-purity copper deposits could be reached in the pulse electrolysis process. The total impurities concentration of copper products could be reduced to 0.74 mg/kg after 24 h by pulse electro-refining, which could only reach 1.24 mg/kg by DC electrolysis. Moreover, the silver and tin concentrations decreased by 95 % and 85 %, respectively. In addition, the effects of several crucial conditions during the pulsed electrolysis process were investigated, including pulse current density, pulse frequency, pulse duty ratio, and pulse electrolysis duration. The results indicated that the concentrations of all impurities apart from silicon were reduced and the purity of copper deposits reached 6 N under the experimental conditions of pulse current density of 400 A/m², pulse frequency of 500 Hz, and pulse duty ratio of 50 % after 36 h. In summarily, the pulsed electrolysis process demonstrates excellent efficacy in producing high-purity copper.