Fundamental Application of Basket Electrolysis Method for Black-Copper Anode

Crude copper with a high content of impurities derived from secondary raw materials, known as black-copper, cannot be used in the conventional electrorefining process because of passivation. The current industrial process for black-copper, which involves a combination of high-temperature acid dissolution under pressure, and subsequent electrowinning, results in high power consumption. In this study, the basket electrolysis method was investigated as an alternative process for black-copper. Basket electrolysis experiments were performed using black-copper alloy samples shaped into shot of diameter 2.5 mm. The anodic dissolution behaviors with respect to the connection between the anode and the supporting conductor, anode shape, number of anodes, and anode composition, i.e., with and without Ag, were investigated. Relatively high anodic dissolution ratios, i.e., greater than 70%, were obtained in all cases when multiple-shot anodes with 10 or more shots were used. The anode film formed on the black-copper surface is thought to contribute to the maintenance of electrolysis by providing ion-conducting paths via electrolyte-filled pores, and electron-conducting paths via metal particles. This enabled application of the basket electrolysis method.