Evaluation of Permanent Cathode Technology for Copper Electrowinning at Rustenburg Base Metals Refinery

Significant advantages of permanent cathode technology have been demonstrated for copper electrowinning. The copper starter-sheet operation at Rustenburg Base Metals Refinery is labour-intensive, and performance is heavily dependent on structural integrity and equipment reliability. The viability of sustainably converting this low current density operation to use of permanent cathodes was evaluated. An 18-harvest cycle pilot trial was carried out under existing plant operating conditions to assess the ability to consistently produce good quality copper. This paper describes the testwork results, including the installation of new cell-top furniture and busbars. Good quality copper was produced from standard (low) current density (<150 A/m²) cycles; unfavourable results were observed during higher current density cycles (290 A/m²). Up to 92.5% current efficiency was achieved, with minimal scrap production. For the current electrolyte composition, the operational current density, size of Pb–6%Sb anodes, type of cathode edge strips, effect of over-plating, and the use of fibreglass electrode-stabilising plates installed at the base of the electrowinning cells proved to be important conversion considerations.