HIGH-CURRENT DENSITY COPPER ELECTROREFINING

High current density copper electrorefining was studied on a large laboratory scale at the Universite Libre de Bruxelles, Belgium, under contract to Metallurgie Hoboken-Overpelt. A two-cathode (length, 1 m; height, 0.2 m) channel cell was used at 2000 A/m2 with an electrolyte flow rate of up to 1.8 m/s. The cathodes produced are of electrorefined grade; metallographic structure and surface roughness are controlled to a depth of 1.3 cm (single-side deposits); silver levels in the cathode are regulated by the presence in solution of Cl- and Br- ions; organics must be used at very low concentrations (around 0.1 mg/l, with a consumption of about 0.01 mg/l/h). The required concentrations of additives were established according to a well-defined strategy based on the consumption of organics at the cathode by a mass transfer-limited process.