Cathodic refining in molten salts: Removal of oxygen, sulfur and selenium from static and flowing molten copper

The removal of nonmetallic impurities, including oxygen, sulfur and selenium, from molten copper (cathode) was achieved by constant voltage electrolysis in molten BaCl2 and CaCl2 alone, or the eutectic mixture of the two at temperatures slightly higher than the melting point of copper. At the applied voltages (2.1 similar to 2.9 V), the cathodic refining occurred without provoking the decomposition of the chloride salts, demonstrating the cathodic ionization of impurities to be responsible. Further evidence supporting this mechanism came from SEM, EDX and preliminary voltammetric studies. To increase the mass transfer of the impurities in the molten copper during the refining process, a novel recessed channel electrode (RCE) was used. The results have demonstrated the feasibility and efficiency of using this technology in terms of space, time and yield of product, offering considerable advantages over a simple electrorefining cell.