Anode-support system for the direct electrorefining of cement copper Part I: Process conditions using horizontal rotary cathodes

This paper describes a preliminary study towards a modified anode-support system for the direct electrorefining of cement copper. The proposed system is an alternative process for small mines that produce cement after leaching of copper oxide minerals. It is feasible to utilize a cell provided with a horizontal AISI-316 stainless steel mesh covered with a layer of cement copper as anode system. As cathode system, several horizontal rotary cylinders of AISI-316 stainless steel can be used. The rotary cylinders, partially immersed in acidic copper sulphate electrolyte, must have an internal electrical contact with a copper shaft and two or more isolated slots at the surface to permit the stripping of the copper deposits in the form of thin sheets. The cement copper must be maintained wet to avoid rapid oxidation. The use of pulsed current permits control of the formation of a non-conductive copper sulphate layer on the cement surface, avoiding a continuous increase in cell voltage. As operating conditions a solution of CUSO₄.5H₂O (160 g dm^–3) and H₂SO₄ (50 g dm^–3) with j_c = 5.0 A dm^–2, T = 40 °C, u = 200 rpm; and pulsed current with t_d = 3 min and t_d/t₀ = 20 can be used. At this stage of the study cement copper (90–95% purity) was utilized.