Abstract

Anodic dissolution of synthetic chalcocite (previously obtained by copper precipitation with S and SO2 in ammonia media) in two different electrolytic cells is described. One cell has a circular graphite anode placed horizontally, surrounded by a stainless steel cylinder as cathode, and the other has a rectangular basket-shaped graphite anode, with a rectangular stainless steel cathode placed in front of it. The electrolysis was performed at 0.2 A and 50 °C, the electrolyte contained 20 to 40 g L-1 of Cu and 100 to 160 g L-1 of H2SO4, and the initial reactions took place at low potential (0.4-0.6 V) until the transformation of Cu2S into CuS, detected by the considerable increase in cell potential. Anodic and cathodic efficiencies greater than 100% and 95%, respectively, were obtained. The hight anodic efficiencie is due to faradic and chemical dissolution too. It is also shown that the (CuS) produced as waste material can replace elemental sulphur as copper precipitating agent in ammoniacal media.