Augmenting metal leaching from copper anode slime by sulfuric acid in the presence of manganese(IV) oxide and graphite

초록

Copper anode slime (CAS) is a solid byproduct of copper electrorefining process, from which the recoveries of base metals (copper, nickel), high-value rare elements (tellurium, selenium) and precious metals (silver, gold) often witnessed problems because of the complexity of constituent phases in the slime. In the present study, a sulfuric acid leaching process in the presence of manganese(IV) oxide (MnO2) as oxidant and graphite as catalyst has been developed to augment metal recoveries from CAS. The leaching efficiencies of copper, nickel, tellurium, selenium and silver from CAS, and manganese from MnO2 achieved were 99.9%, 98.2%, 90.8%, 81.9%, 80.7%, and 84.1%, respectively, after leaching under the conditions: 2.0 M H2SO4 concentration, 90 degrees C temperature, 0.8/0.8/1 MnO2/graphite/CAS mass ratio and 6 h reaction time. These leaching efficiencies are higher than that in the absence of only graphite (99.8% Cu, 97.7% Ni, 76.8% Te, 69.4% Se, 67.2% Ag and 55.9% Mn), showing that graphite plays an important role to augment the leaching reactions. Negligible amount of Se and Ag leaching was noted without MnO2. The recyclability test of graphite showed that it can be recycled without loss of its catalytic performance. Thus, the process presented in this study shows good potential of sustainable metal recovery from CAS.

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