Interaction mechanism between marmatite and chalcocite in acidic (microbial) environments

Sulphide minerals commonly existing in the form of polymetallic ores are the essential objects in the fields of acid mine drainage and biohydrometallurgy. Although interactions between different minerals have been studied extensively, there are no research reports on the interactions between marmatite and chalcocite. Hence, the interactions between marmatite and chalcocite in biotic/abiotic leaching and electrochemical systems were investigated. Electrochemical tests show that the open circuit potential of marmatite is 39 mV lower than that of chalcocite. Theoretically, marmatite should react as an anode in this galvanic couple, thus dissolving faster. However, leaching results suggest that the introduction of marmatite promotes chalcocite dissolution but its own dissolution was impeded, despite a slight acceleration observed during the early stage in abiotic systems. The results of this study reveal that the solution factors including oxidation-reduction potential, iron concentrations, and microbial concentrations might have significant effects that are more potent than the galvanic effect. The unpredictable inhibition of marmatite dissolution might be attributable to the existence of excess Cu2+ liberated from the chalcocite. A further deduction proposed that a synergistic dissolution of marmatite and chalcocite can be achieved by adjusting their mass ratios to attain a suitable Cu2+ concentration.