Application of Acetylcysteine for Selective Separation of Chalcopyrite and Molybdenite: Flotation Performance and Depression Mechanism

Given the comparable natural floatability of molybdenite and chalcopyrite, together with the environmental concerns associated with conventional inorganic depressants, achieving their flotation separation remains a major challenge. Herein, acetylcysteine (NAC), a low-toxicity organic reagent, was investigated as a selective depressant for the flotation separation of molybdenite and chalcopyrite. Flotation results showed that, at pH 8.0 and 40.0 mg/L NAC, efficient separation of molybdenite from chalcopyrite was achieved, with a molybdenite recovery of 97.69%, a chalcopyrite recovery of 10.02%, and a selectivity index of 19.50. Furthermore, NAC remained highly effective in depressing chalcopyrite flotation under xanthate-containing conditions. To elucidate the interfacial origin of NAC selectivity, zeta-potential, wettability, adsorption capacity, FTIR, XPS, and DFT analyses were integrated to reveal the adsorption behavior and interaction mechanism of NAC on chalcopyrite and molybdenite. The results suggest that the -SH and -C═O groups of NAC participate in interfacial interactions with surface Cu sites on chalcopyrite, thereby contributing to its preferential adsorption, whereas only weak interaction is observed on molybdenite. This preferential adsorption markedly increased the hydrophilicity of chalcopyrite, while molybdenite retained its hydrophobicity. These findings indicate that NAC is a promising organic depressant for the selective flotation separation of molybdenite from chalcopyrite.