New Insights into the Role of Thiol Collectors in Malachite Flotation

Malachite is one of the most important copper-bearing oxide minerals; however, it shows poor floatability prior to sulfidization under the thiol collector system. This study investigated the reasons for the low recovery of malachite flotation without sulfidization. The results of adsorption capacity and contact angle test indicated that the malachite surface could adsorb a sufficient amount of the collector, obviously increasing the hydrophobicity of the malachite surface under static conditions. By measuring the amount of inorganic carbon in the flotation solution, it was found that the amount of inorganic carbon in the solution increased significantly when the thiol collectors were added into pulp, which could be attributed to the induced dissolution of the malachite surface by thiol collectors. Solubility tests further demonstrated that the copper ions released from the natural dissolution of malachite proved difficult in regard to reactions with thiol collector to form precipitates; however, the thiol collector induced the dissolution of malachite surface, and so the hydrophobic complexes’ copper-collector could not firmly adsorb on the mineral surface. Fourier transform infrared (FTIR) analysis revealed that thiol collectors do not adsorb stably on malachite surfaces. This was considered to be a substantial reason for the poor performance of malachite flotation without sulfidization.