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A study of the electrochemical behavior of galena and the effect of the Ca 2+ and SO 4 2− species on the mineral behavior at different pH, was carried out using carbon paste electrodes. The Ca 2+ and SO 4 2− ions were used to simulate the species that are most concentrated in the recycled water of sulfide mineral flotation processes. By means of electrochemical and SEM analysis, it was possible to identify the chemical species that are generated on the mineral surface by means of redox reactions. In the same way, it was observed that depending on the pH, Ca 2+ and CaOH + species interact with the oxidized species of galena. Furthermore, at acidic pH, sulfate reacts with lead ions to form a passivating layer on the surface of the mineral, while at alkaline pH more than one species is generated on the mineral, which passivate its surface. [ABSTRACT FROM AUTHOR]

This paper presents and discusses measurements performed to study the interaction mechanism of calcium and sulfate with galena and their effect on xanthate adsorption. The results of collector adsorption show that regardless of the solution pH (5.5, 7.5 and 9.5), the presence of calcium and sulfate during the mineral pre-conditioning, decreases the adsorption of isopropyl xanthate onto galena. Microflotation measurements carried out at pH 9.5 show that at low concentrations of calcium and sulfate (below about 0.005 mol/L), the recovery of galena is not affected. However, as the concentration of both ions increases, flotation recovery substantially decreases. Contact angle measurements corroborate this behavior: a relatively large contact angle in the absence of calcium and sulfate (i.e., 64°), and a significant decrease when these species are present (i.e., ca. 45°). The observed behavior suggests that calcium ion probably has a certain chemical affinity for the active sites of the galena, which hinders the occurrence of ion exchange collector-sulfate or collector-hydroxyl to form lead xanthate (PbX 2 ), which is the species responsible for the enhanced hydrophobicity of the mineral. On the other hand, the adverse effect of the sulfate is probably due to the formation of a layer of lead sulfate on the galena surface, which acts as a barrier that hinders the interaction of the collector with the metallic sites of the mineral lattice, thus negatively affecting the chemisorption mechanism. Likewise, the decreasing of lead concentration in solution, in equilibrium with the precipitated PbSO 4 and the sulfate, limits the precipitation/coagulation of lead xanthate in the vicinity of the interface. Electrochemical measurements corroborate the proposed mechanism. [ABSTRACT FROM AUTHOR]