Floatability and Calculated Reactivity of Gold and Sulfide Minerals

Abstract

This paper presents the results of theoretical calculations of the reactivity of gold, molybdenite, stibnite, galena, chalcopyrite, arsenopyrite, and pyrite in comparison with experimental data on the floatability of monomineral fractions with butyl xanthate, measured contact angles, and variation in the kinetics of the potential of mineral electrodes. The calculation method establishes the following series of the reactivity and oxidation ability: Au < Sb₂S₃ < MoS₂ < PbS < CuFeS₂ < FeAsS < FeS₂. During flotation in the Hallimond tube, natural gold grains demonstrate the highest recovery (70%) in the range of pH 5–7 as compared to all the sulfides; molybdenite and stibnite are recovered under the same conditions at the level of 50%. With an increase in pH in an alkaline environment to pH 12, the floatability of all the sulfides decreases with the exception of chalcopyrite. It is found that the duration of conditioning with the collector required for the highest recovery is inverse to the reactivity value. The measured contact angle of a drop of water on an untreated surface is the highest for a gold plate (78°) and the lowest for pyrite (67°), but the greatest increase in the contact angle (by 15°) for pyrite is noted after treatment with butyl xanthate at a concentration of 10^–4 mol/L and pH 6; for molybdenite, treatment with butyl xanthate has almost no effect on the measured value of the contact angle. According to the value of the electrode potential in the region of pH 2.0–5.6, the following series is determined: Sb₂S₃ < PbS < CuFeS₂ < FeAsS < FeS₂. Theoretical calculations and experimental data of the study of monofractions of sulfides and gold establish that the conditions of the experiment (pH, duration of conditioning, concentration of the collector) significantly affect the floatability. The calculated data on the reactivity of chemical sulfide compounds and gold in comparison with experimental results show the importance of maintaining certain flotation conditions to create contrast in the floatability of minerals.