Floatability and calculated reactivity of sulfide minerals and gold

The paper provides the results of theoretical reactivity calculations for gold, molybdenum, stibnite, galena, chalcopyrite, arsenopyrite and pyrite in comparison with such experimental data as the floatability of monomineral fractions with butyl xanthate, wetting angle values, changes in the kinetics of the mineral electrode potential. The following calculation series in terms of reactivity and oxidizing ability were established by calculation: Au < Sb2S3 < MoS2 < PbS < CuFeS2 < FeAsS < FeS2. During the Hallimond tube flotation, natural gold grains demonstrated the highest recovery (70 %) in the рН = 5÷7 range compared to all the studied sulfides. Molybdenite and stibnite are floated at the level of 50 % under the same conditions. As pH increases towards the alkaline region, a decrease in the floatability of all sulfides except for chalcopyrite is observed. It was established that the highest recovery is achieved when the required time of conditioning with the collector is the inverse of their reactivity. The measured wetting angle of a drop of water on an untreated surface has the highest value (78°) for a gold plate, and the lowest one (67°) for pyrite, but the latter features the greatest increase in the wetting angle (by 15°) after treatment with butyl xanthate at a concentration of 10–4 mol/l and pH = 6. For molybdenite, treatment with butyl xanthate has practically no effect on the measured wetting angle. The Sb2S3 < PbS < CuFeS2 < FeAsS < FeS2 series is determined according to the electrode potential in the рН = 2.0÷5.6 range. Theoretical calculations and experimental data obtained when studying monofractions of sulfides and gold showed that experimental conditions (pH, conditioning time, collector concentration) significantly affect the floatability. The calculated reactivity of chemical sulfide compounds and gold in comparison with experimental results proved the importance of maintaining certain flotation conditions to create contrast in the floatability of minerals.