Modulating Surfaces Hydrophobicity of Molybdenite and Galena through Sulfuric Acid Pretreatment for Efficient Flotation Separation

Molybdenite and galena are often associated in polymetallic sulfide deposits in complex forms, and the separation of the two minerals has become a difficult and hot spot. In this article, a new method combining sulfuric acid pretreatment with flotation is proposed to realize the selective separation of molybdenite and galena. Microflotation tests were used to investigate the effect of sulfuric acid pretreatment on the floatability of molybdenite and galena. Contact angle measurement and XPS and SEM-EDS analyses revealed the mechanism of sulfuric acid pretreatment on the surface properties of molybdenite and galena. The microflotation test of single minerals results showed that sulfuric acid concentration, pretreatment temperature, and time had important effects on the surface properties of molybdenite and galena. Under the optimal conditions of sulfuric acid concentration of 3 mol/L, pretreatment temperature of 100 °C, and time of 30 min, the floatability of molybdenite was almost unaffected and still good, while galena is inhibited and almost unfloatable, which produces the largest difference in floatability between the two minerals. The test results of pretreatment-flotation separation of the molybdenite-galena mixture showed that the new process achieved efficient flotation separation of molybdenite and galena, which further confirmed the microflotation results of a single mineral. The contact angle, XPS, and SEM-EDS analyses showed that the surface of galena was oxidized to form a rough passivation layer of PbSO₄ after pretreatment, which resulted in the loss of hydrophobicity and floatability, while the surface properties of molybdenite did not change significantly before and after pretreatment. The new method of flotation separation of molybdenite and galena based on surface pretreatment provided a potential application prospect for the difficult separation of lead-molybdenum polymetallic sulfide ores.