Effects of solution pH and polyethylene oxide concentrations on molybdenite–molybdenite, molybdenite–kaolinite, and molybdenite–quartz interaction forces: AFM colloidal probe study

Abstract Molybdenite (MoS2), a major resource for Mo, is often associated with some gangue minerals, such as kaolinite and quartz. The flotation separation of fine-grained molybdenite from gangue minerals is always difficult due to the low efficiency of capturing fine particle by bubbles and the heterogeneous agglomeration with gangue particles. In this study, a fundamental investigation was carried out on molybdenite–molybdenite, molybdenite–kaolinite, and molybdenite–quartz interaction forces with varying solution pH and polyethylene oxide (PEO) concentrations using the atomic force microscopy (AFM) colloidal probe technique. And the results of force measurements were interpreted in comparison with the zeta potential distributions, adsorption kinetics experiments and quantum–mechanical calculations. pH 6 solution was optimal for the selective aggregation of molybdenite particles when a stronger adhesion force between molybdenite and molybdenite can be obtained, while a weaker adhesion force existed in the kaolinite–molybdenite and quartz–molybdenite systems. And adding 1–2 ppm of PEO to the solution was the best to improve the flocculation of molybdenite particles and inhibit the adhesion of kaolinite and quartz particles to molybdenite particles in pH 6 solution. Adsorption kinetics experiments and adsorption energy calculations showed the highest adsorption performance of PEO on molybdenite surface, which was attributed to the interaction of sulfur and hydrogen.