Hydration mechanism of molybdenite affected by surface oxidation: New insights from DFT and MD simulations

The oxidation and hydration of molybdenite surfaces cannot be avoided during the crushing and flotation processes in industry, which adversely affects its clean separation and extraction. In this study, the hydration mechanism under the influence of molybdenite surface oxidation was investigated using density functional theory (DFT) and molecular dynamics (MD) simulations. The results showed that the adsorption energy of a single water molecule on the molybdenite (0 0 1) surface changed from -0.33 kcal/mol to -2.07 kcal/mol after oxidation. Dissociated O acted as a bridging link on the molybdenite (0 0 1) surface, inducing hybridization of the H w 1 s orbitals with the O s 2p orbitals, thereby enhancing the adsorption of water molecules. The adsorption energy of a single water molecule on the molybdenite (1 1 0) surface changed from -33.97 kcal/mol to -3.37 kcal/mol after oxidation. The dissociated O hindered the hybridization of the Mo 4d and O w 2p orbitals, thus preventing the adsorption of water molecules on the (1 1 0) surface. After oxidation, the interfacial interaction between the molybdenite (0 0 1) surface and water molecules was enhanced, while the interfacial interaction between the molybdenite (1 1 0) surface and water molecules was weakened. The water molecules near the surface of molybdenite are adsorbed through hydrogen bonding and gradually form a hydrated film consisting of three layers of water molecules with a thickness of 8-9 & Aring; as the water coverage increases.