New insight into poor flotation recovery of fine molybdenite: An overlooked phase transition from 2H to 1T MoS2

[Display omitted] •Phase transition of MoS2 is responsible for recovery drop of fine molybdenite.•Fine molybdenite is more likely to produce 1T MoS2 during milling process.•1T MoS2 exposed more high-index crystal planes and presented a poor flotability. Fine molybdenite is the stubborn part for molybdenite recovery during flotation process, which causes serious resource waste and financial loss. Our recent discovery of MoS2 transition during milling process, from stable 2H to active 1T phase, results in serious recovery drop of fine molybdenite. Moreover, with the decrease of molybdenite size (from 74 to 38 μm), {001} facet spacing of molybdenite widens and 1T MoS2 percentage increases. Flotation experiments present a high linear correlation between molybdenite recovery loss and 1T phase percentage, implying phase transformation is an important reason for the low recovery of fine molybdenite. 1T phase could provide more active adsorption sites than 2H based on electrostatic potential (ESP) results, density of functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations suggest 1T phase presents strong wettability on its basal plane. Combining with the Wulff shape of molybdenite, 1T MoS2 exposed more high index crystal planes than 2H phase and showed a poor flotability in oil–water mixed system. These findings provide a new insight into phase change of fine molybdenite and helps in understanding its flotation behavior in pulp.