LAUSR

Abstract The slow leaching rate of molybdenite (MoS2), due to its inert nature, and low recovery hinders the application of traditional hydrometallurgical processing. This study investigated the effects of grinding speed and time, molar ratio of sodium chlorate (NaClO3, oxidant) to MoS2, leaching time and temperature on the leaching efficiency of molybdenum (Mo). Grinding at low speeds via mechanical activation decreased particle size. However, at speeds over 450 rpm for 1.0 h, or at lower speeds but with longer time, it triggers a solid-state reaction (mechanochemistry) producing soluble Na2Mo2O7. This may be due to the existence of an energy threshold for the solid-state reaction. The most suitable activating conditions were 600 rpm for 0.5 h, with a molar ratio of NaClO3: MoS2 = 5, leached in 0.1 M NaOH solution for 2.0 h at 348 K, giving rise to a Mo recovery of 74.8%. The initial acid leaching stage of the ground mixture is dominated by the dissolution of Na2Mo2O7, giving rise to elevated Mo recovery. The later stage is controlled by the dissolution of MoS2, slowing down the increase in Mo extraction. As compared to alkaline conditions, acidic leaching of MoS2 ground at low speeds (non solid-state reaction) gives greater Mo recovery, due to the greater activity of NaClO3 to MoS2 under acidic conditions. However, the greatest Mo recovery is achieved in alkaline solution for MoS2 ground at high speed (solid-state reaction) due to the occurrence of mechanochemical reaction.