A fundamental study of leaching kinetics and mechanisms of molybdenite assisted by mechanical activation

The mechanical activation was applied as a pre-treatment method to improve molybdenite (MoS 2 ) leaching . The effects of grinding ball size, ball to powder mass ratio, milling speed and time, molar ratio of mineral to oxidants, as well as the influence of solution pH, temperature and leaching time were investigated in detail. The results showed an extremely low Mo extraction (less than 2% at acidic and neutral conditions) for MoS 2 activated alone. However, Mo extraction was increased significantly after co-grinding of MoS 2 with NaClO 2 and Na 2 CO 3 , e.g ., more than 58% in any leaching solution applied. Prolonging the grinding time improved Mo extraction but the efficiency was declined gradually, giving rise to an optimum grinding efficiency at 4 h with a molar ratio of 1:3:5 for MoS 2 :NaClO 2 :Na 2 CO 3 . Distilled water was selected as the leaching solution since this gave similar Mo recovery to other lixiviants. Higher temperature and longer leaching time were beneficial to Mo extraction. However, it was also found that too large grinding balls and high ball to powder mass ratio adversely affected MoS 2 extraction. The kinetics analysis indicated that the leaching of activated MoS 2 followed a chemical reaction controlled mechanism. The XRD and SEM analyses indicated that mechanical activation not only reduced the particle size of MoS 2 but also triggered solid state reaction to produce soluble Na 2 MoO 4 , thereby improving Mo extraction significantly.