Investigations on the extraction of molybdenum and rhenium values from low grade molybdenite concentrate

Extraction of molybdenum and rhenium values from low grade Indian molybdenite concentrate was investigated by roasting the concentrate in the presence of slaked lime and soda ash, followed by hydrometallurgical treatment of the roasted products. In the lime roasting process, molybdenum recoveries of around 99% were achieved when a charge containing a slaked lime to concentrate ratio of 0.875 was roasted at 550 degrees C for 1 h and the calcine was leached twice with 1 M H2SO4 at 80-90 degrees C for 2 h. In the soda ash roasting process, over 99% of the molybdenum could be extracted when a charge containing a sodium carbonate to concentrate ratio of 1.05 was roasted at 650 degrees C for 1 h and the roasted mass was leached with water at 80-90 degrees C for 2 h. A carbon adsorption technique, involving selective adsorption of molybdenum on activated charcoal from the leach solution (at a pH of 2.0), followed by desorption with ammonia, was adopted to prepare high purity MoO3 product. Rhenium recoveries of the order of 74% were obtained by water leaching of the lime-roasted calcine at 80-90 degrees C for 1 h.