Effect of mechanical activation on the hypochlorite leaching of Sarcheshmeh molybdenite concentrate

Hydrometallurgical extraction of molybdenum from sulfidic molybdenite concentrates is an important issue from technical, economic, and environmental viewpoints. The influence of mechanical activation on the hypochlorite leaching of a molybdenite concentrate (Kerman, Iran) were studied in a stirred reactor at batch mode. The effects of several critical parameters, including pH, temperature, reaction time, NaClO concentration, and liquid to solid (L/S) ratio on the rate and extent of molybdenum extraction from the concentrate were investigated. Maximum molybdenum extractions, 98% and 95%, obtained for the mechanically activated and nonactivated concentrates, respectively after 60 min at 50°C, stirring speed of 500 rpm, L/S of 333 mL/g, pH of 9, and using 40% NaClO solution. Specific surface area and particles size measurements in conjunction with FE-SEM images showed that improvement in the extraction after mechanical activation could be due to increasing the surface area and changing the crystal structure of the concentrate. Mechanical activation had a significant effect on molybdenum extraction after 2 min, (13% difference in extraction); however, after 60 min, molybdenum extractions from mechanically activated and nonactivated samples were 97% and 92%, respectively. It was found that mechanical activation has a significant effect on the leaching of molybdenite in short reaction times.