Acid treatment for purification and enrichment of low grade molybdenite concentrates

Molybdenite concentrates produced by Uranium Corporation of India Ltd., contains copper and nickel as impurities in amounts which are much above the specifications for the concentrates to be utilised for the production of standard grade ferro-molybdenum, molybdic acid, calcium molybdate and molybdenum metal. Systematic studies were undertaken to remove impurities like copper and nickel from the concentrates and enrich the product. The process involves two steps comprising of desilication by curing with hydrofluoric acid solution and subsequent curing with nitric acid in presence of chloride salts at ambient temperature whereby over 91% SiO2, 97% Cu and 75% Ni have been removed with less than one percent less of molybdenum in solution. Nickel and copper from the leach liquor can be recovered by conventional processes.