Comprehensive processing of low grade sulphidic molybdenum ores

Low-grade sulphidic molybdenum ores were treated by using a combined processing route for a comprehensive recovery of molybdenum, copper, and other minor elements. As the first step, oxidation roasting was used to convert most of sulphides into metal oxides, during which 85–90% of sulphur was removed. Then both water and dilute sulphuric acid leaching of the roast were tested, in order to remove silica, iron and other impurities from the roast. Both copper and molybdenum were recovered one after another from the filtrates via cementation by iron powder under controlled temperature and pH conditions. Recovery for both elements was in all cases over 99%. Reasonable separation efficiency for copper and molybdenum was achieved from the water leach solutions. The leached cakes were dissolved in ammonia to recover the molybdenum by crystallisation as ammonium-dimolybdate. The proposed roasting, leaching and separation steps give a feasible alternative for a comprehensive processing of low grade molybdenum ores.