Molybdenum recovery from molybdenite concentrates by low-temperature roasting with sodium chloride

Abstract

The roasting of molybdenum concentrates using NaCl has been carried out. During the roasting process, Mo is present both as a gas (25–40%) and as solid residue (60–75%). Molybdenum chloride and oxychloride condensate both dissolve in the alkaline solution with molybdenum recovery up to 100%. The results of the study show that 30–32% of molybdenum (sodium molybdate) in the roasted residue is water-soluble. This paper proposes a methodology for leaching roasted residue in two stages: first by water, then by alkaline solutions. Using this methodology, molybdenum recovery from the roasted residue exceeds 99%. It was determined that up to 40% of the sulfur contained in the concentrate remains in the roasted residue after the roasting process in the form of sodium sulfate, which enables a significant reduction of SO2 generation. The results were achieved under optimal roasting conditions: a roasting temperature of 420–430°С, NaCl ratio of 100% (from concentrate weight), and 90min roasting time.