Recovery of molybdenum and rhenium from sulfide concentrate by electro-oxidation and precipitation

Abstract

With the purpose of extracting molybdenum and rhenium from molybdenum sulfide concentrate, electrolysis of slurry, solvent extraction and precipitation operations were carried out. The slurry of the concentrate in 10 mass% NaCl aqueous solution was continuously circulated into a vertical type 10 stack bipolar electrolytic cell consisted of carbon electrode disks, and the concentrate was dissolved by electrochemically generated oxidizers at 313 K. The current efficiency for molybdenum dissolution was 73 % after 10 hours electrolysis, and the leach solution was found to contain 0.2 mol/l of molybdenum and 4×10-5 mol/l rhenium. This result shows the dissolution is more than 8 times faster than that obtained using a single cell. The leach solution from electro-oxidation was then subjected to a solvent extraction for rhenium, which is then recovered as sulfides. After rhenium separation, molybdenum was precipitated by pH adjustment, and solid MoO3·(H2O)x crystals, free of sulfate, were obtained from the leach solution containing large amount of SO42-.