China Nonferrous Metallurgy

To optimize the treatment process of secondary ammonia leaching residue from molybdenum smelting and enhance production efficiency, this study investigated the leaching efficiency and economic benefits of three treatment schemes for ammonia leaching residue: atmospheric NaOH+Na2CO3 leaching, oxygen-pressure Na2CO3 leaching, and low-temperature pressurized NaOH+Na2CO3 leaching. The following key conclusions were obtained. The molybdenum species in the ammonia leaching residue primarily consist of 6.73% molybdenum oxide, 0.67% molybdate, and 0.36% molybdenum sulfide. Oxygen-pressure leaching significantly shortens the leaching time and improves molybdenum recovery. Under optimized conditions, the molybdenum leaching efficiencies for the three schemes were 91.70%, 97.22%, and 94.21%, with residual molybdenum contents of 0.89%, 0.265%, and 0.60%, respectively. The oxygen-pressure Na2CO3 leaching scheme demonstrated the best performance. Its optimized parameters include a Na2CO3 concentration of 50g/L, liquid-to-solid ratio (L/S) of 4, temperature of 210℃, oxygen pressure of 0.5MPa, and leaching duration of 1h. Under these conditions, the operating cost for treating 1 ton of ammonia leaching residue is 1441 RMB, with a profit of 37300 RMB, which offsets the higher initial equipment investment compared to the other two schemes. The oxygen-pressure Na2CO3 leaching method offers advantages such as high molybdenum recovery, low reagent consumption, minimal impurity leaching, and significant economic benefits, providing a valuable reference for the treatment of molybdenum-containing ammonia leaching residues.