Separation of Molybdenum and Copper Based on Cu-Mo-NH3-H2O System

Copper was an impurity element which was strictly restricted in ammonium molybdate products. Copper was often contained in molybdenum calcine. Copper and molybdenum were leached simultaneously in ammonia leaching process. Sulfide precipitation was often used to remove copper from leaching solution, resulting in increased production costs and environmental pollution. Therefore, the separation of copper and molybdenum was a key problem in the preparation of ammonium molybdate. According to the thermodynamic analysis of the alkaline leaching process containing copper and molybdenum roasting, the lgc-pH diagram of Cu-Mo-NH3-H2O system at 25℃ was drawn. The thermodynamic equilibrium diagram was used to analyze the thermodynamic analysis of the alkali decomposition of copper containing molybdenum calcic sand, and the new separation method of copper and molybdenum was deduced. The results showed that: sodium hydroxide decomposed copper molybdate, molybdenum dissolved and the copper was almost completely left in the slag to separate copper and molybdenum. At condition of pH 5.5~7.0, the complexing of ammonia and copper to form copper ammonia complex to decompose copper molybdate. Reducing [N]T, pH value and increasing [Mo]T to expand CuMoO4 stable region, but not conducive to the formation of Cu(NH3)m 2+, which was beneficial to the separation of copper from ammonium molybdate solution. The test showed that the molybdenum was preferable to the leaching of ammonia compared to copper, and the increase of ammonia was beneficial to the leaching of copper and molybdenum; the pH value of ammonium molybdate solution was 5.8, and the concentration of copper in solution was reduced to 0.098 g•L-1, the precipitation rate of copper reached 98.8%, and the effect of removing copper from ammonium molybdate solution was achieved. The experimental results agreed with the theoretical conclusions. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.