Separation of tungsten and molybdenum has been a big problem of molybdenum and tungsten metallurgy industry. On one hand, China's tungsten resources and high quality tungsten concentrate are fewer and fewer. Tungsten raw materials and tungsten concentrate usually contain molybdenum at different degrees. With growing development of hard alloy, the electron, national defense and other industries, the request for molybdenum content in tungsten products is more and more strict. On the other hand, because of the influence of the lanthanide contraction, tungsten radius is close to molybdenum ionic radius and atomic structure and chemical properties are very similar. Separation process is very difficult. For a long time, people have made a lot of research on separation of tungsten and molybdenum. Methods in industrial application at present basically are molybdenum sulfide precipitation, selective precipitation, ion exchange method, extraction method and so on. In this paper, molybdenum sulfide precipitation separating tungsten and molybdenum from sodium tungstate solution has achieved good effect. 

Molybdenum trisulfide is black solid. It will be heated into molybdenum trioxide above 400℃ in air. It’s slightly soluble in cold water and soluble in hot water. When it’s soluble in aqueous sulfide, the sulfide molybdate will be formed. Molybdenum trisulfide is instable. When heat it in vacuum, it will decompose into molybdenum disulfide and sulfur. Synthesis method of molybdenum trisulfide is adding hydrogen sulfide in the molybdate solution. 

 

The basic principle of molybdenum sulfide precipitation separating tungsten and molybdenum from sodium tungstate solution is as follows: Affinity on sulfur of tungsten and molybdenum exist certain differences. Molybdenum acid radical ion will become thiomolybdate preferentially under certain conditions. In the process of adjusting acid, thiomolybdate salt transforms into molybdenum trisulfide precipitation. While most of tungsten reserves in solution, so as to realize the separation.

 

The experiment method: adjust the solution PH value to 9.0 below and add a certain amount of sodium sulfide. Further adjust the pH of the solution to 8.0 or so and control certain sulfur generation conditions. And then adjust the pH of the solution to around 2.0 ~ 3.0. After boiling, dilute solution double and filter after cooling.