Calcium Tungstate Molybdenum Removal Optimization Process

Tungsten and molybdenum are similar elements, and their physical and chemical properties are very similar. Tungsten minerals are all associated with molybdenum, but the content is different. With the depletion of high-grade tungsten resources, low-grade tungsten resources and secondary tungsten resources have become more and more important tungsten metallurgical raw materials. The molybdenum ion concentration in calcium tungstate solution produced from these raw materials is also increasing. In order to produce pure tungsten compounds, it is necessary to remove molybdenum completely and efficiently from calcium tungstate solution.

(1)Sulfurization: The method of sulfurization in tungsten smelting has been mature, that is, adding a certain amount of S₂ - such as Na₂S or (NH₄)₂S into the solution of calcium tungstate, and controlling the pH, temperature, time and other parameters to form the corresponding thioate molybdenum compounds.

(2)Precipitation: A certain amount of precipitant is dissolved in pure water and added to the sulfurized calcium tungstate solution. The temperature is 20 ~70 ~℃ and the stirring time is 0.5~2.5 hours. The purpose is to form organic compound precipitation between the thioate of molybdenum and the precipitant.

(3)Filtration: The purpose is to separate the organic precipitates containing impurities from the calcium tungstate solution. The filtrate is the calcium tungstate solution after removing impurities, and the filtrate residue is the organic precipitate. When adsorbing, organic matter can also be adsorbed and then filtered and separated. The adsorbate used is activated carbon and its products, and one or more of them can be used as an adsorbate at the same time.

(4)Reduction: Increase the acidity of calcium tungstate solution to 140-160 g/L, and add tungsten powder to the solution. The amount of tungsten powder added is 1-3% of calcium tungstate content in mass fraction. Tungsten and molybdenum are in the state of positive hexavalence in solution. If proper reductant is selected, molybdenum is easy to be reduced to low price. Major molybdenum can be separated from tungsten by utilizing the difference between the properties of low-valent molybdenum compounds and those of high-valent tungsten compounds. Metal tungsten powder can be used as a reducing agent, and this purification operation can be exempted. Tungsten powder can reduce high-valent molybdenum, tungsten is low-valent, and the reduction potential of molybdenum is larger than tungsten, so tungsten powder can preferentially reduce molybdenum, and some tungsten is reduced to low-valent. When tungsten is reduced to molybdenum blue Mo₃O₈, molybdenum blue is dissolved in acid to form thiosulfate.

The molybdenum content in calcium tungstate is 2%-3.5%. The existing smelting impurity removal process is improved. The molybdenum content in calcium tungstate is less than 0.5%. The effect of impurity removal is good, the equipment is simple, the production cost is low, the process is short, and the operation is easy.

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