Tungsten and Molybdenum Separation – Molybdenum Trisulfide Precipitation Method

Tungsten and molybdenum are similar elements, they both belong to VIB clan of element periodic table, have similar property. Tungsten and molybdenum separation has always been a difficult issue in tungsten ore metallurgy, and a key process during beneficiation. 

There are several methods include extraction method, precipitation method and ion exchange method to realize the separation. Here we introduce molybdenum trisulfide precipitation method.

Molybdenum trisulfide precipitation method uses the affinity of molybdenum in solution which is bigger than tungsten, the principle is disparity of affinity toward sulfide between tungsten and molybdenum. Sulfurizing sodium tungstate solution for a certain time to transform molybdenum into sulfidizing agent, by precipitation or exchange to separate tungsten and molybdenum. Sulfurization is the key step. No matter which method is taken, sulfurization directly affects molybdenum removing affect.

Molybdenum trisulfide precipitation method is divided into sulfurization process and add acid to adjust pH value. Adjust pH value of sodium tungstate solution to 7.0~7.5, heat to 70~80℃ and ad Na2S or NaHS. Stirring, keep it warm for 2.0~2.5h, adding amount of sulfurazation agent needs to guarantee S^2- concentration ten times higher than molybdenum, then adjust diluting sulfur acid or diluting hydrochloric acid pH value to 2.5~3.0, boil for 1.5~2 hours, molybdenum will be precipitated as molybdenum trisulfide.

Molybdenum trisulfide precipitation method was used to be main method for eliminating molybdenum in tungsten metallurgy. However, it will waste a lot of tungsten, can not deeply remove molybdenum. Moreover, it consumes too much acid, during acid neutralizing process will discharge toxic gas and waste water to cause environmental pollution. So this method is eliminated gradually.

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