2021年5月19日星期三

New Production Process of Tungstic Acid

Tungstic acid is made of artificial white tungsten (CaWO4) and concentrated acid under heating and cooking conditions. Artificial white tungsten is prepared by removing molybdenum (Mo) from industrial sodium tungstate solution by sodium sulfide method and adding calcium chloride. If the process is not treated by the sodium sulfide method, there will be no molybdenum removal effect, and the sodium sulfide method for removing molybdenum is more troublesome. Because the process needs to be produced under high temperature and high acidity conditions, it has high energy consumption and high acid consumption. The corrosiveness is strong, and the yield is not high. Therefore, the following will introduce a new production process of tungstic acid. The specific steps are as follows:

Add hydrogen peroxide (H2O2) complexing agent to industrial sodium tungstate (concentration between 0.2N and 1N). The amount of complexing agent is the molar ratio of tungsten: hydrogen peroxide of 2:1 to 2:2, add hydrochloric acid in the room temperature range of 10℃ to 28℃ to make the solution acidity between 0.5N and 2N (if the content of chromium and molybdenum impurities in sodium tungstate is high, the acidity of the solution should be adjusted to 2N), and then pass sulfur dioxide or add sulfite or bisulfite to directly prepare tungstic acid. The prepared tungstic acid is washed sequentially with 1N HCl, 0.5N HCl and absolute ethanol to obtain a pure product. Note: The amount of sulfur dioxide or sulfite or bisulfite is that the molar ratio of sulfur dioxide or sulfite or bisulfite: hydrogen peroxide is between 1:0.7 and 1:1.3.

Compared with the existing production method, the advantages of this technology are that in addition to the classic sodium sulfide removal of molybdenum process and the process of preparing artificial white tungsten with calcium chloride; since concentrated acid is no longer needed, it consumes less acid and consumes less energy and wastes; the production efficiency can be 98%, which is 10% higher than the existing process, and the molybdenum removal effect can reach 70% to 80%.

In general, the new technology has the advantages of simple operation, high yield, weak corrosiveness, less three wastes, high purity and high activity.

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