High Purity Tungstate Preparation from Direct Extraction Method

For many years, researchers have been innovating and improving the preparation methods of ammonium tungstate solution. Some scholars have invented a method of producing high purity tungstate from the decomposition of tungsten ore.

The process of extracting tungstate solution by P, As and Si with direct extraction of tungsten is characterized by the use of CO2-3 type quaternary ammonium salt as extractant and a certain polar Ameliorant and diluent to form organic phase. The concentration of the extractant is 200 to 400g/l, and the organic phase is directly exposed to the sodium leaching solution of tungsten ore to carry out multistage countercurrent extraction. In this process, the tungsten is extracted into the organic phase and the impurities P, As and Si are separated from the extractive solution. The loaded organic phase is extracted from the NH₄HCO₃ or NaHCO₃ water solution of 1 to 3mol/l, and the pure ammonium tungstate or sodium tungstate solution is obtained. After the stripping, the organic phase is regenerated with the solution of NaOH in the aqueous solution and the residual liquid produced in the process. The organic phase regeneration solution is returned to leaching through proper treatment.

The extraction process of ammonium tungstate solution from P, As, Si and Mo is characterized by:

Three ways to adjust the pH of the crude Na₂WO₄ solution, then measure the solid sulphide base into the coarse Na2WO4 solution which is given pH, control the concentration of free sulfur ions in the solution of 1 to 10g/l, maintain 48 ~ 0.5hr at the temperature of 60~90°C to room temperature, or the crude Na₂WO₄ solution by membrane electrolysis, and enter the H₂S gas at room temperature. The temperature of 60~90°C is maintained at 48 ~ 0.5hr. In this process, Mo and As are fully converted to thioate, and the WO3 concentration of Na₂WO₄ solution treated by deionized water is adjusted and the solution of pH 8~9 to WO₃ 50 ~ 300g/l with 1 ~ 4mol/l NaOH liquid is adjusted.

CO2-3 type quaternary ammonium salt is used as extractant and mixed with the organic phase of a certain polar ameliorant and diluent to be mixed with the above extraction liquid to carry out multistage countercurrent extraction. In the process, Mo, W and As were extracted into organic phase, and impurities P and Si were separated from the raffinate. Then W and Mo and As were carried out by stepwise reverse extraction. The high purity (NH₄) ₂WO₄ or Na₂WO₄ solution was first extracted with NH₄HCO₃ or NaHCO₃ solution multistage counter current, then the organic phase was oxidized by oxidizing agent, then Mo and As were extracted with bicarbonate solution, or the oxidation and stripping were carried out simultaneously. Finally, the reverse organic phase was regenerated by the NaOH aqueous solution, and the residual liquid produced during the process was produced. The regeneration solution of organic phase can be used for leaching by proper treatment.

The method of direct extraction and separation of impurities from high purity tungstate has a wide source of raw materials, short process, reduced the cost of the product, and it is easy to achieve in industrial production. 

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