High Efficiency Separation of Tungsten and Molybdenum from Special Resin

In the classical process, the removal of molybdenum in ammonium tungstate solution is a method of combining selective precipitation with ion exchange. By sulfurizing the ammonium tungstate solution in advance, Mo and S2- in ammonium tungstate solution are formed into thiomolybdenum root, most of which are precipitated and removed with the added copper salts, and the unprecipitated thiomolybdate root is passed through. The exchange column is further purified by resin adsorption.

There are some defects in the removal process. During the selective precipitation process, while adding copper salt to remove impurities, some tungsten in ammonium tungstate solution will be co precipitated with other impurities and enter the slag, resulting in the loss of valuable tungsten, which is not conducive to the improvement of the recovery rate of tungsten tungsten. In order to overcome the separation efficiency of tungsten and molybdenum, a special resin has been put forward by the researchers. Efficient purification of ammonium tungstate solution containing high Mo is described as follows:

(1) In ammonium tungstate solution, the concentration of WO₃ is 168.40g/L, the concentration of Mo is 7.0g/L, it is vulcanized with ammonium sulphide, the stirring speed is 60r/min, the stirring time is 120min, the reaction temperature is 298K, and the vulcanization end point control S2- is 3.2g/L in the vulcanizing solution.

(2) Sulfuration is completed, static place for 150min, filtration, liquid-solid separation, separation liquid collection and reserve, separation slag collection and recycling.

(3) Simulated exchange adsorption, the analog exchange column is a transparent plexiglass analog exchange column with a specification of Φ5cm x 70cm, the filled resin is a special resin WDA918, the filled resin quality is 467.5g, the resin layer height is 36.5cm.

(4) Exchange adsorption, the separation liquid passes through the resin layer and the flow is controlled to 8mL/min. When the content of Mo is more than 0.01g/L in the separation liquid passing through the resin layer, the exchange is stopped, and then the separation hydraulics in the simulated exchange column is produced with distilled water. The adsorbed Mo metal amount is 22.61g and the saturated adsorption capacity is 4.83% (saturated adsorption capacity = adsorption metal amount/ the quality of the adsorbed resin).

(5) The adsorption saturated special resin WDA918 uses sodium hydroxide solution as a desorption agent for static desorption, the concentration of sodium hydroxide is controlled to 165g/L, the time of desorption is 300min, and the desorption dose is 720mL.

(6) The desorption is completed, the hydrochloric acid solution is used to make the static transformation, the concentration of hydrochloric acid is controlled to 70g/L, the transition time is 300min, the volume of the hydrochloric acid solution of the transformation agent is 720mL, the transformation is completed, the washing and the next adsorption period are entered.

(7) The solution of ammonium tungstate after evaporation crystallization is evaporated and crystallized in water bath. The temperature is controlled to 373K, the stirring speed is 50r/min, and the crystallization end is controlled by the WO₃ concentration of 12g/L in the crystallization mother liquor.

(8) The crystallization is completed, the filtration, the distilled water washing, the liquid solid separation, the separation liquid collection and recycling, the separation solid is dried in the vacuum drying box, the temperature is controlled to 378K, the drying time is 120min.

(9) According to the above 3 experiments, the metal content of Mo with special resin WDA918 was 21.36g, 23.31g and 23.50g respectively. The adsorption saturation capacity was 4.57%, 4.99%, 50.27% respectively, and the crystallization of APT reached the requirement of 0 grade APT.

This method has overcome the disadvantages of low efficiency, complex process and high cost for the production of 0 stage APT. It can efficiently purify ammonium tungstate solution containing high Mo, reduce the process of removing impurity of copper salt, simplify the process and reduce the production cost. 

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