Amonium Pratungstate Recovered by Filtration

The ammonium paratungstate is present in the ammoniated aqueous strip solution in an amount of from about 200 to about 300 grams per liter. Further, the ammonium paratungstate is substantially free of the impurities originally present in the brine.

The concentrated, purified ammonium paratungstate can be recovered from the ammoniated aqueous strip solution by any technique known in the art, such as evaporative crystallization, cooling the hot strip solution to allow the ammonium paratungstate to crystallize and the like. The crystallized ammonium paratungstate then can be recovered by filtration.

The filtrate of the filtration can be recycled to the two stage strip circuit of the secondary solvent extraction system where, after pH adjustment, the filtrate is reloaded with ammonium paratungstate at a temperature of from about 45C.to about 55° C. This procedure eliminates the need for additional evaporation stages and thus results in a substantial savings in equipment costs.

The ammonium paratungstate product recovered from the filtration of the strip solution can be dried using any suitable technique known in the art. Further, the ammonium paratungstate will be substantially free of impurities originally present in the brine, namely arsenic, boron, phosphorus, silica and other heavy metals.

The above described process provides an efficient and effective method for recovering concentrated, purified tungsten values (such as ammonium paratungstate) from a brine containing minor amounts of tungsten values (in the form of tungstic oxide) and substantial amounts of impurities without the use of substantial chemical costs, processing costs, or equipment modifications to obtain the desired result.

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