High Purity Ammonium Paratungstate Ion Exchange Method (2)

(4)The tertiary filter press obtained crude sodium tungstate solution 31 plus an appropriate amount of water 311 diluted to obtain a suitable ion-exchange process dilute crude sodium tungstate solution, when from the top down into the ion exchange column in dilute crude sodium tungstate solution, resin and sodium tungstate solution column in tungsten adsorption.

(5) When the sodium tungstate solution continuously flows into the exchange column, the ion-exchange saturated adsorption is started. Since WO₄^2- has high affinity with the resin, with the increase of WO₄^2-, other impurity anions originally adsorbed on the resin, which will be replaced by WO₄^2- exchange column exchange, the process using selective string ion exchange adsorption process, that is, when the post-liquid containing WO₃ ≤ 0.2g / L directly discharged to waste water treatment.

(6) The tungstate solution containing tungsten obtained above is sent to the cleaning tank, using "selective precipitation" molybdenum removal technology, the solution pH is adjusted to 7-10, adding a certain amount of ammonium sulfide, copper sulfate addition Impurity reagent, the ammonium tungstate solution obtained by ion exchange process desorption is further removed to remove impurities such as molybdenum, arsenic, tin and antimony in ammonium tungstate solution.

(7)The ammonium tungstate solution after impurity removal is added into the crystallization pot and evaporated and crystallized by adding the ammonium tungstate solution through natural precipitation, filter cloth filtration and deep filtration. When the density of the crystallization end to ammonium tungstate solution is 1.04 ~ 1.10g/mL, the natural cooling is 0.5 to 1 hours. Open the bottom valve for discharge, and separate the crystal from the mother liquid in time by the disc vacuum filter, it was washed 1 times with the diluted ammonia water detergent which had been made of 1%-3%, and then washed for 3 times with deionized water. After filtration and washing, the wet high-purity ammonium parotungstate was obtained, and then dried and sieved to obtain the finished product of high purity ammonium parotungstate.

Through the above procedure, a total amount of impurities can be within 70 ppm of high purity ammonium paratungstate.

Read more: High Purity Ammonium Paratungstate Ion Exchange Method (1)

http://news.chinatungsten.com/en/tungsten-information/103457-ti-13082

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