APT Crystallization Liquor Treatment -- Ion Exchange Method
The crystalization method of evaporation and extraction method in the preparation of APT will produce crystallization liquor, leaving about 5% -10% of the WO3 and part of the S, P, As, Mo, K, Na and other impurities.
Resulting in it can not directly return to the process of use , in order to improve the metal recycle, it is necessary to set up auxiliary processes to recycle WO3 in the liquor.
To contain large amounts of NH4Cl crystallization liquor of ammonium paratungstate, ion exchange method can be used to recycle tungsten concentrate and transformed into Na2WO4 and return to the main process.
Ammonium paratungstate crystallization liquor treatment of ion exchange need to adjust the pH value of hydrochloric acid to 3-4, through the weak alkaline anion exchange resin layer, where the tungsten, molybdenum and impurity phosphorus, arsenic, silicon with the same polyacid or heteropoly acid acid anion adsorption, the presence of chloride ions does not affect the adsorption effect, and the supported resin is desorbed by NaOH solution to obtain a concentrated sodium tungstate solution.
Ion exchange method began to be applied to the production of ammonium paratungstate (APT) in the 1980s. The method has the advantages of short process flow, simple equipment, low investment, good environment and high yield, in China has been widely used, many manufacturers have turned to the liquor treated ion exchange techniques, ion exchange method and treatment of crystallization liquor mainly used macroporous weakly basic anion exchange resin, in the acidic conditions, the operation has the characteristics of large exchange capacity, easy to adsorption and desorption, and obtained the sodium tungstate.
The solution can be returned to the ion exchange main process. The method has made great progress compared with the artificial scheelite method, but there are still some shortcomings of acid and alkali consumption and excessive ammonia nitrogen.
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