Recovery of Mother Liquor for Preparing Ammonium Paratungstate by Ion Exchange Method

Most of ammonium paratungstate (APT), about 80% is produced by ion exchange from the raw material of tungsten ore in tungsten metallurgy in China. There are three main steps in ion exchange: decompose tungsten ore, ion exchange, evaporate and crystallize. Today we provide a method that not only can remove Mo, Sb, As, Sn at one-time, but also recycle NH₄Cl, improve the recovery rate of WO₃, and eliminate waste water.

0-95% of the mother liquor is returned for preparing desorption agent, the remaining returned to prepare pre-ion-exchange solution, and take the following two ways according to the contents of impurities in the crystallization mother liquor:
1. If the mass ratio of WO₃/Mo in ammonium tungstate produced by ion exchange is below 5000, adding (NH4)₂S for vulcanization. Conditions for the vulcanization are: vulcanize at 10-75℃, use amount of 0.5-3g/l more than theoretical, then add copper sulfate or chloride or Cu(Ac)₂ at temperature of 10-80℃, the amount of Cu₂⁺ is 3-6 times of the theoretical. Filter after kept 1-3 hours, and the filtrate is evaporated and crystallized to prepare APT, crystallization mother liquor returned back directly.

2. if the mass ratio of WO₃/Mo is upper than 5000, evaporate and crystallize to generate  APT directly. Add (NH4)₂S into the crystallization mother liquor in advance for vulcanization. Conditions for the vulcanization are: vulcanize at 10-75℃, use amount of 1-3g/l more than the theoretical, then add copper sulfate or chloride or Cu(Ac)₂ at temperature of 10-80℃, the amount ofCu₂⁺ is 3-6 times of the theoretical and filter after heat preservation for 1-3 hours, filtrate return to reuse.

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