A new technology was proposed to produce ammonium paratungstate (APT) from ammonium metatungstate (AMT) solution by adding (NH 4 ) 2 CO 3 or NH 4 HCO 3 in order to reduce energy consumption and subsequent ammonia recovery burden in crystallization step. Specifically, the effects of ammonium source dosage, temperature, reaction time and stirring speed on crystallization yield, crystalline phase and morphology of APT products were systematically investigated. The results showed that crystallization yields under optional conditions with (NH 4 ) 2 CO 3 and NH 4 HCO 3 as ammonium sources could reach 85.4% and 86.9% with particle size ( D 50 ) of 358.8 μm and 441.3 μm, respectively. The crystallization mechanism could be identified as first transforming to and finally to , resulting in the APT precipitation by combining with (NH 4 ) 6 H 6 W 12 O 42 ·10H 2 O played as an intermediate in the crystallization, which could also react with ammonium sources to form APT crystals. Compared to NH 3 ·H 2 O as an ammonium resource, the corresponding maximum crystallization yields under the same optimal conditions were in order of NH 4 HCO 3 >(NH 4 ) 2 CO 3 >NH 3 ·H 2 O, while different ammonium sources affect the morphology of crystallization product.
ZHANG et al. (Wed,) studied this question.