Metatungstate is one of many types of tungstate, the only compound which the structures have been identified as colorless crystals. It has high solubility in water, and can be derived from metatungstate. Since the metatungstate itself is extremely unstable and easily degradable, therefore, it has a large difficulty in preparation. In the traditional way, sodium tungstate often used to prepare metatungstate crystals, but the complex process, high production costs, low productivity, poor product quality and the environmental pollution and other defects make the way no to be better. Nowadays, harmonious environment, cost savings, simplified procedures are promoted, so its necessary to develop a process which has the simplified process, low cost and environmental pollution, and also conducive to industrial producing metatungstate.
Studies have pointed out that ammonium paratungstate (APT) can be used to prepare metatungstate solution. The steps as following:
1. APT powder heated to 270℃~350℃ for 30-60 minutes to dissociate, thus to generate ammonium metatungstate;
2. Add ammonium metatungstate powder into deionized water to leaching with stirring to get an emulsion;
3. Carry out filtration to remove insoluble, and the filtrate was placed in a water bath of 60~90℃ aging for 4~24 hours;
4. Filtered again, and exchanged by Cation Resin, then we get metatungstate solution.
As we can see from the above, the method APT used as raw material to prepare metatungstate solution has the advantages like: simplify process, easy to control, and low cost; In addition, since the reaction process doesn’t introduce any impurity element, so the purity and quality of metatungstate can be ensured; finally, the production process does not use ether and other volatile organic compounds, with minimal impact on the environment, so it is suitable for industrial mass production.
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