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络合均相法可在室温和低酸度下生产 H_2WO_4。在 pH=9.4的正常情况下除硅,H_2WO_4的沉淀率可大于98%。如按传统工艺在 pH=8～9除硅,沉淀率仅85%左右。经研究发现,在 pH=8～9时,溶液中部分 Na_2WO_4形成仲钨酸 A,仲钨酸 A 在加热和 H_2SiO_3的催化作用下转变成不能用络合均相法沉淀 H_2WO_4的仲钨酸 B,从而使 H_2WO_4沉淀率明显下降。因此,选择较高的pH 除硅是获得高的 H_2WO_4沉淀率的一个重要条件。
The complex-homogeneous method can produce H_2WO_4 at room temperature and low acidity. In the normal case of pH = 9.4, the precipitation rate of H 2 WO 4 can be more than 98%. If the traditional process at pH = 8 ~ 9 in addition to silicon, precipitation rate of only about 85%. It was found that when pH = 8 ~ 9, part of Na_2WO_4 in the solution formed Paratungstate A, and Paratungstate A changed into Paratungstate B which could not be precipitated by the complexation homogeneous method under the catalysis of heating and H_2SiO_3 , So that H 2 WO 4 precipitation rate decreased significantly. Therefore, selecting a higher pH for silicon removal is an important condition for obtaining high H 2 WO 4 precipitation.