Method for preparing phosphotungstic heteropoly acid solution

The invention discloses a method for preparing a phosphotungstic heteropoly acid solution. The method comprises the following steps: performing first-section bipolar membrane electrodialysis on a tungstate solution (or a mixed solution of tungsten and phosphorus), so the pH value of the solution is reduced to 5.5-7.5; performing heating conversion after phosphorous coordination for one-section electrodialysis solution (or the mixed solution of the tungsten and the phosphorus is directly subjected to heating conversion after one-section electrodialysis); cooling the solution, then performing second-section bipolar membrane electrodialysis, and controlling the pH value to be 1.0-3.0 to obtain a heteropolyphosphatotungstate solution; performing ion exchange transformation decontamination to obtain the phosphotungstic heteropoly acid solution. According to the method, inorganic acid is not consumed, and impurity anions are not introduced, so that not only a tungstate solution can be acidified, but also most of sa