Method for preparing phosphotungstic acid using ammonium paratungstate as raw material

The invention discloses a method for preparing phosphotungstic acid by taking ammonium paratungstate as raw material. It comprises following steps: (1) mixing ammonium paratungstate with inorganic acid at 0-60 Deg. C and getting active tungstate, and the molar ratio between inorganic acid and ammonium paratungstate is 10: 1 -100: 1; (2) mixing active tungstate and phosphoric acid at 20-90 Deg. C and getting phosphotungstic acid solution; and the molar ratio between phosphoric acid which accounts as H3PO4 and ammonium paratungstate is 1.1: 1- 50: 1; (3) making phosphotungstic acid precipitate from solution, drying, crystallizing and getting crystal phosphotungstic acid. By adding inorganic acid precipitant to precipitate phosphotungstic acid, then crying and crystallizing, it can increase its purity further. The invention is characterized by simple process, non use of high concentration of strong acid and flammable organic extractant, low content of phosphate radical in product and suitility for being uses as