METHOD OF PRODUCING THERMAL ORTHOPHOSPHORIC ACID Russian patent published in 2012 - IPC C01B25/20 C01B25/234 

FIELD: chemistry.

SUBSTANCE: invention relates to production and purification of thermal orthophosphoric acid and can be used in chemical industry. Elementary phosphorus containing 0.54-0.6 wt % iodine is fed into a current of dried inert gas or air and reacts with 56-64% nitric acid at 95-100°C. Dried inert gas or air is passed through the reaction mass at 134-145°C. When contaminated elementary phosphorus is used, for example in form of phosphorus-containing wastes, it is first purified by passing in a current of dried inert gas or air. The obtained acid is cooled to 10-16°C and then purified by crystallisation at 12-22°C n the presence of an inoculating crystal. Crystalline orthophosphoric acid is dissolved in water and passed through cation-exchange sorbents at a rate of 0.4-1.5 l/h/m², and then through a porous filtration membrane with pore size of 0.1-0.5 mcm at 1-1.5 atm. Further, the acid is evaporated at 50-70°C and at pressure 160-200 mm Hg and recrystallised at 10-16°C.

EFFECT: method enables to obtain orthophosphoric acid with content of metal impurities of 10^-5-10^-6 wt %.

8 cl, 2 ex