METHOD OF WET-PROCESS PHOSPHORIC ACID PURIFICATION Russian patent published in 2000 - IPC

FIELD: inorganic chemistry, chemical technology. SUBSTANCE: invention relates to method of production of phosphoric acid with low content of impurities and used in production of phosphate salts in technique and food industry. Method involves liquid extraction of phosphoric acid with tributyl phosphate from wet-process phosphoric acid carried out at V_o : V_в = (2.5-5.5): 1 at 1-6 stages of contact to form raffinate and extract, washing out stage of the latter and stage of H₃PO₄ reextraction from extract to aqueous phase to obtain product acid containing 25-300 parts of Fe and 250-2000 parts of SO₄ per mln. parts of P₂O₅, and its part is recovered in the process to washing out stage. Purification process is expediently carried out in columns at pulse regime at intensity 100-600 mm/min at extraction stage, 200-1200 mm/min at washing out stage and 400-1600 mm/min at reextraction stage. Raffinate is used in production of fertilizers and product phosphoric acid removed from washing out stage in production of technical salts and phosphoric from reextraction stage in production of food salts. EFFECT: improved quality of purified phosphoric acid, increased yield of product. 5 cl, 2 tbl, 1 ex