METHOD FOR SEPARATING AND RECOVERING PHOSPHORIC ACID FROM ACETIC ACID-NITRIC ACID-PHOSPHORIC ACID TYPE MIXED ACID WASTE LIQUID

PROBLEM TO BE SOLVED: To provide a method for separating and recovering phosphoric acid from an acetic acid-nitric acid-phosphoric acid type mixed acid waste liquid with high efficiency and good selectivity for a long period by which a good separation property between an oil phase and a water phase in a stripping process is maintained for a long period. SOLUTION: The separating/recovering method comprises an extraction process for selectively dissolving acetic and nitric acids in the extractant solution to extract by mixing the waste liquid containing acetic acid, nitric acid, and phosphoric acid with the extractant solution containing trialkyl phosphate and a saturated aliphatic linear hydrocarbon having a carbon number of 6-13, a recovery process for recovering phosphoric acid from a residual liquid left by the above extraction process, and a stripping process for bringing the obtained acetic/nitric acids-containing extractant solution into contact with a stripping water, wherein the extractant solution can circularly be used by feeding back the oil-phase stripping solution obtained from the acetic acid and nitric acid stripping process to the acetic acid and nitric acid extraction process to recirculate and use the extractant. COPYRIGHT: (C)2010,JPO&INPIT