METHOD OF SEPARATING AND RECOVERING PHOSPHORIC ACID FROM MIXED ACID WASTE LIQUID CONTAINING ACETIC, NITRIC AND PHOSPHORIC ACIDS

PROBLEM TO BE SOLVED: To provide a method capable of highly efficiently, selectively separating and recovering phosphoric acid from a mixed acid waste liquid containing acetic, nitric and phosphoric acids even in a practical large scale production by suppressing the emulsification of an oil phase with a water phase in a settling state in a separation process to enable the circulating use of an extractant solution sufficiently. 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 those acids with the extractant solution containing trialkyl phosphate, a recovery process for recovering phosphoric acid from a residual liquid left by the above process, and a separation process for bringing the obtained acetic/nitric acids-containing extractant solution into contact with a salt-containing water for separation to dissolve and transfer their acids into the above water for separation. The extractant solution can circularly be used by feeding back the oil-phase solution obtained from the separation process to the extraction process. COPYRIGHT: (C)2006,JPO&NCIPI