METHOD FOR TREATING WASTE ETCHANT CONTAINING PHOSPHORIC ACID, ACETIC ACID AND NITRIC ACID USING TRI-OCTYL PHOSPHATE AND TRI-BUTYL PHOSPHATE AS EXTRACTANTS

摘要

PURPOSE: To provide a method for separating and recovering acids from the waste etchant by extracting and separating acetic acid and nitric acid from a waste etchant containing phosphoric acid, acetic acid and nitric acid using tri-octyl phosphate as an extractant, extracting phosphoric acid of low purity from raffinate using tri-butyl phosphate and recovering refined phosphoric acid from the low purity phosphoric acid. CONSTITUTION: In a method for recovering acids from a waste etchant by solvent extraction, the method for treating the waste etchant comprises a phase separation process of contacting phosphoric acid with an organic phase in which a waste solution consisting of acetic acid, nitric acid or a mixture thereof, tri-octyl phosphate as an extractant and a diluent are mixed in a prescribed concentration ratio, uniformly mixing the mixture and stationing the mixture so that the mixture is separated into an extract phase containing acetic acid, nitric acid or a mixture thereof and raffinate containing phosphoric acid; a separation process of recovering acetic acid and nitric acid by stripping the acetic acid and nitric acid extracted organic phase using water; and a phosphoric acid recovering process of recovering refined phosphoric acid by stripping the phosphoric acid using water after extracting phosphoric acid from the separated raffinate using an organic phase in which tri-octyl phosphate as an extractant is mixed with a diluent.