METHOD FOR RECOVERING ACID FROM MIXED WASTE ACID BY USING SOLVENT EXTRACTION METHOD AND VACUUM EVAPORATION

摘要

A method for collecting acid from mixed waste acid is provided to re-perform a vacuum evaporation process after a solvent extraction process in order to completely remove impurities as well as preventing the inner corrosion of a vacuum evaporator. A method for collecting acid from mixed waste acid comprises the following steps of: treating the mixed waste acid generated in a manufacturing process of liquid crystal display devices using an organic solvent to separate into an aqueous phase layer including phosphoric acid and metallic components and an organic phase layer including acetic acid and nitric acid; primarily vacuum-evaporation-treating the liquid of the aqueous phase layer to remove acetic acid and nitric acid and separating into a remaining liquid including the phosphoric acid and metallic components; diffusion-dialysis-treating the remaining liquid to obtain a phosphate solution with metallic component of 1 ppm or less; and concentrating the phosphate solution in a secondarily vacuum evaporation treatment.