Application of Solvent Extraction to the Treatment of Waste Acid Mixture discharged from IT relating Industry

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In this study the separation technology of waste acid mixture discharged in the production of semi-conductor and liquid crystal display, namely the separation method of acid mixture with solvent extraction was investigated and the process for separation was established The separation methed of acids from waste acid mixture in the production of liquid crystal display was investigated based on the research results carried out last year, where we found that the solvent extraction was a suitable method to separate each acid from waste acid mixture in the production of semi-conductor,The basic study on extraction and stripping of phosphoric, acetic, nitric, sulphuric and hydrochloric acids was carried out by using decanol, TBP(tri-butyl phosphate), TOP(tri-octyl phosphate) etc. as extractants. We clarified the extraction mechanism of each acid with these extractants as well as the characteristics of extraction and stripping of each acid. It was found that the extraction behavior of acid in single compornent is largely different from that of acid in two or three acid components. Though in the extraction process of acid generally the separation of acids is possible, but the concentration of acid is impossible, the concentration and separation of acids will he possible if the characteristics of acid extraction is suitably applied to the acid mixture. For example, if other mineral acids are intentionally added to dilute phosphoric acid waste, the phosphoric acid is recovered in the separated and concentrated form.Based on the fundamental experimental data, the acid separation process was established and the demonstaration test for the proposed separation process was carried out using a small scale pilot plant At the same time the method to improve the recovery with keepinghigh purity was investigated.