| Summary: | 碩士 === 元智大學 === 化學工程學系 === 90 === In a typical semiconductor manufacturing process, a large amount of isopropyl alcohol (IPA) is used for wafer cleaning. The wafer cleaning process invariably generates a large quantity of wastewater that contains complex and refractory organic compounds. In general, the wastewater can be divided into two types. The first is a high-strength wastewater with a chemical oxygen demand (COD) as high as 50,000 mg/L and a small amount of IPA. The second is a waste organic solution containing over 70% IPA and fewer refractory organic components. The present research is to adopt two treatment proper procedures for dealing these wastewater and waste solution. Experimental tests are conducted to study their treatment feasibility and efficiency and to identify the optimum operating condition.
The treatment process for tackling the high-stream wastewater consisted of air stripping, evaporation and Fenton oxidation. Air striping was intended to recover as much as possible the IPA in the wastewater. The air stripped wastewater was then separated into two parts by evaporation. The residual portion became much viscous and was strongly colored compared to the original wastewater. Due its small amount (less than 3% of the original wastewater), the residue could be conveniently incinerated. The condensate was then treated by Fenton oxidation to the discharge standard. Tests were conducted to examine the effects of pH, amount of hydrogen peroxide (H2O2), ferrous sulfate (FeSO4) and operating temperature on the oxidation efficiency. Various kinetic models were employed to the test date and to describe the reaction mechanisms.
The waste organic solution contained over 70% of IPA. Hence IPA recovery became a primary focus. Air stripping was used to remove IPA form the waste solution. The gas mixture passed through a condenser that was maintained below -5℃ and was able to remove over 75% of IPA from the gas mixture. The remaining IPA in the lean gas mixture went to a activated carbon fiber (ACF) column for further IPA recovery. The combined air stripping, condensation and ACF adsorption was able to recover over 98% of IPA in the original waste organic solution.
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