以超聲波輔助過硫酸根離子降解水中之異丙醇

Abstract

隨著台灣科技業的蓬勃發展，有機溶劑的使用量也隨之提高，其中異丙醇( Isopropyl alcohol, IPA )為一種無色、易揮發的有機溶劑，廣泛應用於半導體業的晶圓清洗、濕蝕刻等製程之乾燥用有機溶劑，對人體也具有吸入、攝入及吸收毒性，成為汙染環境的潛在威脅，因此如何妥善處理廢水、廢氣中的異丙醇便成為目前實廠需面對的問題。 超聲波技術波能夠增加反應中污染物和自由基之碰撞次數，有效降解水中有機汙染物；本研究利用超聲波引發之空蝕效應( Cavitation effect )造成水中過硫酸根離子( S2O82- )發生熱裂解反應，釋放出高反應性之硫酸根自由基( SO4˙- )及氫氧自由基( OH˙ )，進而促進異丙醇之氧化分解。本研究探討於不同之超聲波輸出功率、過硫酸鹽添加濃度、初始pH值、初始IPA濃度等不同反應條件下水中異丙醇降解效率的變化。 在超聲波功率500 W、初始pH 5.0、過硫酸鹽濃度1.66 mM、4.16 mM、8.32 mM之系統中，50 ppm的IPA經120分鐘反應後之去除率分別為30.7 %、69.8 %、56.2 %，降解反應動力學呈擬一階反應(k=0.0033、0.0094、0.0069 min-1)；在超聲波功率500 W、初始pH 5.0、過硫酸鹽濃度8.32 mM、20.8 mM、41.6 mM之系統中，250 ppm的IPA經120分鐘反應後去除率分別為65.2 %、80.2 %、76.4 %，降解反應動力學呈擬一階反應(k=0.0079、0.0142、0.0115 min-1)。最佳操作條件為500 W、初始pH 5.0及添加IPA初始濃度五倍之過硫酸鈉。透過優勢自由基鑑定實驗可知，超聲波/過硫酸鈉降解IPA系統之優勢自由基為氫氧自由基。 透過本研究所得知最佳操作條件可提供未來實廠應用之評估參考，降低IPA對環境水體及人體之前在危害。

With the development of high-tech industries in Taiwan, significantly increasing of wastewater was discharged for various organics. Isopropanol (IPA) is one of volatile organic compounds (VOCs), which is widely adopted in the semiconductor industry as a cleaning agent at diverse stages of wafer surface washing and cleaning processes. It is also used as a solvent in paint, lithography, pharmaceutical, and rubber manufacture industries. The IPA-containing wastewater may cause adverse effect on water quality and human health. Therefore, it is necessary and stringent to find an applicable treatment technology to remove IPA from water. The use of ultrasonic (US) processes for wastewater treatment is technically feasible by many reports, which can oxidize various pollutants by using cavitation phenomenon and radicals generated during the reaction. This study aims to evaluate the effects of US, persulfate (PS), and US+PS on IPA removal in aqueous solutions, respectively. To understand the effects of operating parameters for implementing sonochemical degradation of IPA at an effective level. The effects of initial IPA concentration, PS concentration, ultrasonic power, and initial pH were studied and discussed. The degradation of IPA and its major degradation intermediates were also be investigated by using a purge and trap gas chromatograph (GC) with flame ionization detection (FID) system and high performance liquid chromatography (HPLC). The results show that PS process was significantly enhanced in the presence of ultrasound. PS process in the presence of US can reach about 80.2 % of IPA decomposition in 120 minutes with the US power of 500 W at pH 5.0, with an initial IPA concentration of 250 ppm and a PS/IPA ratio of 5:1. The identified predominant radical is hydroxyl radical. Therefore, US/PS process is an effective method for degrading IPA in aqueous solutions.