利用連續式電透析處理含有二甲基亞楓的廢水並評估其回用可能性

Abstract

隨著光電產業及半導體產業的發達，製程規格品質要求日趨嚴苛，因此製程中所使用的超純水量也相對增加並且品質要求亦提高。有鑒於台灣水資源缺乏且配合政府回收水比例要求，園區內紛紛設置污水處理廠來進行廢水回收及再使用。一般園區採用匯流方式將廢水集中，以混凝或其他高級處理等方式進行廢水品質的改善，然而，廢水中含有各種有機及無機物質且此種方式並無法使水質規格有效達到超純水等級，因此也無法代替超純水使用於製程中。倘若能在製程機台後端加裝較小規模的處理設備並針對特定的污染物設計處理，那麼不僅處理效率提升也能較易達到超純水的品質要求。因此，本研究在於評估一套針對光電及半導體場中常見之有機物，二甲基亞楓 (dimethyl sulfoxide, DMSO)，所設計的水處理設備其處理效率。此外，將處理水進行回用基板清洗的步驟，並發展一包括採樣及分析的技術，以了解回用水對於玻璃基板清洗是否有殘留或影響

Continuous Electrodeionization (CEDI) 常被使用於超純水的製造，特別是在光電及半導體產業。CEDI 因結合離子交換樹脂混床與電透析使其處理效率要比一般傳統混床或電透析效率要高。本研究藉由改變電流 (I) 與產水比例 (Q) 進行評估 CEDI 處理二甲基亞楓廢水效率，並由量測進流水與出流水的 TOC 值來說明成果。研究中發現，當處理水濃度較低時電流值的大小並不會對於處理效率有很大的影響，而另一方面產水百分比則會大幅使處理效率變化，當比例為 70% 時，效率最佳可達去除率 90% 以上。 分析方式以自動熱脫附儀 (Auto Thermal Desorption, ATD) 搭配氣相層析儀 (Gas Chromatography, GC) 與質量偵檢器 (Mass Spectrum Detector, MSD) 分析氣相中與液相中的二甲基亞楓。此法將 DMSO 收集於填有Tenax TA的吸附管中，接著將吸附管加熱使 DMSO 脫附並進行分析，此法可有效的分析 DMSO，其偵測極限可達 1 ng。另一方面，以 outgassing 進行樣品採樣，在一密閉系統中，加熱玻璃基板使因高溫而從玻璃基板脫附出的污染物收集在吸附管中，接著以 ATD-GC/MS 進行污染物分析。其中，溫度及載流氣體流量為主要影響收集效率的因子，適用於本研究所主要分析的對象 DMSO 的最佳操作條件分別為: 120˚C 及 300 ml/min。

As the product specifications of the photoelectric and semiconductor industries are tightening constantly and the ultra pure water consumption is also increasing proportionately. Due to limitedwater resource and in compliance with the new environmental protection policy in Taiwan, it is mandatory for the industry to set up an onsite wastewater treatment system and implement water reuse program. To achieve this goal, most of the factories adopt flocculation/coagulation or other advanced treatment technologies. However, it is ineffective to remove all organic matters from the wastewater. In view of this, the present research is focused on treating dimethyl sulfoxide (DMSO) contaminated wastewater with an innovative treatment train consisting of UV and RO pretreatments followed by a continuous electrodeionization unit. In addition, the research is focused to establish an analytical method for confirming the quality of the reused DMSO wastewater.

Electrodeionization (EDI) has been commonly applied to produce ultra pure water, especially in the semiconductor industry. The continuous electrical regeneration of an internal equipped ion-exchange mixed bed is the main advantage of this emerging technology. EDI couples two well known effects: electrodialysis and ion exchange. The present research studies EDI process efficiency with a series of applied current I and the permeate percentage Q variations. The results show that current has no significant effect on treated water with low inlet COD concentrations, but permeate percentage at 70% offers the optimum removal efficiency. As a whole, the treatment method studied is very effective for a removal of DMSO from the TFT-LCD manufacturing wastewater.

ATD-GC/MS method for measuring gas and liquid DMSO samples was evaluated. The method involved adsorption using Tenax TA adsorbent tube , followed by thermal desorption and gas chromatography-mass spectrometry analysis. The method was effective in the measurement of DMSO and its detection limit is 1 ng. At temperature above XX oC, the efficiency of DMSO collection from the glass base plate was reduced. In a closed system, the temperature of the outgassing chamber and carrier gas flow rate influenced the DMSO collection efficiency. The optimum temperature and gas flow rate for DMSO were 120˚C and 300 ml/min, respectively.