| 摘要: | 2006 年薄膜電晶體液晶顯示器(TFT-LCD)製造和半導體製造兩產業之產值分別佔光電業和半導體業總產值之66%和53%，廢水量則分別佔光電業和半導體業總廢水量之85%和66%。TFT-LCD製程過程中會產生大量的廢水，其中包含了大量的蝕刻廢液，所以需要尋找一個經濟有效的處理技術來處理蝕刻廢水，是台灣TFT-LCD產業的一個重要的工作。本研究以TFT-LCD實廠蝕刻廢液為處理對象，針對廢液中的化學需氧量(COD)，探討其處理方法。因為TFT-LCD實廠在製程過程中產生廢液裡的化學需氧量，多半都高於放流水標準，所以本研究將使用芬頓程序與電芬頓程序處理蝕刻廢液，針對實廠蝕刻廢液中COD，在經過兩種不同程序後的處理效果來做探討。在實驗中初始pH、亞鐵離子與過氧化氫濃度為程序重要參數，所以經由實驗來找出去除污染物的最佳參數。由結果得知，分別使用Fenton程序與Electro-Fenton程序反應120分鐘之後，在條件pHi=3，[Fe2+]=4mM，[H2O2]=291mM的時候，使用芬頓程序在處理120分鐘後COD最高去除到70.45%，而使用電芬頓程序在條件pH=4，[Fe2+]=3.5mM，[H2O2]=285mM，Ampere=1.5A時處理120分鐘後COD去除效率可以超過芬頓程序達到完全去除。兩種芬頓程序比較後，Electro-Fenton程序在相同的條件下，COD去除的效率可以達到Fenton程序所無法辦到的100%，也能達到放流水的排放標準。過氧化氫添加量的倍數，會因廢水的不同而有所差異。使用電芬頓程序在三種廢水去除COD的過氧化氫加藥量，分別為理論值的1.1、1.5、1.8倍，才能在反應120分鐘後完全去除COD。
Taiwan has one of the major high-technology industry clusters in the world. Manufacturing industries such as, photonics and semiconductors are flourishing in the region. However, various chemicals used in these industries may cause significant pollution when discharged into the environment. In 2006, the output values of TFT-LCD (thin-film transistor liquid-crystal displayer) are 66% and 53% of the total photonics and semiconductor industries, respectively. On the other hand, the corresponding wastewater discharge flow rates from the same industries are 85% and 66%. It is evident that the amount of pollutants produced during TFT-LCD manufacturing substantially increased in the recent years. The volume of these pollutants comes from etching process wastewater. Therefore, finding an effective and economical way to treat etching wastewater is an essential work for the Taiwanese TFT-LCD industry. Advanced oxidation processes (AOPs) are efficient methods to degrade organic compounds. Fenton process is one of these advanced oxidation processes. A new approach to increase ferric reduction efficiency using electro-Fenton procedures has been developed to degrade organic contaminants. In the electrolytic cell, the organic compound is ionized or oxidized by direct electrolysis on the anode. This method uses hydrogen peroxide (H2O2) and ferrous ion to produce hydroxyl radicals to oxidize the contaminants. Ferrous ion is regenerated via the reduction of ferric ion on the cathode.The chemical oxygen demand (COD) in the TFT-LCD etching wastewater exceeds the effluent standards. This study used Fenton process and Electro-Fenton procedures to remove COD from the etching wastewater. The COD removal efficiencies of the electro-Fenton and Fenton method is discussed through the oxidation efficiencies of the process. .The operating conditions used for the Fenton process are: initial pH (2, 2.5, 3, 3.5, 4); ferrous ion concentration (3 mM, 3.5 mM, 4mM); H2O2 concentration (259 mM, 285 mM, 311 mM); and current density (1 A/m2, 1.5 A/m2). Increasing the ferrous ion concentration from 2 to 4 mM increased the hydroxyl radicals and consequently increased the degradation efficiency of COD. Results showed that the COD removal efficiency is optimum using the following operating conditions, Fe2+ = 3.5 mM, H2O2 = 285 M, initial pH＝4.0, current density＝1.5A. Using two (2) hours of continuous electrolysis, the COD removal efficiency increased to 30% compared to that of the Fenton treatment. |
