製備具芬頓複合觸媒脫色效能之光電極濾網及模組建置之研究

Abstract

傳統高級氧化淨水技術，具高耗能、環境不友善及氧化反應途徑單一等問題，導致不具競爭優勢而限制應用性，有鑑於此，本研究研發電泳沉積法、沉浸塗佈法及陽極氧化法等三種光電極濾網之創新製備方法，將二氧化鈦觸媒以不同方式披覆於不鏽鋼或鈦金屬濾網基材上，成為一高接觸面積之濾網型光電極，以確保污染物與電極反應；於製備出具芬頓複合觸媒脫色效能之光電極濾網後，新創一種光電極濾網脫色模組，其具有系統免加藥，陰極以二電子轉移反應自產H2O2；於電場環境驅動電子遷移，減少光觸媒電子再回復現象；現地(in-situ)提供鐵觸媒，並能還原再利用以減少污泥量及具光電芬頓複合觸媒之多元化反應途徑等創新特點。 於鍍層特性分析結果可知，製程最簡便之電泳沉積式光電極濾網，其鍍層行為模式屬兩階段線性趨勢，當鍍層大於穩定層時，則進入電子傳遞效率減少之擴散層，而溶劑選擇除了考量介電常數/黏度比外，應考量二氧化鈦顆粒與基材附著性之關係；製程最彈性之沉浸塗佈式光電極濾網，則應用混摻P25法簡化製備程序，僅需1次塗佈即可達到4次 SGDC之塗佈效果，解決傳統SGDC繁雜製備程序之問題，同時優化孔洞特性；陽極氧化法光電極濾網，則不同於前兩者以不鏽鋼為基材，係以鈦網長出適當奈米鈦管之直徑與長度比，以獲得較佳光電流。 於效能驗證部分，證實光電芬頓複合觸媒脫色方法，較單純光或單純電反應模式具加成脫色效果；其中，P25混摻溶膠凝膠沉浸塗佈法之光電極濾網脫色效果最好，因其孔洞性最佳而有最顯著的芬頓(Fenton)反應，而電泳沉積法製備程序最為簡便，於實廠應用需進行尺寸放大之考量下，本研究另開發一旋轉電泳沉積專利技術，製備出大尺寸之圓環狀光電極濾網，並輔以雙陽極系統來提升芬頓效果，經實廠廢水效能驗證證實，芬頓複合觸媒之光電極濾網具高效脫色能力。 綜觀上述，本研究除成功研發光電極濾網製備技術外，從效能驗證及氧化模式分析上，證實芬頓複合觸媒之光電極濾網具高效加成脫色能力，並成功放大尺寸至實廠廢水處理，提升高級氧化處理程序之價值與應用性。

The application of conventional advanced oxidation processes in water treatment is restraint and sometimes remains less competitive when compared with other treatment technologies due to high energy demand, less pathways of reaction, and environment unfriendly problems. In this study, a novel photo-electrode filter using stainless steel or titanium mesh substrate with titanium dioxide catalyst coating layer for wastewater pollutant decomposition was proposed. With the large surface area, this photo-electrode filter mesh provides full contact between organic pollutants and electrodes to accelerate the reactions. Subsequently, an innovative photo-electro filter module applicable for decolorization of wastewater using Fenton-catalyst with multiple reaction pathways was developed. The cathode produces H2O2 under two-electron transfer without need for chemical dosing; the electron recombination phenomenon of photo-catalyst could be reduced under electro-field; in-situ supply of Fe2+ catalyst can be regenerated at cathode to minimize the ferric sludge production. Technological breakthroughs have been achieved in photo-electrode filter preparation methods. Three catalyst coating processes have been performed for the preparation of photo-electrode filter including electrophoretic deposition (EPD), sol-gel dip-coating (SGDC) and anode oxidation. Two-stage linear trend model was found for the coating behavior of EPD. When the coating layer is greater than the stable layer and reaches into the diffusion layer, a decrease of electron transfer efficiency was observed. For the selection of solvent, not only the dielectric constant/ viscosity ratio, but the performance of substrate adhesion between the TiO2 particles and the metal substrate shall be taken into consideration; P25 SGDC, a coating procedure modified with P25, is developed to simplify the coating process of SGDC. It was found that optimization of pore structure and the same coating effect comparable with 4 times coating with SGDC could be achieved in just one layer of coating with P25 SGDC; In contrast to EPD and SGDC photo-electrode filter, the anode oxidation coating procedure allows the titanium nanotubes to grow on titanium mesh substrate directly. Excellent photo-current could be obtained for certain diameter / length ratios of titanium nanotube. After the preparation of photo-electrode filter, this study has shown that superior decoloring of wastewater could be achieved with Fenton-catalyst reactions when compared with either photochemical reaction or electrochemical reaction alone. Among all photo-electrode filters prepared by three coating methods, the best decoloring performance was observed with the P25 SGDC photo-electrode filter, due to its high porosity of TiO2 coating layer which resulted in outstanding Fenton reaction. However, EPD is the most simple and suitable method for electrode scale-up. In order to implement photo-electrode filter in industrial scale, a rotary EPD patented technology was developed to prepare large-scale ring photo-electrode filter equipped with dual anodes module to intensify the Fenton reaction. In conclusion, this study proposes a high potential photo-electrode filter module coupled with Fenton-catalyst reactions. It could provide a cost-effective and environmentally-friendly solution for decolorization of wastewater.