製備二氧化鈦電極及其染料廢水處理之應用

Abstract

人工染料廢水因含高負荷之色度、總懸浮固體物及生化需氧量，且具高度穩定性及生物難降解等特性，因此傳統廢水處理廠仍無法有效地降解，導致此類型廢水經處理後之水質仍無法達到放流水標準。高級氧化程序已被證實可有效處理染料廢水，包含O3/UV、H2O2/UV、TiO2/UV和傳統芬頓反應，但這類型處理方法操作成本昂貴且需要不斷添加化學藥劑，還可能造成二次污染等問題；因此，電化學方法因具有高效率及高度可應用性，不易產生二次污染等優勢，成為近年主要處理方式。 本研究以二氧化鈦奈米材料複合不鏽鋼網製備二氧化鈦電極，結合光電化學反應系統，藉由陽極不斷釋出亞鐵離子，與陰極所產生之雙氧水反應，針對傳統芬頓技術進行優化及整合，具有環境相容性且節能效率高，易於自動化操作。本研究以溶膠凝膠法製備二氧化鈦膠體溶液，藉由添加界面活性劑聚乙二醇增加膠體溶液之黏滯度，有利於提升不鏽鋼網基材表面鍍層之固化量，並以高溫550℃鍛燒加強鍍層固化強度及顆粒結晶性，且可確保添加之界面活性劑完全去除，並將Degussa P25結合溶膠凝膠法，可省去重複浸鍍之程序，增加二氧化鈦鍍層之孔洞結構，其中以添加P25 50 g/L具有最高孔洞體積。此外，將此複合電極結合本系統光催化及光電芬頓反應，針對Orange G作降解，具最佳降解效率。

Synthetic dyes are considered a high strength pollutant due to its significant contribution to suspended solids (SS), and chemical oxygen demand (COD) content in dye wastewater. Its high stability under sunlight and resistance to microbial attack also makes dye wastewater treatment problematic. Conventional wastewater treatments are proven inefficient in treating the dye wastewater to meet the standard set by the environmental protection bureau in Taiwan. Advanced oxidation processes (AOPs) including O3/UV, H2O2/UV, TiO2/UV and conventional Fenton’s process, which undergo significant development, shows great effectiveness for the decontamination of dye wastewater. However, the use of these methods is not completely accepted at present because they are relatively expensive and experiencing operational problem such as the need of continuous addition of the chemical reagent and further treatment for the iron sludge produced during the process.

In this study, fabrication of nanocrystalline TiO2 flexible film electrodes immobilized on stainless steel substrate and its utilization for the photoelectron reaction system has been conducted. The technology is based on the continuous electro-generation of H2O2 at a suitable cathode, along with an iron catalyst release from the TiO2 electrode into the treated solution to produce oxidant "∙OH" at the bulk via Fenton’s reaction. This process can improve and optimize the conventional Fenton’s process because of its environmental compatibility, high energy efficiency and automation amenability. The results showed that the TiO2 was successfully functionalized by the sol-gel method and that the film immobilization can be controlled by addition of poly ethylene glycol (PEG) in sol-gel methods.Calcination at 550oC can improve the crystalline structure of TiO2 film and enhance the strength of its immobilization on stainless steel mesh. Under this temperature, the surfactant was also guaranteed to be completely removed. The role of Degussa P25 in modified sol-gel method can increase the film thickness by a dip-coating process. 50 g/L P25 loading in the alkoxide sol was found to be the maximum concentration for obtaining good films, mainly attributed to the enhancement of the film’s pore structure. To compare with the conventional Fenton’s reaction and other AOPs, photoelectro-Fenton combined with photocatalytic process for degradation of Orange G exhibited higher decolorization efficiency.