光輔助電化學方法之水楊酸降解反應研究

Abstract

在廢水處理中以高級氧化程序成效最佳，依據不同的反應機制分類，其中以Fenton程序與光催化反應應用最為廣泛。本研究將光催化反應與Fenton程序結合，以二氧化鈦薄膜電極為陽極，二氧化鈦受UV光照射後躍遷至導電帶的光電子會導入陰極中再對氧氣進行還原反應，還原反應生成過氧化氫擴散至反應系統中與亞鐵離子進行典型的Fenton程序。由於反應過程中持續受到UV光的影響，所以反應機制包含photo-Fenton程序，將鐵離子還原成亞鐵離子，如此一來，反應能持續進行直到有機物被完全分解。 以溶膠-凝膠法製備二氧化鈦薄膜電極，由SEM分析得知表面型態；XRD分析其晶型結構，再以Debye-Scherrer方程式計算出粒徑大小；XPS圖譜得知二氧化鈦與ITO玻璃之間的吸附作用與其表面與氧原子鍵結方式；UV-Vis分析其吸收度並估算出能隙；最後再由I-V曲線得知當提供正偏壓光電流效應。 水楊酸在醫療與合成工業上用途廣泛所以產生的廢水也相當可觀。本研究以0.05mM水楊酸為有機污染物進行降解反應。反應系統使用TiO2/ITO陽極、PTFE-碳布為陰極分別討論加入不加入鐵離子、與加入亞鐵離子、鐵離子的系統(AT_CC、AT_CC_Fe2+與AT_CC_Fe3+系統)，研究發現以AT_CC_Fe2+系統的反應性最佳。接著再對影響系統因素一一做探討，例如起始pH值、亞鐵濃度、光照強度、氧氣進 料流量等影響。另外也討論額外在系統中施加電流與反應系統之間的關係。

Advanced oxidation process is the best method for wastewater treatment. According to different classification of reaction mechanisms, Fenton process and photocatalytic reaction have most widely applications. In this study, photocatalytic reaction was combined with Fenton process. Titanium dioxide thin film electrode is used to be the anode, and photoelectrons on TiO2 surface will be irradiated by UV light and then transit to the conductive band to move to cathode to reduce oxygen in the cathode. When the reduction reaction occurred, hydrogen peroxide was produced and it diffused to the system to react with ferrous ion in the solution, which is called Fenton process. As the whole reaction process continued to be irradiated by UV light, the reaction mechanism contains the photo-Fenton process. In this way, ferriciron ions will be reduced to ferrous ions, and the organism will be decomposed completely. Titanium dioxide thin film electrode was prepared by sol-gel method. The surface morphology was developed by SEM. We also analyzed crystal structure by XRD and made use of Debye-Scherrer equation to calculate the particle size of Titanium dioxide. Adsorption and bonding way with oxygen atoms between Titanium dioxide thin film and ITO glass were developed by XPS analysis. Absorbance data was obtained by UV-vis analysis and the energy gap was estimated. Finally, the I-V curve showed the photocurrent effect when a positive voltage was added to the system. Salicylic acid generated much wastewater because of its popular applications of medical treatment and synthetic industry. We chose 0.05mM Salicylic acid as the organic pollutant and proceeded a degradation reaction. Reaction systems are AT_CC, AT_CC_Fe2+ and AT_CC_Fe3+, which the best one is AT_CC_Fe2+. Then we discussed some factors and how they affect the systems which were mentioned above. The factors, for example, are the initial pH value, the concentration of Fe2+, light intensity, and the flux of feeding oxygen. Finally, the relationship between extra added current and reaction system was discussed.