| 摘要: | 近年來新興汙染物開始廣受關注，在這當中又以藥物及個人保健用品使用最為頻繁，由於傳統水處理方法無法有效地完全去除此類化學品，因此容易微量地殘留於水體中，造成生態環境與人體的危害。高級氧化程序成為一個可以去除新興汙染物的方法，尤其是結合紫外光的高級氧化程序。相比其他UV/高級氧化程序，UV/chlorine程序具有成本效益且降解效能在某些汙染物上更具有優勢。故本研究主要目標為利用UV/chlorine程序結合電化學方式來降解水楊酸這種新興汙染物，並依據實驗結果歸納出最佳操作條件，評估此程序應用於水楊酸降解的可行性。
研究主要分成三部分，第一部分為以投藥方式加入次氯酸鈉於系統中，觀察其降解水楊酸的可行性。第二部分為在系統中以電化學方式將氯離子氧化生成自由氯(次氯酸根離子、次氯酸)，不需外加任何氧化劑;第三部分為加入紫外光，並結合第二部分的電化學生成自由氯。研究結果顯示，最佳操作條件為電流密度5 mA cm-2，氯離子濃度0.05M及pH 4。水楊酸降解會符合擬一階反應。經過反應時間60分鐘後，水楊酸降解效率可達96%，反應常數為0.0544 min-1。在加入紫外光後能增強水楊酸降解的效率，並且降低反應的活化能，其主要歸功於自由基的生成。UV/chlorine降解水楊酸也會符合擬一階反應。在反應時間60分鐘內已降解水楊酸超過99%，反應常數為0.0844 min-1。最後推導水楊酸的降解途徑會先從自由基在苯環上的取代反應開始，經過去羧酸與奪氫反應後形成鄰苯二酚和1,2-苯?，再經裂環後形成不飽和產物，最終礦化成二氧化碳與水，同時消毒副產物(DBP)也會在程序中生成。
;In recent years, emerging pollutants have attracted widespread attention. Among them, pharmaceuticals and personal care products are used most frequently. Conventional wastewater treatment cannot remove these chemicals effectively, which leads to trace remain in water body, causing ecological and human health problems. Advanced oxidation processes (AOPs) have become a method that can remove emerging pollutants effectively, especially the UV-based AOPs. Compared with other UV-based AOPs, UV/chlorine process is more cost-effective and the degradation efficiency is more advantageous in certain pollutants. Therefore, this study used UV/chlorine process which was combined with electrochemical process to degrade salicylic acid (SA), which was a kind of emerging pollutants. Then, according to the results to optimize the operating condition and assess the feasibility of this process for degrading SA.
This research was divided into three part: First, sodium hypochlorite was added into the system to confirm the feasibility of degradation of SA by chlorine; Second, the free chlorine(including hypochlorite and hypochlorous acid) was electrochemically oxidized from chloride in the system, without adding additional oxidant. Third, the electro-generated free chlorine was irradiated by UV irradiation. In the results, the optimal operating condition of current density, chloride concentration and pH value were found to be 5 mA cm-2, 0.05M and pH 4, respectively. The SA degradation conformed pseudo first order reaction. After 60-min reaction, the SA degradation efficiency could reach 96% and the reaction constant was 0.0544 min-1. It was found that UV irradiation could enhance the degradation and reduce the activated energy because of the generation of free radicals. Also, the SA degradation by UV/chlorine conformed pseudo first order reaction. After 60-min reaction, the SA degradation efficiency could reach >99%, and the reaction constant was 0.0844 min-1. Finally, a possible degradation pathway was proposed that SA degradation initiated by substitution reaction on benzene ring by radicals. Moreover, catechol and 1,2-Benzoquinone may be form by decarboxylation and hydrogen abstraction. Then, ring opening may occur to formed unsaturated products and mineralize to CO2 and water finally. Disinfection by-product (DBP) may also be formed during the SA degradation. |
