電芬頓法和陽極氧化法降解甲芬那酸之研究

Abstract

甲芬那酸 (Mefenamic acid, MEF) 是非類固醇止痛消炎藥的一種，常作為牙痛、經痛的處方，此類藥物不容易被傳統污水處理廠有效降解。近年來，陽極氧化法 (Anodic oxidation, AO)和電芬頓法 (Electro-Fenton, EF)廣泛應用於降解新興污染物。因此本研究利用陽極氧化法和電芬頓法降解新興污染物甲芬那酸。 在陽極氧化法實驗當中，分別探討電流密度、陽極材料對降解效果的影響，並且利用高層析液相層析儀來檢測廢水中甲芬那酸的濃度。陽極氧化法降解甲芬那酸符合一階降解速率常數方程式。從實驗中得知，在電流密度5-25 mAcm-2之間，電流密度越高降解效率越佳。實驗比較碳氈、石墨、鈦板作為陽極時，降解效率比較為碳氈＞石墨＞鈦板。利用總有機碳分析儀分析礦化效果時發現，氫氧自由基攻擊碳材料表面，使總有機碳濃度漸漸上升。當電流密度越大時，總有機碳上升幅度越大，降解結束後產生終產物硝酸根離子。 在電芬頓法實驗當中分別探討電流密度、鐵離子濃度對降解效果的影響。電芬頓法降解甲芬那酸符合一階降解速率常數方程式。由實驗中可以得知在電流密度5-25 mAcm-2之間，電流密度越高降解效率越佳，然而15 mAcm-2和25 mAcm-2降解效率效果差異不大。在鐵離子濃度0.05-0.15 mM之間，鐵離子濃度越高降解效果越佳。 在低電流密度下 (5 mAcm-2) ，陽極氧化法降解效率較電芬頓法佳；在施加15 mAcm-2的電流時，電芬頓法降解效果比起陽極氧化法佳；施加高密度電流時，則兩者降解效果不分上下。 陽極氧化法中，當施加電流25 mAcm-2 時，使用石墨當作陽極，石墨當作陰極時，甲芬那酸在20分鐘的時候，去除率達到98%。電芬頓法中，當電流密度25 mAcm-2時，鐵離子0.1 mM時，在20分鐘內降解90%以上的污染物。由此可證明陽極氧化法和電芬頓法可以有效降解甲芬那酸。

Mefenamic acid (MEF) is a kind of nonsteroidal anti-inflammatory drugs (NAISDs), which is used to reduce menstrual pain, migraine headache post-surgical pain, etc. MEF can not be degraded effectively by wastewater treatment plants and be discharged into aquatic environment. Then, MEF is accumulated through bioaccumulation and toxic to ecosystems. Advanced oxidized processes are needed to removed MEF. Anodic oxidation (AO) process and electro-Fenton (EF) process were used to remove MEF. In anodic oxidation experiments, the effect of applied current, electrode materials on removal of MEF are investigated. High performance liquid chromatography, total organic carbon (TOC) were used to analyze the concentration of MEF and identify AO and EF degradation kinetics of MEF and extent of its mineralization. The results indicated that applied current and anode material played two important roles in the MEF degradation. Increasing applied current would lead to a corresponding increase in MEF removal. The carbon felt was a better effective anode for oxidation of MEF because of its large specific surface area. On AO processes, the degradation of MEF followed pseudo-first order reaction. The mineralization of MEF was evaluated by the released NO3- concentration. In electro-Fenton experiments, the effect of applied current, concentration of iron on removal of MEF are investigated. The results indicated that applied current and iron concentration played two important roles in the MEF degradation. During the range of 0.05-0.15 mM Fe2+, increasing Fe2+ concentration would lead to a corresponding increase in MEF removal. After comparing the difference of AO and EF, removal efficiency of AO processes are higher than that of EF processed under low applied current (5 mAcm-2) ; under 15 mA cm-2, removal efficiency of EF processes are higher than that of AO processed; under 25 mA cm-2, removal efficiency of AO processes and EF processes are similar. At the optimum conditions of AO processes (Applied current = 5 mA cm-2, pH =7, electrode gap = 4 cm, Na2SO42- = 0.05 M) , more than 94% MEF degradation were observed within 30 minutes treatment with carbon felt. At the optimum conditions of EF processes (Applied current = 25 mA cm-2, pH =6, electrode gap = 4 cm, Na2SO42- = 0.05 M, Fe2+=0.1 mM) more than 90% MEF degradation were observed within 20 minutes treatment. MEF can be degraded effectively by AO and EF processes.