吳芳瑞－以UV/H₂O₂光催化反應處理水中背景有機物之研究
Catalyzed oxidation of Natural Organic Matter in Water by UV/H2O2
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腐植質為一非均質結構複雜之聚合物，佔自然水體中有機碳50％；其假想結構為芳香族苯環主體結構，周圍包圍碳氫化合物、酚類及金屬等，在自然水體中不易為微生物分解。在自來水處理過程中與消毒劑作用產生消毒副產品，對人體健康具有潛在性危害。由於傳統自來水處理方式對腐植酸去除效果不佳，一般需使用高級處理程序加以去除。本研究探討利用UV/H₂O₂光催化反應礦化腐植酸之可行性及處理流程中腐植酸特性之改變。

利用UV/H₂O₂光催化處理腐植酸，除了較傳統方式具較佳之處理效率外，亦可達到完全礦化腐植酸之優點，減少二次污染物的產生。UV/H₂O₂之處理效率隨著反應系統條件不同而改變，但大致上皆可達到80％以上之有機碳去除率。由於UV/H₂O₂反應系統使用之H₂O₂為一強氧化劑，光解產生之氫氧自由基具更高之氧化力，因而H₂O₂之殘留亦須加以重視。在不同的實驗條件下，H₂O₂會遵循不同的反應途徑，進而有不同的殘留情形。當短波長之紫外光無法有效穿透燈罩時，會使H₂O₂光解速率下降；水體中氧原子之存在，會使H₂O₂光降解速率會隨著水體中有機物初始濃度越高而變慢，殘留較多H₂O₂；當H₂O₂本身初始濃度過高時，系統不再以氫氧自由基氧化有機物為唯一之反應途徑，亦會殘留較多H₂O₂；而水中之鹼度離子會捕捉氫氧自由基而加速H₂O₂光降解，降低H₂O₂殘留量。

經UV/H₂O₂光催化反應後，腐植酸溶液之總碳濃度隨著反應時間而遞減，而溶液之無機碳濃度隨反應時間而增加，顯示光催化反應會持續將溶液中之腐植酸礦化。同時經UV/H₂O₂光催化處理後，腐植酸之整體分子量從大分子量逐漸往小分子量移動，顯示光催化反應主要將腐植酸分解成分子量較小的化合物。FTIR圖譜變化，顯示不同照光時間之腐植酸官能基有些微改變，其中以脂肪族及芳香族C-H鍵之變化最為明顯，其餘官能基變化並無明顯之變化。

The humic substances are heterogeneous polymers that take major possession of organic carbon in natural water. Humic substances in natural water can cause disinfection byproducts in water treatment and thus have potential health risk to humen. The conventional drinking water treatment process can remove only 10 to 50% of humic substances, and the advanced process is necessary for its removal. Advanced Oxidation process (AOP) can effectively mineralize organic compounds and reduces the secondary pollution and have been widely used for control of organic pollutants in water and wastewater treatments. The UV/H2O2 is used in this study to evaluate the suitability for control of Natural Organic Matter (NOM) in drinking water.

H2O2 is an oxidant itself and may cause human health concern, it is thus important to determine the H2O2 residual. When the quartz tube is used as the filter, more H2O2 decomposition is observed. When oxygen exists in water, the increase of the NPOC initial concentration will decrease the H2O2 degradation rates. There is an optimum H2O2/NPOC molar concentration ratio in the UV/H2O2. In general, the increase of H2O2 initial concentration will increase the H2O2 residual, but the difference of NPOC residual is not significant. The alkalinity is a hydroxyl radical trap, and the presence of alkalinity will reduce the H2O2 residuals. The higher the concentration of alkalinity, the lesser the H2O2 left in water. However, when the short wavelength UV can not effectively utilized, different results will be observed.

The concentration of total carbon decreases with the reaction time, and the concentration of inorganic carbon increases with the reaction time. It means the UV/H2O2 keeps mineralizing the humic acid in water. The use of GFC and UF showed that the higher molecular weight humic acid is oxidized to lower molecular weight humic substances. The FTIR spectrum showed eight major absorption peak of humic acid. FTIR spectrum also showed that the absorption of aliphatic and aromatic C-H decrease significantly with the reaction time, and no apparent changes were observed for the other functional groups.