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標題: 利用頂空固相微取法探討水中三鹵甲烷生成速率的可行性
Investigation of the feasibility of studying the trihalomethanes formation kinetics by HS-SPME technique
作者: 林坤樟
關鍵字: trihalomethanes formation rate;三鹵甲烷生成速率;headspace solid-phase microextraction;humic acid;頂空固相微萃取;腐植酸
出版社: 環境工程學系
本研究採用頂空固相微萃取法(HS-SPME)進行上述的動力探討,只需一瓶加氯之水樣,於一定溫度下,在不同時間點不需去氯,利用採樣纖維直接濃縮反應瓶頂空間之氣體再注入GC分析。以三氯甲烷生成為例,顯示與傳統方法有相同之結果,卻可省掉以往研究中需多瓶水樣、除氯等繁複步驟。另外,以頂空固相微萃取法分析CHCl3、CHCl2Br、CHClBr2、CHBr3所得方法偵測極限分別為0.020、0.015、0.026、0.037 µg/L。
研究顯示,利用單瓶水樣不去氯直接以HS-SPME採樣分析水中三鹵甲烷生成速率確實可行。利用此方法探討三鹵甲烷生成速率,研究結果顯示當存在足夠氯劑量時,腐植酸加氯反應,其三鹵甲烷生成動力學符合假一階反應動力模式。氯劑量5 mg/L添加於含2 mg/L腐植酸及0.03 mg/L的溴離子之水溶液,CHCl3最終生成量約佔總生成三鹵甲烷的84.5%,CHCl2Br約13.5%,CHClBr2約2%。CHCl3、CHCl2Br、CHClBr2、TTHMs反應速率常數k分別為0.035、0.067、0.055、0.039(hr-1)。

Chlorination for disinfection purpose of drinking water has lead to the formation of disinfection by-products (DBPs), especially the formation of trihalomethanes (THMs). Due to the harmful potential to human health, THMs have caused great public health concerns. Usually the kinetics of the THMs formation was studied by adding sodium sulfite to stop the chlorination reaction at preset time. Then, THMs was determined using liquid-liquid extraction (LLE) or head space gas sampling by syringe(HSGSS)both coupled with gas chromatography (GC). These analysis processes are tedious. In this study, after mixing sodium hypochlorite with humic acid in water sample, headspace solid-phase microextraction(HS-SPME)was used to collect chloroform occurred in gas phase. After 5 minutes of headspace extraction, the fiber was inserted into GC injection port to determine the amount collected. The process is simpler and faster. In addition, this technique can get lower detection limit for THMs analysis. Detection limits observed were 0.020 μg/L (CHCl3), 0.015 μg/L (CHCl2Br), 0.026 μg/L (CHClBr2) and 0.037 μg/L (CHBr3).
In this study, using single bottle of aqueous sample without removing chlorine to study the formation rate of THMs is feasible. As the result, in presence of excess chlorine, THMs formation proceeds as a pseudo first-order reaction. The formation percentages of CHCl3, CHCl2Br, CHClBr2 of total trihalomethanes (TTHMs) were about 84.5%, 13.5%, 2%, respectively in the solution of 2 mg/L humic acid, 0.03 mg/L bromide and 5 mg/L chlorine dose. In addition, the rate constants of CHCl3, CHCl2Br, CHClBr2, TTHMs were 0.035, 0.067, 0.055, 0.039 (hr-1).
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