地下水中五氯酚污染物整治技術研究

Study on Remediation Technologies for Pentachlorophenol Pollutant in Groundwater

劉家福(Chia-Fu Liu)

指導教授 ： 劉敏信

朝陽科技大學/理工學院/環境工程與管理系/碩士(2009年)

摘要

氯酚化合物在自然環境中為一種難分解有機化合物，其中五氯酚為一疏水性有機污染物，一旦污染環境吸附於土壤，進而影響到地下水水源，造成土壤及地下水污染。而二氧化碳具有化學性質不活潑、無毒性、安全性佳、價格便宜以及取得較容易等優點，因此本研究利用超臨界二氧化碳之綠色技術配合修飾劑萃取地下水中五氯酚污染物，尋求最佳萃取條件，並以化學氧化法進行降解試驗。
首先採用未受污染之地下水添加五氯酚分別配置未飽和、飽和及過飽和之水樣，此地下水pH值乃屬中性水樣，導電度及氧化還原電位性質則與其他一般地下水性質相似。在超臨界流體萃取方面，為尋求萃取時之最佳條件與個別的效率，本研究乃針對不同溫度、壓力以及甲醇修飾劑之使用比率進行探討。結果顯示三種水樣，在未添加甲醇修飾劑情況下，最佳萃取效果皆可達96%以上。而添加2.5%、5%(v/v)甲醇修飾劑情況下，三種水樣最佳萃取效果也可達97%以上。
而在化學氧化法試驗，本研究以Fenton氧化法與過硫酸鹽法作為實驗分析，並結合二氧化鈦光觸媒配合紫外光探討地下水中五氯酚之降解。在Fenton試驗中，以過氧化氫濃度206 mM與硫酸亞鐵濃度14.4 mM 為其操作條件；過硫酸鹽試驗中，配合過硫酸鈉濃度16.8 mM與硫酸亞鐵濃度14.4 mM，其最佳降解效果可達94%，使用此二種化學氧化法，配合適當的化學劑量，即可達到最佳效果。二氧化鈦光觸媒試驗中，添加0.1%二氧化鈦時於UV光強度中具有最佳五氯酚降解效果，當添加更高二氧化鈦濃度時，則因遮蔽效應降低五氯酚的降解效率。若以超臨界流體萃取五氯酚之水樣，再進行化學氧化法試驗，相較直接應用於地下水中五氯酚之化學氧化降解，將能降低化學藥劑量之使用，減少環境二次污染。

關鍵字

Fenton氧化法 ； 超臨界流體 ； 五氯酚 ； 二氧化鈦 ； 光觸媒 ； 過硫酸鹽法 ； 地下水

並列摘要

Chlorophenols are a type of organic compound difficult to decompose in the natural environment. Pentachlorophenol, among which, is a hydrophobic ionizable organic pollutant. Once the environment is polluted by adsorption in the soil, it affects the groundwater sources, causing soil and groundwater pollution. Supercritical carbon dioxide has the characteristics of being inactive, non-toxic, safe, relatively low in price, and easy to obtain. Therefore, the main objective of this research was using the green technology of supercritical fluid with methanol modifier to extract the pentachlorophenol pollutant in groundwater. The best extraction efficiency was then determined, followed by chemical oxidation experiments to destroy pentachlorophenol.
First, pentachlorophenol was added to non-contaminated groundwater to make unsaturated, saturated and oversaturated groundwater samples, of which, the groundwater pH value is neutral with its electrical conductivity and oxidation reduction potential similar to common groundwater. Therefore, it can be used as a reference for general groundwater remediation. While conducting supercritical fluid extraction, in order to determine the optimal conditions and individual efficiencies, this study investigated different temperatures, pressure and the addition ratio of methanol modifier. During the extraction for unsaturated, saturated and oversaturated pentachlorophenol in groundwater, the extraction efficiency was found above 96% without adding modifier. However, the extraction efficiency was determined above 97% when 2.5% and 5% v/v methanol modifier was introduced.
In the chemical experiment, this research applied the Fenton oxidation reaction, Persulfate oxidation reaction and TiO2 photocatalysis with UV light to removal the pentachlorophenol pollutant in groundwater. In the Fenton oxidation reaction, hydrogen peroxide solution of 206 mM and ferrous iron of 14.4 mM were prepared for the reaction. As for the persulfate oxidation reaction, sodium persulfate solution of 16.8 mM and ferrous iron of 14.4 mM were prepared for the reaction, the removal efficiencies were determined above 94% for both chemical oxidation reactions. Using the two chemical oxidation methods accompanied by appropriate chemical reagents, optimal removal efficiency can be achieved. In the TiO2 photocatalyst reaction, addition of 0.1% TiO2 provided the best pentachlorophenol removal efficiency in the UV light. However, when adding higher concentration of TiO2, due to the shadowing effect, the removal efficiency of pentachlorophenol was reduced. After using the supercritical fluid to extract pentachlorophenol from the groundwater followed the chemical oxidation experiment, the amount of chemical reagents can be reduced and so will the environmental secondary pollution.

並列關鍵字

Persulfate method ； TiO2 ； Photocatalysts ； Fenton oxidation ； Groundwater ； Pentachlorophenol ； Supercritical fluid extraction

參考文獻

87. 桂椿雄，「超臨界流體萃取法之簡介」，化學，第56卷，第4期，第303-309頁（1998）。

1. Abbott, A., Green Chemistry and the Consumer, (2003).

2. Abraham, M. A. and Sunol, A. K., “Supercritical Fluids: Extraction and Pollution Prevention,” American Chemical Society, Washington, D.C. (1997).

3. Ajzenberg, N., Trabelsi, F., and Recasens, F., “What’s New in Industrial Polymerization with Supercritical Solvents? A Short Review,” Chemical Engineering and Technology, Vol. 23, pp. 829-839 (2000).

4. Augugliaro, V., Plamisano, L., and Sclafani, A., “Photocatalytic Degradation of Phenol in Aqueous Titanium Dioxide Dispersions,” Toxicity of Environmental Chemistry, Vol. 16, pp. 89-109 (1988).