| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系 === 88 === Trichloroethylene (TCE）is a common industrial chemical. It is often found in the contaminated groundwater aquifer. Trichloroethylene is heavier than water, and only solublize slightly; therefore, a large spill of TCE is likely to move downward through the subsurface until lower permeability features impede its progress. This often results in the formation of a plume or pool(s) of dense nonaqueous phase liquid (DNAPL）in the aquifer plus a trail of residual DNAPL in the downward path. The TCE DNAPL is the source of vapor, disssolved, and sorbed phase of pollutants. TCE was used as an index compound in this study to evaluate the feasibility of chemical oxidation by Fenton''s reagent at natural soil pH=7.1.
Two soil samples with different characteristics were collected form Pingtung Country, Taiwan. The WD soil is a loamy sand with higher soil organic matter(SOM) content of 11.8g/kg , The YP soil, sampled form the aquifer of an illegal dumping site, is a sand with low SOM content（0.7g/kg）. This study evaluated factors such as Fe2+ concentration, H2O2 dose, reaction time, TCE concentration, and SOM content of soil on the oxidation efficiency.
The results showed that the Fenton''s reagent could oxidize TCE in water at natural pH. When TCE concentration of water at
concentration near water-saturation（1100.0 mg/L=8.4mM）, the best oxidation concentration of H2O2, Fe2+, and reaction time were 588.2mM, 2.0mM, and 50min, respectively. When TCE concentration of water-DNAPL phase was 22.8mM, the best oxidation concentration of H2O2, Fe2+, and reaction time were 588.2mM, 10.0mM, and 840 min, respectively. The removal rate of TCE was 98.5%.
The optimum oxidation condition for 22.8mM of TCE in the water-sorpted-DNAPL phase of TCE were H2O2=588.2mM, Fe2+=2.0mM, and reaction time of 840 min. The removal rate of TCE for WD soil was 52.3%, but for YP soil was 89.6%. Because SOM and TCE competed for the ‧OH, the WD soil was oxidized less efficiently than the YP soil.
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