| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系所 === 105 === In the field of operation, the Surfactant Enhanced Aquifer Remediation (SEAR) technology, injects or infiltrates surfactant solutions into the aquifer to dissolve and/or mobilize the dense non aqueous liquid (DNAPL). Then the spent surfactant solution is recovered for further treatments. The purpose of this study is to evaluate the effectiveness of two surfactants, TX-100 and SDS, in removing the tar oil DNAPL. The effects of surfactant concentrations and temperatures at different oil-to -water ratios were tested to simulate various DNAPL concentrations present in the subsurface. It is hoped that the results can provide information for the feasibility and economic benefits of the SEAR technology.
The optimum conditions for the two surfactants to remove tar oil DNAPL were at high TPH/surfactant (1/10, w/w) and by 2% SDS and 2.5% Triton X-100. The amount of Tar oil removed was 1998 mg and 1775 mg per mg of SDS and TX-100, respectively. The SDS can dissolve 223 mg more TPH. The Tar oil dissolution was enhanced proportionally by increasing Triton X-100 concentration, but was not related to the SDS concentration. The removal mechanism of tar oil by Triton X-100 at high TPH/surfactant ratios (1/10 to 1/20) is mainly mobilization. On the other hand, when the TPH/surfactant ratio is lower (1/50 to 1/150), the tar oil is removed by dissolution. The removal mechanism by SDS is mainly mobile regardless the ratio of TPH/surfactant is low or high. The CMC value for Triton X-100 and SDS is 59 and 8.4, respectively. This means that Triton X-100 requires more surfactant molecules to form microcells than SDS does. Thus, it is possible that most of the added SDS molecules are dissolved in the tar oil, resulting in the increased DNAPL mobility.
The use of SEAR has some concerns. The increased mobility may lead to DNAPL sinking. Thus, the temperature test was conducted to enhance the solubility of Tar oil by Triton X-100. The results show that at 60 ℃ and TPH/surfactant ratio of 1/10 and 1% TX-100, the O/W (oil/water) value is increased to 0.8483. That means when temperature increases, the solubility of the tar oil increases and the optimal concentration of TX-100 for tar oil dissolution reduced to 1%. However, at high TPH/surfactant ratios, the mobilization mechanism is still occurring and is the main interaction mechanism between Tar oil and TX-100. The increase of NAPL mobility is more useful than dissolution in removing large amounts of TPH and improvement of flushing efficiency.
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