| Summary: | 碩士 === 國立臺南大學 === 環境生態研究所碩士班 === 96 === In the past, dioxins-contaminated environmental media were mostly treated by thermal process which has been considered energy-consumable and costly. The aim of this study is to discuss the treatment of dioxins-contaminated environmental media by Fenton process. Fenton process is one method involved in advanced oxidation processes (AOPs). Due to the addition of hydrogen peroxide and ferrous ions, OH free radical (OH•) is able to attack dioxins-contaminated environmental media by heterogeneous catalytic oxidation. Although previous studies has pointed out that Fenton processes is possible to treat dioxins with high removal efficiency, However, only simulated media were discussed in these studies. Thus, the feasibility of Fenton process on the treatment of actual dioxins-contaminated environmental media is worthwhile.
In this study, primary characteristics of environment media such as fly ash sampled from waste treatment plant, soil and sediment sampled from contaminated site were discussed. Base on the results of Atterberg experiment, fly ash is classified as CL (low compressibility sandy inorganic clay); soil and sediment are classified as OL (to lower to compressibility organic matter silty soil) by unified soil classification system (USCS). Base on the analysis of X-ray fluorescence (XRF) and X-ray diffractomer (XRD), it shows that the main crystalline phase of fly ash is NaCl, and the main crystalline phase of soil and sediment is SiO2. Base on the analysis of thermogravimetry analysis (TGA), weight loss in the range from 25 to 900℃ is obviously, which means that organic content was involved in these environmental media. Toxic equivalent (TEQ) of dioxin for these environmental media is analyzed by HRGC/MS (High Resolution Gas Chromatograph/Mass Spectrometer), it shows that these environment media sampled are above the regulation standard, which are classified as dioxin-hazardous waste.
The analysis of liquid and solid phase for three dioxins-contaminated environmental media after Fenton process was done in this study. It shows that as the dosage of hydrogen peroxide for Fenton Process is increased, the removal efficiency of dioxin in solid phase is increased. By the way, the removal efficiency of organics in liquid phase is also increased. In order to discuss the relationships between dioxin and organic content in solid phase of dioxins-contaminated environmental media after Fenton process, weight loss of 100~550, 550~900 and 100~900℃ were evaluated as organic content in solid phase of these environmental media by furnace. It reveals that weight loss of 100~900℃ for fly ash and sediment has higher relativity to TEQ of dioxin. However, weight loss of 100~550℃ for soil has higher relativity to TEQ of dioxin. As to the contributions of TEQ for each dioxin isomers from these environment media, 1,2,3,7,8-PeCDD, 2,3,7,8-TeCDD, 1,2,3,7,8-PeCDF and 2,3,4,6,7,8-HxCDF are major dioxin species in fly ash. Furthermore, 1,2,3,4,6,7,8-HpCDD, OCDD, 1,2,3,4,6,7,8-HpCDF and OCDF are major dioxin isomers in soil and sediment. Apparently, the specific profiles of dioxin in these environment media after Fenton process are not changed apparently for high organic content involved.
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