| Summary: | 碩士 === 國立中山大學 === 環境工程研究所 === 86 === This research was to evaluate the feasibility of using a combined technology of electrokinetic soil processing and Fenton process for in-situ remediation of a sandy loam and a silt loam contaminated by phenol and 4-chlorophenol, respectively. An electric gradient of 1 V/cm and D.I. water in the cathode reservoir were employed in all experiments by electrokinetics. In Fenton process, scrap iron powder and FeSO4 were used as catalysts. When scrap iron powder was placed in the soil column at a distance of 5 cm from the anode, 0.3% hydrogen peroxide was provided in the anode reservoir. The treatment time was kept for 10 days. When FeSO4 solution was used, on the other hand, different concentrations of FeSO4 were provided in the anode reservoir. After a 3-day electrokinetic reaction, 0.3% hydrogen peroxide was used to replace FeSO4 solution in the anode reservoir. The treatment continued further for additional 7 days or 10 days. In this study, the directions of all electroosmotic flows were found to be positive (i.e., from anode toward cathode). Based on the mass balances for target pollutants, different reaction mechanisms were determined. When scrap iron powder was used as a catalyst, "removal" and "destruction" were found to be the dominant reaction mechanisms for Soils No. 1 and No. 2, respectively. On the other hand, when FeSO4 solution was employed, mechanisms of "destruction" and "removal" were found to be associated with concentrations higher and less than 0.0196M, respectively. The results of this study also showed that by adding 1.05g of scrap iron powder as a catalyst, the highest (i.e., 99.7%) destruction and removal efficiency (DRE) of phenol was obtained for Soil No. 1. However, under the same treatment conditions, a DRE of only 36% was obtained for Soil No. 1 contaminated by 4-chlorophenol. In the case of Soil No. 1 contaminated by phenol, it was found that an increase of the amount of scrap iron powder placed in the soil column would delay the arrival of hydrogen peroxide or hydroxyl radical to the cathode reservoir. This can be verified by comparing the cumulative increased mass of phenol in the cathode reservoir for various amounts of scrap iron powder used. When 0.0196M FeSO4 was used as a catalyst, the highest DREs for Soil No. 1 contaminated by phenol and 4-chlorophenol were found to be 99.5% and 89%, respectively. It was also found that the cumulative increased mass of pollutants in the cathode reservoir decreased after three to four days of reaction. When a concentration of FeSO4 less than 0.0196M was used, the cumulative increased mass of pollutants in the cathode reservoir was found to be gradually increasing throughout the treatment period. By using the same operating conditions, a much lower DRE was obtained for Soil No. 2 regardless of the pollutant type. It is postulated that a much higher content of the organic matter associated with Soil No. 2 would be responsible for the finding. It was also found that the capabilities of removing organic pollutants in soil would be about the same for electrokinetic soil processing alone and the technology combined the electrokinetics and Fenton process. However, the latter was found to be superior to the former in terms of chemical destruction of organic pollutants.
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