부산대학교 도서관

Soil contamination is one of the major environmental issues in the many developed countries, and contamination with heavy metals poses a direct threat to the effective utilization of agricultural land in Taiwan. There is thus a need to develop fast and effective remediation processes for use with contaminated agricultural land, with in-situ model remediation tests being an important part of this. A number of works have applied electrokinetics to the removal of heavy metal contaminants from the soil, with successful results. However, the test samples of contaminated soil in these studies were all manually prepared and on a laboratory scale. When it comes to practical applications in the field, there are still many problems that need to be noted and overcome. This study applies Circulation-Enhanced Electrokinetics (CEEK) on the near-real scale to clean lead contaminated soil in Nantou City, Taiwan. The operational solution concentration of 0.01 M EDTA-2Na and 0.01 M Na_2CO_3 was used in this experiment. The initial experimental conditions were set according to the previously optimum parameters, including a total current of about 10 A, neutral pH, 20% moisture content in the soil and the use of a certain amount of chelating agent. During this experiment, the variations in the pH value and lead concentration in the both the soil and operational solution were measured, and this data was analyzed to obtain the lead mass balance. Moreover, the sample was also examined to measure the operational solution pH, moisture content and current at certain time intervals. The data obtained in this way were then used to assess the removal efficiency with regard to lend contamination, and the operating cost of the CEEK process. After 63 days of treatment, the following conclusions were obtained. The lead removal efficiency was close to 64%, and the average lead concentration decreased from 7,246 mg kg^(-1) to 2,612 mg kg^(-1). The operational cost of electricity for removal is 9.83 NT dollars per 1% lead in an area of 1.0 m^2. The pH and electrical conductivity of the soil were maintained in a neutral and stable conditions, an indication that the CEEK process has little impact on soils. The fertility of the treated soil was slightly less than that of the untreated soils, and thus additional fertilizer was necessary. If further improvements can be made to the CEEK system, then this could make the electrokinetics technique more attractive to potential users. The results show that the use of a closed and non-infiltrated channel for the CEEK can help reduce the effects of effect and problem of deformation over long-term operations, meaning that the channel can be reused, thus reducing costs. The electrical current and voltage can be maintained in a stable condition, and thus the CEEK process is very stable. In addition, the temperature of the operational solution is close to the atmospheric temperature.