| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系 === 87 === In this study, six typical Taiwan agricultural soils that spiked with Cd, Cu, and Pb were used. Chemical extraction (distilled water, EDTA, Citric acid, 0.01N HCl, and 0.001N HCl) and physical sequential sedimentary technology were used to remediate the heavy metals contaminated soil. We also examined the treatment and the recovery of EDTA. In the adsorption experiment, results showed that the metals adsorption capacity to the soils were related to the soil pH. The saturated adsorption capacity would increase with the raise of soil pH. The adsorption ability of soil to metals were as follow Pb＞Cu＞Cd. From the results of sequential extraction procedure, the percentage of Cd, Cu, or Pb''s distribution in the lower-energy bounded forms in the soil would increase with the decrease of soil pH. After water washing or 0.001N HCl extraction, soil Cd and Cu fractional distribution in various soil separates (sand, coarse silt, fine silt, and clay) were similar to that of untreated soil. Soil Pb that distributed in the low-energy bounded forms would decrease with the decrease of particle sizes. From the specific surface area test, the concentration of Cd, Cu, or Pb in various soil particles were proportional to the specific surface area with soil sizes. Cd and Cu had similar bound strength to all soil particle and Pb appeared to be more strongly bounded to the smaller particle sizes. EDTA was the most effective extractant to all of theses soils, 0.001N HCl and distilled water were the worst. The addition of Na2S in EDTA extracting solution made almost all Cd, Cu, or Pb in solution precipitate. The EDTA recovery rates were 18~58% to Cu, Cd, and Pb. These results indicate that using chemical extraction and physical sedimentary technology were effective. It can be another direction to remediate the heavy metals contaminated soils.
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