| Summary: | 碩士 === 明志科技大學 === 環境與安全衛生工程系環境工程碩士班 === 106 === The indigenous effective microorganism (EM) from Taiwan was used to extract heavy metal cadmium (Cd) form soil, and the extraction efficiency of different extractants was compared using both batch test and soil column study. The results showed that 0.1 M FeCl3 had the maximum extraction capacity of 33.6 mg/kg for cadmium with single extractant agent study, followed by HCl of 32.5 mg Cd/kg of soil, and by EDTA of 29.6 mg/kg . After soil washing test using single agent, the EM treatment had soil pH 4.1, which is greater than that of citric acid treatment had soil pH 2.9. However, EM treatment could extract 22.8 mg/kg cadmium from soil but citric acid could only extract 20.6 mg/kg。 In the soil washing experiment using multiple agents, mixing 0.02 M ferric chloride with 0.1 M citric acid of volume ratio 1:4, the highest amount of 49.3 mg/kg cadmium was extracted from soil. When the non-diluted EM solution was mixed with 0.02 M ferric chloride, 36.7 mg/kg cadmium was extracted. These results suggested that mixing two different agents could have a synergistic effect on cadmium extraction efficiency. In the soil column study, after 25 days of soil washing, mixing EM with 0.1 M CaCl2 showed the best cadmium removal efficiency in the top layer of the soil column, and the residual amount of cadmium in soil was 2.3 mg/kg with the removal efficiency of 95.3%. In the middle layer of soil column, mixing citric acid with CaCl2 could decrease the soil cadmium concentration to 7.5 mg/kg with the removal efficiency of 85%. In the bottom layer of soil column, mixing citric acid with CaCl2 could have residual cadmium concentration of 12.5 mg/kg with the removal efficiency of 75%. Overall, it seemed feasible to use EM as a cleaning agent for removing heavy metal cadmium from soil. EM was less harmful to soil than most chemical agents, and thus it could act as an environment-friendly cleaning agent for removing heavy metal from soil.
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