The Study on the Removal of Heavy Metal Contaminated Soil by Electrochemical Treatment
Date Issued
2004
Date
2004
Author(s)
Chou, Shin-Bin
DOI
zh-TW
Abstract
Electrochemical treatment is an emerging technology for decontaminating soil in-situ, which involves electrolysis, adsorption, desorption, precipitation, hydraulic or electroosmotic flow, and ionic transport. The removal of Pb and Cd ions from contaminated soils has been investigated in this study. The pH value of the soil significantly affects the removal of heavy metal ions. Besides the adsorption / desorption and precipitation are strongly affected by the pH of the soils, it can also influence the magnitude and direction of electroosmotic flow, and so the pH of the soil specimen must be regulated adequately. The appropriate range of pH values has been found to be 2〜4, and the pH must not exceed 6. Various enhancing methods of ensuring adequate pH distribution were employed herein, including methods that involve buffer solution, cation exchange membranes and pretreatment with acetic acid and acetate buffered solution. Such methods proved to be highly effective in improving the removal efficiency in all instances. The removal efficiency of Cd+2 can reach 99%, and that of Pb+2 can reach 85%, when buffered solutions are used for the electrochemical treatment. Remediation without hydraulic head is also investigated. The various results are similar with that of remediation with hydraulic head. Only the removal efficiency is less which is the impact of no hydraulic flow.
The bench scale tests are employed to examine the feasibility of in-situ remediation. The anode and cathode chambers are designed to facilitate the removal of contaminants from soil, the results prove to be satisfying. The removal efficiency of copper ions is 63%. That means the method we are developing is useful for in-situ remediation.
The effect of electrode configuration is also examined theoretically by voltage and electric field distribution. The array of a plate electrode between two rows of cylindrical electrodes is the best, then the hexagonal array, and then parallel type and cross type.
Subjects
pH值
緩衝液
電極排列
電化學整治
移除率
electrical treatment, buffered solution
removal efficiency
electrode configuration
pH
Type
thesis
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