- 學位論文
以電化學方法處理受鎘鉛等重金屬污染之土壤之研究
The Study on the Removal of Heavy Metal Contaminated Soil by Electrochemical Treatment
摘要
電化學整治方法是在現地整治相當有效的方法。其重要機制包括水之電解、重金屬離子之吸附/脫附，沉澱，水力流，電滲透流，及離子遷移等。本研究首先探討污染土壤中鉛、鎘離子之移除。土壤之pH值對重金屬離子之移除有重大之影響。除了吸附/脫附，沉澱和土壤之pH值有密切關係外，電滲透流之大小和方向，也受它的影響。因此土壤試體之pH值需調整至適當值。在水力梯度下，其適當值pH值約在2∼4之間。但在無水力梯度之情況下，pH值則宜在3∼6之間。為維持土壤試體之適當pH值分佈，因此運用了各種加強整治之方法。這些方法包括使用緩衝溶液、使用陽離子交換膜、及使用醋酸及醋酸鈉之緩衝液作前處理。這些加強整治方法在改善移除效率方面都證明是相當有效的。當使用緩衝液整治時，效果最好，Cd+2之移除率可達99%，而鉛可達85%。在無水力梯度下，其pH值之分佈、 電滲透係數對時間之變化、土壤殘餘重金屬之分佈和有水力梯度時其相對應之整治情況相當接近，唯移除率較低。 根據前面實驗之結果，進行模擬現場之整治，將陰極槽及陽極槽重新設計。整治之結果，銅離子之移除率可達63%，證明現地整治是可行的。並以理論方式，求得電極各種排列方式之電壓及電場強度分佈，以兩排圓形電極中間插入平板電極最佳，六角排列次之，平行排列、交錯排列無效面積最高。
並列摘要
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.
參考文獻
延伸閱讀
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