Remediation of contaminated soil by the combination of supercritical fluid extraction and electrochemical reaction.

本课题旨在研究超临界流体萃取与电化学反应相结合的污染土壤修复工艺。超临界流体萃取的作用是分离污染土壤中的有机物质，并应用电化学反应将萃取的有机物质在有机溶剂中完全分解。考虑的有机材料包括多芳烃、多氯化烃和沥青。我们首先开发了一种半流型超临界流体萃取器，可以在室温到750k的温度范围内使用，压力可达50mpa。提取器的体积约为500cc，将污染土壤样品放入一个小容器中，置于提取器中。将高压柱塞泵和预热器引入萃取器，产生高温高压水。从萃取器流出的废水…More通过压力控制阀，并被收集到样品校正器中。提取程序后，剩余的样品从提取器中回收进行分析。为了检验实验装置和程序，分别在473 K和573 K下测定了苯和二氯苯的溶解度。通过与苯的参考数据的比较，发现本实验方法给出了可靠的结果。下一步，我们将沥青污染土壤作为含有机土壤的模型材料。结果表明，在573 K和30 MPa的萃取条件下，沥青质可以完全分离。萃取剂分为水溶性萃取剂和不水溶性萃取剂。采用溶剂萃取法提取水溶性组分。将溶剂萃取得到的溶液直接引入电化学电池，提取的有机物通过电化学反应完全分解。对有机化合物在水和CO2溶剂中的溶解度计算方法进行了理论研究。提出了用于预测超临界CO2和超临界水溶解度的定量结构与活度关系方程。该方程的优点之一是计算所需的信息是分子结构数据和熔化温度。利用该方程，可以定量预测二恶英在超临界流体中的溶解度。少

The purpose of this project was to develop a remediation process of contaminated soils by the combination of the supercritical fluid extraction and electrochemical reaction. The supercritical fluid extraction functioned to separate organic materials from contaminated soil, and the electrochemical reaction was applied for the complete decomposition of the extracted organic materials in organic solvents. The organic materials considered were polyaromatic hydrocarbons, polychlorinated hydrocarbons, and asphaltens. We firstly developed a semi-flow type supercritical fluid extractor, which can be used in the temperature range from room temperature to 750 K and pressures up to 50 MPa. The volume of the extractor was about 500 cc. The contaminated soil sample was put into a small container and set in the extractor. The high temperature and high pressure water was produced with a high pressure plunger pump and pre-heater, which was introduced into the extractor. The effluent from the extractor … More went through the pressure control valve and was collected into a sample corrector. After the extraction procedures, the remained sample was recovered from the extractor for analysis. In order to check the experimental apparatus and procedures, the solubility of benzene and dichlorobenzene were measured at 473 K and 573 K.From the comparison with the reference data of benzene, it was found that the present experimental procedure gives reliable results. In the next step, we used asphalten contaminated soil as the model materials of organic containing soil. It was found that the asphaltene can be separated completely by the extraction at 573 K and 30 MPa. The extractants were consisted from water soluble and water insoluble fractions. The water soluble fractions were extracted with solvent extraction. The solution obtained from the solvent extraction was introduced into the electrochemical cell directly, and the extracted organic materials were decomposed completely by the electrochemical reactions.The theoretical study to investigate the solubility calculation method for the organic compounds in water and CO2 solvents was investigated. The quantitative structure and activity relationship equation was proposed for the solubility prediction for the supercritical CO2 and supercritical water. One of the advantages of this equation was that the information needed for the calculation is molecular structural data and melting temperature. With this equation, we can predict the solubility of dioxins in supercritical fluids quantitatively. Less