柠檬酸及EDTA对土壤中六价铬的淋洗修复效果研究

Leaching Remediation of Hexavalantfrom a Contaminated Soil Using Citric Acid and EDTA

主要研究柠檬酸和EDTA淋洗剂对六价铬污染土壤的淋洗修复效果,重点考察淋洗剂浓度、液固比、淋洗时间和淋洗方式对土壤六价铬去除效果的影响。研究结果表明:随着淋洗剂浓度的增加,柠檬酸淋洗剂对供试土壤六价铬的去除率逐渐升高,最高为54.0%,而EDTA淋洗剂对供试土壤的去除率先升高后降低,浓度在0.4 mol·L^(-1)时达到最高,为66.3%;土壤六价铬去除率随液固比的增加呈现先升高后降低的趋势,当液固比为7∶1时,0.5 mol·L^(-1)柠檬酸和0.1 mol·L^(-1)EDTA淋洗剂对供试土壤六价铬的去除率最高,分别为69.6%和61.9%;增加淋洗时间,供试土壤六价铬的去除率逐渐升高,2 h后增幅不大;就清洗方式而言,EDTA淋洗剂一次加入对土壤六价铬的去除效果最好,而柠檬酸淋洗剂宜采用二次加入一次分离的方式。

Citric acid and EDTA were used as leachants to remedy hexavalant chromium contaminated soil in this experiment, which aiming at studying the impact of the concentration of leachants, liquid-solid ratio, leaching time. The results indicated that the hexavalant chromium removal ratio raised gradually using citric acid that can reach to 54. 02%, the hexavalant chromium removal ratio raised at first and then fell that can reach to 66. 30% when EDTA was used at 0. 4mol＆#183;L-1 . When the liquid-sol-id ratio was enlarged, the hexavalant chromium removal ratio raised at first and then fell that can reach 69. 60% and 61. 90% u-sing citric acid and EDTA at 7：1 sold-liquid ratio. When the leaching time was increased, the hexavalant chromium removal ra-tio of contaminated soil raised, fell and raised gradually at last. In addition, the growing rate was little after 4 hours, and therefore 2 hours was confirmed as the best leaching time. When changing the cleaning methods, the separation method of adding twice and separating once was suit to citric acid, while adding twice and separating twice separation method was suit to EDTA.