土柱淋洗法修复铬污染土壤的水力梯度优化试验

Optimization of hydraulic gradient for the remediation of chromium contaminated soil by column leaching

针对重金属污染土壤的修复,淋洗法是一种比较成熟的方式,但目前研究主要聚焦于淋洗剂的选择,而关于水力停留时间对淋洗效果影响的研究相对较少.水力梯度是影响水力停留时间的重要因素,优化水力梯度能够缩短修复周期,降低淋洗成本,有效提高淋洗效率,为现场淋洗修复工程应用提供参考.本文针对人工制备的不同质地的铬污染土壤进行了土柱淋洗试验,探究了土柱淋洗过程中不同水力梯度条件下淋出液的pH值、淋洗液渗流速度和淋洗前后不同类型土壤中Cr(VI)及总Cr含量的变化情况,并根据土壤中Cr(VI)、总Cr去除情况对水力梯度进行了优化,研究结果表明淋洗铬污染土壤的最佳柠檬酸浓度为0.15 mol·L^(-1),淋洗铬污染壤土、砂质壤土和砂土的最佳水力梯度分别为7.2、3.6和1.2,总Cr去除率分别达到82.86%、77.27%和82.15%.

Leaching is one of the most commonly used technologies for the remediation of heavy metal contaminated soil.Most of the previous research focused on the selection of eluent,while few studies took hydraulic retention time(HRT)into consideration.Hydraulic gradient is an important factor affecting HRT.Optimization of hydraulic gradient can shorten the repair cycle,reduce the cost of leaching,and effectively improve the leaching efficiency,which provides valuable insight into field leaching remediation application.In this paper,chromium contaminated soils with different properties were artificially prepared to conduct column leaching experiments.The pH and seepage velocity of leaching solution,and the change of Cr(VI)and total Cr content before and after leaching were studied under different hydraulic gradient conditions.Furthermore,the hydraulic gradient was optimized according to the removal of Cr(VI)and total Cr.The results showed that the optimal concentration of citric acid was 0.15 mol·L^(-1).The optimal hydraulic gradient of leaching chromium contaminated loam,sandy loam,and sandy soil were 7.2,3.6 and 1.2,respectively.Under optimal conditions,the total Cr removal rates were 82.86%,77.27%and 82.15%in loam,sandy loam,and sandy soil,respectively.