Zhuang Heng, Yang Guang-Yu, Fu Xian-Lei, Jiang Zhe-Yuan, Du Yan-Jun
Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety, Institute of Geotechnical Engineering, Southeast University, Nanjing 211189, China.
Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety, Institute of Geotechnical Engineering, Southeast University, Nanjing 211189, China; Baiyun District Branch of Guangzhou Municipal Bureau of Planning and Natural Resources, Guangzhou 510080, China.
Sci Total Environ. 2024 Mar 20;917:170421. doi: 10.1016/j.scitotenv.2024.170421. Epub 2024 Jan 28.
Leachate comprising organic contaminants such as dichloromethane is frequently discharged into groundwater at contaminated sites and unlined landfills. Soil-bentonite backfills in vertical cutoff walls are extensively employed to contain the flow of contaminated groundwater, thereby safeguarding the downstream groundwater environmental quality and ecosystem. This study presented a comprehensive evaluation of effects of dichloromethane-impacted groundwater on hydraulic conductivity and microscopic characteristics of soil-bentonite backfills amended with polymer namely polyanionic cellulose and microscale zero-valent iron. The results showed the amended backfills exhibited lower hydraulic conductivity than the unamended backfill regardless of the permeant type, i.e., tap water and dichloromethane solution. Scanning electron microscopy coupled with energy-dispersive spectrometry analyses demonstrated that polyanionic cellulose hydrogel could effectively coat sand, bentonite, and microscale zero-valent iron particles, providing protection of bentonite particles against attacks imposed by the dichloromethane and multivalent iron ions, and diminish aggregation of microscale zero-valent iron particles in the amended backfills. X-ray diffraction results indicated there was no intercalation of polyanionic cellulose and microscale zero-valent iron into the montmorillonite platelets of bentonite particles. Based on the Fourier Transform Infrared Spectroscopy Spectra analysis, a new functional group (-CH) was identified on the polyanionic cellulose amended bentonite particles. The results demonstrated that amendment with polyanionic cellulose and microscale zero-valent iron is a promising approach to improve the performance of soil-bentonite backfills in containing flow of dichloromethane-impacted groundwater.
包含二氯甲烷等有机污染物的渗滤液经常排放到受污染场地和无衬砌垃圾填埋场的地下水中。垂直防渗墙中的土壤 - 膨润土回填材料被广泛用于遏制受污染地下水的流动，从而保护下游地下水环境质量和生态系统。本研究全面评估了受二氯甲烷影响的地下水对添加了聚合物（即聚阴离子纤维素和微尺度零价铁）的土壤 - 膨润土回填材料的水力传导率和微观特性的影响。结果表明，无论渗透液类型是自来水还是二氯甲烷溶液，添加后的回填材料的水力传导率均低于未添加的回填材料。扫描电子显微镜结合能量色散光谱分析表明，聚阴离子纤维素水凝胶可以有效地包裹沙子、膨润土和微尺度零价铁颗粒，保护膨润土颗粒免受二氯甲烷和多价铁离子的侵蚀，并减少添加后回填材料中微尺度零价铁颗粒的聚集。X射线衍射结果表明，聚阴离子纤维素和微尺度零价铁未插入膨润土颗粒的蒙脱石片层中。基于傅里叶变换红外光谱分析，在聚阴离子纤维素改性的膨润土颗粒上鉴定出一个新的官能团（-CH）。结果表明，添加聚阴离子纤维素和微尺度零价铁是一种有前景的方法，可以提高土壤 - 膨润土回填材料在遏制受二氯甲烷影响的地下水流动方面的性能。
