Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 21008, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 21008, China.
Environ Pollut. 2019 Feb;245:9-19. doi: 10.1016/j.envpol.2018.10.105. Epub 2018 Oct 27.
Efficient injection and distribution of nanoparticles in porous media are considered a formidable technical hurdle for injection-based in situ remediation. One approach to enhance the mobility of nanoparticles in an aquifer is to use surface modifiers. In this study, nanoscale magnesia (NMgOs), an innovative and effective remedial material for cadmium (Cd) removal from groundwater, was modified with the negatively charged and eco-friendly humic acid to enhance its mobility in aquifers. A two-dimensional reactor (60 × 50 × 10 cm), with 2 injection wells and 30 monitoring wells was designed, constructed, and sand-packed in the laboratory to simulate a saturated aquifer. The simulated aquifer was pre-contaminated with Cd to simulate a plume in groundwater. The distribution of injected unmodified NMgOs and humic acid-modified NMgOs slurry were evaluated in the reactor. The radius of influence (ROI) of humic acid-modified NMgOs was estimated to be approximately 5 cm based on visual observation, while no ROI was apparent for the unmodified NMgOs because of their aggregation at the bottom of the injection wells. The concentrations of Cd and magnesium (Mg) were monitored in all 30 monitoring wells at different time intervals to evaluate the effectiveness of Cd removal. The breakthrough curve analysis revealed that humic acid enhances the transport of NMgOs in the saturated porous media. Furthermore, the results of scanning electron microscopy-energy dispersive x-ray (SEM-EDX) characterization of silica sand before and after injection of NMgOs verified the presence of 5.78% of Mg from humic acid-modified NMgOs and 0.19% from unmodified NMgOs at 35 cm downgradient of the injection wells, which are consistent with the conclusion drawn from the breakthrough curves.
在基于注入的原位修复中，高效地将纳米颗粒注入和分布在多孔介质中被认为是一个艰巨的技术难题。一种增强纳米颗粒在含水层中迁移能力的方法是使用表面改性剂。在这项研究中，纳米氧化镁（NMgOs）作为一种从地下水中去除镉（Cd）的创新且有效的修复材料，被带有负电荷和环保的腐殖酸改性，以增强其在含水层中的迁移能力。设计、建造并在实验室中用砂填充了一个二维反应器（60×50×10 cm），其中有 2 个注入井和 30 个监测井，以模拟饱和含水层。模拟含水层预先用 Cd 污染以模拟地下水中的羽流。评估了在反应器中注入的未改性 NMgOs 和腐殖酸改性 NMgOs 泥浆的分布。根据肉眼观察，腐殖酸改性 NMgOs 的影响半径（ROI）估计约为 5 cm，而未改性 NMgOs 则没有 ROI，因为它们在注入井的底部聚集。在不同时间间隔监测了所有 30 个监测井中的 Cd 和镁（Mg）浓度，以评估 Cd 去除的效果。突破曲线分析表明，腐殖酸增强了 NMgOs 在饱和多孔介质中的传输。此外，注入 NMgOs 前后的硅胶砂的扫描电子显微镜-能量色散 X 射线（SEM-EDX）特性分析结果证实，在注入井 35 cm 下游处，腐殖酸改性 NMgOs 中有 5.78%的 Mg，而未改性 NMgOs 中有 0.19%的 Mg，这与突破曲线的结论一致。
