多孔介质中磷负载纳米铁运动特性的模型试验

Model tests on the transport behavior of phosphate-sorbed nano zero-valent iron in porous media

纳米零价铁在多孔介质中的运动能力影响其作为污染地下水修复材料的应用潜力。已有研究多采用一维柱试验研究纳米零价铁的运动行为,对于其二维运动行为的报道有限。自主研发了模拟多孔介质中纳米颗粒运动的模型试验系统,采用细、中、粗3种不同粒径的玻璃珠模拟土体,通过取样测量和图像分析等方法获得了磷负载纳米铁在多孔介质中的运动行为。一维柱试验结果表明磷负载纳米铁在中玻璃珠和粗玻璃珠中均有一定的运动能力,其液相回收率分别为50.3%和41.0%,而在细玻璃珠中运动能力较差;二维模型试验表明磷负载纳米铁在中玻璃珠中的滞留量随距离逐渐降低,而在粗玻璃珠中则呈现出滞留量随距离先升高后降低的趋势。由模型试验结果分析可知,磷负载纳米铁的运动和滞留过程与多孔介质孔隙结构和流速密切相关,颗粒阻塞与表面沉积等不同物理过程的共同作用导致了其在不同粒径多孔介质中运动特性的差异。研究成果可用于评估磷负载纳米铁的运动能力及分析其在多孔介质中的运移和滞留机制,为纳米零价铁技术的工程应用和环境风险评价提供参考依据。

The mobility of nano zero-valent iron(nZVI) will greatly affect its potential application as a remediation material for polluted groundwater. One-dimensional(1 D) column tests are commonly used in previous works to study the transport behavior of nZVI. However, the reports about the two-dimensional(2D) transport behavior of nZVI are still very limited. In this study, model test systems were developed to simulate the transport and retention of nanoparticles in porous media. Glass beads of different sizes(fine,medium and coarse) were used to simulate the porous media. The motion behavior of phosphate-sorbed nZVI(PS-nZVI) in porous media was obtained by sampling and image analysis. Results of 1D column tests show that PS-nZVI has certain mobility in medium and coarse glass beads with liquid-phase recoveries equal to 50.3% and 41.0%, but has poor mobility in fine glass beads. Results of 2D model tests show that the retention of PS-nZVI in medium glass beads decreases with the distance, while the retention in coarse glass beads increases first and then decreases with the distance. Results show that the transport and retention process of PS-nZVI is affected by both the particle size of porous media and the flow velocity. The combined influence of clogging and surface deposition leads to the different transport and retention behaviors of PS-nZVI in glass beads of different sizes. The results of this study can be used to evaluate the mobility of PS-nZVI and analyze its retention mechanism in porous media, and provide a reference for engineering application and environmental risk assessment of nZVI technology.