纳米颗粒和微米颗粒的团聚以及典型纳米/微米复合颗粒在多孔介质中的运移

Investigation of transport of colloids in porous media such as soil is of great interest in multiple disciplines such as Soil Science, Environmental Engineering and Colloid and Interface Sciences. Aggregation is one of the primary factors that govern colloid transport in porous media. Whereas transport of homoaggregates in porous media has been reported in the literature, transport of heteroaggregates in porous media has not been investigated to date. The objective of this study is to theoretically and experimental investigate heteroaggregation of nanoparticles with microparticles and transport of the typical heteroaggregates in porous media. We will firstly conducted experiments such as dynamic light scattering to investigate the heteroaggregation of nanoparticles with microparticles and develop models to quantify the heteroaggregation rates. Then we will conduct flow cell experiments to examine attachment and detachment of typical heteroaggregates of nanoparticles with microparticles on/from surfaces and use models to simulate the processes. Finally, by combining the convection-diffusion equation with the aforementioned heteroaggregation models, attachment and detachment models, and colloid filtration model, a comprehensive model is obtained to simulate the transport of typical heteroaggregates in porous media and column and field experiments are used to testify the model. Findings from this project have implication to using microbes and nanomaterials for soil remediation, and to making regulations for prevention of groundwater from being contaminated by hazardous colloids and colloid-associated pollutants.

研究胶体在土壤等多孔介质中的运移是土壤学、环境工程和胶体与界面等学科的交叉研究方向。团聚是影响胶体在多孔介质中运移的关键因素之一，目前有关同种胶体所形成的团聚体的运移已有研究，关于不同种胶体团聚后所形成的复合颗粒的运移研究则还未见报道。本项目拟从理论分析和实验模拟两方面研究纳米颗粒和微米颗粒的团聚以及团聚后所形成的典型纳米/微米复合颗粒的运移。研究内容主要包括：通过动态光散射仪等实验研究纳米颗粒和微米颗粒的团聚，建立定量纳米颗粒和微米颗粒团聚的模型；进行流动小室实验研究典型纳米/微米复合颗粒在固相表面的吸附和解吸，建立模拟纳米/微米复合颗粒吸附和解吸的模型；在前述模型的基础上，参考对流-弥散方程和胶体过滤模型，建立预测纳米/微米复合颗粒在多孔介质中运移的综合模型，通过土柱模拟和田间实验对前述模型进行验证。本项目研究结果可为土壤污染修复提供技术支持，为地下水污染防控提供理论基础和决策依据。

研究胶体在土壤等多孔介质中的运移是土壤学、环境工程和胶体与界面等学科的交叉研究方向。团聚是影响胶体在多孔介质中运移的关键因素之一，目前有关同种胶体所形成的团聚体的运移已有研究，关于不同种胶体团聚后所形成的复合颗粒的运移研究则还未见报道。本项目采用动态光散射法研究了纳米二氧化钛在初级势阱中的团聚和分散，阐明了纳米二氧化钛团聚体的粗糙表面是团聚体分散的关键因素；制备了片状微米蒙脱石表面负载一单层的纳米零价铁的复合颗粒土壤修复剂，并采用土柱模拟实验，研究了不同电解质溶液离子强度条件下，蒙脱石、纳米零价铁以及蒙脱石负载纳米零价铁胶体在饱和石英砂柱中的吸附、解吸和迁移，发现纳米微米复合结构可显著增强纳米零价铁在多孔介质中的迁移距离；采用蒙特卡洛方法模拟了纳米颗粒和微米颗粒团聚的模拟，提出了定量纳米颗粒和微米颗粒团聚速率的模型；通过设置饱和砂柱实验研究了水合排斥力和表面粗糙度对纳米/微米复合颗粒迁移的影响，发现纳米尺度粗糙凸起有利于复合颗粒的可逆吸附，水合排斥力的存在会进一步增强复合颗粒吸附的可逆性，而凹陷区域则有利于复合颗粒的不可逆吸附。项目研究结果对于污水处理和土壤污染防治具有重要的理论意义，并提供了技术支持。