Aggregation and transport of copper oxide nanoparticles in porous media.

In this study, microscopic aggregates of copper oxide (CuO) nanoparticles were visualized in porous media for the first time. Two-dimensional microscopic visualization results showed that CuO aggregates formed in porous media regardless of flow velocity. The results demonstrated that flow velocity determined the density and location of aggregate deposition in porous media. The lower the flow velocity, the greater the number of aggregates deposited, and the larger the area of deposition-that is, it was not limited to the pore neck. Transport of CuO nanoparticles was also evaluated by comparing breakthrough curves at three different flow velocities. The higher the Darcy flow velocity, the more the CuO nanoparticles are discharged from the porous medium, and the less deposited they are within the medium. Surfactants significantly affected the fate and transport of CuO nanoparticles in porous media. Most of the CuO nanoparticles present in the surfactant solution flowed through the porous medium, while only 30% of the nanoparticles in water flowed through the medium. However, the results also demonstrated that some CuO aggregates did form, even in the presence of a surfactant.