Transport of Lactate-Modified Nanoscale Iron Particles in Porous Media

Nanoscale iron particles (NIPs) have recently been shown to be effective for dehalogenation of recalcitrant organic contaminants such as pentachlorophenol and dinitrotoluene in the environment. However, the effective transport of NIPs into the contaminated subsurface zosnes is crucial for the success of in situ remediation. Previous studies have shown that the transport of NIPs in soils is very limited and surface modification of NIPs is required to achieve adequate transport. This paper investigates the transport of lactate-modified NIPs (LMNIPs) through four different sand porous media. A series of laboratory column experiments was conducted to quantify the transport of bare NIPs and LMNIPs at two slurry concentrations, 1and4g/L, under two flow velocities. The NIPs used in this study possessed magnetic properties; thus, a magnetic susceptibility sensor system was used to monitor the changes in magnetic susceptibility (MS) along the length of the column at different times during the experiments. At the end of testing, the distribution of total Fe in the sand column was measured. Results showed a linear correlation between the Fe concentration and MS, and that was used to assess the transport of NIPs and LMNIPs in the sand columns. Results showed that LMNIPs transported better than the bare NIPs, and a higher concentration of 4g/L LMNIPs exhibited uniform and greater transport compared with other test conditions. Transport of NIPs increased in the following order: coarse Ottawa sand>coarse field sand>medium field sand>fine Ottawa sand. Filtration theory and the advective-dispersion equation with reaction were applied and able to reasonably capture the transport behavior of NIPs and LMNIPs in the sand columns.