Transport and Reactivity of Lactate-Modified Nanoscale Iron Particles for Remediation of DNT in Subsurface Soils

Nanoscale iron particles (NIP) can be used for in situ remediation of a variety of organic contaminants in the subsurface. NIP can effectively degrade contaminants due to their large reactive surface area. NIP transport in subsurface soils is hindered due to their agglomeration and sedimentation, and surface-modified NIP are suggested to enhance the transport. This study investigated the transport and reactivity of bare NIP and lactate-modified NIP (LMNIP) in field sand spiked with 2,4-dinitrotoluene (DNT at 740mg/kg), a representative nitroaromatic organic compound found at munitions waste sites. Column tests were conducted using NIP and LMNIP at two different concentrations (1 and 4g/L) and two different flow velocities (0.75 and 1.2cm/min). During the testing, changes in the magnetic susceptibility (MS) values across the soil column were measured and effluent was collected and its volume was measured at different time periods. After the end of the testing period, the soil was extruded and sectioned, and concentrations of iron (Fe) and DNT were measured in each soil section and effluent. Measured Fe concentrations in the soil and corresponding magnetic susceptibility were found to have a linear correlation. Therefore, the MS measurements made during the testing were used to assess the extent of transport of NIP and LMNIP at different times during the testing. The results showed that 4g/L LMNIP was transported more successfully than the 4g/L bare NIP, but there was no significant difference in the transport of NIP and LMNIP at the low concentration of 1g/L. As a result of the enhanced transport, 4g/L LMNIP caused greater degradation of the DNT. The higher flow rate increased the transport of NIP and LMNIP, thus increasing the DNT degradation.