Adsorptive-Reactive Nanoparticulate Systems for the In Situ Remediation of Chlorinated Hydrocarbons

Chlorinated hydrocarbons such as trichloroethylene (TCE) form a class of dense non-aqueous-phase liquid (DNAPL) toxic contaminants in soil and groundwater. The in situ injection of nanoscale zerovalent iron (NZVI) to reduce DNAPLs is a potentially simple, cost-effective, and environmentally benign technology that become a preferred method in the remediation of these compounds. However, unsupported NZVI particles exhibit ferromagnetism leading to particle aggregation and a loss in mobility through the subsurface. This work focuses on engineering submicron spherical carbon particles as effective carriers/supports for NZVI particles to address the in situ remediation of chlorinated hydrocarbons. We describe here a simple one-step process, demonstrating that it is possible to vary the placement of iron nanoparticles on carbon microspheres either on the surface of the microsphere or in the interior. These composites have high reactivities coupled with strong adsorption capabilities. The optimal size of these multifunctional particulate systems enables effective transport through sediments. The particulate systems are obtained from inexpensive precursors and through a semi-continuous method which allows for large scale synthesis of the composites necessary for eventual in-situ application. The detailed characterization of these multifunctional colloids through high resolution electron microscopy and their functional properties will be described. The mobility of these composites through model sediments using capillary and column transport experiments will be discussed.