HR: 16:05h
AN: H54C-01 INVITED    [Abstracts]
TI: Controlled placement of polyelectrolyte modified engineered nanomaterials in the subsurface: Correlating modifier layer properties and geochemistry with mobility
AU: * Lowry, G
EM: glowry@cmu.edu
AF: Civil & Environmental Engineering; Chemical Engineering; Biomedical Engineering; Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, United States
AU: Phenrat, T
EM: tphenrat@andrew.cmu.edu
AF: Civil & Environmental Engineering; Chemical Engineering; Biomedical Engineering; Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, United States
AU: Fagerlund, F
EM: ffagerlu@mines.edu
AF: Center for Experimental Study of Subsurface Environmental Processes at Colorado School of Mines, 1500 Illinois St., Golden, CO 80401, United States
AU: Kim, H
EM: hyejink@andrew.cmu.edu
AF: Civil & Environmental Engineering; Chemical Engineering; Biomedical Engineering; Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, United States
AU: Illangasekare, T
EM: tillanga@mines.edu
AF: Center for Experimental Study of Subsurface Environmental Processes at Colorado School of Mines, 1500 Illinois St., Golden, CO 80401, United States
AU: Tilton, R
EM: tilton@andrew.cmu.edu
AF: Civil & Environmental Engineering; Chemical Engineering; Biomedical Engineering; Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, United States
AB: Nanoscale zerovalent iron (NZVI) particles are used for in situ remediation of contaminated groundwater. To be effective, NZVI must be reactive with target groundwater contaminants, and be mobile in the subsurface to enable placement. This is typically achieved with surface modification with polymers or surfactants. Concern over the potential toxicity of engineered nanomaterials is further motivation to understanding the factors controlling their mobility. Several hydrogeochemical properties control the mobility of nanoparticles in the subsurface including, the particle surface properties and polydispersity, groundwater geochemistry, the porewater velocity, and the grain size/type and the degree of sorting. Dynamic light scattering, sedimentation, and column transport studies were conducted on polyelectrolyte-modified NZVI under a variety of hydrogeochemical conditions, and with varying polydispersity, to determine the effect of each parameter on their mobility in water-saturated sand columns. It was shown that modifiers that provide electrosteric repulsion, which are less sensitive to changes in ionic strength, were needed to provide good mobility in saturated sand columns under geochemical conditions representative of groundwater conditions. At low particle concentration, mobility decreased with decreasing particle grain size, flow velocity, and in the presence of clay fines. This is consistent with colloid theory predictions. Mobility experiments conducted at high particle concentrations (1 to 6 g/L) and polydisperse samples, and at geochemical conditions relevant to particle injection (10 mM Na+, a pore water velocity of 3.2 x 10-4 m/s) showed that more polydisperse samples containing larger particles (several hundred nanometers) are less mobile than monodisperse samples containing only small particles (~100nm). The degree of deposition reversibility also decreased as polydispersity increases. Because the adsorbed layer properties and thus particle-collector interactions of polymer-modified NZVI are similar for all particle sizes used, the higher deposition rate of the polydisperse samples is attributed to increased aggregation from the magnetic attractive forces between particles which increase with r6. This study emphasizes an important role of geochemistry and particle-particle interaction (aggregation) in the transport of concentrated NZVI dispersions in porous media.
DE: 1832 Groundwater transport
DE: 4809 Colloids
SC: Hydrology [H]
MN: 2007 Fall Meeting