title: Effect of emplaced nZVI mass and groundwater velocity on PCE dechlorination and hydrogen evolution in water-saturated sand.
abstract: The effect of nZVI mass loading and groundwater velocity on the tetrachloroethylene (PCE) dechlorination rate and the hydrogen evolution rate for poly(maleic acid-co-olefin) (MW=12K) coated nZVI was examined. In batch reactors, the PCE reaction rate constant (3.7×10-4Lhr-1m-2) and hydrogen evolution rate constant (1.4 nanomolLhr-1m-2) were independent of nZVI concentration above 10g/L, but the PCE dechlorination rate decreased and the hydrogen evolution rate increased for nZVI concentration below 10g/L. The nonlinearity between nZVI mass loading and PCE dechlorination and H2evolution was explained by differences in pH and Ehat each nZVI mass loading; PCE reactivity increased when solution Ehdecreased, and the H2evolution rate increased with decreasing pH. Thus, nZVI mass loading of <5g/L yields lower reactivity with PCE and lower efficiency of Fe° utilization than for higher nZVI mass loading. The PCE dechlorination rate increased with increasing pore-water velocity, suggesting that mass transfer limits the reaction at low porewater velocity. Overall, this work suggests that design of nZVI-based reactive barriers for groundwater treatment should consider the non-linear effects of both mass loading and flow velocity on performance and expected reactive lifetime.
authors.affiliation: Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA; Chemical Research Division, Environmental Health Research Department, National Institute of Environmental Research, Incheon 404-708, Republic of Korea.
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA; Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA.
authors.forename: Megan
authors.initials: M
authors.lastname: Leitch
authors.affiliation: Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA.
authors.forename: Bhanuphong
authors.initials: B
authors.lastname: Naknakorn
authors.affiliation: Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA; Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA; Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Tilton
authors.affiliation: Civil & Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA; Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA; Center for Environmental Implications of Nanotechnology, Carnegie Mellon University, Pittsburgh, PA 15213-3890, USA. Electronic address: glowry@cmu.edu.
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Lowry
keywords: DNAPL; Environmental nanotechnology; Groundwater treatment; In situ remediation; Nanoiron