HR: 0830h
AN: H51C-1074 [PDF]
TI: Factors Affecting the Reactivity, Efficiency, and Lifetime of Iron Nanoparticles for In Situ
Degradation of TCE
AU: * Lowry, G V
EM: glowry@cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave.
Department of Civil & Env. Eng., Pittsburgh, PA 15213 United States
AU: Liu, Y
EM: yueqiang@andrew.cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave.
Department of Civil & Env. Eng., Pittsburgh, PA 15213 United States
AU: Majetich, S
EM: sara@cmu.edu
AF: Carnegie Mellon University, 5000 Forbes Ave.
Department of Physics, Pittsburgh, PA 15213 United States
AB:
Over the past decade, laboratory and field studies have demonstrated that Fe$^{0}$ can rapidly transform dissolved
chlorinated organic solvents into non-toxic compounds. Using nanoscale Fe$^{0}$ (\~100nm particles) offers a host of novel
in situ subsurface remediation options because particles can be delivered into the small pores of porous media where residual
contamination resides. Using Fe$^{0}$ nanoparticles for in situ groundwater remediation is a recent nanotechnology
application and little is known about the optimal properties for these particles. The objective of this research is to
determine the factors controlling reactivity, lifetime, and efficiency of Fe$^{0}$ nanoparticles so more reactive and
efficient Fe$^{0}$ nanoparticles can be developed.
The physical and chemical properties of two types of Fe$^{0}$ nanoparticles; Fe$^{0}$ (AR-2, Toda America, Inc.) and
Boron-doped Fe$^{0}$ particles synthesized by NaBH$_{4}$ reduction of Fe$^{2+}$(aq) (Fe$^{0}$/B) were determined before and
after reaction with TCE in water using TEM, HRTEM, magnetometry, BET N$_{2}$ adsorption, electron diffraction, and ICP-AES.
The TCE transformation rate and efficiency (% of total Fe oxidized used to dechlorinate TCE) afforded by each type of
particle were measured. Under identical reaction conditions, Fe$^{0}$ nanoparticles (k$_{obs}$=0.013 Lg$^{-1}$d$^{-1}$) are
~2 orders of magnitude less reactive than boron-doped (Fe0/B) particles (k$_{obs}$=1.3 Lg$^{-1}$d$^{-1}$). The oxidized
surface of Fe$^{0}$ nanoparticles prevents them from corroding and limits the rate of TCE dechlorination. The presence of
boron appears to mitigate this effect. Although the Fe$^{0}$/B particles are highly reactive, HRTEM shows a clear core-shell
composition of these particles before reaction. Dissolution of the boron-containing oxide layer formed on the Fe$^{0}$/B
particles may be responsible for their higher reactivity. TEM indicates the presence of acicular 200nm by 15nm
a-Fe$_{2}$O$_{3}$ particles in Fe$^{0}$/B particles that have been fully reacted with TCE in water, suggesting that the
Fe-oxides formed away from the Fe$^{0}$/B particle surface. The efficiency of completely reacted Fe$^{0}$/B particles was
relatively low at ~10%. This indicates a tradeoff between reaction rate and efficiency, and suggests that optimal
Fe$^{0}$-based nanoparticles may not necessarily be those that afford the fastest dechlorination rates.
DE: 1045 Low-temperature geochemistry
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1884 Water supply
SC: Hydrology [H]
MN: 2003 Fall Meeting