HR: 08:30h
AN: U51C-02 [Abstracts]
TI: Kinetics of Reductive Dissolution: Influence of Nanoparticle Size and Aluminum Doping on Ferrihydrite Reactivity
AU: * Penn, R L
EM: penn@chem.umn.edu
AF: University of Minnesota, Department of Chemistry, 207 Pleasant St. SE, Minneapolis, MN
55455, United States
AU: Erbs, J J
EM: erbs@chem.umn.edu
AF: University of Minnesota, Department of Chemistry, 207 Pleasant St. SE, Minneapolis, MN
55455, United States
AU: Jentzsch, T L
EM: jentzsch@chem.umn.edu
AF: University of Minnesota, Department of Chemistry, 207 Pleasant St. SE, Minneapolis, MN
55455, United States
AB:
The composition and size of iron oxide nanoparticles in natural systems varies considerably. Here, we present
results examining the influence of size, and aluminum and arsenic doping on the redox reactivity of iron oxide
(ferrihydrite and magnetite) nanoparticles as determined from kinetic studies using either hydroquinone as a
reductant or benzoquinone as an oxidant. Variable-temperature experiments are used to determine activation
energies and frequency factors so as to quantitatively compare reactivities of the nanoparticles as a function of
varying composition and size. Results show that surface-area normalized rate constants for reductive dissolution
of ferrihydrite and for oxidation of magnetite decrease with increasing size. Interestingly, aluminum doping
results in increased reactivity in the ferrihydrite system whereas aluminum doping in the magnetite system
results in substantially depressed reactivity. Finally, variations in reactivity as a result of arsenic doping are
strongly dependent upon the preparation method. Ferrihydrite prepared by coprecipitation with arsenate exhibit
enhanced reactivity, while particles equilibrated with solutions containing arsenate exhibit decreased reactivity.
The impact of small changes in synthetic and storage procedures will also be specifically addressed.
DE: 1030 Geochemical cycles (0330)
DE: 1042 Mineral and crystal chemistry (3620)
SC: Union [U]
MN: 2007 Joint Assembly