HR: 09:45h
AN: B31F-07    [Abstracts]
TI: The Effect of Nanoparticle Aggregation Processes on Aggregate Structure and Metal Uptake
AU: * Gilbert, B
EM: BGilbert@lbl.gov
AF: Lawrence Berkeley National Laboratory, Earth Science Division, 1 Cyclotron Road, MS 90R1116, Berkeley, CA 94720, United States
AU: Ching, K A
EM: kaching@chapman.edu
AF: Chapman University, Department of Chemistry, One University Drive, Orange, CA 92866, United States
AU: Ono, R K
EM: rkono@chapman.edu
AF: Chapman University, Department of Chemistry, One University Drive, Orange, CA 92866, United States
AU: Kim, C S
EM: cskim@chapman.edu
AF: Chapman University, Department of Chemistry, One University Drive, Orange, CA 92866, United States
AB: Nanoscale oxide and oxyhydroxide minerals are commonly found in the natural environment, and play important roles in adsorbing and sequestering aqueous ions including nutrients such as phosphates and contaminants such as heavy metals. After formation, these materials are typically subjected to natural flocculation events that reduce the nanoparticle surface area that is accessible by aqueous ions. However, no studies have addressed the impact of different aggregation processes on the capacity of the nanoparticles to sorb aqueous metal ions. We synthesized a suspension of ~6 nm iron oxyhydroxide nanoparticles and subjected portions of this suspension to analogues of natural aggregation processes. These included: pH variation around the point of zero surface charge (simulating the neutralization of acid mine drainage); ionic strength elevation (simulating mixing of aquifer and saline water); drying; and freezing. The effect of aggregation on metal ion uptake was then studied by exposing batches of aggregated and control samples to 0.5 mM Cu(NO₃)₂ at pH 6.0 for 24 hours. In addition, we used in situ small-angle x-ray scattering to quantify and visualize the aggregate morphology. We found that the aggregates produced by the different mechanisms varied considerably in their interior porosity and their ability to sequester aqueous ions. In particular, the results demonstrate the important role of water in preserving hydrated channels among aggregated nanoparticles that are permeable to aqueous metal ions.
DE: 0418 Bioremediation
DE: 0461 Metals
DE: 1042 Mineral and crystal chemistry (3620)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting