R1 PM Nanotechnology Environmental Remediation, Fate, and Transport
Thursday, 17 November 2005: 1:50 PM - 5:30 PM in Ballroom 1

(GIL-1118-092655) The impact of aqueous colloid properties on the transport of metal oxide and sulfide nanoparticles.

Gilbert, B.¹, ¹ Lawrence Berkeley National Laboratory, Berkeley, CA, 94720

ABSTRACT- Nanoscale materials are likely to be employed in applications such as chemical catalysis, medical imaging and solar energy conversion that will carry a risk of eventual release into the environment. Furthermore, developing environmental remediation technologies either harness reactive nanoparticles or frequently lead to the precipitation of contaminants as nanoscale particles following microbial activity. The prediction of transport properties of novel nanoscale materials and of contaminants bound to or in the form of inorganic nanoparticles requires understanding of their colloid behavior. The goals of our research are (1) to determine the effects of particle size, surface adsorption and solution chemistry on the regime of colloid stability; (2) to determine the nano- and microscale structures of clusters that are formed when nanoparticles aggregate; and (3) to link aggregate structure to the kinetics of environmental transformations such as dissolution and aggregate transport properties. Metal oxide and metal sulfide nanoparticles represent two important nanomaterial classes, with distinct solution behavior. A combination of electron microscope imaging and in situ x-ray and light scattering studies has shown that iron oxyhydroxide, titanium dioxide and zinc sulfide nanoparticles exhibit a strong tendency to aggregate under environmentally relevant aqueous conditions. Thus, we predict that these nanomaterials will be transported as 20 - 1000 nm diameter pseudo-colloids with complex, and greatly varied interior structure. By using small-angle x-ray scattering to quantify the important aspects of aggregate structure we are developing models of the hydrodynamic and transport behavior of such aggregates for the interpretation of pore-scale transport experiments.

Key words: nanoparticles, colloids, fate