ENVR 172 |
| Reactive Fe0/Fe-oxide nanoparticles are surface modified with polyelectrolytes to enhance colloidal stability and mobility in the subsurface. In the environment, these nanoparticles further interact with natural organic matter (NOM). A mechanistic understanding of how adsorbed polyelectrolyte and NOM affect their reactivity is not available. The objectives of this study are to determine the reasons for the decreased surface reactivity for TCE dechlorination upon adsorption of polyelectrolyte and/or humic acid. The TCE dechlorination rate is systematically measured as a function of the adsorbed mass of polyelectrolyte and humic acid. The layer thickness of the sorbed polyelectrolytes is estimated by Ohshima's soft particle analysis and the partitioning coefficient of TCE onto each polyelectrolyte is measured. These data and Scheutjens-Fleer theory for polymer adsorption indicate that reactivity loss at low adsorbed mass is from reactive site blocking at points of polyelectrolyte attachment and that mass transfer resistance in the polyelectrolyte brush is significant at higher adsorbed mass of polyelectrolyte where an extended brush conformation develops. This conceptual model explains the decrease in the observed TCE dechlorination rate constant for both adsorbed polyelectrolytes and humic acid on Fe0/Fe-oxide nanoparticles. |
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Advances in Abiotic Transformation Processes for Micropollutants in Drinking Water and for Sourcewater Protection
8:30 AM-12:10 PM, Wednesday, April 9, 2008 Morial Convention Center -- Rm. 237, Oral
Division of Environmental Chemistry |