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Stability and Transport of Cerium Oxide Nanoparticles in Aqueous Environment: Effect of pH, Ionic Strength, and Organic Matter.
Citation:
Lui, X., G. Chen, AND C. SU. Stability and Transport of Cerium Oxide Nanoparticles in Aqueous Environment: Effect of pH, Ionic Strength, and Organic Matter. Presented at Gordon Research Conference – Environmental Nanotechnology, Waterville Valley, NH, May 29 - June 03, 2011.
Impact/Purpose:
Presentation for Gordon Research Conference – Environmental Nanotechnology (May 29-June 3, 2011)
Description:
This study investigated the stability and transport of CeO2 NPs under the influence of pH, natural/manmade organic matter, and electrolyte (NaCl) concentrations. In column test, effluent concentration of CeO2 NPs was close to the influent at pH 10, while most NPs deposited on sand media at pH 4 and 7. Similar data were obtained at pH 4 and 10 in deposition test using quartz crystal microbalance with dissipation (QCM-D). However, the CeO2 NPs did not deposit on silica sensors at pH 7, because both NPs and sensors were negatively charged. On the contrary, the deposition of CeO2 on silica sand was observed at pH 7 in column test, which can be attributed to the favorable sites on sand media. In the deposition kinetics study using QCM-D, the reaction and diffusion controlled regimes were found at the original pH of CeO2 dispersion (pH 4.6), which is qualitatively consistent with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. In the presence organic matter (6 mg/L), including Suwanee River humic acid, fulvic acid, citric acid, alginate and carboxymethyl cellulose, more than 80 % of NPs was flushed out of column due to the electrosteric effect. The result of this study implies that although CeO2 NPs can deposit on porous media at near neutral pH, they could be mobilized greatly and transport to further distance in natural aqueous environment.