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The Kinetics of Zero Valent Iron Nanoparticle Oxidation in Oxygenated Water

Researchers from the Materials for Biological Environments Group have measured iron nanoparticle oxidation kinetics in a flowing water system, contributing to a better understanding of how iron nanoparticles might be used for the decontamination of water.

Pilot studies have demonstrated that iron nanoparticles can successfully degrade groundwater contaminants such as trichloroethylene, and there is increasing interest in using iron-based nanoparticles in drinking water and wastewater treatment to remove a wide variety of organic
and inorganic contaminants. When iron nanoparticles are in an aqueous environment, the metallic iron reacts with water and oxygen molecules and oxidizes to iron oxide.
During iron oxidation, reactants are produced that can chemically transform water contaminants through oxidative or reductive reactions. While there has been much work done to measure the kinetics of contaminant degradation in this system, there has been little work done to measure the kinetics of iron nanoparticle oxidation in water. Understanding the kinetics of iron nanoparticle
oxidation in water, however, is critical to optimizing nanoparticle design and lifetime.

Our team measured oxidation kinetics using a quartz crystal microbalance, where the change in sample mass, as a result of oxidation, was calculated based on the change in resonance frequency of the quartz crystal sample substrate. We demonstrated important effects of the nanoparticle surface coating and nanoparticle composition on the onset of, rate of, and extent of nanoparticle oxidation. Chelator-type surface coatings and the addition of nickel to the iron nanoparticles appear to significantly reduce the extent of nanoparticle oxidation. The results of this study indicate that nanoparticle lifetime can be extended based on an understanding of which material properties most affect oxidation.

This recently published work is the first to appear on this topic:  Kinetics of Zero Valent Iron Nanoparticle Oxidation in Oxygenated Water, Lauren Greenlee, Jessica Torrey, Robert Amaro, and Justin Shaw, Environmental Science & Technology 2012 46 (23), 12913-12920  (DOI: 10.1021/es303037k). CONTACT: Lauren Greenlee

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