Kinetics of Zero Valent Iron Nanoparticle Oxidation in Oxygenated Water

Zero valent iron (ZVI) nanoparticles are versatile in their ability to remove a wide variety of water contaminants, and ZVI-based bimetallic nanoparticles show increased reactivity above that of ZVI alone. ZVI nanoparticles degrade contaminants through the reactive species (e.g., OH*, H2(g), H2O2) t...

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Bibliographic Details
Published in:Environmental science & technology 2012-12, Vol.46 (23), p.12913-12920
Main Authors: Greenlee, Lauren F, Torrey, Jessica D, Amaro, Robert L, Shaw, Justin M
Format: Article
Language:English
Subjects:
Applied sciences
Biological and physicochemical phenomena
Chemical reactions
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Exact sciences and technology
Iron
Iron - chemistry
Kinetics
Nanoparticles
Nanoparticles - chemistry
Nanoparticles - ultrastructure
Natural water pollution
Nickel - chemistry
Oxidation
Oxidation-Reduction
Pollution
Pollution, environment geology
Quartz
Solution chemistry
Water - chemistry
Water treatment and pollution
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Summary:Zero valent iron (ZVI) nanoparticles are versatile in their ability to remove a wide variety of water contaminants, and ZVI-based bimetallic nanoparticles show increased reactivity above that of ZVI alone. ZVI nanoparticles degrade contaminants through the reactive species (e.g., OH*, H2(g), H2O2) that are produced during iron oxidation. Measurement and modeling of aqueous ZVI nanoparticle oxidation kinetics are therefore necessary to optimize nanoparticle design. Stabilized ZVI and iron–nickel nanoparticles of approximately 150 nm in diameter were synthesized through solution chemistry, and nanoparticle oxidation kinetics were determined via measured mass change using a quartz crystal microbalance (QCM). Under flowing aerated water, ZVI nanoparticles had an initial exponential growth behavior indicating surface-dominated oxidation controlled by migration of species (H2O and O2) to the surface. A region of logarithmic growth followed the exponential growth which, based on the Mott-Cabrera model of thin oxide film growth, suggests a reaction dominated by movement of species (e.g., iron cations and oxygen anions) through the oxide layer. The presence of ethanol or a nickel shell on the ZVI nanoparticles delayed the onset of iron oxidation and reduced the extent of oxidation. In oxygenated water, ZVI nanoparticles oxidized primarily to the iron oxide-hydroxide lepidocrocite.
ISSN:0013-936X
1520-5851
DOI:10.1021/es303037k