title: Effect of Structural Transformation of Nanoparticulate Zero-Valent Iron on Generation of Reactive Oxygen Species.
abstract: While it has been recognized for some time that addition of nanoparticlate zerovalent iron (nZVI) to oxygen-containing water results in both corrosion of Fe(0) and oxidation of contaminants, there is limited understanding of either the relationship between transformation of nZVI and oxidant formation or the factors controlling the lifetime and extent of oxidant production. Using Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, we show that while nZVI particles are transformed to ferrihydrite then lepidocrocite in less than 2 h, oxidant generation continues for up to 10 h. The major products (Fe(II) and H2O2) of the reaction of nZVI with oxygenated water are associated, for the most part, with the surface of particles present with these surface-associated Fenton reagents inducing oxidation of a target compound (in this study, (14)C-labeled formate). Effective oxidation of formate only occurred after formation of iron oxides on the nZVI surface with the initial formation of high surface area ferrihydrite facilitating rapid and extensive adsorption of formate with colocation of this target compound and surface-associated Fe(II) and H2O2 apparently critical to formate oxidation. Ongoing formate oxidation long after nZVI is consumed combined with the relatively slow consumption of Fe(II) and H2O2 suggest that these reactants are regenerated during the nZVI-initiated heterogeneous Fenton process.
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales , Sydney, New South Wales 2052, Australia.
authors.forename: Di
authors.initials: D
authors.lastname: He
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University , Shanghai 200092, People's Republic of China.
authors.forename: Jinxing
authors.initials: J
authors.lastname: Ma
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales , Sydney, New South Wales 2052, Australia.
authors.forename: Richard N
authors.initials: RN
authors.lastname: Collins
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales , Sydney, New South Wales 2052, Australia.
authors.forename: T David
authors.initials: TD
authors.lastname: Waite
mesh_terms: D000327:Adsorption; D005290:Ferric Compounds / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy
chemical_list: C045076:Fenton's reagent; D005290:Ferric Compounds; D016877:Oxidants; D017382:Reactive Oxygen Species; D014867:Water; C000499:ferric oxide; C092844:ferric oxyhydroxide; D006861:Hydrogen Peroxide; D007501:Iron; D010100:Oxygen