Chemical Transformations during Aging of Zerovalent Iron Nanoparticles in the Presence of Common Groundwater Dissolved Constituents
Title | Chemical Transformations during Aging of Zerovalent Iron Nanoparticles in the Presence of Common Groundwater Dissolved Constituents |
Publication Type | Journal Article |
Year of Publication | 2010 |
Authors | Reinsch, BC, Forsberg, B, Penn, RL, Kim, CS, Lowry, GV |
Journal | Environmental Science & Technology |
Volume | 44 |
Pagination | 3455-3461 |
Date Published | May |
Type of Article | Article |
ISBN Number | 0013-936X |
Accession Number | http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ResearchSoft&SrcApp=EndNote&DestLinkType=FullRecord&DestApp=WOS&KeyUT=000277067000043 |
Keywords | DEGRADATION, EDGE ABSORPTION-SPECTRA, FE MINERALS, H-2 EVOLUTION, MODEL COMPOUNDS, NANOMATERIALS, QUANTITATIVE SPECIATION, REACTIVE BARRIER, SPECTROSCOPY, TCE DECHLORINATION |
Abstract | Nanoscale zerovalent iron (NZVI) that was aged in simulated groundwater was evaluated for alterations in composition and speciation over 6 months to understand the possible transformations NZVI could undergo in natural waters. NZVI was exposed to 10 mN of various common groundwater anions (Cl-, NO3-, SO42-, HPO42-, and HCO3-) or to dissolved oxygen (saturated, similar to 9 mg/L). Fresh and exposed NZVI samples, along with Fe-oxide model compounds, were then analyzed using synchrotron radiation X-ray absorption spectroscopy (XAS) to yield both relative oxidation state, using the X-ray absorption near edge structure (XANES), and quantitative speciation information regarding the types and proportions of mineral species present, from analysis of the extended X-ray absorption fine structure (EXAFS). Over 1 month of aging the dissolved anions inhibited the oxidation of the NZVI to varying degrees. Aging for 6 months, however, resulted in average oxidation states that were similar to each other regardless of the anion used, except for nitrate. Nitrate passivated the NZVI surface such that even after 6 months of aging the particles retained nearly the same mineral and Fe-0 content as fresh NZVI. Linear least-squares combination fitting (LCF) of the EXAFS spectra for 1 month-aged samples indicated that the oxidized particles remain predominantly a binary phase system containing Fe-0 and Fe3O4, while the 6 month aged samples contained additional mineral phases such as vivianite (Fe-3(PO4)(2)center dot 8H(2)O) and iron sulfate species, possibly schwertmannite (Fe163+O16(OH,SO4)(12-13)center dot 10-12H(2)O). The presence of these additional mineral species was confirmed using synchrotron-based X-ray diffraction (XRD). NZVI exposed to water saturated with dissolved oxygen showed a rapid (<24 h) loss of Fe-0 and evolved both magnetite and maghemite (gamma-Fe2O3) within the oxide layer. These findings have implications toward the eventual fate, transport, and toxicity of NZVI used for groundwater remediation. |
URL | http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ResearchSoft&SrcApp=EndNote&DestLinkType=FullRecord&DestApp=WOS&KeyUT=000277067000043 |
Alternate Journal | Environ. Sci. Technol. |