title: Aging of Zerovalent Iron in Synthetic Groundwater: X-ray Photoelectron Spectroscopy Depth Profiling Characterization and Depassivation with Uniform Magnetic Field.
abstract: Scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) depth profiling were employed to characterize the aged zerovalent iron (AZVI) samples incubated in synthetic groundwater. The AZVI samples prepared under different conditions exhibited the passive layers of different morphologies, amounts, and constituents. Owing to the accumulation of iron oxides on their surface, all the prepared AZVI samples were much less reactive than the pristine ZVI for Se(IV) removal. However, the reactivity of all AZVI samples toward Se(IV) sequestration could be significantly enhanced by applying a uniform magnetic field (UMF). Moreover, the flux intensity of UMF necessary to depassivate an AZVI sample was strongly dependent on the properties of its passive layer. The UMF of 1 mT was strong enough to restore the reactivity of the AZVI samples with Fe3O4 as the major constituent of the passive film or with a thin layer of α-Fe2O3 and γ-FeOOH in the external passive film. The flux intensity of UMF necessary to depassivate the AZVI samples would increase to 2 mT or even 5 mT if the AZVI samples were covered with passive films being thicker, denser, and contained more γ-FeOOH and α-Fe2O3. Furthermore, increasing the flux intensity of UMF facilitated the reduction of Se(IV) to Se(0) by AZVI samples.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University , Shanghai 200092, P. R. China.
authors.forename: Hanyang
authors.initials: H
authors.lastname: Xu
authors.affiliation: School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology , Xi'an, Shaanxi 710055, P. R. China.
authors.forename: Yuankui
authors.initials: Y
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University , Shanghai 200092, P. R. China.
authors.forename: Jinxiang
authors.initials: J
authors.lastname: Li
authors.affiliation: Environmental Science and Engineering, Ocean University of China , Qingdao, Shandong 266100, P.R. China.
authors.forename: Fengmin
authors.initials: F
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University , Shanghai 200092, P. R. China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Guan
mesh_terms: D005290:Ferric Compounds; D060587:Groundwater; D007501:Iron / Q000737:chemistry*; D060526:Magnetic Fields; D056951:Photoelectron Spectroscopy; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; D007501:Iron