title: Negative impact of oxygen molecular activation on Cr(VI) removal with core-shell Fe@Fe2O3 nanowires.
abstract: In this study, we demonstrate that the presence of oxygen molecule can inhibit Cr(VI) removal with core-shell Fe@Fe2O3 nanowires at neutral pH of 6.1. 100% of Cr(VI) removal was achieved by the Fe@Fe2O3 nanowires within 60 min in the anoxic condition, in contrast, only 81.2% of Cr(VI) was sequestrated in the oxic condition. Removal kinetics analysis indicated that the presence of oxygen could inhibit the Cr(VI) removal efficiency by near 3 times. XRD, SEM, and XPS analysis revealed that either the anoxic or oxic Cr(VI) removal was involved with adsorption, reduction, co-precipitation, and re-adsorption processes. More Cr(VI) was bound in a reduced state of Cr(III) in the anoxic process, while a thicker Cr(III)/Fe(III)/Cr(VI) oxyhydroxides shell, leading to inhibiting the electron transfer, was found under the oxic process. The negative impact of oxygen molecule was attributed to the oxygen molecular activation which competed with Cr(VI) adsorbed for the consumption of donor electrons from Fe(0) core and ferrous ions bound on the iron oxides surface under the oxic condition. This study sheds light on the understanding of the fate and transport of Cr(VI) in oxic and anoxic environment, as well provides helpful guide for optimizing Cr(VI) removal conditions in real applications.
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University, Wuhan 430079, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Mu
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University, Wuhan 430079, People's Republic of China.
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry, Central China Normal University, Wuhan 430079, People's Republic of China. Electronic address: jennifer.ai@mail.ccnu.edu.cn.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Ai
mesh_terms: D002857:Chromium / Q000302:isolation & purification*; D005296:Ferrous Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D053770:Nanowires / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification
chemical_list: D005296:Ferrous Compounds; D007202:Indicators and Reagents; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; C034236:ferrous oxide; D010100:Oxygen
keywords: Cr(VI); Fe@Fe(2)O(3) core–shell nanowires; Molecular oxygen activation; Removal