title: Facet-Dependent Cr(VI) Adsorption of Hematite Nanocrystals.
abstract: In this study, the adsorption process of Cr(VI) on the hematite facets was systematically investigated with synchrotron-based Cr K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, density-functional theory calculation, and surface complexation models. Structural model fitting of EXAFS spectroscopy suggested that the interatomic distances of Cr-Fe were, respectively, 3.61 Å for the chromate coordinated hematite nanoplates with exposed {001} facets, 3.60 and 3.30 Å for the chromate coordinated hematite nanorods with exposed {001} and {110} facets, which were characteristic of inner-sphere complexation. In situ ATR-FTIR spectroscopy analysis confirmed the presence of two inner-sphere surface complexes with C3ν and C2ν symmetry, while the C3ν and C2ν species were assigned to monodentate and bidentate inner-sphere surface complexes with average Cr-Fe interatomic distances of 3.60 and 3.30 Å, respectively. On the basis of these experimental and theoretical results, we concluded that HCrO4(-) as dominated Cr(VI) species was adsorbed on {001} and {110} facets in inner-sphere monodentate mononuclear and bidentate binuclear configurations, respectively. Moreover, the Cr(VI) adsorption performance of hematite facets was strongly dependent on the chromate complexes formed on the hematite facets.
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: Xiaopeng
authors.initials: X
authors.lastname: Huang
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: Xiaojing
authors.initials: X
authors.lastname: Hou
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: Fahui
authors.initials: F
authors.lastname: Song
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: Jincai
authors.initials: J
authors.lastname: Zhao
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: Lizhi
authors.initials: L
authors.lastname: Zhang
mesh_terms: D000327:Adsorption; D002840:Chromates / Q000737:chemistry; D002857:Chromium / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy; D014965:X-Rays
chemical_list: D002840:Chromates; D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; C000499:ferric oxide