title: New Insight into the Local Structure of Hydrous Ferric Arsenate Using Full-Potential Multiple Scattering Analysis, Density Functional Theory Calculations, and Vibrational Spectroscopy.
abstract: Hydrous ferric arsenate (HFA) is an important arsenic-bearing precipitate in the mining-impacted environment and hydrometallurgical tailings. However, there is no agreement on its local atomic structure. The local structure of HFA was reprobed by employing a full-potential multiple scattering (FPMS) analysis, density functional theory (DFT) calculations, and vibrational spectroscopy. The FPMS simulations indicated that the coordination number of the As-Fe, Fe-As, or both in HFA was approximately two. The DFT calculations constructed a structure of HFA with the formula of Fe(HAsO4)x(H2AsO4)1-x(OH)y·zH2O. The presence of protonated arsenate in HFA was also evidenced by vibrational spectroscopy. The As and Fe K-edge X-ray absorption near-edge structure spectra of HFA were accurately reproduced by FPMS simulations using the chain structure, which was also a reasonable model for extended X-Ray absorption fine structure fitting. The FPMS refinements indicated that the interatomic Fe-Fe distance was approximately 5.2 Å, consistent with that obtained by Mikutta et al. (Environ. Sci. Technol. 2013, 47 (7), 3122-3131) using wavelet analysis. All of the results suggested that HFA was more likely to occur as a chain with AsO4tetrahedra and FeO6octahedra connecting alternately in an isolated bidentate-type fashion. This finding is of significance for understanding the fate of arsenic and the formation of ferric arsenate minerals in an acidic environment.
authors: Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences , Shenyang 110016, China.
authors: Shaofeng
authors: S
authors: Wang
authors: Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences , Shenyang 110016, China.
authors: Xu
authors: X
authors: Ma
authors: Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences , Shenyang 110016, China.
authors: Guoqing
authors: G
authors: Zhang
authors: Institute of Environmental Protection, Shenyang University of Chemical Technology , Shenyang 110142, China.
authors: Yongfeng
authors: Y
authors: Jia
authors: Département Matériaux Nanosciences, Institut de Physique de Rennes , UMR UR1-CNRS 6251, Université de Rennes 1, 35042 Rennes Cedex, France.
authors: Keisuke
authors: K
authors: Hatada
mesh_terms: D001149:Arsenates / Q000737:chemistry*; D001151:Arsenic; D005290:Ferric Compounds / Q000737:chemistry*; D013057:Spectrum Analysis; D056928:X-Ray Absorption Spectroscopy; D014965:X-Rays
chemical_list: D001149:Arsenates; D005290:Ferric Compounds; D001151:Arsenic