Facet-Dependent Cr(VI) Adsorption of Hematite Nanocrystals

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• 作者：Xiaopeng Huang ; Xiaojing Hou ; Fahui Song ; Jincai Zhao ; Lizhi Zhang
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：February 16, 2016
• 年：2016
• 卷：50
• 期：4
• 页码：1964-1972
• 全文大小：530K
• ISSN：1520-5851

文摘

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 C_3ν and C_2ν symmetry, while the C_3ν and C_2ν 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.