A comparative study of As(III) and As(V) in aqueous solutions and adsorbed on iron oxy-hydroxides by Raman spectroscopy |
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Authors: | Katharina Müller Virgínia ST Ciminelli Maria Sylvia S Dantas Sabine Willscher |
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Affiliation: | a Institute of Waste Management and Contaminated Site Treatment, Faculty of Forestry, Geosciences and Hydrology, Dresden University of Technology, Germany b Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais (UFMG), Avenida Antônio Carlos 6627, 30030-160 Belo Horizonte, MG, Brazil c National Institutes of Science and Technology: INCT-Acqua, Brazil |
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Abstract: | The sorption of the arsenite (AsO33−) and the arsenate (AsO43−) ions and their conjugate acids onto iron oxides is one of main processes controlling the distribution of arsenic in the environment. The present work intends to provide a large vibrational spectroscopic database for comparison of As(III) and As(V) speciation in aqueous solutions and at the iron oxide - solution interface. With this purpose, ferrihydrite, feroxyhyte, goethite and hematite were firstly synthesized, characterized in detail and used for adsorption experiments. Raman spectra were recorded from As(III) and As(V) aqueous solutions at various pH conditions selected in order to highlight arsenic speciation. Raman Scattering and Diffuse Reflectance Infrared Fourier Transform (DRIFT) studies were carried out to examine the respective As-bonding mechanisms. The collected data were curve-fitted and discussed according to molecular symmetry concepts. X-ray Absorption Near Edge Spectroscopy (XANES) was applied to confirm the oxidation state of the sorbed species. The comprehensive spectroscopic investigation contributes to a better understanding of arsenic complexation by iron oxides. |
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Keywords: | Arsenate Arsenite Adsorption Coprecipitation Iron oxy-hydroxides Raman spectroscopy Diffuse Reflectance Infrared Fourier Transform Spectroscopy X-ray Absorption Near Edge Spectroscopy |
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