Microwave-hydrothermal synthesis of nanostructured Na-birnessites and phase transformation by arsenic(III) oxidation
- Departamento de Quimica, Universidade Federal de Ouro Preto, 35400-000 Ouro Preto, MG (Brazil)
- DEMET, UFMG, Rua Espirito Santo 35, Sala 206, 30160-030 Belo Horizonte, MG (Brazil)
Microwave-hydrothermal synthesis was employed to produce Na-birnessites. Crystalline, single-phase materials were obtained at temperatures as low as 120 deg. C and times as short as 1 min. X-ray diffraction and Raman spectroscopy were used to characterize the structural features of the nanostructured powders. Birnessites possessed a monoclinic structure in space group C2/m with nine Raman-active bands, all of which were observed for the first time due to optimized acquisition of the spectroscopic data. The highly reactive materials produced were submitted to sorption experiments with As(III). An oxidative precipitation occurred with the production of Mn(II) arsenate at higher arsenic concentrations. In addition, the formation of hausmannite (Mn{sub 3}O{sub 4}) was confirmed by X-ray diffraction and Raman analyses of the reacted solid phase. The observed 14 Raman-active modes were adjusted according to the tetragonal I4{sub 1}/amd space group for hausmannite. An additional band related to the breathing mode of the arsenate was observed, leading to the conclusion that adsorption onto hausmannite takes place in addition to the oxidative precipitation of manganese arsenate.
- OSTI ID:
- 21144026
- Journal Information:
- Materials Research Bulletin, Vol. 43, Issue 6; Other Information: DOI: 10.1016/j.materresbull.2007.06.019; PII: S0025-5408(07)00260-7; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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