Defects induced by Al substitution enhance As(V) adsorption on ferrihydrites
| Autor: | Erico T.F. Freitas, Nelcy D. S. Mohallem, Virginia S.T. Ciminelli, Taiane G. F. Souza |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Langmuir
Environmental Engineering Health Toxicology and Mutagenesis Inorganic chemistry 0211 other engineering and technologies chemistry.chemical_element 02 engineering and technology 010501 environmental sciences 01 natural sciences Ferric Compounds Arsenic Ferrihydrite Adsorption X-ray photoelectron spectroscopy Environmental Chemistry Spectroscopy Waste Management and Disposal 0105 earth and related environmental sciences 021110 strategic defence & security studies Hydrogen-Ion Concentration Pollution chemistry Electron diffraction Selected area diffraction Aluminum |
| Zdroj: | Journal of hazardous materials. 420 |
| ISSN: | 1873-3336 |
| Popis: | An original rationale is proposed to explain the controversial role of aluminum, a common substitutive element in ferrihydrite (Fh), on arsenic adsorption. The adsorption of arsenic on synthetic Al-for-Fe substituted Fh (AlFh) with up to 20 mol% Al was investigated at pH 5 and 8. The reduced interplanar spacings observed by selected area electron diffraction show that all AlFh samples are isomorphically substituted up to 20 mol% Al. A 15 mol% Al incorporation increases the arsenic uptake by 28%. In contrast, the Langmuir binding constants decrease, suggesting weaker bonds. Arsenic uptake reduces by 50% as pH rises from 5 to 8. The Al-for-Fe substitution in ferrihydrite causes structural defects, proton-compensated by OH groups, as indicated by the Vegard rule deviation. X-ray photoelectron spectroscopy demonstrates the increase in the relative amount of surface M-OH sites (45% to 77%) with Al concentration (AlFh-0 to AlFh-20), respectively. The enhanced As(V) uptake was ascribed to the insertion of hydroxyls on the Fh structural defects. Fourier-transformed-infrared spectroscopy showed that the sites modified by Al introduction are involved in As adsorption. These findings help to understand aluminum's role in arsenic adsorption, fixation, and fate in the environment. |
| Databáze: | OpenAIRE |
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