X-ray absorption spectroscopy study of the electronic and structural properties of hexavalent chromium adsorbed by volcanic ashes
•The volcanic ash from the Cameroon volcanic line of Mount Cameroon volcano can be used as a potential economically sustainable adsorbent for removing hexavalent chromium pollutant from wastewater.•The oxidation state of Cr(VI) after being adsorbed by the volcanic ash has changed into the trivalent...
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Veröffentlicht in: | Journal of molecular structure 2023-12, Vol.1294, p.136453, Article 136453 |
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Sprache: | eng |
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Zusammenfassung: | •The volcanic ash from the Cameroon volcanic line of Mount Cameroon volcano can be used as a potential economically sustainable adsorbent for removing hexavalent chromium pollutant from wastewater.•The oxidation state of Cr(VI) after being adsorbed by the volcanic ash has changed into the trivalent chromium oxidation state. This suggests that the most components in the volcanic ash material are chromium compounds in the oxidation state (III).•Chromium adsorbed by volcanic ash sample is mainly composed of Cr2O3, FeCr2O4 and Na2Cr2O7.•The chromium sorption occurred mainly by ion-exchange implying the chemical reduction of Cr(VI) into Cr(III).•In the chromium adsorbed by volcanic ash sample, the first and second shells are coordinated with oxygen and chromium atoms respectively.
X-ray absorption spectroscopy (XAS) was used to characterize the volcanic ash (VA) materials as a low-cost and natural environmental adsorbent for the sorption of Cr (VI). The batch adsorption method was employed to synthesize the sample of chromium (VI) sorbed by VA. The results showed that the Cr-VA material is in the chromium oxidation state (III) and can be described as a composition of Cr2O3 (47.9%), FeCr2O4 (45.2%), and Na2Cr2O7 (6.9%). The promotion of the 1s Cr core electron implies the electronic transitions 1s to 3d(t2g) and 1s to 3d(eg). The first and second shells in the Cr-VA material were coordinated with the oxygen and chromium atoms in a distorted geometrical arrangement. The adsorption mechanism was associated with the chemical reduction of Cr (VI) to Cr (III) via an ion-exchange process. The XAS technique significantly contributes to the characterization of environmental VA, which can be proposed as an economical and alternative adsorbent for the sorption of Cr from contaminated wastewater. |
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ISSN: | 0022-2860 1872-8014 |
DOI: | 10.1016/j.molstruc.2023.136453 |