Adsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study

Adsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study

The development of clay adsorption materials with high Cr(III) removal capacities requires an understanding of the adsorption mechanism at the atomic level. Herein, the mechanisms for the adsorption of Cr(OH)<sup>2+</sup>, Cr(OH)<sub>2</sub><sup>+</sup>, and Cr(OH...

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Autores principales: Jia Du, Leilei Fan, Qinghe Wang, Fanfei Min
Formato: article
Lenguaje:EN
Publicado: MDPI AG 2021
Materias:
DFT
adsorption mechanism
illite
hydroxyl chromium(III)
Chemical technology
TP1-1185
Chemistry
QD1-999
Acceso en línea:https://doaj.org/article/98ec1a72abfb432080f6eeadea0c957a
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spelling oai:doaj.org-article:98ec1a72abfb432080f6eeadea0c957a2021-11-25T18:51:47ZAdsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study10.3390/pr91120482227-9717https://doaj.org/article/98ec1a72abfb432080f6eeadea0c957a2021-11-01T00:00:00Zhttps://www.mdpi.com/2227-9717/9/11/2048https://doaj.org/toc/2227-9717The development of clay adsorption materials with high Cr(III) removal capacities requires an understanding of the adsorption mechanism at the atomic level. Herein, the mechanisms for the adsorption of Cr(OH)<sup>2+</sup>, Cr(OH)<sub>2</sub><sup>+</sup>, and Cr(OH)<sub>3</sub> on the (001) and (010) surfaces of illite were studied by analyzing the adsorption energies, adsorption configurations, charges, and state densities using density functional theory (DFT). The adsorption energies on the illite (010) and (001) surfaces decrease in the order: Cr(OH)<sup>2+</sup> > Cr(OH)<sub>2</sub><sup>+</sup> > Cr(OH)<sub>3</sub>. In addition, the energies associated with adsorption on the (010) surface are greater than those on the (001) surface. Further, the hydrolysates are highly active and can provide adsorption sites for desorption agents. The silica (Si–O) ring on the illite (001) surface can capture Cr(OH)<sub>n</sub><sup>(3</sup><sup>−</sup><sup>n)+</sup> (n = 1–3). In addition, both Cr(OH)<sup>2+</sup> and Cr(OH)<sub>2</sub><sup>+</sup> form one covalent bond between Cr and surface O<sub>S1</sub> (Cr–O<sub>S1</sub>), whereas the hydroxyl groups of Cr(OH)<sub>3</sub> form three hydrogen bonds with surface oxygens. However, increasing the number of hydroxyl groups in Cr(OH)<sub>n</sub><sup>(3</sup><sup>−</sup><sup>n)+</sup> weakens both the covalent and electrostatic interactions between the adsorbate and the (001) surface. In contrast, the Cr in all hydrolysates can form two covalent Cr–O<sub>Sn</sub> (n = 1–2) bonds to the oxygens on the illite (010) surface, in which Cr s and O p orbitals contribute to the bonding process. However, covalent interactions between the cation and the (010) surface are weakened as the number of hydroxyl groups in Cr(OH)<sub>n</sub><sup>(3−n)+</sup> increases. These results suggest that the illite interlayer can be stripped to expose Si–O rings, thereby increasing the number of adsorption sites. Furthermore, regulating the generated Cr(III) hydrolysate can increase or weaken adsorption on the illite surface. Based on these findings, conditions can be determined for improving the adsorption capacities and optimizing the regeneration performance of clay mineral materials.Jia DuLeilei FanQinghe WangFanfei MinMDPI AGarticleDFTadsorption mechanismillitehydroxyl chromium(III)Chemical technologyTP1-1185ChemistryQD1-999ENProcesses, Vol 9, Iss 2048, p 2048 (2021)
institution DOAJ
collection DOAJ
language EN
topic DFT
adsorption mechanism
illite
hydroxyl chromium(III)
Chemical technology
TP1-1185
Chemistry
QD1-999
spellingShingle DFT
adsorption mechanism
illite
hydroxyl chromium(III)
Chemical technology
TP1-1185
Chemistry
QD1-999
Jia Du
Leilei Fan
Qinghe Wang
Fanfei Min
Adsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study
description The development of clay adsorption materials with high Cr(III) removal capacities requires an understanding of the adsorption mechanism at the atomic level. Herein, the mechanisms for the adsorption of Cr(OH)<sup>2+</sup>, Cr(OH)<sub>2</sub><sup>+</sup>, and Cr(OH)<sub>3</sub> on the (001) and (010) surfaces of illite were studied by analyzing the adsorption energies, adsorption configurations, charges, and state densities using density functional theory (DFT). The adsorption energies on the illite (010) and (001) surfaces decrease in the order: Cr(OH)<sup>2+</sup> > Cr(OH)<sub>2</sub><sup>+</sup> > Cr(OH)<sub>3</sub>. In addition, the energies associated with adsorption on the (010) surface are greater than those on the (001) surface. Further, the hydrolysates are highly active and can provide adsorption sites for desorption agents. The silica (Si–O) ring on the illite (001) surface can capture Cr(OH)<sub>n</sub><sup>(3</sup><sup>−</sup><sup>n)+</sup> (n = 1–3). In addition, both Cr(OH)<sup>2+</sup> and Cr(OH)<sub>2</sub><sup>+</sup> form one covalent bond between Cr and surface O<sub>S1</sub> (Cr–O<sub>S1</sub>), whereas the hydroxyl groups of Cr(OH)<sub>3</sub> form three hydrogen bonds with surface oxygens. However, increasing the number of hydroxyl groups in Cr(OH)<sub>n</sub><sup>(3</sup><sup>−</sup><sup>n)+</sup> weakens both the covalent and electrostatic interactions between the adsorbate and the (001) surface. In contrast, the Cr in all hydrolysates can form two covalent Cr–O<sub>Sn</sub> (n = 1–2) bonds to the oxygens on the illite (010) surface, in which Cr s and O p orbitals contribute to the bonding process. However, covalent interactions between the cation and the (010) surface are weakened as the number of hydroxyl groups in Cr(OH)<sub>n</sub><sup>(3−n)+</sup> increases. These results suggest that the illite interlayer can be stripped to expose Si–O rings, thereby increasing the number of adsorption sites. Furthermore, regulating the generated Cr(III) hydrolysate can increase or weaken adsorption on the illite surface. Based on these findings, conditions can be determined for improving the adsorption capacities and optimizing the regeneration performance of clay mineral materials.
format article
author Jia Du
Leilei Fan
Qinghe Wang
Fanfei Min
author_facet Jia Du
Leilei Fan
Qinghe Wang
Fanfei Min
author_sort Jia Du
title Adsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study
title_short Adsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study
title_full Adsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study
title_fullStr Adsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study
title_full_unstemmed Adsorption of Cr(OH)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study
title_sort adsorption of cr(oh)<sub>n</sub><sup>(3−n)+</sup> (n = 1–3) on illite (001) and (010) surfaces: a dft study
publisher MDPI AG
publishDate 2021
url https://doaj.org/article/98ec1a72abfb432080f6eeadea0c957a
work_keys_str_mv AT jiadu adsorptionofcrohsubnsubsup3nsupn13onillite001and010surfacesadftstudy
AT leileifan adsorptionofcrohsubnsubsup3nsupn13onillite001and010surfacesadftstudy
AT qinghewang adsorptionofcrohsubnsubsup3nsupn13onillite001and010surfacesadftstudy
AT fanfeimin adsorptionofcrohsubnsubsup3nsupn13onillite001and010surfacesadftstudy
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