Molecular Dynamics Simulation Study on Adsorption Characteristics of Illite for Hg<sup>2+</sup>
The Three Gorges Reservoir area of the Yangtze River has formed vast riverine fallout zones as a result of its periodic water storage and flood discharge operations, and the main constituents of this area are quaternary loose clays. It is important to study the microscopic characteristics of clay mi...
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MDPI AG
2023-09-01
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| Online Access: | https://www.mdpi.com/2073-4433/14/10/1503 |
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| author | Zhengchao Guo Biao Wang Xin Tang |
| author_facet | Zhengchao Guo Biao Wang Xin Tang |
| author_sort | Zhengchao Guo |
| collection | DOAJ |
| description | The Three Gorges Reservoir area of the Yangtze River has formed vast riverine fallout zones as a result of its periodic water storage and flood discharge operations, and the main constituents of this area are quaternary loose clays. It is important to study the microscopic characteristics of clay minerals in these fallout zones and their adsorption properties of Hg<sup>2+</sup> to guide the environmental safety of the fallout zones in the Three Gorges Reservoir area. In this context, the authors of this paper used X-ray diffraction (XRD) experiments to reveal the main clay mineral compositions in the fallout zones and then constructed the molecular model structures of the clay minerals based on molecular dynamics theory and studied the adsorption characteristics of these clay minerals with Hg<sup>2+</sup> in depth. The results show that the main clay minerals in the Three Gorges Reservoir area fallout zone include illite, illite-mixed layer and green-mixed layer, in which the content of illite ranges from 21% to 54%. Taking illite as the study object, the heat of adsorption of Hg<sup>2+</sup> in illite ranged from 14.83 kJ·mol<sup>−1</sup> to 31.92 kJ·mol<sup>−1</sup>, which is a physical adsorption. The heat of adsorption was mainly affected by the water content and had little relationship with temperature. With the gradual increase in water content, the heat of adsorption gradually decreases. The adsorption amount of Hg<sup>2+</sup>, on the other hand, is jointly affected by water content and temperature and decreases with the increase in water content and temperature; under natural environmental conditions (P = 0.1 Mpa), the adsorption characteristics of Hg<sup>2+</sup> in illite change with the change in water content. When the water content was between 0% and 6.95%, the increase in water content led to an increase in the interlayer spacing of illite, and the adsorption of Hg<sup>2+</sup> in illite was in a monolayer state, with the adsorption peaks located from 4.5~5.5 Å. When the water content increased to 6.95% to 13.90%, the layer spacing of illite reached the maximum, and the adsorption of Hg<sup>2+</sup> in illite transitioned from a monolayer to a bilayer, with the adsorption peaks located between 5 Å and 9~10 Å, respectively. When the water content was further increased to 13.90% to 20.85%, the increase in water content instead led to a slight decrease in the layer spacing of illite, showing a tendency of transitioning from a bilayer to a monolayer adsorption layer, which at the same time changed the number of adsorption layers of Hg<sup>2+</sup>; the study also revealed that the interaction between illite and Hg<sup>2+</sup> was regulated by van der Waals and Coulomb forces, whereas the increase in temperature promoted the Hg<sup>2+</sup> +diffusion, and an increase in water content inhibits the diffusion of Hg<sup>2+</sup>. In summary, these findings provide valuable theoretical support for solving the problem of Hg<sup>2+</sup> pollution in the Three Gorges Reservoir Decline Zone. |
| first_indexed | 2024-03-10T21:27:24Z |
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| last_indexed | 2024-03-10T21:27:24Z |
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| series | Atmosphere |
| spelling | doaj.art-5895f7b04f5c472d8c648961822bd0252023-11-19T15:35:56ZengMDPI AGAtmosphere2073-44332023-09-011410150310.3390/atmos14101503Molecular Dynamics Simulation Study on Adsorption Characteristics of Illite for Hg<sup>2+</sup>Zhengchao Guo0Biao Wang1Xin Tang2School of Civil Engineering, Chongqing Three Gorges University, Chongqing 404000, ChinaSchool of Civil Engineering, Chongqing Three Gorges University, Chongqing 404000, ChinaSchool of Civil Engineering, Chongqing Three Gorges University, Chongqing 404000, ChinaThe Three Gorges Reservoir area of the Yangtze River has formed vast riverine fallout zones as a result of its periodic water storage and flood discharge operations, and the main constituents of this area are quaternary loose clays. It is important to study the microscopic characteristics of clay minerals in these fallout zones and their adsorption properties of Hg<sup>2+</sup> to guide the environmental safety of the fallout zones in the Three Gorges Reservoir area. In this context, the authors of this paper used X-ray diffraction (XRD) experiments to reveal the main clay mineral compositions in the fallout zones and then constructed the molecular model structures of the clay minerals based on molecular dynamics theory and studied the adsorption characteristics of these clay minerals with Hg<sup>2+</sup> in depth. The results show that the main clay minerals in the Three Gorges Reservoir area fallout zone include illite, illite-mixed layer and green-mixed layer, in which the content of illite ranges from 21% to 54%. Taking illite as the study object, the heat of adsorption of Hg<sup>2+</sup> in illite ranged from 14.83 kJ·mol<sup>−1</sup> to 31.92 kJ·mol<sup>−1</sup>, which is a physical adsorption. The heat of adsorption was mainly affected by the water content and had little relationship with temperature. With the gradual increase in water content, the heat of adsorption gradually decreases. The adsorption amount of Hg<sup>2+</sup>, on the other hand, is jointly affected by water content and temperature and decreases with the increase in water content and temperature; under natural environmental conditions (P = 0.1 Mpa), the adsorption characteristics of Hg<sup>2+</sup> in illite change with the change in water content. When the water content was between 0% and 6.95%, the increase in water content led to an increase in the interlayer spacing of illite, and the adsorption of Hg<sup>2+</sup> in illite was in a monolayer state, with the adsorption peaks located from 4.5~5.5 Å. When the water content increased to 6.95% to 13.90%, the layer spacing of illite reached the maximum, and the adsorption of Hg<sup>2+</sup> in illite transitioned from a monolayer to a bilayer, with the adsorption peaks located between 5 Å and 9~10 Å, respectively. When the water content was further increased to 13.90% to 20.85%, the increase in water content instead led to a slight decrease in the layer spacing of illite, showing a tendency of transitioning from a bilayer to a monolayer adsorption layer, which at the same time changed the number of adsorption layers of Hg<sup>2+</sup>; the study also revealed that the interaction between illite and Hg<sup>2+</sup> was regulated by van der Waals and Coulomb forces, whereas the increase in temperature promoted the Hg<sup>2+</sup> +diffusion, and an increase in water content inhibits the diffusion of Hg<sup>2+</sup>. In summary, these findings provide valuable theoretical support for solving the problem of Hg<sup>2+</sup> pollution in the Three Gorges Reservoir Decline Zone.https://www.mdpi.com/2073-4433/14/10/1503water-level-fluctuating zonemolecular simulationilliteadsorptionHg<sup>2+</sup> |
| spellingShingle | Zhengchao Guo Biao Wang Xin Tang Molecular Dynamics Simulation Study on Adsorption Characteristics of Illite for Hg<sup>2+</sup> Atmosphere water-level-fluctuating zone molecular simulation illite adsorption Hg<sup>2+</sup> |
| title | Molecular Dynamics Simulation Study on Adsorption Characteristics of Illite for Hg<sup>2+</sup> |
| title_full | Molecular Dynamics Simulation Study on Adsorption Characteristics of Illite for Hg<sup>2+</sup> |
| title_fullStr | Molecular Dynamics Simulation Study on Adsorption Characteristics of Illite for Hg<sup>2+</sup> |
| title_full_unstemmed | Molecular Dynamics Simulation Study on Adsorption Characteristics of Illite for Hg<sup>2+</sup> |
| title_short | Molecular Dynamics Simulation Study on Adsorption Characteristics of Illite for Hg<sup>2+</sup> |
| title_sort | molecular dynamics simulation study on adsorption characteristics of illite for hg sup 2 sup |
| topic | water-level-fluctuating zone molecular simulation illite adsorption Hg<sup>2+</sup> |
| url | https://www.mdpi.com/2073-4433/14/10/1503 |
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