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Molecular Modeling of Ammonia Gas Adsorption onto the Kaolinite Surface with DFT Study

1
College of Earth and Planetary Science, University of Chinese Academy of Science, Beijing 100049, China
2
Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
3
College of Engineering, City University of Hong Kong, Hong Kong 999077, China
4
School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
*
Authors to whom correspondence should be addressed.
Minerals 2020, 10(1), 46; https://doi.org/10.3390/min10010046
Received: 25 November 2019 / Revised: 23 December 2019 / Accepted: 28 December 2019 / Published: 2 January 2020
(This article belongs to the Special Issue The Universal Application of Clay Minerals)
With high porosity and being one of the most abundant clay minerals, dried kaolinite may be an excellent adsorbent to remove ammonia gas (NH3). Here, the plane wave pseudopotential method based on density functional theory (DFT) was used to explore the mechanism of ammonia gas adsorption on the dried kaolinite, the Mulliken electric charge, and the partial density of states of atoms of the NH3/kaolinite (001) system. NH3 adsorption on kaolinite can happen in three different type adsorption positions: “top”, “bridge” and “hollow”. The “hollow” position is enclosed by two "upright" hydroxyl groups perpendicular to the (001) surface of kaolinite and a "lying" hydroxyl group parallel to the surface. At this position, the adsorption is the most stable and has the highest adsorption energy. The nitrogen atom of the NH3 molecule bonds with the hydrogen atom in the "upright" hydroxyl group on the (001) surface and its hydrogen atom forms HN…O hydrogen bond with oxygen atom in the "lying" hydroxyl group, which leads to the NH3 stably adsorbed on kaolinite (001) surface. A small part of electrons transfer between NH3 molecules and kaolinite creates weakly electrostatic adsorption between them. View Full-Text
Keywords: kaolinite; NH3; adsorption; density functional theory (DFT) kaolinite; NH3; adsorption; density functional theory (DFT)
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Cheng, Q.; Li, Y.; Qiao, X.; Guo, Y.; Zhao, Y.; Zhang, Q.; Ju, Y.; Shi, Y. Molecular Modeling of Ammonia Gas Adsorption onto the Kaolinite Surface with DFT Study. Minerals 2020, 10, 46.

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