DFT study of the effect of impurity defects on the inner-layer adsorption of hydrated Al(OH)2+ on the kaolinite (001) surface
DFT study of the effect of impurity defects on the inner-layer adsorption of hydrated Al(OH)2+ on the kaolinite (001) surface
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DOI：
10.1016/j.molliq.2022.120819
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发表时间：
2022-11
影响因子：
6
通讯作者：
Yuqi Miao;Huashan Yan;Bengen Hong;Xiaowen Zhou;Lichao Tong;Yanfei Xiao;S. Qiu;Bin Yang
中科院分区：
文献类型：
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作者：
Yuqi Miao;Huashan Yan;Bengen Hong;Xiaowen Zhou;Lichao Tong;Yanfei Xiao;S. Qiu;Bin Yang
杂质缺陷普遍存在于高岭石表面。用密度泛函理论(DFT)研究了Al~(3+)在高岭石(0，0，1)理想表面和掺杂高岭石(0，0，1)表面的吸附机理，以及镁、钙、铁三种常见杂质缺陷对表面性质的影响。此外，还比较了范德华力和有效库仑斥力对密度泛函计算结果的影响。结果表明，Al(OH)2+的稳定水化构型为Al(OH)2(H2O)4+。水合Al(OH)2+倾向于吸附在OTSite上，Al-Osare充满成键轨道。与理想高岭石表面相比，掺镁高岭石表面更容易吸附水合Al(OH)2+。镁和钙掺杂提高了表面氧原子的活性，使水合Al(OH)2+更容易吸附在表面，而铁掺杂降低了表面氧原子的活性。范德华力对表面性质和吸附构型影响不大。由于有效库仑斥力参数U考虑了铁原子上具有相反自旋的局域电子之间的库仑斥力，因此可以更准确地描述铁掺杂体系。研究结果揭示了掺杂后高岭石表面性质的变化及杂质铝在掺杂高岭石表面的吸附机理，为开发高效离子稀土矿石浸取剂提供了参考。
Impurity defects are ubiquitous on the kaolinite surface. Density functional theory (DFT) was used to study the adsorption mechanism of Al3+dihydroxy hydrate on ideal and impurity-doped kaolinite (0 0 1) Al-OH surfaces, and the influence of three common impurity defects, namely Mg, Ca, and Fe, on the surface properties. In addition, the effects of van der Waals forces and effective Coulomb repulsion on DFT calculations results are compared. The results show that the stable hydration configuration of Al(OH)2+is Al(OH)2(H2O)4+. Hydrated Al(OH)2+tends to be adsorbed at the Otsite and Al-Osare filled with bonding orbitals. Compared with the ideal kaolinite surface, hydrated Al(OH)2+is more easily adsorbed on the Mg-doped surface. Mg and Ca doping enhanced the activity of surface O atoms and made the hydrated Al(OH)2+more easily adsorbed on the surface, while Fe doping decreased the activity of surface O atoms. The van der Waals force has little effect on the surface properties and adsorption configuration. Since the effective Coulomb repulsion parameter U takes into account the Coulomb repulsion between local electrons with opposite spins on the Fe atom, the Fe-doped system can be described more accurately. The research results reveal the change of properties of kaolinite surface after doping and the adsorption mechanism of impurity Al on the doped kaolinite surface, which provides a reference for the development of high-efficiency ionic rare earth ore leaching agent.