Theoretical investigation of hydrated [Lu(OH)2]+ adsorption on kaolinite (001) surface with DFT calculations
Theoretical investigation of hydrated [Lu(OH)2]+ adsorption on kaolinite (001) surface with DFT calculations
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DOI：
10.1016/j.apsusc.2021.150473
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发表时间：
2021-07-08
影响因子：
6.7
通讯作者：
Qiu, Tingsheng
中科院分区：
文献类型：
--
作者：
Qiu, Sen;Wu, Hao;Qiu, Tingsheng
高岭石是离子吸附稀土矿石中的主要矿物，也是钚(Lu)的主要来源。在这些矿石中，Lu主要以水合或羟基水合离子的形式吸附在高岭石表面，因此可以通过离子交换浸出解吸。用密度泛函理论方法研究了水合[Lu(OH)2]+离子在高岭石(001)表面的吸附机理和成键性质。Lu3+呈定向倾向几何构型，配位数高达9。吸附模型以水体系中最稳定的离子[Lu(OH)2(H2O)6]+为初始结构。为了研究水合[Lu(OH)2]+与高岭石表面的结合，采用了外层(与氢键相关)和内层(与配位键相关)吸附模型。研究了去质子化Al-OH表面的表面电荷和HOMO分布。由于去质子化的羟基具有很高的反应性，其内层吸附以Lu与表面氧之间的配位键为主，其中Ol位的双齿配位吸附能最大(-663.86 kJ/m ol)。此外，态投影和Mulliken键布居的偏密度表明，Lu 5d和Os 2p的反键结合是Lu和表面氧的主要轨道贡献。这些对Lu吸附机理的洞察有助于开发改进的离子交换浸出技术。
Kaolinite is a major mineral present in ion-adsorption rare earth ores, which are the primary source of lutetium (Lu). In those ores, Lu is mainly found to be adsorbed on the kaolinite surface in the form of hydrated or hydroxyl-hydrated ions, and can therefore be desorbed by ion-exchange leaching. This study used density functional theory calculations to investigate the adsorption mechanisms and bonding nature of hydrated [Lu (OH)2]+ ions on the kaolinite (0 0 1) surface. Lu3+ exhibited directed tendency geometry with high coordination number of nine. [Lu(OH)2(H2O)6]+, the most stable ion in aqueous system, was considered as the initial structure for the adsorption models. To investigate bonding between hydrated [Lu(OH)2]+ and the kaolinite surface, outerlayer (related to hydrogen bonding) and inner-layer (related to coordination bonding) adsorption models were applied. The surface charge and HOMO distribution of the deprotonated Al-OH surface were also investigated. Owing to the high reactivity of the deprotonated hydroxyls, inner-layer adsorption was dominated by coordination bonds between Lu and surface oxygen, with bidentate complexation at Ol site giving the largest adsorption energy (-663.86 kJ/mol). Moreover, partial density of state projections and Mulliken bond populations showed that the antibonding combination of Lu 5d and Os 2p is the dominant orbital contribution of Lu and surface oxygen. These insights into the Lu adsorption mechanism can aid in developing improved ion-exchange leaching techniques.