Shen Peng, Wu Sikai, Hu Chen, Cheng Zhihai, Wu Jiang, Luo Guangqian, Yao Hong, Mao Xu, Song Mao, Yang Xiaolian
College of Energy and Mechanical Engineering, Shanghai University of Electric Power, Shanghai, 200090, China.
College of Energy and Mechanical Engineering, Shanghai University of Electric Power, Shanghai, 200090, China.
J Mol Graph Model. 2023 Jan;118:108357. doi: 10.1016/j.jmgm.2022.108357. Epub 2022 Oct 7.
CaSiO is highly resistant to sintering and can trap arsenic at high temperatures in the boiler furnace. However, the trapping capacity of CaSiO for arsenic does not meet the requirements of practical applications, and it is easy to react with acidic gases, which significantly affects the adsorptive property of arsenic. In this paper, the effect of Al modification on the AsO adsorption behaviour on the CaSiO(001) surface was systematically investigated using a density functional theory. By comparing the magnitude of adsorption energy of different sites, the active site of AsO adsorbed on the surface of CaSiO(001) was determined to be Ca, and the adsorption activity of AsO by the silicon oxygen chain composed of [SiO] tetrahedron is deficient. The Si atoms in the [SiO] tetrahedral structure are directly replaced by Al atoms, the difference in bond length and bond energy between Al-O bond and Si-O bond is used to promote the redistribution of surface charge and the increase of local structural bond angle of CaSiO(001), leading to the exposure of new active sites (Si-top and Al-top sites) on the silicon oxygen chain. The new active site can realize the chemical adsorption of AsO, the higher adsorption energy of the Al-top site is attributed to the stronger s-p orbital hybridization between Al and O atoms after doping, which is more conducive to the charge transfer between AsO and the adsorbent surface. In this work, influence of SO and HCl gases on the adsorption of AsO by modified silicon oxygen chains was also discussed. The results show that SO and HCl in the flue gas may occupy the Al-top site on the silicon oxygen chain through chemical adsorption, and reduce the activity of this site, thereby affecting the adsorption of AsO. However, the exposed Si-top sites owing to Al doping show good acidic gas resistance, which in turn help the surface of Al-CaSiO(001) can also maintain stable adsorption of AsO in SO and HCl atmosphere.
硅酸钙对烧结具有高度抗性，并且在锅炉炉膛的高温下能够捕获砷。然而，硅酸钙对砷的捕获能力不符合实际应用的要求，并且它容易与酸性气体发生反应，这显著影响了砷的吸附性能。在本文中，使用密度泛函理论系统地研究了Al改性对CaSiO(001)表面上AsO吸附行为的影响。通过比较不同位点的吸附能大小，确定吸附在CaSiO(001)表面上的AsO的活性位点为Ca，并且由[SiO]四面体组成的硅氧链对AsO的吸附活性不足。[SiO]四面体结构中的Si原子被Al原子直接取代，利用Al-O键和Si-O键之间的键长和键能差异来促进表面电荷的重新分布以及CaSiO(001)局部结构键角的增加，导致硅氧链上出现新的活性位点（Si-top和Al-top位点）。新的活性位点能够实现AsO的化学吸附，Al-top位点较高的吸附能归因于掺杂后Al与O原子之间更强的s-p轨道杂化，这更有利于AsO与吸附剂表面之间的电荷转移。在这项工作中，还讨论了SO和HCl气体对改性硅氧链吸附AsO的影响。结果表明，烟气中的SO和HCl可能通过化学吸附占据硅氧链上的Al-top位点，并降低该位点的活性，从而影响AsO的吸附。然而，由于Al掺杂而暴露的Si-top位点表现出良好的抗酸性气体能力，这反过来有助于Al-CaSiO(001)表面在SO和HCl气氛中也能保持对AsO的稳定吸附。
