Mo/Fe3O4(111)表面对燃煤烟气汞吸附的密度泛函研究

利用CASTEP软件包采用密度泛函理论计算研究了过渡金属Mo掺杂Fe_3O_4(111)Fe_(tet)表面对Hg~0、HgCl和HgCl_2的吸附特征,分析了Mo掺杂前后Fe_3O_4(111)Fe_(tet)表面上不同汞物种的吸附形态。结果表明,Mo掺杂Fe_3O_4(111)Fe_(tet)表面对HgCl和HgCl_2为化学吸附,而对Hg~0的吸附为物理吸附;与纯净表面相比,HgCl在Mo原子掺杂表面上的吸附能提高了40%-66%。HgCl_2在纯净Fe_3O_4(111)Fe_(tet)表面形成"M"形结构;而掺杂Mo原子后,由于Cl原子与Mo原子之间更强的相互作用,使得HgCl_2发生了完全解离,两个Cl原子分别与Mo原子和Fe原子成键吸附在表面,Hg脱附。相关研究结果可为脱除燃煤烟气中的汞提供一定的理论指导。

A DFT study on the adsorption of various mercury species in the coal combustion flue gases on the Mo-doped Fe3O4(111) surface

The adsorption characteristics of Hg⁰, HgCl and HgCl₂ on the Mo-doped Fe₃O₄ (111) Fe_tet surface were investigated by density functional theory (DFT) calculation with the CASTEP software package. The results indicate that both HgCl and HgCl₂ are chemically adsorbed on the Mo-doped Fe₃O₄ (111) Fe_tet surface, whereas Hg⁰ is bound to the surface by physisorption. The binding energies of HgCl on the Mo-doped Fe₃O₄ (111) Fe_tet surface is about 40%-66% higher than that on the pure Fe₃O₄ (111) Fe_tet surface. For the adsorption of HgCl₂ molecule on the pure Fe₃O₄ (111) Fe_tet surface, two Cl atoms interact with one Mo atom and one Fe atom, forming the "M" structure; in contrast, on the Mo-doped Fe₃O₄ (111) Fe_tet surface, the stronger interaction between Cl atom and Mo atom allows a complete dissociation of HgCl₂ and release of Hg. The adsorption mechanism of mercury species on the Mo-doped Fe₃O₄ (111) Fe_tet surface revealed in this work may be helpful for the practical removal of mercury from coal-fired flue gases.