磁性硅铁载铜吸附Hg0动力学机制及密度泛函研究

采用粉末冶金法将纳米单质铜(Cu⁰)、硅铁(FeSi)、四氧化三铁硅涂层(Fe₃O₄@SiO₂)混合煅烧并制备出新型磁性硅铁载铜吸附剂MagFeSi-Cu⁰。实验研究不同烟气温度下MagFeSi-Cu⁰的汞吸附能力基础上,结合颗粒内扩散模型、准二阶动力学模型、Elovich模型及Bangham模型分析了MagFeSi-Cu⁰吸附Hg⁰过程的主要控制步骤。在此基础上,依据密度泛函理论(DFT)研究了不同反应温度下FeSi表面Cu⁰原子与Hg⁰原子的汞齐作用机制。研究结果表明,Bangham模型的拟合值与MagFeSi-Cu⁰汞吸附实验值拟合度最高,MagFeSi-Cu⁰表面痕量Hg⁰吸附由汞的外扩散和表面铜汞齐吸附共同控制;通过密度泛函计算,发现Cu⁰颗粒表面Cu-Hg齐吸附能为-0.534 eV,当烟气温度从80℃上升至200℃时,Hg⁰原子与单质Cu原子的吸附自由能从-22.47 kJ/mol下降至-13.96 kJ/mol,这些结果为深入了解Hg⁰在Cu(111)表面的反应机理提供了理论基础。

Kinetic mechanism and density functional theory of Hg0 removal by Cu0-loaded magnetic Ferrosilicon

The FeSi,the nano-copper and the silica-coated magnetic Fe₃O₄ nano-particles were mixed and calcinated at 300℃by powder metallurgy method to prepare a novel magnetic sorbent(MagFeSi-Cu⁰).The intra-particle diffusion model,quasi-second-order kinetic model,Elovich model and Bangham model were used to analyze the control steps in the process of Hg⁰ removal.On this basis,according to density functional theory(DFT),the amalgam interaction mechanism of Cu⁰ atoms and Hg⁰ atoms on the FeSi surface at different reaction temperatures was studied.The research results showed that the fitting value of Bangham model and the experimental value of mercury adsorption was the highest.The adsorption of trace Hg⁰ on the surface of MagFeSi-Cu⁰ was controlled by the external diffusion and copper amalgam.In addition,it was found that the adsorption energy of Cu-Hg on the surface of Cu⁰ was-0.534 eV.When the temperature of flue gas rose from 80℃to 200℃,the adsorption energy of Hg⁰ dropped from-22.47 kJ/mol to-13.96kJ/mol.These results provide a theoretical basis for in-depth understanding of the reaction mechanism of Hg⁰ on Cu(111)surface.