飞灰中活性SiO2吸附痕量元素汞的DFT研究

DFT Study on Adsorption Mechanism of Trace Element Mercury by Active SiO2 in Fly Ash

为探究痕量元素汞在飞灰中的富集特性,利用密度泛函理论(DFT)研究了Hg0和HgCl在飞灰中的主要活性成分SiO2表面上的吸附机理,对优化后的吸附构型进行能量计算、AIM理论和Mayer键级分析,并利用定域化分子轨道(LMO)图分析相互作用类型。结果表明:Hg0在无定型SiO2表面缺陷位的吸附能均小于50 kJ/mol,为较弱的物理吸附;HgCl在无定型SiO2表面缺陷位的吸附能均远大于50 kJ/mol,吸附构型均为典型的化学吸附,且SiO2-HgCl为共价键相互作用。

To study the enrichment characteristics of trace element mercury in fly ash, the adsorption mechanism of elemental mercury Hg0 and oxidized mercury HgCl by active SiO2 in fly ash was studied by density functional theory(DFT). The adsorption configuration was studied through energy calculation, AIM theory analysis and Mayer bond analysis, while the interaction type was analyzed using localized molecular orbital(LMO) map. Results show that the adsorption energy of elemental mercury Hg0 by active defect of amorphous SiO2 is less than 50 kJ/mol, proving the adsorption to be the weak physical kind;whereas the adsorption energy of oxidized mercury HgCl by active defect of amorphous SiO2 is greatly larger than 50 kJ/mol, indicating a typical chemical adsorption, and the interaction between HgCl and SiO2 is covalent.