飞灰中的缺陷位SiO_2对痕量元素As的吸附机理

Adsorption mechanism of trace As on the defect sites of SiO_2 in fly ash

为了认识痕量元素As在飞灰中的富集特性,利用密度泛函理论研究了砷的典型氧化物AsO在飞灰中的主要成分SiO_2模型上的吸附机理,对优化后的吸附构型进行能量计算、AIM理论、Mulliken电荷分析以及定域化轨道指示函数(LOL)填色图分析,剖析了AsO与SiO_2表面的相互作用。结果表明,AsO在无定型SiO_2表面的缺陷位的吸附能均大于50 k J/mol,吸附构型均为典型的化学吸附。在无定型SiO_2缺陷活性位点形成的As-Si键、Si-O键和As-O键强度较大,均属于共价键;SiO_2与AsO之间为共价相互作用。

To understand the enrichment characteristics of trace As in fly ash,the adsorption mechanism of AsO,a typical arsenic oxide,in SiO 2,the main component of fly ash,was investigated by using density functional theory;energy calculation,AIM theory,Mulliken charge analysis and Localized Orbital Locator(LOL)color map were performed on the optimized adsorption configuration,in order to analyze the interaction between AsO and SiO 2.The results show that the adsorption energy of AsO on the defect sites of amorphous SiO 2 is higher than 50 kJ/mol,typical for the configuration of chemical adsorption.The bonds of As-Si,Si-O and As-O formed at the active defect sites of the amorphous SiO 2 have high strength,belonging to the covalent bond;that is,the interaction between SiO 2 and AsO is covalent.