DFT Study On The Adsorption Of Trace Elements By SiO₂ And K₂O In Fly Ash

In recent years,the problem of air pollution caused by coal-fired power generation has become increasingly serious.Coal-fired power stations at home and abroad have perfect control measures for conventional atmospheric pollutants such as NO_X,SO_X and dust,but pollution prevention measures for trace elements such as mercury and arsenic have yet to be improved.Therefore,in this paper,the Density Functional Theory is used to study the adsorption mechanism of SiO₂,K₂O adsorbent in fly ash with trace gases such as mercury and arsenic in flue gas.In order to study the enrichment characteristics of trace elements in fly ash,the typical oxide AsO,elemental mercury Hg⁰ and oxidized mercury HgCl in ash adsorpted on the SiO₂ model were studied by Gaussian and Multiwfn software using density functional theory.Energy calculation,AIM theory and Mulliken charge,and Mayer bond level are analyzed for the optimized adsorption configuration.And make a localized orbit indication function（LOL）color map,localized molecular orbital map（LMO）,etc.,using graphically intuitive analysis of interaction types.The results show that the adsorption energy of AsO、oxidized mercury HgCl on the surface of amorphous SiO₂ are more than 50 kJ/mol,and the adsorption configuration is typical chemical adsorption.SiO₂-AsO、SiO₂-HgCl all belong to a covalent interaction.The adsorption energy of elemental mercury Hg⁰ on the surface of amorphous SiO₂ is less than 50 kJ/mol,which is a weak physical adsorption.Study on the adsorption mechanism of trace elements As and Hg in K₂O crystals in fly ash,the surface of K₂O crystal and the adsorption configuration of trace gases AsO and Hg⁰ were optimized by using Dmol³ module in Materials Studio software.The energy calculations of the optimized adsorption configurations were carried out,and the optimal adsorption position of the adsorption configuration was obtained.The density of the adsorption configuration and the density of the partial wave states were analyzed.The results show that the adsorption of AsO on the surface of active K₂O crystals in fly ash is strong chemical adsorption,and the optimal adsorption position of AsO molecule on the surface of K₂O crystal（1 1 1）is the top position of O atom The adsorption energy is 138.25 kJ/mol,which is a typical chemical adsorption,the resonance intensity and overlapping region of the resonance peak between the O atoms of the K₂O and As are large,indicating that the interaction is strong.On the surface of K₂O crystal（1 1 1）,the adsorption of elemental Hg⁰ is weaker physical adsorption,and the optimal adsorption position is also the top position of O atom,and its adsorption energy is 46.50kJ/mol,the partial wave state density of the O atom of K₂O and Hg⁰ has almost no formant,indicating that the interaction is weak.In this paper,quantum chemistry is introduced into the adsorption and removal of pollutants from coal-fired power plants by fly ash adsorbents.It is confirmed that the defected SiO₂ and active K₂O（1 1 1）crystals in the fly ash can be used as adsorbents for adsorbing trace atmospheric pollutants in flue gas.This research lays a solid theoretical foundation for transforming the existing pollution control devices of coal-fired boilers,and truly achieving the joint removal of various pollutants from coal-fired power plants.