Density Functional Theory Study Of Hg~0 Adsorption On Si-doped And Al-doped Graphene

The emission of mercury in coal-fired power stations has an extremely bad effect on human and the ecological environment.Mercury in flue gas has three forms:elemental mercury(Hg0),divalent mercury(Hg2+)and particulate mercury(Hgp).The elemental mercury is very stable in nature and not easy to remove.The adsorption method is one of the main methods to remove the elemental mercury and its key is to find effective adsorbents for adsorption and removal of mercury.Since the discovery of graphene,it is well known for its good adsorption properties.Therefore,the quantum mechanical density functional theory was used to study the adsorption of mercury on the surface of graphene in this study.Firstly,the adsorption of mercury on the surface of primary graphene and defective graphene was investigated.The result shows that elemental mercury are physically adsorbed on both surfaces.The most stable adsorption site on the surface of primary graphene is the top site,while that on the surface of the defective graphene is empty acupoint.The existence of defects on the surface of graphene promotes the adsorption of mercury.Secondly,the effect of atoms doping on the graphene was investigated.In this paper,the silicon doped and aluminum doped graphene were selected.For single atomic doped structures,the adsorption of mercury on Si doped graphene is physical adsorption,while that on A1 doped graphene is chemisorption.Of course,both two kind of atoms enhance the adsorption effect.Finally,the effects of different doping positions and numbers on the surface of graphene were investigated.Whether it is for Si doped structure or A1 doped structure,the higher the degree of independence between the doping positions is,the better the mercury adsorption effect is.When the number of doped atoms is increasing,the effect of mercury adsorption is better.As for the single defective graphene,the adsorption capacity of Si doped graphene increases first and then decreases with the increase of Si atoms,while the adsorption ability of Al doped graphene decreases with the increase of Al atoms.