Mercury adsorption and regeneration mechanism of ironbased modified biochar based on density functional theory

To further explore the adsorption characteristic of biochar mercury and improve the adsorption performance of biochar mercury,the ironbased modified biochar mercury remover with biobased as the carrier is prepared by coprecipitation method. Based on the density functional theory (DFT) and a variety of characterization and calculation methods,through the combination of high valence metal ions,lattice oxygen and oxygen vacancy,the metal doped defective carbon ring is constructed as the molecular model of ironbased modified biochar. The reaction path of Hg 0 on the surface of ironbased modified biochar is studied. The activation energy barrier and the rate determining step of Hg 0 adsorption on the surface of modified biochar are determined. The reaction mechanism of Hg-Fe10%-BC and the corresponding bonding mechanism are further revealed. In addition,on the basis of verifying the feasibility of regeneration of inactivated biochar with different ironbased loading ratios,the regeneration reaction mechanism of inactivated biochar is revealed and the influence of reaction conditions and oxygencontaining functional groups on the adsorption process is explored. It is found that:The adsorption process of Hg 0 on ironbased modified biochar included diffusion and adsorption stages. Hg 0,as a Lewis base,is easy to react with the modified biochar as a Lewis acid,while HgO is the main occurrence form after Hg 0 adsorption,The oxygen vacancy with electrons is the chemical adsorption site in the adsorption process,and the metal ions and the lattice oxygen in the corresponding oxides uniformly dispersed in the biochar are the oxidation sites in the reaction process,The oxygencontaining functional groups further affect the mercury adsorption performance of biochar through their own acidbase degree,The regeneration of inactivated biochar is limited by the length of oxygen chain. And the maximum mercury adsorption efficiency decreases to 90% of that of modified biochar. The adsorption mechanism of Hg 0 on ironbased modified biochar and the regeneration mechanism of inactivated modified biochar are quantitatively revealed,which provides theoretical basis and key data for the optimization of mercury removal methods in the future.