| Metal mercury can not only pollute the environment of human’s home,but also cause great harm to human health.Metal-organic skeleton materials as adsorbents have great potential in chemical separation.Zirconium-based organic Frameworks have attracted much attention due to their advantages of high thermal stability,large specific surface area and adjustable structure.It is of great significance to design and develop zirconium matrix materials with adsorptive mercury removal.In this paper,the high-throughput screening technique was used to screen the candidate materials with the best adsorption performance of metal mercury in the MOF library.Additionally,the adsorption performance of mercury and compounds in the presence of sulfur dioxide and water vapor was studied.The adsorption capacity,Henry coefficient,Henry selectivity,GCMC selectivity and other thermodynamic properties of elemental mercury were calculated using Grand Canonical Monte Carlo simulation.Ten Zr-MOFs with excellent performance were selected according to their thermodynamic properties.In order to study the structure-activity relationship,the adsorption mechanism of UiO-66-(SO3H)2 and MOF-801 with excellent adsorption properties was studied.The adsorption isotherms,density distribution,free energy and radial distribution function of elemental mercury in the two Zr-MOFs were calculated in the presence of different concentrations of sulfur dioxide.It is concluded that pore size has an important effect on the adsorption and removal of Hg0 in flue gas.The presence of SO2 molecule did not inhibit the adsorption properties of UiO-66-(SO3H)2 and MOF-801 for elemental mercury.Based on 181 organic zirconium matrix materials,we studied the separation performance of elemental mercury in the presence of water vapor.The relationship between material physical parameters and adsorption capacity shows that the adsorption capacity of elemental mercury can be changed through adjustments to material physical parameters.Efficient adsorption of elemental mercury can be attained by controlling the LCD value of Zr-MOFs within the range of 5.00-7.50 A,VF in the range of 0.30-0.45,and GSA below 500 m2·g-1.Under two humidity conditions(RH=36%and RH=80%),the density distribution of fluid molecules of UiO-66-(SO3H)2 and MOF-801,which have excellent adsorption properties,was studied.The results revealed that the presence of water molecules does not inhibit the adsorption of elemental mercury;In fact,it can enhance the adsorption to some extent.Furthermore,the adsorption capacity of mercury chloride was calculated in 181 kinds of Zr-MOFs materials,and two types of Zr-MOFs(Zr-L5 and MOF-806)with the best adsorption performance were selected.In order to study their selectivity and adsorption properties in mixtues,the adsorption isotherms of mercury chloride and sulfur dioxide were calculated.The results of adsorption isotherms showed that sulfur dioxide slightly inhibited the adsorption of mercury chloride;However,the inhibition effect was very weak.To confirm the weak inhibition effect,the density distribution was calculated.There was little change in the density distribution in the cavity,which also confirmed the weak inhibition effect of sulfur dioxide molecules.In order to study the effect of humidity on adsorption properties,we calculated the adsorption isotherms of mercury chloride and water in Zr-L5 and MOF-806 under the relative humidity of 36%and 80%,respectively.The results demonstrated that the insertion of water molecules into the two skeleton materials has an inhibitory effect on the adsorption of mercury chloride.Despite the fact that Zr-L5 has stronger hydrophobicity than MOF-806,Zr-L5 was found to adsorb more water molecules than MOF-806 because of its large pore cavity and high specific surface area.These finds suggest that pore cavity and specific surface area are important characteristics affecting adsorption.In order to further investigate the influence on adsorption,we calculated the density distribution in the binary mixtures.The results of density distribution also confirmed that Zr-L5 and MOF-806 are potential MOFs for mercury chloride adsorption due to their special structure. |
PDF Full Text Request