The Effect Of Fulvic Acid On The Adsorption Of Pb(?) In Water By Post-modified MIL-100(Fe)

Metal-organic frameworks(MOFs),as a noval material with high specific surface area,high porosity and ease of post-synthetic modification(PSM),was applied to metal ion adsorption firstly in 2010.In recent years,PSM using functional groups has enabled MOFs to have boosted adsorption performance for heavy metal removal.For practical application of MOFs in wastewater treatment,material's adsorption performance is not the only determinant,the influence of environmental factors also plays an important role.Fulvic acid(FA),as a natural organic matter(NOM),is ubiquitously dissolved in the natural environment and has been reported to affect the reactivity of various adsorbents.Nevertheless,there is no related research that has been done for the effect of FA on MOFs.Therefore,in our study,we prepared a novel material ED-MIL-100(Fe)and compared it with its parent MOF material for adsorption capacity towards Pb in water.Besides,FA was investigated for its effect on the physicochemical property of MOF for the first time.The results show that the charge on the surface of MIL-100(Fe),modified with ethylenediamine can be changed from the positive to the negative on the ED-MIL-100(Fe)surface,which will greatly facilitate the adsorption of cationic heavy metals.Additionly,results showed the ED-MIL-100(Fe)enabled 99%removal of Pb(?)from water at or below60 mg L^-1,whereas the parent MIL-100(Fe)hardly adsorbed any Pb(?).The adsorption percentage of the Pb(?)ions(76%)outcompeted that of other metal ions(i.e.Co(?),Cu(?),Ni(?),Zn(?),and Cd(?))(each?25%)in the mixed solution.It means that the adsorption behavior of Pb(?)is more selective than other metal ions.In the experiment of the influence of FA on the adsorption properties of the materials,the negative surface charge of ED-MIL-100(Fe)was not affected by increasing concentrations of FA.Interestingly,increasing FA concentration steadily increased the functional groups surrounding the ED-MIL-100(Fe)via electrical interaction,thus facilitating the Pb(?)ions adsorption.In conclusion,the modified MIL-100(Fe)has good adsorptive and selective properties for lead ions in water,and it can be considered as an alternative adsorbent in water.