Experimental and DFT study of selective adsorption mechanisms of Pb(II) by UiO-66-NH2 modified with 1,8-dihydroxyanthraquinone

A new adsorbent (MOFs-DHAQ) was prepared by functionalizing UiO-66-NH 2 with 1,8-dihydroxyanthraquinone to remove Pb(II) from wastewater. The optimum pH, adsorption kinetics and adsorption isotherms were studied. MOFs-DHAQ has a good removal rate for Pb(III) at pH 4. It takes only 30   min to reach maximum adsorption capacity about 213.3 mg/g. The experimental data conforms to the pseudo-secondary kinetics and the Freundlich models. The adsorption process belongs to multilayer chemical adsorption . Desorption and adsorption experiments indicate that the adsorbent can be recycled at least four times. The rising temperature favors the adsorption of Pb(II) on MOFs-DHAQ because the adsorption process is a spontaneous endothermic reaction. The interaction mechanism between Pb(II) and the reactive group is mainly electrostatic interaction and complexation. MOFs-DHAQ has excellent selectivity for removing Pb(II) from wastewater contains a variety of interfering ions. The calculated adsorption capacity ( Q ex ) of Pb(II) for column adsorption was 108.04 mg/g and was consistent with the Thomas model's adsorption capacity( Q Th ) about 109.63mg/g. Density functional theory calculations show that MOFs-DHAQ combines with Pb(II) through monodentate N atoms and bidentate O groups. MOFs-DHAQ has good application prospect in the removal of lead from wastewater.