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-NH2 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(11) through monodentate N atoms and bidentate O groups. MOFs-DHAQ has good application prospect in the removal of lead from wastewater. (C) 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.