Fabrication of phosphorylated UiO-66 for efficient selective removal of Pb 2+from acidic wastewater

Metal-organic framework (MOF) materials have emerged as promising candidates for treating heavy metal wastewater because of their controllable pore size, high specific surface area, and abundant active sites. Nevertheless, the currently reported MOFs usually require near-neutral environments (pH = 5 - 6) to achieve efficient removal of Pb 2 + and cannot be applied to acidic environments (pH = 2 - 3). In this work, the structurally stabilized zirconium-based MOF UiO-66 was chosen as the object of study. Three phosphate ester -based MOFs (UiO-66-(OPO 3 ) X ) containing different amounts and spatial positions were designed and prepared by simple chemical modification and used to remove Pb 2 + . Adsorption experiments showed that they could reach adsorption equilibrium in 30 min with excellent adsorption rate. Owing to the unique ionization ability of the phosphate ester group, UiO-66-(OPO3) X maintains a high removal efficiency of Pb 2 + even at pH = 2 and pH = 3. In addition, selectivity and competition experiments demonstrated that UiO-66-(OPO 3 ) X possessed excellent selectivity and anticompetitive ability towards Pb 2 + .The excellent regeneration performance demonstrates their value for practical application. Moreover, the adsorption mechanism was investigated in detail by experiment combined with density functional theory (DFT).