Functionalized UiO-67-Rhodanine-3-acetic acid (Rd) composites efficiently trapping Pb (II) in wastewater

Metal organic frameworks (MOFs) have the advantages of large specific surface area, high porosity, controlled structures and strong stability, and were excellent adsorbents for the efficient trapping of heavy metals. In this work, two morphologies of Zr-MOF composites (UiO-67-AC-Rd and UiO-67-FA-Rd) under different solvent conditions were synthesized by a sequential solvothermal process. The properties of the composites were characterized by SEM, TEM, XRD, XPS, and BET, and the adsorption capacities of Pb (II) were investigated in detail. The excellent performance of UiO-67-AC-Rd exhibited superfast removal efficiencies for Pb (II), ascribing to its surface contains plentiful oxygen, nitrogen and sulfur functional groups and large specific surface area, which makes it have fascinating properties in removing Pb (II), and the maximum adsorption capacity of Pb (II) was 309.8 mg g-1. Chelation and electrostatic adsorption were considered as the main adsorption mechanisms. Adsorption isotherms were fitted well using the Langmuir and Freundlich model, and the adsorption thermo-dynamics indicated that the adsorption process was endothermic and spontaneous. The UiO-67-AC-Rd composites maintained excellent adsorption capacity for Pb (II) after four consecutive cycles, and the removal efficiency was above 74 %. The study will further provide a new pathway to the application of UiO-67-Rd composites in the adsorption of heavy metals in wastewater.