Efficient removal of metal contaminants by EDTA modified MOF from aqueous solutions

Herein a versatile adsorbent has been synthesized by immobilization of ethylenediaminetetraacetic acid (EDTA) into the pores of the Zr-based metal organic framework (UiO-66) through a facile method. The as-prepared EDTA modified UiO-66 (UiO-66-EDTA) was characterized completely to investigate its physical and chemical properties. It shows great chemical stability with octahedral structure and carboxylic groups and amine groups. Through batch experiments, UiO-66-EDTA shows no specificity for the removal of diverse heavy metal ions (three categories: soft acids, hard acids, and borderline acids) because of its both hard and relatively softer chemical characters of functional groups. The maximum removal capacities of UiO-66-EDTA for Eu³⁺ (hard acids), Hg²⁺ (soft acids) and Pb²⁺ (borderline acids) are 195.2, 371.6 and 357.9 mg g⁻¹, respectively. Notably, 11 metal ions removal efficiency reaches over 99% in co-existing system. The results from X-ray photoelectron spectroscopy (XPS) analysis reveal the coordination of Eu³⁺, Hg²⁺ and Pb²⁺ with carboxyl groups (–COOH) and tertiary amine groups (C–N(C)–C) is responsible for their removal by UiO-66-EDTA. Given the fact that UiO-66-EDTA possesses high chemical stability, facile synthesis method, efficient removal performance and superior reusability, it can be applied in treatment of seriously polluted water with multi-pollutants.