Post-synthetic modification of zirconium-based metal-organic frameworks for enhanced simultaneous adsorption of heavy metal ions and organic dyes

Heavy metal and dye pollution pose a serious threat to human health and ecology, and there is an urgent need to develop novel adsorbent materials for wastewater treatment. In this study, a novel functionalized zirconium-based MOF UiO-66-Gd was prepared by a post-synthetic modification strategy and used for the simultaneous removal of Pb²⁺, Cu²⁺ and methylene blue (MB) from wastewater. UiO-66-Gd retained the crystalline structure and morphological features before modification. The specific surface area reached 574.94 m²/g, which can provide abundant active sites for adsorption. The effects of several factors on the adsorptive performance of UiO-66-Gd were investigated by batch adsorption experiments. The adsorption of Pb²⁺ by UiO-66-Gd reached the adsorption equilibrium in only 5 min. The theoretical maximum adsorption capacities for Pb²⁺, Cu²⁺ and MB were 833.33, 354.61 and 564.91 mg/g, respectively. In addition, UiO-66-Gd has excellent anti-interference and regeneration properties with potential for practical applications. Competition adsorption experiments showed that UiO-66-Gd had the greatest affinity for Pb²⁺. The adsorption of UiO-66-Gd on Pb²⁺ and Cu²⁺ was mainly through electrostatic interactions and chelation, and on MB mainly through electrostatic interactions, π-π interactions and hydrogen bonding. Overall, UiO-66-Gd has great potential for application in the removal of Pb²⁺, Cu²⁺ and MB.