Highly efficient adsorption and removal of Cd(II) from wastewater by mass synthesis of magnetically functionalized UiO-66 based on its high coordination advantage

The development of heavy metal adsorbent materials that combine high yield and high adsorption capacity is a challenging problem. In this study, we report a novel magnetic adsorbent (Fe3O4@UiO-66-Lcys) for the efficient removal of cadmium from wastewater. Among them, UiO-66 was loaded on the Fe3O4 core by solvothermal method, followed by loading a large amount of L-cysteine (Lcys) on its surface by amidation reaction. The material innovatively achieves a large and uniform loading of functionalized groups on the magnetic core, which is a strategy for targeted removal of heavy metals. The successful synthesis of the materials was confirmed by structural characterization such as FTIR, TGA, and XRD. Excitingly, the composite has excellent adsorption performance, with the maximum adsorption of Cd2+ by Fe3O4@UiO-66-Lcys of 430.89 mg/g at the temperature of 298 K, which is more than five times that of Fe3O4@UiO-66. According to the mechanism analysis, the large amount of –COOH on UiO-66 provided enough sites for the stable grafting of L-cysteine, which exposed a large number of –NH2, –COOH, and −SH groups on the surface of the material, and provided abundant adsorption sites for Cd2+ chelation. In addition, the structure of the adsorbed material remained stable, and the removal rate of Cd2+ was still above 90 % after five times of reuse. Therefore, Fe3O4@UiO-66-Lcys is a good adsorbent for the removal of Cd2+ from wastewater, which provides an idea for the development and creation of high-yield, high-efficiency, and reusable green adsorbents.