Preparation of EDTA-modified UiO-66 for the selective removal of Cu(II) from water

A novel metal-organic framework adsorbent, UiO-66-EDTA, was synthesized by chemically linking of UiO-66-NH2 with ethylenediaminetetraacetic acid (EDTA) to improve the sorption efficiency and selectivity for Cu(II) in water. The product UiO-66-EDTA was characterized by various instruments. The adsorption kinetic and isotherm data for Cu(II) were in line with the pseudo-second-order and Langmuir models, respectively, confirming monolayer chemisorption dominated the loading of Cu(II) on pore channel surface. For Cu(II) ion adsorption, UiO-66-EDTA showed a high maximum adsorption capacity of 154.8 mg/g at pH 6.0, which was much greater than the precursor UiO-66-NH2. Besides, thermodynamic analysis revealed that the loading of Cu(II) on UiO-66-EDTA was spontaneous and endothermic. Furthermore, the functionalization with EDTA significantly improved the adsorption selectivity of UiO-66 for Cu(II) compared to other coexisting cations in water. X-ray photoelectron spectroscopy depicted that Cu(II) ion binding occurred by complexation with oxygen/nitrogen atoms on the EDTA ligand. As a regenerable adsorbent, UiO-66-EDTA was considered to have an obvious application prospect for selectively absorbing Cu(II) ions in water.