Highly efficient capture of phosphate from water via cerium-doped metal-organic frameworks

Abstract

A highly effective and neoteric cerium-doped metal-organic framework (MOF Ce-UiO-66-NH2) was triumphantly prepared via a simple and convenient approach of solvothermal reaction; the Ce-UiO-66-NH2 can be used for removing phosphate from water. The physicochemical characteristics of new adsorbent were determined by X-ray diffraction (XRD), Brunauer–Emmett–Teller analysis (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and infrared spectroscopy (FTIR). The results confirmed that the introduction of cerium caused a trivial effect on the UiO-66-NH2 structure; however, a hybrid MOF with polyhedral crystalloid shapes was obtained. When cerium was doped in UiO-66-NH2, the newly developed adsorbent Ce-UiO-66-NH2 exhibited outstanding performance in terms of adsorption of phosphate, and the maximum uptake capacity was up to 211.86 mg g−1. The reaction for capture of phosphate of 0.75Ce-UiO-66-NH2 was quite fast, and could reach equilibrium in 60 min. Furthermore, FTIR and X-ray photoelectron spectroscopy (XPS) characterization indicated that the main mechanism of phosphate capture involved the production of an inner-sphere complex of Zr/Ce–O–P and electrostatic attraction. After adsorption, the phosphate on Ce-UiO-66-NH2 was efficiently desorbed with NaOH (0.10 mol L−1); thus the material could be used repeatedly for at least five cycles, and the adsorption capacity was still more than 100 mg g−1 at the fifth cycle. The repeated utilization potentially provides access to effectively prevent water pollution and further implement cleaner production at the minimum cost. The developed Ce-UiO-66-NH2 is an efficient and regenerative adsorbent that can be used for phosphate uptake to mitigate increasing eutrophication of water.