Zeolitic Imidazolate Framework-67: A promising candidate for recovery of uranium (VI) from seawater

Abstract

With the development of the nuclear industry and nuclear technology application, it is important to develop adsorbents with high selectivity and adsorption capacity for removal of uranium from nuclear waste and for trace uranium capture from seawater. In this report, we investigated for the first time Zeolitic Imidazolate Framework-67 (ZIF-67) for the removal of uranium from aqueous solutions and trace uranium from simulated seawater. The influence of pH, contact time and initial uranium concentration were studied. Results showed that ZIF-67 possessed an ultrahigh adsorption capacity (Qm = 1683.8 mg g−1) and high removal rate at both ppb and ppm levels (>99%) for uranium. The adsorption process fits well with the Langmuir isotherm model and pseudo-second-order rate equation. In addition to the general characterization of ZIF-67 by XRD, SEM, TEM, and FT-IR, the uranium-adsorbed ZIF-67 was investigated by X-ray photoelectron spectroscopy (XPS), which revealed a possible mechanism that involved the existence of large amounts of CoOH and active sites produced after the dispersion of ZIF-67 in water; CoOH was the key factor that ZIF-67 possessed to realise a high adsorption capacity and affinity for uranium (VI).