Tailored metal-organic frameworks facilitate the simultaneously high-efficient sorption of UO22+ and ReO4− in water

The simultaneously efficient extraction of radioactive metal cations and anions from radioactive waste is of great interest for the proper disposal of spent fuel and environmental protection. Modifying metal-organic frameworks (MOFs) into multifunctional materials with controllable and desired properties is an efficient strategy for broadening their practical applications. Herein, poly(ethyleneimine) (PEI) tailored MIL-101(Cr) (MILP) was obtained through an easy operation and low-cost strategy and was utilized to simultaneously extract uranium (UO22+) and rhenium (ReO4−) from water. The effects of PEI coating amounts, system pH, contact time, initial UO22+/ReO4− concentrations, ionic strength, as well as interfering ions were studied to evaluate the sorption performance of MILP composites. The maximum sorption capacity was 416.67 mg/g for UO22+ at pH 5.5 and 434.78 mg/g for ReO4− at pH 3.5, levels that are superior to those of most adsorbents. The sorption of UO22+/ReO4− occurred in a pH-dependent, spontaneous and endothermic manner, which showed preferable modeling by the pseudo-second-order (PSO) kinetic equation and Freundlich isotherm equation. The adsorption of ReO4− was inhibited by the coexistence of UO22+ and high ion strength. Batch experiments and X-ray photoelectron spectroscopy (XPS) results indicate that UO22+/ReO4− sorption was driven by the abundant amino groups and unsaturated metal sites in the MILP-3 composites. MILP-3 also showed excellent recycling performance and maintained high sorption capacities for UO22+/ReO4− in different simulated water samples. This study shows that MILP composites can effectively extract radioactive metal cations and anions from water, and lays a foundation for designing an excellent new category of candidates with versatile functions for wastewater management. Poly(ethyleneimine) coating motivates the high-efficiency and selective extraction of MIL-101(Cr) nanoparticles for both UO22+ and ReO4− from water. [Display omitted] •Highly efficient removal of both UO22+ and ReO4− was achieved by MILP.•MILP-3 displayed a maximum UO22+ and ReO4− uptake capacity of 416 mg/g (pH 5.5) and 435 mg/g (pH 3.5).•MILP-3 showed superior selectivity and high reusability for UO22+ and ReO4−.•MILP-3 was efficient in UO22+ removal from contaminated synthetic waters.•The interaction between UO22+/ReO4− and MILP-3 was traced by XPS.