Thermal-responsive Ion-imprinted magnetic microspheres for selective separation and controllable release of uranium from highly saline radioactive effluents

Abstract

Recovery of uranium from highly saline radioactive effluents is strategically important both for environmental concerns and sustainable development of nuclear energy. However, high-efficiency extraction of uranium from highly saline low-level liquid wastes (SLLWs) remains challenges of slow rate, poor selectivity and complicated regeneration. In this work, we report a strategy for highly selective separation and facile recovery for uranium from SLLWs by thermal-responsive uranyl ion-imprinted magnetic microspheres (UIMM). The adsorbent showed better selectivity for uranium against other cations compared with non-imprinted magnetic microspheres (NIMM), and the adsorbent has good salt resistance. Moreover, the adsorption equilibrium of UIMM could be achieved within 10 min, and the maximum uptake capacities are 122.7 mg/g and 231.5 mg/g at 298.15 K and 305.15 K, respectively. Importantly, highly efficient elution can be attained facilely via changing the temperature of elution, which can avoid secondary pollutants caused by the use of a large number of eluents. And the magnetic separation of the adsorbent can greatly improve its practical performance. XPS spectra indicate that uranium(VI) is partly reduced to a lower uranium(IV) state by Fe2+ on the Fe3O4 surface besides being adsorbed on the materials by phosphonic acid and N-isopropylacrylamide.