A novel multi-shelled Fe3O4@MnOx hollow microspheres for immobilizing U(VI) and Eu(III)

The leakage of radionuclides poses a great threat to the global ecosystem, which has aroused world-wide continuous attention. Since sorption plays the most important role in their environmental fate and humic acid (HA) is a key factor to their migration behavior, it is necessary to develop highly-efficient adsorbents that can remove radionuclides from the contaminated water in the presence of HA. Herein, we reported a novel multi-shelled Fe3O4@MnOx, which showed considerable sorption capacities towards uranium (U(VI)) and europium (Eu(III)). From the systemic batch experiments, the sorption kinetics follows the pseudo-second-order model, and sorption thermodynamics are endothermic processes. The sorption edges are pH-dependent but independent of ionic strength. Furthermore, the sorption isotherms are well described by the Langmuir model, giving maximum sorption capacities of 106.72 mg.g(-1) for U(VI) and 138.13 mg.g(-1) for Eu(III) at 298 K. Based on the spectroscopic studies, U(VI) is mainly adsorbed on the Mn-III-O-H site while Eu(III) shows higher affinity to the Mn-IV-O-H site. In the presence of humic acid (HA), the HAUO(2)(+) and (HA)(2)Eu+ species can accelerate the sorption kinetics and enhance the sorption capacities. This work can not only boost the exploration of adsorbent systems in the field of materials, but also promote the investigations of the interface reaction mechanism in the field of radiochemistry.