Combining batch technique with theoretical calculation studies to analyze the highly efficient enrichment of U(VI) and Eu(III) on magnetic MnFe2O4 nanocubes

The progress of efficient and low-cost materials for environmental remediation is highly desirable but remains challenging. Herein, we fabricated magnetic bimetal oxide MnFe2O4 nanocubes (NCs) by co-precipitation phase inversion method. Characterization of the as-prepared nanomaterials revealed that MnFe2O4 NCs had an average size of 50-70 nm and possessed unique magnetic properties for adsorbent separation. The adsorption behavior and interaction mechanism of U(VI)/Eu(III) on MnFe2O4 were explored by batch experiment and spectroscopy analysis combined with density functional theory (DFT) calculations. Batch experimental results showed that U (VI)/Eu(III) sorption onto MnFe2O4 were independent of ionic strength, indicating the formation of inner-sphere surface complexes. The maximum sorption capacities of MnFe2O4 calculated from Langmuir isotherm model at 298.15 K were 119.90 mg.g(-1) for U(VI) at pH 5.0 and 473.93 mg.g(-1) for Eu(III) at pH 7.0, respectively. Furthermore, the excellent regeneration and reusability of MnFe2O4 could support long-term application in wastewater and sewage treatment. The analysis of FT-IR and XPS in combination with DFT calculations revealed that the interaction of U(VI)/Eu(III) onto MnFe2O4 was mainly ascribed to the strong ionic bonds (M-O) and hydroxyl (-OH) groups via electrostatic interaction and surface complexation. The resulting MnFe2O4 further exhibited high effective retention and recovery for U(VI)/Eu(III) from synthetic water systems and real seawater. This work highlighted that MnFe2O4 NCs were exceptionally capable in rapidly and efficiently sequestering U (VI)/Eu(III) from natural water and sewage, which would be a great prospect and further widely used in other lanthanides/actinides remediation.