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

Abstract

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 (MO) 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.