Magnetic-dictyophora indusiata derived biochar composite for efficient removal of U(VI) and mechanism investigation

Abstract

Nuclear energy has been extensively studied in recent years which accelerated the consumption of nuclear fuel. However, the misusing, accidents, and improper transportation of nuclear radionuclides would inevitably contribute to the discharge of uranium (U(VI)) into natural world. The toxicity, radioactivity, and mutagenesis of U(VI) has made it become one of the most serious radioactive contaminants and demanded a highly efficient removal approach, which was an urgent task for creatures and environment. As an economically feasible adsorbent, magnetic materials such as Fe3O4 has been considered as a potential scavenger for U(VI) elimination from aqueous environment. Whereas, Fe3O4 is prone to conglomerate which lowers the efficiency and is the bottleneck in the application of eliminating radionuclide U(VI). To decrease the conglomeration, biochar was applied to modify Fe3O4. In this paper, Magnetic-Dictyophora indusiata derived biochar (M-DI) was successfully synthesized by an easy and green hydrothermal method using dictyophora indusiata derived biochar (DI), FeCl3•6H2O and CH3COONa as reactants and glycol as solvent. Different characterization technologies were employed to explore the structure, magnetic properties and other physicochemical properties of M-DI, and serial batch experiments were conducted to investigated the removal performance of M-DI and elimination mechanism towards U(VI). The scanning electron microscopy, transmission electron microscopy and elemental analysis results manifested M-DI was successfully synthesized, and N2 Brunauer-Emmett-Teller surface area measurement as well as the vibrating sample magnetometer technologies indicated M-DI possessed excellent surface properties and magnetic properties (37.74 emu g-1). Macroscopic study at the condition of pH 5 and solid content at 0.1g L-1 exhibited the fast dynamics (within 30 min), high capacity (122.8 mg g-1) of U(VI) elimination towards M-DI material, and the thermodynamic parameter (ΔG0, ΔS0, ΔH0) calculation results indicated that the adsorption process was a spontaneous endothermic process of increased entropy. The capacities of U(VI) elimination increased with temperature while barely affected by ionic strength. The removal mechanism was confirmed to be controlled by inner-sphere complexation and electrostatic attraction. In addition, the separation of M-DI from liquid phase was easy to complete under the magnetic field. Overall, the synthetization of M-DI which has a wide source range of raw materials, the excellent surface properties and efficient capacities of U(VI) elimination can not only declared the benefits of M-DI application for environmental remediation but also lead a new direction of magnetic materials modification. In the meantime, the outstanding performances for U(VI) removal and the potential practical prospect in water purification demonstrated the widely utilization of M-DI in foreseeable future.