Synthesis of magnetic Fe₃O₄/CFA composites for the efficient removal of U(VI) from wastewater

The application of thermal power plant waste (coal fly-ash, CFA) for the potential retention of U(VI) from wastewater was crucial in radionuclide contaminant management. In this work, magnetic Fe₃O₄/CFA composites were synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) and energy dispersive (EDS) spectroscopy techniques. The as-synthesized Fe₃O₄/CFA composites were applied to remove U(VI) from aqueous solutions and the results showed that U(VI) sorption was mainly dominated by inner-sphere surface complexation at low pH values, and by outer-sphere surface complexation at high pH values. According to the results of X-ray photoelectron spectroscopy (XPS) and FTIR analysis, the high sorption of U(VI) on Fe₃O₄/CFA composites was mainly attributed to Fe–O bond. Compared with CFA (Q_max = 0.254 mmol/g), Fe₃O₄/CFA composites exhibited excellent U(VI) sorption capacity (Q_max = 1.380 mmol/g), relative high and stable U(VI) sorption ability under high pH values (pH 6∼10) in 0.1 M NaCl. The investigation was meaningful for the “treating wastewater with wastes” strategy implementation, especially in the aspect of reducing the environmental pollution caused by thermal power plant waste and their application in nuclear pollution management.