Development of magnetic nickel prussian blue analog composites using simple synthesis treatment for efficient cesium removal

The radioactive cesium species (e.g., 137Cs) in radioactive waste have necessitated the development of strategies for its selective removal from contaminated water. In this study, we synthesized nickel-modified Prussian blue/maghemite (NiPB/γ-Fe2O3) composite materials exhibiting high selectivity for Cs ions. The composites were synthesized via a facile hydrothermal reaction, and their magnetism was confirmed through an X-ray magnetic circular dichroism measurement. The composites selectively separated Cs from solutions containing alkali and alkaline earth metal cations, with a removal efficiency of ≥ 99.7 %. The synthesis mechanism involved the hydrothermal reaction, including partial oxidation and subsequent γ-Fe2O3 formation. The maximum adsorption capacity of the NiPB/γ-Fe2O3 composites, assuming successful magnetic separation, was determined to be 102 mg g−1 using the Langmuir adsorption model. The powder X-ray diffraction patterns revealed enhanced crystallinity in the composites compared to NiPB, with a distorted structure framework from face-centered cubic to rhombohedral. XAS spectra showed changes in vibration peaks due to hydrothermal treatment, indicating partial oxidation of Fe(Ⅱ) to Fe(Ⅲ). The composites exhibited superparamagnetism, whereas NiPB showed no magnetization. These findings highlight the potential of NiPB/γ-Fe2O3 composites in environmental remediation and radioactive waste management, providing an effective solution for Cs removal from contaminated systems.