Enhanced cesium adsorption and desorption mechanisms in ZnFe Prussian blue analogs: Structural transformation and reusability

The management of radioactive cesium (¹³⁷Cs) is critical due to its long half-life, environmental persistence, and harmful effects on human health and ecosystems. Although Prussian blue analogs (PBAs) have gained attention for their potential in adsorption-based Cs⁺ removal, the structural changes that occur during adsorption and desorption cycling are poorly understood. This study investigates the synthesis of ZnFe-PBAs using various methodologies, including photochemical reduction and the use of different precursors and reducing agents, to achieve diverse oxidation states in their lattice structures. The photochemically synthesized ZnFe-PBAs exhibited significantly enhanced Cs⁺ adsorption capacities compared to those of conventional materials. Comprehensive characterization techniques, including X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, were employed to assess the physicochemical properties of the ZnFe-PBAs and examine their structural changes during Cs⁺ adsorption and desorption. The results revealed that the ZnFe samples exhibited distinct structural transformations, with ZnFe-W showing rapid structural changes that facilitated rapid Cs⁺ adsorption and desorption. In contrast, ZnFe-Y maintained a stable cubic structure throughout the process. Adsorption isotherm and kinetic studies confirmed that ion exchange with K⁺ is the primary mechanism of Cs⁺ adsorption, and it was deduced that the desorption efficiency varied with the choice of desorption solution. This study highlights the importance of understanding structural changes during Cs⁺ removal and provides insights into designing more efficient and reusable adsorbents. These findings suggest that ZnFe-PBAs have strong potential for ¹³⁷Cs removal in simulated nuclear waste environments and a promising strategy for radioactive contaminant management.