Density functional theory and EXAFS spectroscopy studies of formamidoxime-intercalated molybdenum disulfide for the removal of Eu(iii) and U(vi)

Abstract

Controlling radioactive pollution is crucial for the sustainable development of nuclear energy. In this study, formamidoxime-intercalated molybdenum disulfide (CH₄N₂O–MoS₂) was prepared to remove Eu(III) and U(VI) from the water environment. The material revealed a spherical structure with a diameter of 0.92 μm. The maximum adsorption capacities of CH₄N₂O–MoS₂ for Eu(III) and U(VI) reached 69.8 mg g⁻¹ and 137.1 mg g⁻¹, respectively. U(VI) and Eu(III) ions can compete for adsorption sites on the surface and between layers of the material, resulting in a lower removal efficiency. Besides, the material can be used to separate U(VI) and Eu(III) owing to the huge difference in adsorption capacity at pH = 3.0. DFT calculations and EXAFS analysis demonstrated that Eu(III) capture depended on interlayer adsorption, surface complexation, and precipitation. The elimination mechanisms of U(VI) were interlayer adsorption and surface complexation. Moreover, Eu(III) and U(VI) were more prone to interlayer adsorption than surface adsorption. This study provides an in-depth insight into the relationship between the structure and Eu(III) and U(VI) adsorption performance of the reported material, thereby guiding the design of novel materials.