Theoretical and experimental studies on uranium(vi) adsorption using phosphine oxide-coated magnetic nanoadsorbent

In this study, novel Cyanex-923-coated magnetite nanoparticles (Fe3O4@Cyanex-923) were prepared, comprehensively characterized, and employed for uranium(vi) ion adsorption from aqueous solutions. FTIR and TGA data confirmed that Fe3O4 has successfully gained Cyanex-923 surface functionality. Particle size and morphological studies via DLS, HR-TEM, and SEM showed uniform-dispersed quasi-spherical nanoparticles with a mean diameter of ca. 44 nm. Magnetism measurement data revealed the superparamagnetic properties of the Fe3O4@Cyanex-923 nanoadsorbent. The effect of different experimental settings on the adsorption efficiency was studied to determine the best operational conditions. The experimental results were analyzed using Langmuir, Freundlich, and Temkin isotherms; where the adsorption data obeyed the Langmuir model showing a theoretical adsorption capacity of 429.185 mg g(-1) at 298 K. Kinetics data analysis revealed a fast adsorption process that could reach equilibrium within 60 min and is well-fitted to the pseudo-2nd-order model. Temperature affected the adsorption process and the thermodynamic data indicated that uranium(vi) adsorption was spontaneous and exothermic. Fe3O4@Cyanex-923 nanoparticles displayed a good regeneration behavior over three sequential adsorption-desorption cycles. The Fe3O4@Cyanex-923 nanoadsorbent showed a high uranium adsorption capacity, fast equilibration time, economic nature, good reusability, and easy separation; making it a promising candidate for uranium(vi) removal from nuclear waste streams.