Fabrication of granular three-dimensional graphene oxide/UiO-66 adsorbent for high uranium adsorption: Density functional theory and fixed bed column studies

This study presents a thorough investigation of the novel application of graphene oxide (GO) modified with melamine formaldehyde to fabricate granular three-dimensional GO (3D-GO), followed by the introduction of UiO-66 doping (3D-GO/U) for high uranium (U) adsorption. The U(VI) adsorption isotherms revealed that 3D-GO/U-10 with 10 % UiO-66 incorporation exhibited an impressive adsorption capacity of 375.5 mg g^–1 and remained high U(VI) sorption performance in wide pH range. The introduction of UiO-66 to 3D-GO (3D-GO/U-10) led to the deagglomeration of the UiO-66 particles. The in situ surface-enhanced-Raman-spectroscopy-analysis and density-functional-theory simulations showed the symmetric metal center site Zr–O₂ on UiO-66 was discovered to exhibit the highest adsorption energy (–3.21 eV) for U(VI) species due to the electrons transfer from the oxygen atom to U(VI) drives the covalent bonding between the symmetric metal center sites Zr–O₂ and U(VI) on 3D-GO/U-10. The 3D-GO/U-10 was regenerated using a 0.1 M Na₂CO₃/0.01 M H₂O₂ solution and achieved up to 89.7 % U(VI) removal in the 5^th cycle. The continuous flow column experiments results revealed 3D-GO/U-10 can regenerate and maintain a U(VI) removal capacity of ∼76 % for up to 4 cycles column experiments. Therefore, 3D-GO/U-10 exhibits great potential for removing U(VI) from water bodies.