Functional group influence on uranyl ion adsorption by L-cysteine-grafted graphene oxide: A theoretical study

As a highly toxic radioactive contaminant in nuclear waste, the efficient removal of uranyl ions (UO₂²⁺) presents a critical challenge for sustainable nuclear energy applications. In this study, the effects of various functional groups in L-cysteine grafted graphene oxide (L-Cys-GO) on UO₂²⁺ adsorption were systematically investigated through density functional theory (DFT) calculations. Two distinct L-Cys-GO models were constructed to comparatively analyze the interaction mechanisms between UO₂²⁺ and functional groups, including carboxyl (-COOH), hydroxyl (-OH), thiol (-SH), and amino (-NH₂). The results demonstrate that the synergistic effect between the graphene oxide substrate and L-cysteine significantly enhances uranium adsorption capacity. Theoretical calculations reveal that both the central uranium atom and the axial oxygen atoms of UO₂²⁺ serve as coordination sites, with the coordination between functional groups and the central uranium atom dominating the adsorption process. Among the examined functional groups, the -NH₂ group exhibits superior adsorption capability, achieving a maximum adsorption energy of 558.6 kJ/mol. Notably, L-Cys-GO materials prepared via nucleophilic substitution display superior adsorption performance compared to those synthesized through amide reactions. This study provides a theoretical foundation for the design of effective uranyl ion adsorption materials and holds significant implications for nuclear waste management and environmental pollution remediation.