Design and implementation of Cs/GO/TiO2 nanocomposite for controlling sulfamethoxazole

The persistent presence of sulfamethoxazole (SMX), a widely used antibiotic, in aquatic environments poses significant ecological and health risks. This issue stems largely from its incomplete removal by conventional wastewater treatment processes. In this study, density functional theory (DFT) calculations were employed to investigate the adsorption behavior of hydrated SMX on chitosan/graphene oxide/titanium dioxide (Cs/GO/TiO2) composites. Two adsorption configurations were examined: interaction via the amine (–NH2) group of chitosan and coordination between the isoxazole nitrogen of SMX and TiO2. Electronic and topological properties were analyzed using total dipole moment (TDM), HOMO–LUMO energy gap (ΔE), molecular electrostatic potential (MESP), global reactivity descriptors (GRDs), density of states (TDOS/PDOS/OPDOS), quantum theory of atoms in molecules (QTAIM), and non-covalent interaction (NCI) analyses. The results reveal increased polarity, reduced energy gaps, and notable charge redistribution upon adsorption. The calculated adsorption energies (–2.31 eV and − 3.69 eV) indicate energetically favorable interactions, with relative stability depending on the adsorption site. These findings provide atomic-level insight into SMX–composite interactions and highlight the potential role of Cs/GO/TiO₂ composites in adsorption-based removal of antibiotic contaminants.