Key roles of electron cloud density and configuration in the adsorption of sulfonamide antibiotics on carbonaceous materials: Molecular dynamics and quantum chemical investigations

Highlights: • A new strategy for clarifying the adsorption mechanisms was proposed. • Antibiotics were adsorbed at a distance of 4–5 Å from the adsorbent surfaces. • Orthogonal configuration is hard to be adsorbed due to easy molecular aggregation. • Increasing the π electron density of adsorption system enhance the interactions. • Electron cloud density and configuration play the key roles in the adsorption. Electron transfer often drives the adsorption, but its role is difficult to determine by traditional experimental methods. In this work, two typical carbonaceous materials, graphene (GPE) and graphyne (GPY) were selected as adsorbents, and three sulfonamide antibiotics, sulfamethazine (SMT), sulfamethoxazole (SMX), and sulfamethizole (SMZ) were used as the model adsorbates. Molecular dynamics simulations and quantum chemical calculations were combined to explore the adsorption behavior and mechanisms. Molecular dynamics results showed that the antibiotic molecules were most likely to be adsorbed at a distance of 4–5 Å from the GPE and GPY surfaces. Subsequently, the energies and electronic information were analyzed based on quantum chemical calculations. The N-atom in the pyrimidine ring of SMT exhibited a stronger electron-donating ability than the O- and S-atoms in the heterocycles of SMX and SMZ, thereby enhancing its interaction with GPE and promoting its adsorption. GPE has a stronger π electron system and conjugation effect compared with GPY, and its triangular electron cloud configuration gives it a stronger adsorption ability. The electron cloud density and configuration played key roles in the adsorption. These results provide fundamental theoretical support for the structural design and optimization of carbonaceous materials and the efficient removal of sulfonamide antibiotics.