Graphitic carbon for ultrahigh-capacity removal of neonicotinoids in real water systems

The widespread application of neonicotinoid pesticides (NEOs) has caused severe contamination of aquatic environments, posing serious threats to water resources and ecological sustainability. In this study, graphitic micro-mesoporous composite carbon (GMC) was synthesized via template-assisted method and employed for the adsorption of NEOs from water. Structural characterization confirmed that GMC possessed graphitized framework, well-developed micro-mesoporous composite architecture, and abundant functional groups, which enhanced its adsorption performance. The GMC exhibits excellent adsorption performance for NEOs, with adsorption equilibrium achieved within 120 min. Batch adsorption experiments showed that the adsorption kinetics were consistent with both pseudo-first-order and pseudo-second-order models, while the adsorption isotherms followed the Freundlich model. This indicates that the adsorption process is spontaneous, endothermic, and tends toward physical adsorption. The maximum adsorption capacity for Thiamethoxam (THM) was achieved 1421.3 mg/g at pH = 3, whereas that for Nitenpyram (NIM) was obtained 642.7 mg/g at pH = 7, suggesting that the ionization degree of NEOs significantly affects the adsorption performance of GMCs. Five consecutive adsorption-desorption cycles validated the excellent stability and reusability of GMC. Co-existing ions and humic acid (HA) exerted negligible effects on adsorption performance. Furthermore, the GMC exhibits good adsorption performance in multi-pesticide coexistence systems and actual farmland surface water, demonstrating the adaptability of GMC to complex water matrices. This study reveals that the adsorption process of NEOs on GMCs is better described by interactions dominated by physical adsorption, driven by a variety of physical mechanisms, including strong π-π stacking, hydrogen bonding, and hydrophobic interactions. The excellent stability, sustainability, and reliability of GMC indicate its considerable potential for practical applications in water purification and environmental remediation.