Comprehensive insights into non-steroidal anti-inflammatory drugs adsorption by magnetic ionic covalent organic framework: Kinetics, isotherms, and mechanisms

Abstract

Ionic covalent organic frameworks (iCOFs) have shown promise in non-steroidal anti-inflammatory drugs (NSAIDs) removal, but their recycling from solutions remains challenging. In this study, the development of a novel magnetic iCOF (M–TDiCOF) based on Schiff base reaction using amino functional group modified NH2-Fe3O4 as a magnetic source was reported. The resulting M–TDiCOF exhibits high adsorption capacity and fast kinetics, and can be easily separated and regenerated. Notably, M–TDiCOF achieves equilibrium adsorption of diclofenac sodium (DCF) within 30 min and shows a higher adsorption capacity under acidic conditions (371.27 mg/g, pH = 5). Kinetics and isotherms studies expose the adsorption of M–TDiCOF for DCF following the pseudo second-order kinetic model and Langmuir isotherm model. The correlation between the physicochemical properties of NSAIDs and the adsorption capacity of M–TDiCOF was illustrated. Moreover, the Independent gradient model based on Hirshfeld partition (IGMH) analysis revealed the interaction sites and the electrostatic potential (ESP) analysis highlighted the significance of electrostatic interactions. Finally, the adsorption mechanisms of M–TDiCOF are systematically confirmed. The abundant functional groups (guanidinium groups, hydroxyl groups, and aromatic groups) of M–TDiCOF facilitate electrostatic interactions, H-bond, π-π interactions, and ion exchange during water purification. Mung bean growth experiments verify the safety of M–TDiCOF system.