Efficient removal of diclofenac sodium from aqueous environments by magnetic ionic covalent organic frameworks based on polydopamine: Adsorption performance and mechanism study

In recent years, ion covalent organic frameworks (iCOFs) have shown excellent adsorption performance in the removal of non-steroidal anti-inflammatory drugs (NSAIDs), but powdered iCOFs are faced with problems in separation and recovering from solution and are prone to environmental pollution. In this work, polydopamine (PDA) was used as the mediated coating, Fe 3 O 4 as the magnetic nucleus, and iCOFs consisting of benzene-1,3,5-triscarbaldehyde (BT) and 1,3-diaminoguanidine hydrochloride (DG Cl ) as organic ligands were in-situ grown on the surface of the PDA coating by Schiff base reaction, resulting in a magnetic nanocomposite (Fe 3 O 4 @PDA@BT-DG Cl ) with a coral-like structure. The adsorption kinetics and adsorption isotherms showed that the adsorption behavior of diclofenac sodium (DS) on Fe 3 O 4 @PDA@BT-DG Cl followed the pseudo-second-order kinetic model and Langmuir model, and the maximum adsorption capacity could reach up to 420.17 mg g −1 (25 ℃, pH 5). The adsorption of DS on Fe 3 O 4 @PDA@BT-DG Cl was dominated by electrostatic interactions, along with hydrogen bonding, π-π interactions, and ion exchange, according to the analysis of the adsorption mechanism. The Fe 3 O 4 @PDA@BT-DG Cl consistently maintained high adsorption efficiency after six adsorption–desorption cycles, making it an efficient adsorbent for the removal of NSAIDs in complex water environments.