Adsorptive removal of diclofenac sodium from aqueous solution by magnetic COF: Role of hydroxyl group on COF

Covalent organic frameworks (COFs) with great application potential in environmental remediation exist as the form of powder, which are difficult to separate and recycle. Two magnetic COFs with good recyclability were prepared through simple impregnation-precipitation method in this study. The prepared magnetic COFs were used for the adsorptive removal of diclofenac sodium (DCF). The introduction of hydroxyl group on magnetic COF (OH-MCOF) could greatly enhance its adsorption amount for DCF, and OH-MCOF was selected to study the effect of adsorption time, initial concentrations, solution pH and ionic strength on its adsorption for DCF, as well as its regeneration and reuse performance were investigated. In this study, the OH-MCOF had a high adsorption capacity for DCF of 203.4 mg/g based on the Langmuir model fitting, and exhibited quickly adsorption for DCF within 30 min. The adsorption efficiency was better than that of most reported adsorbents. Furthermore, the role of hydroxyl group on magnetic COF was highlighted through density functional theory (DFT) and electrostatic potential (ESP) calculation. After 5 cycles of regeneration, the OH-MCOF still maintained the same adsorption amount for DCF, showing good reusability and stability. This study reveals OH-MCOF with high removal and reusability in the further application of environmental remediation.