Exploration of interaction mechanism and removal performance of polystyrene nanoplastics with covalent organic framework: experimental and theoretical study

Nanoplastics pollution in the environment has attracted heightened attention due to the potential for nanoplastics to adsorb and combine with other pollutants to increase their toxicity and endanger human health. Therefore, there is an urgent demand for effective strategies to remediate nanoplastics contamination in aquatic systems. In this study, COF was experimentally used to remove nanoplastics for the first time. TAPB-TPA COF was prepared by ultrasonic synthesis method using 1,3,5-tris (4-aminophenyl) benzene (TAPB) and terephthaldehyde (TPA) at ambient temperature and pressure. The effects of pH, adsorbent dose, polystyrene nanoplastics (PSNPs) concentration, interfering ions, and environmental samples (river water, sewage and seawater) on the removal of PSNPs were investigated. A removal efficiency of 99% was attained within two hours when the dose of TAPB-TPA COF was 0.3 g/L. The experiments and density functional theory (DFT) calculations proved that electrostatic attraction between TAPB-TPA COF and PSNPs was the main adsorption mechanism, accompanied by weak chemical interactions. The maximum adsorption capacity of TAPB-TPA COF for PSNPs approached 185 mg/g and the regenerated adsorbents still had good removal performance. This work demonstrated the feasibility of COF as an adsorbent to remove nanoplastics and provided theoretical support for water remediation.