Evaluating the performance of the metal organic framework-based ultrafiltration membrane for nanoplastics removal

Nanoplastics (NPs) have emerged as pollutants with detrimental impacts on human and aquatic health. While commercial ultrafiltration (UF) membranes in wastewater treatment plants can effectively remove NPs, their hydrophobic nature limits water permeability and leads to membrane fouling. Herein, we fabricated polyethersulfone (PES)/polyamide (PA) UF composite membranes using the MIL-101(Cr)-based metal–organic frameworks (MOF) nanoparticles for the removal of two types of NPs (polyethylene and polystyrene) from synthetic wastewater. Results show that the presence of more water channels in MOF particles shortened the pathways for water molecules, thereby increasing water permeability by 22 % over the pure PES/PA membranes. An optimal dosage of 0.2 w/v% achieved a high-water permeability of 1204 L/m2/h/bar and over 99 % removal of both NPs in a crossflow filtration system. The high removal efficiency is due to the electrostatic repulsion between negatively charged membrane surface and NPs, coupled with a sieving mechanism. Furthermore, the flux recovery ratio of over 98 % up to six cycles facilitated by quick wetting of the hydrophilic membrane surface and decreased foulant adsorption, confirms the reusability of the membrane. Additionally, the stability of PA/PES-based composite membranes with evenly distributed nanoparticles with various pH ranges (2–10) also inhibits nanoparticle leaching. Therefore, the findings highlight the potential of MOF-based composite UF membranes in effectively removing NPs from wastewater and achieving high water permeability.