Improving the antifouling properties of anion exchange membrane by reducing the adhesion force between membrane and foulants via construction of zwitterionic surface nanolayer

Abstract

Membrane fouling is a critical challenge that must be addressed for the effective application of electrodialysis in wastewater treatment. In this study, zwitterionic surface nanolayer was constructed on anion exchange membrane (AEM), which significantly reduced the adhesion force between the membrane surface and foulants, thereby improving the antifouling properties of the membrane. Among the modified membranes, the best-performing AEM-PDA-SBMA and AEM-PDA-MPC exhibited low adhesion forces to the model foulant of only 0.465 nN and 0.499 nN as measured by AFM, respectively. This was primarily attributed to the reduction in hydrophobic interactions, with a decrease in electrostatic interactions also contributing to the overall effect. In the electrodialysis desalination fouling experiments, the membrane energy consumption of the zwitterionic modified membranes was only 7.76 % and 9.35 % of that of the unmodified membrane. Additionally, the total energy consumption was reduced to 44.22 % and 45.57 %, respectively, while maintaining high current efficiency (>91 %). The long-term stability of the membrane was verified through cyclic electrodialysis experiments. Fouling analysis demonstrated that most of the fouling on the modified membrane was reversible, but a small amount of irreversible fouling was a potential threat. This study quantified the antifouling properties of membranes by measuring the adhesion force between the membrane surface and foulants, providing valuable insights into the interaction mechanisms involved in membrane fouling and offering guidance for the development of effective antifouling strategies.