Insights into Fouling Control of the Salt-Responsive Membrane across the Entire Filtration–Backwashing Cycle

Ultrafiltration, a key membrane technology for surface water treatment, is highly susceptible to fouling caused by natural organic matter. Herein, a zwitterionic polymeric membrane (<b>ZPM</b>) was fabricated via a two-step protocol. During surface water filtration, <b>ZPM</b> demonstrated high pure water permeance (about 1433 L·m^-2·h^-1·bar^-1) and superior fouling-resistant ability compared with the commercial ultrafiltration membrane. The enhanced fouling control was attributed to the greater hydrophilicity and narrower pore size of <b>ZPM</b>. Molecular dynamics simulations and XDLVO analysis revealed that the reduced values of van der Waals energy during the interaction between foulants and <b>ZPM</b> were the main mechanism. Furthermore, the zwitterionic polymer underwent deformation under a NaCl solution (10 g·L^-1) due to the antielectrolyte effect, causing <b>ZPM</b> to mechanical swelling. This mechanical effect alone can remove 70% of the membrane fouling resistance, comparable to the performance of pure water backwashing. The swelling of <b>ZPM</b> also reduced the membrane pore size, leading to a 56% increase in flux velocity, further removing membrane fouling resistance. This study provides new insights into enhanced membrane fouling control across the entire filtration cycle by implementing a dual strategy that combines high-efficiency membrane material with a cost-effective operational process.