(486e) Zwitterions Coated Hollow Fiber Membranes with Enhanced Antifouling Properties for Osmotic Power Generation from Municipal Wastewater

The rapid increases in energy consumption and CO₂ emissions have accelerated the exploration of renewable and green energy. Among them, osmotic energy released from the mixing of water streams with different salinities via pressure retarded osmosis (PRO) has attracted global attention owing to its abundance and renewability. Two factors primarily affect the productivity of a PRO process; namely, the PRO membrane and the feed pair. An ideal PRO membrane requires a high water permeability, high salt rejection, low concentration polarization, high mechanical strength, and minimal fouling tendency. In case of feed pairs, in addition to the conventional pair of river water and seawater, the feed pair of concentrated reverse osmosis (RO) brine and wastewater from municipal recycle plants has received great attention because it has a higher salinity gradient and can potentially produce a higher power density. In addition, this new feed pair may add extra values such as lowering the overall energy consumption for RO, diluting the seawater RO brine for ecologically-friendly disposal, and saving some seawater pretreatment costs.

However, fouling on PRO membranes leads to severe declines in water flux and power density because their porous substrates are facing the wastewater feed. Thus, inorganics, organics and microorganisms in the wastewater are prone to depositing on the substrate surface and even in its pores. In order to reduce the fouling propensity, coating the substrate surface of PRO membranes with zwitterionic materials proves to be an effective way. In our work, 2-methacryloyloxyethylphosphorylcholine (MPC), is modified and grafted onto the polydopamine (PDA) coated poly(ether sulfone) (PES) hollow fiber substrate. Both the synthesis and surface coating of MPC are simple and straightforward. Compared with the pristine PES and PES-PDA substrates, the MPC modified substrate (PES-PDA-MPC) exhibits high resistance to protein adsorption as well as bacteria adhesion. By using a state-of-the-art thin-film composite poly(ether sulfone) (TFC-PES) hollow fiber membrane as the control for power generation, the power density of the TFC-PES-PDA-MPC membrane can achieve as high as 7.7 W/m² while the unmodified one has only 6.0 W/m² after 3 hâ??s PRO tests. In conclusion, the osmotic power generation of PRO membranes can be significantly sustained by modifying the membrane surface with zwitterions.