Joint Centers of Excellence Program

Efficient High-Performance Membranes for Desalination (Domain 4, Project 1)

This research aims to develop new porous membrane materials for desalination, which exhibit greater durability and antifouling properties than what is currently available on the market. One of the conventional porous membranes used in desalination of water are made up of aromatic polyamides (PA) that can prevent ~99.9% of salt ions from passing through under high pressure while still allowing a significant flux of water. Typical PAs, however, suffer from fouling and it can 1) reduce membrane efficiency, 2) increase the pressure along the membranes, and 3) decrease salt rejection. In order to address these drawbacks, introduction of a crown ether moiety into the polyamide (PA) network to create an antifouling hydrophilic membrane system is one of the most promising approaches. Crown ethers are known to attract and bind Group IA and IIA cations, e.g., Na+, Ca2+, Mg2+, thus making it less susceptible to fouling. Furthermore, crown ethers a good candidate to incorporate into PA membranes for desalination as they will also render the system hydrophilic on account of its bismethyleneoxy (–CH2CH2O–) links. This approach will also allow us to incorporate a library of crown ethers into the system to tune the ring size of the cavity to accommodate the radii of various cations. Once the crown ether binds a series of cations, the positive charge will become evenly distributed over the polymer network on both the surface and internal pores. On account of these positive charges, the network will then repel other cationic ions such as Na+, Ca2+, Mg2+ in water leading to enhanced salt rejection. This hydrophilic system will also reject positively charged organic molecules resulting in improved antifouling properties.