Microfiltration and ultrafiltration membranes have excellent ability to remove contaminants from liquid streams, such as industrial wastewaters. If membranes were more widely used, water quality could be significantly improved. However, membranes suffer from fouling that makes them costly to operate because of high energy requirements. The goal of this research project is to engineer coatings that are regenerable. Regenerable coatings can be applied before filtration, then removed after fouling. Since the coating is easy to remove, all of the foulants on top of the coating will also be removed, and membrane performance will be restored.
The key research question is to determine which coating materials are appropriate. Proteins and polysaccharides are two material classes that have potential because their polymeric nature can lead to good attachment, yet the materials are benign. Some polysaccharide types having a range of size and attachment properties include starches, chitosan, dextran, and glycogen. Proteins include albumins, caseins, collagens, and integrins. Aside from proteins and polysaccharides, synthetic polymers and nanoparticles are also of interest since they can be specifically designed with the membrane coating function in mind. Linear polymers such as polyDADMAC have quaternary amines for positive charge that bind well to negatively charged membranes. Branched polymers like PAMAM dendrimers have a globular structure, reducing attachment points and potentially making them more regenerable. Nanoparticles functionalized with various surface groups are also of interest, where nanoparticle size helps control attachment strength.
The student’s individual project will be to test the attachment and regenerability of various coating materials. The key analytical equipment is an electrokinetic analyzer that allows the student to measure the surface charge of the membranes before and after coating; this is a very sensitive technique and one that students will likely not have previously seen, yet can be mastered in a short time. The student will also perform membrane filtration experiments to test the performance of the coatings at reducing fouling and increasing flux over several backwash cycles.