Antifouling and Antimicrobial Coatings for Water Purification Membranes

Y-H. Na
IBM Almaden Research Center,
United States

Keywords: water technologies

Summary:

Membrane treatment processes, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO), have been widely used to purify water as a result of their simple operation and competitive energy efficiency. However, membrane fouling (surface deposition and pore clogging) by inorganic salts, organic and biological substances remains the main obstacle in the use of the membrane technology, causing significant flux decline and increased operational costs. Here at IBMÂ’s Almaden Research Center, we have developed a series of highly water permeable, hydrophilic coating materials that demonstrate significant anti-fouling and antimicrobial efficiency during UF, NF, and RO processes. Bifunctional hydrogels were specifically designed for modifying porous UF membranes, and prepared by the photopolymerization of polyethylene glycol diacrylate (PEGDA for antifouling function) and a functional monomer containing ammonium salt (RNH3Cl for antimicrobial function). For dense RO and NF membranes, multi-amine-functionalized hydrophilic polymers were synthesized and covalently grafted onto a polyamide active layer through sequential interfacial polymerization to form ultrathin, fouling resistant coating layer. Very recently, globular-shaped nanogel star polymers comprised of hydrophobic core and hydrophilic arms have been synthesized and applied onto a variety of commercial membranes including porous UF and dense RO through a molecular self-assembly process. These functional materials forming molecular-layered thin coatings completely changed the wetting property of membrane surfaces, and showed excellent antifouling efficiency in cross-flow filtration tested using an oil-water emulsion or a bovine serum albumin (BSA) solution as the feed. The antimicrobial activity of the anti-fouling materials was also demonstrated by a case study employing E-coli. In the presentation, the chemical compositions, molecular architecture, and the functions of the novel anti-fouling materials will be thoroughly discussed.