Antifouling and Chlorine-resistant Ultrathin Coatings on Reverse Osmosis Membranes

Technology #16133

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Antifouling zwitterionic coatings applied onto commercial RO membranes via iCVD. a,b, Cross-sectional SEM image of (a) bare and (b) iCVD coated RO membrane. c, AFM scan of coated membrane and (inset) bare membrane. d, N(1s) XPS high resolution scan of the iCVD P4VP as- deposited (blue) and post-functionalized by PS (red), demonstrating full conversion of pyridine to zwitterion. e, Salt rejection of bare and coated membranes. The comparable values of salt rejection indicate that the coating leaves the thin selective layer of the delicate RO membranes intact. f, Water flux through bare and coated membranes. Membranes coated with 30-nm functionalized copolymer 1 maintain 86% of the original water flux.
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Inventors
Professor Karen Gleason
Department of Chemical Engineering, MIT
External Link (web.mit.edu)
Rong Yang
Department of Chemical Engineering, MIT
Managed By
Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Antifouling and Chlorine-Resistant Ultrathin Coatings on Reverse Osmosis Membranes

US Patent Pending 2014-0299538
Publications
Synergistic Prevention of Biofouling in Seawater Desalination by Zwitterionic Surfaces and Low‐Level Chlorination
Advanced Materials, March 19, 2014, p. 1711-1718

Biofouling refers to the undesirable attachment of organic matters, biomolecules and microbes on submerged surfaces, which diminishes the device performance. The inventors have developed a chlorine-resistant, Zwitterionic polymer coating which, when applied to commercial reverse osmosis (RO) membranes, will provide excellent means to combat biofouling of these surfaces. 

Applications

The invented Zwitterionic coating applied on commercially available RO membranes has excellent potential of providing chlorine-resistant, antifouling surfaces. This technology is very useful in the water desalination industry.

Problem Addressed

Other antifouling coatings have been applied to various surfaces by processes that involve the use of harsh solvents. These solvents may cause damage to delicate substrate (such as RO membranes). The invented copolymer chemistry is the first-ever ultralow fouling coating developed by initiated chemical vapor deposition (iCVD), a solvent-less technique. Additionally, while fouling from membrane use can be reduced by remediation with chlorine, exposure to water with even a few parts per billion chlorine significantly degrades normal membrane performance. This polymer coating is chlorine-resistant, lowering the number of additional processing steps and, in turn, operational costs. 

Technology

The inventors have developed a novel antifouling chemistry that is also chlorine-resistant. The coating derives from poly(4-vinylpyridine) (P4VP), which has been used as the precursor for antimicrobial coatings. Quaternization is performed on P4VP to obtain a positively-charged surface that is able to penetrate and degrade cell membranes of various microbes. P4VP is reacted with 1,3-propane sultone to obtain a zwitterionic chemistry with a balanced surface charge that removes killed bacteria and enhances the surface’s antimicrobial activity. Divinylbenzene (DVB) copolymerizes with 4VP and renders the copolymer resistant to the oxidation of chlorine. Ultrathin P4VP coatings are put down on commercially available TFC membranes via iCVD. Since surface tension and de-wetting are avoided, this all-dry process conforms to the geometry of the underlying substrate.

Advantages 

  • Ease of application, excellent control and surface conformance via iCVD technique
  • Solvent free and room temperature deposition process is unlikely to damage delicate RO membrane
  • Zwitterionic copolymer film provides ultralow biofouling surface
  • Chlorine-resistant coating enhances membrane maintenance