Biofouling resistance of polysulfobetaine coated reverse osmosis membranes

• The polymer brushes were successfully grafted from the surface of RO membranes.
• The modification with pSBMA provides densely packed, regular length polymer chains.
• Very stable hydration shell on the monomer segments within the polymer chain was formed.
• Modified membranes showed a minimum of at least 4 times biofouling improvement.
• Modified membranes still maintaining competitive permeation flux and rejection properties

Although reverse osmosis technology appears to be maturing, several major challenges remain including membrane fouling. The most problematic type of fouling is biofouling because even small amounts of microorganisms that escape pretreatment processes can colonize the system, multiplying the problem at the membrane surface. To address this issue we have created an industrially attractive process suitable for the grafting of polysulfobetaine onto commercially available reverse osmosis membrane surfaces to create an anti-fouling coating. Attachment of coating components was confirmed using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Water contact angle (WCA) and transmission electron microscopy (TEM) then illustrated that the polysulfobetaine coating increased both the hydrophilicity and smoothness of the membrane surface. This modification resulted in at least 80% reduction in microbial abundance at the surface in both aquaria-based static tests and hydrodynamic cross-flow filtration tests while exhibiting flux and salt rejection comparable to controls. The potential applications of this technology include sea water reverse osmosis membranes and alternative feed water sources.

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