Improving fouling resistance of thin-film composite polyamide reverse osmosis membrane by coating natural hydrophilic polymer sericin

• Natural hydrophilic polymer sericin was coated on the surface of TFC RO membrane.
• Membrane surface hydrophilicity was improved and negative charge was enhanced.
• Membrane surface morphology was smoothed.
• Membrane pure water permeability and salt permeability coefficient were decreased.
• Modified membrane showed improved fouling resistance to BSA.

In this study, a commercial thin-film composite aromatic polyamide reverse osmosis membrane was modified through coating a surface layer of natural polymer sericin for improved antifouling property. The deposition of sericin on the membrane was carried out through dip-coating followed by in situ cross-linking and was confirmed by ATR-FTIR spectroscopy. The changes of surface charge, hydrophilicity and roughness that resulted from the sericin application were analyzed using zeta-potential analysis, contact angle measurement and atomic force microscopy, respectively. The separation performance was evaluated through cross-flow permeation tests. It was found that the sericin-coated membrane showed improved surface hydrophilicity, enhanced surface negative charge, smoothed surface morphology, and decreased pure water permeability and salt permeability coefficient. The results of fouling experiments with bovine serum albumin aqueous solution revealed that the fouling resistance of the reveres osmosis membrane could be effectively improved by coating sericin surface layer. Although the initial flux of the modified membrane was lower than that of the unmodified membrane under the same operating pressure due to the additional hydraulic resistance, the rate of flux decline slowed after modification due to the mitigation of foulant deposition on the membrane surface and compensated for the initial flux decline within 40 h.