Enhancing the antifouling performance of surfactant-contaminated brackish water in the reverse osmosis process through a super-hydrophilic layer

Membrane fouling during the reverse osmosis (RO) process significantly deteriorates treatment efficiency and increases operational costs, especially in treating wastewater contains surfactants. In this study, to alleviate membrane fouling, we coated iron-tannic acid (Fe-TA) in top and interlayer of RO membrane (Fe-IP-Fe) via a two-step modification approach, and investigated the optimized coating parameters as well. Results showed that Fe-TA layer can enlarge the size of polyamide leaf-like structures and provide a stable and effective reaction interface for the interfacial polymerization (IP) process, leading to an increased water flux and rejection rate. Especially, water flux of the Fe-IP-Fe membrane increased by approximately 89.5 % in contrast to the original membrane. Furthermore, anti-surfactant-fouling performance of this novel membrane was evaluated. When treating SDS contained feed, normalized water flux of Fe-IP-Fe membrane was 0.84 after 5 h operation, which is 50.6 % higher than that of the original membrane. The outstanding anti-fouling can be attributed to two factors: (1) Fe-TA as an interlayer facilitates a more uniform and complete structure of the membrane top layer and induces the expansion of the polyamide layer; (2) Fe-TA as a top layer significantly enhances membrane's hydrophilicity and roughness. This study provides valuable references for developing anti-fouling RO membranes. [Display omitted] •An anti-fouling RO membrane with two layers iron-tannic acid (Fe-IP-Fe) was prepared.•Fe-IP-Fe exhibited high hydrophilicity (WCA 13.6°) and uniform membrane surface.•Fe-IP-Fe showed high rejection (92.1 %) and water flux (29 L/m2∙h)in surfactants.•XDLVO theory showed hydrophobic interaction is important in Fe-IP-Fe’s anti-fouling.