High-Performance thin film composite forward osmosis membrane on tannic Acid/Fe³⁺ coated microfiltration substrate

Herein, a triple-layer thin film composite (TFC) forward osmosis (FO) membrane was fabricated via interfacial polymerization (IP) of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on a tannic acid-Fe³⁺(TA-Fe³⁺)-coated microfiltration (MF) PVDF substrate. The polyphenol interlayer is prepared by coordination of TA using ferric (Fe³⁺) ions as cross-linker on the MF substrate. The effect of the TA-Fe³⁺ interlayer on the hydrophilicity, structure and roughness of the TFC-FO membranes was entirely investigated by using several instrument characteristics. The TA modified TFC(TA-TFC) membrane presented approximately tripled water flux when compared to the control TFC membrane without TA modification. Specially, a membrane perm-selectivity or reverse salt flux (J_s) to water flux (J_w) (J_s/J_w value) ratio of 0.10 g/L was obtained for the TA modified composite membrane where DI water and 1 M NaCl were used as feed and draw solutions, respectively. In addition, this approach is versatile, facile, green, and easy to scale-up, giving controllable chemical and physical structures to TFC-FO membranes.