Metal-phenolic network as precursor complex coating for forward osmosis membrane with enhanced antifouling property.

In this study, a multi-functional layer was developed based on the commercially available cellulose triacetate (CTA) forward osmosis (FO) membrane to improve its antifouling property. Tannic acid/ferric ion (TA/Fe3+) complexes were firstly coated as a precursor layer on the membrane surface via self-assembly. Afterwards, the tannic acid/diethylenetriamine (TA/DETA) hydrophilic functional layer was further coated, following Ag/polyvinylpyrrolidone (PVP) anti-bacterial layer was formed in situ through the reducibility of TA to obtain TA/Fe3+-TA/DETA-Ag/PVP-modified membrane. The optimized precursor layer was acquired by adjusting the buffer solution pH to 8, TA/Fe3+ ratio to 4 and the number of self-assembled layers to 5. The permeability testing results illustrated that the functional layer had an insignificant effect on the membrane transport parameters. The TA/Fe3+-TA/DETA-Ag/PVP-modified membrane simultaneously exhibited excellent physical and chemical stability. The coated membrane also demonstrated enhanced anti-bacterial properties, achieving 98.63 and 97.30% inhibition against Staphylococcus aureus and Escherichia coli, respectively. Furthermore, the dynamic fouling experiment showed a 12% higher water flux decrease for the TA/Fe3+-TA/DETA-Ag/PVP CTA membrane compared to the nascent CTA membrane, which proved its excellent antifouling performance. This work provides a feasible strategy to heighten the antifouling property of the CTA FO membrane.

Improving antifouling performance of FO membrane by surface immobilization of silver nanoparticles based on a tannic acid: diethylenetriamine precursor layer for municipal wastewater treatment.

In this study, a facile method for multifunctional surface modification on forward osmosis (FO) membrane was constructed by surface immobilization of AgNPs based on tannic acid (TA)/diethylenetriamine (DETA) precursor layer. The cellulose triacetate (CTA) FO membranes modified by TA and DETA with different co-deposition time (6 h, 12 h, 24 h) were investigated. Results indicated that the TA/DETA (24)-Ag CTA membrane with a TA/DETA co-deposition time of 24 h was identified to be optimal, which attained more hydrophilic. And it had the bacterial mortality of Escherichia coli and Staphylococcus aureus reaching 98.23% and 99.83% respectively and possessed excellent physical and chemical binding stability. Meanwhile, the coating layer resulted in the antifouling ability without damaging the membrane intrinsic transport characteristics. As for synthetic municipal wastewater treatment, the water flux of CTA FO membrane decreased approximately 49% of the initial flux after running for 14 days. In contrast, the flux decline rate of TA/DETA (24)-Ag CTA membrane was about 37%. Furthermore, less foulant deposition and higher recovery rate of water flux was observed for TA/DETA (24)-Ag CTA membrane, implying that the modified membrane effectively alleviated membrane fouling and processed a lower flux decline during municipal wastewater treatment. It was attributed to the enhanced surface hydrophilicity and antibacterial property of the coating layer, which improved antifouling property.