The anti-biofouling properties of thin-film composite nanofiltration membranes grafted with biogenic silver nanoparticles

• Biogenic silver nanoparticles (AgNPs) were grafted on TFC NF membranes.
• Biogenic AgNPs enhanced hydrophilicity and water flux of TFC NF membranes.
• Better membrane stability was achieved with grafted biogenic AgNPs than chemical AgNPs.
• Biogenic AgNP grafted NF membrane shows better antibacterial ability.

Biofouling is still one of the most challenging issues of nanofiltration. One of the practical strategies to reduce biofouling is to develop novel anti-biofouling membranes. Herein, biogenic silver nanoparticles (BioAg0-6) with the averaged diameter of only 6 nm were firstly grafted on the surface of polyamide NF membrane. The effect of grafted BioAg0-6 on the performance of thin-film composite (TFC) NF membranes was systematically investigated with a comparison to the grafted chemical AgNPs. BioAg0-6 grafted membrane (TFC-S-BioAg) increased the hydrophilicity of the TFC membrane and water permeability, while maintaining the relatively high salt rejection. The result of silver leaching experiment indicated that the grafted BioAg0-6 had a better stability on the membranes, the ratio of remained silver in the TFC-S-BioAg membrane was 95%, after soaked in pure water for 50 days. After 4 month immersion, the rejection of TFC-S-BioAg membrane remained more than 90% of initial rejection. The results of disk diffusion test revealed that both of TFC-S-BioAg membrane and TFC-S-ChemAg membrane showed effective anti-bacterial ability to inhibit Pseudomonas aeruginosa and Escherichia coli growth, the TFC-S-BioAg membrane showed more excellent and longer lasting antibacterial property. Therefore, BioAg0-6 grafted TFC membranes could be potential as an effective strategy to decrease biofouling in nanofiltration process.