Surface characteristics of thin film composite polyamide membranes dictate silver nanoparticle loading efficacy

Silver nanoparticles (AgNPs) have emerged as promising antimicrobial agents for controlling biofilm growth on polyamide (PA) thin film composite membranes. However, the current literature lacks a clear path for leveraging silver functionalization in designing biofouling-resistant PA membranes mainly due to huge variations in the resulting silver loading on the membrane. To help develop a robust procedure for fabricating AgNP-loaded PA membranes, here we investigate the relationship between loading yield and membrane (surface) properties. We selected four commercially available PA TFC membranes (BW 30, SW 30 XLE, AMI H, NF 270) and decorated those with AgNPs using the same functionalization chemistry. As expected, we observed a clear variation in silver loading (in the order of BW 30 > AMI H > SW 30 > NF 270). To elucidate the role of membrane surface properties in determining the silver loading efficacy, we conducted a detailed surface characterization of PA TFC membranes using atomic force microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, streaming potential analysis, and contact angle measurements. Subsequently, we employed multiple linear regression analysis to correlate surface properties with silver loading. Our investigation revealed that oxygen content significantly influences AgNP loading (p < 0.05), more than any other surface characteristics. These results will guide future material selection for reverse osmosis or nanofiltration applications critical in the water sector in short term. Moreover, the insights gained from this work are expected to be pivotal in developing membranes more suitable for fabricating AgNP-loaded antimicrobial membranes.