Plasma-enhanced magnetron sputtering of silver nanoparticles on reverse osmosis membranes for improved antifouling properties

The reverse osmosis process is an efficient water purification technology with comparatively low energy consumption. However, unwanted biofilm formation remains a major challenge for membrane plant operators, and effective fouling control strategies are highly sought for. A material-based antifouling approach is the deposition of silver nanoparticles onto the polyamide layer of thin film composite membranes by plasma-enhanced magnetron sputtering, as described in this study. The particle size and distributions were analyzed from Scanning Electron Microscopy (SEM) images and discussed with the elemental composition of the membrane surfaces derived by X-ray Photoelectron Spectroscopy (XPS). The desalination efficiency of the silver coated membranes was determined by use of a coupon tester, and the antimicrobial effect was verified by inducing a reproducible microbial stress on the membranes with a chemostat. In the presence of silver nanoparticles, which had an average diameter of 30 nm, the biofilm formation of pseudomonas sp. was significantly reduced by 64.6% on average after 14 days of continuous cultivation. A sputtering time of 5 s proved to be successful both in significantly improving the antifouling properties as well as fully maintaining the filtration performance of the membranes.