Background: The control of biofouling is crucial in the membrane separation process. In the present study, graphene oxide-silver (GO-Ag) nanocomposite was fabricated and incorporated into polycaprolactone (PCL) membrane for the first time to increase its antibacterial properties and reduce its biofouling. Characterization of GO-Ag nanocomposite was done by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy. Also, The PCL/GO-Ag membranes were characterized by XRD, attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), porosity determination, water contact angle measurement, and tensile test. Furthermore, pure water flux (PWF) and bovine serum albumin (BSA) rejection of the *Corresponding author: Tel./Fax: +98 51 38816840, E-mail: mmousavi@um.ac.ir This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/jctb.7478 This article is protected by copyright. All rights reserved. membranes were evaluated. Also, the antibacterial activity of membranes was investigated by diffusion inhibition zone test and plate count of colony-forming units. Results: The results demonstrated that Ag nanoparticles were formed on the GO surfaces. In addition, membranes incorporated with the GO-Ag nanocomposite were more hydrophilic, more porous, and more permeable to pure water while showing a lower protein rejection in the filtration of a BSA solution. Adding the GO-Ag nanocomposite to the PCL membrane increased the inhibition effect against bacteria. The colony counting method confirmed that PCL/GO-Ag membranes had higher antibacterial properties than the pure PCL membrane, and the PCL/1.8% GO-Ag membrane represented the maximum antibacterial efficiency of 90% and 98% against P. aeruginosa and S. aureus, respectively. Conclusion: Overall, by the incorporation of GO-Ag nanocomposite into the PCL membrane, PWF and antibacterial property were augmented while protein rejection dropped.

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