In situ surface functionalization of reverse osmosis membranes with biocidal copper nanoparticles

Biofouling may lead to severe operational challenges that can significantly impair membrane desalination processes. In recent years, copper-based nanoparticles (Cu-NPs) have gained increased attention as a potentially viable anti-biofouling agent in membrane processes, due to their strong antibacterial activity and relatively low cost. This study presents a novel and facile method to attach biocidal Cu-NPs on the surface of a thin-film composite reverse osmosis membrane. Herein, we suggest a method for membrane surface functionalization with Cu-NPs that is performed without disassembling the membrane module, which highlights its practicality and potential application for reverse osmosis desalination plants. The loading of Cu-NPs on the membrane was confirmed both by scanning electron microscope imaging and X-ray photoelectron spectroscopy analysis, indicating that the deposited nanoparticles were composed of either metallic copper or copper-oxide. The impact of the in situ Cu-NP modification on membrane transport properties was found to be minor, with only a slight increase of the water and salt permeability. Furthermore, except for a slight increase in hydrophobicity, the modified membrane exhibited surface properties comparable to those of the pristine membrane. Finally, the in situ formed Cu-NPs imparted a strong antibacterial activity to the membrane surface, leading to 90% reduction in the number of attached live Escherichia coli bacteria on the modified membrane compared to the pristine reverse osmosis membrane. This study demonstrates that in situ grafting of Cu-NPs on reverse osmosis membranes is a potential alternative to reduce biofouling. © 2016 Elsevier B.V. All rights reserved.

In order to utilize biocidal Me-NPs for biofouling mitigation in membrane desalination, a viable procedure for repeatable loading of the antibacterial agent inside the membrane module must be developed. In our previous work, we demonstrated the potential feasibility of in situ formed biocidal Ag-NPs on TFC RO membrane and the rendered antibacterial activity [29]. Here, we extended the in situ formation procedure for surface modification of TFC-RO membrane with biocidal Cu-NPs. Cu-NPs have a much lower cost than Ag-NPs, but still have a strong antibacterial activity. We succeeded in achieving in situ formed Cu-NPs that coated the surface of TFC-RO membranes by a facile procedure that was performed at ambient conditions, and required only two chemicals (copper salt and reducing agent) without an additional NP stabilizing agent. The loading can be performed in situ, implying potential implementation of the method for repeatable loading of Cu-NPs in a desalination plant without disassembling the membrane module. Generally, only a minor impact of the Cu-NP in situ procedure was observed on the transport properties of the membrane. Similarly, the surface properties were generally maintained, although the Cu-NPs in situ modified membrane demonstrated prominent antibacterial activity compared to the pristine membrane. Therefore, we demonstrated here a potentially viable method for loading biocidal Cu-NPs on TFC-RO membranes. Acknowledgments This work was supported by the NSF Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (ERC1449500). This research was also supported by BARD, the United States–Israel Binational Agricultural Research and Development Fund, via a Vaadia-BARD Postdoctoral Fellowship to M.B-S. (Award No. FI [1] M. Elimelech, W.A. 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