Enhancing Milk Concentration Process Using Conductive Forward Osmosis Membranes: A Study on Membrane Fouling Mitigation

Mass concentration using conventional forward osmosis (FO) membranes has experienced critical issues including membrane fouling and internal concentration polarization effects. In this study, we designed a conductive FO membrane for milk concentration using the proposed electro-FO system. Specifically, the conductive layer, with a thickness of approximately 1 mu m, was constructed through in situ polymerization of pyrrole on the surface of a symmetric polyoxadiazole-co-hydrazide FO membrane. This unique structural design promoted an FO membrane (named PPy-PODH) with a high water flux (12.7 L m(-2) h(-1)) and exceptional reverse flux selectivity (115,000 L mol(-1)), 3 orders of magnitude higher than those of commercial FO membranes. At an external voltage of 2 V, the conductive FO membrane could maintain a substantial operation (water flux maintained at approximately 6 L m(-2) h(-1)), achieving a high concentration factor of 2.6 toward skim milk. Moreover, high flux recovery ratios of >94.3% were obtained for the PPy-PODH membrane in a "concentration-cleaning" loop experiment, in contrast to 55% for the commercial FO membrane. Overall, this study presents a promising strategy to achieve efficient mass concentration using conductive FO membranes coupled with an electro-FO system.