Polydopamine-copper spacers improve longevity and prevent biofouling in reverse osmosis

Abstract

Reverse Osmosis (RO) is a promising technology that will increase access to clean and safe water sources throughout the world. However, the impact of RO filtration of natural waters is severely hindered by biofouling. Formation of complex biofilms on RO membranes dramatically decreases output due to release of extracellular polymeric substances (EPS) by the microorganisms. We present a polydopamine-copper (PD-Cu) coating for RO feed spacer materials to prevent biofouling and enhance longevity of Cu ions. The following spacers were tested in a continuous flow bench scale RO system: (1) Polypropylene (PP) feed spacers coated with PD-Cu, (2) a pristine PP, control spacer, (3), a PD control spacer and (4) a Cu control spacer. Results showed the PD-Cu spacers exhibited higher Cu ion chelation, retaining 71 + 2% more Cu ions compared to a Cu-only spacer after 13 h. In a stirring beaker, PD-Cu spacers lost loosely attached Cu ions until the optimum Cu concentration was achieved, approximately 30.6 + 0.3% of total composition, within 6 h, and the remaining Cu ions bonded with PD covalently. In addition, PD-Cu spacers showed a 17.5% higher permeate flux and a 58% biofilm biovolume decrease as compared to a pristine spacer over 24 h.