Piezoelectric reverse osmosis (RO) membrane: Fabrication and anti-fouling effect

Abstract

In this study, a novel piezoelectric RO membrane with vibrating mechanism when exposed to an electric field was developed. The vibration due to the piezoelectric effect can disturb the concentration polarization layer on the membrane surface and minimize membrane fouling. Polyvinylidene fluoride (PVDF) which has piezoelectric properties was selected as the porous substrate for a thin film composite (TFC) polyamide RO membrane in this study. Electrical poling was performed to enhance the piezoelectric properties of the PVDF substrate. RO membranes fabricated via interfacial polymerization using different PVDF substrates (i.e., with and without pre-wetting the PVDF substrate, with and without polyethylene terephthalate (PET) non-woven fabric support (denoted as NWF and no-NWF, respectively), with and without electrical poling) were systematically investigated. The results indicated that RO membrane fabricated on poled PVDF-NWF substrate shows reasonable pure water permeability of ∼2 LMH/bar and sodium chloride (NaCl, 2000 ppm) rejection of ∼98.9 % when tested at 15 bar. In the accelerated fouling study using colloidal silica particles (∼20 nm in diameter, 200 ppm with background of 2000 mg/L NaCl), when the RO membrane fabricated using both unpoled and poled PVDF-NWF substrates were excited with AC signal, membrane fouling was significantly reduced. These findings suggested that electrical poling may not be necessary for such piezoelectric RO membrane.