Highly Conductive Ultrafiltration Membrane via Vacuum Filtration Assisted Layer-by-Layer Deposition of Functionalized Carbon Nanotubes

Conductive membranes can offer innovative solutions for membrane fouling control while maintaining enhanced filtration performance. Here, an emerging technique, vacuum filtration assisted layer-by-layer deposition of functionalized multiwalled carbon nanotubes (MWNTs), was used to prepare conductive surfaces on polysulfone (PSf) ultrafiltration membranes. PSf membranes were functionalized with oxygen-containing negatively charged functional groups through oxygen plasma treatment. MWNT-PSf membranes were prepared with 5, 10, 15, and 20 bilayers with amine- and carboxylic-functionalized MWNTs. The prepared membranes were characterized by the thickness, contact angle, and conductivity of the membranes. Scanning electron microscopy images of the membranes confirmed uniform MWNT distribution across the membrane surface. MWNT-PSf membranes exhibited slightly reduced permeability, improved selectivity, and greater conductivity with increasing number of MWNT bilayers and demonstrated almost complete inactivation of Escherichia coli at low applied DC potential (1–3 V). Furthermore, significant (around 99%) degradation of methyl orange during electrofiltration was observed, supporting an expected reduction in organic fouling of the membrane.