An Investigation Into the Influence of Titania–Carbon Nanotube Nanophotocatalysts Into the Filtration Performance of Polyethersulfone-Based Membranes

Abstract

The polyethersulfone/sulfonated polyethersulfone (PES/SPSf) blend is enriched with ionizable sulfonic acid groups rendering a stable polymer system suited for blending nanocomposites using water as a dispersant. PES/SPSf/TiO₂-amorphous carbon nanotubes (aCNT) mixed matrix membranes are prepared via addition of a TiO₂–aCNT/deionized water slurry and precipitated via non-solvent induced phase separation. Membranes' electrostatic and non-electrostatic interactions with charged organic pollutants and membrane–dye interactions are probed using the Liftshitz-acid–base approach. Fluid transport and solute rejection mechanisms are investigated through porosity, pore radius, flux, permeance, dye rejection and fouling propensity. PES/SPSf/TiO₂–aCNT membrane contact angle at 1.6 wt.% TiO₂–aCNT loading reached 35° accompanied by pore radius decrease and a decline in membrane pure water permeability (197.7 for MF0 to 48.5 L.m⁻².h⁻¹ for MF1.6). Membranes had good rejection for cationic azure B (≈90%) and zwitterionic rhodamine B (≈100%) compared to anionic charged methyl orange (MO) (2.0%–10.8%). Major dye removal mechanism was size exclusion, where reactive red 120 (1335.9 g/mol) retention was higher than that of MO (327.4 g/mol). TiO₂–aCNT loading imputes membranes additional cationic charge and electron donor components that enables solute transportation via electrostatic switching mechanism and charge-dependent antifouling for reactive dyes, which are the bulk of textile industry pollution.