Photocatalysis-assisted water filtration: Using TiO₂-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7

A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO₂) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO₂/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope–energy dispersive analysis of X-ray (SEM–EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO₂/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P < 0.05) as compared to TiO₂/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO₂-ceramic and MWCNT/TiO₂-ceramic under fluorescent light was found be 1.45 × 10⁻² min⁻¹ and 2.23 × 10⁻² min⁻¹ respectively. Further, when I–V characteristics were performed for TiO₂/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network. - Highlights: • Coating of vertically aligned MWCNT on ceramic candle filter • Surface orchestration of TiO₂ on MWCNT arrays • I–V characteristic studies are performed under dark and illumination. • Photocatalytic efficiency of TiO₂/MWCNT arrays is determined using E. coli O157:H7. • Proposed a mechanism of bacterial killing due to free radical formation