Inactivation of Escherichia coli on immobilized TiO2 using fluorescent light

There are many circumstances where it is necessary or desirable to remove or to kill microorganisms found on surfaces. In this paper, we present evidence of the photocatalytic inactivation of Escherichia coli (ATCC8739) cells deposited on TiO2 loaded membrane filters during irradiation with fluorescent light. The TiO2 selected was the photocatalyst PC105, with loadings ranging from 520 to 15,590 mg m−2. Irradiation was produced by eight 8 W lamps with visible light, and UV (290–400 nm) at 0.05–0.12 W m−2 intensity. E. coli inactivation as a function of time was monitored for up to 120 min. In the presence of fluorescent light, the inactivation rate of E. coli increased with a decrease in the TiO2 loading, giving the best results at 520 mg m−2 loading, with complete inactivation achieved after 2 h of exposure. TiO2 loading higher than 6236 mg m−2 resulted in decreased inactivation. SEM images of photocatalyst and bacteria show that increasing the particle contact with the bacteria enhanced the disinfection process. Thus excess TiO2 did not enhance the antibacterial effect, once maximum cell–photocatalyst contact had been achieved.