Abstract
TiO2 nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method with different controlled morphologies: columnar, granular, and branched structures for the photocatalytic inactivation of Escherichia coli (E. coli) in water. Effects of film morphology and external applied voltage on inactivation rate were investigated. As-prepared films were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and UV-VIS. Photocatalytic and photoelectrochemical inactivation of E. coli using as-prepared TiO2 films were performed under irradiation of UVA light (note: UVA has a low efficiency to inactivate E. coli). Inactivation rate constants for each case were obtained from their respective inactivation curve through a 2 h incubation period. Photocatalytic inactivation rate constants of E. coli are 0.02/min (using columnar films), and 0.08/min (using branched films). The inactivation rate constant for the columnar film was enhanced by 330% by applied voltage on the film while that for the branched film was increased only by 30%. Photocatalytic microbial inactivation rate of the columnar and the branched films were also compared taking into account their different surface areas. Since the majority of the UV radiation that reaches the Earth’s surface is UVA, this study provides an opportunity to use sunlight to efficiently decontaminate drinking water.
Highlights
Nearly 20% of the world’s population lacks clean drinking water [1,2]
E. coli is rapidly killed by UVB and UVC in the absence of the TiO2 films, but most E. coli survives under UVA
TiO2 films did not have any bactericidal effects on E. coli in the dark condition whereas they inactivated E. coli cells strongly by photocatalytic and the photoelectrochemical reaction under UVA
Summary
Nearly 20% of the world’s population lacks clean drinking water [1,2]. With a rapidly increasing world population, this problem is further exacerbated. Titanium dioxide (TiO2) is a non-hazardous photocatalytic material Oxidants generated by such photocatalytic materials are strong enough to inactivate pathogenic microorganisms in water [7]. Wei et al [9] used P25 (TiO2, Degussa) to inactivate E. coli in water They reported effects of particle dosage, light intensity etc. Inactivation efficiency is low because electron-hole (e-h) pairs generated by photoactivation recombine rapidly [7,14] To overcome these problems, several research groups have studied inactivation of pathogenic microorganisms using immobilized TiO2 films [15,16,17,18]. This study describes the effect of three TiO2 film morphologies (columnar, granular, and branched structures) on the efficiency of inactivation of E. coli in water. The effect of applied voltage on the photocatalytic inactivation is investigated
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