Although chlorination disinfection is effective in sterilizing waterborne pathogens, the production of carcinogenetic by-products has raised public concerns. TiO2-mediated photocatalysis isconsidered as an enviormentally frendly disinfection method. SinceTiO2is only activated by UV-light, the TiO2 activity has been modified by doping metal/non-metal materials in response to visible-light irradiation for water disinfection. Mostly, E. coliis conducted as a model pathogen in photocatalytic disinfection. Apart from E. coli, Candida albicans(C. albicans) and Mycobacteriumavium(M. avium) are toxic waterborne pathogens that are challenging to be sterilized. Moreover, C. albicanshas been ranked as the fourth cause about the bloodstream infection of the human. However, no literature reports the effects of visible-light-responsive photocatalyst on photocatalytic disinfection of bothpathogens. The aims of this study were to evaluatethe performance of visible-light-responsive TiO2composites (N-TiO2, C-TiO2, N-T-TiO2,andPd-C-TiO2) on photocatalytic disinfection of C. albicans and M. avium, to investigatethe model for photo-disinfection kineticdata, and to identifythe antibacterial mechanism. The key parameters affecting disinfection efficiency were light intensity, initial microbial concentrationand photocatalytic loading. SEMand TEMwere used to investigate the change of cell surface and morphologies, and Atomic Force Microscope and transmission X-ray microscopy were used to examine the biophysical and structural properties during the disinfection. Results showed that the TiO2composited intensely inhibited the microbial growth. The Lin modelcan be used to describe thekinetics ofphotocatalytic disinfection process. TiO2composites adsorbed on the surface of C. albicansandM. aviumwithin 2 hsubsequently, indicating that TiO2composites-mediated photocatalysis caused seriousdeformation in microbial cells. The internal cellular structure was distortedfollowing the irradiation time. The biochemical properties of damaged cells during the photo-inactivation process were also demonstratedby the leakage of K+, CoA, DNA andprotein. In conclusion, the visible-light-responsive TiO2photocatalysts show high-performance to disinfect water pathogens, which might be a promising alternative for water purification.

Performance and photo-disinfection mechanism of visible-light-responsive tiO2 composites for removal of water pathogen

2019 Fall National Meeting

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