Disinfection mechanism of E. coli by CNT-TiO2 composites: Photocatalytic inactivation vs. physical separation

Abstract

Magnetic carbon nanotube (MCNT) composites with titanium dioxide (TiO₂) have an enhanced photocatalytic disinfection efficiency (i.e. higher disinfection rate) and better applicability (i.e. solar light applicability and catalyst separation using its magnetic property) than bare TiO₂ and/or MCNT. However, the role and mechanism of MCNT in the disinfection process are still unclear. Therefore, this study aimed at investigating the disinfection mechanism of Escherichia coli using MCNT-TiO₂ nanocomposites under various conditions (i.e. the presence and absence of light and reactive oxygen species scavengers, and different MCNT-TiO₂ ratio) and photocatalytic disinfection models. The results showed that (i) MCNT and its nanocomposites with TiO₂ had much higher disinfection efficiencies than bare TiO₂, (ii) the physical bacterial capture was the dominant disinfection mechanism, (iii) the higher disinfection rate was found at an optimum MCNT:TiO₂ ratio of 5:1 under the tested experimental conditions, (iv) hydroxyl radical (OH) was the influencing reactive oxygen species on the photocatalytic disinfection using MCNT-TiO₂, and (v) good correlation between experimental parameters (i.e. carbon contents, surface area and concentration of MCNT-TiO₂) and the contribution rate of physical and photocatalysis reactions. The finding from this study and the methods proposed herein are essential for understanding the photocatalytic disinfection processes using TiO₂ and its carbonaceous nanocomposites, which can promote the application of photocatalytic disinfection process.

Keywords: Disinfection; E. coli; Magnetic carbon nanotube; Photocatlaysis; Titanium dioxide.