Kinetics of ultrasonic disinfection of Escherichia coli in the presence of titanium dioxide particles

The ultrasonic disinfection of Escherichia coli was carried out in the presence of anatase-type TiO₂ particles, and the effectiveness of the combination of ultrasonic irradiation with TiO₂ addition was verified. The rate constant was determined from the plot of the common logarithm of the survival cell ratio versus the ultrasonic irradiation time using first-order kinetics. In the absence of particles, the rate constant was proportional to the ultrasonic power. When ultrasonic disinfection was carried out in the presence of TiO₂ particles, which have a radical generation ability, the rate of disinfection was remarkably faster than that in the absence of TiO₂. In the presence of silica particles, which have no radical generation ability, the rate of disinfection was the same as that in the absence of TiO₂. These results suggest that the radical generation ability of TiO₂ appeared as a result of the ultrasonic irradiation. The effect of the amount of TiO₂ on the rate of disinfection was also examined. The rate constant for disinfection in the presence of TiO₂ was saturated to a certain value and was represented using the Langmuir-type equation. The proposed model well describes the effects of the ultrasonic power and the amount of TiO₂ on the rate constant for disinfection.