Significant Improvement and Mechanism of Ultrasonic Inactivation to Escherichia coli with Piezoelectric Effect of Hydrothermally Synthesized t-BaTiO3

Piezoelectric effect was first used for disinfection. In this process, hydrothermally synthesized nano/micrometer tetragonal-BaTiO3 was selected as the piezo-catalyst which was stressed by ultrasound to generate piezoelectric potential. It was found that the inactivation number of the nano/micrometer tetragonal BaTiO3 exposure or sonication alone within 180 min was 0.30 log and 0.70 log for E. coli in deionized water, respectively, while addition of 2 g tetragonal-BaTiO3 with piezo-activity in the ultrasound system resulted in a 2.72 log inactivation without the input of any additional energy, only by original ultrasound. The latter was 2.72 folds as great as the sum of the two former inactivation numbers. However, addition of cubic-BaTiO3 without piezo-activity only led to a 1.02 log inactivation. And moreover, in the process of serious physical damage and chemical oxidation of cells, substantial leakages of intracellular materials were observed. These great differences not only clearly indicated that the combination of sonication and piezocatalysis possessed a great inactivation potential but also suggested that there was a significant synergistic inactivation effect between piezocatalytic oxidation and sono-mechanical destruction.