Synergistic Effect of Atmospheric-pressure Plasma and TiO₂ Photocatalysis on Inactivation of Escherichia coli Cells in Aqueous Media

Atmospheric-pressure plasma and TiO₂ photocatalysis have been widely investigated separately for the management and reduction of microorganisms in aqueous solutions. In this paper, the two methods were combined in order to achieve a more profound understanding of their interactions in disinfection of water contaminated by Escherichia coli. Under water discharges carried out by microplasma jet arrays can result in a rapid inactivation of E. coli cells. The inactivation efficiency is largely dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N₂, He and air microplasma arrays, O₂ microplasma had the highest activity against E. coli cells in aqueous solution, and showed >99.9% bacterial inactivation efficiency within 4 min. Addition of TiO₂ photocatalytic film to the plasma discharge reactor significantly enhanced the inactivation efficiency of the O₂ microplasma system, decreasing the time required to achieve 99.9% killing of E. coli cells to 1 min. This may be attributed to the enhancement of ROS generation due to high catalytic activity and stability of the TiO₂ photocatalyst in the combined plasma-TiO₂ systems. Present work demonstrated the synergistic effect of the two agents, which can be correlated in order to maximize treatment efficiency.