Study on Sterilization Efficiency of Non-thermal Plasma Air Cleaning Device

摘要

The non-thermal plasma (NTP) air cleaning device employing needle-matrix-to-plate corona discharge was adopted to inactivate airborne bacteria. Sterilization experiments with different conditional parameters were carried out to improve the sterilization efficiency. In respect of air speed, the optimal value under different applied voltage of both negative and positive corona discharges is about 0.5 m/s. Under the same applied voltage, positive corona discharge has a higher sterilization efficiency than negative corona discharge; while the latter has wider applied voltage range and more stable discharge characteristic. After 10 min sterilization by positive or negative corona discharge, indoor bacteria number can fulfill the Hospital Disinfection and Sanitation StandardⅡ(GB15928－1995) (less than 200 cfu/m3). After 40 min sterilization, the best sterilization efficiency is more than 90%. With the same discharge mode, the sterilization efficiency increases with increasing treatment time and applied voltage. In addition, the scanning electron microscopy (SEM) were used to take photos of bacteria which was treated by 6kV applied voltage of positive corona discharge; the morphological differences between the original bacteria and treated bacteria were observed and the microbe sterilization mechanism was discussed. It was analyzed that reactive particles including charged particles, free radicals and ozone (O3) play significant roles in the course of air bacteria sterilization; besides, fine particles can be trapped by discharge reactor where they are bombarded by high-energy particles, which contributes to higher sterilization efficiency.