Volume 14, No. 3, April 2014, Pages 1028-1037 PDF(1.5 MB)
Effects of Electric Field Strength on an Antimicrobial Air Filter
Gi Byoung Hwang1, Hyun-Seol Park2, Gwi-Nam Bae1, Jae Hee Jung1,3
1 Center for Environment, Health, and Welfare Research, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Korea
2 High Efficiency and Clean Energy Research Division, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Korea
3 Department of Electrical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA, 91125, USA
We investigated the effects of a surrounding electric field (EF) on the performance of antimicrobial air filters coated with natural-product nanoparticles. The filtration efficiency of the control filter increased with increasing EF strength, whereas the filtration efficiency of the antimicrobial filter did not, probably because its original efficiency was already high (> 99%) and non- or relatively weakly charged bacterial aerosols were hardly affected by EF strength. The bacterial deposition profiles through the depth of the antimicrobial filters were evaluated. The bacterial concentration at depths of 0–68 µm was increased by about 30% at an EF of 7.7 kV/cm compared with the concentration at 0 kV/cm. Scanning electron microscopy revealed that at 7.7 kV/cm, but not at 0 kV/cm, the bacteria formed dendrites on the fibers of the filter, and the concentration of bacteria deposited on the fibers at 7.7 kV/cm was two to three times that at 0 kV/cm. In antimicrobial tests, the performance of the antimicrobial filters increased with increasing concentration of antimicrobial nanoparticles, but the effectiveness differed between 0 and 7.7 kV/cm. At an identical nanoparticle concentration, the inactivation efficiency of the antimicrobial filter at 7.7 kV/cm was at most 23% lower than that at 0 kV/cm, because the relative increase in bacterial concentration and dendrite formation in the first layer of the antimicrobial filter at 7.7 kV/cm reduced the surface contact area between the bacteria and the antimicrobial nanoparticles. This study provides valuable information for developing a hybrid air purification system that serves various functions and can be used in an indoor environment.
Electric field (EF); Bacteria aerosol; Antimicrobial filter; Deposition profile in filter.