Unipolar Charging of Fine and Ultra-Fine Particles Using Carbon Fiber Ionizers

Abstract

A simple and novel unipolar charger using carbon fiber ionizers was developed to effectively charge fine and ultra-fine aerosol particles without the generation of ozone. The particle penetration in the charger was investigated for non-charged, neutralized, and singly charged particles in the size range of 20-200 nm. Particle loss and the intrinsic, exit and extrinsic charging efficiencies of fine and ultra-fine particles were also investigated for non-charged particles at different applied voltages to the charger. Particle penetrations in the charger were nearly 100% for particles larger than 20 nm, irrespective of the initial particle charging state. Particle losses in the charger could be decreased by decreasing the applied voltage to the charger from 4.0 kV to 2.3 kV. The intrinsic charging efficiencies were proportionally increased with the applied voltage, whereas the exit charging efficiencies were almost independent of the applied voltage. Therefore, the extrinsic charging efficiency of the charger becomes higher for the lower applied voltage (2.3 kV), at which about 60% of 20 nm particles were charged. Little (less than 4 ppb) to no ozone was generated under all operation conditions. It can be concluded that the newly developed unipolar charger using carbon fiber ionizers can charge fine and ultra-fine particles at least as effectively as currently available unipolar chargers, but with the major advantage of negligible ozone generation, a highly desirable feature if the charged particles are to be used for chemical or biological analysis.

Capture of Ultrafine Particles Using a Film-Type Electret Filter with a Unipolar Charger

“…3 , and these values were much higher than the corresponding values of approximately 10 12 s m -3 generated by ionizers (Han et al, 2008). Therefore, we can expect the charging efficiency and consequent collection efficiency using a corona discharge to be much higher than those using an ionizer are.…”

Enhanced Antimicrobial Activity on Non-Conducting and Conducting Air Filters by Using Air Ions and Grapefruit Seed Extract

“…We measured the sizes of the bioaerosol particles and found that they most frequently had the same size as the GSE particles . To determine whether the use of air ions on the test filters had an antimicrobial effect, ions were supplied to the filter surface by a carbon fiber ionizer (Han et al, 2008) with a DC power supply and 1 L min -1 of filtered air during 5 minutes, as shown in Fig. 2(c) after exposing the filter to S. aureus.…”

“…In the present study, filters were coated with GSE particles and air ions were also prepared (Han et al, 2008) and injected onto the filter surface. Simply immersing the filter media in the GSE solution can cause a significant pressure drop.…”

Performance of wearable ionization air cleaners: Ozone emission and particle removal

“…For the same level of ionization, a carbon fiber ionizer typically requires lower voltage than metallic cathodes of corona discharge because the diameter of carbon fibers is much smaller (about 5-10 mm) than that of metallic cathodes. Lower voltage applied to carbon fibers is sufficient to trigger ionization at the tip of carbon fiber cathodes; while, the electric field from the applied voltage is not high enough to induce unnecessary ozone reactions (shown in Equations (6) and (7)) (Han et al 2008;Han et al 2009). This may explain the negligible ozone emissions by AC3 and AC4.…”