Enhancing electric virtual impactor performance with condensational growth and efficient charging for size-selective sampling of fine and ultrafine particles

Abstract

An electric virtual impactor can be used for size-selective sampling of airborne particles by utilizing an electric field to segregate particles based on their size, enabling only particles of a specific size range to be collected. This study utilized a condensational particle growth system to improve the aerosol particle charging efficiency and electric virtual impactor performance. A condensational particle growth system and a corona-needle unipolar charger were used together. Polydisperse particles ranging from 10 nm to 5 μm were grown to bigger droplets and charged to a high charge level in the corona needle charger before drying them in the evaporator. A charge level of more than 50 charges per particle was achieved for sizes of 20, 30, 42, and 55 nm. The highly charged particles were then sampled in the electric virtual impactor. The lower cutoff size of the electric virtual impactor could vary in the range from 30 nm to 1 μm while the upper cutoff size was fixed to 2.5 μm based on inertial separation mechanism. The developed system is expected to be very useful in sampling fine and ultrafine particles under normal pressure conditions, even by setting the particle size range suitable for the sampling purpose.