10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Characterization of an High-Efficiency Electrostatic Precipitator Regarding Particle Size, Aerosols Flow and Particle Concentration
HARALD WIEGAND, Jörg Meyer, Gerhard Kasper, KIT, Germany
Abstract Number: 1544 Working Group: Aerosol Toxicology
Abstract The air-liquid interface (ALI) provides a realistic in-vitro exposure scenario for the deposition of inhalable nanoparticles onto cell cultures for toxicological, pharmaceutical and environmental research. It is hence necessary to provide a reliable and sufficient nanoparticle dose within an acceptable time while achieving the required separation of nanoparticles from the carrier gas. For this purpose an electrostatic cross-flow ALI precipitator capable of exposing cultured human lung cells to nanoparticles is presented.
A specially developed conductivity measurement technique was used to characterize particle deposition rates as it is described in [1]. Apart from its application in toxicological research a precisely characterized ALI precipitator is capable of producing suspension of well-known particle size distribution and concentration.
Experimental In Figure 1A a schematic of the inlet and the deposition zone is shown. Three gas flows are fed into the ALI precipitator.
The aerosol flow consists of polydisperse sodium chloride particles (20-520 nm) which is used as a surrogate aerosol for deposition rate measurements. Following the dispersion of an aqueous solution into air, the particles are charged unipolarly. The humidified flow has a relative humidity of 85 to 95 % to provide suitable conditions for cell culture experiments. In order to guarantee laminar flow conditions a sheathed flow of clean air is used. All three flows are temperature controlled. The particles are deposited in an electrostatic field (1 to 3 kV/cm) directly into the wells (Figure 1A). As the conductivity of the liquid in each well changes proportionally to the quantity of deposited salt the deposition rates can be determined [1]. For particle size dependent experiments a DMA was operated at various voltages to generate a monodisperse salt aerosol. An example of a sized aerosol is given in Figure 1B. The three main peaks at 80 nm, 120 nm and 155 nm correspond to particles in Boltzmann equilibrium carrying one, two and three elementary charges. This conditioning allows a connection between selected particle sizes and their deposition rate.
Results First results of particle deposition characterization indicate a deposition efficiency of about 40 % of the introduced particle mass in the cell culture wells. A sufficiently narrow particle size distribution with a high concentration was generated to complete an experiments in a reasonable time. The bigger particles (>200 nm) could possibly disturb the conductivity measurements, therefore the flow velocity in the precipitation zone has to be carefully selected.
Conclusion A deposition efficiency of about 40 % and the narrow size distribution allows particle size depended deposition rate measurements in a reasonable time. The aim is a precipitator, for which the particle deposition rate can be calculated as a function of particle size and operating conditions.
[1] Wiegand, H., Meyer, J., and G. Kasper, (2015) An electrical conductivity based method of determining the particle deposition rate in air–liquid interface devices. Toxicology in Vitro, Volume 29, Issue 5, 1100-110.