PARTICLE CHARGE-DISTRIBUTION MEASUREMENT FOR COMMONLY GENERATED LABORATORY AEROSOLS

An improved particle charge analyzer system has been developed to meas ure the absolute charge distribution of common generated laboratory ae rosols. The charge analyzer system consists of an integral cylindrical mobility analyzer used in conjunction with an optical aerosol spectro meter, with computer assisted operation and data reduction. The charge analyzer collects aerosol particles over an absolute electrical mobil ity range from 4.210(-4) to 400 cm(2)/(stat Volt second) and flow rat es that can vary from 0.3 to 30 liters per minute. The charge analyzer has been used to investigate the nature of spray and contact electrif ication during aerosol generation by measuring the residual charge dis tribution on the liquid and solid generated particles. In addition, th e neutralization of charged particles by bipolar ions also was studied using conventional neutralizers that use ionizing radiation from alph a and beta sources. Charge distribution measurements were performed on alumina dust (Al), Arizona road dust (ARD), potassium chloride (KCI), sodium chloride (NaCl) and di-octyl sebacate (DOS) liquid particles. Aerosol generation devices include a Collison atomizer, a condensation aerosol generator and a fluidized bed dust generator. Our work provid es experimental charge distribution data for comparison with simple mo dels of electrification theory. Experimental results showed that charg e levels of atomized KCl and NaCl particles were high and decreased as the dissolved ion concentration increased. DOS particles generated by evaporation-condensation were both neutral and moderately charged. Th ese conclusions support the existence of a dipole layer at the liquid- gas interface that interacts with dissolved particles and changes thei r charge state. Alumina and ARD generated by the fluidized bed dispers er are highly charged due to strong contact electrification during dis persion. In most cases, the charge on generated aerosols could be redu ced to Boltzmann charge equilibrium conditions by commonly used radioa ctive neutralizers. (C) 1998 American Association for Aerosol Research .