Measuring surface area of airborne titanium dioxide powder agglomerates: relationships between gas adsorption,diffusion and mobility-based methods |
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Authors: | Ryan F LeBouf Bon Ki Ku Bean T Chen David G Frazer Jared L Cumpston Aleksandr B Stefaniak |
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Institution: | (1) National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, WV 26505, USA;(2) National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, OH 45213, USA; |
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Abstract: | Inhalation toxicology studies generally use the Brunauer, Emmett, and Teller (BET) gas adsorption method to measure total
surface area of particles whereas occupational exposures are more readily measured by real-time mobility-based surface areas
or active surface area measured with diffusion charger-based instruments. Three surface area measurement methods were studied:
filter-based inert gas adsorption (BET method), diffusion charging, and mobility-based methods. The goal of the project was
to investigate and develop a correlation between the measurement methods. The experimental design consisted of measuring surface
area in a series of five trials for each of two powder types, fine and ultrafine titanium dioxide with primary particle sizes
of 440 and 20 nm, respectively, and two aerosol concentrations. Diffusion charger instruments tended to underestimate the
total particle surface area measured by the BET, but were well correlated with mobility-based surface areas obtained from
a scanning mobility particle sizer. Filter-based gas adsorption methods and diffusion charging methods provide different but
valuable information on total and active surface areas of particles, respectively. Results indicate they should not be used
as predictors of one another. |
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