Aerosolization of Single-Walled Carbon Nanotubes for an Inhalation Study

Abstract

Single-walled carbon nanotubes (SWCNT) are being produced in increasing quantities because of high interest in applications resulting from their unique properties. Because of potential respiratory exposures during production and handling, inhalation studies are needed to determine potential toxicity. A generation system was designed to produce respirable aerosol at 5 mg/m³ for a 1-wk animal (mouse) exposure. The starting material used in these experiments was as-produced powder from the high pressure carbon monoxide method that was sieved to number 6 mesh (< 2.3 mm). An acoustic feeder system was developed that handled the SWCNT powder without causing compaction of the material. The feed rate was adjustable, allowing output concentrations as high as 25 mg/m³. The powder particles were reduced in size using a mill that produced high shear forces, tearing the agglomerates apart. The resulting aerosol was size-separated using a settling chamber and two cyclones to produce a respirable aerosol. The mass output efficiency of the entire system for producing a respirable aerosol from bulk material was estimated to be about 10%.