Aluminum-based materials for inactivation of aerosolized spores of Bacillus anthracis surrogates

Energetic materials generating biocidal combustion products to disable airborne pathogenic microorganisms (including bio-threat agents) were designed as compounds of halogens and metals with high heats of oxidation. Thermally stable Al-based powders containing iodine and chlorine were prepared using ball-milling at room and cryogenic temperatures. Such powders can replace pure aluminum in metallized energetic formulations. Their stability and halogen release were quantified using thermo-gravimetric analysis. Ignition temperatures were determined by coating prepared powders onto an electrically heated filament. All prepared composites had lower ignition temperatures and longer combustion times compared to pure Al. In separate experiments, combustion products generated by injecting the prepared powders into an air-acetylene flame were mixed with a well-characterized bioaerosol. Inactivation of viable bioaerosol particles exposed to the heated combustion products for a short period of time (estimated to be 0.33 s) was quantified. The combustion products of materials investigated in this study effectively inactivated the aerosolized spores of two tested surrogates of Bacillus anthracis (B. atrophaeus and B. thuringiensis var kurstaki). A ternary composite with 20 wt% of iodine, 40 wt% of aluminum and 40 wt% of boron was found to be most attractive based on both its stability and efficiency in inactivating the aerosolized spores. The inactivation achieved was primarily attributed to chemical stresses as the thermal effect could not solely produce the high measured levels of inactivation. The findings point to a possible synergy of the thermal and chemical spore inactivation mechanisms. © 2017 American Association for Aerosol Research