AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Diffusive Filtration Efficiency of Granular Activated Carbons for Nanoparticles
CHANG HYUK KIM, David Y. H. Pui, University of Minnesota
Abstract Number: 16 Working Group: Aerosol Physics
Abstract Granular activated carbons (GACs) are widely used materials to eliminate gaseous contaminants in the air by adsorption. When gas molecules come to GACs, they move into the pores of GACs by diffusion and adhere on the inner surface of the pores. Because diffusion is also an important filtration mechanism of fibrous filters for nanoparticles, GACs can be applied to remove nanoparticles as packed-beds filters. Moreover, if the particle size approaches to 1 nm (molecular levels), the diffusive filtration efficiency of GACs may be enhanced by the internal deposition of nanoparticles on the pores of GACs.
In this study, the diffusive filtration efficiency of GACs for nanoparticles were investigated using three kinds of nanoparticles, such as silver, sulfuric acid and ammonium sulfate. They were synthesized by the condensation and evaporation method with a mini tube furnace (sliver) and by the soft X-ray assisted gas-to-particle conversion (sulfuric acid and ammonium sulfate). The monodisperse nanoparticles were introduced into the GAC holder after classifying the particle size from 3 to 30 nm using a differential mobility analyzer. The particle number concentrations upstream and downstream the GAC holder were measured by an ultrafine condensation particle counter. The diffusive filtration efficiency was calculated from the penetration ratio with the measured particle number concentrations, and increased with the inverse of the particle size. The diffusive filtration efficiency did not change with the composition of the nanoparticles, but did significantly with the face velocity. The single sphere efficiency of GACs was a function of the peclet number (Pe). The exponent of the power-law of Pe was about -0.5, which was between those of the single fiber (-0.43) and sphere (-2/3) theories by others. This implicates that the large surface area of the GAC enhanced the filtration efficiency by the internal deposition of nanoparticles on the pores surfaces.