Interactions of sulfur dioxide with insoluble suspended particulate matter

Abstract

A laboratory study was conducted of the heterogeneous catalysis of sulfur dioxide at ppm concentrations in air by insoluble particles of CaCO2, V2O5, Fe203, flyash from a coal-burning power plant, MnCO2, activated carbon, and suspended particulate matter from urban air. The investigalion was performed by utilizing a new technique for aerosol stabilization which consists of depositing the aerosol on Teflon beads in a fluidized bed. The Teflon beads with deposited aerosol particles were then packed into a flow reactor. Progress of the chemical reaction of SO2with deposited particles was continuously monitored by determining the SO2concentrations in the reactor effluent with a microcoulometer. In this investigation, CaCOg, V2O5, and flyash were essentially inert to SO2at room temperature. Fe2O3, activated carbon, MnO2, and suspended particulate matter from urban air sorbed SO2from air streams with up to 14.4 ppm SO2in air. Evidence is presented which suggests that a substantial part of the sorbed SO2was physically adsorbed. Bioassay procedures which utilize pulmonary flow resistance changes in guinea pigs to monitor response to inhaled SO2-aerosol mixtures in air have indicated the weak or non-potentiating capacity of insoluble aerosols as contrasted to soluble aerosols. Potentiating response of an aerosol appears to be strongly associated with reaction of SO2in a water droplet containing aerosol ions and not with physically adsorbed SO2on an insoluble aerosol. © Taylor & Francis Group, LLC.