A Fourier transform infrared study of the adsorption of SO2on n-hexane soot from −130° to −40°C

This paper focuses on the uptake of SO2 on soot at temperatures below room temperature. Oxidation on soot may provide a mechanism for the oxidation of atmospheric SO2 under conditions when the standard gas-phase and aqueous-phase mechanisms cannot explain the rapid rate of H2SO4 production. An understanding of the uptake of SO2 under dry conditions provides a useful step toward understanding the uptake and oxidation of SO2 on soot under wet conditions. We find that rapid, reversible SO2 adsorption on soot occurs within a few seconds, presumably by adsorption on the outer surfaces of the spherical soot particles. Subsequently, uptake continues slowly for over an hour, presumably by diffusion into micropores within the soot particles. We focused only on the rapid adsorption. An isothermal analysis of rapid SO2 uptake revealed that a small fraction (