Adsorption and adsorbate interaction at soot particle surfaces Original Research Article

Previously reported research, demonstrating a role of adsorbed molecular oxygen in the reaction of ozone with soot particles and in their hydration, has been extended to explore the interaction between O2 and SO2, O3, H2O, NH3, NO2 and NO at the soot surface as well as the effect of these adsorbates on each other. Electron paramagnetic resonance (EPR) and microgravimetry have revealed the extent of interactions between some competing reactants on soot. EPR has been used as a probe of the surface behavior of paramagnetic species (O2, NO2, NO) through their effect on the intensity of a large signal which is the result of the high concentration of unpaired electrons in soots. The effects of diamagnetic reactants (H2O, NH3, SO2) also are measured through their influence on the paramagnetic adsorbates and thus on the EPR signal. Microgravimetric measurements of adsorption and changes in the mass resulting from surface reactions also have enabled interpretations of the behavior of reactants on soot particles. Details of the modes of adsorption of SO2, NO2 and NH3 on n-hexane soot have emerged from these measurements as well.