An FT-IR Study of the Effect of Simulated Solar Radiation and Various Particulates on the Oxidation of SO 2

Short- and long-term studies of the effect of black carbon and other particulates on the oxidation of SO₂ with and without the presence of oxygen, water vapor, and simulated solar radiation, have been carried out. FT-IR studies involving isotopic oxygen-18, sulfur dioxide-18, and D₂O in these reactions confirm the requirement of water vapor and oxygen for this oxidation. Such experiments conducted at 298 K demonstrate only the formation of ionic sulfates, while the reactions conducted under simulated solar radiation show the formation of both covalent and ionic sulfate species. These observations have implications for the retention or diminution of catalytic activity by the soot. The reaction vessel walls, SiO₂, and particulate black carbon, all act as catalysts for the conversion of S(IV) to S(VI), the amounts depending primarily on the surface area of the solid.