Titanium dioxide is a component of mineral dust aerosols which can play an important role in earth's atmosphere. In this work, transmission FTIR spectroscopy is used to probe the details of sulfur dioxide adsorption and photooxidation on TiO2 nanoparticle surfaces. The role of surface hydroxyl groups and additional insights into the adsorption mechanism were investigated using 16O�H, 16O�D and 18O�H labeled surface O�H groups. These data show that surface hydroxyl groups are involved in the adsorption of sulfur dioxide, and in particularly, sulfur dioxide reacts with either one surface O�H group to yield adsorbed bisulfite or two surface O�H groups to yield both adsorbed sulfite and water. The photooxidation of adsorbed sulfite to sulfate occurs with UV irradiation. Furthermore, it is shown here that adsorbed water more easily displaces sulfite from the surface compared to sulfate by forming a stable sulfur dioxide water complex in the presence of adsorbed water. These differences in stability have implications for adsorbed species that form as a result of surface heterogeneous reactions with sulfur dioxide on TiO2 particle surfaces in particular and, potentially more generally, on oxide particle surfaces including other components of mineral dust aerosol.

Sulfur dioxide adsorption and photooxidation on titanium dioxide nanoparticle surfaces: Roles of surface hydroxyl groups and adsorbed water on the formation and stability of adsorbed sulfite and sulfate

243rd National Meeting (2012)

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