Chemical Engineering Division environmental chemistry annual report, July 1974--June 1975. [Chemistry of airborne particulates; /sup 18/O analysis of atmospheric sulfate aerosols; S emission control chemistry

Abstract

Analysis of ambient urban aerosols using infrared spectroscopic techniques has revealed the presence of acidic sulfate species. Field sampling has also revealed that the chemistry of submicrometer-sized particulates in different geographic regions is characterized more by similarity than differences. Established analytical techniques have been improved, and new approaches, including attenuated total reflectance spectroscopy, have been explored. Study of the oxygen isotope ratios in sulfate, prepared by differing processes in the laboratory, has shown that the oxygen-18 enrichment of the product depends on the specific formation process used. This observation suggests that the oxygen isotope ratio measurements may provide a basis for determining the formation mechanism of sulfate in atmospheric particulates. Preliminary results, based on samples collected at Argonne during winter months, indicate that the sulfate was formed predominantly by a heterogeneous mechanism involving surface-adsorbed species. Details of the oxygen isotope measurement technique are described. X-ray diffraction, optical microscopy, electron microprobe, and TGA studies have been directed toward an understanding of the molecular processes associated with the cyclic use of dolomite in sulfur emission control. Kinetic data are presented for the half-calcination, sulfation, reduction, and carbonation reactions. Other topics discussed include the development of a mathematical model to describe kinetic data,more » the elucidation of a structural and morphological model, the development and use of synthetic dolomites, the feasibility of a solid-solid regeneration reaction, the formation of the binary sulfate, Mg/sub 3/Ca(SO/sub 4/)/sub 4/, and the study of procedures to control the morphology of half-calcined dolomite.« less