A reactor using d.c. corona discharge of negative polarity was applied to remove sulfur dioxide from an oxygen-nitrogen mixture in the presence or absence of water vapor for temperatures ranging from room temperature to 350 degreesC. It was observed that increasing the reactor temperature caused a decrease in the removal efficiency. Mixing water vapor with the process gas resulted in an increase of the removal efficiency. The effect of the presence of water vapor on improving the removal efficiency was significant under low temperature conditions, while it was relatively moderate under high temperature conditions. In addition. the solid deposit formed inside the reactor at two temperatures, room temperature and 200 degreesC was analyzed with both a differential scattering calorimeter and an X ray diffractometer. The analysis indicated that SO2 was ultimately converted to solid sulfur in both the presence and absence of water vapor in the gas flow.