AN EXPERIMENTAL-STUDY ON THE RATE OF REACTION BETWEEN MERCURY-VAPOR AND GASEOUS NITROGEN-DIOXIDE

The importance of nitrogen dioxide for oxidation of gaseous mercury in the atmosphere and in combustion flue gases was investigated. The reaction rate was studied by a stopped flow technique in a temperature interval from 20 degrees C to 900 degrees C and at surface-to-volume ratios of 1.8 and 4 cm(-1). The reaction exhibits a first-order dependence with respect to mercury and a second-order dependence with respect to NO2 in the temperature range from 20 degrees C to 200 degrees C. From 250 degrees C to 500 degrees C, the NO2 dependence is lost and a partly heterogeneous reaction is proposed. Above 500 degrees C, no reaction was detectable. The Hg-NO2 reaction appears to have little significance for the atmospheric chemistry of mercury nor for the transformation of mercury in combustion processes, It might, however, have some importance on the oxidation of elemental mercury in aging combustion plumes.