Kinetic and Product Studies of the Reactions of NO2, with Hg0 in the Gas Phase in the Presence of Titania Micro-Particle Surfaces

Abstract

As global mercury emissions from coal fire power plants increase with the continuing rise of coal consumption, mercury capture methods are being developed to prevent mercury’s escape into the atmosphere. Titanium dioxide (TiO2) in the presence of ultra violet light (UV-A; λ max ∼360 nm) and oxygen will capture mercury as the solid product HgO(s). Testing the effects of TiO2 in the presence of other pollutants has so far been limited. We have performed kinetic and product studies of mercury adsorption in the presence of the gaseous flue co-pollutant NO2(g). We extensively studied the gas-phase reaction of NO2(g) with Hg (g) 0 . We compared the gas-phase reaction to the same reaction performed in the presence of thin TiO2 particle surfaces from 0 to 100 % relative humidity. The second-order rate constant was measured to be k = (3.5 ± 0.5) × 10−35 cm6 molecules−2 s−1, independent of the presence of titania or the total surface area available for adsorption. Exposure of NO2(g) to titania surfaces that were already saturated in captured mercury (HgO(s)) increased total mercury uptake onto the surface. We discuss the implications of this study to the capture of mercury emissions prior to release to the atmosphere.