Kinetic and Product Studies of the Reactions of NO_2, with Hg° in the Gas Phase in the Presence of Titania Micro-Particle Surfaces

摘要

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 (TiO_2) 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 TiO_2 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 NO_2(g) with Hg_(g)0. We compared the gas-phase reaction to the same reaction performed in the presence of thin TiO_2 particle surfaces from 0 to 100 % relative humidity. The second-order rate constant was measured to be fc=(3.5±0.5)xl0~(-35) cm~6 molecules~(-2) s~(-1), independent of the presence of titania or the total surface area available for adsorption. Exposure of NO_2(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.