Kinetic and Product Studies of the Reactions of NO₂, with Hg ⁰ in the Gas Phase in the Presence of Titania Micro-Particle Surfaces
2012
Snider, Graydon | Ariya, Parisa
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.
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