Kinetics of the interaction of water vapour with mineral dust and soot surfaces at T = 298 K

Abstract

The interaction of water vapour with mineral dust and soot surfaces has been studied at T = 298 K using a Knudsen cell reactor. For the uptake of water vapour on mineral dust an adsorption constant of k_ads = 6.0 ± 1.1 s⁻¹, corresponding to an uptake coefficient of γ_ini = (4.2 ± 0.7) × 10⁻² has been determined. The uptake has been found to be reversible and a desorption rate constant of k_des = (1.7 ± 0.1) × 10⁻³ s⁻¹ has been determined. For the uptake of water vapour on soot an uptake coefficient of γ_ini = (3.6 ± 2.0) × 10⁻⁴ has been determined. However, in this case the uptake was found to be more complex with reversible adsorption and rapid saturation of surface sites simultaneously taking place. In order to separate the adsorption and desorption process, additional experiments using D₂O as gaseous reactant have been performed.