MODELLING OF THE INTERACTION OF NITROGEN DIOXIDE WITH ACTIVATED CARBON I. ADSORPTION DYNAMICS AT THE SINGLE PARTICLE SCALE

The adsorption dynamics of nitrogen dioxide on activated carbon are measured using a microbalance technique. A theoretical model, incorporating the mechanisms of micropore, macropore and concentration dependent sorbed phase (surface) diffusion, with nonlinear equilibrium (dual Langmuir isotherm), is fitted to the experimental NO₂ adsorption dynamics over a range of temperatures, concentrations and particles sizes. The data are well fitted by the model over the temperature range 298-373 K, with typical extracted values of the diffusivities at 298 K being: D/R²_μ=0.003 s^-11 (micropore), D_p = 0.038 cm²/s (macropore) and D_so=1.0 × 10^-6cm²/s (surface) with micropore and surface diffusion activation energies of 14.8 and 11.0 kJ/mole, respectively. The influence of the NO₂/N₂O₄ ratio on the adsorption dynamics is also discussed. At temperature higher than 373 K, significant reaction of NO₂ with activated carbon results in consumption of the carbon.