ACTIVATED CARBON ADSORPTION AND DESORPTION OF TOLUENE IN THE AQUEOUS-PHASE

The equilibrium and dynamics of toluene adsorption and desorption in single-component aqueous solutions were investigated. Adsorption rates in a batch reactor under a variety of operating conditions were fitted successfully with the homogeneous surface diffusion model and a surface diffusion coefficient that increases exponentially with surface concentration. The dependence of the external mass-transfer coefficient on the hydrodynamic conditions in the liquid phase was taken into account. Desorption studies in the aqueous phase and solvent regeneration of toluene-loaded activated carbon suggest that only a small fraction of toluene adsorbs irreversibly. Moreover, irreversible adsorption occurs only on virgin activated carbon, while adsorption on solvent-regenerated activated carbon is fully reversible. After accounting for irreversible adsorption, the model successfully predicted toluene desorption rates in the aqueous phase under various operating conditions using toluene transport parameters determined from the adsorption studies.