The oxidation of sulfur dioxide (SO2) in the presence of activated carbon particles has been studied experimentally in slurries of both pure water and sulfuric acid solutions. In the water slurries, the oxidation of absorbed molecular SO2 is accompanied by parallel oxidation of HSO3- ions produced by SO2 dissociation. In acid slurries of pH less than one, the dissociation of molecular SO2 is inhibited and only direct oxidation of molecular SO2 is observed. Experiments in up to 35 wt% sulfuric acid solutions were carried out in slurries of fine coconut activated carbon particles. The rate of molecular SO2 oxidation has been correlated both to an empirical power-law model and to a heterogeneous. Langmuir-Hinshelwood type model : [GRAPHICS] Langmuir-Hinshelwood model corresponds to a kinetic mechanism limited by the surface reaction between adsorbed, non-dissociated O-2 and two adsorbed molecular SO2 molecules.