Kinetics of sulfur dioxide oxidation in slurries of activated carbon and concentrated sulfuric acid

The oxidation of sulfur dioxide (SO 2) 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 SO 2 is accompanied by parallel oxidation of HSO 3 − ions produced by SO 2 dissociation. In acid slurries of pH less than one, the dissociation of molecular SO 2 is inhibited and only direct oxidation of molecular SO 2 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 SO 2 oxidation has been correlated both to an empirical power-law model and to a heterogeneous Langmuir-Hinshelwood type model: R pl = 0.21 m 1 0.69m 2 0.19 m 3 0.72 , R in = 3.81 10 8m 1m 2 2 (1 + 8.46 10 3m 1 + 4.53 10 3m 2 + 1.20m 3) 3 The Langmuir-Hinshelwood model corresponds to a kinetic mechanism limited by the surface reaction between adsorbed, non-dissociated O 2 and two adsorbed molecular SO 2 molecules.