Scrubbing of Sulfur Dioxide Using a Cerium(IV)-Containing Acidic Solution:  A Kinetic Investigation

The paper describes kinetic investigations related to the development of a wet scrubbing process for SO2 abatement from industrial waste gases: the oxidation of sulfur dioxide by tetravalent cerium in a sulfuric medium. Experiments carried out using two gas/liquid contactors and their interpretation could highlight the reaction schemes; rate constants could also be deduced from experimental data at 25 °C. First, tetravalent cerium oxidizes sulfur dioxide into dithionate and sulfuric acid: increasing the concentration of sulfuric acid up to 5 M reduces the importance of dithionate species and the rate constants. The oxidation by Ce(IV) is a first-order process with respect to both reactants, and the global rate constant of SO2 consumption decreases from 2 to 0.05 m3 mol-1 s-1 when the concentration of sulfuric acid is varied from 0.5 to 5 M. Besides, sulfur dioxide can also be oxidized by air oxygen through a catalytic process: both Ce(III) and Ce(IV) species were shown to have significant catalytic effect.