Oxidation of aqueous sulphur dioxide in suspensions of magnesium oxide: Removal of SO₂ from flue gases

Abstract

The kinetics of oxidation of aqueous SO₂ in acetate buffered suspensions of MgO obeys rate law (i)<br> R_obs = <em>k</em>[MgO][S(IV)]²[H⁺]^-l ... (i)<br> and the main oxidation product is sulphate. The suggested mechanism involves the formation of surficial complexes between hydroxylated magnesium and S(IV). There exists a close parallelism between R_obs and <em>p</em>H of zero point charge, <em>p</em>H_zpc<em>, </em> for CdO, MgO and SiO₂. The results suggest that in wet-scrubbers, which utilize the slurries of MgO for removal of SO₂ from the flue gases, the sulphite formed as a result of SO₂ absorption will be oxidized by atmospheric oxygen to sulphate, the extent of which will increase with increase in <em>p</em>H<em>, </em> temperature, slurry density and absorbed SO₂.