Reaction Kinetics and Mechanism of Iron(II)-Induced Catalytic Oxidation of Sulfur(IV) during Wet Desulfurization

Abstract

The reaction kinetics of the Fe(II)-induced catalytic oxidation of S(IV) in a concentration range of 10–6 M ≤ [Fe(II)] ≤ 1 M was studied. The S(IV) catalytic oxidation reaction order for O2 and HSO3– was found to be 0 and 1 in this iron concentration range. The reaction order toward Fe(II) was 1 for 10–6 M ≤ [Fe(II)] ≤ 10–4 M, 0 for 10–4 M < [Fe(II)] ≤ 10–2 M, and −0.2 for 10–2 M ≤ [Fe(II)] ≤ 1 M. At 30–50 °C the activation energy values were low but increased after an increase in the ionic strength. The ionic strength had a negative influence on the reaction rate constant in the iron concentration range. By analyzing the radical mechanisms and reaction kinetic results, a simplified model for the Fe(II)-induced catalytic oxidation of S(IV), which enables a better analysis and elucidation of the experimental results, is proposed.