Kinetics and Mechanism of Se-Catalyzed Disproportionation of Bisulfite: The Critical Role of Selenosulfate

Se-catalyzed disproportionation of bisulfite (HSO3 –) is a facile and potential wet flue gas desulfurization. In this paper, the kinetics and mechanism of Se-catalyzed disproportionation of HSO3 – were systematically investigated. The Se-catalyzed disproportionation of HSO3 – is found to be pseudo-first-order with respect to the HSO3 – and Se concentrations, and is zeroth-order with respect to the initial pH value. More importantly, the kinetics of Se-catalyzed disproportionation of HSO3 – can be divided into two stages, i.e., a rate-controlling stage and an acceleration stage. In the rate-controlling stage, the reaction rate is slow and the intermediate HSeSO3 – forms. This intermediate is decisive to accelerate the HSO3 – disproportionation, and thus, it plays an important role in the Se-catalyzed process. Furthermore, a kinetic equation is determined according to the results: r 0 = k 1[HSO3 –]0.94[Se]1.13, where k 1 = (10.88 ± 0.04) × 10–2 M–1.07·min–1. This kinetics prediction model is fitted well with the experimental data, indicating that this model can satisfactorily describe the experimental kinetic data of Se-catalyzed disproportionation of HSO3 –.