title: Bisulfite-driven autocatalysis in the bromate-thiosulfate reaction in a slightly acidic medium.
abstract: The thiosulfate-bromate reaction has been studied by high-performance liquid chromatography, monitoring the concentrations of thiosulfate and tetrathionate simultaneously. It is found that concentration-time curves of both species display a sigmoidal shape in a slightly acidic, well-buffered medium. Unlike the previously reported complex reaction systems involving bromate, this nonlinear dynamical behavior originates from neither proton nor bromine(III) autocatalysis under our experimental conditions. We demonstrated that sulfur(IV) species significantly accelerates the reaction; therefore, it acts as an autocatalyst. To the best of our knowledge, no reaction system has yet been reported among the pH-driven oxysulfur-oxyhalogen systems, where sulfur(IV) has such a remarkable role. On the basis of the simultaneous evaluation of [S2O3(2-)] and [S4O6(2-)] time series, an eight-step kinetic model is proposed to account for the experimental observations. The model employed here may serve as a solid starting point to extend it for other oxysulfur-oxyhalogen systems where such a seemingly general phenomenon may become observable.
authors.affiliation: College of Chemical Engineering, China University of Mining and Technology , Xuzhou 221116, People's Republic of China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Gao
authors.forename: Changwei
authors.initials: C
authors.lastname: Pan
authors.forename: Yuemin
authors.initials: Y
authors.lastname: Zhao
authors.forename: Attila K
authors.initials: AK
authors.lastname: Horváth