pH Oscillations in the BrO₃^-−SO₃^2-/HSO₃^- Reaction in a CSTR

Abstract

Large-amplitude pH oscillations have been measured during the oxidation of sulfur (IV) species by the bromate ion in aqueous solution in a continuous-flow stirred tank reactor in the absence of any additional oxidizing or reducing reagent. The source of the oscillation in this simple chemical reaction is a two-way oxidation of sulfur (IV) by the bromate ion: (1) the hydrogen-ion-producing self-accelerating oxidation to sulfur (VI) (SO4(2-)), and (2) a hydrogen-ion-consuming oxidation to sulfur (V) (S2O6(2-)). In such a way, both the H+-producing and H+-consuming composite processes required for a pH oscillator take place in parallel in a reaction between two reagents in this system. A simple reaction scheme, consisting of the protonation equilibria of SO3(2-) and HSO3-, the oxidation of HSO3- and H2SO3 by BrO3- to SO4(2-), and the oxidation of H2SO3 to S2O6(2-) has successfully been used to simulate the observed dynamical behavior. Simulation with this simple scheme shows that oscillations can be calculated even if only about 1% of sulfur (IV) is oxidized to S2O6(2-) along with the main product SO4(2-). Agreement between calculated and measured dynamical behavior is found to be quite good. Increasing temperature decreases both the period length of oscillations in a CSTR and the Landolt time measured in a closed reactor. No temperature compensation of the oscillatory frequency is found in this reaction.

Chemoelastodynamics of Responsive Gels

“…The sources of chemomechanical instabilities described above have been tested in two quite different proton-autoactivated systems: the CT [63] and the BS [64] reactions.…”

Oscillatory dynamics induced in polyelectrolyte gels by a non-oscillatory reaction: A model

“…The Bromate-Sulfite model is a reaction which is autocatalytic with H + and has been studied previously both in CSTR [25] and in the context of spatial bistability [26]. The reader is invited to refer to [26] for details on the kinetic model and the experimental procedures.…”

“…The purpose of this article is to demonstrate that occurence of oscillations that originate in pure chemomechanical instabilities based on spatial chemical bistability can be predicted on the basis of reasonable and more realistic models. We shall use the Bromate-Sulfite reaction (BS) for which a good kinetic model is available [25,26] and we shall develop a model of swelling for a polyelectrolyte in presence of the reaction. Beforehand, we shall briefly summarize the principles of the chemo-mechanical instability.…”

pH-oscillations in the bromate–sulfite reaction in semibatch and in gel-fed batch reactors

“…Based on this recognition, pHoscillations have recently been produced experimentally in the bromate-sulfite CSTR reaction without coupling it to any additional H þ consuming reaction. 2 The twocomponent BrO 3 -ÀSO 3 2-CSTR reaction shows oscillations only in a relatively narrow range of the experimental parameters (input concentrations, flow rate, and temperature), but the ranges become significantly wider if the BrO 3 À -SO 3 2À reaction is coupled to other H þ consuming processes like to the reactions that take place between bromate and ferrocyanide, 3 hydrogen ion and marble, 4 bromate and manganese(II), 5 2has successfully been used to simulate the observed pH-oscillations and other dynamical phenomena in the bromate-sulfite CSTR reaction. 2 Recently, some practical applications of the pH-oscillators have been proposed.…”

“…pH-oscillations in the bromate-sulfite reaction in semibatch and in gel-fed batch reactors Eszter Poros, 1 Krisztina Kurin-Cs€ orgei, 1 Istv an Szalai, 1 Gyula R abai, 2 The simplest bromate oxidation based pH-oscillator, the two component BrO 3 À -SO 3 2flow system was transformed to operate under semibatch and closed arrangements. The experimental preconditions of the pH-oscillations in semibatch configuration were predicted by model calculations.…”