PH Oscillations in the Bromate−Sulfite−Marble Semibatch and Flow Systems

Abstract

A self-accelerating oxidation of an unbuffered aqueous sodium sulfite−hydrogen sulfite solution by sodium bromate and a selective removal of the hydrogen ion by solid marble chips from the reaction mixture have been used to construct an oscillatory system. The system exhibits large-amplitude oscillations between pH 3.5 and 7.5 at 25.0 °C in a continuous-flow stirred tank reactor and in a semibatch configuration. The shape, the periodic time (from 10 min to 2 h), and the region of oscillations can be controlled by using different amounts and grade size of marble. A simple reaction scheme, consisting of the protonation equilibria of SO32- and HSO3-, the oxidation of HSO3- and H2SO3 by BrO3-, and a removal of H+ by the CaCO3 in marble in the form of HCO3- has successfully been used to simulate the observed dynamical behavior.