PH OSCILLATIONS IN THE BROMATE-SULFITE-MARBLE SEMIBATCH AND FLOW SYSTEMS

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 lar ge-amplitude oscillations between pH 3.5 and 7.5 at 25.0 degrees C in a continuous-flow stirred tank reactor and in a semibatch configuratio n. The shape, the periodic time (from 10 min to 2 h), and the region o f oscillations can be controlled by using different amounts and grade size of marble. A simple reaction scheme, consisting of the protonatio n equilibria of SO32- and HSO3-, the oxidation of HSO3- and H2SO3 by B rO3-, 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 .