A New pH Oscillator: The Chlorite-Sulfite-Sulfuric Acid System in a CSTR

摘要

Anew pH oscillator has been discovered involving the system of NaClO_2, Na28O_3, and H28O4 in a continuous- flow stirred tank reactor (C8TR). While ClO2- serves as an oxidant in numerous systems exhibiting nonlinear dynamical behavior, this is the first reported chlorite-based pH oscillator. Large-amplitude oscillations in pH and potential of a platinum electrode were observed over a rather narrow concentration range. Complex dynamical behavior also was observed, including aperiodic oscillations, bistability between steady states, bistability between steady state and oscillatory state, bursting, a possible third steady state, and damped oscillations in batch. Autocatalytic oxidation of H8O_3~- by ClO2- is a major source of positive feedback in H+. A fast Cl+-transfer reaction between HOCl and 8O32~- is an important source of negative feedback. Oscillations were also obtained in the presence of Na_2CO_3, with the dehydration reaction of H_2CO_3 providing additional negative feedback. Models are proposed to account for observed behavior using computer simulations. Comparisons are made to the ClO_2~--I~- and CIO_2-I~- oscillating systems, as well as to the general model for chlorite-based chemical oscillators proposed by Rabai and Orban. A possible mechanism for chemical coupling is proposed.