Investigation Of Chemical Oscillatory Reaction Relating To Chlorine Dioxide And Sodium Chlorite

This paper investigated the chlorite-iodide-ethyl acetoacetate and ClO2-I2-acetylacetone (Hacac) chemical oscillatory reaction system.Firstly, four component reactions were used to model chlorite-iodide-ethyl acetoacetate oscillating reaction by dynamic analysis software Berkeley Madonna. The oscillatory phenomenon is observed for the concentration changes of triiodide ion, chlorite ion, and hydrogen ion. The initial concentration of ethyl acetoacetate, chlorite, iodide, and hydrogen ion has great influence on the oscillation. The period and the amplitude of I3-, CIO2- and H+ have the same change rule when increasing the initial concentration of CIO2- gradually, that is the amplitude and the period of the oscillation decrease gradually as the initial concentration of CIO2- increases. The amplitude of I3-increases with iodine initial concentration and the oscillation period is prolonged by increasing the initial iodine concentration. The amplitude of CIO2- increases and the oscillation period is shortened by increasing the initial iodine concentration. The amplitude of H+ increases and the oscillation period is prolonged by increasing the initial iodine concentration. The period and the amplitude of I3-, CIO2- and H+ have the same change rule when increasing the initial concentration of EAA gradually, that is the amplitude, the period of the oscillation and the induction time of the oscillation increase gradually as the initial concentration of EAA increases.When the initial concentration of H+ increases, the amplitude of I3- increases, the period and the induction time of I3- decrease; the amplitude and the period of CIO2- increase; the amplitude and the period of H+ increase, too. The amplitude and the number of oscillations are associated with the initial reactant’s concentration. The equation of concentration of the triiodide ion, chlorite ion, or hydrogen ion, which is an attenuation sine function, changing with reaction time and the initial concentrations in the oscillation stage was obtained. The bifurcation surface between oscillatory and nonoscillatory behavior with different pH values was obtained by MATLAB and the spatial zone to occur oscillation is reducing with the increase of pH value.Then the system of ClO2-I2-Hacac was studied by UV-vis spectrophotometric, and the obvious oscillation phenomenon can be observed at 295 nm without adding starch and 285 nm,350 nm and 575 nm with adding starch. The initial concentration of reactants, solution acidity and the reaction temperature had great influence on the oscillation reaction.The amplitude and the period of oscillations decrease, as the initial concentration of ClO2 increases.The amplitude increases and the period of oscillations decreases, as the initial concentration of I2 increases. The period of oscillations and amplitude increase, as the initial concentration of acetylacetone increases. The number of oscillations decreases, and amplitude increases, as the pH value of the solution increases. The oscillation reaction can be accelerated by increasing reaction temperature. The apparent activation energy in terms of the oscillation period, which was calculated according to Arrhenius equation, is relatively small. The equations for the triiodide ion reaction rate changing with reaction time and the initial concentrations in the oscillation stage were obtained by differentiating and curve fitting of the oscillatory curves which were got in the experiments. The equations of the amplitude and the period of oscillation changing with initial concentrations of various substances were also obtained.The reaction of iodine and acetylacetone was investigated by online infrared spectrum analysis. Three intermediates were detected during the reaction. The chemical structures of the three intermediates were identified through the infrared spectrum analysis. The reaction mechanism was proposed based upon the relevant literatures.