Studies on the Oxidation of Corn Starch Granules by Sodium Hypochlorite Part III. Kinetics

Abstract

The kinetics of the oxidation of corn starch granules with sodium hypochlorite were investigated. The reaction, having been reported as a first order reaction, was either first or second order depending on the pH and temperature used during the oxidation. As the lower pH values and the higher temperatures, respectively, in the ranges of pH 8-11 and 20-50°C were used, that is, as the reaction rate increased, the reaction was first order and under the opposite conditions it was second order. There seem to be two steps involved in the oxidation of a heterogeneous system, viz., a diffusion process and a reaction process . It was deduced that the order of the reaction depended upon which of these two steps was the controlling process. The overall activation energy of this reaction was concluded to be approximately 15 kcal/mole. The adsorption equilibrium between corn starch granules and sodium hypochlorite was observed in time of one minute after the start of reaction according to Freundlich adsorption formula and during twenty minutes, too, even though most of oxidants were consumed in the reaction. The oxidation processes, viz., adsorption, consumption and transportation of sodium hypochlorite in the medium and corn starch granules were discussed from the above results.