Kinetic modeling of advanced starch oxidation with ozone in basic solutions

• Published in: Ozone: science & engineering Vol. ahead-of-print; no. ahead-of-print; pp. 1 - 10
• Main Authors: Ávila-Sierra, Alejandro, Vicaria, José M., Martínez-Gallegos, Juan F., Cañadas, Sara, Jurado-Alameda, Encarnación
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 02.11.2023; Taylor & Francis Ltd
• Subjects: Activation energy; Additives; Advanced oxidation process; Batch reactors; Chemical oxygen demand; Food additives; Food industry; Free radicals; High temperature; Hydroxyl radicals; Kinetic model; Oxidants; Oxidation; Oxidation process; Oxidizing agents; Ozonation; Ozone; Pharmaceutical industry; Physicochemical properties; Reaction time; Semi-batch reactor; Starch; Starches
• ISSN: 0191-9512; 1547-6545
• DOI: 10.1080/01919512.2023.2178382

The growing use of ozone (O 3 ) in the last years to clean and enhance the physicochemical properties of starches, widely used as additives in food, beverage, and pharmaceutical industries, calls for a better understanding of their oxidation process. High pH, however, decomposes O 3 rapidly, forming highly-oxidant radicals, thus increasing the complexity of the reaction system. In this study, a kinetic model for the ozonation reaction of starch in an alkaline medium was developed and experimentally validated. Firstly, the concentration of hydroxyl radicals ( ● OH) over the reaction time is evaluated through the degradation of pCBA (a probe compound) to later evaluate and model the oxidation process of starch based on Chemical Oxygen Demand (COD) measurements. By using a semi-batch reactor containing alkaline solutions at pH = 13, different O 3 concentrations (0-42.30 g/Nm 3 ) and temperatures (20-60 °C), a pseudo first-order kinetic model was proposed to model the pCBA-ozone reaction. This model estimates the ● OH formation, being [ ● OH] constant and proportional to the O 3 continuous dose. Therefore, under the conditions studied, ● OH is a non-limiting reactant independent of temperature. The activation energy was estimated at 14.2 ± 2.1 and 14.5 ± 0.6 KJ/mol for 21.15 and 42.30 gO 3 /Nm 3 , respectively. Then, COD data were used to propose a kinetic model for ozone-starch oxidation in alkaline media, where besides O 3 concentration and temperature, starch concentration (600-1700 mg/L) was also varied. According to the results, higher temperatures and longer reaction times resulted in a greater COD reduction, being it more pronounced at lower initial starch concentration. The activation energy of the ozone radicals-starch reaction was estimated at 8.1 ± 0.4 KJ/mol, being significantly lower than those reported for the reaction between pCBA and ● OH.