Degradation of Phenolic Compounds in Aqueous Sucrose Solutions by Ozonation

摘要

The sugar industry is concerned with color formation due to the oxidation of phenolic compounds in the presence of carbohydrates. In this study, we investigated the ozonation of a mixture of five phenolic compounds in water and aqueous sucrose solution: p-coumaric (p-COU), caffeic (CAF), syringic (SYR), and chlorogenic (CHO) acids, as well as the flavonoid quercetin (QUE). The experiments were carried out in a 3-L glass reactor with magnetic stirring and a diffuser plate at the bottom to feed the ozone-oxygen gas mixture. Initial solution concentrations of 5mg L-1 of each acid, 15mg L-1 of quercetin, and 40g L-1 of sucrose were used. The degradation of phenolic compounds followed apparent first-order kinetics, with rate constants and percent removals decreasing in the presence of sucrose. In water, average consumed ozone dosages of 10.4 and 18.7mg L-1 were necessary for 50 and 90 removals, respectively, for CHO, CAF, and p-COU; for QUE they were slightly higher (13.9 and 20.5mg L-1, respectively). At a consumed dosage of 20.8mg O3L-1, more than 99 removal was obtained for CHO, CAF, and p-COU, while 96.2 was achieved for SYR. In contrast, QUE revealed to be more recalcitrant during ozonation in the absence of sucrose, with only 70 removal at the highest consumed O3 dosage. The consumed ozone dosages for 50 and 90 removals were higher for CHO, CAF, and p-COU in aqueous sucrose solution, which may impact ozone consumption during real sugarcane juice treatment. Sucrose and t-butanol were the main influential parameters that significantly affected the total amount of phenolic compounds degraded.