UV Irradiation and Ozone Treatment of κ-Carrageenan: Kinetics and Products Characteristics

Abstract

Low molecular weight (LMW) of sulfated polysaccharide such as κ-carrageenan has been shown to exhibit a wide spectrum of biological activities. In this research, the influence of UV irradiation, ozone (O 3 ), and the combination of O 3 /UV methods on the depolymerization of κ-carrageenan was investigated. The kinetics depolymerization of κ-carrageenan by the Advanced Oxidation Process (UV/O 3 ) was studied in this work. The average molecular weight of LMW of κ-carrageenan was determined by intrinsic viscosity methods. A mathematical model was developed in order to predict the kinetic rate constant as a function of ozone dosage and UV irradiation intensity. The physicochemical and morphological properties of the degraded κ-carrageenan were analyzed by FT-IR, SEM, and XRD. This study shows that the intrinsic viscosity of κ-carrageenan decreases due to the increase in UV lamp power and ozone concentration. The combination of UV/O 3 treatment in the degrading of κ-carrageenan was more effective than individual approaches. The highest value of the kinetic rate constant of depolymerization of κ-carrageenan is 1.924 × 10 -4 min-1 with 125 mg/L ozone concentration and 40 mW/cm2 of UV lamp intensity. This research also studied the relationship between the experimental conditions such as the power dissipation of UV lamp and ozone concentration on the reaction kinetics model of depolymerization of κ-carrageenan. The results of the mathematical model suggest that ozone treatment has a higher effect than the UV irradiation intensity. FT-IR spectra show that no significant change of functional properties of treated κ-carrageenan by UV and O 3 process. However, the morphological properties of LMW of κ-carrageenan have rougher and porous than native κ-carrageenan.