This study aimed to enhance the properties of CaCl₂ crosslinked sodium alginate/k-carrageenan (SA/KC) incorporated with clove essential oil (CEO). An evaluation of the modification effects on physicochemical, morphological, antioxidant, and antibacterial properties was performed. The properties were observed at various SA/KC ratios (10/0 to 1.5/1), CEO (1.5% to 3%), and CaCl₂ (0% to 2%). The surface morphology was improved by addition of KC and CaCl₂. The Fourier transform infrared (FTIR) result showed insignificant alteration of film chemical structure. The X-ray diffraction (XRD) result confirmed the increased crystallinity index of the film by CaCl₂ addition. On physicochemical properties, a higher proportion of SA/KC showed the declined tensile strength, meanwhile both elongation at break and water solubility were increased. The incorporated CEO film reduced both tensile strength and water solubility; however, the elongation at break was significantly increased. The presence of Ca²⁺ ions remarkably increased the tensile strength despite decreased water solubility. Overall, the addition of KC and CaCl₂ helped in repairing the mechanical properties and flexibility. CEO incorporation showed the effectiveness of profiling the antioxidant and antimicrobial activity indicated by high 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity up to 90.32% and inhibition zone of E. coli growth up to 113.14 mm².

Depolymerization kinetics of κ-carrageenan by ozone treatment has been studied at various pHs and times. The purified κ-carrageenan with the initial molecular weight of 271 kDa was dispersed in water to form (1 % w/v) solution. Ozone with 80±2 ppm concentration and constant flow rate of 3 L.min-1 was bubbled into the κ-carrageenan solution. The experiments were conducted at pH of 3, 7, and 10 at different times (5, 10, 15, and 20 minutes) of ozonation. The viscosity of the solution was measured using Ubbelohde capillary viscometer, which was then used to find the number-average molecular weight by Mark-Houwink equation. The number-average molecular weight data was treated using zero, first, and the second-order reaction kinetics model, to obtain the kinetics of κ-carrageenan depolymerization. The depolymerization is assumed to occur by random scission. The results show that the kinetics rate constant of κ-carrageenan depolymerization is higher at lower pHs. The second-order model is more suitable for describing the kinetics of depolymerization of κ-carrageenan by ozonation process. The rate constants for the second-order kinetics model are 5.45×10-4 min-1, 1.27×10-4 min-1, and 7.21×10-5 min-1 for pH 3, 7, and 10, respectively. The actual values of reaction order under acid and alkali conditions are ranging from 1.88 to 1.90.

The objective of this research was to investigate the effect of ultrasonication on citronella oil encapsulation using alginate/carrageenan (Alg/Carr) in the presence of sodium dodecyl sulfate (SDS). The functional groups of microparticles were characterized using Fourier transform infrared spectroscopy (FTIR), and the beads’ morphologies were observed using a scanning electron microscope (SEM). The FTIR results showed that the ultrasonication process caused the C-H bonds (1426 cm⁻¹) to break down, resulting in polymer degradation. The SEM results showed that the ultrasonication caused the presence of cavities or pores in the cracked wall and a decrease in the beads’ size. In this study, the use of ultrasound during the encapsulation of citronella oil in Alg/Carr enhanced the encapsulation efficiency up to 95–97%. The kinetic evaluation of the oil release of the beads treated with ultrasound (UTS) showed a higher k₁ value of the Ritger–Peppas model than that without ultrasonication (non-UTS), indicating that the oil release rate from the beads was faster. The R/F value from the Peppas–Sahlin model of the beads treated with UTS was smaller than that of the non-UTS model, revealing that the release of bioactive compounds from the UTS-treated beads was diffusion-controlled rather than due to a relaxation mechanism. This study suggests the potential utilization of UTS for controlling the bioactive compound release rate.

An investigation of the process of ozone combined with ultraviolet radiation has been carried out in order to establish the kinetics for photochemical oxidation of copper (Cu) from electroplating wastewater. The effects of operating parameters, including initial Cu concentration, ozone dosage, UV irradiation intensity, and pH value on the photochemical oxidation of Cu have been studied comprehensively. The Cu concentration during the reaction was identified using atomic absorption spectroscopy (AAS) method. The solid product was analyzed using X-ray diffraction (XRD) and scanning electron microscope–energy-dispersive X-ray (SEM–EDX) methods. It was found that the UV-Ozone process has high performance on Cu removal compared to UV and Ozone processes due to the high production rate of HO• radicals. It was also found that the solid product from the UV-Ozone process was CuO monoclinic crystal phase. The initial Cu concentration, ozone dosage, and pH value were significantly affected the Cu removal efficiency. On the other hand, the UV irradiation intensity was not significant; however, it has responsibility in promoting the ozone photolysis. The kinetics model for the photochemical oxidation of Cu was established following the first-order kinetic model. Furthermore, the reaction mechanism was also developed.

Flavonoid are bioactive compounds that can be found in moringa leaves. Extraction of bioactive compounds using conventional method requires a long time and low extract yields. This study was aimed to determine the optimum process conditions of sequential microwave-ultrasonic-assisted extraction (MUAE) of total flavonoids (TF) from moringa. The response surface methodology (RSM) with Box-Behnken design (BBD) was employed to determine the optimum operating conditions of MUAE among the set of variables: Time (10 - 30 min), temperature (40 - 60 °C), and solvent concentration (60 - 80%). Furthermore, the flavonoids content was determined using high-performance liquid chromatography (HPLC) and the antioxidant activity was analyzed using the DPPH scavenging method. The RSM optimization showed that the predicted optimum total flavonoids content was 3.25 quercetin equivalent (QE) mg/g, achieved under operating conditions at a temperature of 49.76 °C, extraction time 20.68 min and solvent concentration of 71.16 %. These optimum operating conditions were validated, resulting in an average error of 0.546 %. The MS/HPLC results showed that the content of quercetin and myricetin were 0.167 and 2.89 g/ 100 mL, respectively. Moringa extraction product has a strong antioxidant activity with IC₅₀ of 74.58 - 74.62 µg/mL. HIGHLIGHTS GRAPHICAL ABSTRACT 

The low molecular weight (LMW) of sulfated polysaccharides including k-carrageenan, is shows a wide spectrum of biological activities. This research investigates the influence of UV irradiation, ozone (O3), and the combination of O3/UV methods on the depolymerization of k-carrageenan. The depolymerization kinetics of k-carrageenan using the Advanced Oxidation Process (UV/O3) was also studied. Furthermore, the intrinsic viscosity method was used to determine the average molecular weight of the research sample, and a mathematical model was developed to predict the kinetic rate constant, as a function of ozone dosage and UV irradiation intensity. Therefore, the physicochemical and morphological properties of the degraded k-carrageenan were analyzed by FT-IR, SEM, and XRD. The intrinsic viscosity k-carrageenan decreases with increasing UV light intensity and ozone concentration. The combination of UV/O3 treatment appeared to be more effective than the individual approaches, as the highest kinetic rate constant for depolymerization was 1.924×10-4 min-1, using 125 mg/L ozone concentration and 40 mW/cm2 of UV lamp intensity. This research also evaluated the relationship between various experimental conditions, including UV lamp power dissipation and ozone concentration on the reaction kinetics model, and the results suggest that lower effect is contributed by UV irradiation intensity. In addition, FT-IR spectra showed the absence of any significant change in the functional properties of k-carrageenan treated with UV and O3 processes, although the morphological properties of the LMW k-carrageenan were rougher and more porous than the native k-carrageenan. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).