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Degradation kinetics of anthocyanin and physicochemical changes in fermented turnip juice exposed to pulsed UV light
摘要： In this study, the effects of pulsed UV (PUV) light on the degradation kinetics of anthocyanins and physicochemical properties of turnip juice were investigated. PUV light was applied to turnip juice at 3 different distances (5, 8, 13 cm) from the quartz window of the xenon lamp for 5 different times (5, 15, 30, 45, 60 s). The pH, total acidity (% lactic acid), monomeric anthocyanin content, color density, hue, brightness, and percent color components (yellow, red, and blue) of turnip juice changed significantly after PUV-light treatments at each level. The maximum degradation of anthocyanin after PUV-light treatments was found to be about 63%. The anthocyanin degradation, brightness, yellow and blue color (%) increased, while red color (%) decreased with longer treatment time and shorter distance. The degradation of monomeric anthocyanins in turnip juice exposed to PUV light was described by the Weibull model (R2 0.982–0.998, RMSE 0.087–0.133) more accurately than the first-order kinetics (R2 0.906–0.992, RMSE 0.071–0.192).
关键词： Degradation kinetics of anthocyanin,Pulsed UV light,Physicochemical properties,Turnip juice,Weibull model
更新于2025-09-23 15:21:21
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Structural characterization and thermal degradation of poly(methylmethacrylate)/zinc oxide nanocomposites
摘要： This work is based on the preparation of composites of poly(methylmethacrylate) with zinc oxide nanoparticles synthesized by solution casting method. Chloroform cast poly(methylmethacrylate) films containing different amounts of ZnO nanoparticles were characterized by XRD, SEM, UV-vis spectroscopy, FTIR spectroscopy and TGA. The results show that ZnO nanoparticles with a size of 24 nm were fairly dispersed in the polymer matrix. The obtained material had UV shielding capability with optical transparency. Thermal characterization shows that, the nanocomposites were more thermally stable than pure PMMA presenting three degradation steps. Apparent kinetic parameters were determined for each degradation step using peak fitting methodology. According to activation energies, ZnO particles affect simultaneously but oppositely the kinetics of underlying degradation reactions. Thermal stability of the PMMA/ZnO nanocomposites was the result of the overall balance in favor of the inhibiting effect of ZnO.
关键词： PMMA,polymer nanocomposites,activation energy,ZnO nanoparticles,degradation kinetics,TGA
更新于2025-09-19 17:15:36
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STUDY OF AN ANNULAR PHOTOREACTOR WITH TANGENTIAL INLET AND OUTLET.II. THE UV/H <sub/>2</sub> O <sub/>2</sub> REACTIVE FLOW
摘要： The concentration profiles of species involved in the degradation of phenol by an advanced oxidation processes (AOP) are modeled using a CFD tool, in an annular reactor whose fluid dynamics was the object of a previous study. The reactive flow was fully described together with the kinetic model, which encompasses large kinetic constants, such as 101 0 L mol-1 s-1, and the radiation field. Phenol degradation can be simulated b y using relaxation factors of 1012 kg m-3 s-1 at least. The hydroxyl radical concentration profile, depends on the radiation field, performed by the discrete ordinate (DO) and the discrete transfer (DT) methods. Phenol can be completely degraded along the reactor. A centrifugal effect was observed, with higher concentration of degradation products along the inner wall at the reactor outlet.
关键词： Fluence rate,Advanced oxidation process,Computational fluid dynamics,Phenol degradation,Degradation kinetics,Parameter estimation,Modeling
更新于2025-09-10 09:29:36
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Degradation kinetics and mechanism of 3-Chlorobenzoic acid in anoxic water environment using graphene/TiO <sub/>2</sub> as photocatalyst
摘要： Degradation kinetics and mechanism of 3-Chlorobenzoic acid(3-CBA) in anoxic water environment using graphene/TiO2 (GR/TiO2) as photocatalyst had been investigated. The effects of various parameters such as catalyst dosage, pH, initial concentration, catalyst reuse and dissolved oxygen(DO) on 3-CBA photocatalytic degradation kinetics were studied. The qualitative and quantitative analysis for degradation intermediate products and parent compound were studied by using HPLC, HPLC/MS/MS and IC technologies. The results show that the residual concentration of 3-CBA has a good linear relationship and its correlation coefficient R2are all greater than 0.985 by Langmuir-Hinshelwood (L-H) dynamic model under different photocatalytic degradation conditions; Some oxidative degradation products such as 3-chlorophenol, resorcinol, hydroxyquinol are generated, and some reductive degradation products such as 3-chlorobenzaldehyde, 3-hydroxybenzaldehyde, 3-hydroxybenzyl alcohol, cyclohexanediol are produced, and part of 3-CBA are mineralized to generate CO2 when DO is in the range of 0.5~1.0 mg/L; When DO is less than 0.28 mg/L, photocatalytic reduction mainly occurs. The results provide a theoretical basis for photocatalytic in-situ remediation of pollutants in anoxic water environment.
关键词： Degradation kinetics,Degradation mechanism,3-Chlorobenzoic acid,GR/TiO2,Anoxic water environment
更新于2025-09-04 15:30:14
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Visible–light driven photocatalytic degradation of bisphenol-A using ultrasonically synthesized polypyrrole/K-birnessite nanohybrids: Experimental and DFT studies
摘要： Although manganese oxides are known for their semiconductor characteristics, the photocatalytic performance of conducting polymer intercalated K-Birnessite (K-Bi) has not been explored till date. With the view to design a visible light driven organic–inorganic hybrid photocatalyst for rapid degradation of Bisphenol A (BPA), the present work reports the ultrasound-assisted green synthesis of K-Bi/polypyrrole (Ppy) nanohybrids. The loading of Ppy in K-Bi was confirmed by thermogravimetric analysis while the formation of organic–inorganic hybrid was confirmed by infrared spectroscopy. K-Bi revealed a band gap of 2.8 eV while for the nanohybrids it was found to be ranging between 2.4 and 1.6 eV. X-ray diffraction studies confirmed partial intercalation of Ppy chains in the inter-layer space of K-Bi. High resolution transmission electron microscopy and scanning electron microscopy studies showed mixed morphology of K-Birnessite/Ppy nanohybrids. Rapid degradation of BPA was observed under visible irradiation in presence of K-Bi/Ppy nanohybrids and almost 90% degradation of 20 mg/L BPA solution was achieved within 120 min. The degradation was found to follow pseudo-first order kinetics and the degraded fragments were identified using liquid chromatography-mass spectrometry. Degradation pathway was proposed based on density-functional theory calculations of fukui index predicting the radical easy-attacking (f0) and (f-) sites in BPA.
关键词： DFT calculations,Degradation kinetics,Photocatalysis,Manganese oxide,Polypyrrole
更新于2025-09-04 15:30:14