scholarly journals Isothermal green microwave-assisted extraction of caffeine from guarana: a kinetic study

2017 ◽  
Vol 6 (6) ◽  
Author(s):  
Biljana Koturevic ◽  
Borivoj Adnadjevic ◽  
Jelena Jovanovic
Keyword(s):  
Microwave Heating ◽  
Model Fitting ◽  
Water Extract ◽  
Isoconversional Method ◽  
Microwave Assisted Extraction ◽  
Exponential Factor ◽  
Microwave Assisted ◽  
Assisted Extraction ◽  
Caffeine Extraction ◽  
Kinetics Of

AbstractThe kinetics of isothermal green microwave-assisted extraction of caffeine from guarana seed powder with water at a temperature range from 40°C to 60°C was investigated. The caffeine concentration in the water extract was determined by UV-Vis spectrophotometry. By applying the isoconversional method, it was established that the kinetics of the caffeine extraction from the guarana seed powder with microwave heating is an elementary kinetic process. The model fitting method was used to determine the kinetic model of the caffeine extraction under microwave heating. It was found that the kinetics of the caffeine extraction can, under microwave heating, be modeled by the Jander’s model of three dimensional diffusion. The kinetic parameters, activation energy and pre-exponential factor of the caffeine extraction were determined.

scholarly journals Kinetics of soursop leaves antioxidant extraction using microwave-assisted extraction

2020 ◽  
Vol 572 ◽  
pp. 012041
Author(s):  
Megawati ◽  
D S Fardhyanti ◽  
D Widjanarko ◽  
Hanifah ◽  
G M Bungsu ◽  
...  
Keyword(s):  
Microwave Assisted Extraction ◽  
Microwave Assisted ◽  
Assisted Extraction ◽  
Kinetics Of

scholarly journals Kinetic Study on Chlorophyll and Antioxidant Activity from Polyscias fruticosa (L.) Harms Leaves via Microwave-Assisted Extraction

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3761
Author(s):  
Thi-Thuy-Dung Nguyen ◽  
Quoc-Duy Nguyen ◽  
Thi-Van-Linh Nguyen
Keyword(s):  
Antioxidant Activity ◽  
Microwave Power ◽  
Order Kinetic ◽  
Microwave Assisted Extraction ◽  
Total Polyphenols ◽  
Microwave Assisted ◽  
Assisted Extraction ◽  
Order Kinetic Model ◽  
High Antioxidant Activity ◽  
Kinetics Of

Polyscias fruticosa (L.) leaves contain significant bioactive compounds with high antioxidant activity such as chlorophylls, total polyphenols, etc. but these have still been underutilized. In this study, the kinetics of chlorophyll and antioxidant activity extraction from P. fruticosa leaves by microwave-assisted extraction (MAE) were investigated. Microwave power was 300, 450, or 600 (W); the ratio of material/solvent varied from 1:40 to 1:80 (g/mL). In this study, the second-order kinetic model successfully predicted the change of chlorophyll and antioxidant activity during MAE. The increase of microwave power or/and the solvent amount increased saturated extraction efficiency and the extraction rate constant. However, the saturated concentration of chlorophyll and antioxidant activity increased with the increment of microwave power and the decrease in solvent amount.

scholarly journals Studies of dehydration kinetics of Li2SO4·H2O by the master plots method

2007 ◽  
Vol 5 (1) ◽  
pp. 341-348
Author(s):  
Tang Wanjun ◽  
Chen Donghua
Keyword(s):  
Standard Deviation ◽  
Model Fitting ◽  
Isoconversional Method ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Air Atmosphere ◽  
Master Plots Method ◽  
Fitting Method ◽  
Master Plots ◽  
Kinetics Of

AbstractThe kinetics of Li2SO4·H2O dehydration in static air atmosphere was studied on the basis of nonisothermal measurements by differential scanning calorimetry. Dehydration data were subjected to an integral composite procedure, which includes an isoconversional method, a master plots method and a model-fitting method. Avrami-Erofeev equation was found to describe all the experimental data in the range of conversion degrees from 0.1 to 0.9. The determined activation energy equals 65.45 kJ·mol−1 with standard deviation ±0.47 kJ·mol−1. The estimated value of parameter m in Avrami-Erofeev equation is 2.15 with standard deviation ±0.11. Also, the obtained pre-exponential factor is 7.79×105 s−1 with standard deviation ±0.55×105 s−1. The results show that the present integral composite procedure gives self-consistent kinetic parameters.

Microwave assisted extraction as an important technology for valorising orange waste

2014 ◽  
Vol 38 (6) ◽  
pp. 2278-2283 ◽  
Author(s):  
Thomas M. Attard ◽  
Baillie Watterson ◽  
Vitaliy L. Budarin ◽  
James H. Clark ◽  
Andrew J. Hunt
Keyword(s):  
Fold Increase ◽  
Microwave Assisted Extraction ◽  
Two Stage ◽  
Microwave Assisted ◽  
Assisted Extraction ◽  
Orange Waste ◽  
Stage Process ◽  
Conventional Extraction ◽  
Kinetics Of

Kinetics of microwave-assisted d-limonene extraction demonstrates a five-fold increase in yield over conventional extraction in a two stage process.

scholarly journals Kinetics of the Release of Nicotinamide Absorbed on Partially Neutralized Poly(acrylic-co-methacrylic acid) Xerogel under the Conditions of Simultaneous Microwave Heating and Cooling

Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 193
Author(s):  
Jelena D. Jovanovic ◽  
Borivoj K. Adnadjevic
Keyword(s):  
Kinetic Parameters ◽  
Microwave Heating ◽  
Model Fitting ◽  
Reaction System ◽  
Release Process ◽  
Exponential Factor ◽  
Heating And Cooling ◽  
Different Temperatures ◽  
First Order Chemical Reaction ◽  
Kinetics Of

The kinetics of release of nicotinamide (NIAM) that was absorbed on partially neutralized poly(acrylic-co-methacrylic) (PAM) xerogel/hydrogel, under the conditions of simultaneous microwave heating and cooling (SMHC) were examined. The kinetics curves of NIAM release into an aqueous solution at temperatures of 308–323 K were recorded. By applying the model-fitting method (MFM), it was found that the kinetics of NIAM release can be modeled by a kinetic model of a first-order chemical reaction. The values of the release rate constants (kM) at different temperatures were calculated, and their values were found to be within the range 8.4 10−3 s −1−15.7 10−3 s−1. It has been established that the Arrhenius equation was valid even in the conditions of SMHC. The values of the kinetic parameters (activation energy (Ea) and pre-exponential factor (A) of the NIAM release process adsorbed on PAM xerogel/hydrogel were calculated as follows: Ea = 25.6 kJ/mol and ln (A/s−1) = 5.21. It has been proven that the higher value of the rate constant at SMHC in relation to CH is not a consequence of the overheating of the reaction system or the appearance of “hot-points”. The values of change of the enthalpy of activation (ΔH*) and the change of entropy of activation (ΔS*) were calculated as follows: ΔH* = +23.82 kJ/mol and ΔS* = −201.4 J/mol K. The calculated higher values of the kinetic parameters and thermodynamic parameters of activation are explained by the formation of a specific activated complex under SMHC, whose structure and degree of order are different than in the one formed under CH.

Kinetics of thermal degradation of wood biomass

2014 ◽  
Vol 68 (12) ◽  
Author(s):  
Ivan Hrablay ◽  
Ľudovít Jelemenský
Keyword(s):  
Kinetic Parameters ◽  
13C Nmr ◽  
Model Fitting ◽  
Isoconversional Method ◽  
Experimental Results ◽  
Pyrolysis Kinetics ◽  
Exponential Factor ◽  
Model Free ◽  
Fitting Method ◽  
Kinetics Of

AbstractPyrolysis kinetics of a hardwood representative, beech (Fagus sylvatica), was investigated by two different kinetic approaches: model-free isoconversional method and model-fitting method. The model-free isoconversional method was used for the determination of apparent kinetic parameters, i.e. the activation energy and pre-exponential factor. The model fitting method was used for the optimization of kinetic parameters of the reaction pathways of three selected reaction mechanisms: one-step, two-step, and three-step one. In both approaches, thermo-gravimetric data were used at five heating rates: 2°C min−1, 5°C min−1, 10°C min−1, 15°C min−1 and 20°C min−1. As the most suitable mechanism, the three-step mechanism containing the intermediate degradation step was chosen. This selection was supported by experimental results from the 13C NMR analysis of solid residues prepared at the key temperatures within the range of 230–500°C. The progress of mass fraction values of each component in this mechanism was simulated. Conclusions from the simulation were confronted with experimental results from the 13C NMR.

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