Kinetics and Thermodynamics of Ultrasound-Assisted Depolymerization of κ-Carrageenan

Ratnawati, Ratnawati; Prasetyaningrum, Aji; Wardhani, Dyah Hesti

doi:10.9767/bcrec.11.1.415.48-58

Cited by 22 publications

(42 citation statements)

References 50 publications

(95 reference statements)

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“…K-carrageenan can be depolymerized using various techniques, such as thermal depolymerization [6], acid-catalyzed hydrolysis [7][8][9][10][11], enzymatic hydrolysis [2], ozone oxidation [12], and ultrasound irradiation [13]. When a polysaccharide solution is subjected to an ultrasound irradiation, the ultrasound wave will cause a cavitation which consists of the nucleation, growth, and collapse of microbubbles.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and Thermodynamics Study of Ultrasound-Assisted Depolymerization of k-Carrageenan in Acidic Solution

Ratnawati

Indriyani

2020

Bull. Chem. React. Eng. Catal.

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K-carrageenan is a natural polymer with high molecular weight ranging from 100 to 1000 kDa. The oligocarrageenan with low molecular weight is widely used in biomedical application. The aim of this work was to depolymerize k-carrageenan in an acidic solution with the assistance of ultrasound irradiation. The ultrasonication was conducted at various pH (3 and 6), temperatures (30-60 °C), and depolymerization time (0-24 minutes). The results show that the depolymerization reaction follows pseudo-first-order kinetic model with reaction rate constant of 1.856×10-7 to 2.138×10-6 s-1. The reaction rate constant increases at higher temperature and lower pH. The Q10-temperature coefficients of the depolymerization are 1.25 and 1.51 for pH 6 and 3, respectively. The enthalpy of activation (ΔH‡) and the Gibbs energy of activation (ΔG‡) are positive, while the entropy of activation (ΔS‡) is negative, indicating that the activation step of the ultrasound-assisted depolymerization of k-carrageenan is endothermic, non-spontaneous, and the molecules at the transition state is more ordered than at the ground state. The ΔH‡ and the ΔS‡ are not affected by temperature, while the ΔG‡ is a weak function of temperature. The ΔH‡ and ΔS‡ become smaller at higher pH, while the ΔG‡ increases with the increase of pH. The kinetics and thermodynamics analysis show that the ultrasound-assisted depolymerization of k-carrageenan in acidic solution is possibly through three mechanisms, i.e. bond cleavage due to cavitational effect of microbubbles, hydroxyl radical and hydrogen peroxide, as well as proton. Copyright © 2020 BCREC Group. All rights reserved

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Section: Introductionmentioning

confidence: 99%

“…Ratnawati et al [13] investigated the effect of temperature on the thermodynamics and kinetics of depolymerization of -carrageenan at pH 9 with the assistance of ultrasound irradiation. There has been no researcher concerned on the effect of pH on the ultrasound-assisted of hydrolysis of k-carrageenan.…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Thermodynamics Study of Ultrasound-Assisted Depolymerization of k-Carrageenan in Acidic Solution

Ratnawati

Indriyani

2020

Bull. Chem. React. Eng. Catal.

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“…In this work, the rate constant for second order model (ks) at pH 10 is 7.21×10 -5 min -1 . Ratnawati et al [29] who degraded κ-carrageenan by ultrasound method found that the kinetics rate constant for pseudo-first order model at 30 o C and pH 10 was 1.74×10 -6 min -1 . The rate constant of ozone treatment is 41.4 fold of that of ultrasonic treatment.…”

Section: Kinetics Depolymerization Of κ-Carrageenan By Ozone Treatmentmentioning

confidence: 99%

“…There were several different techniques, such as microwave-assisted depolymerization [28], sonication [29][30][31], irradiation [17,32], and oxidation using H2O2 [21,33]. Acidic hydrolysis has been considered as a common and fast method to produce a series of carrageenan oligomers, but the use of chemicals causes a potential increase in the level of environmental pollution.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Oxidative Depolymerization of κ-carrageenan by Ozone

Prasetyaningrum

Ratnawati

Jos

2017

Bull. Chem. React. Eng. Catal.

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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.

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“…Next article in this issue is about kinetics and thermodynamics of ultrasound-assisted depolymerization of κ-carrageenan by Ratnawati et al [7]. They found that the results were compared to the result of thermal depolymerization by calculating the half life.…”

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confidence: 99%