Ultrasonic degradation of poly(vinyl alcohol) in aqueous solution

Harkal, Umesh D.; Gogate, Parag R.; Pandit, Aniruddha B.; Shenoy, Mohan

doi:10.1016/j.ultsonch.2005.07.002

Cited by 32 publications

(13 citation statements)

References 10 publications

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“…The most generally used methods such as acid based [5], radiation based (treatment with ionizing radiation) [6] and enzymatic methods [7] suffer from important drawbacks as higher treatment cost especially in the case of enzymatic and ionizing radiation methods and uncontrolled molecular weight reduction with some changes in chemical identity especially in the case of acid based methods [8,9]. The other methods based on ultrasound [10,11] and microwave irradiation [9,12] have good potential for efficient depolymerization. The development of cost effective and efficient methods for degradation of polymer is most important and the issues related to scale up should also be addressed.…”

Section: Introductionmentioning

confidence: 99%

Depolymerization using sonochemical reactors: A critical review

Gogate

Prajapat

2015

Ultrasonics Sonochemistry

104

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Ultrasonic irradiation has been proposed as a novel approach for degradation of polymer compounds, especially considering the fact that the reduction in the molecular weight (also the intrinsic viscosity) is simply by splitting the most susceptible chemical bond without causing any changes in the chemical nature. An overview of the application of ultrasound for the polymer degradation has been presented in this work, discussing the mechanism of degradation, kinetic modeling, effect of operating parameters and the type of reactors generally used for depolymerization. The effect of important operating parameters such as initial polymer concentration, presence of functional groups in the polymer chain, reaction volume, initial molecular weight, temperature, operating frequency, power dissipation and use of process intensifying additives have been discussed also giving guidelines about selection of the optimum parameters. It has been observed that the low concentrations and higher power dissipation (till an optimum) are favorable resulting in higher extents of degradation. Typically low frequency is recommended but for the case of water soluble polymers, higher frequencies would also give similar results due to the dominant action of chemical effects of cavitation. It has been demonstrated that the alkyl group substituent also affects the degradation rate of polymer. An overview of degradation using combined approach based on ultrasound and additives with comparison with individual approach has also been presented. It has been observed that the main contributing factor for the synergy of the combined approach is the selection of optimum loading of additives. Overall, it has been observed that efficient polymer degradation can be achieved using combined process based on the use of ultrasound.

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Section: Introductionmentioning

confidence: 99%

Depolymerization using sonochemical reactors: A critical review

Gogate

Prajapat

2015

Ultrasonics Sonochemistry

104

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“…From the experimental data, it is clear that the degradation rate decreases with increasing solution concentration, so ''n'' is negative. Harkal et al 37 was found that the order of ultrasonic degradation reaction for PVA obtained from this kinetic model is À1.…”

Section: Kinetic Modelmentioning

confidence: 88%

A kinetic study of ultrasonic degradation of carboxymethyl cellulose

Taghizadeh

Abdollahi

2011

J of Applied Polymer Sci

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In this study, the effect of power of ultrasound, temperature, and concentration of carboxymethyl cellulose (CMC) solution on the rate of ultrasonic degradation were investigated, and a kinetic model based on viscometry data was used to calculate the rate constants in different conditions. To investigation of effect of ultrasonic power on the degradation of CMC, the power of ultrasound was increased and observed that the viscosity of the CMC solution was decreased with an increase in the power of ultrasound, but the extent of the degradation in a constant power was found to decrease with an increase in concentration or temperature. The ultrasonic degradation of CMC solutions was carried out at different temperatures to investigate the effect of the temperature on the rate of degradation. The calculated rate constants indicated that the degradation rate of the CMC solutions decreased as the temperature increased. The degraded CMCs were characterized by gel permeation chromatography, and average molecular weights of ultrasonicated CMCs were compared in different reaction conditions.

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“…Harkal et al was found that the order of ultrasonic degradation reaction for poly (vinyl alcohol) obtained from this kinetic model is -1. 47 It is noted that solution concentration (g/L) is constant and the total molar concentration (mol/L) increases during the degradation of polymer. The solution of differential Eq.…”

Section: Kinetic Modelmentioning

confidence: 99%

Photo-Assisted Sondegradation of Hydrogels in the Presence of TiO₂Nanoparticles

Ebrahimi¹,

Tarhandeh²,

Rafiey³

et al. 2012

Journal of the Korean Chemical Society

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ABSTRACT. The degradation of one of the commercially important hydrogel based on acrylic acid and acryl amide, (acrylic acid-co-acryl amide) hydrogels, by means of ultrasound irradiation and its combination with heterogeneous (TiO2) was investigated. 24 kHz of ultrasound irradiation was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. The extent of sonolytic degradation increased with increasing ultrasound power (in the range 30-80 W). TiO2 sonophotocatalysis led to complete (acrylic acid-co-acryl amide) hydrogels degradation with increasing catalyst loading, while, the presence of TiO2 in the dark generally had little effect on degradation. Therefore, emphasis was totally on the sonolytic and sonophotocatalytic degradation of hydrogels and a synergy effect was calculated for combined degradation procedures (Ultrasound and Ultraviolet) in the presence of TiO2 nanoparticles. TiO2 sonophotocatalysis was always faster than the respective individual processes due to the enhanced formation of reactive radicals as well as the possible ultrasound-induced increase of the active surface area of the catalyst. A kinetics model based on viscosity data was used for estimation of degradation rate constants at different conditions and a negative order for the dependence of the reaction rate on total molar concentration of (acrylic acid-co-acryl amide) hydrogels solution within the degradation process was suggested.

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Ultrasonic degradation of poly(vinyl alcohol) in aqueous solution

Cited by 32 publications

References 10 publications

Depolymerization using sonochemical reactors: A critical review

Depolymerization using sonochemical reactors: A critical review

A kinetic study of ultrasonic degradation of carboxymethyl cellulose

Photo-Assisted Sondegradation of Hydrogels in the Presence of TiO₂Nanoparticles

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Ultrasonic degradation of poly(vinyl alcohol) in aqueous solution

Cited by 32 publications

References 10 publications

Depolymerization using sonochemical reactors: A critical review

Depolymerization using sonochemical reactors: A critical review

A kinetic study of ultrasonic degradation of carboxymethyl cellulose

Photo-Assisted Sondegradation of Hydrogels in the Presence of TiO2Nanoparticles

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Photo-Assisted Sondegradation of Hydrogels in the Presence of TiO₂Nanoparticles