Kinetics Of Ultrasonic Degradation Research Articles

Ultrasonic effects on the degradation kinetics, structural characteristics and protective effects on hepatocyte lipotoxicity induced by palmitic acid of Pueraria Lobata polysaccharides

In this study, a high-molecular-weight Pueraria lobata polysaccharide (PLP) with a molecular weight of 273.54 kDa was degraded by ultrasound, and the ultrasonic degradation kinetics, structural characteristics and hepatoprotective activity of ultrasonic degraded PLP fractions (PLPs) were evaluated. The results showed that the ultrasonic treatment significantly reduced the Mw and particle size of PLP, and the kinetic equation of ultrasonic degradation of PLP followed to the midpoint fracture model (the fist-order model). The monosaccharide composition analysis, FT-IR, triple helix structure and XRD analysis all indicated that the ultrasound degradation did not destroy the primary structure of PLP, but the thermal stability of degraded fractions improved. Additionally, the scanning electron microscopy analysis demonstrated that the surface morphology of PLP was altered from smooth, flat, compact large flaky structure to a sparse rod-like structure with sparse crosslinking (PLP-7). The degraded PLP fractions (0.5 mg/mL) with lower Mw exhibited better antioxidant activities and protective effects against palmitic acid-induced hepatic lipotoxicity, which may be due to the increased exposure of active groups such as hydroxyl groups of PLP after ultrasound. Further investigation showed that PLPs not only increased Nrf2 phosphorylation and its nuclear translocation, thereby activating Nrf2/Keap1 signaling pathway, but also enhanced HO-1, NQO-1, γ-GCL gene expressions and promoted superoxide dismutase and catalase activities, which protected hepatocytes against PA-induced oxidative stress and lipotoxicity. Overall, our research might provide an in-depth insight into P. Lobata polysaccharide in ameliorating lipid metabolic disorders, and the results revealed that ultrasonic irradiation could be a promising degradation method to produce value-added polysaccharide for use in functional food.

Ultrasonic degradation kinetics and isomerization of 3- and 4-O-caffeoylquinic acid at various pH: The protective effects of ascorbic acid and epigallocatechin gallate on their stability

Caffeoylquinic acids are existed in many plant species with various biological and pharmacological activities. 3-O-caffeoylquinic acid and 4-O-caffeoylquinic acid are two isomers of caffeoylquinic acids, which may be degraded and transformed to their isomers in processing. The present paper found that the stability of 3- and 4-O-caffeoylquinic acid had decreased with the increasing solution alkalinity. 3-O-caffeoylquinic acid was more stable than 4-O-caffeoylquinic acid at the same condition. During degradation, 3- and 4-O-caffeoylquinic acid were partially converted to their isomers. Additionally, ultrasonic effects on the degradation and isomerization of 3- and 4-O-caffeoylquinic acid at different pH were studied. Ultrasound facilitated the degradation and isomerization of these compounds. The degradation kinetics were described by the Weibull equation. The protective effect of ascorbic acid and epigallocatechin gallate were also explored. Ascorbic acid and epigallocatechin gallate could alleviate the degradation of 3- and 4-O-caffeoylquinic acid under certain conditions.

Ultrasonic Degradation Kinetics and Isomerization of 3- and 4-O-Caffeoylquinic Acid at Various Ph: The Protective Effects of Ascorbic Acid and Epigallocatechin Gallate on Their Stability

Caffeoylquinic acids have been found in many plant species with various biological and pharmacological activities. 3- O -caffeoylquinic acid and 4- O -caffeoylquinic acid are two isomers of caffeoylquinic acids, which may be degraded in processing. The present paper found that the stability of 3- and 4- O -caffeoylquinic acid had decreased with the increasing solution alkalinity , while 3- O -caffeoylquinic acid was more stable than 4- O -caffeoylquinic acid at the same condition. 3- and 4- O -caffeoylquinic acid were converted more to each other than to 5- O -caffeoylquinic acid. Additionally, ultrasonic effects on the degradation and isomerization of 3- and 4- O -caffeoylquinic acid at different pH were studied. Ultrasound facilitated the degradation and isomerization of these compounds. The degradation kinetics were described by the Weibull equation. The protective effect of ascorbic acid and epigallocatechin gallate were also explored. Ascorbic acid and epigallocatechin gallate could abate the degradation of 3- and 4- O -caffeoylquinic acid under certain conditions.

Effects of ultrasonic frequency and initial concentration on degradation of methylene blue

The ultrasonic degradation of hazardous organic compounds in an aqueous solution is an attractive technology for wastewater treatment. The kinetics of ultrasonic degradation has been investigated. However, there have been only a few quantitative studies of the effect of ultrasonic frequency on degradation rate. In this study, the ultrasonic degradation of methylene blue was performed at various frequencies, especially in the high frequency region, and various initial concentrations. From the results of the time dependence of the methylene blue concentration in this study, ultrasonic degradation was considered to be a pseudo-first-order reaction. The apparent degradation rate constant and sonochemical efficiency have a linear relationship, and the apparent rate constant and initial concentration have an inversely proportional relationship. These phenomena well agree with our proposed formula for estimating the apparent degradation rate constant. In addition, our proposed model is also applicable to the ultrasonic degradation of nonvolatile and hydrophilic compounds.

Degradation of Methylparathion Pesticide by Nano Anatase Catalyst

A kind of typical organophosphate insecticide, methylparathion pesticide, was degradated by nano anatase catalyst under a variety of affecting factors. The results indicated that the effects of ultras onic degradation was more obvious in the presence of nanoanatase. The ultrasonic degradation kinetics of methylparathion pesticide in the presence of nano anatase catalyst followed the first-order reaction. The degradation ratio of methylparathion pesticide surpassed 94.2 % within 40 min under ultrasonic frequency of 50kHz, amount of 2000mg.L-1 catalyst, output power of 40W, pH of 6.00, and temperature of 30°C, methyl parathion pesticide concentration of 40mg.L-1.

Degradation and in situ reaction of polyolefin elastomers in the melt state induced by ultrasonic irradiation

AbstractThe degradation and in situ reaction with polystyrene (PS) of polyolefin elastomers in the melt state induced through high intensity ultrasonic wave were investigated. The effects of initial molecular weight of polyolefin elastomers, irradiation time, ultrasonic intensity, as well as reaction temperature on the ultrasonic degradation of polyolefin elastomers melt were studied using a “static” ultrasonic vibration system. The results show that the degradation occurs mostly at the tip of the ultrasonic probe, and little or no degradation was observed at the distance of 5 mm or greater from the tip of the probe. The intrinsic viscosity [η] of polyolefin elastomers near the tip of ultrasound probe significantly decreases with irradiation time in the first 100 s and tends toward a limiting value for all samples. The degradation rates increased with an increase in ultrasonic intensity and decrease in reaction temperature. The ultrasonic degradation kinetics of polyolefin elastomers in melt state follows the equation: [η]t = [η]∞ + Ae−kt. The fitting results by this equation accord well with the experimental data. The feasible ultrasonic degradation mechanism is proposed based on the viscoelastic characteristic of polymer melt. FTIR analysis confirms that the copolymer forms under ultrasonic irradiation for PS/POE mixtures and in situ reaction of polymer in melt state can be induced by ultrasonic irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Kinetics of Ultrasonic Degradation of Phenol in the Presence of Composite Particles of Titanium Dioxide and Activated Carbon.

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionKinetics of Ultrasonic Degradation of Phenol in the Presence of Composite Particles of Titanium Dioxide and Activated Carbon.M. Kubo, H. Fukuda, X. J. Chua, and T. YonemotoCite this: Ind. Eng. Chem. Res. 2007, 46, 11, 3858Publication Date (Web):April 28, 2007Publication History Published online28 April 2007Published inissue 1 May 2007https://doi.org/10.1021/ie070542qCopyright © 2007 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views326Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (5 KB) Get e-Alerts Get e-Alerts

Kinetics of Ultrasonic Degradation of Phenol in the Presence of Composite Particles of Titanium Dioxide and Activated Carbon

Degradation of phenol in water was carried out by ultrasonic irradiation in the presence of the composite particles of titanium dioxide (TiO2) and activated carbon. Degradation of phenol as well as adsorption of phenol on the particles occurred at the same time. The amount of adsorbed phenol on the particles was estimated, and the overall phenol concentration in the system was calculated by adding the amount of adsorbed phenol on the particles and that dissolved in the liquid. The degradation rate in the presence of the composite particles was higher than that when the TiO2 and activated carbon were separately suspended. A kinetic model for degradation of phenol took into account the degradation both in the water phase and on the particle surface. The calculated results explained the effects of the amount of the particles and the TiO2 ratio in the particles on the degradation rate.

Degradation kinetics of polystyrene and EPDM melts under ultrasonic irradiation

The ultrasonic degradation of polystyrene (PS) and ethylene–propylene diene monomer (EPDM) melts was conducted in a specially designed reactor. A degradation model of polymer melts was proposed to explain the ultrasonic degradation, and degradation of polymer melts is treated as a mechanochemical process. Ultrasonic degradation kinetics obeys the equations: M t = M ∞ + A ⅇ − k t or [ η ] t = [ η ] ∞ + ( [ η ] 0 − [ η ] ∞ ) ⅇ − k t . The experimental results show that the molecular weight or intrinsic viscosity of polymer melts decreased with ultrasonic irradiation time and approached a limiting value, below which no further degradation took place. Different from ultrasonic degradation of polymer solutions, the scission of chains in polymer melts is random in the initial stage, and then non-random. FTIR spectra of samples ultrasonically treated and untreated confirmed that the initial product of ultrasonic degradation in polymer melts is a macroradical. The effects of ultrasonic intensity and reaction temperature on degradation of PS and EPDM melts were also investigated. The significant results showed that the degradation rate, the limiting value and degradation extent are correlated greatly with the experimental conditions.

Studies on chain scission and extension of polyamide 6 melt in the presence of ultrasonic irradiation

The ultrasonic degradation of polyamide 6 (PA6) melt was conducted in a specially designed reactor. The effects of initial molecular weight of PA6, irradiation time, ultrasonic intensity as well as ultrasonic irradiation distance on the ultrasonic degradation of PA6 melt were investigated. Some surprising experimental results show that for low molecular weight PA6 (LPA6), the viscosity-average molecular weight of LPA6 increases in the presence of ultrasonic oscillations due to extension reaction of end groups (COOH and NH 2), while for high molecular weight PA6 (HPA6), the viscosity-average molecular weight of HPA6 decreases with irradiation time, and passes through a minimum, then increases with irradiation time, up to a limiting molecular weight. Ultrasonic degradation kinetics of HPA6 melt obey the equation: M t = M ∞+ Ae − kt . FTIR analysis and a microtitration method confirm that the chain scission of HPA6 under ultrasonic irradiation occurs at CN bonds. A plausible ultrasonic degradation model of the polymer melt based on molecular movement is proposed.

Kinetics of ultrasonic degradation and polymerisation degree distribution of sonochemically degraded chitosans

The process of physical degradation by means of the ultrasonic action towards chitosans with mole fraction of 2-acetamido-2-deoxy-β- d-glucopyranose units (the degree of N-acetylation, F A ) in the range of 0.10≤F A≤0.28, and the weight average polymerisation degree ( x ̄ w) in the range of 2.2≤ x ̄ w×10 −3≤3.1 has been investigated. The decrease of x ̄ w as well as changes in the distribution of the degree of polymerisation ( P) has been determined as a function of time, F A , temperature, concentration of chitosan solution and concentration of acetic acid in the solution. The use of low-power ultrasound emitter allowed to establish that in the case of chitosan (binary heteropolysaccharide) the general rate parameter ( k) increased with F A . This can be explained by the relatively stronger aggregation of macromolecules with higher F A , which results in size increase of macromolecular individuals and hence in their higher susceptibility to ultrasonic action. It was also observed that k decreased with chitosan concentration and temperature. The value of limiting degree of polimerisation ( x e ) was found to be influenced by structural parameters of chitosan chains ( F A , aggregation). The increase of acetic acid concentration caused the increase in the k value, what indicated accelerating effect of ultrasound towards acidic hydrolysis of chitosan. The shape of the P curve of sonochemically degraded chitosans are in good correlation with the mid-point breakage concept of degradation accepted in sonochemical degradation of polymers.

Kinetics of ultrasonic degradation of phenol in the presence of TiO 2 particles

The degradation of phenol by ultrasonic irradiation in the presence of TiO 2 was investigated in complete darkness. The effects of amount of TiO 2 and the combination of TiO 2 addition with gas (air or oxygen) supply on the degradation kinetics of phenol and the formation of the reaction products were examined. The degradation rate of phenol increased with the amount of TiO 2. As the dissolved oxygen concentration increased by supplying oxygen, the degradation rate of phenol also increased. A kinetic model for the disappearance of phenol was proposed. The model takes into account the OH radical formation by direct water degradation, indirect degradation by oxygen atom and indirect degradation by TiO 2 catalysis. The calculated results explained well the fact that a higher amount of TiO 2 and dissolved oxygen concentration gave faster disappearance rate.

Mechanochemical degradation kinetics of high-density polyethylene melt and its mechanism in the presence of ultrasonic irradiation

In this paper, the effect of ultrasonic intensity on the degradation of high-density polyethylene (HDPE) melt, degradation mechanism, ultrasonic degradation kinetics of HDPE melt as well as the development of molecular weight distribution of HDPE melt during ultrasonic degradation were studied. In the initial stage, the ultrasonic degradation of HDPE melt shows a random scission process, and the molecular weight distribution broadens. After that, the ultrasonic degradation of HDPE melt shows a nonrandom scission process, and the molecular weight distribution of HDPE melt narrows with ultrasonic irradiation time. The average molecular weight of HDPE decreases with the increase of ultrasonic intensity and increases and trends forward that of undegraded HDPE with the increase of distance from ultrasonic probe tip, indicating that attenuation of ultrasonic intensity in HDPE melt is very quick. Ultrasonic degradation kinetics of HDPE melt obeys the equation: M t = M ∞+ Ae − kt . The theoretic calculation by this equation accords well with the experimental results. The plausible ultrasonic degradation mechanism of polymer melt based on molecular relaxation was also proposed in this paper.

Effect of degree of deacetylation of chitosan on the kinetics of ultrasonic degradation of chitosan

AbstractThe objective of the study was to explore the effect of the degree of deacetylation (DD) of the chitosan used on the degradation rate and rate constant during ultrasonic degradation. Chitin was extracted from red shrimp process waste. Four different DD chitosans were prepared from chitin by alkali deacetylation. Those chitosans were degraded by ultrasonic radiation to different molecular weights. Changes of the molecular weight were determined by light scattering, and data of molecular weight changes were used to calculate the degradation rate and rate constant. The results were as follows: The molecular weight of chitosans decreased with an increasing ultrasonication time. The curves of the molecular weight versus the ultrasonication time were broken at 1‐h treatment. The degradation rate and rate constant of sonolysis decreased with an increasing ultrasonication time. This may be because the chances of being attacked by the cavitation energy increased with an increasing molecular weight species and may be because smaller molecular weight species have shorter relaxation times and, thus, can alleviate the sonication stress easier. However, the degradation rate and rate constant of sonolysis increased with an increasing DD of the chitosan used. This may be because the flexibilitier molecules of higher DD chitosans are more susceptible to the shear force of elongation flow generated by the cavitation field or due to the bond energy difference of acetamido and β‐1,4‐glucoside linkage or hydrogen bonds. Breakage of the β‐1,4‐glucoside linkage will result in lower molecular weight and an increasing reaction rate and rate constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3526–3531, 2003

Sonochemical Degradation Kinetics of Methyl Violet in Aqueous Solutions

The sonochemical degradation in aqueous solution of methyl violet, chosen as a model of a basic dye, was studied. The ultrasonic degradation kinetics in water were found to be first-order and the degradation rate coefficient is 1.35×10-2 min-1 (R= 0.9934, n=8) at 20±1°C. The influence of the initial concentrations, reaction temperature and the pH of medium on the ultrasonic decomposition of methyl violet were also investigated.

Kinetics of ultrasonic and transient elongational flow degradation: a comparative study

The kinetics of ultrasonic degradation has been investigated for dilute polystyrene solutions in decalin. The increase in the scission rate constant ( K) with initial molecular chain length was systematically investigated over 2 decades of molecular weight by using narrow polymer fractions with M = 50 × 10 3 − 8.5 × 10 6Da. An empirical relation of the form K ∼ ( M - M lim) 1.9, with M lim = 30 000, was found for 50 × 10 3 ≤ M ≤ 2.2 × 10 6. The rate constant becomes independent from M at higher molecular weight. This complex behaviour is rationalized by establishing a parallelism between transient elongational flow and ultrasonic degradation.