Mechanism and Kinetic Analysis of Degradation of Atrazine by US/PMS

The degradation effect, degradation mechanism, oxidation kinetics, and degradation products of Atrazine (ATZ) by Ultrasound/Peroxymonosulfate (US/PMS) in phosphate buffer (PB) under different conditions were studied. It turned out that the degradation rate of US/PMS to ATZ was 45.85% when the temperature of the reaction system, concentration of PMS, concentration of ATZ, ultrasonic intensity, and reaction time were 20 °C, 200 μmol/L, 1.25 μmol/L, 0.88 W/mL, and 60 min, respectively. Mechanism analysis showed that PB alone had no degradation effect on ATZ while PMS alone had extremely weak degradation effect on ATZ. HO• and SO4−• coexist in the US/PMS system, and the degradation of ATZ at pH7 is dominated by free radical degradation. Inorganic anion experiments revealed that Cl−, HCO3−, and NO3− showed inhibitory effects on the degradation of ATZ by US/PMS, with Cl− contributing the strongest inhibitory effect while NO3− showed the weakest suppression effect. According to the kinetic analysis, the degradation kinetics of ATZ by US/PMS was in line with the quasi-first-order reaction kinetics. ETA with concentration of 1 mmol/L reduced the degradation rate of ATZ by US/PMS to 10.91%. Product analysis indicated that the degradation of ATZ by US/PMS was mainly achieved by dealkylation, dichlorination, and hydroxylation, but the triazine ring was not degraded. A total of 10 kinds of ATZ degradation intermediates were found in this experiment.

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Electrochemical degradation of diclofenac by boron doped diamond anode: degradation mechanism, pathways and influencing factors

Water Science & Technology ◽

10.2166/wst.2021.231 ◽

2021 ◽

Author(s):

Huimin Qiu ◽

Pingping Fan ◽

Xueying Li ◽

Guangli Hou

Keyword(s):

Influencing Factors ◽

Wastewater Treatment Plants ◽

Degradation Products ◽

Degradation Kinetics ◽

Degradation Mechanism ◽

Electrochemical Process ◽

Sodium Sulphate ◽

Boron Doped Diamond ◽

Quenching Effect ◽

Boron Doped

Abstract Nonsteroidal anti-inflammatory drugs (NAIDS) have been widely detected in wastewater and surface water, which indicates the removal of NAIDS by wastewater treatment plants was not efficiency. Electrochemical advanced oxidation technology is considered to be an effective process. This study presents an investigation of the kinetics, mechanism and influencing factors of Diclofenac (DCF) degradation by an electrochemical process with the boron doped diamond anodes. Relative operating parameters and water quality parameters are examined. It appears that the degradation follows the pseudo-first-order degradation kinetics. DCF degradation was accelerated with the increase of pH from 6 to 10. The degradation was promoted by the addition of electrolyte concentrations and current density. HA and HCO3− significantly inhibited the degradation, whereas Cl− accelerated it. According to the inhibition tests, hydroxyl radicals (•OH) and sulfate radicals (SO4•–) contributed 76.5% and 6.5%, respectively, to the degradation. Sodium sulphate remains a more effective electrolyte, compared to sodium nitrate and sodium phosphate, suggesting the quenching effect of nitrate and phosphate on •OH. Major DCF transformation products were identified. According to the degradation products detected by liquid chromatography-mass spectrometry, hydroxylation and decarboxylation are the main pathways to DCF degradation; meanwhile, dechlorination, chlorination and nitro substitution are also included.

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Development and Validation of a Stability-Indicating HPLC-Photodiode Array Detector Method for Formulation Analysis and Degradation Kinetics and Dissolution Studies of Mycophenolate Sodium and HPLC/MS/MS Characterization of its Stress Degradation Products

Journal of AOAC International ◽

10.5740/jaoacint.11-063 ◽

2013 ◽

Vol 96 (3) ◽

pp. 593-598

Author(s):

Anna Pratima G Nikalje ◽

Vishnu P Choudhari

Keyword(s):

Degradation Product ◽

Degradation Products ◽

Degradation Kinetics ◽

Array Detector ◽

Forced Degradation ◽

Product Analysis ◽

Mycophenolate Sodium ◽

Stability Indicating ◽

Stress Degradation

Abstract A simple stability-indicating isocratic RP-HPLC method was developed and validated for the determination of mycophenolate sodium and its alkali degradation product. Forced degradation of the drug was carried out under thermolytic, photolytic, acid/base hydrolytic, and oxidative stress conditions. Alkali degradation product DP1 was isolated, and separation of stress degradation products was achieved on a Symmetry C18 (250 × 4.6 mm × 5.0 μm) column using the mobile phase methanol–acetate buffer adjusted with acetic acid to pH 6.0 (76 + 24, v/v) at a 0.55 mL/min flow rate and 50°C. Data were integrated at the detection wavelength of 251 nm. The method validation characteristics included accuracy, precision, linearity, range, specificity, and sensitivity per International Conference on Harmonization guidelines. Robustness testing was conducted to evaluate the effect of minor changes in the chromatographic conditions and to establish appropriate system suitability parameters. Structural elucidation of degraded products was performed by HPLC/MS/MS. The method was used successfully for drug product analysis, dissolution study, and determination of the drug's acid, alkali, and oxidative degradation kinetics.

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Empirical Kinetic Modelling and Mechanisms of Quercetin Thermal Degradation in Aqueous Model Systems: Effect of pH and Addition of Antioxidants

Applied Sciences ◽

10.3390/app11062579 ◽

2021 ◽

Vol 11 (6) ◽

pp. 2579

Author(s):

Abdessamie Kellil ◽

Spyros Grigorakis ◽

Sofia Loupassaki ◽

Dimitris P. Makris

Keyword(s):

Thermal Degradation ◽

Empirical Model ◽

Degradation Products ◽

Degradation Kinetics ◽

Kinetic Modelling ◽

Degradation Mechanism ◽

Antioxidant Properties ◽

Biological Significance ◽

Model Systems ◽

Molar Ratio

Quercetin (Qt) is a natural flavonoid of high biological significance, and it occurs in a wide variety of plant foods. Although its oxidation by various means has been extensively studied, its behavior with regard to thermal treatments remains a challenge. The study described herein aimed at investigating Qt thermal decomposition, by proposing an empirical sigmoidal model for tracing degradation kinetics. This model was employed to examine the effect of addition of antioxidants on Qt thermal degradation, including ascorbic acid, L-cysteine, and sulfite. Furthermore, degradation pathways were proposed by performing liquid chromatography-tandem mass spectrometry analyses. Upon addition of any antioxidant used, the sigmoidal course of Qt thermal degradation was pronounced, evidencing the validity of the empirical model used in the study of similar cases. The antioxidants retarded Qt degradation in a manner that appeared to depend on Qt/antioxidant molar ratio. No major differentiation in the degradation mechanism was observed in response to the addition of various antioxidants, and in all cases protocatechuic acid and phloroglucinol carboxylic acid were typical degradation products identified. Furthermore, in all cases tested the solutions resulted after thermal treatment possessed inferior antioxidant properties compared to the initial Qt solutions, and this demonstrated the detrimental effects of heating on Qt. The empirical model proposed could be of assistance in interpreting the degradation behavior of other polyphenols, but its validity merits further investigation.

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Photoassisted Degradation of a Herbicide Derivative, Dinoseb, in Aqueous Suspension of Titania

The Scientific World JOURNAL ◽

10.1100/2012/251527 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 6

Author(s):

Niyaz A. Mir ◽

Malik M. Haque ◽

Abuzar Khan ◽

Mohd. Muneer ◽

Colin Boxall

Keyword(s):

Uv Light ◽

Degradation Products ◽

Degradation Kinetics ◽

Degradation Mechanism ◽

Aqueous Suspension ◽

Electron Acceptors ◽

Potassium Persulphate ◽

First Order Kinetics ◽

Degradation Rates ◽

Degussa P25

The titanium dioxide (TiO2) photoassisted degradation of herbicide dinoseb has been examined in aqueous suspensions under UV light irradiation. The degradation kinetics were studied under various conditions such as substrate concentration, type of catalyst, catalyst dosage, pH, and light intensity as well as in presence of electron acceptors such as hydrogen peroxide, potassium bromate, and potassium persulphate under continuous air purging, and the degradation rates were found to be strongly influenced by these parameters. The Degussa P25 was found to be more efficient photocatalyst as compared to other photocatalysts tested. Dinoseb was found to degrade efficiently in acidic pH and all the electron acceptors studied enhanced the degradation rate. The results manifested that the photocatalysis of dinoseb followed pseudo-first-order kinetics. A qualitative study of the degradation products generated during the process was performed by GC-MS, and a degradation mechanism was proposed.

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The influence of pH on the molecular degradation mechanism of PLGA

MRS Advances ◽

10.1557/adv.2018.602 ◽

2018 ◽

Vol 3 (63) ◽

pp. 3883-3889 ◽

Cited By ~ 3

Author(s):

Rainhard Machatschek ◽

Burkhard Schulz ◽

Andreas Lendlein

Keyword(s):

Degradation Products ◽

Bulk Material ◽

Degradation Kinetics ◽

Degradation Mechanism ◽

Controlled Drug Release ◽

Interfacial Rheology ◽

Alkaline Conditions ◽

A Chain ◽

The Impact ◽

Kinetics Of

ABSTRACTPoly[(rac-lactide)-co-glycolide] (PLGA) is used in medicine to provide mechanical support for healing tissue or as matrix for controlled drug release. The properties of this copolymer depend on the evolution of the molecular weight of the material during degradation, which is determined by the kinetics of the cleavage of hydrolysable bonds. The generally accepted description of the degradation of PLGA is a random fragmentation that is autocatalyzed by the accumulation of acidic fragments inside the bulk material. Since mechanistic studies with lactide oligomers have concluded a chain-end scission mechanism and monolayer degradation experiments with polylactide found no accelerated degradation at lower pH, we hypothesize that the impact of acidic fragments on the molecular degradation kinetics of PLGA is overestimated. By means of the Langmuir monolayer degradation technique, the molecular degradation kinetics of PLGA at different pH could be determined. Protons did not catalyze the degradation of PLGA. The molecular mechanism at neutral pH and low pH is a combination of random and chainend-cut events, while the degradation under strongly alkaline conditions is determined by rapid chainend cuts. We suggest that the degradation of bulk PLGA is not catalyzed by the acidic degradation products. Instead, increased concentration of small fragments leads to accelerated mass loss via fast chain-end cut events. In the future, we aim to substantiate the proposed molecular degradation mechanism of PLGA with interfacial rheology.

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Impact of Active Chlorines and •OH Radicals on Degradation of Quinoline Using the Bipolar Electro-Fenton Process

Water ◽

10.3390/w13020128 ◽

2021 ◽

Vol 13 (2) ◽

pp. 128

Author(s):

Wenlong Zhang ◽

Jun Chen ◽

Jichao Wang ◽

Cheng-Xing Cui ◽

Bingxing Wang ◽

...

Keyword(s):

Degradation Kinetics ◽

Degradation Mechanism ◽

Supporting Electrolyte ◽

Reaction System ◽

Oxygen Demand ◽

Oh Radicals ◽

Fenton Process ◽

Reaction Conditions ◽

Initial Ph ◽

Kinetics Of

Quinoline is a typical nitrogenous heterocyclic compound, which is carcinogenic, teratogenic, and mutagenic to organisms, and its wastewater is difficult to biodegrade directly. The bipolar electro-Fenton process was employed to treat quinoline solution. The process/reaction conditions were optimized through the single factor experiment. The degradation kinetics of chemical oxygen demand (COD) was analyzed. To get the degradation mechanism and pathways of quinoline, the intermediate products were identified by gas chromatograph–mass spectrometer (GC–MS). By using sodium chloride as supporting electrolyte in the electro-Fenton reaction system with initial pH 3.0, conductivity 15,800 µs/cm, H2O2 concentration 71 mmol/L, current density 30.5 mA/cm2, and applied voltage 26.5 V, 75.56% of COD was decreased by indirect oxidation with electrogeneration of hydroxyl radicals (•OH) and active chloric species in 20 min. The COD decrease of quinoline solution followed the first order reaction kinetic model. The main products of quinoline degradation were 2(1H)-quinolinone, 4-chloro-2(1H)-quinolinone, 5-chloro-8-hydroxyquinoline, and 5,7-dichloro-8-hydroxyquinoline. Furthermore, two possible degradation pathways of quinoline were proposed, supported with Natural charge distribution on quinoline and intermediates calculated at the theoretical level of MN15L/6-311G(d).

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Ag2O and NiO Decorated CuFe2O4 with Enhanced Photocatalytic Performance to Improve the Degradation Efficiency of Methylene Blue

Materials ◽

10.3390/ma13214760 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4760

Author(s):

Lu Liu ◽

Nan Hu ◽

Yonglei An ◽

Xingyuan Du ◽

Xiao Zhang ◽

...

Keyword(s):

Methylene Blue ◽

Rate Constant ◽

Fenton Reaction ◽

Degradation Rate ◽

Photocatalytic Performance ◽

Reaction System ◽

Dye Wastewater ◽

Degradation Rate Constant ◽

Degradation Effect ◽

High Degradation Rate

Dye wastewater is a serious threat to human health and life. It is an important task for researchers to treat it efficiently. Among many treatment methods, the photo-Fenton method can rapidly degrade organic pollutants. In this study, a ternary photocatalyst, Ag2O-NiO/CuFe2O4, was prepared and applied for a photo-Fenton reaction to degrade methylene blue (MB). MB had the best degradation effect when 10 mg of the catalyst were used in an 80 mL reaction system for measurement. The degradation rate of MB was up to 96.67% in 60 min with a high degradation rate constant k=5.67×10−2min−1. The total organic carbon (TOC) degradation rate was 78.64% with a TOC degradation rate constant of k=2.57×10−2min−1. Therefore, this study fully proves that Ag2O-NiO/CuFe2O4 can catalyze the photo-Fenton reaction and effectively degrade MB.

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RETRACTED ARTICLE: Kinetic and anion degradation products study on photocatalytic degradation of reactive orange 5 solution with phosphotungstic acid

Open Chemistry ◽

10.2478/s11532-007-0064-2 ◽

2008 ◽

Vol 6 (1) ◽

pp. 99-105 ◽

Cited By ~ 2

Author(s):

Junbo Zhong ◽

Hong Zhao ◽

Di Ma ◽

An Lian ◽

Minjiao Li ◽

...

Keyword(s):

Kinetic Model ◽

Photocatalytic Degradation ◽

Phosphotungstic Acid ◽

Degradation Products ◽

Degradation Mechanism ◽

Reaction System ◽

Retracted Article ◽

Degradation Reaction ◽

The Difference ◽

Reactive Orange

AbstractIncreasing environmental pollution caused by toxic dyes is a matter of great concern due to their hazardous nature. So it is crucial to develop processes which can destroy these dyes effectively. It has been generally agreed that reactive orange 5 (KGN) can be effectively degraded in aerated phosphotungstic acid (HPA) in a homogeneous reaction system using near-UV irradiation. In this paper, photocatalytic degradation of reactive orange 5 solutions with phosphotungstic acid was investigated, especially more attention was paid to the kinetic model and the anion degradation products. The results revealed that the photocatalytic degradation reaction of KGN with HPA in a homogenous solution can be described by Langmuir-Hinshelwood equation and Langmuir-Hinshewood kinetic model described it well. The reaction manifested the first order with lower concentration(⩽30 mg L−1) with the limiting rate constant and the adsorption constant in this case being 0.8098 mg L−1 min−1 and 4.359 10−2 L mg−1, respectively. The degradation mechanism of KGN with HPA is different from that with TiO2, the anion products of the two reaction systems are the same. The difference in degradation mechanism of KGN with HPA from that with TiO2 is caused by the nature of the photocatalyst.

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Multi-chain action of exo-D-galacturonanase from carrot

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19833579 ◽

1983 ◽

Vol 48 (12) ◽

pp. 3579-3588

Author(s):

Kveta Heinrichová ◽

Jana Perečková

Keyword(s):

Optimal Condition ◽

Degradation Products ◽

Degradation Kinetics ◽

Hydrolytic Cleavage ◽

Chain Mechanism ◽

Modes Of Action ◽

Enzyme Degradation ◽

Good Agreement

Two possible modes of action of exo-D-galacturonanase from carrot (E.C. 3.2.1.67) were investigated; this enzyme catalyses the sequential hydrolytic cleavage of pectants and oligogalacturonans by a terminal action from the nonreducing end of the molecule. The experiments indicate that the investigated exo-D-galacturonanase degrades these substrates by a predominantly multi-chain mechanism. Distribution of degradation products of oligomeric substrates (hexa- and pentagalacturonide) under an optimal condition for the action of the enzyme (pH and temperature) indicates that a multi-chain enzyme attack with a prevalent simple collision is involved. Results of the enzyme degradation kinetics are in a good agreement with the above-mentioned presumption.

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Thermal degradation kinetics of Opuntia Ficus Indica flour and talc-filled poly (lactic acid) hybrid biocomposites by TGA analysis

Journal of Composite Materials ◽

10.1177/00219983211008202 ◽

2021 ◽

pp. 002199832110082

Author(s):

Azzeddine Gharsallah ◽

Abdelheq Layachi ◽

Ali Louaer ◽

Hamid Satha

Keyword(s):

Thermal Stability ◽

Lactic Acid ◽

Thermal Degradation ◽

Degradation Kinetics ◽

Degradation Mechanism ◽

Melt Processing ◽

Thermal Degradation Kinetics ◽

Poly Lactic Acid ◽

Opuntia Ficus Indica ◽

Model Free

This paper reports the effect of lignocellulosic flour and talc powder on the thermal degradation behavior of poly (lactic acid) (PLA) by thermogravimetric analysis (TGA). Lignocellulosic flour was obtained by grinding Opuntia Ficus Indica cladodes. PLA/talc/ Opuntia Ficus Indica flour (OFI-F) biocomposites were prepared by melt processing and characterized using Wide-angle X-ray scattering (WAXS) and Scanning Electron Microscope (SEM). The thermal degradation of neat PLA and its biocomposites can be identified quantitatively by solid-state kinetics models. Thermal degradation results on biocomposites compared to neat PLA show that talc particles at 10 wt % into the PLA matrix have a minor impact on the thermal stability of biocomposites. Loading OFI-F and Talc/OFI-F mixture into the PLA matrix results in a decrease in the maximum degradation temperature, which means that the biocomposites have lower thermal stability. The activation energies (Ea) calculated by the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) model-free approaches and by model-fitting (Kissinger method and Coats-Redfern method) are in good agreement with one another. In addition, in this work, the degradation mechanism of biocomposites is proposed using Coats-Redfern and Criado methods.

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