Thermal Degradation Kinetics of N,N'-Di(diethoxythiophosphoryl)-1,4-phenylenediamine

The non-isothermal degradation kinetics of N,N＇-di（diethoxythiophosphoryl）-1,4-phenylenediamine in N2 was studied by TG-DTG techniques.The kinetic parameters,including the activation energy and pre-exponential factor of the degradation process for the title compound were calculated by means of the Kissinger and Flynn-Wall-Ozawa（FWO）method and the thermal degradation mechanism of the title compound was also studied with the Satava-Sestak methods.The results indicate that the activation energy and pre-exponential factor are 152.61 kJ/mol and 9.06×101 4s -1with the Kissinger method and 154.08 kJ/mol with the Flynn-Wall-Ozawa method,respectively.It has been shown that the degradation of the title compound follows a kinetic model of one-dimensional diffusion or parabolic law,the kinetic function is G（α）=α2and the reaction order is n=2.

Thermal Degradation Kinetics of Three Kinds of Representative Anthocyanins Obtained from Blood Orange

Cyanidin-3-glucoside, cyanidin-3-（6′′-malonyl）-glucoside, and cyanidin-3-glucoside-derived pyranoanthocyanins which were three major anthocyanins of blood orange, were obtained using a Toyopearl TSK HW-40S column chromatography. Then, thermal degradation kinetics of the three major anthocyanins was studied at selected temperatures （70, 80, and 90°C）. Degradation parameters such as k and t1/2 values were determined. The activation energy （Ea） values for cyanidin- 3-glucoside, cyanidin-3-（6′′-malonyl）-glucoside and cyanidin-3-glucoside-derived pyranoanthocyanin were 75.4, 79.5, and 81.7 kJ mol-1, respectively. Ea values suggested that cyanidin-3-glucoside-derived pyranoanthocyanin had the highest stability, followed by cyanidin-3-（6′′-malonyl）-glucoside and cyanidin-3-glucoside. However, t1/2 values indicated cyanidin- 3-glucoside-derived pyranoanthocyanin degraded faster than cyanidin-3-（6′′-malonyl）-glucoside and cyanidin-3-glucoside at selected temperature.

Thermal Degradation Kinetics of Anthocyanins and Visual Color of Blood Orange Juice

Thermal degradation kinetics of anthocyanins and visual color （Hunter α value） of blood orange juice were studied at selected temperatures （70-90℃）. Results indicated that both the thermal degradation of anthocyanin and visual color all followed first-order reaction kinetics, and they could be expressed by Arrhenius equation. The activation energy values for the anthocyanins degradation and visual color degradation were 55.81 and 47.51 kJ tool-1, respectively. The linear relationship between visual color and anthocyanin content was obtained. Furthermore, during thermal processing of blood orange juice, the formulas about the linear relationships showed no significant difference at selected temperatures. So, the relationships between visual color and anthocyanins content during thermal processing at selected temperatures could be described by the same equation： α＊/αo＇=0.559（C/Co）＋0.43. It might be inferred that visual color measured instantaneously by tristimulus colorimeters for on-line quality control, could be used to predict the anthocyanins degradation during thermal processing of blood orange juice.

Study on degradation kinetics of epalrestat in aqueous solutions and characterization of its major degradation products under stress degradation conditions by UHPLC-PDA-MS/MS

Drug stability is closely related to drug safety and needs to be considered in the process of drug production,package and storage.To investigate the stability of epalrestat,a carboxylic acid derivative,a reversed-phase high-performance liquid chromatography(RP-HPLC)method was developed in this study and applied to analyzing the degradation kinetics of epalrestat in aqueous solutions in various conditions,such as different pH,temperatures,ionic strengths,oxidation and irradiation.The calibration curve was A=1.6×10^5C–1.3×10^3(r=0.999)with the liner range of 0.5–24μg/mL,the intra-day and inter-day precision was less than 2.0%,as was the repeatibility.The average accuracy for different concentrations was more than 98.5%,indicating that perfect recoveries were achieved.Degradation kinetic parameters such as degradation rate constants(k),activation energy(Ea)and shelf life(t0.9)under different conditions were calculated and discussed.The results indicated that the degradation behavior of epalrestat was pH-dependent and the stability of epalrestat decreased with the rised irradiation and ionic strength;however,it was more stable in neutral and alkaline conditions as well as lower temperatures.The results showed that the degradation kinetics of epalrestat followed first-order reaction kinetics.Furthermore,the degradation products of epalrestat under stress conditions were identified by UHPLC-PDA-MS/MS,with seven degradation products being detected and four of them being tentatively identified.

POSTMORTEM REDISTRIBUTION KINETICS OF ACONITINE IN RABBITS

The postmortem redistribution of aconitine(AC) and its influencing factors by orally ingested Aconitum brachypodum Diels (AbD) in rabbits were studied. The results showed that postmortem AC redistribution did exist, and the diffusion along a concentration gradient was the major influencing factor on it. Change of temperature and incomplete distribution in life also influenced it.Besides those mentioned above, there were other influencing factors. These may be related to postmortem blood movement and toxin released from cells occurring as part of the processes of autolysis and putrefaction.

Kinetics study of metaxalone degradation under hydrolytic, oxidative and thermal stress conditions using stability-indicating HPLC method

An isocratic stability indicating RP-HPLC-UV method is presented for the determina- tion of metaxalone （MET） in the presence of its degradation products. The method uses Dr. Maisch C18 column （250 mm × 4.6 mm, 5μm） with mobile phase consisting of acetonitrile-potassium dihydrogen orthophosphate buffer with 4 mL of 0.4% triethyl amine （pH 3.0; 10 mM） （58：42, v/v） at a flow rate of 1.0 mL/min, pH of the buffer was adjusted with o-phosphoric acid. UV detection was performed at 225 nm. The method was validated for specificity, linearity, precision, accuracy, limit of detection, limit of quantification and robustness. The calibration plot was linear over the concentration range of 1-100 μg/mL having a correlation coefficient （r2） of 0.999. Limits of detection and quantification were 0.3 and 1μg/mL, respectively. Intra-day and inter-day precision （% RSD） was 0.65 and 0.79 respectively. The proposed method was used to investigate the degradation kinetics of MET under different stress conditions employed. Degradation of MET followed a pseudo-first-order kinetics, and rate constant （K）, time left for 50% potency （t1/2）, and time left for 90% potency 090） were calculated.

STUDY OF ACONITINE DEGRADATION KINETICS IN RABBIT CORPSES

in order to research on the degradation kinetics rule or aconitine (AC) in rabbit corpses,in this article,through the acute intoxic models set up by orally administrating Aconitum brachypodum Diels (AbD) of absolute lethal dose (ALD) to New Zealand rabbits,the changing rules of aconitine degradation in tissues of rabbit corpses stored at 4℃ refrigirater were studied. The result showed that AC degradation process in rabbit corpses was apparent two-order degradation kinetics. AC degradation kinetics equations in liver and kidney were the half lives of them were 5.66 and 6. 47 days respectively.

Degradation kinetics of larotaxel and identification of its degradation products in alkaline condition

Larotaxel, a new taxane compound prepared by partial synthesis from 10-deacetyl baccatin III, is active against tumors. In this research, a selective LC–MS method was developed and validated for the study of degradation kinetics of larotaxel, which was carried out in aqueous solutions with different pH（1.5, 3.0, 5.0, 6.5, 7.4, 9.0, 10 and 11.0） and temperature（0, 25, 37 and 45 °C）. The linear range was 0.5–25 μg/mL, the intra-and inter-day precisions were less than 7.0%, and accuracy ranged from 97.4–104.5% for each analyte. The observed rate obtained by measuring the remaining intact larotaxel was shown to follow first-order kinetics. The activation energies for degradation were 126.7 and 87.01 k J/mol at pH 1.5 and 11, respectively. Although larotaxel was stable in pH 5, 6.5 and 7.4 buffers at 37 °C for 24 h during our study, increasing or decreasing the pH of the solutions would decrease its stabilities. Moreover, three main degradation products in alkaline condition were separated by HPLC and identified by Q–TOF–MS. The three degradation products were confirmed as 10-deacetyl larotaxel, 7, 8-cyclopropyl baccatin Ⅲ and 10-deacetyl-7, 8-cyclopropyl baccatin Ⅲ.

Efficient degradation of aqueous dichloromethane by an enhanced microbial electrolysis cell:Degradation kinetics,microbial community and metabolic mechanisms

Dichloromethane(DCM)has been listed as a toxic and harmful water pollutant,and its re moval needs attention.Microbial electrolysis cells(MECs)are viewed as a promising alterna tive for pollutant removal,which can be strengthened from two aspects:microbial inocula tion and acclimation.In this study,the MEC for DCM degradation was inoculated with the ac tive sludge enhanced by Methylobacterium rhodesianum H13(strain H13)and then acclimated in the form of a microbial fuel cell(MFC).Both the introduction of strain H13 and the initi ation in MFC form significantly promoted DCM degradation.The degradation kinetics were fitted by the Haldane model,with V_(max),K_(h),K_(i)and v_(max)values of 103.2 mg/L/hr,97.8 mg/L268.3 mg/L and 44.7 mg/L/hr/cm^(2),respectively.The cyclic voltammogram implies that DCM redox reactions became easier with the setup of MEC,and the electrochemical impedance spectrogram shows that the acclimated and enriched microbes reduced the charge transfe resistance from the electrode to the electrolyte.In the biofilm,the dominant genera shifted from Geobacter to Hyphomicrobium in acclimation stages.Moreover,Methylobacterium played an increasingly important role.DCM metabolism mainly occurred through the hydrolytic glutathione S-transferase pathway,given that the gene dcmA was identified rather than the dhlA and P450/MO.The exogenous electrons facilitated the reduction of GSSG,directly o indirectly accelerating the GSH-catalyzed dehalogenation.This study provides support fo the construction of an efficient and stable MEC for DCM removal in water environment.

Degradation of Anionic Dye Eosin by Glow Discharge Electrolysis Plasma

This paper describes a novel method for the degradation of eosin by using glow discharge electrolysis （GDE）. The effects of various parameters on the removal efficiency were studied. It was found that the eosin degradation could be raised considerably by increasing the applied voltage and the initial concentration, or by decreasing pH of the aqueous solution. Fe^2＋ ion had an evident accelerating effect on the eosin degradation. The degradation process of eosin obeyed a pseudo-first-order reaction. The relationship between the degradation rate constant k and the reaction temperature T could be expressed by Arrhenius equation with which the apparent activation energy Ea of 14.110 kJ· mol^-1 and the pre-exponential factor k0 of 2.065× 10^-1 min^-1 were obtained, too. The determination of hydroxyl radical was carried out by using N, N-dimethyl -p-nitrosoaniline （RNO） as a scavenger. The results showed that the hydroxyl radical plays an important role in the degradation process.

Photocatalytic degradation of methylene blue by nanostructured Fe/FeS powder under visible light

The photocatalytic performance of mechano-thermally synthesized Fe/FeS nanostructures formed from micron-sized starting materials was compared with that of a thermally synthesized nanostructure with nano-sized precursors in this paper. The properties of as-synthesized materials were studied by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, vibrating sample magnetometry（VSM）, diffuse reflectance spectroscopy（DRS）, and ultraviolet–visible（UV-Vis） spectroscopy. The effects of irradiation time, methylene blue（MB） concentration, catalyst dosage, and p H value upon the degradation of MB were studied. Magnetic properties of the samples showed that both as-synthesized Fe/FeS photocatalysts are magnetically recoverable, eliminating the need for conventional filtration steps. Degradation of 5 ppm of the MB solution by mechano-thermally synthesized Fe/FeS with a photocatalyst dosage of 1 kg/m^3 at pH 11 can reach 96% after 12 ks irradiation under visible light. The photocatalytic efficiency is higher in alkaline solution. The kinetics of photocatalytic degradation in both samples is controlled by a first-order reaction. However, the rate-constant value in the thermally synthesized Fe/FeS photocatalyst sample is only 1.5 times greater than that of the mechano-thermally synthesized one.

Degradation characteristics of two Bacillus strains on the Microcystis aeruginosa

The degradation kinetics of strains P05 and P07 and the degradation effects of mixed strain on Microcystis aeruginosa were studied. The results showed that: (1) The degradation processes of strains P05 and P07 on Microcystis aeruginosa accorded with the first-order reaction model when the range of Chl-a concentration was from 0 to 1500 μg/L. (2) The initial bacterium densities had a strong influence on the degradation velocity. The greater the initial bacterium density was, the faster the degradation was. The degradation velocity constants of P05 were 0.1913, 0.2175 and 0.3092 respectively, when bacterium densities were 4.8×10 5, 4.8×10 6, 2.4×10 7 cells/ml. For strain P07, they were 0.1509, 0.1647 and 0.2708. The degradation velocity constant of strain P05 was higher than that of P07 when the bacterium density was under 4.8×10 5 cells/ml, but the constant increasing of P07 was quicker than that of P05. (3) The degradation effects of P05 and P07 strains did not antagonize. When the concentration of Chl-a was high, the degradation effects of mixed strain excelled that of any single strains. But with the decrease of the Chl-a concentration, this advantage was not clear. When the concentration was less than 180 μg/L, the degradation effects of mixed were consistent with that of strain P07.

Degradation kinetic study of lysine in lysine hydrochloride solutions for injection by determining its main degradation product

A limited number of researches have been reported to apply the Arrhenius equation to study the relationship between drugs and its degradation products so far.In the present work,the thermal degradation kinetics of lysine hydrochloride solutions for injection,the special solvent for ademetionine 1,4-butanedisulfonate(SAM)for injection,was investigated at selected temperatures and pH values.The main degradation product of lysine was separated,purified,and confirmed as lysine lactam.A reversed-phase high performance liquid chromatographic(RP-HPLC)method without derivation was developed for the simultaneous determination of lysine and lysine lactam.The results confirmed that both the lysine degradation and lysine lactam generation followed zero-order reaction kinetics.The degradation and generation rate constants increased with increasing temperatures and decreasing pH values.The temperature-dependent degradation and generation reaction could be sufficiently modeled on the Arrhenius equation with the activation energy of 80.14 and 83.22 kJ/mol,respectively.Meanwhile,a linear relationship existed between the amount of lysine degradation and lysine lactam generation since the approximate activation energy.Considering there could be other side effects,we established an upper limit of lysine lactam(500 mg/ml),as the acceptable criteria for stability to estimate the shelf life together with lysine,which made the prediction more accurate and credible.Extrapolation data demonstrated that the lysine hydrochloride solutions for injection could be stable for two years stored at room temperature.

Effect of Graphene Nanoplatelets Presence on the Thermal and Mechanical Properties of Polypropylene Fibers Produced by Melt Spinning

In aiming to obtain fibers with enhanced thermal and mechanical properties,graphene based textile fibers with 144 filaments were developed using an approach in which the PP/GnP(polypropylene/graphene nanoplatelets)nanocomposite was employed as conductive material in a fiber with circular cross-section geometry.The kinetics of thermal degradation was evaluated by the Broido method using thermogravimetric analysis(TGA).Activation energy was enhanced from 260.6 kJ·mol^-1 to 337.4 kJ·mol^-1 compared to the neat PP.GnP increased the thermal stability of the PP,slowing its degradation by thermal depolymerization.Furthermore,the degree of crystallization declined as the GnP content increased,reducing the tenacity of the yarn,but improving its elastic modulus from 91.9 to 95.9 cN/tex,being a promising alternative to produce smart textiles.In conclusion,it has been confirmed that GnP loading up to 1%(w/w)can be incorporated into polypropylene by melt spinning and that the resulting nanocomposite fibers are suitable for several applications in the textile industry.

Treatment Processes of Leachate from a Landfill by Advanced Oxidation Fenton and Ozone-UV

In this paper it is presented the results of advanced oxidation of leachates from a technified sanitary landfill located in the State of Querétaro, Mexico. One characteristic of already stabilized leachates from sanitary landfills like this case, is their difficult degradation, mainly because the organic matter contained is recalcitrant. For the samples collect, four sites were selected, where three points per site were sampled, measuring at each site the parameters: temperature, pH, conductivity, redox potential (ORP) and dissolved oxygen (DO) and leachate samples were collected. On the other hand, the Chemical Oxygen Demand (COD) of crude leachates, leachates acidified and leachates oxidized by Fenton reagent and Ozone-UV combined were analyzed. COD was used to monitor the degradation kinetics. With the results, the ArcGIS software was applied to study the distribution of temperature, dissolved oxygen and COD mainly in the leachate lagoon. For the application of Fenton reagent in the crude leachate oxidation, the pH was first adjusted and Fe2+/H2O2 ratio was optimized. The efficiency of Ozone-UV treatments was studied through COD degradation kinetics. The graphs of in (Ci/Co) vs time, showed that the kinetic processes are of order one, with very acceptable regression coefficients (R2) and extraordinarily similar speed constants (K). With Fenton oxidation, the highest percentage of COD degradation was achieved and with Ozone-UV oxidation, it was possible to practically degrade all the COD.

Degradation behaviors of Nabumetone and its metabolite during UV/monochloramine process:Experimental and theoretical study

This study investigated degradation behaviors of a nonsteroidal anti-inflammatory drug Nabumetone(NMT)and its major metabolite 6-methoxy-2-naphthylacetic acid(MNA)in the coupling process of ultraviolet and monochloramine(UV/NH2Cl).The second-order rate constants of the contaminants reacting with reactive radicals(HO·,Cl·,Cl_(2)·-,and CO_(3)·^(-))were determined by laser flash photolysis experiments.HO·and Cl·contributed predominantly with 52.3%and 21.7%for NMT degradation and 60.8%and 22.3%for MNA degradation.The presence of chlorides retarded the degradation of NMT,while promoted the destruction of MNA,which was ascribed to the photosensitization effects of MNA under UV irradiation.Density functional theory(DFT)calculations revealed that radical adduct formation(RAF)was dominant pathway for both HO·and Cl·reacting with the contaminants,and hydrogen atom transfer(HAT)preferred to occur on side chains of NMT and MNA.NMT reacted with NO_(2)·through single electron transfer(SET)with the second-order rate constant calculated to be 5.35×10^(7)(mol/L)^(-1)sec^(-1),and the contribution of NO_(2)·was predicted to be 13.0%of the total rate constant of NMT in pure water,which indicated that NO_(2)·played a nonnegligible role in the degradation of NMT.The acute toxicity and developmental toxicity of NMT were enhanced after UV/NH_(2)Cl treatment,while those of MNA were alleviated.The transformation products of both NMT and MNA exhibited higher mutagenicity than their parent compounds.This study provides a deep understanding of the mechanism of radical degradation of NMT and MNA in the treatment of UV/NH2Cl.

Degradation kinetics of functional components of honeysuckle flowers during controlled-atmosphere heat pump drying

To investigate the change law of functional components and exterior color of honeysuckle flowers(HF)during controlled-atmosphere heat pump drying,nitrogen was used as drying medium in this study to reduce the oxygen concentration.The influences of drying temperature,HF’s loading amount and oxygen concentration on chlorogenic acid content,cynaroside content and L value(on behalf of browning degree)were explored,and the degradation kinetics models of chlorogenic acid and cynaroside were constructed.The results showed that chlorogenic acid content,cynaroside content and L value decreased with the rise of temperature,HF’s loading amount and oxygen concentration.The degradation kinetics models of chlorogenic acid and cynaroside during the drying process were established through introducing an exponent r related to time t in the first order reaction kinetics equation.The models had good fitting precision and can be used to predict the degradation law of chlorogenic acid and cynaroside.

Photocatalytic degradation of carbofuran in TiO_2 aqueous solution: Kinetics using design of experiments and mechanism by HPLC/MS/MS

The photocatalytic degradation kinetics of carbofuran was optimized by central composite design based on response surface methodology for the first time. Three variables, TiO2 concentration, initial pH value and the concentration of carbofuran, were selected to determine the dependence of degradation efficiencies on independent variables. Response surface methodology modeling results indicated that the degradation efficiency of carbofuran was highly affected by the initial pH value and the concentration of carbofuran. Then nine degradation intermediates were detected by HPLC/MS/MS. The Frontier Electron Densities of carbofuran were calculated to predict the active sites on carbofuran attacked by hydroxyl radicals and photoholes. Point charges were used to elucidate the chemisorption pattern on TiO2 catalysts during the photocatalytic process. By combining the experimental results and calculation data, the photocatalytic degradation pathways of carbofuran were proposed, including the addition of hydroxyl radicals and the cleavage of the carbamate side chain.

Thermal Degradation Kinetics of Structurally Diverse Poly(bispropargyl ethers-bismaleimide) Blends

Structurally diverse bispropargyl ethers using resorcinol,quinol,4,4￠-dihydroxy biphenyl,bisphenol-A,4,4￠-dihydroxy diphenyl ketone,4,4￠-dihydroxy diphenylsulphone,trimethyl indane bisphenol and tetramethyl spirobiindane bisphenol were prepared by using phase transfer catalyst.Synthesized materials were separately blended with 4,4￠-bismaleimido diphenyl methane（BMIM）in mole ratios（0.5：0.5）.The materials were thermally cured and the structural characterisation and the thermal properties of these cross-linked materials are investigated using Fourier-transform infrared（FTIR）spectrophotometer and thermogravimetric analyzer（TGA）.Among the different materials investigated poly MRPE,poly MBPEBPA and poly MSPE show higher onset degradation temperature of 300°C indicating higher thermal stability.The degradation kinetics is investigated using Flynn-Wall-Ozawa（FWO）,Vyazovkin（VYZ）and Friedman（FRD）methods.Amongst the various cured materials investigated,the activation energy（Ea-D）values obtained for poly MRPE and poly MKPE were observed to increase continuously froma=0.2 to 0.8 and the values range from 199 kJ/mol to 245 k J/mol and 153 k J/mol to 295 k J/mol respectively.The crosslinked materials resulting from these bispropargyl monomers definitely need more energy for bond cleavage due to the presence of more aromatic units.The volatile products obtained during the thermal degradation of the polymers were analyzed using thermogravimetric-Fourier transform infrared analyses（TG-FTIR）.The phenols,substituted phenols,carbon monoxide,carbon dioxide and small amount of aniline were found to be the major products during thermal degradation of these cured blends.

Kinetics and mechanism of thermal degradation of vegetable-tanned leather fiber

Thermal degradation of vegetable-tanned leather fiber(VLF)was investigated by thermogravimetric analysis aiming to know the exact kinetics and degradation mechanism.The thermogravimetric(TG)and differential thermogravimetric(DTG)curves showed that decomposition of the VLF occurs mainly in the range of 150-600℃,and the latter exhibits asymmetrical peak with a pronounced shoulder.The decomposition process was first analyzed by deconvolution of the experimental DTG curves,followed by reconstruction of the weight loss profiles of two individual processes.Several common isoconversional approaches were applied to calculate the activation energy over a wide range of conversion for the sample,including modified Kissinger-Akahira-Sunose(MKAS),Friedman,and Flynn-Wall-Ozawa.The average activation energy of vegetable-tanned leather fiber was found to be 241.9 kJ mol^(−1) by MKAS method.The activation energy values obtained for the pseudocomponents representing highly-crosslinked and low-crosslinked collagen in VLF were given as 190.6 and 124.8 kJ mol^(−1),respectively.Generalized master plots results suggested that the reaction mechanism for highly-crosslinked collagen follows the random nucleation and growth process at conversion values lower than 0.5.When the conversion is higher than 0.5,the mechanism tends to random scission model.For low-crosslinked collagen,the degradation is mainly governed by random nucleation and nuclei growth.The gaseous products of VLF thermal degradation were analyzed with an online-coupled TG-Fourier transform infrared spectroscopy system.