Lignin is a natural polymer,second only to cellulose in natural reserves.Degradation is one of the ways to achieve the high-value transformation of lignin.Deep eutectic solvent(DES)thermal degradation of lignin can be...Lignin is a natural polymer,second only to cellulose in natural reserves.Degradation is one of the ways to achieve the high-value transformation of lignin.Deep eutectic solvent(DES)thermal degradation of lignin can be used as an excellent green degradation method.This paper introduces the degradation mechanism and effect of the lactic acid-choline chloride DES system in dissolving and degrading alkaline lignin,and the final solvent recovery.It can also be found from the scanning electron microscope(SEM)images that the surface of the degraded solid product is transformed from smooth to disordered.Fourier transform infrared(FTIR)spectroscopy and 1H-NMR spectroscopy were used to characterize the changes in lignin functional groups during DES treatment.The results showed that the content of phenolic hydroxyl groups increased after degradation,indicating that theβ-O-4 ether bond was broken.The molecular weight of the degraded lignin was observed by gel permeation chromatography(GPC),and the lignin residue with low molecular weight and narrow polydispersity index was obtained.The lowest average molecular weight(Mw)reached 2512 g/mol.The ratio of oxygen to carbon atoms in lignin increased substantially during degradation as measured by X-ray photoelectron spectroscopy(XPS),probably because DES treatment was accompanied by many oxidation reactions,which led to significant structural changes in lignin and a large number of ether bond breakage reactions during the reaction.The main final degradation products are aromatic monomers,vanillin,butyrovanillone,etc.展开更多
Diatomite-based porous ceramics were adopted as carriers to immobilize nano-TiO_2 via a hydrolysis-deposition technique. The thermal degradation of as-prepared composites was investigated using thermogravimetric–diff...Diatomite-based porous ceramics were adopted as carriers to immobilize nano-TiO_2 via a hydrolysis-deposition technique. The thermal degradation of as-prepared composites was investigated using thermogravimetric–differential thermal analysis, and the phase and microstructure were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicated that the carriers were encapsulated by nano-TiO_2 with a thickness of 300–450 nm. The main crystalline phase of TiO_2 calcined at 650℃ was anatase, and the average grain size was 8.3 nm. The FT-IR absorption bands at 955.38 cm^(-1) suggested that new chemical bonds among Ti, O, and Si had formed in the composites. The photocatalytic(PC) activity of the composites was investigated under UV irradiation. Furthermore, the photodegradation kinetics of formaldehyde was investigated using the composites as the cores of an air cleaner. A kinetics study showed that the reaction rate constants of the gas-phase PC reaction of formaldehyde were κ = 0.576 mg·m^(–3)·min^(–1) and K = 0.048 m^3/mg.展开更多
Analytical method for the residues of strobilurins azoxystrobin and pyraclostrobin in blueberries was developed. Fungicide residues were determined by solid-phase microextraction (SPME) cou-pled to gas chromatography ...Analytical method for the residues of strobilurins azoxystrobin and pyraclostrobin in blueberries was developed. Fungicide residues were determined by solid-phase microextraction (SPME) cou-pled to gas chromatography with micro-electron capture detector. The effect of pH values and fiber coatings were studied. The SPME fiber coating selected was 100 μm PDMS. The method is selective with adequate precision and high accuracy and sensitivity. Recoveries ranged within the 100% - 106% range for azoxystrobin, and 96% - 106% range for pyraclostrobin;and detection and quantification limits were 2.0 and 6.0 μg/kg for azoxystrobin, and 26.0 and 86.0 μg/kg for py-raclostrobin, respectively. Statistical parameters indicated the occurrence of matrix effect;con-sequently calibration was performed on spiked samples. Degradation of azoxystrobin and pyra-clostrobin was studied in blueberry fields located in Concordia, Argentina, with fruits from Emerald and Jewel varieties. The degradation of these fungicides in both blueberry varieties studied followed a first order rate kinetics, and the half-life for azoxystrobin was 11.6 and 17.8 days for Emerald and Jewel cultivars;and for pyraclostrobin was 5.5 and 8.0 days, respectively.展开更多
The effects of oxidant dosage,oxidation temperature and time on the degradation of soda lignin by hydrogen peroxide with and without the presence of microwave irradiation were investigated.It is found that the oxidati...The effects of oxidant dosage,oxidation temperature and time on the degradation of soda lignin by hydrogen peroxide with and without the presence of microwave irradiation were investigated.It is found that the oxidative degradation of lignin includes the cleavage of ether bond inβ-O-4 structure,the partial destruction of aromatic ring,and the re-condensation of the degraded lignin.Compared to the conventionally heated oxidation of lignin,the microwave irradiation efficiently facilitates the degradation of the lignin with high molecular weight and the re-condensation of that with low molecular weight at a low oxidant dosage,low oxidation temperature,or a short oxidation time,which leads to the formation of the degraded lignin with narrower molecular weight distribution and lower molecular weight.Additionally,the lignin degraded in the presence of microwave irradiation has the characteristics of higher content of phenolic hydroxyl group,lower content of methoxyl group,and lower degree of condensation,which enhances the reactivity of lignin.Therefore,the oxidative degradation of lignin assisted by microwave irradiation may be a new pretreatment approach for efficiently utilizing the soda lignin.展开更多
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-phas...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.展开更多
Kinetics of photocatalytic degradation of methylene blue(MB) over Ca Ti O3 was studied. Effects of the solution p H, the MB concentration, the Ca Ti O3 dosage, and the type of light source on photocatalytic degradatio...Kinetics of photocatalytic degradation of methylene blue(MB) over Ca Ti O3 was studied. Effects of the solution p H, the MB concentration, the Ca Ti O3 dosage, and the type of light source on photocatalytic degradation rate of MB over Ca Ti O3 were investigated in detail. The results show that photocatalytic degradation of MB over Ca Ti O3 followed the first-order reaction. The apparent rate constant(kobs) of MB significantly increased with increasing solution p H while it greatly decreased with increasing MB concentration. The kobs of MB increased with increasing Ca Ti O3 dosage from 0.05 to 0.1 g, whereas it slightly decreased with increasing Ca Ti O3 dosage in the range of 0.1-0.4 g. The kobs of MB under UV-visible light irradiation was larger by factors of 2.2 than that under visible light irradiation. The kobs of MB was(4.8±0.3)×10-1h-1 under optimal conditions with the solution p H of 11, the MB concentration of 1 ppm, the Ca Ti O3 dosage of 0.1 g, and UV-visible light irradiation.展开更多
The curing process of two biobased adhesives:pine tanninhexamine(TH)and organosolv lignin non-isocyanate polyurethane(NIPU),suitable for interior nonstructural use,were compared with commercial urea-formaldehyde(UF)ad...The curing process of two biobased adhesives:pine tanninhexamine(TH)and organosolv lignin non-isocyanate polyurethane(NIPU),suitable for interior nonstructural use,were compared with commercial urea-formaldehyde(UF)adhesive.Changes in chemical structure before and after the curing process were observed with Fouriertransform infrared spectroscopy(FTIR).The process of adhesive curing was monitored with differential scanning calorimetry(DSC)and the automated bonding evaluation system(ABES).Both DSC and ABES measurements confirmed UF as the fastest and NIPU as the slowest curing adhesive observed.Taking into account the ABES results,the optimal pressing parameters for the TH adhesive would be 4 min at 175℃,for the NIPU adhesive 7 min at 200℃and for the UF 1.5 min at 100℃.Strong linear correlation was observed between mechanical and chemical curing for the UF and NIPU adhesives,whereas lower correlation was observed for the TH adhesive.At all observed adhesives,the DSC measurements were underestimating the curing process determined by ABES in the first part and overestimating it at the end.The underestimation was the most evident with the TH adhesive and the less with the UF adhesive.When comparing the uncured and cured FTIR spectra of all three types of adhesives,a drastic decrease in the characteristic band of-OH groups at 3330–3400 cm^(−1)and an increase in the signal intensity at 2920 cm^(−1)of aliphatic-CH2-groups were observed.For the UF adhesive,the C=O stretching frequency has shifted from 1632 cm^(−1)for uncured to three different bands at 1766,1701,and 1655 cm^(−1)for cured UF.The sharp band for phenolic alcohols at 1236 cm^(−1)of C–O stretch and hydroxyl O–H functional group at 1009 cm^(−1)and at 684 cm^(−1)of uncured TH adhesive diminished during curing,which indicates that a crosslinking reaction occurs via-OH groups.The peak of the C=O group of urethane bridges at 1697 cm^(−1)for uncured NIPU shifted to lower wavenumber at 1633 cm^(−1)for cured NIPU.展开更多
A new polymer,poly(imino isophthaloyl imino(2,4,8,10-tetraoksoaspiro[5,5]undekan-3,9-dipropylene)) [poly(IPIT)]was synthesized by an interfacial polycondensation reaction.The characterization of poly(IPIT)was conducte...A new polymer,poly(imino isophthaloyl imino(2,4,8,10-tetraoksoaspiro[5,5]undekan-3,9-dipropylene)) [poly(IPIT)]was synthesized by an interfacial polycondensation reaction.The characterization of poly(IPIT)was conducted by using FT-IR,^(13)C-NMR,TG and DTA techniques.The kinetics of the thermal degradation of poly(IPIT)was investigated by thermogravimetric analysis at different heating rates.TG curves showed that the thermal decomposition of poly(IPIT) occurred in three stages.The apparent activation ener...展开更多
As a natural aromatic polymer,lignin has great potential but limited industrial application due to its complex chemical structure.Among strategies for lignin conversion,biodegradation has attracted promising interest ...As a natural aromatic polymer,lignin has great potential but limited industrial application due to its complex chemical structure.Among strategies for lignin conversion,biodegradation has attracted promising interest recently in term of efficiency,selectivity and mild condition.In order to overcome the issues of poor stability and non-reusability of enzyme in the biodegradation of lignin,this work explored a protocol of immobilized laccase on magnetic nanoparticles(MNPs)with rough surfaces for enhanced lignin model compounds degradation.Scanning electron microscope with energy dispersive spectrometer(SEM-EDS),flourier transformation infrared spectroscopy(FTIR)and thermal gravimetric analysis(TGA)were utilized to characterize the immobilization of laccase.The results showed a maximum activity recovery of 64.7%towards laccase when it was incubated with MNPs and glutaraldehyde(GA)with concentrations of 6 mg·ml^-1and 7.5 mg·ml^-1for 5 h,respectively.The immobilized laccase showed improved thermal stability and pH tolerance compared with free laccase,and remained more than 80%of its initial activity after 20 days of storage at 4℃.In addition,about 40%residual activity of the laccase remained after 8 times cycles.Gas chromatography–mass spectrometry(GC–MS)was utilized to characterize the products of lignin model compound degradation and activation,and the efficiency of immobilized laccase was calculated to be 1–5 times that of free laccase.It was proposed that the synergistic effect between MNPs and laccase displays an important role in the enhancement of stability and activity in lignin model compound biodegradation.展开更多
Objective To investigate the kinetics of quinoline biodegradation by Burkholderia pickttii, a Gram negative rod-shaped aerobe, isolated in our laboratory. Methods HPLC (Hewlett-Packard model 5050 with an UV detector) ...Objective To investigate the kinetics of quinoline biodegradation by Burkholderia pickttii, a Gram negative rod-shaped aerobe, isolated in our laboratory. Methods HPLC (Hewlett-Packard model 5050 with an UV detector) was used for the analysis of quinoline concentration. GC/MS method was used to identify the intermediate metabolites of quinoline degradation. Results The biodegradation of quinoline was inhibited by quinoline at a high concentration, and the degradation process could be described by the Haldane model. The kinetic parameters based on Haldane substrate inhibition were evaluated. The values were vmax= 0.44 h-1, Ks=166.7 mg/L, Ki= 650 mg/L, respectively.The quinoline concentration to avoid substrate inhibition was inferred theoretically and determined to be 329 mg/L. Conclusion The biodegradation of quinoline conforms to the Haldane inhibition model and the main intermediate metabolite of quinoline biodegradation is 2-hydroxy-quinoline.展开更多
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 ch...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.展开更多
Thermal degradation kinetics of anthocyanins and visual color (Hunter a* value) of blood orange juice were studied at selected temperatures (70-90°C). Results indicated that both the thermal degradation of anthoc...Thermal degradation kinetics of anthocyanins and visual color (Hunter a* value) of blood orange juice were studied at selected temperatures (70-90°C). 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 mol-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: a*/a0*=0.559(C/C0)+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.展开更多
An innovative photoelectrode, B 2O 3·TiO 2/Ti electrode, was prepared by galvanostaticanodisation. The morphology and crystalline texture of the B 2O 3·TiO 2 film on electrode were examined by atomic force m...An innovative photoelectrode, B 2O 3·TiO 2/Ti electrode, was prepared by galvanostaticanodisation. The morphology and crystalline texture of the B 2O 3·TiO 2 film on electrode were examined by atomic force microscopy(AFM) and X-ray diffraction respectively. The examination results indicated that the anatase was the dominant component. The kinetics of photoelectrocatalytic(PEC) degradation of humic acid(HA) was investigated; the results demonstrated that effects from strongness to weakness on the photoelectrocatalytic degraded rate of humic acid: power of UV-lamp, area of TiO 2 film, bias, original concentration of humic acid solution. The optimum conditions were power of UV-lamp 125 W, area of TiO 2 film 42.0 cm 2, bias 1.4 V, original concentration of humic acid solution 5 mg/L in this PEC reaction system.展开更多
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 fac...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.展开更多
Cyhalodiamide is a novel agrochemical which is effective against Lepidoptera pests,including Cnaphalocrocis medinalis,Chilo suppressalis,Pieris rapae,Plutella xylostella,Helicoverpa armigera,etc.In the study,a fast an...Cyhalodiamide is a novel agrochemical which is effective against Lepidoptera pests,including Cnaphalocrocis medinalis,Chilo suppressalis,Pieris rapae,Plutella xylostella,Helicoverpa armigera,etc.In the study,a fast and accurate analytical method was developed to detect cyhalodiamide in Chinese typical rice field environment by a modified Qu ECh ERS(Quick,Easy,Cheap,Effective,Rugged,Safe)method with UPLC-MS/MS(ultra-high performance chromatography-tandem mass spectrometry).The mean recoveries of cyhalodiamide varied from 73.5% to 107.5%,with the RSDs from 1.2% to 10.7%.The limits of determination(LODs)were 0.0005 mg·kg^(-1),and the limits of quantitation(LOQs)were from 0.002 to 0.01 mg·kg^(-1)in all five matrices.This method was used to determine cyhalodiamide residues for studies of the distribution and degradation kinetics in rice field environment.The field trials results showed that cyhalodiamide was easily degradable and the half-lives were4.2–13.6 d in rice straw,8.77 d in paddy soil and 5.37–8.45 d in paddy water,respectively.The final residues of cyhalodiamide in brown rice were below 0.35 mg·kg^(-1).The used dosage of 33.75 g·hm^(-2)with pre-harvest interval(PHI)of 21 d and the maximum residue limit(MRL)of cyhalodiamide in rice at 0.1 mg·kg^(-1)were recommended,which would be safe to human health and environment.The developed analytical method will be useful to monitor cyhalodiamide residues and safety evaluation in rice environment.展开更多
Based on the theory of substrate permeation through the cytoplasmic membrane,and considering the effect of initial concentration of substrate,a new kinetic model of phenol degradation process was proposed,Comparing wi...Based on the theory of substrate permeation through the cytoplasmic membrane,and considering the effect of initial concentration of substrate,a new kinetic model of phenol degradation process was proposed,Comparing with the widely used Haldane model,which is greatly dependent on the initial phenol concentration,our model can be used to simulate the phenol degradation process in a wide range of initial phenol concentration by using only one set of model parameters ,Therefore,this new kinetic model has much more potential applications to industrial design and operation.展开更多
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 degradat...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.展开更多
The thermal degradation behavior of 4, 4-bishydroxydeoxybenzoin-polyphosphonate( BHDB-PPN) was investigated by gas chromatograph-mass spectrometer( GC-MS)and thermogravimetric analysis( TGA). It was found that BHDBPPN...The thermal degradation behavior of 4, 4-bishydroxydeoxybenzoin-polyphosphonate( BHDB-PPN) was investigated by gas chromatograph-mass spectrometer( GC-MS)and thermogravimetric analysis( TGA). It was found that BHDBPPN exhibited a different char formation way from the previous proposed mechanism based on the residue analysis by Fourier transform infrared spectra( FTIR) and the gas phase analysis by GC-MS. The thermal degradation kinetics was studied through TGA at various heating rates to identify the activation energy of BHDBPPN at two decomposition stages which were mainly attributed to the evolved phenol and benzene respectively. It was demonstrated that the activation energy at the second stage was much higher than that at the first stage,indicating that more energy was required to break the P—C bond to form benzene in comparison to the formation of phenol.展开更多
In this study,sulfur-doped TiO2 /Ti photoelectrodes were prepared by anodization. The morphology, crystalline structure,composition of sulfur-doped TiO2 /Ti film and light absorption property were examined by SEM,XRD,...In this study,sulfur-doped TiO2 /Ti photoelectrodes were prepared by anodization. The morphology, crystalline structure,composition of sulfur-doped TiO2 /Ti film and light absorption property were examined by SEM,XRD,XRF,XPS and UV/VIS respectively. Dimethyl phthalate( DMP) ,one kind of environmental disrupting chemicals( EDCs) ,was degraded by the optimized photoelectrodes. Power of xenon light,initial concentration of DMP,photoelectrocatalytic( PEC) area of photoelectrode and bias were investigated in the study on kinetics of PEC degradation of DMP. Hence,this study concluded that the optimum conditions were power of xenon light 150 W,initial concentration of DMP 1 mg/L,PEC area of sulfur-doped TiO2 /Ti photoelectrode 10 cm2,bias 1. 3 V in the PEC reaction system.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(31730106).
文摘Lignin is a natural polymer,second only to cellulose in natural reserves.Degradation is one of the ways to achieve the high-value transformation of lignin.Deep eutectic solvent(DES)thermal degradation of lignin can be used as an excellent green degradation method.This paper introduces the degradation mechanism and effect of the lactic acid-choline chloride DES system in dissolving and degrading alkaline lignin,and the final solvent recovery.It can also be found from the scanning electron microscope(SEM)images that the surface of the degraded solid product is transformed from smooth to disordered.Fourier transform infrared(FTIR)spectroscopy and 1H-NMR spectroscopy were used to characterize the changes in lignin functional groups during DES treatment.The results showed that the content of phenolic hydroxyl groups increased after degradation,indicating that theβ-O-4 ether bond was broken.The molecular weight of the degraded lignin was observed by gel permeation chromatography(GPC),and the lignin residue with low molecular weight and narrow polydispersity index was obtained.The lowest average molecular weight(Mw)reached 2512 g/mol.The ratio of oxygen to carbon atoms in lignin increased substantially during degradation as measured by X-ray photoelectron spectroscopy(XPS),probably because DES treatment was accompanied by many oxidation reactions,which led to significant structural changes in lignin and a large number of ether bond breakage reactions during the reaction.The main final degradation products are aromatic monomers,vanillin,butyrovanillone,etc.
基金financially supported by the National Natural Science Foundation of China (No. 50708037)the National Science Fund for Excellent Young Scholars of China (No. 51522402)+1 种基金the Science and Technology Research Projects in Zhengzhou (No. 141PPTGG388)the National Innovation and Entrepreneurship Training Program of the Undergraduate (No. 201610078034)
文摘Diatomite-based porous ceramics were adopted as carriers to immobilize nano-TiO_2 via a hydrolysis-deposition technique. The thermal degradation of as-prepared composites was investigated using thermogravimetric–differential thermal analysis, and the phase and microstructure were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicated that the carriers were encapsulated by nano-TiO_2 with a thickness of 300–450 nm. The main crystalline phase of TiO_2 calcined at 650℃ was anatase, and the average grain size was 8.3 nm. The FT-IR absorption bands at 955.38 cm^(-1) suggested that new chemical bonds among Ti, O, and Si had formed in the composites. The photocatalytic(PC) activity of the composites was investigated under UV irradiation. Furthermore, the photodegradation kinetics of formaldehyde was investigated using the composites as the cores of an air cleaner. A kinetics study showed that the reaction rate constants of the gas-phase PC reaction of formaldehyde were κ = 0.576 mg·m^(–3)·min^(–1) and K = 0.048 m^3/mg.
文摘Analytical method for the residues of strobilurins azoxystrobin and pyraclostrobin in blueberries was developed. Fungicide residues were determined by solid-phase microextraction (SPME) cou-pled to gas chromatography with micro-electron capture detector. The effect of pH values and fiber coatings were studied. The SPME fiber coating selected was 100 μm PDMS. The method is selective with adequate precision and high accuracy and sensitivity. Recoveries ranged within the 100% - 106% range for azoxystrobin, and 96% - 106% range for pyraclostrobin;and detection and quantification limits were 2.0 and 6.0 μg/kg for azoxystrobin, and 26.0 and 86.0 μg/kg for py-raclostrobin, respectively. Statistical parameters indicated the occurrence of matrix effect;con-sequently calibration was performed on spiked samples. Degradation of azoxystrobin and pyra-clostrobin was studied in blueberry fields located in Concordia, Argentina, with fruits from Emerald and Jewel varieties. The degradation of these fungicides in both blueberry varieties studied followed a first order rate kinetics, and the half-life for azoxystrobin was 11.6 and 17.8 days for Emerald and Jewel cultivars;and for pyraclostrobin was 5.5 and 8.0 days, respectively.
基金Supported by the National Natural Science Foundation of China（20876064） the Natural Science Foundation of Guangdong Province（9151064101000082） the Guangdong Provincial International Cooperation Fund（2008B05010006）
文摘The effects of oxidant dosage,oxidation temperature and time on the degradation of soda lignin by hydrogen peroxide with and without the presence of microwave irradiation were investigated.It is found that the oxidative degradation of lignin includes the cleavage of ether bond inβ-O-4 structure,the partial destruction of aromatic ring,and the re-condensation of the degraded lignin.Compared to the conventionally heated oxidation of lignin,the microwave irradiation efficiently facilitates the degradation of the lignin with high molecular weight and the re-condensation of that with low molecular weight at a low oxidant dosage,low oxidation temperature,or a short oxidation time,which leads to the formation of the degraded lignin with narrower molecular weight distribution and lower molecular weight.Additionally,the lignin degraded in the presence of microwave irradiation has the characteristics of higher content of phenolic hydroxyl group,lower content of methoxyl group,and lower degree of condensation,which enhances the reactivity of lignin.Therefore,the oxidative degradation of lignin assisted by microwave irradiation may be a new pretreatment approach for efficiently utilizing the soda lignin.
文摘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.
基金Funded by the National Natural Science Foundation of China(No.21407020)the Fundamental Research Fund for the Central Universities(No.N130302004)
文摘Kinetics of photocatalytic degradation of methylene blue(MB) over Ca Ti O3 was studied. Effects of the solution p H, the MB concentration, the Ca Ti O3 dosage, and the type of light source on photocatalytic degradation rate of MB over Ca Ti O3 were investigated in detail. The results show that photocatalytic degradation of MB over Ca Ti O3 followed the first-order reaction. The apparent rate constant(kobs) of MB significantly increased with increasing solution p H while it greatly decreased with increasing MB concentration. The kobs of MB increased with increasing Ca Ti O3 dosage from 0.05 to 0.1 g, whereas it slightly decreased with increasing Ca Ti O3 dosage in the range of 0.1-0.4 g. The kobs of MB under UV-visible light irradiation was larger by factors of 2.2 than that under visible light irradiation. The kobs of MB was(4.8±0.3)×10-1h-1 under optimal conditions with the solution p H of 11, the MB concentration of 1 ppm, the Ca Ti O3 dosage of 0.1 g, and UV-visible light irradiation.
基金the ERA-CoBioTech project WooBAdh(Environmentally-friendly bioadhesives from renewable resources)and by the Slovenian Ministry of Education.Science and Sport and the Slovenian Research Agency within the framework of the program P4-0015.
文摘The curing process of two biobased adhesives:pine tanninhexamine(TH)and organosolv lignin non-isocyanate polyurethane(NIPU),suitable for interior nonstructural use,were compared with commercial urea-formaldehyde(UF)adhesive.Changes in chemical structure before and after the curing process were observed with Fouriertransform infrared spectroscopy(FTIR).The process of adhesive curing was monitored with differential scanning calorimetry(DSC)and the automated bonding evaluation system(ABES).Both DSC and ABES measurements confirmed UF as the fastest and NIPU as the slowest curing adhesive observed.Taking into account the ABES results,the optimal pressing parameters for the TH adhesive would be 4 min at 175℃,for the NIPU adhesive 7 min at 200℃and for the UF 1.5 min at 100℃.Strong linear correlation was observed between mechanical and chemical curing for the UF and NIPU adhesives,whereas lower correlation was observed for the TH adhesive.At all observed adhesives,the DSC measurements were underestimating the curing process determined by ABES in the first part and overestimating it at the end.The underestimation was the most evident with the TH adhesive and the less with the UF adhesive.When comparing the uncured and cured FTIR spectra of all three types of adhesives,a drastic decrease in the characteristic band of-OH groups at 3330–3400 cm^(−1)and an increase in the signal intensity at 2920 cm^(−1)of aliphatic-CH2-groups were observed.For the UF adhesive,the C=O stretching frequency has shifted from 1632 cm^(−1)for uncured to three different bands at 1766,1701,and 1655 cm^(−1)for cured UF.The sharp band for phenolic alcohols at 1236 cm^(−1)of C–O stretch and hydroxyl O–H functional group at 1009 cm^(−1)and at 684 cm^(−1)of uncured TH adhesive diminished during curing,which indicates that a crosslinking reaction occurs via-OH groups.The peak of the C=O group of urethane bridges at 1697 cm^(−1)for uncured NIPU shifted to lower wavenumber at 1633 cm^(−1)for cured NIPU.
文摘A new polymer,poly(imino isophthaloyl imino(2,4,8,10-tetraoksoaspiro[5,5]undekan-3,9-dipropylene)) [poly(IPIT)]was synthesized by an interfacial polycondensation reaction.The characterization of poly(IPIT)was conducted by using FT-IR,^(13)C-NMR,TG and DTA techniques.The kinetics of the thermal degradation of poly(IPIT)was investigated by thermogravimetric analysis at different heating rates.TG curves showed that the thermal decomposition of poly(IPIT) occurred in three stages.The apparent activation ener...
基金supported by the Startup Foundation of Beijing Institute of Technology,China(3160011181808)。
文摘As a natural aromatic polymer,lignin has great potential but limited industrial application due to its complex chemical structure.Among strategies for lignin conversion,biodegradation has attracted promising interest recently in term of efficiency,selectivity and mild condition.In order to overcome the issues of poor stability and non-reusability of enzyme in the biodegradation of lignin,this work explored a protocol of immobilized laccase on magnetic nanoparticles(MNPs)with rough surfaces for enhanced lignin model compounds degradation.Scanning electron microscope with energy dispersive spectrometer(SEM-EDS),flourier transformation infrared spectroscopy(FTIR)and thermal gravimetric analysis(TGA)were utilized to characterize the immobilization of laccase.The results showed a maximum activity recovery of 64.7%towards laccase when it was incubated with MNPs and glutaraldehyde(GA)with concentrations of 6 mg·ml^-1and 7.5 mg·ml^-1for 5 h,respectively.The immobilized laccase showed improved thermal stability and pH tolerance compared with free laccase,and remained more than 80%of its initial activity after 20 days of storage at 4℃.In addition,about 40%residual activity of the laccase remained after 8 times cycles.Gas chromatography–mass spectrometry(GC–MS)was utilized to characterize the products of lignin model compound degradation and activation,and the efficiency of immobilized laccase was calculated to be 1–5 times that of free laccase.It was proposed that the synergistic effect between MNPs and laccase displays an important role in the enhancement of stability and activity in lignin model compound biodegradation.
基金The work was supported by the National Natural Science Foundation of China (Grant No. 29637010 50325824).
文摘Objective To investigate the kinetics of quinoline biodegradation by Burkholderia pickttii, a Gram negative rod-shaped aerobe, isolated in our laboratory. Methods HPLC (Hewlett-Packard model 5050 with an UV detector) was used for the analysis of quinoline concentration. GC/MS method was used to identify the intermediate metabolites of quinoline degradation. Results The biodegradation of quinoline was inhibited by quinoline at a high concentration, and the degradation process could be described by the Haldane model. The kinetic parameters based on Haldane substrate inhibition were evaluated. The values were vmax= 0.44 h-1, Ks=166.7 mg/L, Ki= 650 mg/L, respectively.The quinoline concentration to avoid substrate inhibition was inferred theoretically and determined to be 329 mg/L. Conclusion The biodegradation of quinoline conforms to the Haldane inhibition model and the main intermediate metabolite of quinoline biodegradation is 2-hydroxy-quinoline.
基金funded by the Natural Science Foundation of Hubei Province, China(2006ABA168)
文摘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.
基金funded by the Natural Science Foundation of Hubei Province,China(2006ABA168)
文摘Thermal degradation kinetics of anthocyanins and visual color (Hunter a* value) of blood orange juice were studied at selected temperatures (70-90°C). 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 mol-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: a*/a0*=0.559(C/C0)+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.
文摘An innovative photoelectrode, B 2O 3·TiO 2/Ti electrode, was prepared by galvanostaticanodisation. The morphology and crystalline texture of the B 2O 3·TiO 2 film on electrode were examined by atomic force microscopy(AFM) and X-ray diffraction respectively. The examination results indicated that the anatase was the dominant component. The kinetics of photoelectrocatalytic(PEC) degradation of humic acid(HA) was investigated; the results demonstrated that effects from strongness to weakness on the photoelectrocatalytic degraded rate of humic acid: power of UV-lamp, area of TiO 2 film, bias, original concentration of humic acid solution. The optimum conditions were power of UV-lamp 125 W, area of TiO 2 film 42.0 cm 2, bias 1.4 V, original concentration of humic acid solution 5 mg/L in this PEC reaction system.
基金the China Petroleum&Chemical Science and Technology Foundation(No.205026)the Tianjin Science andTechnology Plan Foundation,China(No.06TXTJJC14400).
文摘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.
基金Supported by the National Key Research and Development Plan(2016YFD020120)the Natural Science Foundation of Hunan Province(2017JJ3165)
文摘Cyhalodiamide is a novel agrochemical which is effective against Lepidoptera pests,including Cnaphalocrocis medinalis,Chilo suppressalis,Pieris rapae,Plutella xylostella,Helicoverpa armigera,etc.In the study,a fast and accurate analytical method was developed to detect cyhalodiamide in Chinese typical rice field environment by a modified Qu ECh ERS(Quick,Easy,Cheap,Effective,Rugged,Safe)method with UPLC-MS/MS(ultra-high performance chromatography-tandem mass spectrometry).The mean recoveries of cyhalodiamide varied from 73.5% to 107.5%,with the RSDs from 1.2% to 10.7%.The limits of determination(LODs)were 0.0005 mg·kg^(-1),and the limits of quantitation(LOQs)were from 0.002 to 0.01 mg·kg^(-1)in all five matrices.This method was used to determine cyhalodiamide residues for studies of the distribution and degradation kinetics in rice field environment.The field trials results showed that cyhalodiamide was easily degradable and the half-lives were4.2–13.6 d in rice straw,8.77 d in paddy soil and 5.37–8.45 d in paddy water,respectively.The final residues of cyhalodiamide in brown rice were below 0.35 mg·kg^(-1).The used dosage of 33.75 g·hm^(-2)with pre-harvest interval(PHI)of 21 d and the maximum residue limit(MRL)of cyhalodiamide in rice at 0.1 mg·kg^(-1)were recommended,which would be safe to human health and environment.The developed analytical method will be useful to monitor cyhalodiamide residues and safety evaluation in rice environment.
基金Supported by China Petroleum & Chemical Corporation (X599011).
文摘Based on the theory of substrate permeation through the cytoplasmic membrane,and considering the effect of initial concentration of substrate,a new kinetic model of phenol degradation process was proposed,Comparing with the widely used Haldane model,which is greatly dependent on the initial phenol concentration,our model can be used to simulate the phenol degradation process in a wide range of initial phenol concentration by using only one set of model parameters ,Therefore,this new kinetic model has much more potential applications to industrial design and operation.
文摘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.
基金National Natural Science Foundation of China(No.51473031)Natural Science Foundation of Shanghai,China(No.15ZR1401100)
文摘The thermal degradation behavior of 4, 4-bishydroxydeoxybenzoin-polyphosphonate( BHDB-PPN) was investigated by gas chromatograph-mass spectrometer( GC-MS)and thermogravimetric analysis( TGA). It was found that BHDBPPN exhibited a different char formation way from the previous proposed mechanism based on the residue analysis by Fourier transform infrared spectra( FTIR) and the gas phase analysis by GC-MS. The thermal degradation kinetics was studied through TGA at various heating rates to identify the activation energy of BHDBPPN at two decomposition stages which were mainly attributed to the evolved phenol and benzene respectively. It was demonstrated that the activation energy at the second stage was much higher than that at the first stage,indicating that more energy was required to break the P—C bond to form benzene in comparison to the formation of phenol.
基金Sponsored by the National Natural Science Foundation of China ( Grant No 50678044)
文摘In this study,sulfur-doped TiO2 /Ti photoelectrodes were prepared by anodization. The morphology, crystalline structure,composition of sulfur-doped TiO2 /Ti film and light absorption property were examined by SEM,XRD,XRF,XPS and UV/VIS respectively. Dimethyl phthalate( DMP) ,one kind of environmental disrupting chemicals( EDCs) ,was degraded by the optimized photoelectrodes. Power of xenon light,initial concentration of DMP,photoelectrocatalytic( PEC) area of photoelectrode and bias were investigated in the study on kinetics of PEC degradation of DMP. Hence,this study concluded that the optimum conditions were power of xenon light 150 W,initial concentration of DMP 1 mg/L,PEC area of sulfur-doped TiO2 /Ti photoelectrode 10 cm2,bias 1. 3 V in the PEC reaction system.
