The efficacy of roasted sesame oil(SO)on the oxidation deterioration of sunflower oil(SFO)during heating was investigated.The concentrations of SO in the SFO were 0,10%,20%,and 30%by volume.The oxidation profile of oi...The efficacy of roasted sesame oil(SO)on the oxidation deterioration of sunflower oil(SFO)during heating was investigated.The concentrations of SO in the SFO were 0,10%,20%,and 30%by volume.The oxidation profile of oil samples was monitored by evaluating the generation of oxidation products and chemical alterations in the oils'composition during heating at frying temperature(180℃).The results showed that the oxidation parameters(free fatty acid,peroxide value,p-anisidine value,total oxidation status,thiobarbituric acid value,and color index)increased significantly in SFO compared to blends or SO during thermal treatment.During heating,the concentration of polyunsaturated fatty acids(PUFA)was reduced with increased level of saturated fatty acids;these results were observed more in SFO than those of SO or blend oils.However,the presence of SO in SFO reduced the decomposition of PUFA.In Fourier-transform infrared spectroscopy,the peak intensities were significantly altered in SFO compared to the blend oils during heating.Based on the most analytical data,it may be agreed that the heating at frying temperature led to the generation of relatively higher contents of oxidative products in SFO compared to blend oils,showing a lower degree of oxidation occurred in blends.The best frying performance for the SFO was achieved by using 30%SO extracted from the roasted sesame seed.This study showed the proper blending of high polyunsaturated oil with SO can produce oil blends with high nutritional values and enhanced stability for daily cooking and deep-frying applications.展开更多
In order to evaluate the thermal oxidation degradation behavior of lubricant with different antioxidants,the thermal kinetics equation based on the anlyses of thermogravimetry(TG),differential thermal analysis(DTA),an...In order to evaluate the thermal oxidation degradation behavior of lubricant with different antioxidants,the thermal kinetics equation based on the anlyses of thermogravimetry(TG),differential thermal analysis(DTA),and differential scanning calorimetry(DSC)was established,respectively,to calculate the activation energy of lubricant thermal-oxidative reaction.The thermal analyses of TG and DTA were employed to determine the thermal decomposition properties of ester oils trimethylolpropane trioleate(TMPTO)with butyl-octyl-diphenylamine/octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate/amine-phenol combination antioxidant.The activation energy of the lubricating oil adding antioxidant is increased relative to the TMPTO base oil,and the order of activation energy are Ec(93.732 kJ·mol^(-1))>Ed(88.71 kJ·mol^(-1))>Eb(58.41 kJ·mol^(-1))>Ea(46.32 kJ·mol^(-1)).The experimental results show that octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate in TMPTO has favorable resistance to thermal oxidation and decomposition.The thermal analysis method of DSC accurately reflects the heat exchange of lubricant thermal-oxidative reaction.The order of activation energy is calculated to ED(144.385 kJ·mol^(-1))>EC(110.05 kJ·mol^(-1))>EB(97.187 kJ·mol^(-1))>EA(66.02 kJ·mol^(-1)).It is illustrated that the amine-phenol combination antioxidant has the best thermal oxidation resistance,which is the same as what the oxidation onset temperature effected.展开更多
Degradation of dyes is an important environmental issue. In order to avoid the carcinogenic risks in anaerobic-aerobic biological process for wastewater containing azo dyes, a hemin based biomimetic oxidative degradat...Degradation of dyes is an important environmental issue. In order to avoid the carcinogenic risks in anaerobic-aerobic biological process for wastewater containing azo dyes, a hemin based biomimetic oxidative degradation of azo dyes was developed. Acid orange 7 (AO7) was selected as the model for azo dye and the high efficient degradation was achieved in hemin/H2O2 system at pH 11.0. Degradation could be described by a pseudo-first-order kinetic model. The order of dependence on H2O2 concentration was significantly larger than that of hemin. Coexisting anions sulphate and chloride had little effect on the degradation, but reductive sulphite dramatically inhibited the degradation. The protic solvent 2-prophanol obviously promoted the degradation. Azo chromogenic group was destroyed quickly and some smaller intermediates formed. Active species oxoferryl porphyrin p-cation radical +PFeIV=O generated from heterolytic cleavage of O-O in H2O2 catalyzed by hemin play the main roles in degradation and reaction pathways were proposed.展开更多
trichlorophenol (TCP) was firstly treated with air ions generated by electric discharge, and high dechlorination (53%) was observed after 60 min treatment, indicating that air ions are an efficient dechlorination mean...trichlorophenol (TCP) was firstly treated with air ions generated by electric discharge, and high dechlorination (53%) was observed after 60 min treatment, indicating that air ions are an efficient dechlorination means and might have a future in the oxidative removal of chlorinated phenols. In addition, a stepwise degradation of TCP, beginning with the formation of a major product 2,6-dichloro-1,4-benzenediol via substitution, is proposed through a detailed analysis of gas chromatography/mass spectrometry.展开更多
The study focused on the application of high-resolution mass spectrometry for the identification of impurities in pharmaceutical small molecules. A high-performance liquid chromatography (HPLC) coupled high resolution...The study focused on the application of high-resolution mass spectrometry for the identification of impurities in pharmaceutical small molecules. A high-performance liquid chromatography (HPLC) coupled high resolution mass spectrometer (HRMS) was used for identification of oxidative degradation impurities (DIs) of lansoprazole. The utilization of HRMS facilitates to determine the accurate mass of impurities and their fragment/product ions. A fast mass spectrometer (MS) compatible reverse phase chromatography method was used to investigate the oxidative stressed impurities. HPLC column;C18 (50 × 4.6 mm, 3.5 μm) was used with gradient elution. Spectral data acquired using information dependent acquisition (IDA) with real time dynamic background subtraction algorithm (DBS). Three oxidative impurities: DI-I (m/z 386.0781), DI-II (m/z 402.0734) and DI-III (m/z 386.0785), was observed during this study;interpretation of high resolution spectral data of all three impurities was carried out;elemental composition and molecular structure was proposed for major fragments. In this study mass error was found ≤7.7 parts per million (ppm).展开更多
A fully characterised natural rubber latex was subjected to mechanicaldegradation by stirring at intervals. The resistance to oxidative degradation of the differentsamples were studied by measuring the Plasticity rete...A fully characterised natural rubber latex was subjected to mechanicaldegradation by stirring at intervals. The resistance to oxidative degradation of the differentsamples were studied by measuring the Plasticity retention indices (PRI). The results show that there is an enhancement of the PRI from 57% for the undegradedrubber to 79% for the one-hour degraded sample. Further degradation resulted in decreaseof PRI as time of degradation increased. Therefore, the one-hour degraded sample is aspecial rubber with high oxidation resistance which is of great importance in engineering.展开更多
Iron-doped titania nanoparticles exhibit a higher photocatalytic activity than pure TiO2 for the degradation of nitrite. The optimum Fe-doped content in terms of activity is approximately 0. 5 %. The increase in photo...Iron-doped titania nanoparticles exhibit a higher photocatalytic activity than pure TiO2 for the degradation of nitrite. The optimum Fe-doped content in terms of activity is approximately 0. 5 %. The increase in photoactivity is probably due to the higher adsorption and the inhibition of electron-hole recombination. The photocatalytic oxidation reaction of nitrite over the Fe-doped TiO2 catalyst follows zero-order kinetics, which is different from that over pure TiO2. The reaction rate decreases linearly with the increase of the pH of the solution.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
Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene (HIPS) with triphenyl phosphate (TPP) and novolac type epoxy resin (NE) were characterized using thermo-...Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene (HIPS) with triphenyl phosphate (TPP) and novolac type epoxy resin (NE) were characterized using thermo-gravimetric experiment. And the flammability was determined by limited oxygen indices (LOI). The LOI results show that TPP and NE had a good synthetic effect on the flame retardancy of HIPS. Compared with pure HIPS,the LOI values of HIPS/NE and HIPS/TPP only increased by about 5%,and the LOI value of HIPS/TPP/NE reached 42.3%,nearly 23% above that of HIPS. All materials showed one main decomposition step,as radical HIPS scission predominated during anaerobic decomposition. TPP increased the activity energy effectively while NE affected the thermal-oxidative degradation more with the help of the char formation. With both TPP and NE,the materials could have a comparable good result of both thermal and thermal-oxidative degradation,which could contribute to their effect on the flame retardancy.展开更多
A series of metal oxide catalysts for catalytic oxidative degradation of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) were prepared, and the supported CuO catalysts were studied particularly. The supported CuO cata...A series of metal oxide catalysts for catalytic oxidative degradation of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) were prepared, and the supported CuO catalysts were studied particularly. The supported CuO catalysts were characterized by XRD and NH3-TPD techniques, in which CuO/γ-Al2O3 exhibited high degradation activity. The addition of Na2O or K2O into CuO/γ-Al2O3 improved the oxidative degradation of CPs remarkably, in which Na2O was more efficient than K2O. Over CuO/γ-Al2O3-Na2O, CPs were completely converted and the liberation of the inorganic chloride from 2-CP or 4-CP reached 97% or 100% respectively at 30 ?C for 2 h. The supported CuO catalysts with good dispersion of CuO particles and less acid sites were favorable for the efficient oxidative degradation of CPs. In addition, the initial pH of the reaction solution was found to be an important factor which influenced the catalytic oxidative degradation of CPs and the initial pH of 11.2 and 9.8 was preferred for the oxidative degradation of 2-CP and 4-CP respectively over CuO/γ-Al2O3 catalyst.展开更多
Contact glow discharge electrolysis (CGDE) of o-chlorophenol (2-CP) was investi-gated under different pH, voltages and initial concentrations. And the mechanism of the oxidationwas explored. The results suggested that...Contact glow discharge electrolysis (CGDE) of o-chlorophenol (2-CP) was investi-gated under different pH, voltages and initial concentrations. And the mechanism of the oxidationwas explored. The results suggested that the degradation followed the first order kinetic law;Fe2+ had a remarkable catalytic effect on the removal rate of o-chloropenol. In the presence ofFe2+, 2-CP underwent an exhaustive degradation, from which the major intermediates includedo-dihydroxybenze, p-hydroxybenze, p-benzoquione and carboxlic acids.展开更多
The scope of this study was to determine techniques to remediate trichloroethylene contamination under different environmental conditions, media and in co-existence with chromium. The specific objectives were focused ...The scope of this study was to determine techniques to remediate trichloroethylene contamination under different environmental conditions, media and in co-existence with chromium. The specific objectives were focused on the oxidation of trichloroethylene (TCE) in soil and aqueous media using both unmodified KMnO4 particles and poly (methyl methacrylate), PMMA encapsulated KMnO4 in the presence and absence of hexavalent chromium, Cr(VI). Molar ratios (p-values) of KMnO4 to TCE were used as a determining factor in the TCE oxidation process. p-values of 2, 5 and 10 were investigated in aqueous media and an approximately 0.5 M-1·s-1 rate constant was obtained using unmodified KMnO4 in aqueous system. The extent of oxidation did not change with TCE concentration. In soil system, TCE oxidation requires a large amount of KMnO4 to produce similar results as in aqueous system. pH experiments indicate that except at high alkaline condition, pH does not impact the extent of TCE oxidation. Also, the presence of Cr(VI) did not hinder TCE oxidation by KMnO4. Using controlled release application, the rate of TCE oxidation was reduced by PMMA encapsulated KMnO4. Comparative study indicated an expectedly slow rate of TCE degradation using modified KMnO4 but similar overall extent of oxidation for both modified and unmodified KMnO4. The application of the encapsulated matrix yielded 88% ± 3% TCE oxidation and a simultaneous 81% ± 2.1% Cr(VI) reduction by ferrous ion in the same system.展开更多
Deep frying with repeated use of same edible oil leads to the formation of lipid oxidation products. The presence of these oxidized products formed during frying at elevated temperature is hazardous for human health a...Deep frying with repeated use of same edible oil leads to the formation of lipid oxidation products. The presence of these oxidized products formed during frying at elevated temperature is hazardous for human health and therefore, requires prompt analysis for ensuring its fitness/quality. In this study, oxidative degradation of thermally stressed edible oils canola, sunflower and palm olein shortening was studied at 180°C ± 5°C up to 48 hours. Palm olein shortening remained stable during this period as the increase in its acid value was significantly less than canola and sunflower seed oils. The shortening samples were further studied by attenuated total reflectance Fourier transformation infrared (ATR-FTIR) and gas chromatography mass spectrometry (GC-MS) to evaluate the formation of various oxidation products due to thermal stress. ATR-FTIR indicates the formation of free fatty acids (FFAs), aldehyde groups and change in degree of unsaturation while GC-MS gives important information about profile of FFAs. The combination of these analytical techniques is useful for rapid and highly sensitive analysis of oxidized edible oil thus, ensuring its quality and fitness for safe use.展开更多
Spent auricularia auricular substrate(SAAS)was oxidatively degraded with aqueous hydrogen peroxide(AHPO)/acetic anhydride(AAH)to produce carboxylic acids(CAs)under mild conditions.The results show that up to 53.6%of t...Spent auricularia auricular substrate(SAAS)was oxidatively degraded with aqueous hydrogen peroxide(AHPO)/acetic anhydride(AAH)to produce carboxylic acids(CAs)under mild conditions.The results show that up to 53.6%of the organic matter in SAAS was converted to the soluble species(SSs).In total 122 CAs were detected in the SSs by the analysis with a gas chromatograph/mass spectrometer,which can be classified into 29 group components,mainly being aliphatic acids and along with small amount of aromatic acids.Among the aliphatic acids,normal alkanedioic acids are the most abundant.The detected aromatic acids include benzoic acids,phthalic acids,trimellitic acids,pyromellitic acids,and their derivatives.The synergistic oxidation and the released·OH,CH3COO·,and HOO·induced by AHPO/AAH play crucial roles in oxidatively degrading SAAS.展开更多
Results of triplet-triplet energy transfer from biacetyl to OPVs and OPV triplet state quenching by 1, 4-diazabicvclo[2.2.2] octane (DABCO) sueeested that trinlet stata of oligophenylenevinylenes(OPVs) direct...Results of triplet-triplet energy transfer from biacetyl to OPVs and OPV triplet state quenching by 1, 4-diazabicvclo[2.2.2] octane (DABCO) sueeested that trinlet stata of oligophenylenevinylenes(OPVs) directly takes part in their photooxidafive degradation instead of just generating singlet oxygen.展开更多
Choibá (Dipteryx oleifera Benth.) is a promising source of edible oil with high nutritional quality and a significant content of oleic acid (52% - 54%). To promote Choibá as source of edible oil is necessary...Choibá (Dipteryx oleifera Benth.) is a promising source of edible oil with high nutritional quality and a significant content of oleic acid (52% - 54%). To promote Choibá as source of edible oil is necessary to ensure its stability along the time of production, distribution and storage. Loss of nutritional and organoleptic quality in lipids is mainly due to lipid peroxidation reactions. The aim of this research was to evaluate the oxidative stability of Choibá oil at 100°C ± 1°C with aeration (1150 mL air/min) supplemented with rosemary extract (Rosmarinus officinalis L.), at 1000 mg/L (RE1000) and 1500 mg/L (RE1500), and with BHT (200 mg/L) and from this results to evaluate the degradation kinetics and shelf-life of Choibá oil at 35°C, 45°C and 55°C without addition of antioxidants (Control) and with addition of best concentration of rosemary extract obtained from previous study. Progress in oil oxidation was measured through the extent of oxidation products: peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Results revealed that the addition of rosemary extract at 1500 mg/L significantly reduced de formation of hydroperoxides (PV), more than BHT. Through correlations between concentrations of antioxidant (including control without antioxidant) with peroxide values, the kinetics of degradation and shelf-life of Choibá oil with predictive models are evaluated in real time and accelerated (35°C, 45°C and 55°C) using the Arrhenius equation. In addition, the oxidation reactions of this oil follow a first order kinetic model for PV and zero order kinetic model for TBARS. The rate of formation of PV was dependent on the storage temperature, according to the Arrhenius equation with the activation energy of 4611.5071 J/mol for Control and 7409.5771 J/mol for RE1500 treatment. The result of TBARS didn’t adjust to Arrhenius model, thus measurement of malondialdehyde (MDA) wasn’t a useful parameter for shelf-life determination of Choibá oil.展开更多
A novel hierarchical bowl-like FeCuS@Cu_(2)S@Fe^(0)nanohybrid catalyst(B-FeCuS@Cu_(2)S@Fe^(0))was synthesized for removing sulfamethoxazole(SMX) through catalytic activation of peroxymonosulfate(PMS). It was found tha...A novel hierarchical bowl-like FeCuS@Cu_(2)S@Fe^(0)nanohybrid catalyst(B-FeCuS@Cu_(2)S@Fe^(0))was synthesized for removing sulfamethoxazole(SMX) through catalytic activation of peroxymonosulfate(PMS). It was found that this catalyst exhibited excellently high catalytic activity. Under optimized reaction conditions, all the added SMX(12 mg/L) could be completely degraded within 5 min. The SMX degradation followed pseudo first order kinetics with a rate constant k of 0.89 min^(-1), being 1.38, 4.51, 8.99 and 35.6 times greater than that of other catalysts including Fe^(0)(0.644 min^(-1)in the very initial stage), bowl-like iron-doped CuS(B-FeCuS, 0.197 min^(-1)), bowl-like CuS(B-CuS, 0.099 min^(-1)) and Cu_(2)O(0.025 min^(-1)), respectively. During the degradation, several reactive oxygen species(·OH, SO_(4)·-and1O_(2)) were generated with ·OH as the main one as confirmed by electron paramagnetic resonance analysis. The SMX degradation in the present system included both radical and non-radical mediated processes. A possible mechanistic insight of the PMS activation by bowl Fe^(0)decorated CuS@Cu_(2)S-based catalyst was proposed according to X-ray photoelectron spectroscopic(XPS) analysis, and the degradation pathway of SMX was speculated by monitoring the degradation intermediates with liquid chromatography coupled with mass spectrometry(LC-MS).展开更多
For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion b...For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion beam-scanning electron microscopy was em-ployed to characterize and reconstruct the ceramic microstructures of SOFC anodes.The lattice Boltzmann method(LBM)simulation of multiphysical and electrochemical processes in the reconstructed models was performed.Two samples collected from industrial-size cells were characterized,including a reduced reference cell and a cell with an initial aging process.Statistical parameters of the reconstructed microstructures revealed a significant decrease in the active triple-phase boundary and Ni connectivity in the aged cell compared with the reference cell.The LBM simulation revealed that activity degradation is dominant compared with microstructural degradation during the initial aging process,and the electrochemical reactions spread to the support layer in the aged cell.The microstructural and activity de-gradations are attributed to Ni migration and coarsening.展开更多
Vegetable oils are a source of energy, essential fatty acids, antioxidants and fat-soluble vitamins useful for human health care and development. These oils also contribute to organoleptic quality of their products’ ...Vegetable oils are a source of energy, essential fatty acids, antioxidants and fat-soluble vitamins useful for human health care and development. These oils also contribute to organoleptic quality of their products’ derivatives. However, their chemical and physical properties can be modified by the mode of their extraction, storage and distribution. These modifications might negatively affect the nutritional quality of the oils. The goals of this study were to: sample different vegetable oils for cosmetic or dietary use marketed in Cameroon, and verify purity and oxidation states of each kind of oil through determination of its acidity, iodine, peroxide, saponification, refractive indexes and the conformity of the labeling. The carotene content, the level of polar components and specific absorbance were also determined. As the result, six oils namely palm, palm kernel, coconut, black cumin, peanut and shea butter were collected. Apart from labeling, chemicals and physicals parameters analyzed were generally in accordance with the Cameroonian and Codex Alimentarius standard. This study suggests that vegetable oils sampled in the Cameroonian market may not expose consumers to lipid oxidation products generating pathological oxidative stress and inflammation. However, efforts in application of existing standard need to be done as far as labeling are concerned.展开更多
This paper is intended to explore soil organic matter and carbon isotope fractionation at three locations of the Passaic River to determine if microbial degradation of organic contaminants in soil is correlated to the...This paper is intended to explore soil organic matter and carbon isotope fractionation at three locations of the Passaic River to determine if microbial degradation of organic contaminants in soil is correlated to the surrounding physical environment. Microbial degradation of organic contaminants is important for the detoxification of toxic substances thereby minimizing stagnation in the environment and accumulating in the food chain. Since organic contaminants are not easily dissolved in water, they will penetrate sediment and end up enriching the adjacent soil. The hypothesis that we are testing is microbial activity and carbon isotope fractionation will be greater in preserved soils than urban soils. The reason why this is expected to be the case is the expectation of higher microbial activity in preserved environments due to less exposure to pollutants, better soil structure, higher organic matter content, and more favorable conditions for microbial growth. This is contrasted with urban soils, which are impacted by pollutants and disturbances, potentially inhibiting microbial activity. We wish to collect soil samples adjacent to the Passaic River at a pristine location, Great Swamp Wildlife Refuge, a suburban location, Goffle Brook Park, Hawthorne NJ, and an urban location, Paterson NJ. These soil samples will be weighed for soil organic matter (SOM) and weighed for isotope ratio mass spectrometry (IRMS) to test organic carbon isotopes. High SOM and δ13C depletion activity indicate microbial growth based on the characteristics of the soil horizon rather than the location of the soil sample which results in degradation of organic compounds.展开更多
文摘The efficacy of roasted sesame oil(SO)on the oxidation deterioration of sunflower oil(SFO)during heating was investigated.The concentrations of SO in the SFO were 0,10%,20%,and 30%by volume.The oxidation profile of oil samples was monitored by evaluating the generation of oxidation products and chemical alterations in the oils'composition during heating at frying temperature(180℃).The results showed that the oxidation parameters(free fatty acid,peroxide value,p-anisidine value,total oxidation status,thiobarbituric acid value,and color index)increased significantly in SFO compared to blends or SO during thermal treatment.During heating,the concentration of polyunsaturated fatty acids(PUFA)was reduced with increased level of saturated fatty acids;these results were observed more in SFO than those of SO or blend oils.However,the presence of SO in SFO reduced the decomposition of PUFA.In Fourier-transform infrared spectroscopy,the peak intensities were significantly altered in SFO compared to the blend oils during heating.Based on the most analytical data,it may be agreed that the heating at frying temperature led to the generation of relatively higher contents of oxidative products in SFO compared to blend oils,showing a lower degree of oxidation occurred in blends.The best frying performance for the SFO was achieved by using 30%SO extracted from the roasted sesame seed.This study showed the proper blending of high polyunsaturated oil with SO can produce oil blends with high nutritional values and enhanced stability for daily cooking and deep-frying applications.
基金Funded by the National Natural Science Foundation of China(52075391)the China Postdoctoral Science Foundation(2019M660596)。
文摘In order to evaluate the thermal oxidation degradation behavior of lubricant with different antioxidants,the thermal kinetics equation based on the anlyses of thermogravimetry(TG),differential thermal analysis(DTA),and differential scanning calorimetry(DSC)was established,respectively,to calculate the activation energy of lubricant thermal-oxidative reaction.The thermal analyses of TG and DTA were employed to determine the thermal decomposition properties of ester oils trimethylolpropane trioleate(TMPTO)with butyl-octyl-diphenylamine/octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate/amine-phenol combination antioxidant.The activation energy of the lubricating oil adding antioxidant is increased relative to the TMPTO base oil,and the order of activation energy are Ec(93.732 kJ·mol^(-1))>Ed(88.71 kJ·mol^(-1))>Eb(58.41 kJ·mol^(-1))>Ea(46.32 kJ·mol^(-1)).The experimental results show that octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate in TMPTO has favorable resistance to thermal oxidation and decomposition.The thermal analysis method of DSC accurately reflects the heat exchange of lubricant thermal-oxidative reaction.The order of activation energy is calculated to ED(144.385 kJ·mol^(-1))>EC(110.05 kJ·mol^(-1))>EB(97.187 kJ·mol^(-1))>EA(66.02 kJ·mol^(-1)).It is illustrated that the amine-phenol combination antioxidant has the best thermal oxidation resistance,which is the same as what the oxidation onset temperature effected.
文摘Degradation of dyes is an important environmental issue. In order to avoid the carcinogenic risks in anaerobic-aerobic biological process for wastewater containing azo dyes, a hemin based biomimetic oxidative degradation of azo dyes was developed. Acid orange 7 (AO7) was selected as the model for azo dye and the high efficient degradation was achieved in hemin/H2O2 system at pH 11.0. Degradation could be described by a pseudo-first-order kinetic model. The order of dependence on H2O2 concentration was significantly larger than that of hemin. Coexisting anions sulphate and chloride had little effect on the degradation, but reductive sulphite dramatically inhibited the degradation. The protic solvent 2-prophanol obviously promoted the degradation. Azo chromogenic group was destroyed quickly and some smaller intermediates formed. Active species oxoferryl porphyrin p-cation radical +PFeIV=O generated from heterolytic cleavage of O-O in H2O2 catalyzed by hemin play the main roles in degradation and reaction pathways were proposed.
基金the Alexander von Humboldt Foundation of Germany, and partly by the CAS and the NNSF of China.
文摘trichlorophenol (TCP) was firstly treated with air ions generated by electric discharge, and high dechlorination (53%) was observed after 60 min treatment, indicating that air ions are an efficient dechlorination means and might have a future in the oxidative removal of chlorinated phenols. In addition, a stepwise degradation of TCP, beginning with the formation of a major product 2,6-dichloro-1,4-benzenediol via substitution, is proposed through a detailed analysis of gas chromatography/mass spectrometry.
文摘The study focused on the application of high-resolution mass spectrometry for the identification of impurities in pharmaceutical small molecules. A high-performance liquid chromatography (HPLC) coupled high resolution mass spectrometer (HRMS) was used for identification of oxidative degradation impurities (DIs) of lansoprazole. The utilization of HRMS facilitates to determine the accurate mass of impurities and their fragment/product ions. A fast mass spectrometer (MS) compatible reverse phase chromatography method was used to investigate the oxidative stressed impurities. HPLC column;C18 (50 × 4.6 mm, 3.5 μm) was used with gradient elution. Spectral data acquired using information dependent acquisition (IDA) with real time dynamic background subtraction algorithm (DBS). Three oxidative impurities: DI-I (m/z 386.0781), DI-II (m/z 402.0734) and DI-III (m/z 386.0785), was observed during this study;interpretation of high resolution spectral data of all three impurities was carried out;elemental composition and molecular structure was proposed for major fragments. In this study mass error was found ≤7.7 parts per million (ppm).
文摘A fully characterised natural rubber latex was subjected to mechanicaldegradation by stirring at intervals. The resistance to oxidative degradation of the differentsamples were studied by measuring the Plasticity retention indices (PRI). The results show that there is an enhancement of the PRI from 57% for the undegradedrubber to 79% for the one-hour degraded sample. Further degradation resulted in decreaseof PRI as time of degradation increased. Therefore, the one-hour degraded sample is aspecial rubber with high oxidation resistance which is of great importance in engineering.
基金the National Natural Science Foundation of China.
文摘Iron-doped titania nanoparticles exhibit a higher photocatalytic activity than pure TiO2 for the degradation of nitrite. The optimum Fe-doped content in terms of activity is approximately 0. 5 %. The increase in photoactivity is probably due to the higher adsorption and the inhibition of electron-hole recombination. The photocatalytic oxidation reaction of nitrite over the Fe-doped TiO2 catalyst follows zero-order kinetics, which is different from that over pure TiO2. The reaction rate decreases linearly with the increase of the pH of the solution.
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.
基金Guangdong Province Natural Sciences Fundation(No.39672)
文摘Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene (HIPS) with triphenyl phosphate (TPP) and novolac type epoxy resin (NE) were characterized using thermo-gravimetric experiment. And the flammability was determined by limited oxygen indices (LOI). The LOI results show that TPP and NE had a good synthetic effect on the flame retardancy of HIPS. Compared with pure HIPS,the LOI values of HIPS/NE and HIPS/TPP only increased by about 5%,and the LOI value of HIPS/TPP/NE reached 42.3%,nearly 23% above that of HIPS. All materials showed one main decomposition step,as radical HIPS scission predominated during anaerobic decomposition. TPP increased the activity energy effectively while NE affected the thermal-oxidative degradation more with the help of the char formation. With both TPP and NE,the materials could have a comparable good result of both thermal and thermal-oxidative degradation,which could contribute to their effect on the flame retardancy.
基金financially supported by the Education Department of Liaoning Province(No.2009A421)
文摘A series of metal oxide catalysts for catalytic oxidative degradation of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) were prepared, and the supported CuO catalysts were studied particularly. The supported CuO catalysts were characterized by XRD and NH3-TPD techniques, in which CuO/γ-Al2O3 exhibited high degradation activity. The addition of Na2O or K2O into CuO/γ-Al2O3 improved the oxidative degradation of CPs remarkably, in which Na2O was more efficient than K2O. Over CuO/γ-Al2O3-Na2O, CPs were completely converted and the liberation of the inorganic chloride from 2-CP or 4-CP reached 97% or 100% respectively at 30 ?C for 2 h. The supported CuO catalysts with good dispersion of CuO particles and less acid sites were favorable for the efficient oxidative degradation of CPs. In addition, the initial pH of the reaction solution was found to be an important factor which influenced the catalytic oxidative degradation of CPs and the initial pH of 11.2 and 9.8 was preferred for the oxidative degradation of 2-CP and 4-CP respectively over CuO/γ-Al2O3 catalyst.
基金The project supported by the Key Project of Science and Technology from the Ministry of Education China (No. 00250) the project of KJCXGC-01 of Northwest Normal University, China
文摘Contact glow discharge electrolysis (CGDE) of o-chlorophenol (2-CP) was investi-gated under different pH, voltages and initial concentrations. And the mechanism of the oxidationwas explored. The results suggested that the degradation followed the first order kinetic law;Fe2+ had a remarkable catalytic effect on the removal rate of o-chloropenol. In the presence ofFe2+, 2-CP underwent an exhaustive degradation, from which the major intermediates includedo-dihydroxybenze, p-hydroxybenze, p-benzoquione and carboxlic acids.
文摘The scope of this study was to determine techniques to remediate trichloroethylene contamination under different environmental conditions, media and in co-existence with chromium. The specific objectives were focused on the oxidation of trichloroethylene (TCE) in soil and aqueous media using both unmodified KMnO4 particles and poly (methyl methacrylate), PMMA encapsulated KMnO4 in the presence and absence of hexavalent chromium, Cr(VI). Molar ratios (p-values) of KMnO4 to TCE were used as a determining factor in the TCE oxidation process. p-values of 2, 5 and 10 were investigated in aqueous media and an approximately 0.5 M-1·s-1 rate constant was obtained using unmodified KMnO4 in aqueous system. The extent of oxidation did not change with TCE concentration. In soil system, TCE oxidation requires a large amount of KMnO4 to produce similar results as in aqueous system. pH experiments indicate that except at high alkaline condition, pH does not impact the extent of TCE oxidation. Also, the presence of Cr(VI) did not hinder TCE oxidation by KMnO4. Using controlled release application, the rate of TCE oxidation was reduced by PMMA encapsulated KMnO4. Comparative study indicated an expectedly slow rate of TCE degradation using modified KMnO4 but similar overall extent of oxidation for both modified and unmodified KMnO4. The application of the encapsulated matrix yielded 88% ± 3% TCE oxidation and a simultaneous 81% ± 2.1% Cr(VI) reduction by ferrous ion in the same system.
文摘Deep frying with repeated use of same edible oil leads to the formation of lipid oxidation products. The presence of these oxidized products formed during frying at elevated temperature is hazardous for human health and therefore, requires prompt analysis for ensuring its fitness/quality. In this study, oxidative degradation of thermally stressed edible oils canola, sunflower and palm olein shortening was studied at 180°C ± 5°C up to 48 hours. Palm olein shortening remained stable during this period as the increase in its acid value was significantly less than canola and sunflower seed oils. The shortening samples were further studied by attenuated total reflectance Fourier transformation infrared (ATR-FTIR) and gas chromatography mass spectrometry (GC-MS) to evaluate the formation of various oxidation products due to thermal stress. ATR-FTIR indicates the formation of free fatty acids (FFAs), aldehyde groups and change in degree of unsaturation while GC-MS gives important information about profile of FFAs. The combination of these analytical techniques is useful for rapid and highly sensitive analysis of oxidized edible oil thus, ensuring its quality and fitness for safe use.
基金supported by the Seed Fund from Jilin Agricultural Science and Technology University([2016]No.Z02)Undergraduate Scientific and Technical innovation of Jilin Province(Grant[2016]No.030).
文摘Spent auricularia auricular substrate(SAAS)was oxidatively degraded with aqueous hydrogen peroxide(AHPO)/acetic anhydride(AAH)to produce carboxylic acids(CAs)under mild conditions.The results show that up to 53.6%of the organic matter in SAAS was converted to the soluble species(SSs).In total 122 CAs were detected in the SSs by the analysis with a gas chromatograph/mass spectrometer,which can be classified into 29 group components,mainly being aliphatic acids and along with small amount of aromatic acids.Among the aliphatic acids,normal alkanedioic acids are the most abundant.The detected aromatic acids include benzoic acids,phthalic acids,trimellitic acids,pyromellitic acids,and their derivatives.The synergistic oxidation and the released·OH,CH3COO·,and HOO·induced by AHPO/AAH play crucial roles in oxidatively degrading SAAS.
文摘Results of triplet-triplet energy transfer from biacetyl to OPVs and OPV triplet state quenching by 1, 4-diazabicvclo[2.2.2] octane (DABCO) sueeested that trinlet stata of oligophenylenevinylenes(OPVs) directly takes part in their photooxidafive degradation instead of just generating singlet oxygen.
基金the support of DIME project 18870Colciencias project 338756236225.
文摘Choibá (Dipteryx oleifera Benth.) is a promising source of edible oil with high nutritional quality and a significant content of oleic acid (52% - 54%). To promote Choibá as source of edible oil is necessary to ensure its stability along the time of production, distribution and storage. Loss of nutritional and organoleptic quality in lipids is mainly due to lipid peroxidation reactions. The aim of this research was to evaluate the oxidative stability of Choibá oil at 100°C ± 1°C with aeration (1150 mL air/min) supplemented with rosemary extract (Rosmarinus officinalis L.), at 1000 mg/L (RE1000) and 1500 mg/L (RE1500), and with BHT (200 mg/L) and from this results to evaluate the degradation kinetics and shelf-life of Choibá oil at 35°C, 45°C and 55°C without addition of antioxidants (Control) and with addition of best concentration of rosemary extract obtained from previous study. Progress in oil oxidation was measured through the extent of oxidation products: peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Results revealed that the addition of rosemary extract at 1500 mg/L significantly reduced de formation of hydroperoxides (PV), more than BHT. Through correlations between concentrations of antioxidant (including control without antioxidant) with peroxide values, the kinetics of degradation and shelf-life of Choibá oil with predictive models are evaluated in real time and accelerated (35°C, 45°C and 55°C) using the Arrhenius equation. In addition, the oxidation reactions of this oil follow a first order kinetic model for PV and zero order kinetic model for TBARS. The rate of formation of PV was dependent on the storage temperature, according to the Arrhenius equation with the activation energy of 4611.5071 J/mol for Control and 7409.5771 J/mol for RE1500 treatment. The result of TBARS didn’t adjust to Arrhenius model, thus measurement of malondialdehyde (MDA) wasn’t a useful parameter for shelf-life determination of Choibá oil.
基金the funding supports from the National Natural Science Foundation of China (Nos. 22076052 and 21976063)China Postdoctoral Science Foundation (No. 2018M642850)。
文摘A novel hierarchical bowl-like FeCuS@Cu_(2)S@Fe^(0)nanohybrid catalyst(B-FeCuS@Cu_(2)S@Fe^(0))was synthesized for removing sulfamethoxazole(SMX) through catalytic activation of peroxymonosulfate(PMS). It was found that this catalyst exhibited excellently high catalytic activity. Under optimized reaction conditions, all the added SMX(12 mg/L) could be completely degraded within 5 min. The SMX degradation followed pseudo first order kinetics with a rate constant k of 0.89 min^(-1), being 1.38, 4.51, 8.99 and 35.6 times greater than that of other catalysts including Fe^(0)(0.644 min^(-1)in the very initial stage), bowl-like iron-doped CuS(B-FeCuS, 0.197 min^(-1)), bowl-like CuS(B-CuS, 0.099 min^(-1)) and Cu_(2)O(0.025 min^(-1)), respectively. During the degradation, several reactive oxygen species(·OH, SO_(4)·-and1O_(2)) were generated with ·OH as the main one as confirmed by electron paramagnetic resonance analysis. The SMX degradation in the present system included both radical and non-radical mediated processes. A possible mechanistic insight of the PMS activation by bowl Fe^(0)decorated CuS@Cu_(2)S-based catalyst was proposed according to X-ray photoelectron spectroscopic(XPS) analysis, and the degradation pathway of SMX was speculated by monitoring the degradation intermediates with liquid chromatography coupled with mass spectrometry(LC-MS).
基金the National Key R&D Program of China(No.2018YFB1502201)the Guangdong Basic and Applied Basic Research Foundation,China(No.2020A1515010551).
文摘For present solid oxide fuel cells(SOFCs),rapid performance degradation is observed in the initial aging process,and the dis-cussion of the degradation mechanism necessitates quantitative analysis.Herein,focused ion beam-scanning electron microscopy was em-ployed to characterize and reconstruct the ceramic microstructures of SOFC anodes.The lattice Boltzmann method(LBM)simulation of multiphysical and electrochemical processes in the reconstructed models was performed.Two samples collected from industrial-size cells were characterized,including a reduced reference cell and a cell with an initial aging process.Statistical parameters of the reconstructed microstructures revealed a significant decrease in the active triple-phase boundary and Ni connectivity in the aged cell compared with the reference cell.The LBM simulation revealed that activity degradation is dominant compared with microstructural degradation during the initial aging process,and the electrochemical reactions spread to the support layer in the aged cell.The microstructural and activity de-gradations are attributed to Ni migration and coarsening.
文摘Vegetable oils are a source of energy, essential fatty acids, antioxidants and fat-soluble vitamins useful for human health care and development. These oils also contribute to organoleptic quality of their products’ derivatives. However, their chemical and physical properties can be modified by the mode of their extraction, storage and distribution. These modifications might negatively affect the nutritional quality of the oils. The goals of this study were to: sample different vegetable oils for cosmetic or dietary use marketed in Cameroon, and verify purity and oxidation states of each kind of oil through determination of its acidity, iodine, peroxide, saponification, refractive indexes and the conformity of the labeling. The carotene content, the level of polar components and specific absorbance were also determined. As the result, six oils namely palm, palm kernel, coconut, black cumin, peanut and shea butter were collected. Apart from labeling, chemicals and physicals parameters analyzed were generally in accordance with the Cameroonian and Codex Alimentarius standard. This study suggests that vegetable oils sampled in the Cameroonian market may not expose consumers to lipid oxidation products generating pathological oxidative stress and inflammation. However, efforts in application of existing standard need to be done as far as labeling are concerned.
文摘This paper is intended to explore soil organic matter and carbon isotope fractionation at three locations of the Passaic River to determine if microbial degradation of organic contaminants in soil is correlated to the surrounding physical environment. Microbial degradation of organic contaminants is important for the detoxification of toxic substances thereby minimizing stagnation in the environment and accumulating in the food chain. Since organic contaminants are not easily dissolved in water, they will penetrate sediment and end up enriching the adjacent soil. The hypothesis that we are testing is microbial activity and carbon isotope fractionation will be greater in preserved soils than urban soils. The reason why this is expected to be the case is the expectation of higher microbial activity in preserved environments due to less exposure to pollutants, better soil structure, higher organic matter content, and more favorable conditions for microbial growth. This is contrasted with urban soils, which are impacted by pollutants and disturbances, potentially inhibiting microbial activity. We wish to collect soil samples adjacent to the Passaic River at a pristine location, Great Swamp Wildlife Refuge, a suburban location, Goffle Brook Park, Hawthorne NJ, and an urban location, Paterson NJ. These soil samples will be weighed for soil organic matter (SOM) and weighed for isotope ratio mass spectrometry (IRMS) to test organic carbon isotopes. High SOM and δ13C depletion activity indicate microbial growth based on the characteristics of the soil horizon rather than the location of the soil sample which results in degradation of organic compounds.
