Abiotic degradability of four phthalic acid esters （PAEs） in the aquatic phase was evaluated over a wide pH range 5-9. The PAE solutions in glass test tubes were placed either in the dark and under the natural sunli...Abiotic degradability of four phthalic acid esters （PAEs） in the aquatic phase was evaluated over a wide pH range 5-9. The PAE solutions in glass test tubes were placed either in the dark and under the natural sunlight irradiation for evaluating the degradation rate via hydrolysis or photolysis plus hydrolysis, respectively, at ambient temperature for 140 d from autumn to winter in Osaka, Japan. The efficiency of abiotic degradation of the PAEs with relatively short alkyl chains, such as butylbenzyl phthalate （BBP） and di-nbutyl phthalate （DBP）, at neutral pH was significantly lower than that in the acidic or alkaline condition. Photolysis was considered to contribute mainly to the total abiotic degradation at all pH. Neither hydrolysis nor photolysis of di-ethylhexyl phthalate （DEHP） proceeded significantly at any pH, especially hydrolysis at neutral pH was negligible. On the other hand, the degradation rate of di- isononyl phthalate （DINP） catalyzed mainly by photolysis was much higher than those of the other PAEs, and was almost completely removed during the experimental period at pH 5 and 9. As a whole, according to the half-life （t1/2） obtained in the experiments, the abiotic degradability of the PAEs was in the sequence： DINP （32-140 d） 〉 DBP （50-360 d）, BBP （58-480 d） 〉 DEHP （390-1600 d） under sunlight irradiation （via photolysis plus hydrolysis）. Although the abiotic degradation rates for BBP, DBP, and DEHP are much lower than the biodegradation rates reported, the photolysis rate for DINP is comparable to its biodegradation rate in the acidic or alkaline condition.展开更多
This study aims to disclose the thermo-oxidative degradation behaviors and kinetics of a carbon fiber reinforced polyimide(CFRPI)composite for modeling of the Iong-term degradation process.The degradation behaviors we...This study aims to disclose the thermo-oxidative degradation behaviors and kinetics of a carbon fiber reinforced polyimide(CFRPI)composite for modeling of the Iong-term degradation process.The degradation behaviors were revealed through off-gas products analysis,and the overall kinetic interpretation was achieved from study of the mass-loss curves recorded under dynamic conditions.It was found that thermooxidative degradati on of the CFRPI composite was a multistep process,which in eluded four main reaction steps.Since most kinetic an alysis methods were derived from simple reactions described by a single kinetic triplet,they cannot be applied reliably to such a process.Therefore,we firstly separated the four overlapped reaction steps by peak fitting of derivative thermogravimetric curves using Fraser-Suzuki equation consider!ng the asymmetrical n ature of kin etic curves,and subsequently an a lyzed each in dividual reaction employing Friedma n method and experimental master-plots method.Four sets of kinetic triplets were determined to characterize the entire degradation process.The validity of four corresponding kinetic triplets was confirmed by perfect simulation of mass-loss curves recorded at both dynamic conditions used in kinetic analysis and entirely different isothermal conditions.Finally,modeling of Iong-term aging at 400°C of the CFRPI composite was successfully achieved based on these kinetic triplets.The predicted mass loss and flexural property correlated well with experimental results.This study can serve as a basis for rapid evaluation of the long-term durability of the CFRPI composite in various application environments.展开更多
This investigation was carried out to establish a new domestic landfill gas(LFG)generation rate model that takes into account the impact of leachate recirculation.The first-order kinetics and two-stage reaction(FKTSR)...This investigation was carried out to establish a new domestic landfill gas(LFG)generation rate model that takes into account the impact of leachate recirculation.The first-order kinetics and two-stage reaction(FKTSR)model of the LFG generation rate includes mechanisms of the nutrient balance for biochemical reaction in two main stages.In this study,the FKTSR model was modified by the introduction of the outflow function and the organic acid conversion coefficient in order to represent the in-situ condition of nutrient loss through leachate.Laboratory experiments were carried out to simulate the impact of leachate recirculation and verify the modified FKTSR model.The model calibration was then calculated by using the experimental data.The results suggested that the new model was in line with the experimental data.The main parameters of the modified FKTSR model,including the LFG production potential(L0),the reaction rate constant in the first stage(K1),and the reaction rate constant in the second stage(K2)of 64.746 L,0.202 d^(–1),and 0.338 d^(–1),respectively,were comparable to the old ones of 42.069 L,0.231 d^(–1),and 0.231 d^(–1).The new model is better able to explain the mechanisms involved in LFG generation.展开更多
To well describe the Ti（IV）-catalyzed H2O2/O3 reaction in aqueous solution, a kinetic model was established based on its mechanism. This model was then validated by the experiments of acetic acid degradation in aque...To well describe the Ti（IV）-catalyzed H2O2/O3 reaction in aqueous solution, a kinetic model was established based on its mechanism. This model was then validated by the experiments of acetic acid degradation in aqueous solution. It was found that the correlation coefficient of fittings was higher than 0.970. Three key operating factors affecting organic degradation in the Ti（IV）-catalyzed H2O2/O3 process were studied, including Ti（IV） concentration, dissolved ozone concentration and initial H2O2 concentration. Furthermore, some experiments were conducted to determine the rate constant for dissolved ozone decomposition initiated by Ti2O52＋. The rate constant measured is almost in accord with the data analyzed by this kinetic model. The goodness of fittings demonstrated that this model could well describe the kinetics of the Ti（IV）-catalyzed H2O2/O3 reaction mathematically and chemically. Therefore, this kinetic model can provide some useful information to optimize the parameters in ozonation of water containing certain pollutants.展开更多
在假设里氏木霉ATCC56764产生的壳聚糖酶水解壳聚糖是以唯一内切方式随机进攻 b -1,4糖苷键的基础上,结合终产物非竞争性抑制的M-M动力学,建立了壳聚糖降解的数学模型,并用四阶Runge-Kutta方法结合Powell优化方法对模型中各个动力学参...在假设里氏木霉ATCC56764产生的壳聚糖酶水解壳聚糖是以唯一内切方式随机进攻 b -1,4糖苷键的基础上,结合终产物非竞争性抑制的M-M动力学,建立了壳聚糖降解的数学模型,并用四阶Runge-Kutta方法结合Powell优化方法对模型中各个动力学参数进行了优化。模型计算结果与实验数据的比较表明,建立的数学模型能够合理地描述和解释壳聚糖降解的动力学过程,有助于加深对壳聚糖酶法降解机理的认识,对生产特定聚合度的壳聚糖具有指导意义。展开更多
文摘Abiotic degradability of four phthalic acid esters （PAEs） in the aquatic phase was evaluated over a wide pH range 5-9. The PAE solutions in glass test tubes were placed either in the dark and under the natural sunlight irradiation for evaluating the degradation rate via hydrolysis or photolysis plus hydrolysis, respectively, at ambient temperature for 140 d from autumn to winter in Osaka, Japan. The efficiency of abiotic degradation of the PAEs with relatively short alkyl chains, such as butylbenzyl phthalate （BBP） and di-nbutyl phthalate （DBP）, at neutral pH was significantly lower than that in the acidic or alkaline condition. Photolysis was considered to contribute mainly to the total abiotic degradation at all pH. Neither hydrolysis nor photolysis of di-ethylhexyl phthalate （DEHP） proceeded significantly at any pH, especially hydrolysis at neutral pH was negligible. On the other hand, the degradation rate of di- isononyl phthalate （DINP） catalyzed mainly by photolysis was much higher than those of the other PAEs, and was almost completely removed during the experimental period at pH 5 and 9. As a whole, according to the half-life （t1/2） obtained in the experiments, the abiotic degradability of the PAEs was in the sequence： DINP （32-140 d） 〉 DBP （50-360 d）, BBP （58-480 d） 〉 DEHP （390-1600 d） under sunlight irradiation （via photolysis plus hydrolysis）. Although the abiotic degradation rates for BBP, DBP, and DEHP are much lower than the biodegradation rates reported, the photolysis rate for DINP is comparable to its biodegradation rate in the acidic or alkaline condition.
文摘This study aims to disclose the thermo-oxidative degradation behaviors and kinetics of a carbon fiber reinforced polyimide(CFRPI)composite for modeling of the Iong-term degradation process.The degradation behaviors were revealed through off-gas products analysis,and the overall kinetic interpretation was achieved from study of the mass-loss curves recorded under dynamic conditions.It was found that thermooxidative degradati on of the CFRPI composite was a multistep process,which in eluded four main reaction steps.Since most kinetic an alysis methods were derived from simple reactions described by a single kinetic triplet,they cannot be applied reliably to such a process.Therefore,we firstly separated the four overlapped reaction steps by peak fitting of derivative thermogravimetric curves using Fraser-Suzuki equation consider!ng the asymmetrical n ature of kin etic curves,and subsequently an a lyzed each in dividual reaction employing Friedma n method and experimental master-plots method.Four sets of kinetic triplets were determined to characterize the entire degradation process.The validity of four corresponding kinetic triplets was confirmed by perfect simulation of mass-loss curves recorded at both dynamic conditions used in kinetic analysis and entirely different isothermal conditions.Finally,modeling of Iong-term aging at 400°C of the CFRPI composite was successfully achieved based on these kinetic triplets.The predicted mass loss and flexural property correlated well with experimental results.This study can serve as a basis for rapid evaluation of the long-term durability of the CFRPI composite in various application environments.
基金the Specialized Research Fund for the Doctoral Program of Higher Education(No.20050027002)。
文摘This investigation was carried out to establish a new domestic landfill gas(LFG)generation rate model that takes into account the impact of leachate recirculation.The first-order kinetics and two-stage reaction(FKTSR)model of the LFG generation rate includes mechanisms of the nutrient balance for biochemical reaction in two main stages.In this study,the FKTSR model was modified by the introduction of the outflow function and the organic acid conversion coefficient in order to represent the in-situ condition of nutrient loss through leachate.Laboratory experiments were carried out to simulate the impact of leachate recirculation and verify the modified FKTSR model.The model calibration was then calculated by using the experimental data.The results suggested that the new model was in line with the experimental data.The main parameters of the modified FKTSR model,including the LFG production potential(L0),the reaction rate constant in the first stage(K1),and the reaction rate constant in the second stage(K2)of 64.746 L,0.202 d^(–1),and 0.338 d^(–1),respectively,were comparable to the old ones of 42.069 L,0.231 d^(–1),and 0.231 d^(–1).The new model is better able to explain the mechanisms involved in LFG generation.
基金supported by the National Natural Science Foundation of China (No. 50578146, 20876151,21176225)the Natural Science Foundation of Zhejiang Province, China (No. Y5080178)
文摘To well describe the Ti（IV）-catalyzed H2O2/O3 reaction in aqueous solution, a kinetic model was established based on its mechanism. This model was then validated by the experiments of acetic acid degradation in aqueous solution. It was found that the correlation coefficient of fittings was higher than 0.970. Three key operating factors affecting organic degradation in the Ti（IV）-catalyzed H2O2/O3 process were studied, including Ti（IV） concentration, dissolved ozone concentration and initial H2O2 concentration. Furthermore, some experiments were conducted to determine the rate constant for dissolved ozone decomposition initiated by Ti2O52＋. The rate constant measured is almost in accord with the data analyzed by this kinetic model. The goodness of fittings demonstrated that this model could well describe the kinetics of the Ti（IV）-catalyzed H2O2/O3 reaction mathematically and chemically. Therefore, this kinetic model can provide some useful information to optimize the parameters in ozonation of water containing certain pollutants.
文摘在假设里氏木霉ATCC56764产生的壳聚糖酶水解壳聚糖是以唯一内切方式随机进攻 b -1,4糖苷键的基础上,结合终产物非竞争性抑制的M-M动力学,建立了壳聚糖降解的数学模型,并用四阶Runge-Kutta方法结合Powell优化方法对模型中各个动力学参数进行了优化。模型计算结果与实验数据的比较表明,建立的数学模型能够合理地描述和解释壳聚糖降解的动力学过程,有助于加深对壳聚糖酶法降解机理的认识,对生产特定聚合度的壳聚糖具有指导意义。
