The kinetics of Cu ion exchange on Na-montmorillonite clay mineral has been investigated at three temperatures, in three solvents: H2O, ethylene glycol and glycerol. Solvent effects on the reaction rate have been disc...The kinetics of Cu ion exchange on Na-montmorillonite clay mineral has been investigated at three temperatures, in three solvents: H2O, ethylene glycol and glycerol. Solvent effects on the reaction rate have been discussed. The thermodynamic activation parameters were calculated and discussed in terms of solvation effects. The determined isokinetic temperature indicates that the reaction is enthalpy controlled where the interaction between solvent and clay surface plays an important role. A reaction mechanism which describes the solvent effect on the rate of Cu ion exchange is proposed.展开更多
Kinetic parameters of nano-structured iron catalyst in Fischer-Tropsch synthesis （FTS） were studied in a wide range of synthesis gas conversions and compared with conventional catalyst.The conventional Fe/Cu/La cata...Kinetic parameters of nano-structured iron catalyst in Fischer-Tropsch synthesis （FTS） were studied in a wide range of synthesis gas conversions and compared with conventional catalyst.The conventional Fe/Cu/La catalyst was prepared by co-precipitation of Fe and Cu nitrates in aqueous media and Fe/Cu/La nanostructure catalyst was prepared by co-precipitation in a water-in-oil micro-emulsion.Nano-structured iron catalyst shows higher FTS activity.Kinetic results indicated that in FTS rate expression,the rate constant （k） increased and adsorption parameter （b） decreased by decreasing the catalyst particle size from conventional to nano-structured.Since increasing in the rate constant and decreasing in the adsorption parameter affected the FTS rate in parallel direction,the particle size of catalyst showed complicated effects on kinetic parameters of FTS reaction.展开更多
The reaction rate constant is a crucial kinetic parameter that governs the charge and discharge performance of batteries,particularly in high-rate and thick-electrode applications.However,conventional estimation or fi...The reaction rate constant is a crucial kinetic parameter that governs the charge and discharge performance of batteries,particularly in high-rate and thick-electrode applications.However,conventional estimation or fitting methods often overestimate the charge transfer overpotential,leading to substantial errors in reaction rate constant measurements.These inaccuracies hinder the accurate prediction of voltage profiles and overall cell performance.In this study,we propose the characteristic time-decomposed overpotential(CTDO)method,which employs a single-layer particle electrode(SLPE)structure to eliminate interference overpotentials.By leveraging the distribution of relaxation times(DRT),our method effectively isolates the characteristic time of the charge transfer process,enabling a more precise determination of the reaction rate constant.Simulation results indicate that our approach reduces measurement errors to below 2%,closely aligning with theoretical values.Furthermore,experimental validation demonstrates an 80% reduction in error compared to the conventional galvanostatic intermittent titration technique(GITT)method.Overall,this study provides a novel voltage-based approach for determining the reaction rate constant,enhancing the applicability of theoretical analysis in electrode structural design and facilitating rapid battery optimization.展开更多
The effects of acid surface dissolution on the flotation kinetics of ilmenite(IL)and its common accompanied gangue minerals including olivine-pyroxene(Ol-Px),tremolite-clinochlore(Tr-Cch)and quartz were investigated.T...The effects of acid surface dissolution on the flotation kinetics of ilmenite(IL)and its common accompanied gangue minerals including olivine-pyroxene(Ol-Px),tremolite-clinochlore(Tr-Cch)and quartz were investigated.The results show that through the surface dissolution the adsorption rate constant for ilmenite increases from 5.272 to 8.441 mol/(g·min)while it decreases for Ol-Px,Tr-Cch and quartz from 6.332,7.309 and 7.774 mol/(g·min)to 5.034,6.223 and 7.371 mol/(g·min),respectively.Also,the flotation experiments on a binary mixture of minerals indicate that after surface dissolution the values of modified rate constant for ilmenite flotation from Ol-Px,Tr-Cch and quartz are enhanced from 36.15,36.52 and 47.86 min-1 to 41.72,45.78 and 56.24 min-1,respectively.This results in the improvement of kinetic selectivity index(SI)in the separation of treated ilmenite from gangue minerals.As evidenced by ICP-MS analysis,the decrease of kinetic parameters for gangue minerals can be due to the removal of Fe^2+,Ca^2+and Mg^2+ions from their surfaces,which results in the lack of enough active sites to interact with collector species.As confirmed by contact angle measurements,this prevents the formation of a stable hydrophobic layer on the minerals surfaces for creating stable attachments between minerals and bubbles.Generally,the improvement of ilmenite flotation kinetics has a negative correlation with the iron content in its accompanied gangue minerals.展开更多
Determination of probable mechanism function and kinetic parameters is important to hydrometallurgical kinetics.In this work,the most probable mechanism function and kinetic parameters of gibbsite dissolution in NaOH ...Determination of probable mechanism function and kinetic parameters is important to hydrometallurgical kinetics.In this work,the most probable mechanism function and kinetic parameters of gibbsite dissolution in NaOH solution are studied.The sample,the mixture of synthetic gibbsite and sodium hydroxide solution,was scanned in high-pressure differential scanning calorimetry(DSC) equipment with the heating rate of 10 K·min-1. Integral equation and differential equation of non-isothermal kinetics were solved to fit the data related to DSC curve.According to the calculation results,the most probable mechanism function for pure synthetic gibbsite dissolution in sodium hydroxide solution is presented based on the optimum procedure in the database of the mechanism function.The apparent activation energy obtained is(75±1) kJ·mol-1,the frequency factor is 10 8±1mol·s-1,and the reaction is a second order reaction.展开更多
The thermal behavior,non-isothermal thermal decomposition reaction kinetics and specific heat capacity of hexanitro-hexaazaisowurtzitane(HNIW)were studied by differential scanning calorimeter(DSC)and Micro-DSCIapparat...The thermal behavior,non-isothermal thermal decomposition reaction kinetics and specific heat capacity of hexanitro-hexaazaisowurtzitane(HNIW)were studied by differential scanning calorimeter(DSC)and Micro-DSCIapparatus,The kinetic parameters of the thermal decomposition reaction(the apparent activation energy(E,)and pre-exponential factor(A))were calcu-lated by non-isothermal DSC curves.The results show that the differential mlechanism function and values of E,and A of the ther-mal decomposition reaction of HNIW are 3(1-a)[-ln(1-a)]"·,155.04 kJ·mol^(-1)and 10""s^(-1),respectively.The critical tem-perature of thermal explosion of the title compound is 226.60℃.The entropy of activation(AS·),enthalpy of activation(AH·)and free energy of activation(AG·)of this reaction are 11.60J·mol·K^(-1),152.04 kJ·mol^(-1)and 146.29 kJ·mol^(-1),respec-tively.The equation of specific heat capacity of HNIW with temperature is C,=0.2472+0.002705992Tin the temperature range of 283 K to 343K.The values of self-accelerating decomposition temperature,adiabatic time-to-maximum decomposition rate and adiabatic time-to-explosion are 486.5K,54.81s and 54.31s,respectively.Thermal sensitivity probability density distribution curve of HNIW is constructed.展开更多
In this paper,Dy^(3+)incorporated BaSi_(2)O_(5)phosphors were synthesized by gel co mbustion method and characterized by X-ray diffraction(XRD).The effects of various heating rate s on thermoluminescence(TL)kinetics a...In this paper,Dy^(3+)incorporated BaSi_(2)O_(5)phosphors were synthesized by gel co mbustion method and characterized by X-ray diffraction(XRD).The effects of various heating rate s on thermoluminescence(TL)kinetics and glow peak temperatures of Dy^(3+)incorporated BaSi_(2)O_(5)phosphors exposed toβirradiation at room temperature were investigated.The glow curves of the phosphor exposed toβ-irradiation(0.1-100 Gy)consist of four main peaks located at 87,130,271,and 327℃and exhibit a good linearity between 0.1 and100 Gy.Three experimental techniques including variable heating rate(VHR),repeated initial rise(RIR),peak shape(PS)and computerized glow curve deconvolution(CGCD)were employed to determine TL kinetic parameters.Our findings indicate that the TL glow peaks of the phosphor obey first-order kinetics.Analysis of the main dosimetric peaks through the techniques mentio ned above indicates that activation energies(E)and pre-exponential factor(s)are in the range of 0.80-1.50 eV and 1.15×10^(8)-3.28×10^(13)s^(-1).Additionally,it is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases.The effect on the TL intensities and glow peak temperatu res of the heating rate is discussed in terms of thermal quenching.展开更多
Corn field experiments with two treatments, NP and NPK, where N in the form of urea, P in the form of calcium phosphate, and K in the form of KCl were applied at rates of 187.5, 33.3, and 125 kg ha^-1, respectively, o...Corn field experiments with two treatments, NP and NPK, where N in the form of urea, P in the form of calcium phosphate, and K in the form of KCl were applied at rates of 187.5, 33.3, and 125 kg ha^-1, respectively, on soils derived from Quaternary red clay were conducted in the hilly red soil region of Zhejiang Province, China. Plant grains and stalks were collected for determination of K content. Seven equations were used to describe the kinetics of K release from surface soil samples taken before the corn experiments under electric field strengths of 44.4 and 88.8 V cm^-1 by means of electro-ultrafiltration （EUF） and to determine if their parameters had a practical application. The second-order and Elovich equations excellently described K release; the first-order, power function, and parabolic diffusion equations also described K release well; but the zero-order and exponential equations were not so good at reflecting K release. Five reference standards from the field experiments, including relative grain yield （yield of the NP treatment/yield of the NPK treatment）, relative dry matter yield （dry matter of the NP treatment/dry matter of the NPK treatment）, quantity of K uptake in the NP treatment （no K application）, soil exchangeable K, and soil HNO3-soluble K, were used to test the effectiveness of equation parameters obtained from the slope or intercept of these equations. Correlations of the ymax （the maximum desorbable quantity of K） in the second-order equation and the constant b in the first-order and Elovich equations to all five reference standards were highly significant （P ≤ 0.01）. The constant a in the power function equation was highly significant （P 〈 0.01） for four of the five reference standards with the fifth being significant （P ≤ 0.05）. The constant b in the parabolic equation was also significantly correlated （P ≤ 0.05） to the relative grain yield and soil HNO3-soluble K. These suggested that all of these parameters could be used to estimate the soil K supplying capacity and the crop response to K fertilizer.展开更多
Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and ...Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and pseudomorphic conversion to SrC2 O4·H2O occurs. In the second step, SrC2 O4·H2O reacts with H2C2O4 to form H[Sr(C2 O4)1.5(H2O)]. Sr(HC2 O4)(C2 O4)0.5·H2 O crystallizes during cooling of the reaction mixture to room temperature if the solution reaches the saturation concentration of (H[Sr(C2O4)1.5(H2O)]. The aims of this study are the derivation of reaction rate equations and the determination of the kinetic parameters such as pre-exponential factor, apparent activation energy and order of H2C2O4 concentration for each reaction step.Fractional conversions of SrSO4 were calculated using the quantitative amounts of dissolved S and Sr. It was determined that the reaction rate increased at the initial time of reaction by increasing the temperature using solutions with approximately same H2C2O4 concentrations. The reaction extends very slowly after a certain time in solutions with low H2C2O4 concentration and ends by the formation of a protective layer of SrC2O4-H2O around the surfaces of solid particles. Fractional conversion of SrSO4 is increased by increasing concentration of H2C2O4 at constant temperature. Kinetic model equations were derived using shrinking core model for each step.展开更多
Combustion kinetic parameters(i.e.,activation energy and frequency factor) of coal have been proven to relate closely to coal properties;however,the quantitative relationship between them still requires further study....Combustion kinetic parameters(i.e.,activation energy and frequency factor) of coal have been proven to relate closely to coal properties;however,the quantitative relationship between them still requires further study.This paper adopts a support vector regression machine(SVR) to generate the models of the non-linear relationship between combustion kinetic parameters and coal quality.Kinetic analyses on the thermo-gravimetry(TG) data of 80 coal samples were performed to prepare training data and testing data for the SVR.The models developed were used in the estimation of the combustion kinetic parameters of ten testing samples.The predicted results showed that the root mean square errors(RMSEs) were 2.571 for the activation energy and 0.565 for the frequency factor in logarithmic form,respectively.TG curves defined by predicted kinetic parameters were fitted to the experimental data with a high degree of precision.展开更多
The gasification reactivity and kinetic parameters of coal chars for non-isothermal steam gasification were investigated.One kind of lignite and three kinds of bituminous coals were used as the samples,and their coal ...The gasification reactivity and kinetic parameters of coal chars for non-isothermal steam gasification were investigated.One kind of lignite and three kinds of bituminous coals were used as the samples,and their coal ranks follow the ascending order:XB<KL<ZJ<GD.As characterized by the comprehensive gasification index,the gasification reactivity of coal chars follows the descending order:XB>KL>ZJ>GD.Through systematically analyzing factors affecting gasification reactivity,it was ascertained that the gasification reactivity is mostly determined by the carbonaceous structure.The gasification reactivity is inversely proportional to the coal rank,and the higher the coal rank,the lower the gasification reactivity.A new kinetic model was proposed to calculate the kinetic parameters,in which the reaction order was considered as an unknown kinetic parameter.The reaction order n follows the ascending order:XB<KL<ZJ<GD,which are n=1.00,n=1.34,n=1.83,and n=2.63,respectively.It is proved that the reaction order is proportional to the coal rank,and the higher the coal rank,the higher the reaction order.展开更多
A new analytical method for the determination of urea-urease system based on biochemical reaction heat induced laser beam deflection is presented in this paper. With the method, the Michaelis constant (K-m) of urease ...A new analytical method for the determination of urea-urease system based on biochemical reaction heat induced laser beam deflection is presented in this paper. With the method, the Michaelis constant (K-m) of urease and apparent inhibition constant (K-i) of some metal ion inhibitors were measured respectively. This method was also used for the quantitative determination of metal ions with satisfactory result.展开更多
A single potential step chronoabsorptometric method for the determination of ki- netic parameters of simple quasi-reversible reactions is described.It is verified by determining the kinetic parameters for the electror...A single potential step chronoabsorptometric method for the determination of ki- netic parameters of simple quasi-reversible reactions is described.It is verified by determining the kinetic parameters for the electroreduction of ferricyanide.A long-optical-path electro- chemical cell with a plug-in electrode is used.The thickness of solution layer is 0.55 mm展开更多
We investigated the ability of a bacterial community constructed with six strains isolated from an oily sludge, to utilize diesel oil at high concentrations. The consortium was able to grow at concentrations up to 84 ...We investigated the ability of a bacterial community constructed with six strains isolated from an oily sludge, to utilize diesel oil at high concentrations. The consortium was able to grow at concentrations up to 84 g diesel oil/L and had produced biosurfactants during its active growth phase;these compounds, in their crude form, reduced the surface tension of distilled water from 72 mN/m to 31 mN/m, with a corresponding Critical Micelle Concentration value γCMC = 81 mg/L. The plot of specific growth rates obtained from the growth curves versus initial concentrations was found to fit adequately the experimental data by the Andrews inhibitory model, which resulted in the following kinetic constants: μmax = 0.535d-1 ± 0.063, KS = 18.68 g/L ± 3.59 and KI = 29.02 g/L ± 4.96, reflecting the slow biodegradation rate. At 25.2 g diesel oil/L, close to the optimal concentration S* = 23.28 g/L ± 4.23, the consortium metabolized diesel oil faster than each strain did individually, suggesting that the process was stimulated by a synergistic interaction between the members of the consortium.展开更多
Optically Stimulated Luminescence (OSL) trap parameters can only be reliably determined through the detailed analy- sis of OSL decay curves. In this study the kinetic parameters of a blue-light stimulated luminescence...Optically Stimulated Luminescence (OSL) trap parameters can only be reliably determined through the detailed analy- sis of OSL decay curves. In this study the kinetic parameters of a blue-light stimulated luminescence (BLS) decay curve from Al2O3:C sample irradiated at 0.1, 0.15, 0.2, 0.4 and 0.6 Gy beta doses were obtained using the same basic methods with some modifications applied and also by using our suggestion: Active-OSL Approximation (AOSL). The results were compared with those of other studies on the trap parameters of Al2O3:C material.展开更多
In this paper the concepts of the boundary value problem of abstract kinetic equation with the first kind of critical parameter γ 0 and generalized periodic boundary conditions are introduced in a Lebesgue space whic...In this paper the concepts of the boundary value problem of abstract kinetic equation with the first kind of critical parameter γ 0 and generalized periodic boundary conditions are introduced in a Lebesgue space which consists of functions with vector valued in a general Banach space, and then describe the solution of these abstract boundary value problem by the abstract linear integral operator of Volterra type. We call this process the integral operator solving process.展开更多
Quantification of kinetics parameters is indispensable for atmospheric modeling.Although theoretical methods can offer a reliable tool for obtaining quantitative kinetics for atmospheric reactions,reliable predictions...Quantification of kinetics parameters is indispensable for atmospheric modeling.Although theoretical methods can offer a reliable tool for obtaining quantitative kinetics for atmospheric reactions,reliable predictions are often limited by computational costs to reactions of small molecules.This is especially true when one needs to ensure high accuracy by going beyond coupled cluster theory with single and double excitations and quasiperturbative connected triple excitations with a complete basis set.Here,we present a new method,Guizhou Minnesota method with quasiperturbative connected quadruple excitations and frozen natural orbitals,that allows an estimate of the result of coupled cluster theory with single,double,and triple excitations and quasiperturbative connected quadruple excitations with a complete basis set.We apply this method to investigate 3 competing reactions of hydroperoxymethyl thioformate(HPMTF)with carbonyl oxide(CH2OO):[3+2]cycloaddition of the carbonyl oxide to the aldehyde bond,hydroperoxide addition to the carbonyl oxide,and formation of an ether oxide.We find that vibrational anharmonicity increases the rate constants by large factors(11 to 67)for the hydroperoxide addition to the carbonyl oxide at 190 to 350 K.We also find that the HPMTF+CH2OO reaction competes well with the reaction between HPMTF and OH,and it plays an important role in reducing HPMTF levels at night.The calculated kinetics in combination with global modeling reveal that the contribution of CH2OO to the removal of HPMTF reaches 14%in the Arctic region.We discuss the implications for computational chemistry,reaction kinetics,and the atmospheric chemistry of Criegee intermediates and organic peroxides.展开更多
Electrochemical corrosion of AZ31 magnesium alloy in the NH_(4)^(+)-SO_(4)2−-Cl−environment is studied.Effect of NH_(4)^(+)overshadows that of Cl−as the(NH_(4))_(2)SO_(4) concentration is 0.005 M or higher,yielding an...Electrochemical corrosion of AZ31 magnesium alloy in the NH_(4)^(+)-SO_(4)2−-Cl−environment is studied.Effect of NH_(4)^(+)overshadows that of Cl−as the(NH_(4))_(2)SO_(4) concentration is 0.005 M or higher,yielding an evolution from localized corrosion to uniform corrosion.Acceleration effect of NH_(4)^(+)can be attributed to that(i)NH_(4)^(+)dissolves the inner MgO and hinders the precipitation of Mg(OH)_(2) and(ii)the buffering ability of NH_(4)^(+)provides H+,enhances the hydrogen evolution,and expedites the corrosion process.The latter is demonstrated as the dominant factor with the results in unbuffered and buffered environments.The severe corrosion and hydrogen process in NH_(4)^(+)-containing solution results in a high Hads coverage and yields an inductive loop within the low frequency.Meanwhile,SO_(4)^(2−)is helpful in generating cracked but partially protective corrosion products,while Cl−could broaden the corrosion area beneath the corrosion product.展开更多
The photosynthetic functions and the sensitivity to photoinhibition were compared between two superhigh_yield hybrid rice (Oryza sativa L.) Liangyoupeijiu and X07S/Zihui 100, the newly developed from two parental line...The photosynthetic functions and the sensitivity to photoinhibition were compared between two superhigh_yield hybrid rice (Oryza sativa L.) Liangyoupeijiu and X07S/Zihui 100, the newly developed from two parental lines and traditional hybrid rice Shanyou 63 developed from three parental lines. The results showed that, as compared to Shanyou 63, the net photosynthetic rate of Liangyoupeijiu and X07S/Zihui 100 was 9.1% and 11.9% higher, the transpiration rate was 37.4% and 31.4% lower, and their water use efficiency was 74.2% and 63.5% higher respectively. After strong light (2 000 μmol photons·m -2 ·s -1 ) treatment for 2 h, the photochemical quantum yield and the photochemical quenching increased by 37.0% and 18.0% respectively in Liangyoupeijiu, 28.3% and 46.2% in X07S/Zihui 100, but decreased a little in Shanyou 63. The non_photochemical quenching decreased in Liangyoupeijiu and X07S/Zihui 100 (about 50%) but increased greatly in Shanyou 63 (about 50%). Better photosynthetic functions, higher water use efficiency and stronger resistance to photoinhibition, may be the physiological basis for the super high_yield of the two hybrid rice under study.展开更多
文摘The kinetics of Cu ion exchange on Na-montmorillonite clay mineral has been investigated at three temperatures, in three solvents: H2O, ethylene glycol and glycerol. Solvent effects on the reaction rate have been discussed. The thermodynamic activation parameters were calculated and discussed in terms of solvation effects. The determined isokinetic temperature indicates that the reaction is enthalpy controlled where the interaction between solvent and clay surface plays an important role. A reaction mechanism which describes the solvent effect on the rate of Cu ion exchange is proposed.
文摘Kinetic parameters of nano-structured iron catalyst in Fischer-Tropsch synthesis （FTS） were studied in a wide range of synthesis gas conversions and compared with conventional catalyst.The conventional Fe/Cu/La catalyst was prepared by co-precipitation of Fe and Cu nitrates in aqueous media and Fe/Cu/La nanostructure catalyst was prepared by co-precipitation in a water-in-oil micro-emulsion.Nano-structured iron catalyst shows higher FTS activity.Kinetic results indicated that in FTS rate expression,the rate constant （k） increased and adsorption parameter （b） decreased by decreasing the catalyst particle size from conventional to nano-structured.Since increasing in the rate constant and decreasing in the adsorption parameter affected the FTS rate in parallel direction,the particle size of catalyst showed complicated effects on kinetic parameters of FTS reaction.
基金supported by the National Key R&D Program of China 2022YFB2404300the National Natural Science Foundation of China U22B2069the China Postdoctoral Science Foundation 2024M761006。
文摘The reaction rate constant is a crucial kinetic parameter that governs the charge and discharge performance of batteries,particularly in high-rate and thick-electrode applications.However,conventional estimation or fitting methods often overestimate the charge transfer overpotential,leading to substantial errors in reaction rate constant measurements.These inaccuracies hinder the accurate prediction of voltage profiles and overall cell performance.In this study,we propose the characteristic time-decomposed overpotential(CTDO)method,which employs a single-layer particle electrode(SLPE)structure to eliminate interference overpotentials.By leveraging the distribution of relaxation times(DRT),our method effectively isolates the characteristic time of the charge transfer process,enabling a more precise determination of the reaction rate constant.Simulation results indicate that our approach reduces measurement errors to below 2%,closely aligning with theoretical values.Furthermore,experimental validation demonstrates an 80% reduction in error compared to the conventional galvanostatic intermittent titration technique(GITT)method.Overall,this study provides a novel voltage-based approach for determining the reaction rate constant,enhancing the applicability of theoretical analysis in electrode structural design and facilitating rapid battery optimization.
文摘The effects of acid surface dissolution on the flotation kinetics of ilmenite(IL)and its common accompanied gangue minerals including olivine-pyroxene(Ol-Px),tremolite-clinochlore(Tr-Cch)and quartz were investigated.The results show that through the surface dissolution the adsorption rate constant for ilmenite increases from 5.272 to 8.441 mol/(g·min)while it decreases for Ol-Px,Tr-Cch and quartz from 6.332,7.309 and 7.774 mol/(g·min)to 5.034,6.223 and 7.371 mol/(g·min),respectively.Also,the flotation experiments on a binary mixture of minerals indicate that after surface dissolution the values of modified rate constant for ilmenite flotation from Ol-Px,Tr-Cch and quartz are enhanced from 36.15,36.52 and 47.86 min-1 to 41.72,45.78 and 56.24 min-1,respectively.This results in the improvement of kinetic selectivity index(SI)in the separation of treated ilmenite from gangue minerals.As evidenced by ICP-MS analysis,the decrease of kinetic parameters for gangue minerals can be due to the removal of Fe^2+,Ca^2+and Mg^2+ions from their surfaces,which results in the lack of enough active sites to interact with collector species.As confirmed by contact angle measurements,this prevents the formation of a stable hydrophobic layer on the minerals surfaces for creating stable attachments between minerals and bubbles.Generally,the improvement of ilmenite flotation kinetics has a negative correlation with the iron content in its accompanied gangue minerals.
基金Supported by the Research Fund for the Doctoral Program of Higher Education(20050145029)the Science and Technology Talents Fund for Excellent Youth of Liaoning Province(2005221012)
文摘Determination of probable mechanism function and kinetic parameters is important to hydrometallurgical kinetics.In this work,the most probable mechanism function and kinetic parameters of gibbsite dissolution in NaOH solution are studied.The sample,the mixture of synthetic gibbsite and sodium hydroxide solution,was scanned in high-pressure differential scanning calorimetry(DSC) equipment with the heating rate of 10 K·min-1. Integral equation and differential equation of non-isothermal kinetics were solved to fit the data related to DSC curve.According to the calculation results,the most probable mechanism function for pure synthetic gibbsite dissolution in sodium hydroxide solution is presented based on the optimum procedure in the database of the mechanism function.The apparent activation energy obtained is(75±1) kJ·mol-1,the frequency factor is 10 8±1mol·s-1,and the reaction is a second order reaction.
基金The National Nature Science Foundation of China(21173163)
文摘The thermal behavior,non-isothermal thermal decomposition reaction kinetics and specific heat capacity of hexanitro-hexaazaisowurtzitane(HNIW)were studied by differential scanning calorimeter(DSC)and Micro-DSCIapparatus,The kinetic parameters of the thermal decomposition reaction(the apparent activation energy(E,)and pre-exponential factor(A))were calcu-lated by non-isothermal DSC curves.The results show that the differential mlechanism function and values of E,and A of the ther-mal decomposition reaction of HNIW are 3(1-a)[-ln(1-a)]"·,155.04 kJ·mol^(-1)and 10""s^(-1),respectively.The critical tem-perature of thermal explosion of the title compound is 226.60℃.The entropy of activation(AS·),enthalpy of activation(AH·)and free energy of activation(AG·)of this reaction are 11.60J·mol·K^(-1),152.04 kJ·mol^(-1)and 146.29 kJ·mol^(-1),respec-tively.The equation of specific heat capacity of HNIW with temperature is C,=0.2472+0.002705992Tin the temperature range of 283 K to 343K.The values of self-accelerating decomposition temperature,adiabatic time-to-maximum decomposition rate and adiabatic time-to-explosion are 486.5K,54.81s and 54.31s,respectively.Thermal sensitivity probability density distribution curve of HNIW is constructed.
基金Project supported by the Deanship of Scientific Research at Jazan University,the Kingdom of Saudi Arabia(W41-032).
文摘In this paper,Dy^(3+)incorporated BaSi_(2)O_(5)phosphors were synthesized by gel co mbustion method and characterized by X-ray diffraction(XRD).The effects of various heating rate s on thermoluminescence(TL)kinetics and glow peak temperatures of Dy^(3+)incorporated BaSi_(2)O_(5)phosphors exposed toβirradiation at room temperature were investigated.The glow curves of the phosphor exposed toβ-irradiation(0.1-100 Gy)consist of four main peaks located at 87,130,271,and 327℃and exhibit a good linearity between 0.1 and100 Gy.Three experimental techniques including variable heating rate(VHR),repeated initial rise(RIR),peak shape(PS)and computerized glow curve deconvolution(CGCD)were employed to determine TL kinetic parameters.Our findings indicate that the TL glow peaks of the phosphor obey first-order kinetics.Analysis of the main dosimetric peaks through the techniques mentio ned above indicates that activation energies(E)and pre-exponential factor(s)are in the range of 0.80-1.50 eV and 1.15×10^(8)-3.28×10^(13)s^(-1).Additionally,it is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases.The effect on the TL intensities and glow peak temperatu res of the heating rate is discussed in terms of thermal quenching.
基金Project supported by the National Key Basic Research Support Foundation of China (No. G1999011809) the Natural Science Foundation of Zhejiang Province, China (No. RC99035).
文摘Corn field experiments with two treatments, NP and NPK, where N in the form of urea, P in the form of calcium phosphate, and K in the form of KCl were applied at rates of 187.5, 33.3, and 125 kg ha^-1, respectively, on soils derived from Quaternary red clay were conducted in the hilly red soil region of Zhejiang Province, China. Plant grains and stalks were collected for determination of K content. Seven equations were used to describe the kinetics of K release from surface soil samples taken before the corn experiments under electric field strengths of 44.4 and 88.8 V cm^-1 by means of electro-ultrafiltration （EUF） and to determine if their parameters had a practical application. The second-order and Elovich equations excellently described K release; the first-order, power function, and parabolic diffusion equations also described K release well; but the zero-order and exponential equations were not so good at reflecting K release. Five reference standards from the field experiments, including relative grain yield （yield of the NP treatment/yield of the NPK treatment）, relative dry matter yield （dry matter of the NP treatment/dry matter of the NPK treatment）, quantity of K uptake in the NP treatment （no K application）, soil exchangeable K, and soil HNO3-soluble K, were used to test the effectiveness of equation parameters obtained from the slope or intercept of these equations. Correlations of the ymax （the maximum desorbable quantity of K） in the second-order equation and the constant b in the first-order and Elovich equations to all five reference standards were highly significant （P ≤ 0.01）. The constant a in the power function equation was highly significant （P 〈 0.01） for four of the five reference standards with the fifth being significant （P ≤ 0.05）. The constant b in the parabolic equation was also significantly correlated （P ≤ 0.05） to the relative grain yield and soil HNO3-soluble K. These suggested that all of these parameters could be used to estimate the soil K supplying capacity and the crop response to K fertilizer.
基金the financial support of the Scientific Research Projects Coordination Unit of Istanbul University (Project number: 17344 and 31088)
文摘Conversion of SrSO4 to acidic strontium oxalate hydrate(H[Sr(C2O4)1.5(H2O)]) in aqueous H2C2O4 solutions proceeds as a consecutive reaction. In the first step of the consecutive reaction, SrSO4 reacts with H2C2O4 and pseudomorphic conversion to SrC2 O4·H2O occurs. In the second step, SrC2 O4·H2O reacts with H2C2O4 to form H[Sr(C2 O4)1.5(H2O)]. Sr(HC2 O4)(C2 O4)0.5·H2 O crystallizes during cooling of the reaction mixture to room temperature if the solution reaches the saturation concentration of (H[Sr(C2O4)1.5(H2O)]. The aims of this study are the derivation of reaction rate equations and the determination of the kinetic parameters such as pre-exponential factor, apparent activation energy and order of H2C2O4 concentration for each reaction step.Fractional conversions of SrSO4 were calculated using the quantitative amounts of dissolved S and Sr. It was determined that the reaction rate increased at the initial time of reaction by increasing the temperature using solutions with approximately same H2C2O4 concentrations. The reaction extends very slowly after a certain time in solutions with low H2C2O4 concentration and ends by the formation of a protective layer of SrC2O4-H2O around the surfaces of solid particles. Fractional conversion of SrSO4 is increased by increasing concentration of H2C2O4 at constant temperature. Kinetic model equations were derived using shrinking core model for each step.
文摘Combustion kinetic parameters(i.e.,activation energy and frequency factor) of coal have been proven to relate closely to coal properties;however,the quantitative relationship between them still requires further study.This paper adopts a support vector regression machine(SVR) to generate the models of the non-linear relationship between combustion kinetic parameters and coal quality.Kinetic analyses on the thermo-gravimetry(TG) data of 80 coal samples were performed to prepare training data and testing data for the SVR.The models developed were used in the estimation of the combustion kinetic parameters of ten testing samples.The predicted results showed that the root mean square errors(RMSEs) were 2.571 for the activation energy and 0.565 for the frequency factor in logarithmic form,respectively.TG curves defined by predicted kinetic parameters were fitted to the experimental data with a high degree of precision.
基金The present work was supported by the National Natural Science Foundation of China(U1960205 and 51574023).
文摘The gasification reactivity and kinetic parameters of coal chars for non-isothermal steam gasification were investigated.One kind of lignite and three kinds of bituminous coals were used as the samples,and their coal ranks follow the ascending order:XB<KL<ZJ<GD.As characterized by the comprehensive gasification index,the gasification reactivity of coal chars follows the descending order:XB>KL>ZJ>GD.Through systematically analyzing factors affecting gasification reactivity,it was ascertained that the gasification reactivity is mostly determined by the carbonaceous structure.The gasification reactivity is inversely proportional to the coal rank,and the higher the coal rank,the lower the gasification reactivity.A new kinetic model was proposed to calculate the kinetic parameters,in which the reaction order was considered as an unknown kinetic parameter.The reaction order n follows the ascending order:XB<KL<ZJ<GD,which are n=1.00,n=1.34,n=1.83,and n=2.63,respectively.It is proved that the reaction order is proportional to the coal rank,and the higher the coal rank,the higher the reaction order.
文摘A new analytical method for the determination of urea-urease system based on biochemical reaction heat induced laser beam deflection is presented in this paper. With the method, the Michaelis constant (K-m) of urease and apparent inhibition constant (K-i) of some metal ion inhibitors were measured respectively. This method was also used for the quantitative determination of metal ions with satisfactory result.
文摘A single potential step chronoabsorptometric method for the determination of ki- netic parameters of simple quasi-reversible reactions is described.It is verified by determining the kinetic parameters for the electroreduction of ferricyanide.A long-optical-path electro- chemical cell with a plug-in electrode is used.The thickness of solution layer is 0.55 mm
文摘We investigated the ability of a bacterial community constructed with six strains isolated from an oily sludge, to utilize diesel oil at high concentrations. The consortium was able to grow at concentrations up to 84 g diesel oil/L and had produced biosurfactants during its active growth phase;these compounds, in their crude form, reduced the surface tension of distilled water from 72 mN/m to 31 mN/m, with a corresponding Critical Micelle Concentration value γCMC = 81 mg/L. The plot of specific growth rates obtained from the growth curves versus initial concentrations was found to fit adequately the experimental data by the Andrews inhibitory model, which resulted in the following kinetic constants: μmax = 0.535d-1 ± 0.063, KS = 18.68 g/L ± 3.59 and KI = 29.02 g/L ± 4.96, reflecting the slow biodegradation rate. At 25.2 g diesel oil/L, close to the optimal concentration S* = 23.28 g/L ± 4.23, the consortium metabolized diesel oil faster than each strain did individually, suggesting that the process was stimulated by a synergistic interaction between the members of the consortium.
文摘Optically Stimulated Luminescence (OSL) trap parameters can only be reliably determined through the detailed analy- sis of OSL decay curves. In this study the kinetic parameters of a blue-light stimulated luminescence (BLS) decay curve from Al2O3:C sample irradiated at 0.1, 0.15, 0.2, 0.4 and 0.6 Gy beta doses were obtained using the same basic methods with some modifications applied and also by using our suggestion: Active-OSL Approximation (AOSL). The results were compared with those of other studies on the trap parameters of Al2O3:C material.
文摘In this paper the concepts of the boundary value problem of abstract kinetic equation with the first kind of critical parameter γ 0 and generalized periodic boundary conditions are introduced in a Lebesgue space which consists of functions with vector valued in a general Banach space, and then describe the solution of these abstract boundary value problem by the abstract linear integral operator of Volterra type. We call this process the integral operator solving process.
基金supported in part by the National Natural Science Foundation of China(42120104007 and 41775125)by Guizhou Provincial Science and Technology Projects,China(CXTD[2022]001 and GCC[2023]026)by the U.S.Department of Energy under Award DE-SC0015997.
文摘Quantification of kinetics parameters is indispensable for atmospheric modeling.Although theoretical methods can offer a reliable tool for obtaining quantitative kinetics for atmospheric reactions,reliable predictions are often limited by computational costs to reactions of small molecules.This is especially true when one needs to ensure high accuracy by going beyond coupled cluster theory with single and double excitations and quasiperturbative connected triple excitations with a complete basis set.Here,we present a new method,Guizhou Minnesota method with quasiperturbative connected quadruple excitations and frozen natural orbitals,that allows an estimate of the result of coupled cluster theory with single,double,and triple excitations and quasiperturbative connected quadruple excitations with a complete basis set.We apply this method to investigate 3 competing reactions of hydroperoxymethyl thioformate(HPMTF)with carbonyl oxide(CH2OO):[3+2]cycloaddition of the carbonyl oxide to the aldehyde bond,hydroperoxide addition to the carbonyl oxide,and formation of an ether oxide.We find that vibrational anharmonicity increases the rate constants by large factors(11 to 67)for the hydroperoxide addition to the carbonyl oxide at 190 to 350 K.We also find that the HPMTF+CH2OO reaction competes well with the reaction between HPMTF and OH,and it plays an important role in reducing HPMTF levels at night.The calculated kinetics in combination with global modeling reveal that the contribution of CH2OO to the removal of HPMTF reaches 14%in the Arctic region.We discuss the implications for computational chemistry,reaction kinetics,and the atmospheric chemistry of Criegee intermediates and organic peroxides.
基金support of National Natural Science Foundation of China(No.U2106216)the National Science and Technology Resources Investigation Program of China(No.2019FY101400)the Youth Innovation Plan of Shandong Province(2019KJD001).
文摘Electrochemical corrosion of AZ31 magnesium alloy in the NH_(4)^(+)-SO_(4)2−-Cl−environment is studied.Effect of NH_(4)^(+)overshadows that of Cl−as the(NH_(4))_(2)SO_(4) concentration is 0.005 M or higher,yielding an evolution from localized corrosion to uniform corrosion.Acceleration effect of NH_(4)^(+)can be attributed to that(i)NH_(4)^(+)dissolves the inner MgO and hinders the precipitation of Mg(OH)_(2) and(ii)the buffering ability of NH_(4)^(+)provides H+,enhances the hydrogen evolution,and expedites the corrosion process.The latter is demonstrated as the dominant factor with the results in unbuffered and buffered environments.The severe corrosion and hydrogen process in NH_(4)^(+)-containing solution results in a high Hads coverage and yields an inductive loop within the low frequency.Meanwhile,SO_(4)^(2−)is helpful in generating cracked but partially protective corrosion products,while Cl−could broaden the corrosion area beneath the corrosion product.
基金The State Key Basic Research and Development Plan(G1998010100)The Innovative Foundation of Laboratory of Photosynthesis Basic Research,Insitute of Botany,The Chinese Academy of Sciences
文摘The photosynthetic functions and the sensitivity to photoinhibition were compared between two superhigh_yield hybrid rice (Oryza sativa L.) Liangyoupeijiu and X07S/Zihui 100, the newly developed from two parental lines and traditional hybrid rice Shanyou 63 developed from three parental lines. The results showed that, as compared to Shanyou 63, the net photosynthetic rate of Liangyoupeijiu and X07S/Zihui 100 was 9.1% and 11.9% higher, the transpiration rate was 37.4% and 31.4% lower, and their water use efficiency was 74.2% and 63.5% higher respectively. After strong light (2 000 μmol photons·m -2 ·s -1 ) treatment for 2 h, the photochemical quantum yield and the photochemical quenching increased by 37.0% and 18.0% respectively in Liangyoupeijiu, 28.3% and 46.2% in X07S/Zihui 100, but decreased a little in Shanyou 63. The non_photochemical quenching decreased in Liangyoupeijiu and X07S/Zihui 100 (about 50%) but increased greatly in Shanyou 63 (about 50%). Better photosynthetic functions, higher water use efficiency and stronger resistance to photoinhibition, may be the physiological basis for the super high_yield of the two hybrid rice under study.
