Kinetics and Thermodynamic Parameters of the CopperExchange on Na-montmorillonite Clay Mineral inSelected Solvents

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.

Kinetics studies of nano-structured iron catalyst in Fischer-Tropsch synthesis

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.

Influence of ammonium sulfate on the corrosion behavior of AZ31 magnesium alloy in chloride environment

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.

Effect of surface dissolution on kinetic parameters in flotation of ilmenite from different gangue minerals

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.

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.

Comparison of Seven Kinetic Equations for K Release and Application of Kinetic Parameters

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.

Reduction behavior and kinetics of vanadium–titanium sinters under high potential oxygen enriched pulverized coal injection

In this work, the reduction behavior of vanadium–titanium sinters was studied under five different sets of conditions of pulverized coal injection with oxygen enrichment. The modified random pore model was established to analyze the reduction kinetics. The results show that the reduction rate of sinters was accelerated by an increase of CO and H2contents. Meanwhile, with the increase in CO and H2contents, the increasing range of the medium reduction index (MRE) of sinters decreased. The increasing oxygen enrichment ratio played a diminishing role in improving the reduction behavior of the sinters. The reducing process kinetic parameters were solved using the modified random role model. The results indicated that, with increasing oxygen enrichment, the contents of CO and H2in the reducing gas increased. The reduction activation energy of the sinters decreased to between 20.4 and 23.2 kJ/mol. © 2017, The Author(s).

Kinetics of celestite conversion to acidic strontium oxalate hydrate in aqueous solution of oxalic acid

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.

Determination of Kinetic Parameters and Metal Ions in Urea-Urease System Based on the Biochemical Reaction Heat Induced Laser Beam Deflection

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.

CHRONOABSORPTOMETRY FOR THE DETERMINATION OF KINETIC PARAMETERS OF ELECTRON TRANSFER REACTIONS USING LONG-OPTICAL-PATH ELECTROCHEMICAL CELL

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

Growth Kinetics Study of a Bacterial Consortium Producing Biosurfactants,Constructed with Six Strains Isolated from an Oily Sludge

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.

Dose-Dependence of Trap Parameters of OSL Decay from Al_(2)O_(3):C

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.

Multi-time scale identification of key kinetic processes for lithium-ion batteries considering variable characteristic frequency

The electrification of vehicles puts forward higher requirements for the power management efficiency of integrated battery management systems as the primary or sole energy supply.In this paper,an efficient adaptive multi-time scale identification strategy is proposed to achieve high-fidelity modeling of complex kinetic processes inside the battery.More specifically,a second-order equivalent circuit model network considering variable characteristic frequency is constructed based on the high-frequency,medium-high-frequency,and low-frequency characteristics of the key kinetic processes.Then,two coupled sub-filters are developed based on forgetting factor recursive least squares and extended Kalman filtering methods and decoupled by the corresponding time-scale information.The coupled iterative calculation of the two sub-filter modules at different time scales is realized by the voltage response of the kinetic diffusion process.In addition,the driver of the low-frequency subalgorithm with the state of charge variation amount as the kernel is designed to realize the adaptive identification of the kinetic diffusion process parameters.Finally,the concept of dynamical parameter entropy is introduced and advocated to verify the physical meaning of the kinetic parameters.The experimental results under three operating conditions show that the mean absolute error and root-mean-square error metrics of the proposed strategy for voltage tracking can be limited to 13 and 16 mV,respectively.Additionally,from the entropy calculation results,the proposed method can reduce the dispersion of parameter identification results by a maximum of 40.72%and 70.05%,respectively,compared with the traditional fixed characteristic frequency algorithms.The proposed method paves the way for the subsequent development of adaptive state estimators and efficient embedded applications.

Effect of acid-associated mechanical pretreatment on the hydrolysis behavior of pine sawdust in subcritical water

The effects of sulfuric acid-associated mechanical pretreatment on the hydrolysis behavior of pine sawdust were investigated in this study.Sulfuric acid could act as an acidic catalyst to depolymerize holocellulose through cleavage of the glycosidic bonds,the dissociation energies of which were supplied by the impact of a ball on pine sawdust,during milling.The destruction of glycosidic and hydrogen bonds in pine sawdust resulted in a decrease of crystallinity and an increase of water solubility.The sulfuric acid could promote the hydrolysis of holocellulose and its hydrolysis products.It also destroyed the chemical linkages between holocellulose and lignin during ball milling.The cleavage of chemical linkages with holocellulose made lignin more difficult to hydrolyze in subcritical water,and higher activation energy was needed to hydrolyze pretreated pine sawdust at higher reaction temperatures.It also led to the formation of glucose char and aromatic-linked polymer char from the hydrolysis products of holocellulose.

Photosynthetic Characteristics of Two Superhigh-yield Hybrid Rice

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.

Effect of Heat Stress on Photosynthetic Characteristics of Different Green Organs of Winter Wheat During Grain-filling Stage

Four winter wheat (Triticum aestivum L.) varieties ('JD 8', 'Jing 411','Centurk' and 'Tam 202') were used to study the effect of heat stress on photosynthetic characteristics of flag leaf blade, nag leaf sheath, peduncle, glume, lemma and awn during grain-filling stage. The results showed that heat acclimation during grain-filling stage increased thermotolerance of wheat with significant differences among different green organs. During heat stress, the decreases of the efficiency of primary light energy conversion (F-v/F-m) of PS II and pigment (chlorophyll and carotenoid) content were much slower in peduncle, flag leaf sheath and glume than in nag leaf blade, lemma and ann; and the percentage of decrease in net photosynthetic rate (P-n) of ear was lower than that of the nag leaf blade. The measured photosynthetic parameters (F-v/F-m, P-n and pigment content) of 'JD 8', a relatively heat tolerant variety, declined more slowly than those of the other three varieties during the whole heat stress period.

Dynamic Effects of PAEs on Soil Urease and Phosphatase

[Object] The study aimed to supply a reference for evaluating ecotoxicology of soil contaminated with phthalate acid esters(PAEs).[Method] The dynamic effects of DBP and DEHP on activities and kinetics parameters of urease and phosphatase in agro-soil contaminated artificially with DBP and DEHP were studied.[Result] The activities of urease and phosphatase were both inhibited significantly by higher contents of DBP and DEHP in soils compared with CK.The inhabitations increased with increasing DBP and DEHP c...

Full-scale application of microbial agent on in-situ sludge reduction

The full-scale application of Tx-1, a multifunctional microbial agent, was carried out for 8 months in an anoxic/oxic（A/O） municipal wastewater treatment process. The results show that the Tx-1 dosed system can obtain good effluent characteristics while minimizing sludge production and energy consumption. The total phosphorus（TP） is lower than0. 5 mg/L in effluent without any chemical regent added. The discharged dry sludge per 10 000 m^3 wastewater Dwat decreases from 1. 4 to 0. 5 t. For per cubic meter wastewater, the air supply decreases from 6. 0 to 5. 1 m^3 and the electricity consumption decreases from 0. 412- 0. 425 kW·h to 0. 331 kW·h. The addition of Tx-1 can improve the substrate removal constant and decrease the microorganism growth yield coefficient of activated sludge. At the same time,the structure of the microbial community changes and the biodiversity increases by adding Tx-1. The abundance of polyphosphate accumulating organisms（PAO）, Comamonadaceae and Tetrasphaera, increased. Effective microbial agent is a potential way to combine in-situ sludge minimization with contaminants removal.

STUDY ON CO-CURING REACTION IN CHAIN-PROLONGED BISMALEIMIDE-UNSATURATED POLYMER RESIN SYSTEM

The curing proces of chemical reactombetween flexible unsaturated polymer resin and diphenyl-methane bismaleimides which have been chain-prolonged by diaminodiphenylmethane is presented. also the kinetics parameters and curing technology are investigated.

An evaluation equation of TG experiment data based on iso-conversion method for activation energy

The iso-conversion method to could calculate the kinetics parameters effectively, the present paper built an evaluation equation for iso-conversion methods according to the thermo kinetics integral equation and analyses the temperatures of the same degree of conversion for different heating rates by ideal TG （thermo-gravity） curve data. It is obtained that the temperatures of the same degree of conversion for different heating rates＇ TG curve have good linearity connection validating the correction of the evaluation equation for iso-conversion methods and the scope of linear slope for theratio between heating rates being 2 is 1.05 to 1.09.