Values Of Reaction Rate Constants Research Articles

Dimethyl carbonate synthesis by transesterification of propylene carbonate with methanol: Comparative assessment of Ce-M (M=Co, Fe, Cu and Zn) catalysts

In this work, Ce–M catalysts (M = Co, Fe, Cu and Zn) synthesized by sol-gel method and characterized by various techniques have been evaluated for the transesterification of propylene carbonate (PC) with methanol for dimethyl carbonate (DMC) synthesis in a batch reactor. The catalysts were characterized by various techniques such as X-ray diffraction (XRD), N2-sorption analysis, scanning electron microscope (SEM-EDX) etc. Total basicity of CeCo, CeCu, CeZn and CeFe catalysts were 0.083, 0.698, 0.424 and 0.492 mmol/g with crystalline sizes found to be 19.4, 18.8, 9.6 and 21.6 nm, respectively. Best performing catalyst CeCu was further used for optimization of operating conditions such as methanol/PC molar ratio, catalysts dose, reaction time, reaction temperature and kinetics study. The reaction rate constant values as obtained using non-linear regression analysis were found to be 0.285, 0.570 1.255 and 1.596 h−1 at 120, 140, 160 and 180 °C, respectively for the CeCu catalyst. Reusability of the catalyst was studied in terms of PC conversion and turn over frequency.

Degradation of Herbicide Mesotrione in Three Soils with Differing Physicochemical Properties from China.

The movement and fate of herbicides in soils under various environmental factors are important in evaluating their mobility and ecological impact. The effects of sterilization, solarization, and soil physicochemical properties on the degradation of herbicide mesotrione in three soils from China were evaluated using laboratory incubation method, and the degradation kinetics were also simulated using pseudo first-order reaction model. The calculated half-lives () of mesotrione were found to be 3.78- to 5.24-fold increased in sterilized soils than nonsterilized soils, which indicated that the degradation of mesotrione was strongly affected by soil microbial activity. A certain role of promoting degradation effect of natural light was found, and the values appeared to be only 7.90, 15.89, and 25.29 d in the surface of paddy soil, sandy loess, and silt clay loam, respectively. Correlation analysis between the observed first-order reaction rate constant () values and the selected soil properties revealed that the degradation of mesotrione was highly dependent on soil pH value ( > 0.992) and organic matter content ( > 0.932), but less related with clay content (<0.02 mm) with < 0.761 and nonrelated with cation exchange capacity (CEC) ( < 0.164). Data obtained in this study are helpful for further research on the prediction of the movement and fate of mesotrione in soils in limiting its environmental impact.

Enzymolysis kinetics, thermodynamics and model of porcine cerebral protein with single-frequency countercurrent and pulsed ultrasound-assisted processing

The present work investigated the enzymolysis kinetics, thermodynamics and model of porcine cerebral protein (PCP) which was pretreated by single-frequency countercurrent and pulsed ultrasound. The kinetic constants for ultrasonic pretreated and traditional enzymolysis have been determined. Results showed that the value of KM in ultrasonic PCP (UPCP) enzymolysis decreased by 9% over that in the traditional enzymolysis. The values of reaction rate constant (k) for UPCP enzymolysis increased by 207%, 121%, 62%, and 45% at 293, 303, 313 and 323K, respectively. For the thermodynamic parameters, ultrasound decreased activation energy (Ea), change in enthalpy (ΔH) and entropy (ΔS) by 76%, 82% and 31% in PCP, respectively. However, ultrasound had little change in Gibbs free energy (ΔG) value in the temperature range of 293–323K. Therefore, a general kinetic equation for the enzymolysis model of UPCP by a simple empirical equation was suggested. The experimental values fits with the enzymolysis kinetic model with a low average relative error (4%) confirmed that the kinetic model was accurate to reflect the enzymolysis process. The positive effect of single-frequency countercurrent and pulsed ultrasound in this study and application of the kinetic model may be useful for the release of bioactive peptides from meat processing by-products.

Differential scanning calorimetry study—Assessing the influence of composition of vegetable oils on oxidation

The thermal oxidation of eight different vegetable oils was studied using differential scanning calorimetry (DSC) under non-isothermal conditions at five different heating rates (5, 7.5, 10, 12.5, and 15°C/min), in a temperature range of 100–400°C. For all oils, the activation energy (Ea) values at Tp were smaller than that at Ts and Ton. Among all the oils, refined palm oil (RPO) exhibited the highest Ea values, 126.06kJ/mol at Ts, 134.7kJ/mol at Ton, and 91.88kJ/mol at Tp. The Ea and reaction rate constant (k) values at Ts, Ton, and Tp were further correlated with oil compositions (fatty acids and triacylglycerols) using Pearson correlation analysis. The rate constant (k) and Ea of all oils exhibited varying correlations with FAs and TAGs, indicating that the thermal oxidation behaviors were affected by oil compositions.

Electrochemical Model for Ionic Liquid Electrolytes in Lithium Batteries

ABSTRACT Room temperature ionic liquids are considered as potential electrolytes for high performance and safe lithium batteries due to their very low vapor pressure and relatively wide electrochemical and thermal stability windows. Unlike organic electrolytes, ionic liquid electrolytes are molten salts at room temperature with dissociated cations and anions. These dissociated ions interfere with the transport of lithium ions in lithium battery. In this study, a mathematical model is developed for transport of ionic components to study the performance of ionic liquid based lithium batteries. The mathematical model is based on a univalent ternary electrolyte frequently encountered in ionic liquid electrolytes of lithium batteries. Owing to the very high concentration of components in ionic liquid, the transport of lithium ions is described by the mutual diffusion phenomena using Maxwell-Stefan diffusivities, which are obtained from atomistic simulation. The model is employed to study a lithium-ion battery where the electrolyte comprises ionic liquid with mppy + (N-methyl-N-propyl pyrrolidinium) cation and TFSI − (bis trifluoromethanesulfonyl imide) anion. For a moderate value of reaction rate constant, the electric performance results predicted by the model are in good agreement with experimental data. We also studied the effect of porosity and thickness of separator on the performance of lithium-ion battery using this model. Numerical results indicate that low rate of lithium ion transport causes lithium depleted zone in the porous cathode regions as the porosity decreases or the length of the separator increases. The lithium depleted region is responsible for lower specific capacity in lithium-ion cells. The model presented in this study can be used for design of optimal ionic liquid electrolytes for lithium-ion and lithium-air batteries.

Application of dhurrin for kinetics and thermodynamic characterization of linamarase (β-glucosidase) genetically engineered from Saccharomyces cerevisiae.

Recombinant Saccharomyces cerevisiae cells at the stationary phase of growth were recovered, homogenized and centrifuged to obtain crude extracts designated as GELIN 0 . Carboxy methyl cellulose, diethyl amino-ethyl-sephadex and diethyl amino-ethyl-cellulose were used to purify the crude extracts of GELIN 0 resulting in GELIN 1 , GELIN 2 and GELIN 3 , respectively. The ability of the enzyme extracts and a commercial native linamarase (CNLIN) to hydrolyse cyanogenic glucosides was challenged using dhurrin from sorghum as substrate. Precisely, the actions of commercial native linamarase (CNLIN) and the genetically engineered linamarase (β-glucosidase) from Saccharomyces cerevisiae on dhurrin as influenced by degree of its purification, pH (6.8 ) and temperature(30-45°C) were investigated and the data derived were applied for kinetics and thermodynamic characterization of the enzymes. Enzymic degradation kinetics of the dhurrin were evaluated using a 4 x 6 x 8 B/W design comprising of 4 enzyme types ( GELIN o , GELIN 1 GELIN 2 and GELIN 3 ,, 6 temperatures (30, 32, 35, 37, 40, 45 °C) and 8 time intervals( 0-70 min.). Data obtained from the residual HCN with time were fitted into zero, first and second order kinetics models to derive reaction rate constant (Kmin -1 ) values which were analyzed using the Arrhenius and absolute reaction rate models Thermodynamic parameters were obtained including; activation energies (E a ), frequency factor(K o ), enthalpy (ΔH ) and entropy (ΔS#) that characterized the reactions on dhurrin catalyzed by commercial native linamarase (CNLIN) and the genetically engineered linamarase (β-glucosidase) from Saccharomyces cerevisiae. The results showed that the best fitted order based on higher coefficient of linear regression (r 2 ) values > 0.998 and linearity of curves was the first order kinetics model and not either zero or second order models. Kmin -1 values ranged from GELIN O- GELIN 3 0.03-0.07 μmol/min while the derived D-values from K-values were in the range of 24-65 min. The frequency factors (K o ) increased with enzyme purity from GELIN 0 to GELIN 3 corresponding to K o (min -1 ) of 22.585 to 56.462. The energy of activation E a (KJ/mol)generated 60.0995 to 150.6900 corresponding to enzymes GELIN 0 to GELIN 3 followed the same pattern with frequency factor for breaking of bonds in dhurrin molecules. At pH 6.8 CNLIN showed no action on dhurrin. The high correlation coefficient values of (r 2 = 0.97 to 0.99) indicated the best fit of the Arrhenius and the absolute reaction rate models. The entropy change (ΔS) increased with enzyme purity from 0.588 J/mol.deg. to 1.4625Jmol degree. The enthalpy change KJ/mol followed the same pattern whereby increases influenced by enzyme purity ranged from 1892 KJ/mol to 13104KJ/mol. Keywords : kinetics, thermodynamic, characterization, dhurrin, genetically engineered β- glucosidase, Saccharomyces cerevisiae.

Axial ligands and (acido) (phthalocyaninato) lanthanides(III) stability on examples of erbium and lutetium

The results of a spectrophotometric study of the dissociation kinetics of the coordination centre in (phthalocyaninato) erbium(III) and lutetium(II), (X)LnPc (X = Cl, Br, AcO) in ethanol in the presence of acetic acid are reported. The kinetic equations, the numerical values of reaction rate constants and dependences of the letter on the temperature were determined by the method of excessive concentrations. The stoichiometric mechanism of the complexes dissociation and the nature of the limiting elementary reaction were substantiated and the role of axial ligands in the reaction mechanism was revealed using spectral data and the quasiequilibrium principle to describe kinetic regularities. The resulting data can help in the use of erbium and lutetium phthalocyanines as precursors in the synthesis of higher stoichiometry complexes.

Para-hydrogen and helium cluster size distributions in free jet expansions based on Smoluchowski theory with kernel scaling

The size distribution of para-H2 (pH2) clusters produced in free jet expansions at a source temperature of T0 = 29.5 K and pressures of P0 = 0.9-1.96 bars is reported and analyzed according to a cluster growth model based on the Smoluchowski theory with kernel scaling. Good overall agreement is found between the measured and predicted, Nk = A k(a) e(-bk), shape of the distribution. The fit yields values for A and b for values of a derived from simple collision models. The small remaining deviations between measured abundances and theory imply a (pH2)k magic number cluster of k = 13 as has been observed previously by Raman spectroscopy. The predicted linear dependence of b(-(a+1)) on source gas pressure was verified and used to determine the value of the basic effective agglomeration reaction rate constant. A comparison of the corresponding effective growth cross sections σ11 with results from a similar analysis of He cluster size distributions indicates that the latter are much larger by a factor 6-10. An analysis of the three body recombination rates, the geometric sizes and the fact that the He clusters are liquid independent of their size can explain the larger cross sections found for He.

Fluorescence spectroscopy of UV-MALDI matrices and implications of ionization mechanisms.

Matrix-assisted laser desorption ionization (MALDI) has been widely used in the mass analysis of biomolecules; however, there are a lot of debates about the ionization mechanisms. Previous studies have indicated that S1-S1 annihilation might be a key process in the generation of primary ions. This study investigates S1-S1 annihilation by examining the time-resolved fluorescence spectra of 12 matrices. No S1-S1 annihilation was observed in six of these matrices (3-hydroxy-picolinic acid, 6-aza-2-thiothymine, 2,4-dihydroxy-acetophenone, 2,6-dihydroxy-acetophenone, 2,4,6-trihydroxy-acetophenone, and ferulic acid). We observed two matrix molecules reacting in an electronically excited state (S1) in five of these matrices (2,5-dihydroxybenzoic acid, α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxy-acetophenone, 2,3-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid), and S1-S1 annihilation was a possible reaction. Among these five matrices, no S1-S1 annihilation was observed for 2,3-dihydroxybenzoic acid in typical peak power region of nanosecond laser pulses in MALDI, but a very small value of reaction rate constant was observed only in the high peak power region. The excited-state lifetime of sinapinic acid was too short to determine whether the molecules reacted in an electronically excited state. No correlation was observed between the ion generation efficiency of MALDI and S1-S1 annihilation. The results indicate that the proposal of S1-S1 annihilation is unnecessary in MALDI and energy pooling model for MALDI ionization mechanism has to be modified.

Performance and kinetic study of semi-dry thermophilic anaerobic digestion of organic fraction of municipal solid waste

Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) is promoted as an energy source and waste disposal. In this study semi dry anaerobic digestion of organic solid wastes was conducted for 45days in a lab-scale batch experiment for total solid concentration of 100g/L for investigating the start-up performances under thermophilic condition (50°C). The performance of the reactor was evaluated by measuring the daily biogas production and calculating the degradation of total solids and the total volatile solids. The biogas yield at the end of the digestion was 52.9L/kg VS (volatile solid) for the total solid (TS) concentration of 100g/L. About 66.7% of the volatile solid degradation was obtained during the digestion. A first order model based on the availability of substrate as the limiting factor was used to perform the kinetic studies of batch anaerobic digestion system. The value of reaction rate constant, k, obtained was 0.0249day−1.

Alkylating potential of styrene oxide: reactions and factors involved in the alkylation process.

The chemical reactivity of styrene-7,8-oxide (SO), an alkylating agent with high affinity for the guanine–N7 position and a probable carcinogen for humans, with 4-(p-nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilic characteristics similar to those of DNA bases, was investigated kinetically in water/dioxane media. UV–vis spectrophotometry and ultrafast liquid chromatography were used to monitor the reactions involved. It was found that in the alkylation process four reactions occur simultaneously: (a) the formation of a β-NBP–SO adduct through an SN2 mechanism; (b) the acid-catalyzed formation of the stable α-NBP–SO adduct through an SN2′ mechanism; (c) the base-catalyzed hydrolysis of the β-adduct, and (d) the acid-catalyzed hydrolysis of SO. At 37.5 °C and pH = 7.0 (in 7:3 water/dioxane medium), the values of the respective reaction rate constants were as follows: kalkβ = (2.1 ± 0.3) × 10–4 M–1 s–1, kalkα = (1.0 ± 0.1) × 10–4 M–1 s–1, khydAD = (3.06 ± 0.09) × 10–6 s–1, and khyd = (4.2 ± 0.9) × 10–6 s–1. These values show that, in order to determine the alkylating potential of SO, none of the four reactions involved can be neglected. Temperature and pH were found to exert a strong influence on the values of some parameters that may be useful to investigate possible chemicobiological correlations (e.g., in the pH 5.81–7.69 range, the fraction of total adducts formed increased from 24% to 90% of the initial SO, whereas the adduct lifetime of the unstable β-adduct, which gives an idea of the permanence of the adduct over time, decreased from 32358 to 13313 min). A consequence of these results is that the conclusions drawn in studies addressing alkylation reactions at temperatures and/or pH far from those of biological conditions should be considered with some reserve.

Leaching Kinetics of Atrazine and Inorganic Chemicals in Tilled and Orchard Soils

Abstract The aim of this study was to verify first-order kinetic reaction rate model performance in predicting of leaching of atrazine and inorganic compounds (K+1, Fe+3, Mg+2, Mn+2, NH4 +, NO3 - and PO4 -3) from tilled and orchard silty loam soils. This model provided an excellent fit to the experimental concentration changes of the compounds vs. time data during leaching. Calculated values of the first-order reaction rate constants for the changes of all chemicals were from 3.8 to 19.0 times higher in orchard than in tilled soil. Higher first-order reaction constants for orchard than tilled soil correspond with both higher total porosity and contribution of biological pores in the former. The first order reaction constants for the leaching of chemical compounds enables prediction of the actual compound concentration and the interactions between compound and soil as affected by management system. The study demonstrates the effectiveness of simultaneous chemical and physical analyses as a tool for the understanding of leaching in variously managed soils.

Anoxic microniches in marine sediments induced by aggregate settlement: biogeochemical dynamics and implications

Spherical (~2 mm diameter) diatom (Skeletonema sp.) aggregates, representing analogues of “marine snow”, were placed at the sediment–water interface of an experimental sediment system. Optode measurements showed that, after an initial lag period, oxygen concentrations within the aggregates decreased and then were gradually replenished, resulting in a temporary anoxic microniche. A multi-species, 3-dimensional, reactive transport model was used to simulate the oxygen dynamics and the associated biogeochemical consequences. Temporal and spatial changes in oxygen were replicated assuming an exponential increase in the mineralisation rate constant and a gradual exhaustion of reactive organic material. The peak value of the time-dependent reaction rate constant of organic matter mineralisation (kOMM) was seven to sixty times greater than analogous values measured previously in water column experiments. The validated model was used to investigate how the size and reactivity of parcels of organic matter influence the formation of anoxic microniches at the sediment–water interface of typical deep-sea environments. As well as kOMM, the concentration of reactive organic matter in the aggregate, its size and porosity were also critical in determining the likelihood of anoxic microniche formation. For the optimum fitted parameters describing kOMM and the concentration of reactive organic matter, the minimum diameter of the parcel to induce anoxia was 1.8 mm, whereas it was 2.8 mm to make a significant contribution to the denitrification occurring in a typical deep-sea sediment. This work suggests that anoxic microniches resulting from the settlement of marine aggregates may play an overlooked role for denitrification activities in deep-sea sediments.

The combined effect of bacteria and Chlorella vulgaris on the treatment of municipal wastewaters

Impacts of Chlorella vulgaris with or without co-existing bacteria on the removal of nitrogen, phosphorus and organic matter from wastewaters were studied by comparing the wastewater treatment effects between an algae-bacteria consortium and a stand-alone algae system. In the algae-bacteria system, C.vulgaris played a dominant role in the removal of nitrogen and phosphorus, while bacteria removed most of the organic matter from the wastewater. When treating unsterilized wastewater, bacteria were found to inhibit the growth of algae at >231 mg/L dissolved organic carbon (DOC). Using the algae-bacteria consortium resulted in the removal of 97% NH4(+), 98% phosphorus and 26% DOC at a total nitrogen (TN) level of 29-174 mg/L. The reaction rate constant (k) values in sterilized and unsterilized wastewaters were 2.17 and 1.92 mg NH4(+)-N/(mg algal cell ·d), respectively.

Kinetics Approach of Biodegradation of Petroleum Contaminated Soil by using Indigenous Isolated Bacteria

The bioremediation of petroleum contaminated soil was investigated using a microscale Landfarming. The Indigenousbacteria, Pseudomonas pseudoalcaligenes, Bacillus megaterium, and Xanthobacter autotrophicus were isolated from the contaminated sites Sungai Lilin Jambi Pertamina Ltd and used further in the bioremediation experiments. The biodegradation rates of petroleum contaminated soil in the presence of the isolated bacteria were studied by using the chemical kinetics approach. The reaction orders were studied by using the differential method and the reaction rate constants were studied by using the integral method. The results showed that the reaction orders were 1.0949, 1.3985, 0.8823, and the reaction rate constants were 0.0189, 0.0204, 0.0324 day-1, respectively. Considering the values of reaction orders and reaction rate constants, the biodegradation rate of contaminated soil by usingeach bacteria had significantly different value; Xanthobacter Autotrophicus bacteria could degrade the petroleumoil sludge fastest than the others.Keywords: Biodegradation, indigenous bacteria, kinetics, petroleum oil

Production enhancement of 5‐hydroxymethyl furfural from fructose via mechanical stirring control and high‐fructose solution addition

AbstractBACKGROUND5‐hydroxymethylfurfural (HMF) has attracted increasing attention so that an efficient process for HMF production from high‐sugar solution is needed for the successful commercialization of this versatile intermediate in the production of high value chemicals.RESULTSTwo simple operations, mechanical stirring control and high‐fructose solution addition, were applied to the water/butanol system for enhancing fructose‐to‐HMF reaction using HCl as catalyst. The optimization of stirring speed led to a high HMF yield of 81.7% with 92.0% fructose conversion (0.3 moL L−1 HCl, 1000 rpm). Moreover, a reasonable mechanism describing the effect of stirring speed on HMF yield was proposed. During the process of high‐fructose solution (54.6 wt%) addition, the yields of HMF after four additions in every experiment all exceeded 55%, and a HMF yield of 83.3% was achieved after three additions at 1000 rpm.CONCLUSIONSThe optimization of mechanical stirring in aqueous/butanol media led to a high HMF yield. By studying the kinetics of the fructose‐to‐HMF reaction, it was demonstrated that a low value of reaction rate constant is of benefit to obtain high HMF yield for this biphasic system. The simple addition process greatly reduced the side‐reaction and made the operation more continuous and stable, and thus provided a practical and effective method of HMF preparation in high‐fructose solution. © 2013 Society of Chemical Industry

Reversible immobilization of invertase on Cu-chelated polyvinylimidazole-grafted iron oxide nanoparticles

Polyvinylimidazole (PVI)-grafted iron oxide nanoparticles (PVIgMNP) were prepared by grafting of telomere of PVI on the iron oxide nanoparticles. Different metal ions (Cu(2+), Zn(2+), Cr(2+), Ni(2+)) ions were chelated on polyvinylimidazole-grafted iron oxide nanoparticles, and then the metal-chelated magnetic particles were used in the adsorption of invertase. The maximum invertase immobilization capacity of the PVIgMNP-Cu(2+) beads was observed to be 142.856mg/g (invertase/PVIgMNP) at pH 5.0. The values of the maximum reaction rate (V max) and Michaelis-Menten constant (Km) were determined for the free and immobilized enzymes. The enzyme adsorption-desorption studies, pH effect on the adsorption efficiency, affinity of different metal ions, the kinetic parameters and storage stability of free and immobilized enzymes were evaluated.

Sacrificial Hydrogen Generation from Formaldehyde with Pt/TiO2 Photocatalyst in Solar Radiation

In this work, solar TiO2 photocatalysis was used for sacrificial hydrogen generation from formaldehyde. Platinum was loaded onto a TiO2 photocatalyst by a solar photodeposition method to suppress the electron/hole recombination process. The photocatalyst inside the reactor was irradiated from the top with a solar simulator. Photocatalytic hydrogen generation from formaldehyde was influenced by the solution pH, platinum loading (wt %) on TiO2, catalyst concentration, light intensity, and initial formaldehyde concentration. A Langmuir-type model fitted well with the experimental data, and the values of surface reaction rate constant, k, and the adsorption equilibrium constant, K, are 2.3598 × 10–6 mol min–1 and 17.73 M–1, respectively. Apparent quantum yield (QY) was higher for the UV light-driven hydrogen generation (10.91%) compared to the solar light-driven hydrogen generation (1.24%).

A note on the reverse Michaelis–Menten kinetics

We theoretically derived a general equation describing the enzyme kinetics that could be further simplified to the typical Michaelis–Menten (M–M) kinetics or the reverse M–M equation (RM–M) under the condition of S ≈ S1 >> E0 or S1 << E0, respectively, where E0 and S1 (=S + ES) are the concentrations of total enzyme and substrate including free substrate (S) and enzyme–substrate complex (ES). We showed that the related Schimel and Weintraub RM–M equation (RM–M–SW) can be derived from the Langmuir adsorption isotherm theory with S >> E0. Both the M–M and the RM-M-SW are appropriate to field soil conditions with S >> E0 given different values of specific reaction rate (k3) and half-saturation constant (Ks). In contrast to M–M and RM–M–SW models, the RM–M model is not applicable to field conditions because of its limited application to one substrate with a simple enzyme system. However, we demonstrate that the best formulation for the process of enzyme-mediated decomposition may vary depending on whether the process is limited by substrate or enzyme availability.

Modeling calcium and water intake in threshed corn grain during thermo-alkaline treatment

A mathematical model describing simultaneous solvent diffusion and gelatinization of starch was used to explain the water and calcium absorption in threshed corn grains during the thermo-alkaline treatment. A computer-aided nonlinear optimization technique was used to find the effective diffusion coefficients and the reaction rate constants of water and calcium in threshed corn grains at boiling temperature (92.5±0.3°C). The mathematical model shows good correlation between measured and predicted values of water and calcium intake. It is concluded that the cooking process is limited by the reaction of starch components with water and calcium. The effective diffusion coefficient for water varied between 1.18×10−10 and 1.45×10−10m2/s and for calcium between 8.55×10−10and 16.77×10−10m2/s. The diffusion of water and calcium in threshed corn was produced with a reaction rate constants in the range of 6.83×10−4 to 10.4×10−4s−1 for water and 2.7×10−5–7.6×10−5s−1 for calcium. According to these effective diffusion coefficient values the diffusive process seems to be slower for water than for calcium. However, the reaction rate constant values are approximately 10 times higher for water than for calcium which may indicate that a higher amount of solvent was linked in the water diffusion process due to the gelatinization. Low concentration of Ca(OH)2 such as 0.10% did not significantly affect the water diffusion of threshed corn during the cooking process.