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Sample records for acid components kinetics

  1. Kinetic analysis of the reactions of hypobromous acid with protein components

    Pattison, David I; Davies, Michael Jonathan

    2004-01-01

    proteins isolated from patients with atherosclerosis, asthma, and cystic fibrosis, implicating the production of HOX in these diseases. The quantitative significance of these findings requires knowledge of the kinetics of reaction of HOX with protein targets, and such data have not been previously...... more, and Cys and Met much less, important targets for HOBr than HOCl. Kinetic models have been developed to predict the targets of HOX attack on proteins and free amino acids. Overall, these results shed light on the mechanisms of cell damage induced by HOX and indicate, for example, that the 3-chloro...

  2. Radiomimeticity of the system H2O2/Fe(II) on nucleic acid components. Kinetics study

    The kinetic study of the action of a redox system on DNA monomers allowed us to make criticisms on radiomimetic character of this system. Assuming that in both cases, gamma radiolysis of aerated aqueous solutions and action of H2O2 / Fe(II) system in the same conditions, the reactive species is the OH radical, we propose the kinetic expressions that are confirmed by our experimental results. Some of the accepted G-values are corrected in view of our results. Al so these results put in evidence mechanisms of molecular repair after radical attack. (Author) 79 refs

  3. Synergistic role of different soil components in slow sorption kinetics of polar organic contaminants

    We observed that the sorption kinetics of nitrobenzene and 2,4-dinitrotoluene (two model polar compounds) was significantly slower than that of 1,4-dichlorobenzene and phenanthrene (two model apolar compounds). The difference was attributable to the strong non-hydrophobic interactions between the polar molecules and soil. Interestingly, sorption kinetics of the polar sorbates to the soil organic matter-free soil, humic/fulvic acid-free soil, and extracted humic acids was very fast, indicating that different soil components played a synergetic role in the observed slow kinetics. We propose that slow sorption kinetics of highly polar sorbates stems mainly from the strong specific interactions (H-bonding, electron donor–acceptor interactions, etc.) with humic/fulvic acids; such specific interactions occur when sorbate molecules diffuse through humic/fulvic acids coiled, in relatively compressed confirmations, within the complex, tortuous, and porous soil matrices formed by mineral grains/particles and soil organic matter. -- Highlights: • Polar sorbates exhibit much slower sorption kinetics to soil than apolar sorbates. • Slow sorption is not from sorptive interaction with any single soil component. • Polar interactions with humic/fulvic acids coiled in soil matrices hinder sorption. • Humin/minerals contribute to slow sorption by forming tortuous, porous network. -- Slow sorption kinetics of polar organic contaminants is a result of synergistic contribution from different soil components

  4. On the kinetic theory of the one-component plasma

    In this thesis, kinetic theory is applied to transport phenomena of a one-component plasma. Existing kinetic equations, containing both dynamical screening effects and close binary collisions do not suffer from divergencies. Recently an approximation for the pair correlation function has been proposed that is valid for small values of the plasma collision parameter. Upon insertion of this expression into the general form of the collision integral, one obtains another convergent kinetic equation. This thesis shows that both kinetic equations yield the same coefficient of heat conductivity and viscosity; and that for a hot dilute plasma the arbitrary transport coefficient is rather insensitive to the pair correlation function. In the second part, the author studies the diffusion of a tagged particle in an external magnetic field. It is found that the longitudinal self-diffusion coefficient contra-varies monotonically with the magnetic field strength. (Auth.)

  5. Kinetic Modeling of Sunflower Grain Filling and Fatty Acid Biosynthesis.

    Durruty, Ignacio; Aguirrezábal, Luis A N; Echarte, María M

    2016-01-01

    Grain growth and oil biosynthesis are complex processes that involve various enzymes placed in different sub-cellular compartments of the grain. In order to understand the mechanisms controlling grain weight and composition, we need mathematical models capable of simulating the dynamic behavior of the main components of the grain during the grain filling stage. In this paper, we present a non-structured mechanistic kinetic model developed for sunflower grains. The model was first calibrated for sunflower hybrid ACA855. The calibrated model was able to predict the theoretical amount of carbohydrate equivalents allocated to the grain, grain growth and the dynamics of the oil and non-oil fraction, while considering maintenance requirements and leaf senescence. Incorporating into the model the serial-parallel nature of fatty acid biosynthesis permitted a good representation of the kinetics of palmitic, stearic, oleic, and linoleic acids production. A sensitivity analysis showed that the relative influence of input parameters changed along grain development. Grain growth was mostly affected by the specific growth parameter (μ') while fatty acid composition strongly depended on their own maximum specific rate parameters. The model was successfully applied to two additional hybrids (MG2 and DK3820). The proposed model can be the first building block toward the development of a more sophisticated model, capable of predicting the effects of environmental conditions on grain weight and composition, in a comprehensive and quantitative way. PMID:27242809

  6. Kinetic Modeling of Sunflower Grain Filling and Fatty Acid Biosynthesis

    Durruty, Ignacio; Aguirrezábal, Luis A. N.; Echarte, María M.

    2016-01-01

    Grain growth and oil biosynthesis are complex processes that involve various enzymes placed in different sub-cellular compartments of the grain. In order to understand the mechanisms controlling grain weight and composition, we need mathematical models capable of simulating the dynamic behavior of the main components of the grain during the grain filling stage. In this paper, we present a non-structured mechanistic kinetic model developed for sunflower grains. The model was first calibrated for sunflower hybrid ACA855. The calibrated model was able to predict the theoretical amount of carbohydrate equivalents allocated to the grain, grain growth and the dynamics of the oil and non-oil fraction, while considering maintenance requirements and leaf senescence. Incorporating into the model the serial-parallel nature of fatty acid biosynthesis permitted a good representation of the kinetics of palmitic, stearic, oleic, and linoleic acids production. A sensitivity analysis showed that the relative influence of input parameters changed along grain development. Grain growth was mostly affected by the specific growth parameter (μ′) while fatty acid composition strongly depended on their own maximum specific rate parameters. The model was successfully applied to two additional hybrids (MG2 and DK3820). The proposed model can be the first building block toward the development of a more sophisticated model, capable of predicting the effects of environmental conditions on grain weight and composition, in a comprehensive and quantitative way. PMID:27242809

  7. Kinetics and Mechanism of Oxidation of Phenyl Acetic Acid and Dl-Mandelic Acid by Permanganate in Acid Medium

    B. Syama Sundar; P.S.Radhakrishna murti

    2014-01-01

    Kinetics of oxidation of phenyl acetic acid and DL- Mandelic acid by potassium permanganate in aqueous acetic acid and perchloric acid mixture reveals that the kinetic orders are first order in oxidant, first order in H+ and zero order in substrate for phenyl acetic acid. DL-Mandelic acid exhibits first order in oxidant and zero order in substrate. The results are rationalised by a mechanism involving intermediate formation of mandelic acid in case of Phenyl acetic acid and ester formation wi...

  8. Kinetics of Demineralization of Shrimp Shell Using Lactic Acid

    Alewo Opuada AMEH

    2014-02-01

    Full Text Available Shrimp exoskeleton was demineralized using lactic acid and the kinetics of the demineralisation was studied. The residual concentration of calcium after acid treatment was used as a measure of the degree of demineralisation. Kinetic data was obtained using five acid concentrations (0.2, 0.4, 0.6, 0.8 and 1M and the obtained kinetic data was fitted to the shrinking core model. For all concentrations, the best predictive model was determined to be ash layer diffusion controlled mechanism.

  9. Kinetics of molecular transformations in connective tissue hyaluronic acid

    When exposed to ionizing radiations or inflammatory disease, the glycosaminolycan component of connective tissue is preferentially degraded, probably by a free-radical mediate pathway. The resulting changes in molecular structure adversely change the properties of the matrix. Rooster comb hyaluronic acid of high molecular weight was used to investigate the mechanisms of these structural changes at macro and molecular level. Intrinsic viscosity and gel permeation chromatography measurements are suitable for demonstrating that random chain session occurs. Fast kinetic techniques are necessary to identify the mechanisms of single strand breaks. Pulse conductivity and low-angle laser light scattering pulse radiolysis can quantify the rate and yield of strand breaks. Competitive radical scavenging methods have also allowed the quantification of the rate of spontaneous and alkali-catalyzed hydrolysis of a-hydroxy radicals on polysaccharide chains, which control molecular structure changes

  10. Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid

    The reaction kinetics of the esterification of ethylene glycol with acetic acid in the presence of cation exchange resin has been studied and kinetic models based on empirical and Langmuir approach has been developed. The Langmuir based model involving eight kinetic parameters fits experimental data much better compared to empirical model involving four kinetic parameters. The effect of temperature and catalyst loading on the reaction system has been analyzed. Further, the activation energy and frequency factor of the rate constants for Langmuir based model has been estimated.

  11. Single molecule DNA interaction kinetics of retroviral nucleic acid chaperone proteins

    Williams, Mark

    2010-03-01

    Retroviral nucleocapsid (NC) proteins are essential for several viral replication processes including specific genomic RNA packaging and reverse transcription. The nucleic acid chaperone activity of NC facilitates the latter process. In this study, we use single molecule biophysical methods to quantify the DNA interactions of wild type and mutant human immunodeficiency virus type 1 (HIV-1) NC and Gag and human T-cell leukemia virus type 1 (HTLV-1) NC. We find that the nucleic acid interaction properties of these proteins differ significantly, with HIV-1 NC showing rapid protein binding kinetics, significant duplex destabilization, and strong DNA aggregation, all properties that are critical components of nucleic acid chaperone activity. In contrast, HTLV-1 NC exhibits significant destabilization activity but extremely slow DNA interaction kinetics and poor aggregating capability, which explains why HTLV-1 NC is a poor nucleic acid chaperone. To understand these results, we developed a new single molecule method for quantifying protein dissociation kinetics, and applied this method to probe the DNA interactions of wild type and mutant HIV-1 and HTLV-1 NC. We find that mutations to aromatic and charged residues strongly alter the proteins' nucleic acid interaction kinetics. Finally, in contrast to HIV-1 NC, HIV-1 Gag, the nucleic acid packaging protein that contains NC as a domain, exhibits relatively slow binding kinetics, which may negatively impact its ability to act as a nucleic acid chaperone.

  12. Acid-catalyzed kinetics of indium tin oxide etching

    We report the kinetic characterization of indium tin oxide (ITO) film etching by chemical treatment in acidic and basic electrolytes. It was observed that film etching increased under more acidic conditions, whereas basic conditions led to minimal etching on the time scale of the experiments. Quartz crystal microbalance was employed in order to track the reaction kinetics as a function of the concentration of hydrochloric acid and accordingly solution pH. Contact angle measurements and atomic force microscopy experiments determined that acid treatment increases surface hydrophilicity and porosity. X-ray photoelectron spectroscopy experiments identified that film etching is primarily caused by dissolution of indium species. A kinetic model was developed to explain the acid-catalyzed dissolution of ITO surfaces, and showed a logarithmic relationship between the rate of dissolution and the concentration of undisassociated hydrochloric acid molecules. Taken together, the findings presented in this work verify the acid-catalyzed kinetics of ITO film dissolution by chemical treatment, and support that the corresponding chemical reactions should be accounted for in ITO film processing applications. - Highlights: • Acidic conditions promoted indium tin oxide (ITO) film etching via dissolution. • Logarithm of the dissolution rate depended linearly on the solution pH. • Acid treatment increased ITO surface hydrophilicity and porosity. • ITO film etching led to preferential dissolution of indium species over tin species

  13. Kinetic and Thermodynamic Parameters for Uncatalyzed Esterification of Carboxylic Acid

    Kehinde S. Bankole

    2014-06-01

    Full Text Available A fundamental study on uncatalyzed esterification of various biomass-derived aliphatic carboxylic acids with stoichiometric amount of ethanol has been investigated in an isothermal batch reactor, with the objective to convert carboxylic acids to corresponding ethyl esters and to determine both the kinetic and thermodynamic parameters. The effects of temperature on the conversion of carboxylic acid, kinetic and thermodynamic parameters have been investigated. Temperature was found to have significant effect on the rate of reaction and conversion of carboxylic acid. A simple second order reversible kinetic model was developed to determine the kinetic and thermodynamic parameters. The thermodynamic and kinetic parameters varied for uncatalyzed esterification reaction of both short-chain and long-chain carboxylic acids considered. The predicted data from the kinetic model were correlated with experimental data and the two sets of data agreed reasonably well for the uncatalyzed esterification systems. It was observed that the Van’t Hoff plot for uncatalyzed esterification of linoleic acid was non-linear curve, whereas for the Arrhenius and Eyring plots, they were linear. Additional experiments to assess the catalytic and corrosion effects of several metallic substances revealed Inconel 625 alloy, nickel wire and stainless steel materials were susceptible to corrosion problem with uncatalyzed esterification reaction at elevated reaction temperatures. However, tantalum and grade-5 titanium materials were corrosion resistance metals, suitable for similar reaction conditions and this can encourage the design of a flow reactor system. Although, uncatalyzed esterification of carboxylic acids at elevated reaction temperature is still at laboratory scale. It is our hope that the estimated kinetic and thermodynamic parameters would be the guiding tools for reactor scale-up, thus providing a new perspective into the conversion of biomass-derived carboxylic

  14. Kinetics of Hydrogen Evolution on Copper Electrode Involving Organic Acids as Proton Donors

    A. Survila; Kanapeckaitė, S.; Pileckienė, J.; Būdienė, J.

    2011-01-01

    Linear potential sweep (LPS) voltammetry was applied to study the kinetics of hydrogen evolution in solutions containing glycolic, malic, tartaric, and gluconic acids. The CE mechanism of hydrogen evolution was analyzed invoking the 2nd Fick's law equations supplemented by terms that account for chemical interactions between diffusing particles. Acids are considered as components that are capable of releasing hydrated protons taking part in the charge-transfer step. Current peaks observed on ...

  15. Kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid

    Girisuta, B.; Janssen, L. P. B. M.; Heeres, H. J.

    2007-01-01

    A variety of interesting bulk chemicals is accessible by the acid-catalyzed hydrolysis of cellulose. An interesting example is levulinic acid, a versatile precursor for fuel additives, polymers, and resins. A detailed kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid is r

  16. Thermodynamic and kinetic aspects of surface acidity. Progress report

    Dumesic, J.A.

    1992-04-01

    Our research in the general area of acid catalysis involves the characterization of solid acidity and the corresponding assessment of catalytic performance of acidic materials. Acid characterization studies are required to provide essential information about the type of acid site (i.e., Lewis versus Bronsted), the strength of the sites, and the mobility of molecules adsorbed on the acid sites. An accurate measure of acid strength is given by the heat of adsorption of a basic probe molecule on the acid site. A thermodynamic representation of the mobility of adsorbed species on these sites is given by the entropy of adsorption. Important techniques used in these acid site characterization studies include microcalorimetry, thermogravimetric measurements, temperature programmed desorption, infrared spectroscopy and solid state nuclear magnetic resonance. The combination of these acid site characterization studies with reaction kinetics measurements of selected catalytic processes allows the elucidation of possible relationships between surface thermodynamic and kinetic properties of acidic sites. Such relationships are important milestones in formulating effective strategies for the effective utilization of solid acid catalysts. Current work in this direction involves methylamine syntheses over various zeolites, and the basic probe molecules employed include ammonia, methanol, water and mono-, di- and tri-methylamines. 31 refs., 18 figs., 1 tab.

  17. Ab initio and kinetic modeling studies of formic acid oxidation

    Marshall, Paul; Glarborg, Peter

    2015-01-01

    A detailed chemical kinetic model for oxidation of formic acid (HOCHO) in flames has been developed, based on theoretical work and data from literature. Ab initio calculations were used to obtain rate coefficients for reactions of HOCHO with H, O, and HO2. Modeling predictions with the mechanism...... on calculations with the kinetic model. Formic acid is consumed mainly by reaction with OH, yielding OCHO, which dissociates rapidly to CO2 + H, and HOCO, which may dissociate to CO + OH or CO2 + H, or react with H, OH, or O2 to form more stable products. The branching fraction of the HOCHO + OH...

  18. Kinetics and Mechanism of Oxidation of Phenyl Acetic Acid and Dl-Mandelic Acid by Permanganate in Acid Medium

    B.Syama Sundar

    2014-06-01

    Full Text Available Kinetics of oxidation of phenyl acetic acid and DL- Mandelic acid by potassium permanganate in aqueous acetic acid and perchloric acid mixture reveals that the kinetic orders are first order in oxidant, first order in H+ and zero order in substrate for phenyl acetic acid. DL-Mandelic acid exhibits first order in oxidant and zero order in substrate. The results are rationalised by a mechanism involving intermediate formation of mandelic acid in case of Phenyl acetic acid and ester formation with Mn (VII in case of DL-Mandelic acid. The following order of reactivity is observed: DL-Mandelic acid > Phenyl acetic acid. The high reactivity of DL-Mandelic acid over phenyl acetic acid may be due to different mechanisms operating with the two substrates and benzaldehyde is the final product in both the cases.

  19. Kinetics of esterification of methanol and acetic acid with mineral homogeneous acid catalyst

    Mallaiah Mekala; Venkat Reddy Goli

    2015-01-01

    In this work, esterification of acetic acid and methanol to synthesize methyl acetate in a batch stirred reactor is studied in the temperature range of 305.15–333.15 K. Sulfuric acid is used as the homogeneous catalyst with concentrations ranging from 0.0633 mol·L−1 to 0.3268 mol·L−1. The feed molar ratio of acetic acid to methanol is varied from 1:1 to 1:4. The influences of temperature, catalyst concentration and reactant concentration on the reaction rate are investigated. A second order kinetic rate equation is used to correlate the experimental data. The forward and backward reaction rate constants and activation energies are determined from the Arrhenius plot. The developed kinetic model is compared with the models in literature. The developed kinetic equation is useful for the simulation of reactive distillation column for the synthesis of methyl acetate.

  20. Sulfuric acid leaching kinetics of South African chromite

    Qing Zhao; Cheng-jun Liu; Pei-yang Shi; Bo Zhang; Mao-fa Jiang; Qing-song Zhang; Ron Zevenhoven; Henrik Saxn

    2015-01-01

    The sulfuric acid leaching kinetics of South African chromite was investigated. The negative influence of a solid product layer constituted of a silicon-rich phase and chromium-rich sulfate was eliminated by crushing the chromite and by selecting proper leaching con-ditions. The dimensionless change in specific surface area and the conversion rate of the chromite were observed to exhibit a proportional re-lationship. A modified shrinking particle model was developed to account for the change in reactive surface area, and the model was fitted to experimental data. The resulting model was observed to describe experimental findings very well. Kinetics analysis revealed that the leach-ing process is controlled by a chemical reaction under the employed experimental conditions and the activation energy of the reaction is 48 kJ·mol–1.

  1. The Kinetics and Mechanism for the Oxidation of Nicotinic Acid by Peroxomonosulfate in Acidic Aqueous Medium

    The kinetics of oxidation of nicotinic acid by peroxomonosulfate (PMS) has been studied in acetate buffers. Stoichiometry of the reaction corresponds to the reaction of one mole of the oxidant with a mole of nicotinic acid. N→O product has been confirmed both by UV visible and IR spectroscopy. The reaction is second order viz. first order with respect to each reactant. Activation parameters have also been evaluated. A plausible reaction mechanism is mentioned and the derived kinetic rate law accounts for experimental observations

  2. Kinetics of xylose dehydration into furfural in acetic acid

    Zhou Chen; Weijiang Zhang; Jiao Xu; Pingli Li

    2015-01-01

    In this paper kinetics of xylose dehydration into furfural using acetic acid as catalyst was studied comprehensively and systematical y. The reaction order of both furfural and xylose dehydration was determined and the reaction activation energy was obtalned by nonlinear regression. The effect of acetic acid concentration was also investi-gated. Reaction rate constants were galned. Reaction rate constant of xylose dehydration is k1 ¼ 4:189 . 1010 ½A.0:1676 exp −108:6.1000RT . ., reaction rate constant of furfural degradation is k2 ¼ 1:271 . 104½A.0:1375 exp−63:413.1000RT . and reaction rate constant of condensation reaction is k3 ¼ 3:4051 . 1010½A.0:1676 exp−104:99.1000RT .. Based on this, the kinetics equation of xylose dehydration into furfural in acetic acid was set up according to theory of Dunlop and Furfural generating rate equation is dd½F.t ¼ k1½X.0e−k1t−k2½F.−k3½X.0e−k1t½F.. © 2015 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.

  3. Lipid-Nucleic Acid Supramolecular Complexes: Lipoplex Structure and the Kinetics of Formation

    Nily Dan

    2015-06-01

    Full Text Available The need for synthetic gene therapy or gene silencing vehicles that can insert therapeutic nucleic acids (DNA or siRNA into cells (so-called transfection has focused interest on lipid-nucleic acid assemblies (lipoplexes. This paper reviews the kinetics pathways leading to lipoplex formation and structure. The process is qualitatively comparable to those of cluster nucleation and growth and to the adsorption of polyelectrolytes on colloidal particles: Initially is a rapid stage where the nucleic acid binds onto the surface of the cationic lipid aggregate (adsorption, or nucleation. This is followed by an intermediate step where the lipid/nucleic acid complexes flocculate to form larger structures (growth. The last and final step involves internal rearrangement, where the overall global structure remains constant while local adjustment of the nucleic acid/lipid organization takes place until the equilibrium lipoplex characteristics are obtained. This step can require unusually long time scales of order hours or longer. Understanding the kinetics of lipoplex formation is not only of fundamental interest as a multi-component, multi-length scale and multi-time scale process, but also has significant implications for the utilization of lipoplexes as carriers for gene delivery and gene silencing agents.

  4. Acid base catalyzed transesterification kinetics of waste cooking oil

    Jain, Siddharth; Sharma, M.P.; Rajvanshi, Shalini [Alternate Hydro Energy Centre, Indian Institute of Technology, Roorkee (India)

    2011-01-15

    The present study reports the results of kinetics study of acid base catalyzed two step transesterification process of waste cooking oil, carried out at pre-determined optimum temperature of 65 C and 50 C for esterification and transesterification process respectively under the optimum condition of methanol to oil ratio of 3:7 (v/v), catalyst concentration 1%(w/w) for H{sub 2}SO{sub 4} and NaOH and 400 rpm of stirring. The optimum temperature was determined based on the yield of ME at different temperature. Simply, the optimum concentration of H{sub 2}SO{sub 4} and NaOH was determined with respect to ME Yield. The results indicated that both esterification and transesterification reaction are of first order rate reaction with reaction rate constant of 0.0031 min{sup -1} and 0.0078 min{sup -1} respectively showing that the former is a slower process than the later. The maximum yield of 21.50% of ME during esterification and 90.6% from transesterification of pretreated WCO has been obtained. This is the first study of its kind which deals with simplified kinetics of two step acid-base catalyzed transesterification process carried under the above optimum conditions and took about 6 h for complete conversion of TG to ME with least amount of activation energy. Also various parameters related to experiments are optimized with respect to ME yield. (author)

  5. Kinetic Optimization of Folic Acid Polymer Conjugates for Drug Targeting

    Jacob M. Ngoy

    2011-01-01

    Full Text Available Problem statement: Folic Acid (FA is an essential, bioavailable water soluble B-complex vitamin that helps in the replication of normal cells. It is obtained from natural sources and it deficiency can leads to oncogenic cells development. Within this frame work in mind, we designed and synthesized a new bioconjugate carrier that can enhance the effectiveness of FA. Approach: The polymeric carrier: Polysucscinimide (PSI was synthesized via the polycondensation of aspartic acid by attaching 3-(N,N-Dimethylamino Propylamine (DMP and 1,3-P-propylenediamine (PDA for solubility behavior and reactivity for FA site anchoring. Also the use of an ester 2-(1H-benzotrial-1- yl-1,1,3,3-tetramethylurium Hexafluorophosphate (HBTU as coupling agent to FA. The bioreversible binding of the water-soluble and biocompatible macromolecular were attested through kinetic studies. The kinetic reactions were investigated through the nuclear resonance (H1NMR spectra analysis. Results and Conclusion: The H1NMR optimization reaction times were found within the range of 120-130 min (80-85% as optimum coupling. The yield of the FA occurred within the same time range but with maximum incorporation between 90-100%. The growth of FA incorporation in terms of reaction time resulted to an increase inherent viscosity relative to the decrease of water solubility of the conjugate obtained.

  6. Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid

    A. W. Birdsall

    2012-11-01

    Full Text Available The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA.

  7. Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid

    A. W. Birdsall

    2013-03-01

    Full Text Available The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA.

  8. Radiomimeticity of the system H{sub 2}O{sub 2}/Fe(II) on nucleic acid components. Kinetics study; Radiomimeticidad del sistema H{sub 2}O{sub 2}/Fe(II) sobre components de Acidos Nucleicos. Estudio Cinetico

    Cirauqui, R.; Mingot, F.; Davila, C. A.

    1974-07-01

    The kinetic study of the action of a redox system on DNA monomers allowed us to make criticisms on radiomimetic character of this system. Assuming that in both cases, gamma radiolysis of aerated aqueous solutions and action of H{sub 2}O{sub 2} / Fe(II) system in the same conditions, the reactive species is the OH radical, we propose the kinetic expressions that are confirmed by our experimental results. Some of the accepted G-values are corrected in view of our results. Al so these results put in evidence mechanisms of molecular repair after radical attack. (Author) 79 refs.

  9. [Leaching kinetics of josephinite tailings with sulfuric acid].

    Chen, An-An; Zhou, Shao-Qi; Huang, Peng-Fei

    2013-07-01

    Leaching is the most important step of josephinite tailing recycle technology. This step can separate the valuable metal Mg from Si and other impure metal. Effects of sulfuric acid on leaching Mg efficiency from josephinite tailings were investigated. To obtain the leaching behavior, a modified unreacted shrinking core model that based on the experimental data was used to determine the dissolution kinetic parameters. The model was significant and showed that the dissolution of Mg2+ in josephinite tailing was controlled by the produce layer diffusion, apparent activation reaction energy E = 34.04 kJ x mol(-1). The produce layers obstruct the forward reaction of the dissolution of Mg2+. PMID:24028005

  10. Intramolecular Lactonization of Poly(α-hydroxyacrylic acid: Kinetics and Reaction Mechanism

    Heli Virkki

    2015-01-01

    Full Text Available Poly(α-hydroxyacrylic acid, PHA, is one of the few polymers with biodegradable properties used in mechanical pulp bleaching to stabilize hydrogen peroxide. A new method for the in situ follow-up of the lactone ring formation of PHA has been developed. The results have further been applied to describe the reaction kinetics of the lactonization and hydrolysis reactions through parameter estimation. In addition, the reaction mechanism is elucidated by multivariate data analysis. Satisfactory identification and semiquantitative separation of the lactone ring as well as the acyclic (carboxyl and hydroxyl groups forms have been established by 1H NMR in the pH range of 1–9. The lactonization reaction approaching equilibrium can be described by pseudo-first-order kinetics in the pH range of 1–6. The rate constants of the pseudo-first-order kinetic model have been estimated by nonlinear regression. Due to the very low rates of lactonization as well as the weak pH dependency of the reaction, an addition-elimination mechanism is proposed. Additionally, the presence of a transient reaction intermediate during lactonization reaction could be identified by subjecting the measurement data to multivariate data analysis (PCA, principal component analysis. A good correlation was found between the kinetic and the PCA models in terms of model validity.

  11. Kinetics and mechanism of reduction of iron (III) kojic acid complex by ascorbic acid

    Kinetics of reduction of iron (III) kojic acid complex by ascorbic acid has been carried out using photodiode array spectrophotometer over the ranges: 4.0<=pH<=5.5 and 5.0<=T<=25.0 degree C at ionic strength 0.2 M under pseudo-first order conditions by stopped-flow technique. Rate of the reaction was found to be pH dependent. The redox reaction followed the saturation kinetics. The rate law is deduced as follows: Rate = (k/sub 3/k/sub eq(H/sup +/)(HAsc/sup -/)(Fe(KA)/sub 3/) / (HKA) + K/sub eq/(H/sup +/)(HAsc/sup -/) The activation parameters of this reaction were determined. A mechanism consistent with this rate law has been proposed. (author)

  12. 3.6. The kinetics of sulfuric acid decomposition of calcined concentrate of borosilicate ore

    Present article is devoted to kinetics of sulfuric acid decomposition of calcined concentrate of borosilicate ore. The experimental data of kinetics of extraction of boron oxide from danburite at sulfuric acid decomposition were obtained at 20-90 deg C temperature range and process duration 15-90 minutes. The flowsheet of obtaining of boric acid from borosilicate ores of Ak-Arkhar Deposit by sulfuric acid method was proposed.

  13. Cometary impact and amino acid survival - Chemical kinetics and thermochemistry

    Ross, D.S.

    2006-01-01

    The Arrhenius parameters for the initiating reactions in butane thermolysis and the formation of soot, reliable to at least 3000 K, have been applied to the question of the survival of amino acids in cometary impacts on early Earth. The pressure/temperature/time course employed here was that developed in hydrocode simulations for kilometer-sized comets (Pierazzo and Chyba, 1999), with attention to the track below 3000 K where it is shown that potential stabilizing effects of high pressure become unimportant kinetically. The question of survival can then be considered without the need for assignment of activation volumes and the related uncertainties in their application to extreme conditions. The exercise shows that the characteristic times for soot formation in the interval fall well below the cooling periods for impacts ranging from fully vertical down to about 9?? above horizontal. Decarboxylation, which emerges as more rapid than soot formation below 2000-3000 K, continues further down to extremely narrow impact angles, and accordingly cometa??ry delivery of amino acids to early Earth is highly unlikely. ?? 2006 American Chemical Society.

  14. Kinetics and effects of dichloroacetic acid in rainbow trout.

    Fitzsimmons, Patrick N; Hoffman, Alex D; Lien, Gregory J; Hammermeister, Dean E; Nichols, John W

    2009-09-14

    Halogenated acetic acids (HAAs) produced by chlorine disinfection of municipal drinking water represent a potentially important class of environmental contaminants. Little is known, however, about their potential to adversely impact fish and other aquatic life. In this study we examined the kinetics and effects of dichloroacetic acid (DCA) in rainbow trout. Branchial uptake was measured in fish confined to respirometer-metabolism chambers. Branchial uptake efficiency was passive diffusion through aqueous channels in the gill epithelium. DCA concentrations in tissues following prolonged (72, 168, or 336 h) waterborne exposures were expressed as tissue:plasma concentration ratios. Concentration ratios for the kidney and muscle at 168 and 336 h were consistent with the suggestion that DCA distributes primarily to tissue water. Reduced concentration ratios for the liver, particularly at 72 h, indicated that DCA was highly metabolized by this tissue. Routes and rates of elimination were characterized by injecting chambered animals with a high (5.0mg/kg) or low (50 microg/kg) bolus dose. DCA was rapidly cleared by naïve animals resulting in elimination half-lives (t(1/2)) of less than 4h. Waterborne pre-treatment of fish with DCA increased the persistence of a subsequently injected dose. In high dose animals, pre-treatment caused a 4-fold decrease in whole-body clearance (CL(B)) and corresponding increases in the area under the plasma concentration-time curve (extrapolated to infinity; AUC(0-->infinity)) and t(1/2). Qualitatively similar results were obtained in low dose fish, although the magnitude of the pre-treatment effect ( approximately 2.5-fold) was reduced. Renal and branchial clearance contributed little (combined, <3% of CL(B)) to the elimination of DCA. Biliary elimination of DCA was also negligible. The steady-state volume of distribution (V(SS)) did not vary among treatment groups and was consistent with results of the tissue distribution study. DCA had no

  15. 3.3. The kinetics of sulfuric acid decomposition of calcined borosilicate ore

    Present article is devoted to kinetics of sulfuric acid decomposition of calcined borosilicate ore. The experimental data of kinetics of extraction of boron oxide from calcined borosilicate ore at sulfuric acid decomposition were obtained at 30-95 deg C temperature ranges and process duration from 15 to 60 minutes.

  16. Kinetics of oxidation of acidic amino acids by sodium N-bromobenzenesulphonamide in acid medium: A mechanistic approach

    Puttaswamy; Nirmala Vaz

    2001-08-01

    Kinetics of oxidation of acidic amino acids (glutamic acid (Glu) and aspartic acid (Asp)) by sodium N-bromobenzenesulphonamide (bromamine-B or BAB) has been carried out in aqueous HClO4 medium at 30°C. The rate shows firstorder dependence each on [BAB]o and [amino acid]o and inverse first-order on [H+]. At [H+] > 0 60 mol dm-3, the rate levelled off indicating zero-order dependence on [H+] and, under these conditions, the rate has fractional order dependence on [amino acid]. Succinic and malonic acids have been identified as the products. Variation of ionic strength and addition of the reaction product benzenesulphonamide or halide ions had no significant effect on the reaction rate. There is positive effect of dielectric constant of the solvent. Proton inventory studies in H2O-D2O mixtures showed the involvement of a single exchangeable proton of the OH- ion in the transition state. Kinetic investigations have revealed that the order of reactivity is Asp > Glu. The rate laws proposed and derived in agreement with experimental results are discussed.

  17. Green chemicals : A Kinetic Study on the Conversion of Glucose to Levulinic Acid

    Girisuta, B.; Janssen, L.P.B.M.; Heeres, H.J.

    2006-01-01

    Levulinic acid has been identified as a promising green, biomass derived platform chemical. A kinetic study on one of the key steps in the conversion of biomass to levulinic acid, i.e., the acid catalysed decomposition of glucose to levulinic acid has been performed. The experiments were performed i

  18. Kinetics of reaction between acetic acid and Ag2+ in nitric acid medium

    The reaction kinetics between acetic acid and Ag2+ in nitric acid medium is studied by spectrophotometry. The effects of concentrations of acetic acid (HAc), H+, NO3- and temperature on the reaction are investigated. The rate equation has been determined to be -dc(Ag2+)/dt=kc(Ag2+)c(HAc)c-1(H+), where k = (610±15) (mol/L)-1·min-1 with an activation energy of about (48.8±3.5) kJ·mol-1 when the temperature is 25degC and the ionic strength is 4.0 mol/L. The reduction rate of Ag2+ increases with the increase of HAc concentration or temperature and the decrease of HNO3 concentration. However, the effect of NO3- concentrations on the reaction rate is negligible. (author)

  19. Kinetics and mechanism of the oxidation of some neutral and acidic -amino acids by tetrabutylammonium tribromide

    Raghvendra Shukla; Pradeep K Sharma; Kalyan K Banerji

    2004-03-01

    The oxidation of eleven amino acids by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid results in the formation of the corresponding carbonyl compounds and ammonia. The reaction is first order with respect to TBATB. Michaelis-Menten type kinetics is observed with some of the amino acids while others exhibit second-order dependence. It failed to induce polymerization of acrylonitrile. The effect of solvent composition indicate that the rate of reaction increases with increase in the polarity of the medium. Addition of tetrabutylammonium chloride has no effect on the rate of oxidation. Addition of bromide ion causes decrease in the oxidation rate but only to a limiting value. The reaction is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.

  20. Kinetic characterization of a novel acid ectophosphatase from Enterobacter asburiae.

    Sato, Vanessa Sayuri; Galdiano Júnior, Renato F; Rodrigues, Gisele Regina; Lemos, Eliana G M; Pizauro Junior, João Martins

    2016-02-01

    Expression of acid ectophosphatase by Enterobacter asburiae, isolated from Cattleya walkeriana (Orchidaceae) roots and identified by the 16S rRNA gene sequencing analysis, was strictly regulated by phosphorus ions, with its optimal activity being observed at an inorganic phosphate concentration of 7 mM. At the optimum pH 3.5, intact cells released p-nitrophenol at a rate of 350.76 ± 13.53 nmol of p-nitrophenolate (pNP)/min/10(8) cells. The membrane-bound enzyme was obtained by centrifugation at 100,000 × g for 1 h at 4 °C. p-Nitrophenylphosphate (pNPP) hydrolysis by the enzyme follows "Michaelis-Menten" kinetics with V = 61.2 U/mg and K0.5 = 60 μM, while ATP hydrolysis showed V = 19.7 U/mg, K0.5 = 110 μM, and nH = 1.6 and pyrophosphate hydrolysis showed V = 29.7 U/mg, K0.5 = 84 μM, and nH = 2.3. Arsenate and phosphate were competitive inhibitors with K i = 0.6 mM and K i = 1.8 mM, respectively. p-Nitrophenyl phosphatase (pNPPase) activity was inhibited by vanadate, while p-hydroxymercuribenzoate, EDTA, calcium, copper, and cobalt had no inhibitory effects. Magnesium ions were stimulatory (K0.5 = 2.2 mM and nH = 0.5). Production of an acid ectophosphatase can be a mechanism for the solubilization of mineral phosphates by microorganisms such as Enterobacter asburiae that are versatile in the solubilization of insoluble minerals, which, in turn, increases the availability of nutrients for plants, particularly in soils that are poor in phosphorus. PMID:26832666

  1. Surface components of chylomicrons from rats fed glyceryl or alkyl esters of fatty acids: minor components.

    Yang, L Y; Kuksis, A; Myher, J J; Pang, H

    1992-08-01

    The lipid class, fatty acid and molecular species composition of the minor polar surface components of rat lymph chylomicrons were determined during absorption of menhaden oil and corn oil or of the corresponding fatty acid ethyl esters. In addition to the previously reported minor polar lipids (sphingomyelin, phosphatidylserine, phosphatidylinositol, phosphatidic acid and lysophosphatidylcholine), we identified phosphatidylglycerol, dimethylphosphatidylethanolamine, ceramide and cholesteryl sulfate in the chylomicrons from both oil and ester feeding. The dietary fatty acids were found to be incorporated to a variable extent into the different phospholipid classes, the proportions of which remained the same during both types of feeding. No evidence was obtained for the presence of the minor glycerophospholipids characteristic of the lysosomal membranes (e.g., bis-phosphatidic, lysobisphosphatidic and semilysobis-phosphatidic acids), although special efforts were made to identify them. These results indicate that the chylomicrons arising from the monoacylglycerol and phosphatidic acid pathways of triacylglycerol biosynthesis become enveloped in closely similar monolayers of phospholipids. Hence, all triacylglycerols may be secreted from the villus cells via a common mechanism as suggested by the previously demonstrated convergence (at the 2-monoacylglycerol stage) of the monoacylglycerol and the phosphatidic acid pathways of mucosal triacylglycerol formation [Yang, Y.L., and Kuksis, A. (1991) J. Lipid Res. 32, 1173-1186]. PMID:1406072

  2. Kinetic isotope effect of carbon-13 in decarboxylation of phenylpropiolic acid in anhydrous formic acid

    Carbon-13 kinetic isotope effects in the decarboxylation of phenylpropiolic acid (carboxyl-13C) in formic acid medium and in the decarbonylation of liquid formic acid assisted with phenylpropiolic acid (PPA) and acetophenone (AP) have been studied in the 70-100oC temperature interval. The carboxyl-13C KIEs are in the range 1.0034 at 71.6oC and 1.0047 at 101.2oC respectively. The C-13C KIE, k-12/k-13, in the decarbonylation of liquid formic acid assisted with PPA were found to be of 1.0419 at 71.6oC and 1.0383 at 101.2oC. The C-13 KIE in the decarbonylation of pure formic acid are 1.0464 at 70.2oC and 1.0411 at 98oC respectively. The above experimental results have been discussed and interpreted as indicating that the formation of Cα-H bond preceded by the protonation of triple acetylenic bond of PPA is the rate determining step followed by carbon dioxide splitting. The 13-CO-KIE in the carbon monooxide generation assisted with PPA is much larger than the 13-CO-KIE generated in the presence of phenylacetylene. This shows that the decarboxylation of PPA and decarboxylation of FA are interrelated processes proceeding in the reaction cage. The formic acid involved in the formation of TS is decarbonylating directly avoiding probably largely the formic acid anhydride intermediate formation. (author)

  3. Components development for sulfuric acid processing in the IS process

    The Japan Atomic Energy Agency (JAEA) has been conducting research and development on a thermochemical iodine–sulfur (IS) process, one of most attractive water-splitting hydrogen production methods, that uses the nuclear heat of a high-temperature gas-cooled reactor (HTGR). An examination is planned to verify the integrity of the components in the sulfuric acid decomposition section. A bayonet-type sulfuric acid decomposer made of SiC ceramics, a key component in the section, was test-fabricated. In parallel, a direct-contact heat exchanger (DCHX) is contemplated for use in the sulfuric acid decomposition section to simplify the process. The application of the DCHX makes it possible to perform heat recovery and separate undecomposed sulfuric acid from the decomposed gaseous mixture in one reactor. Although the concept is very attractive, little is known about the heat and mass transfer behavior in the DCHX. Therefore, a test apparatus was constructed to measure the gas-phase mass transfer coefficients required for the optimal design of the DCHX. These coefficients of water were acquired and compared with an empirical correlation. The experimental data were in good agreement with those obtained from empirical correlation, and thus, the apparatus was confirmed to be reasonable

  4. PCB congener sorption to carbonaceous sediment components: Macroscopic comparison and characterization of sorption kinetics and mechanism

    Sorption of polychlorinated biphenyls (PCBs) to sediment is a key process in determining their mobility, bioavailability, and chemical decomposition in aquatic environments. In order to examine the validity of currently used interpretation approaches for PCBs sorption, comparative results on 2-chlorobiphenyl sorption to carbonaceous components in sediments (activated carbon, carbon black, coal, soot, graphite, flyash, wood) were macroscopically correlated with the structural, morphological, crystallographic, and compositional properties of the carbonaceous components. Since the Freundlich sorption constant, KF (L kg-1) spanned several orders of magnitude, ranging from log KF of 6.13-5.27 for activated carbon, 5.04 for carbon black, 3.83 for coal to 3.08 for wood, organic carbon partitioning approach should be more specifically categorized, considering the various forms, nature and origins of organic carbon in sediment. Sorption rate constants and fraction parameters, which were numerically defined from empirical kinetic model with fast and slow sorption fractions, were closely related to the physicochemical properties of the carbonaceous components. Sorption interpretation approaches with a specific property and viewpoint, such as organic carbon partitioning, soot carbon distribution, or surface area correlation, did not properly explain the overall results on sorption capacity, fast and slow sorption kinetics, and partitioning coefficient. It is also important to emphasize the heterogeneous nature of sediment and the difficulties of encompassing the partitioning among its carbonaceous components.

  5. Kinetic modelling of the demineralization of shrimp exoskeleton using citric acid

    Alewo Opuada AMEH; Muhammed Tijani ISA; David ABUTU; Alibaba DANLAMI

    2014-01-01

    Citric acid was used in the demineralization of shrimp exoskeleton and the kinetics of the demineralization process was studied. Kinetic data was obtained by demineralisation using five acid concentrations (0.1, 0.2, 0.3, 0.4 and 0.5M). The obtained kinetic data were fitted to the shrinking core model for fluid particle reactions. The concentration of calcium was found to decrease with time. For all acid concentrations considered, the best predictive mechanism for the demineralization process...

  6. Kinetics of Formic Acid-autocatalyzed Preparation of Performic Acid in Aqueous Phase

    孙晓英; 赵雪冰; 杜伟; 刘德华

    2011-01-01

    Performic acid (PFA) is an oxidant used in chemical processing, synthesis and bleaching. The macro kinetic models of synthesis, hydrolysis and decomposition of PFA were investigated via formic acid-autocatalyzed reaction. It was found that the intrinsic activation energies of PFA synthesis and hydrolysis were 75.2 kJ·mol^-1 and 40.4 kJ·mol^-1 respectively. The observed activation energy of PFA decomposition was 95.4 kJ·mol^-1. The experi-mental results indicated that the decomposition of PFA was liable to occur even at the ambient temperature. Both the spontaneous decomposition and the radical-introduced decomposition contributed to the decomposition of PFA.

  7. Kinetics of Acid Reactions: Making Sense of Associated Concepts

    Tan, Kim Chwee Daniel; Treagust, David F.; Chandrasegaran, A. L.; Mocerino, Mauro

    2010-01-01

    In chemical kinetics, in addition to the concepts related to kinetics, stoichiometry, chemical equilibrium and the characteristics of the reactants are often involved when comparing the rates of different reactions, making such comparisons very challenging for students at all levels, as well as for pre-service science teachers. Consequently, four…

  8. Kinetic Study of the Reaction between Tert-butyl Hydrazine and Nitrous Acid

    2001-01-01

    The kinetic study of the reaction between tert-butyl hydrazine(TBH)and nitrous acid in nitric acid system is performed by spectrophotometry. The effect of some factors such as the concentration of TBH, the concentration of nitric acid, ionic strength, temperature and the

  9. Esterification of Oleic Acid for Biodiesel Production Catalyzed by SnCl2: A Kinetic Investigation

    Marcio J. da Silva

    2008-09-01

    Full Text Available The production of biodiesel from low-cost raw materials which generally contain high amounts of free fatty acids (FFAs is a valuable alternative that would make their production costs more competitive than petroleum-derived fuel. Currently, the production of biodiesel from this kind of raw materials comprises a two-stage process, which requires an initial acid-catalyzed esterification of the FFA, followed by a basecatalyzed transesterification of the triglycerides. Commonly, the acid H2SO4 is the catalyst on the first step of this process. It must be said, however, that major drawbacks such as substantial reactor corrosion and the great generation of wastes, including the salts formed due to neutralization of the mineral acid, are negative and virtually unsurmountable aspects of this protocol. In this paper, tin(II chloride dihydrate (SnCl2·2H2O, an inexpensive Lewis acid, was evaluated as catalyst on the ethanolysis of oleic acid, which is the major component of several fat and vegetable oils feedstocks. Tin chloride efficiently promoted the conversion of oleic acid into ethyl oleate in ethanol solution and in soybean oil samples, under mild reaction conditions. The SnCl2 catalyst was shown to be as active as the mineral acid H2SO4. Its use has relevant advantages in comparison to mineral acids catalysts, such as less corrosion of the reactors and as well as avoiding the unnecessary neutralization of products. Herein, the effect of the principal parameters of reaction on the yield and rate of ethyl oleate production has been investigated. Kinetic measurements revealed that the esterification of oleic acid catalyzed by SnCl2·2H2O is first-order in relation to both FFAs and catalyst concentration. Experimentally, it was verified that the energy of activation of the esterification reaction of oleic acid catalyzed by SnCl2 was very close those reported for H2SO4.

  10. Conversion of hemicellulose sugars catalyzed by formic acid: kinetics of the dehydration of D-xylose, L-arabinose, and D-glucose.

    Dussan, Karla; Girisuta, Buana; Lopes, Marystela; Leahy, James J; Hayes, Michael H B

    2015-04-24

    The pre-treatment of lignocellulosic biomass produces a liquid stream of hemicellulose-based sugars, which can be further converted to high-value chemicals. Formosolv pulping and the Milox process use formic acid as the fractionating agent, which can be used as the catalyst for the valorisation of hemicellulose sugars to platform chemicals. The objective of this study was to investigate the reaction kinetics of major components in the hemicelluloses fraction of biomass, that is, D-xylose, L-arabinose and D-glucose. The kinetics experiments for each sugar were performed at temperatures between 130 and 170 °C in various formic acid concentrations (10-64 wt %). The implications of these kinetic models on the selectivity of each sugar to the desired products are discussed. The models were used to predict the reaction kinetics of solutions that resemble the liquid stream obtained from the fractionation process of biomass using formic acid. PMID:25821128

  11. Kinetics of the esterification of active pharmaceutical ingredients containing carboxylic Acid functionality in polyethylene glycol

    Schou-Pedersen, Anne Marie V; Hansen, Steen Honoré; Moesgaard, Birthe;

    2014-01-01

    reactions. In this study, kinetics of two active pharmaceutical ingredients, cetirizine and indomethacin possessing carboxylic acid functionality, has been studied in PEG 400 and PEG 1000 at 50°C, 60°C, 70°C, and 80°C. HPLC-UV was applied for the determination of concentrations in the kinetic studies...

  12. Kinetic study of CO2 with various amino acid salts in aqueous solution

    Holst, van J.; Versteeg, G.F.; Brilman, D.W.F.; Hogendoorn, J.A.

    2009-01-01

    A study towards the kinetics of CO2 with several aqueous salts of amino acids was performed at a temperature of 298 K. Absorption rate experiments were carried out in the pseudo-first-order regime, enabling the determination of the kinetic rate constant from the flux. In a preliminary screening at a

  13. Kinetic study of CO2 with various amino acid salts in aqueous solution

    van Hoist, J.; Versteeg, G. F.; Brilman, D. W. F.; Hogendoorn, J. A.; Holst, J. v

    2009-01-01

    A study towards the kinetics Of CO2 with several aqueous salts of amino acids was performed at a temperature of 298 K. Absorption rate experiments were carried out in the pseudo-first-order regime, enabling the determination of the kinetic rate constant from the flux. In a preliminary screening at a

  14. Kinetics of fatty acid binding ability of glycated human serum albumin

    Eiji Yamazaki; Minoru Inagaki; Osamu Kurita; Tetsuji Inoue

    2005-09-01

    Kinetics of fatty acid binding ability of glycated human serum albumin (HSA) were investigated by fluorescent displacement technique with 1-anilino-8-naphtharene sulphonic acid (ANS method), and photometric detection of nonesterified-fatty-acid (NEFA method). Changing of binding affinities of glycated HSA toward oleic acid, linoleic acid, lauric acid, and caproic acid, were not observed by the ANS method. However, decreases of binding capacities after 55 days glycation were confirmed by the NEFA method in comparison to control HSA. The decrease in binding affinities was: oleic acid (84%), linoleic acid (84%), lauric acid (87%), and caproic acid (90%), respectively. The decreases were consistent with decrease of the intact lysine residues in glycated HSA. The present observation indicates that HSA promptly loses its binding ability to fatty acid as soon as the lysine residues at fatty acid binding sites are glycated.

  15. Kinetics and mechanism of the oxidation of formic and oxalic acids by quinolinium fluorochromate

    Madhu Khurana; Pradeep K Sharma; Kalyan K Banerji

    2000-04-01

    Kinetics and mechanism of oxidation of formic and oxalic acids by quinolinium fluorochromate (QFC) have been studied in dimethylsulphoxide. The main product of oxidation is carbon dioxide. The reaction is first-order with respect to QFC. Michaelis-Menten type of kinetics were observed with respect to the reductants. The reaction is acid-catalysed and the acid dependence has the form: obs = + [H+]. The oxidation of -deuterioformic acid exhibits a substantial primary kinetic isotope effect (H/D = 6.01 at 303 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using Taft’s and Swain’s multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical cyclic transition state in the rate-determining step. Suitable mechanisms have been proposed

  16. KINETIC OF ESTERIFICATION OF ETHYL ALCOHOL BY ACETIC ACID ON A CATALYTIC RESIN

    Erol İNCE

    2002-01-01

    Full Text Available The conversion kinetics of diluted acetic acid to ethyl acetate by ethanol esterification in a batch reactor in liquid phase with an acidic polymer catalyst (lewatit series was studied. The intrinsic rate constants have been correlated with the reaction temperature, concentration of catalyst, initial ratios of reactants and initial water concentrations. The kinetic analysis was restricted to the system at hand in which a liquid and vapor phase are at equilibrium.

  17. KINETIC OF ESTERIFICATION OF ETHYL ALCOHOL BY ACETIC ACID ON A CATALYTIC RESIN

    Erol İNCE

    2002-01-01

    The conversion kinetics of diluted acetic acid to ethyl acetate by ethanol esterification in a batch reactor in liquid phase with an acidic polymer catalyst (lewatit series) was studied. The intrinsic rate constants have been correlated with the reaction temperature, concentration of catalyst, initial ratios of reactants and initial water concentrations. The kinetic analysis was restricted to the system at hand in which a liquid and vapor phase are at equilibrium.

  18. Development of acid-resistant HEPA filter components

    Laboratory and in-service tests of various HEPA filter media and separators were conducted to establish their relative resistances to HNO3-HF vapors. Filter medium of glass fiber with Nomex additive and aluminum separators with an epoxy-vinyl coating have performed quite well in the acid environment in the laboratory, and in prototype-filters placed in service in a plenum at Rocky Flats. Proprietary filters with new design and/or components were also tested in service with generally good results

  19. Study on the Hydrolysis Kinetics of Xylan on Different Acid Catalysts

    In this study, we investigated kinetic model for the acid-catalyzed xylan hydrolysis at temperature 120-150 .deg. C. Also, we analyzed the kinetic parameters for xylose production and furfural decomposition. The hydrolysis of xylan and the degradation of xylose were promoted by high reaction temperature and acid concentration. The optimal hydrolysis condition for the highest reaction rate constants (k1) was different depending on the acid catalysts. Among sulfuric, oxalic and maleic acid, the xylan reaction rate constants (k1) to xylose had the highest value of 0.0241 min-1 when 100 mM sulfuric acid was used at 120 .deg. C. However, sulfuric acid induced more xylose degradation compared to oxalic and maleic acid hydrolysis. The activation energy for xylan degradation was the highest when sulfuric acid was used

  20. Study on the Hydrolysis Kinetics of Xylan on Different Acid Catalysts

    Na, Byeong-Il; Lee, Jae-Won [Chonnam National University, Gwangju (Korea, Republic of)

    2014-04-15

    In this study, we investigated kinetic model for the acid-catalyzed xylan hydrolysis at temperature 120-150 .deg. C. Also, we analyzed the kinetic parameters for xylose production and furfural decomposition. The hydrolysis of xylan and the degradation of xylose were promoted by high reaction temperature and acid concentration. The optimal hydrolysis condition for the highest reaction rate constants (k{sub 1}) was different depending on the acid catalysts. Among sulfuric, oxalic and maleic acid, the xylan reaction rate constants (k{sub 1}) to xylose had the highest value of 0.0241 min{sup -1} when 100 mM sulfuric acid was used at 120 .deg. C. However, sulfuric acid induced more xylose degradation compared to oxalic and maleic acid hydrolysis. The activation energy for xylan degradation was the highest when sulfuric acid was used.

  1. Thermodynamics and kinetics of thermal decomposition of dibutylalkyl and dipentylalkyl phosphonate-nitric acid systems

    Highlights: • Thermal stability of neat and nitric acid solvated DBalP and DPalP have been studied for the first time. • Incompressible gases and reddish viscous or black solid residues were formed on decomposition. • Decomposition of acid solvated phosphonates was found to be exothermic and follows first order kinetics. • The thermodynamic and kinetic parameters were derived wherever possible. - Abstract: Thermal stability of neat and nitric acid-solvated dibutylalkyl and dipentylalkyl phosphonates was studied under closed air ambience using an adiabatic calorimeter. Enthalpies and kinetic parameters for the decomposition reaction were derived wherever possible and are reported for the first time. The neat compounds were found to be stable up to 555 K while the nitric acid-solvated phosphonates decomposed at lower temperatures (370–403 K) with exothermic rise in temperature and pressure invariably producing incompressible gases. Decomposition of all these acid-solvates followed first order kinetics. The rise in temperature and pressure was found to be strongly dependent on nitric acid content of the acid-solvate. While the neat phosphonates produced solid black residue, the acid-solvates produced a viscous reddish-brown residue on decomposition. Heat capacities (Cp), of acid-solvates (DBPrP·0.6HNO3, DBBP·0.6HNO3 and DBPP·0.6HNO3) were measured at constant pressure using a heat flux type differential scanning calorimeter in the temperature range 305–350 K

  2. Kinetics of sulfuric acid decomposition of pre-baked danburite of Ak-Arkhar deposit

    The results of studies of kinetics of sulfuric acid decomposition of pre-baked danburite of Ak-Arkhar deposit by means of first-order equation is given. It is defined that reaction passes in mixed area. The activation energy of sulfuric acid decomposition of pre-baked danburite is evaluated.

  3. A kinetic study on the decomposition of 5-hydroxymethylfurfural into levulinic acid

    Girisuta, B.; Janssen, L. P. B. M.; Heeres, H. J.

    2006-01-01

    Levulinic acid (LA), accessible by the acid catalyzed degradation of biomass, is potentially a very versatile green intermediate chemical for the synthesis of various (bulk) chemicals for applications like fuel additives, polymers, and resin precursors. We report here a kinetic study on one of the k

  4. Esterification of oleic acid with ethanol catalyzed by sulfonated cation exchange resin: Experimental and kinetic studies

    Graphical abstract: - Highlights: • Esterification of oleic acid with ethanol was investigated in the presence of sulfonated cation exchange resin. • We studied kinetic model of the esterification of oleic acid with ethanol according to experimental data. • The proposed kinetic model can well predict oleic acid conversion. - Abstract: This paper investigated the effects of ethanol to oleic acid molar ratio, reaction temperature, catalyst loading, water content and catalyst recycling on sulfonated cation exchange resin in a stirred batch reactor under atmospheric pressure. When the esterification was carried out with an ethanol to oleic acid (42.4 g) molar ratio of 9:1, reflux of ethanol at 82 °C, 20 g of catalyst and 8 h of reaction time, the oleic acid conversion rate reached approximately 93%. A pseudo-homogeneous kinetic model for describing the esterification of oleic acid with ethanol by the sulfonated cation exchange resin was developed on the basis of laboratorial results. The kinetic model can well predict the oleic acid conversion

  5. Kinetic study of hexavalent plutonium reduction by hydrogen peroxide in acid solution

    The kinetics of the reduction of hexavalent plutonium by hydrogen peroxide has been studied in perchloric, sulphuric and nitric acids. The rate of reduction is proportional to the initial concentrations of plutonium and of hydrogen peroxide and is inversely proportional to the acidity. The values of the proportionality constant k have been determined. They are very dependent on the temperature, on the ionic force and on the nature of the anion of the acid medium. An interpretation is put forward, based on the experimental results, attributing an important role to the hydrolysed species PuO2(OH)+ in the reduction kinetics. (author)

  6. 5.3. The kinetics of acetic acid decomposition of calcined borosilicate concentrate

    Present article is devoted to kinetics of acetic acid decomposition of calcined borosilicate concentrate. The experimental data of kinetics of boron oxide extraction from the calcined danburite concentrate at acetic acid decomposition was obtained at 30-90 deg C temperature ranges and 15-60 minutes process duration. It was defined that at temperature increasing the extraction rate of boron oxide from the calcined danburite concentrate significantly increases. The influence of extraction rate of boron oxide on process duration at acetic acid decomposition was studied.

  7. Carbon-13 kinetic isotope effects in the decarbonylation of lactic acid of natural isotopic composition in phosphoric acid medium

    The 13C kinetic isotope effect fractionation in the decarbonylation of lactic acid (LA) of natural isotopic composition by concentrated phosphoric acids (PA) and by 85% H3PO4 has been studied in the temperature interval of 60-150 deg C. The values of the 13C(1) isotope effects in the decarbonylation of lactic acid in 100% H3PO4, in pyrophosphoric acid and in more concentrated phosphoric acids are intermediate between the values calculated assuming that the C(1)-OH bond is broken in the rate-controlling step of dehydration and those calculated for rupture of the carbon-carbon bond in the transition state. In the temperature interval of 90-130 deg C the experimental 13C fractionation factors determined in concentrated PA approach quite closely the 13C fractionation corresponding to C(2)-C(1) bond scission. The 13C(1) kinetic isotope effects in the decarbonylation of LA in 85% orthophosphoric acid in the temperature range of 110-150 deg C coincide with the 13C isotope effects calculated assuming that the frequency corresponding to the C(1)-OH vibration is lost in the transition state of decarbonylation. A change of the mechanism of decarbonylation of LA in going from concentrated PA medium to 85% H3PO4 has been suggested. A possible secondary 18O and a primary18O kinetic isotope effect in decarbonylation of lactic acid in phosphoric acids media have been discussed, too. (author) 21 refs.; 3 tabs

  8. Kinetics of free radical decay reactions in lactic acid homo and copolymers irradiated to sterilization dose

    The kinetics of free radical decay reactions of poly(L-Lactic acid), poly(DL-Lactic acid) and random copolymer of lactic and glycolic acid have been investigated for decays taking place in air and in vacuum. The change in ESR lines of γ-irradiated polymers have been followed over a long time period. The decay has been found to follow neither simple first-order nor second-order kinetics. Various kinetic approaches including composite first or second-order mechanisms and diffusion-controlled first or second-order equations were determined to be also unsatisfactory. The decay of radicals in bulk irradiated lactic acid homo and copolymers was found to be best described when the second-order non-classical equation with time dependent rate constant approach was used. (Author)

  9. Kinetics Studies on citric acid production by gamma ray induced mutant of Aspergillus niger

    Effect of cultural pH and incubation temperature on citric acid yield and kinetic patterns of citric acid fermentation by a natural isolate of aspergillus niger as CA16 and one of its gamma ray induced mutants were studied using cane molasses as growth and fermentation substrate. Mutant strain, 277/30 gave maximum citric acid yield of 85 g/l at pH 3.5 and 28 degree centigrade in molasses medium adjusted to 16% sugar and 25% prescott salt in the medium. Parent strain, CA16 gave a maximum yield of 34 g/l at pH 4.0 and 26 degree centigrade in molasses medium adjusted to 16% sugar and 100% prescott salt in the medium. In kinetic studies, strains showed combination kinetics of citric acid fermentation where product formation is directly related to growth and cell mass and indirectly related to carbohydrate uptake

  10. Kinetic modelling of the demineralization of shrimp exoskeleton using citric acid

    Alewo Opuada AMEH

    2014-11-01

    Full Text Available Citric acid was used in the demineralization of shrimp exoskeleton and the kinetics of the demineralization process was studied. Kinetic data was obtained by demineralisation using five acid concentrations (0.1, 0.2, 0.3, 0.4 and 0.5M. The obtained kinetic data were fitted to the shrinking core model for fluid particle reactions. The concentration of calcium was found to decrease with time. For all acid concentrations considered, the best predictive mechanism for the demineralization process was determined to be Ash Layer Diffusion Control Mechanism. This was indicated by the high R2 values obtained (0.965 with 150% excess of citric acid.

  11. Kinetics of Reductive Acid Leaching of Cadmium-Bearing Zinc Ferrite Mixture Using Hydrazine Sulfate

    Zhang, Chun; Zhang, Jianqiang; Min, Xiaobo; Wang, Mi; Zhou, Bosheng; Shen, Chen

    2015-09-01

    The reductive acid leaching kinetics of synthetic cadmium-bearing zinc ferrite was investigated, and the influence of reaction temperature, sulfuric acid and hydrazine sulfate were studied. The results illustrated that an increase in the reaction temperature, initial sulfuric acid and hydrazine sulfate significantly enhanced the extraction efficiencies of cadmium, zinc and iron. The leaching kinetics were controlled by a surface chemical reaction based on a shrinking core model. The empirical equation applied was found to fit well with the kinetics analysis; the leaching processes of cadmium, zinc and iron were similar and the activation energies were 79.9 kJ/mol, 77.9 kJ/mol and 79.7 kJ/mol, respectively. The apparent orders of cadmium-bearing zinc ferrite dissolution with respect to sulfuric acid concentration were 0.83, 0.83 and 0.84 for Cd, Zn and Fe, respectively.

  12. Affinity and kinetics study of anthranilic acids as HCA2 receptor agonists.

    van Veldhoven, Jacobus P D; Liu, Rongfang; Thee, Stephanie A; Wouters, Yessica; Verhoork, Sanne J M; Mooiman, Christiaan; Louvel, Julien; IJzerman, Adriaan P

    2015-07-15

    Structure-affinity relationship (SAR) and structure-kinetics relationship (SKR) studies were combined to investigate a series of biphenyl anthranilic acid agonists for the HCA2 receptor. In total, 27 compounds were synthesized and twelve of them showed higher affinity than nicotinic acid. Two compounds, 6g (IC50=75nM) and 6z (IC50=108nM) showed a longer residence time profile compared to nicotinic acid, exemplified by their kinetic rate index (KRI) values of 1.31 and 1.23, respectively. The SAR study resulted in the novel 2-F, 4-OH derivative (6x) with an IC50 value of 23nM as the highest affinity HCA2 agonist of the biphenyl series, although it showed a similar residence time as nicotinic acid. The SAR and SKR data suggest that an early compound selection based on binding kinetics is a promising addition to the lead optimization process. PMID:25737085

  13. Dissolution kinetics of nickel laterite ore using different secondary metabolic acids

    S. Sahu

    2011-06-01

    Full Text Available The dissolution kinetics of nickel laterite ore in aqueous acid solutions of three metabolic acids, i.e., citric acid, oxalic acid and acetic acid were investigated in a batch reactor individually. It was determined that experimental data comply with a shrinking core model. The diffusion coefficients for citric acid, oxalic acid and acetic acid were found to be 1.99×10-9 cm²/s, 2.59×10-8 cm²/s and 1.92×10-10 cm²/s respectively. The leaching ability of each acid was observed and it was found that oxalic acid was better than the other two.

  14. Kinetics and mechanism of the oxidation of formic and oxalic acids by benzyltrimethylammonium dichloroiodate

    Poonam Gupta; Seema Kothari

    2001-04-01

    The oxidation of formic and oxalic acids by benzyltrimethylammonium dichloroiodate (BTMACI), in the presence of zinc chloride, leads to the formation of carbon dioxide. The reaction is first order with respect to BTMACI, zinc chloride and organic acid. Oxidation of deuteriated formic acid indicates the presence of a kinetic isotope effect. Addition of benzyltrimethylammonium chloride enhances the rate. It is proposed that the reactive oxidizing species is [(PhCH2Me3N)+ (IZn2Cl6)−]. Suitablemechanisms have been proposed.

  15. Kinetics of oxidation of ethyldigol by vanadium(V) in aqueous acidic medium

    The kinetics of oxidation of ethyldigol by vanadium(V) in aqueous acidic medium has been carried out. The reaction is first order with respect to vanadium(V) and the substrate and is acid catalysed. Hammett acidity function (H0) and Bunnett hypothesis have been applied. The formation of free radicals during the course of the reaction has been indicated. A probable reaction mechansim is proposed. (Author)

  16. Kinetic theory of the shear viscosity of a strongly coupled classical one-component plasma

    We present an approximation to the linearized collision operator or memory function of the exact kinetic equation obeyed by the correlation function of the phase-space density of a classical one-component plasma. This approximate collision operator generalizes the well known Balescu-Guernsey-Lenard (BGL) operator to finite wavelengths, finite frequencies, and finite coupling constants. It, moreover, satisfies the necessary symmetry relations, leads to appropriate conservation laws, and fulfills its first sum rule exactly. Next we use this operator to compute the shear viscosity eta for a series of coupling constants spanning the whole fluid phase. For weak coupling we make contact with the BGL theory, while for strong coupling we confirm, at least qualitatively, the results of Vieillefosse and Hansen, who predicted a minimum in eta as a function of temperature. We also demonstrate the important role played by the sum rules in the quantitative evaluation of a transport coefficient such as eta

  17. Carbon-14 kinetic isotope effect in the decarbonylation of lactic acid [1-14C

    The carbon-14 kinetic isotope effect for the decarbonation of lactic acid[1-14C] in sulfuric acid has been measured in the temperature interval of 20-90 deg C. The experimental values of (k12C/k14C) are compared with the theoretical 14C kinetic isotope effect calculated assuming that one carbon-oxygen stretching vibration is lost in the rate-determining step. The discrepancy between experimentally observed temperature dependence of the 14C kinetic isotope effect and the theoretical one is explained by the possible side reactions wich change the apparent degrees of decarbonylation and isotopic composition of CH3CHOHCOOH[1-14C] used in experiments aiming at the determination of carbon-14 kinetic isotope effect in the decarbonylation process itself. (author) 6 refs.; 1 tab

  18. Effect of Ascorbic Acid on the Degradation of Cyanocobalamin and Hydroxocobalamin in Aqueous Solution: A Kinetic Study

    Ahmad, Iqbal; Qadeer, Kiran; Zahid, Saima; SHERAZ, MUHAMMAD ALI; Ismail, Tehmina; Hussain, Waqar; Ansari, Izhar Ahmad

    2014-01-01

    The degradation kinetics of 5 × 10−5 M cyanocobalamin (B12) and hydroxocobalamin (B12b) in the presence of ascorbic acid (AH2) was studied in the pH range of 1.0–8.0. B12 is degraded to B12b which undergoes oxidation to corrin ring cleavage products. B12b alone is directly oxidized to the ring cleavage products. B12 and B12b in degraded solutions were simultaneously assayed by a two-component spectrometric method at 525 and 550 nm without interference from AH2. Both degrade by first-order kin...

  19. RESEARCH ON THE POLYCONDENSATION KINETICS OF ω-AMINO-ACIDS

    WANG Baoren; SHI Manli; QIAN Chunqing

    1983-01-01

    In our previous report, it was discovered that the polycondensation of 9-amino-nonanoic acid follows second order from the beginning up to the extent of reaction, p, around 99%, and after which the reaction changes rapidly to third order. In this paper, we wish to report that this change of the reaction order from second to third occurred also in the polycondensation of 6aminocaproic acid and 11-amino-undecanoic acid. The transition region lay again at p around 99%.It may be concluded that this is a general rule in the polycondensation of the ω-amino-acids (monomers of the A-B type), and the controversial results that appeared in the literature may be cleared up by our experiments.

  20. Reaction Kinetics Between Acetic Acid and Ag2+

    2008-01-01

    <正>The application of the salt-free reagents in the spent fuel reprocessing process has been investigated so much in the last years. Preferable result was obtained in the application of acetohydroxamic acid in the

  1. Conjugated Linoleic Acid Production by Bifidobacteria: Screening, Kinetic, and Composition

    Raimondi, Stefano; Amaretti, Alberto; Leonardi, Alan; Quartieri, Andrea; Gozzoli, Caterina; Rossi, Maddalena

    2016-01-01

    Conjugated linoleic acids (CLA) are positional and geometric isomers of linoleic acid involved in a number of health aspects. In humans, CLA production is performed by gut microbiota, including some species of potential probiotic bifidobacteria. 128 strains of 31 Bifidobacterium species were screened with a spectrophotometric assay to identify novel CLA producers. Most species were nonproducers, while producers belonged to B. breve and B. pseudocatenulatum. GC-MS revealed that CLA producer st...

  2. Optimization of Process of Methacrylic Acid Obtaining by Aldol Condensation of Propionic Acid with Formaldehyde Using a Kinetic Model

    Nebesnyi, Roman; Ivasiv, Volodymyr; Dmytruk, Yulia; Lapychak, Nazar

    2013-01-01

    Methacrylic acid is widely used industrial monomer. An alternative method of its obtaining is aldol condensation of propionic acid with formaldehyde in the gas phase. It has been found that catalyst based on oxides of boron and phosphorus and promoted by oxide of tungsten is effective for this process. The purpose of this work is to find out optimal parameters of this process (temperature and contact time) using a kinetic model. The optimal parameters of this process have been found and techn...

  3. Kinetics and mechanism of the oxidation of some -hydroxy acids by hexamethylenetetramine-bromine

    Dimple Garg; Seema Kothari

    2004-11-01

    The oxidation of lactic acid, mandelic acid and ten monosubstituted mandelic acids by hexamethylenetetramine-bromine (HABR) in glacial acetic acid, leads to the formation of the corresponding oxoacid. The reaction is first order with respect to each of the hydroxy acids and HABR. It is proposed that HABR itself is the reactive oxidizing species. The oxidation of -deuteriomandelic acid exhibits the presence of a substantial kinetic isotope effect (/ = 5.91 at 298 K). The rates of oxidation of the substituted mandelic acids show excellent correlation with Brown’s + values. The reaction constants are negative. The oxidation exhibits an extensive cross conjugation between the electron-donating substituent and the reaction centre in the transition state. A mechanism involving transfer of a hydride ion from the acid to the oxidant is postulated.

  4. Kinetic stability of indium(3) complexes with azaporphyrins in aqueous sulfuric acid

    Kinetic stability of octaphenyltetraazaporphynatochloroindium(3) and 3,7,13,17-tetramethyl-2,8,12,18-tetrabutyl-5,15-diazaporphynatochloroindium (3)= (ClInDAP) in aqueous 90-98% sulfuric acid was studied by the method of spectrophotometric titration. Kinetic parameters of solvo-protolytic dissociation of indium complexes were determined, the reaction mechanism being suggested. The state of ClInDAP in proton-donor medium was studied by the method of absorption spectroscopy and it was shown that two mesoatoms of nitrogen enter the interaction in series. Dissociation constants of the acid forms formed were determined

  5. Dissolution kinetics of nickel ferrite in amino poly carboxylic acids

    Nickel ferrite is one of the important corrosion products of PHWR's where Monel and carbon steel are used as the constructional materials in the primary heat transport system. The dissolution of synthetically prepared nickel ferrite was studied in low concentrations (< 10 mmol/l) of HEDTA, DTPA, NTA and HIDA. The dependence of the dissolution rate on the ligand concentration was found to be langmuirian in all these cases. The effect of the addition of low concentrations of citric acid, oxalic acid, ascorbic acid and Fe(II)-ligand complex, individually, to each of the above chelating agents was also studied. The effect of pH and temperature on the dissolution rate was determined. (author)

  6. Kinetic Model of Biomass Pyrolysis Based on Three-component Independent Parallel First-order Reactions

    王新运; 万新军; 陈明强; 王君

    2012-01-01

    The pyrolysis behavior of two kinds of typical biomass (pine wood and cotton stalk) was studied in nitrogen atmosphere at various heating rates by thermogravimetric analysis (TGA).The pyrolysis process can be divided into three stages:evolution of moisture (<200 ℃),devolatilization (200~400 ℃) and carbonization (>400 ℃).The comparison of DTG curves of two biomass materials show that the higher the hemicellulose content of biomass,the more evident the shoulder peak of DTG curve.The weight loss process of two materials was simulated by the kinetic model assuming cellulose,hemicellulose and lignin pyrolyzing independently and in parallel,obeying first-order reactions.The pyrolysis kinetic parameters corresponding to the three components were estimated by the nonlinear least square algorithm.The results show that their fitting curves are in good agreement with the experimental data.Their activation energy values for pine wood and cotton stalk are in the range of 188~215,90~102,29~49 and 187~214,95~101,30~38 kJ/mol,respectively.The corresponding pre-exponential factors are in the range of 1.8×1015~2.0×1016,1.6×107~7.1×108,9.3×101~l.5×103 and 1.2× 1015~6.7×1017,1.2× 108~1.4×109,1.4× 102~4.6× 102 min-1,respectively.In addition,the activation energy of cellulose and lignin increased and their contributions to volatile tended to fall,whereas the activation energy of herricellulose decreased and its contribution to volatile tended to rise with increasing of heating rate.

  7. Conjugated Linoleic Acid Production by Bifidobacteria: Screening, Kinetic, and Composition

    Amaretti, Alberto; Leonardi, Alan; Quartieri, Andrea; Gozzoli, Caterina; Rossi, Maddalena

    2016-01-01

    Conjugated linoleic acids (CLA) are positional and geometric isomers of linoleic acid involved in a number of health aspects. In humans, CLA production is performed by gut microbiota, including some species of potential probiotic bifidobacteria. 128 strains of 31 Bifidobacterium species were screened with a spectrophotometric assay to identify novel CLA producers. Most species were nonproducers, while producers belonged to B. breve and B. pseudocatenulatum. GC-MS revealed that CLA producer strains yielded 9cis,11trans-CLA and 9trans,11trans-CLA, without any production of other isomers. Hydroxylated forms of LA were absent in producer strains, suggesting that the myosin-cross-reactive antigen (MCRA) protein that exerts hydratase activity is not involved in LA isomerization. Moreover, both CLA producer and nonproducer species bear a MCRA homologue. The strain B. breve WC 0421 was the best CLA producer, converting LA into 68.8% 9cis,11trans-CLA and 25.1% 9trans,11trans-CLA. Production occurred mostly during the lag and the exponential phase. For the first time, production and incorporation of CLA in biomass were assessed. B. breve WC 0421 stored CLA in the form of free fatty acids, without changing the composition of the esterified fatty acids, which mainly occurred in the plasmatic membrane. PMID:27429985

  8. Phase separation kinetic studies for uranium recovery from phosphoric acid by solvent extraction

    Wet process phosphoric acid (WPA) contains uranium in the range 80-120 mg/LU3O8 while in the Merchant Grade Acid (MGA) it is in the range 220-240 mg/L .Based on the experimental work, a two cycle solvent extraction process for uranium separation from phosphoric acid has been developed at REDS and patented. While the equilibrium extraction behaviour and reaction mechanisms have been studied, the kinetic aspect of uranium extraction from phosphoric acid with particular reference to rate of mass transfer and phase disengagement time has not been studied

  9. Kinetics of Hydrochloric Acid Leaching of Titanium from Titanium-Bearing Electric Furnace Slag

    Zheng, Fuqiang; Chen, Feng; Guo, Yufeng; Jiang, Tao; Travyanov, Andrew Yakovlevich; Qiu, Guanzhou

    2016-05-01

    The hydrochloric acid leaching of titanium from titanium-bearing electric furnace slag was investigated under different experimental conditions. The results indicate that particle size, hydrochloric acid concentration and reaction temperature were of significance to the leaching kinetics. Specifically, reaction temperature was the most important factor followed by hydrochloric acid concentration and particle size. The shrinking core model was used to describe the leaching process which was controlled by surface chemical reaction. The kinetic equation was obtained and the activation energy was found to be 43.16 kJ/mol. Iron and calcium species were almost completely dissolved in the acid when the extraction degree of titanium reached 99.84%. MgO (19.34 wt.%) and Al2O3 (32.45 wt.%) in the spinel were still in the leaching residue and SiO2 (43.53 wt.%) in the form of quartz remained in the leaching residue.

  10. Degradation Kinetics of Xylose and Glucose in Hydrolysate Containing Dilute Sulfuric Acid

    亓伟; 张素平; 许庆利; 任铮伟; 颜涌捷

    2008-01-01

    In preparation of fuel alcohol from biomass as feedstock,hydrolysis with dilute acid as catalyst iS one way to produce fermentable saccharide,xylose and glucose.However,the acid is also the catalyst in degradation of xylose and glucose and the yield of sacchride is dependent on the kinetic behaviors of saccharide.The degradation kinetics of xylose and glucose in the hydrolysate Was investigated under the conventional process conditions of hydrogen ion concentration from O.05 to 0.2 mol/L and temperature from 150 to 200℃.With a numerical calculation method,the kinetic parameters Were estimated,and the activation energy of xylose and glucose in the degradation reaction was obtained.The kinetic equations correlating the effect of hydrogen ion concentration on the rate constants of degradation reaction were established.Comparison between the calculated results from the equations and experimental ones proved that the established kinetic model could satisfactorily predict the degradation behavior of xylose and glucose in the acidic hydrolysate.

  11. Kinetics, intermediates and acute toxicity of arsanilic acid photolysis.

    Zhu, Xiang-Dong; Wang, Yu-Jun; Liu, Cun; Qin, Wen-Xiu; Zhou, Dong-Mei

    2014-07-01

    Arsanilic acid (4-amino phenyl arsenic acid, ASA) is widely used in poultry production as feed additives, while most of ASA in the feed is excreted in the animal manure and released into the environment. However, the environmental behaviors of ASA were not well understood. In the present study, the photolysis behaviors of ASA and the toxicity of its metabolites to luminescent bacterium were studied. The results showed that ASA could be photodegraded and this process was strongly affected by solution pH, humic acid and dissolved oxygen. Upon UV irradiation for 360 min, ASA could be completely eliminated, but the reduction of total organic carbon (TOC) was not significant. In addition, NH4(+) ions and inorganic arsenic including arsenite and arsenate were identified as the predominant end-products. The conversion of ASA included both direct and indirect photolysis involving radicals, and its possible photolysis pathways were proposed on the basis of the identified intermediates. Unfortunately, higher adverse effects of the conversion products of ASA on bacteria were observed during the photolysis reaction. The results of present study might be helpful for assessing the environmental persistence and risks of ASA. PMID:24405966

  12. 2.2. The kinetics of hydrochloric-acid decomposition of calcined borosilicate ore

    Present article is devoted to kinetics of hydrochloric-acid decomposition of calcined borosilicate ore. The experimental data of dependence of hydrochloric-acid decomposition of calcined borosilicate ore for boron oxide extraction on temperature (30-95 deg C) and process duration (15-60 min) were considered. It was defined that at temperature increasing the boron oxide extraction increases from 28.9 till 53.2%. The constants of decomposition rate of calcined ore were calculated.

  13. Effect of retinoic acid on cell proliferation kinetics and retinoic acid receptor expression of colorectal mucosa

    Hong-Bo Wei; Xiao-Yan Han; Wei Fan; Gui-Hua Chen; Ji-Fu Wang

    2003-01-01

    AIM: To investigate the effect of retinoic acid (RA) on cell proliferation kinetics and retinoic acid receptor (RAR)expression of colorectal mucosa.METHODS:One hundred sixty healthy male Wistar rats were randomly divided into 4 groups. Rats in groups Ⅰ and Ⅱ were subcutaneously injected with dimethylhydrazine (DMH) (20 mg/kg, once a week,) for 7 to 13 weeks, while groups Ⅲ and Ⅳ were injected with normal saline. Rats in groups Ⅱ and Ⅲ were also treated with RA (50 mg/kg,every day, orally) from 7th to 15th week, thus group Ⅳ was used as a control. The rats were killed in different batches.The expressions of proliferating cell nuclear antigen (PCNA),nucleolar organizer region-associated protein (AgNOR) and RAR were detected.RESULTS: The incidence of colorectal carcinoma was different between groupsⅠ(100 %) and Ⅱ (15 %) (P<0.01).The PCNA indices and mean AgNOR count in group Ⅱ were significantly lower than those in group Ⅰ(F=5.418 and 4.243,P<0.01). The PCNA indices and mean AgNOR count in groups Ⅰ and Ⅱ were significantly higher than those in the groups Ⅲ and Ⅳ (in which carcinogen was not used) (F=5.927and 4.348, P<0.01). There was a tendency in group Ⅰ that the longer the induction with DMH the higher PCNA index and AgNOR count expressed (F=7.634 and 6.826, P<0.05).However, there was no such tendency in groups Ⅱ, Ⅲ and Ⅳ(F=1.662 and 1.984, P>0.05). The levels of RAR in normal and cancerous tissues in groups treated with RA were significantly higher than those in groups not treated with RA (F=6.343 and 6.024, P<0.05).CONCLUSION: RA decreases the incidence of colorectal carcinoma induced by DMH. Coiorectal cancer tissue is associated with abnormal expression of PCNA, AgNOR and RAR. RA inhibits the expression of PCNA and AgNOR, and increases RAR concentration in colorectal tissues.

  14. Oxidation kinetics of crystal violet by potassium permanganate in acidic medium

    Khan, Sameera Razi; Ashfaq, Maria; Mubashir; Masood, Summyia

    2016-05-01

    The oxidation kinetics of crystal violet (a triphenylmethane dye) by potassium permanganate was focused in an acidic medium by the spectrophotometric method at 584 nm. The oxidation reaction of crystal violet by potassium permanganate is carried out in an acidic medium at different temperatures ranging within 298-318 K. The kinetic study was carried out to investigate the effect of the concentration, ionic strength and temperature. The reaction followed first order kinetics with respect to potassium permanganate and crystal violet and the overall rate of the reaction was found to be second order. Thermodynamic activation parameters like the activation energy ( E a), enthalpy change (Δ H*), free energy change (Δ G*), and entropy change (Δ S*) have also been evaluated.

  15. Kinetics of sulfuric acid decomposition of solid fluorine containing wastes of aluminium production

    The results of researches of kinetics of sulfuric acid decomposition of solid fluorine containing wastes of aluminium production were considered in this work. The apparent activation energy was determined. The rate constant and pre-exponential factor of Arrhenius equation were defined as well.

  16. Phospholipids and poly(glutamic acid)/hydrolyzed gluten: interaction and kinetics

    The effect of poly (glutamic acid) (PGA) and Hydrolyzed wheat gluten (HG) on the thermal and kinetics properties of lysophosphatidylcholine (LPC) was determined using Differential Scanning Calorimetry (DSC). A model system containing 3, 6 and 10% PGA or HG was added to 40% LPC aqueous suspension. ...

  17. Reactive extraction of lactic acid using alamine 336 in MIBK: equilibria and kinetics.

    Wasewar, Kailas L; Heesink, A Bert M; Versteeg, Geert F; Pangarkar, Vishwas G

    2002-07-17

    Lactic acid is an important commercial product and extracting it out of aqueous solution is a growing requirement in fermentation based industries and recovery from waste streams. The design of an amine extraction process requires (i) equilibrium and (ii) kinetic data for the acid-amine (solvent) system used. Equilibria for lactic acid extraction by alamine 336 in methyl-iso-butyl-ketone (MIBK) as a diluent have been determined. The extent to which the organic phase (amine +MIBK) may be loaded with lactic acid is expressed as a loading ratio, z=[HL](o)/[B](i,o). Calculations based on the stoichiometry of the reactive extraction and the equilibria involved indicated that more lactic acid is transferred to the organic phase than would be expected from the (1:1) stoichiometry of the reaction. The extraction equilibrium was interpreted as a result of consecutive formation of two acid-amine species with stoichiometries of 1:1 and 2:1. Equilibrium complexation constant for (1:1) and (2:1) has been estimated. Kinetics of extraction of lactic acid by alamine 336 in MIBK has also been determined. In a first study of its kind, the theory of extraction accompanied by a chemical reaction has been used to obtain the kinetics of extraction of lactic acid by alamine 336 in MIBK. The reaction between lactic acid and alamine 336 in MIBK in a stirred cell falls in Regime 3, extraction accompanied by a fast chemical reaction occurring in the diffusion film. The reaction has been found to be zero order in alamine 336 and first order in lactic acid with a rate constant of 1.38 s(-1). These data will be useful in the design of extraction processes. PMID:12052683

  18. Synthesis and photopolymerization kinetics of benzophenone sesamol one-component photoinitiator.

    Yang, Jinliang; Shi, Suqing; Xu, Fei; Nie, Jun

    2013-02-01

    A benzodioxole derivative, 4-(2-(benzodioxol-5-yloxy)ethoxy)benzophenone (BPC2BDO), based on 4-hydroxybenzophenone and sesamol was synthesized, and used as a one-component Type II photoinitiator. The structure of BPC2BDO was characterized by elementary analysis, APCI-MS, (1)H NMR, and (13)C NMR. The rate of decomposition (R(d)) of BPC2BDO in acetonitrile was studied by UV-Vis spectroscopy and found that R(d) was proportional to light intensity. Real-time near-IR was used to study the kinetics of photopolymerization of the photoinitiator. As the benzophenone (BP) moiety and hydrogen donor were introduced into one molecule in BPC2BDO, radicals could be generated through intra-molecular reaction due to the close vicinity of the hydrogen donor and BP, which might be faster than inter-molecular reaction. The results also showed that the rate of polymerization of acrylates was significantly higher than that of methacrylates at the same polymerization conditions; the functionality of acrylates, concentration of BPC2BDO, and light intensity affected the polymerization rate and the final conversion. PMID:23047776

  19. Asymmetric Synthesis of 1,3-Oxazolidine Derivatives with Multi-Component Reaction and Research of Kinetic Resolution

    Xiao-Wei Hong

    2015-09-01

    Full Text Available An efficient multi-component reaction to synthesize multi-substituted 1,3-oxazolidine compounds of high optical purity was described. All the products were well-characterized and the absolute configuration of one chiral center was determined. The plausible mechanism was proposed and a kinetic resolution of epoxides process was confirmed.

  20. Removal of 5-Amino-2-chlorotoluene-4-sulfonic and Chlorhydric Acids From Wastewater by Weakly Basic Resin: Equilibrium and Kinetics

    2007-01-01

    To study the adsorption of 5-Amino-2-chlorotoluene-4-sulfonic (CLT) and chlorhydric (HCl) acids from wastewater by weakly basic resin.Methods The kinetics and isotherm were studied. Thermodynamic parameters for the adsorption of acids were calculated and discussed.Results The adsorption of CLT and HCl acids followed Langmuir isotherm and the first-order kinetics model.Conclusion The adsorptive affinity of the two acids on D301R is in the order of CLT acid > HCl acid. CLT and HCl acids can be separated.

  1. Dilute Acid Hydrolysis of Cowpea Hulls: A Kinetic Study

    Chioma M. Onyelucheya

    2016-08-01

    Full Text Available In this study, dilute acid hydrolysis of cowpea hulls was carried out in two stages under the following conditions: pre-hydrolysis (4%v/v H2SO4, 121˚C, 30 minutes and hydrolysis ( at 10% and 15% v/v H2SO4,varied at different temperatures 150 oC, 160 oC, 170 oC and 180 oC for 2.5 hrs.. The substrate was characterized using both Fourier transform infrared spectroscopy and proximate analysis. The percentage lignocellulosic composition of the substrate was obtained for cellulose, hemicellulose and lignin as 34%, 14% and 4.7% respectively. Maximum glucose concentration of 8.09g was obtained using 10%v/v acid concentration at 170˚C after a reaction time of 90min. Saeman’s model gave a good fit for the experimental data. Activation energy for glucose formation using 10%v/v and 15%v/v H2SO4 was obtained as 38.28KJ and 82.204KJ respectively. From the results obtained it can be concluded that cowpea hulls can be converted to a useful product.

  2. Kinetics of acid-catalyzed aldol condensation reactions of aliphatic aldehydes

    Casale, Mia T.; Richman, Aviva R.; Elrod, Matthew J.; Garland, Rebecca M.; Beaver, Melinda R.; Tolbert, Margaret A.

    Field observations of atmospheric aerosols have established that organic compounds compose a large fraction of the atmospheric aerosol mass. However, the physical/chemical pathway by which organic compounds are incorporated into atmospheric aerosols remains unclear. The potential role of acid-catalyzed reactions of organic compounds on acidic aerosols has been explored as a possible chemical pathway for the incorporation of organic material into aerosols. In the present study, ultraviolet-visible (UV-vis) spectroscopy was used to monitor the kinetics of formation of the products of the acid-catalyzed aldol condensation reaction of a range of aliphatic aldehydes (C 2-C 8). The experiments were carried out at various sulfuric acid concentrations and a range of temperatures in order to estimate the rate constants of such reactions on sulfuric acid aerosols under tropospheric conditions. The rate constants were generally found to decrease as the chain length of the aliphatic aldehyde increased (except for acetaldehyde, which had an unusually small rate constant), increase as a function of sulfuric acid concentration as predicted by excess acidity theory, and showed normal Arrhenius behavior as a function of temperature. While the kinetic data are generally consistent with previous laboratory reports of aldehyde reactivity in various sulfuric acid media, the aldol condensation reactions involving aliphatic aldehydes do not appear fast enough to be responsible for significant transfer of organic material into atmospheric aerosols.

  3. 4-Hydroxy cinnamic acid as mushroom preservation: Anti-tyrosinase activity kinetics and application.

    Hu, Yong-Hua; Chen, Qing-Xi; Cui, Yi; Gao, Huan-Juan; Xu, Lian; Yu, Xin-Yuan; Wang, Ying; Yan, Chong-Ling; Wang, Qin

    2016-05-01

    Tyrosinase is a key enzyme in post-harvest browning of fruit and vegetable. To control and inhibit its activity is the most effective method for delaying the browning and extend the shelf life. In this paper, the inhibitory kinetics of 4-hydroxy cinnamic acid on mushroom tyrosinase was investigated using the kinetics method of substrate reaction. The results showed that the inhibition of tyrosinase by 4-hydroxy cinnamic acid was a slow, reversible reaction with fractional remaining activity. The microscopic rate constants were determined for the reaction on 4-hydroxy cinnamic acid with tyrosinase. Furthermore, the molecular docking was used to simulate 4-hydroxy cinnamic acid dock with tyrosinase. The results showed that 4-hydroxy cinnamic acid interacted with the enzyme active site mainly through the hydroxy competed with the substrate hydroxy group. The cytotoxicity study of 4-hydroxy cinnamic acid indicated that it had no effects on the proliferation of normal liver cells. Moreover, the results of effects of 4-hydroxy cinnamic acid on the preservation of mushroom showed that it could delay the mushroom browning. These results provide a comprehensive underlying the inhibitory mechanisms of 4-hydroxy cinnamic acid and its delaying post-harvest browning, that is beneficial for the application of this compound. PMID:26812105

  4. Kinetic study on the photocatalytic degradation of salicylic acid using ZnO catalyst

    The photocatalytic degradation of salicylic acid was studied by a batch process using ZnO as the catalyst on irradiation with UV light. The effect of process parameters such as pH, catalyst loading and initial concentration of salicylic acid on the extent of degradation was investigated. The degradation of salicylic acid was found to be effective in the neutral pH range. The optimum catalyst loading was observed at 2.0 g/L. The process followed first order kinetics and the apparent rate constant decreased with increase in the initial concentration of salicylic acid. The mechanism for the degradation of salicylic acid could be explained on the basis of Langmuir-Hinshelwood mechanism. The complete mineralization of salicylic acid was observed in the presence of ZnO photocatalyst. The ZnO was found to be quite stable and undergoes photocorrosion only to a negligible extent.

  5. Study of kinetics of scandium extraction by di(2-ethylhexyl)phosphoric acid

    Kinetics of extracting scandium with (2-ethylhexyl)phosphoric acid (D2EHPA) from 0.5 and 8 mol/l solutions of hydrochloric acid has been studied. At [Sc]:[D2EHPA] ratio equal to 1:2.6 and 1:3.2 equilibrium is attained in strongly acid solutions after 40 and 10 minutes periods of contacting and in weakly acid solutions after 60 and 20 minutes. At [Sc]:[D2EHPA] ratio more than 1:4.6 the equilibrium is attained for less than two minutes. The rate constant of scandium extraction by cation-exchange mechanism is 0.0293 cm/min and by solvate mechanism 0.0415 cm/min. The activation energy upon extracting from weakly acid solutions is 5.4 kcal/mol, from strongly acid solutions - 1.8 kcal/mol

  6. Kinetics of the Esterification Reaction between Pentanoic Acid and Methanol Catalyzed by Noncorrosive Cation Exchange Resin

    Sharma, M.; Toor, A. P.; R. K. Wanchoo

    2014-01-01

    Methyl pentanoate, commonly known as methyl valerate, is the methyl ester of pentanoic acid (valeric acid) with a fruity odour. Methyl pentanoate is commonly used in fragrances, beauty care, soap, laundry detergents at levels of 0.1 – 1 %. In its very pure form (purity 99.5 %) it is used as a plasticizer in the manufacture of plastics. In the present investigation, kinetics of esterification of pentanoic acid with methanol catalyzed by heterogeneous catalyst in a batch-type reactor is reporte...

  7. Kinetics of acetic acid synthesis from ethanol over a Cu/SiO2 catalyst

    Voss, Bodil; Schjødt, Niels Christian; Grunwaldt, Jan-Dierk;

    2011-01-01

    The dehydrogenation of ethanol via acetaldehyde for the synthesis of acetic acid over a Cu based catalyst in a new process is reported. Specifically, we have studied a Cu on SiO2 catalyst which has shown very high selectivity to acetic acid via acetaldehyde compared to competing condensation routes....... The dehydrogenation experiments were carried out in a flow through lab scale tubular reactor. Based on 71 data sets a power law kinetic expression has been derived for the description of the dehydrogenation of acetaldehyde to acetic acid. The apparent reaction order was 0.89 with respect to water and...

  8. New method for spectrophotometric determination of quinones and barbituric acid through their reaction. A kinetic study

    Medien, H. A. A.

    1996-11-01

    A new and sensitive spectrophotometric method is described for the determination of p-benzoquinone, p-chloranil and 1.4-naphthoquinone. The method is based on the reaction between quinones and barbituric acid, by which a color is developed with maximum absorption between 485 and 555 nm in 50% methyl alcohol-water mixture. The absorption of the product obeys Beer's law within the concentration range 0.025-05 mM of orginal quinone. The kinetics of the reaction between p-benzoquinone and barbituric acid was studied in a range of methyl alcohol-water mixtures. The reaction follows overall second order kinetics, first order in each of the reactants. The rate increases with increasing dielectric constant. The method was applied for determination of barbituric acid with p-benzoquinone in the concentration range of 0.025-0.345 mM. Other barbiturates do not interfere.

  9. β-methyl-15-p-iodophenylpentadecanoic acid metabolism and kinetics in the isolated rat heart

    The use of 15-p-iodophenyl-β-methyl-pentadecanoic acid (βMe-IPPA) as an indicator of long chain fatty acid (LCFA) utilization in nuclear medicine studies was evaluated in the isolated, perfused, working rat heart. Time courses of radioactivity (residue curves) were obtained following bolus injections of both βMe-IPPA and its straight chain counterpart 15-p-iodophenyl-pentadecanoic acid (IPPA). IPPA kinetics clearly indicated flow independent impairment of fatty acid oxidation caused by the carnitine palmitoyltransferase I inhibitor 2[5(4-chlorophenyl)pentyl]oxirane-2-carboxylate (POCA). In contrast, βMe-IPPA kinetics were insensitive to changes in fatty acid oxidation rate and net utilization of long chain fatty acid. Analysis of radiolabeled species in coronary effluent and heart homogenates showed the methylated fatty acid to be readily incorporated into complex lipids but a poor substrate for oxidation. POCA did not significantly alter metabolism of the tracer, suggesting that the tracer is poorly metabolized beyond βMe-IPPA-CoA in the oxidative pathway. (orig.)

  10. Kinetics of bromide catalysed oxidation of dextrose by cerium (IV) in aqueous sulphuric acid solution

    Kinetics of bromide catalysed oxidation of dextrose by CeIV in aqueous sulphuric acid medium show first order dependence each in dextrose and cerium(IV). The reaction rate decreases on increasing the concentration of hydrogen ion. The increase in [HSO4-] or [SO42-] decreases the rate. The bromide ion shows positive catalytic effect on the reaction rate. The value of activation energy has been calculated and a suitable mechanism confirming to the kinetic data is proposed. (author). 3 refs., 3 tabs

  11. Reaction kinetics of free fatty acids esterification in palm fatty acid distillate using coconut shell biochar sulfonated catalyst

    Hidayat, Arif; Rochmadi, Wijaya, Karna; Budiman, Arief

    2015-12-01

    Recently, a new strategy of preparing novel carbon-based solid acids has been developed. In this research, the esterification reactions of Palm Fatty Acid Distillate (PFAD) with methanol, using coconut shell biochar sulfonated catalyst from biomass wastes as catalyst, were studied. In this study, the coconut shell biochar sulfonated catalysts were synthesized by sulfonating the coconut shell biochar using concentrated H2SO4. The kinetics of free fatty acid (FFA) esterification in PFAD using a coconut shell biochar sulfonated catalyst was also studied. The effects of the mass ratio of catalyst to oil (1-10%), the molar ratio of methanol to oil (6:1-12:1), and the reaction temperature (40-60°C) were studied for the conversion of PFAD to optimize the reaction conditions. The results showed that the optimal conditions were an methanol to PFAD molar ratio of 12:1, the amount of catalyst of 10%w, and reaction temperature of 60°C. The proposed kinetic model shows a reversible second order reaction and represents all the experimental data satisfactorily, providing deeper insight into the kinetics of the reaction.

  12. Kinetics of sulfuric acid leaching of cadmium from Cd-Ni zinc plant residues.

    Safarzadeh, Mohammad Sadegh; Moradkhani, Davood; Ojaghi-Ilkhchi, Mehdi

    2009-04-30

    Cd-Ni filtercakes are produced continuously at the third purification step in the electrolytic production of zinc in the National Iranian Lead and Zinc Company (NILZ) in northwestern Iran. In this research, the dissolution kinetics of cadmium from Cd-Ni residues produced in NILZ plant has been investigated. Hence, the effects of temperature, sulfuric acid concentration, particle size and stirring speed on the kinetics of cadmium dissolution in sulfuric acid were studied. The dissolution kinetics at 25-55 degrees C and tshrinking core model, with inter-diffusion of cadmium and sulfate ions through the porous region of alloying layer (Cd(5)Ni, Cd(2)Ni(1.9) and Cd(10)Cu(3)) as the rate determining step. This finding is in accordance with the apparent activation energy (E(a)) of 13.363 kJ/mol and a linear relationship between the rate constant and the reciprocal of squared particle size. Arrhenius constant was calculated as 6.3942 min(-1). The order of reaction with respect to sulfuric acid concentration, solid/liquid ratio and particle size were also achieved. The rate of reaction at first 5 min based on diffusion-controlled process can be expressed by a semi-empirical equation as:It was determined that the dissolution rate increased with increasing sulfuric acid concentration and decreasing particle size. PMID:18755541

  13. Kinetic studies for sorption of some metal ions from aqueous acid solutions onto TDA impregnated resin

    Kinetic studies for sorption of uranium, thorium and cobalt ions from hydrochloric acid solutions using tri-dodecyl amine (TDA) loaded on Amberlite XAD4 (polystyrene resin supplied by Rohm and Haas) using the batch technique, have been evaluated and assessed. Analysis of the respective data in accordance with three kinetic models revealed that the particle diffusion mechanism is the rate determining step, and the sorption for each metal ion on the impregnated sorbent follows the first order reversible kinetics. Values of the first order rate constants, rate constants of intraparticle transport, and the particle diffusion coefficients for the studied ions were determined. Sorption isotherms, which have been evaluated from the distribution coefficients for these ions, were found in good fit with the Langmuir and Freundlich isotherms. (author)

  14. Oxidation of glycylglycine by ferricyanide in acid medium: Kinetics and mechanism

    Krishna K. Yerneni

    2015-12-01

    Full Text Available The oxidative degradation of glycylglycine (GlyGly to formic acid, ammonium ion, and carbon dioxide occurs when it reacts with ferricyanide in acid medium, which has been studied spectrophotometrically at 303 nm at constant temperature. Kinetic runs have been performed under a pseudo-first-order condition of [GlyGly]0 >> [ferricyanide]0. The experimental rate law obtained for the redox reaction is: rate = kı [$ \\text{Fe(CN}^{3 - }_{6} $] [GlyGly]x [H+]y[Pd(II]0, where x and y are fractional orders. Effects of ionic strength and dielectric constant are also investigated. Activation parameters have been evaluated using Arrhenius and Eyring plots. A probable mechanism has been proposed and the derived rate law is consistent with the kinetic data.

  15. Kinetic investigation of the immobilization of chromotropic acid derivatives onto anion exchange resin

    Savić Jasmina

    2007-01-01

    Full Text Available The adsorption kinetics of pyrazol- (РАСА and imidazol-azo-chromo-tropic acid (IACA onto Dowex 1-X8 resin, as a function of the dye concentration and temperature were investigated at pH 4.5. The pseudo-first- and second-order kinetic models and intraparticle diffusion model were used to describe the obtained kinetic data. The adsorption rate constants were found to be in the order of magnitude 10-2 min-1 for all of the used kinetics models. The adsorption capacity increases with increasing initial dye concentration. The study of adsorption kinetics at different temperatures (in the range from 5 to 25 °C reveals an increase in the rate of adsorption and adsorption capacity with increasing temperature. The activation energy (in the case of РАСА 16.6 kJ/mol, and for IACA 11.3 kJ/mol was determined using the Arrhenius dependence. Electrostatic interactions between the dye and resin beads were shown to be the adsorption mechanism.

  16. Lewis acidic metal catalysed organic transformations by designed multi-component structures and assemblies

    Afsar Ali; Amit P Singh; Rajeev Gupta

    2010-05-01

    This paper presents the recent developments in designing multi-component structures including metal-organic frameworks containing Lewis acidic metal ions. The emphasis has been given to understand the design elements adopted to synthesize such structures bearing Lewis acidic metal ion. Further, few important Lewis acidic metal catalysed organic transformation reactions have been discussed demonstrating the importance of such materials for practical purposes.

  17. Kinetic Modelling for Flavonoid Recovery from Red Grape (Vitis vinifera) Pomace with Aqueous Lactic Acid

    Katerina Tzima; Stamatina Kallithraka; Yorgos Kotseridis; Dimitris P. Makris

    2014-01-01

    This study was undertaken with the aim of establishing a correlation between the extraction yield in total flavonoids from red grape pomace and the extraction temperature, using 0.5% (w/v) aqueous lactic acid as the solvent system. Extraction of flavonoids was found to obey second-order kinetics, and on such a basis, the yield in total flavonoids at saturation could be very effectively determined and correlated with temperature using non-linear regression. The results indicated that the extr...

  18. Kinetics of Sawdust Hydrolysis with Dilute Hydrochloric Acid and Ferrous Chloride

    袁传敏; 颜涌捷; 任铮伟; 李庭琛; 曹建勤

    2004-01-01

    With dilute hydrochloric acid as catalyst and promoted by ferrous chloride, hydrolysis of waste sawdust to produce monosaccharides was conducted by using an one-step method in a batch-wise operation reactor. Based on the model of first order consecutive irreversible reactions, the kinetics equation incorporating the term of catalyst concentration was obtained that is suitable for describing the hydrolysis of sawdust. Activation energies were calculated for hydrolysis of sawdust and decomposition of monosaccharides.

  19. Adsorption of rhodamine B by acid activated carbon-Kinetic, thermodynamic and equilibrium studies

    Shanmugam Arivoli; M. Thenkuzhali; P. Martin Deva Prasath

    2009-01-01

    A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing Rhodamine B (RDB). The parameters studied include agitation time, initial dye concentration, carbon dose, pH and temperature. The adsorption followed first order kinetics and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm) obtained from the Langmuir isotherm p...

  20. Kinetics and mechanism of sphalerite leaching by sodium nitrate in sulphuric acid solution

    Sokić M.; Marković B.; Matković V.; Živković D.; Štrbac N.; Stojanović J.

    2012-01-01

    Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time ...

  1. Kinetic energy releases of small amino acids upon interaction with keV ions

    Bari, S.; Alvarado, F.; Postma, J.; Sobocinski, P.; Hoekstra, R.; Schlatholter, T. [Groningen Univ., KVI Atomic Physics (Netherlands); Schlatholter, T. [Universites P. et M. Curie and D. Diderot, INSP, CNRS UMR 75-88, 75 - Paris (France)

    2009-01-15

    In chromatin, DNA is tightly packed into one complex together with histone and non-histone proteins. These proteins are known to protect the DNA against indirect and to some extent even direct radiation damage. Radiation action upon amino acids is thus one of the primary steps in biological radiation action. In this paper we investigate the ionization and fragmentation of the gas-phase amino acids glycine, alanine and valine upon interaction with keV {alpha}-particles. High resolution coincidence time-of-flight mass spectrometry is used to determine the dominant fragmentation channels as well as fragment kinetic energies. (authors)

  2. Kinetics and mechanism of oxidation of acetanilide by quinquevalent vanadium in acid medium

    The kinetics of the oxidation of acetanilide with vanadium(V) in sulphuric acid medium at constant ionic strength has been studied. The reaction is first order with oxidant. The order of reaction in acetanilide varies from one to zero. The reaction follows an acid catalyzed independent path, exhibiting square dependence in H+. A Bunnett plot indicates that the water acts as a nucleophile. The thermodynamic parameters have been computed. A probable reaction mechanism and rate law consistent with these data are given. (Author)

  3. Kinetics and Thermodynamics of Oil Extraction from Sun ower Seeds in the Presence of Aqueous Acidic

    TOPALLAR, Hüseyin

    2000-01-01

    Oil extraction was performed in aqueous HCl, H2SO4 and H3PO4 solutions with n-hexane (C6H14) at 30, 40, 50 and 60 oC using 10 gr of sunflower seeds over 1 h with 10-min. sampling intervals. The optimum acid concentration was wt. 10% for each acid, and the highest oil yield was obtained in the extraction procedure with n-hexane containing H2SO4. The extraction process was observed with regard to the percent oil yield versus time, and the reaction order was found to be first-order kinetics by t...

  4. Kinetic energy releases of small amino acids upon interaction with keV ions

    In chromatin, DNA is tightly packed into one complex together with histone and non-histone proteins. These proteins are known to protect the DNA against indirect and to some extent even direct radiation damage. Radiation action upon amino acids is thus one of the primary steps in biological radiation action. In this paper we investigate the ionization and fragmentation of the gas-phase amino acids glycine, alanine and valine upon interaction with keV α-particles. High resolution coincidence time-of-flight mass spectrometry is used to determine the dominant fragmentation channels as well as fragment kinetic energies. (authors)

  5. Thermodynamics and kinetics of lutetium extraction with HEH(EHP) in hydrochloric acid medium

    DONG Jinshi; XU Yang; WANG Liangshi; HUANG Xiaowei; LONG Zhiqi; WU Shengxi

    2016-01-01

    Solvent extraction has been the most widely used technique for rare earths separation. In this study, thermodynamics and kinetics of lutetium extraction with HEH (EHP) in hydrochloric acid medium were investigated. The extraction mechanism and the relevant parameters were determined by experiment research which can guide the practical extraction process. The data indicated that chloride ion had no effect on lutetium extraction, the rate constant increased when stirring speed was enhanced. Effects of temperature, HEH (EHP) concentration, acidity, and chloride concentration were also studied. Thickness of the diffusion film was also calculated to be 4.66×10–3 cm at 150 r/min.

  6. Equilibrium and Kinetic Studies on the Adsorption of Acid Yellow 36 Dye by Pinecone

    Amir Sheikh Mohammadi

    2013-11-01

    Full Text Available Background & Aims of the Study: Dyes have significant role in environmental problems, due to their toxic effects on the food chain and sources of water. The purpose of this research was to study the adsorption of acid yellow 36 dye onto pinecone using batch system. Materials & Methods: This research was performed at laboratory scale and batch system. Equilibrium isotherms were modeled using Langmuir, Freundlich, and D-R models. Also kinetic studies were done by three models of pseudo first order, pseudo second order, and intra-particle diffusion. Results: The maximum adsorption was achieved at pH 5.0, adsorbent dose 0.7 g/l and contact time 20 min. The equilibrium adsorption capacity (mg/g increased with increasing initial dye concentration. The Langmuir model (R2=0.99 provided the best fit for the experimental data. The adsorption kinetics were studied and best fit was achieved by pseudo- second order model (R2= 0.96. Conclusions: According to the results obtained of equilibrium and kinetic studies on the adsorption of acid yellow 36, pinecone can be a suitable and efficient adsorbent in the removal of yellow acid 36 dye from industrial wastewater.

  7. Kinetics of gas phase formic acid decomposition on platinum single crystal and polycrystalline surfaces

    Detwiler, Michael D.; Milligan, Cory A.; Zemlyanov, Dmitry Y.; Delgass, W. Nicholas; Ribeiro, Fabio H.

    2016-06-01

    Formic acid dehydrogenation turnover rates (TORs) were measured on Pt(111), Pt(100), and polycrystalline Pt foil surfaces at a total pressure of 800 Torr between 413 and 513 K in a batch reactor connected to an ultra-high vacuum (UHV) system. The TORs, apparent activation energies, and reaction orders are not sensitive to the structure of the Pt surface, within the precision of the measurements. CO introduced into the batch reactor depressed the formic acid dehydrogenation TOR and increased the reaction's apparent activation energies on Pt(111) and Pt(100), consistent with behavior predicted by the Temkin equation. Two reaction mechanisms were explored which explain the formic acid decomposition mechanism on Pt, both of which include dissociative adsorption of formic acid, rate limiting formate decomposition, and quasi-equilibrated hydrogen recombination and CO adsorption. No evidence was found that catalytic supports used in previous studies altered the reaction kinetics or mechanism.

  8. Kinetics and mechanism of N-chlorosaccharin oxidation of malic acid

    Sanjay Kumar Singh

    2010-12-01

    Full Text Available Kinetic study of N-chlorosaccharin (NCSA oxidation of malic acid (MA in aqueous acetic acid medium in presence of perchloric acid has been investigated. The reactions exhibit first-order dependency in oxidant and HClO4 while order varies from one to zero in substrate. The reactions are acid catalyzed and retarded by the addition of saccharin, a byproduct of reaction. The rate of oxidation decreases with decrease in dielectric constant of the medium. The effect of temperature on the reaction has been investigated in the temperature range 313-333 K. The stochiometric studies revealed 1:1 mole ratio. Various thermodynamic parameters have been computed and a possible operative mechanism is proposed.

  9. Kinetic Study and Mathematical Model of Hemimorphite Dissolution in Low Sulfuric Acid Solution at High Temperature

    Xu, Hongsheng; Wei, Chang; Li, Cunxiong; Deng, Zhigan; Li, Minting; Li, Xingbin

    2014-10-01

    The dissolution kinetics of hemimorphite with low sulfuric acid solution was investigated at high temperature. The dissolution rate of zinc was obtained as a function of dissolution time under the experimental conditions where the effects of sulfuric acid concentration, temperature, and particle size were studied. The results showed that zinc extraction increased with an increase in temperature and sulfuric acid concentration and with a decrease in particle size. A mathematical model able to describe the process kinetics was developed from the shrinking core model, considering the change of the sulfuric acid concentration during dissolution. It was found that the dissolution process followed a shrinking core model with "ash" layer diffusion as the main rate-controlling step. This finding was supported with a linear relationship between the apparent rate constant and the reciprocal of squared particle radius. The reaction order with respect to sulfuric acid concentration was determined to be 0.7993. The apparent activation energy for the dissolution process was determined to be 44.9 kJ/mol in the temperature range of 373 K to 413 K (100 °C to 140 °C). Based on the shrinking core model, the following equation was established:

  10. Wet oxidation of glycerol into fine organic acids: catalyst selection and kinetic evaluation

    J. E. N. Brainer

    2014-12-01

    Full Text Available The liquid phase oxidation of glycerol was performed producing fine organic acids. Catalysts based on Pt, Pd and Bi supported on activated carbon were employed to perform the conversion of glycerol into organic acids at 313 K, 323 K and 333 K, under atmospheric pressure (1.0 bar, in a mechanically agitated slurry reactor (MASR. The experimental results indicated glycerol conversions of 98% with production of glyceric, tartronic and glycolic acids, and dihydroxyacetone. A yield of glyceric acid of 69.8%, and a selectivity of this compound of 70.6% were reached after 4 h of operation. Surface mechanisms were proposed and rate equations were formulated to represent the kinetic behavior of the process. Selective formation of glyceric acid was observed, and the kinetic parameter values indicated the lowest activation energy (38.5 kJ/mol for its production reaction step, and the highest value of the adsorption equilibrium constant of the reactant glycerol (10-4 dm³/mol.

  11. A kinetic model for impact/sliding wear of pressurized water reactor internal components. Application to rod cluster control assemblies

    A new concept of industrial wear model adapted to components of nuclear plants is proposed. Its originality is to be supported, on one hand, by experimental results obtained via wear machines of relatively short operational times, and, on the other hand, by the information obtained from the operating feedback over real wear kinetics of the reactors components. The proposed model is illustrated by an example which corresponds to a specific real situation. The determination of the coefficients permitting to cover all assembly of configurations and the validation of the model in these configurations have been the object of the most recent work. (author)

  12. A kinetic model for impact/sliding wear of pressurized water reactor internal components. Application to rod cluster control assemblies

    Zbinden, M.; Durbec, V.

    1996-12-01

    A new concept of industrial wear model adapted to components of nuclear plants is proposed. Its originality is to be supported, on one hand, by experimental results obtained via wear machines of relatively short operational times, and, on the other hand, by the information obtained from the operating feedback over real wear kinetics of the reactors components. The proposed model is illustrated by an example which corresponds to a specific real situation. The determination of the coefficients permitting to cover all assembly of configurations and the validation of the model in these configurations have been the object of the most recent work. (author). 34 refs.

  13. Solid-state NMR studies of nucleic acid components

    Dračínský, Martin; Hodgkinson, P.

    2015-01-01

    Roč. 5, č. 16 (2015), s. 12300-12310. ISSN 2046-2069 R&D Projects: GA ČR GA13-24880S Institutional support: RVO:61388963 Keywords : NMR spectroscopy * nucleic acids * solid-state NMR Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.840, year: 2014 http://pubs.rsc.org/en/content/articlepdf/2015/ra/c4ra14404j

  14. Lipid clustering in bilayers detected by the fluorescence kinetics and anisotropy of trans-parinaric acid.

    C. Reyes Mateo; Brochon, J C; M Pilar Lillo; Ulises Acuña, A.

    1993-01-01

    Fluid heterogeneity in lipid bilayers and shows a simple and useful method to quantify this heterogeneity. Taking advantage of the maximum entropy method, we have resolved the probe fluorescence lifetime distributions in homogeneous solutions and in single and two-component lipid bilayers at different temperatures. A precise description of the emission kinetics was obtained as a function of viscosity in the homogeneous solution and as a function of the phase composition (gel/fluid) in the lip...

  15. Esterification of oleic acid for biodiesel production catalyzed by SnCl{sub 2}: a kinetic investigation

    Cardoso, A. L.; Gonzaga Neves, S. C.; Silva, M. J. da [Departament of Chemistry, Federal University of Vicosa, Vicosa, Minas Gerais, 36570-000 (Brazil)

    2008-07-01

    The production of biodiesel from low-cost raw materials which generally contain high amounts of free fatty acids (FFAs) is a valuable alternative that would make their production costs more competitive than petroleum-derived fuel. Currently, the production of biodiesel from this kind of raw materials comprises a two-stage process, which requires an initial acid-catalyzed esterification of the FFA, followed by a basecatalyzed transesterification of the triglycerides. Commonly, the acid H{sub 2}SO{sub 4} is the catalyst on the first step of this process. It must be said, however, that major drawbacks such as substantial reactor corrosion and the great generation of wastes, including the salts formed due to neutralization of the mineral acid, are negative and virtually unsurmountable aspects of this protocol. In this paper, tin(II) chloride dihydrate (SnCl{sub 2}{center_dot}2H{sub 2}O), an inexpensive Lewis acid, was evaluated as catalyst on the ethanolysis of oleic acid, which is the major component of several fat and vegetable oils feedstocks. Tin chloride efficiently promoted the conversion of oleic acid into ethyl oleate in ethanol solution and in soybean oil samples, under mild reaction conditions. The SnCl{sub 2} catalyst was shown to be as active as the mineral acid H{sub 2}SO{sub 4}. Its use has relevant advantages in comparison to mineral acids catalysts, such as less corrosion of the reactors and as well as avoiding the unnecessary neutralization of products. Herein, the effect of the principal parameters of reaction on the yield and rate of ethyl oleate production has been investigated. Kinetic measurements revealed that the esterification of oleic acid catalyzed by SnCl{sub 2}{center_dot}2H{sub 2}O is first-order in relation to both FFAs and catalyst concentration. Experimentally, it was verified that the energy of activation of the esterification reaction of oleic acid catalyzed by SnCl{sub 2} was very close to those reported for H{sub 2}SO{sub 4

  16. A novel diffusion-biphasic hydrolysis coupled kinetic model for dilute sulfuric acid pretreatment of corn stover.

    Chen, Longjian; Zhang, Haiyan; Li, Junbao; Lu, Minsheng; Guo, Xiaomiao; Han, Lujia

    2015-02-01

    Kinetic experiments on the dilute sulfuric acid pretreatment of corn stover were performed. A high xylan removal and a low inhibitor concentration were achieved by acid pretreatment. A novel diffusion-hydrolysis coupled kinetic model was proposed. The contribution to the xylose yield was analyzed by the kinetic model. Compared with the inhibitor furfural negatively affecting xylose yield, the fast and slow-hydrolyzing xylan significantly contributed to the xylose yield, however, their dominant roles were dependent on reaction temperature and time. The impact of particle size and acid concentration on the xylose yield were also investigated. The diffusion process may significantly influence the hydrolysis of large particles. Increasing the acid concentration from 0.15 M to 0.30 M significantly improved the xylose yield, whereas the extent of improvement decreased to near-quantitative when further increasing acid loading. These findings shed some light on the mechanism for dilute sulfuric acid hydrolysis of corn stover. PMID:25479388

  17. Study on the kinetics and transformation products of salicylic acid in water via ozonation.

    Hu, Ruikang; Zhang, Lifeng; Hu, Jiangyong

    2016-06-01

    ozonation of salicylic acid in water, in terms of transformation products, kinetic, mechanism, as well as degradation pathways. PMID:27031802

  18. Kinetics of Reaction Between Tc(Ⅶ) and Monomethylhydrazine or Dimethylhydroxylamine in Nitric Acid Medium Containing Plutonium

    2008-01-01

    <正>The chemical reaction kinetics research of Tc(Ⅶ) with monomethylhydrazine or dimethylhydroxy-lamine in nitric acid medium demonstrated that Tc(Ⅶ) hardly reacts with the salt-free reagents during the

  19. Comparison of palmitic acid kinetics during glucose or ketone body infusions

    Birkhahn, R.H.; Block, D.J.; Birkhahn, G.C.; Thomford, N.R.

    1986-03-05

    Ketone body interactions can be observed for extended ketosis by infusion by monoacetoacetin (the monoglyceride of acetoacetic acid). Palmitic acid kinetics were compared on the 5th day of glucose or ketone body-glucose infusions. 20 rats were fed complete diets intravenously at the rate of 50 ml/day. All diets contained vitamins, trace minerals, electrolytes, amino acids and 1 kcal/ml of non-protein energy. Rats were divided by energy source: Group A (n = 10) received energy from glucose and Group B (n = 10) from 72% monoacetoacetin plus 28% glucose. Diets were given at 1/2 and 3/4 rats on days 1 and 2, respectively and at full rate for days 3-5. Urinary nitrogen losses, body weight and dietary intake were measured daily. Palmitate kinetics was measured on day 5 using a continuous infusion of (1-/sup 14/C) palmitate and measuring C-14 in breath and plasma and plasma palmitate by GC. The two groups had similar body weight changes and urinary nitrogen losses over the 3 days of full intake Group A had lower plasma palmitate (88 +/- 7 vs 105 +/- 6 micromol/l) but similar turnover (17.1 +/- 2.4 vs 15.0 +/- 1.9 mmol/hr) and oxidation 2.3 +/- 0.3 vs 2.2 +/- 0.05 mmol/hr) compared to Group B. These data show that feeding monoacetoacetin intravenously does not stimulate fatty acid metabolism in the well nourished rat.

  20. Dissolution kinetics of Si and Al from montmorillonite in carbonic acid solution

    Xiaoming Ni; Quanzhong Li; Wenxue Chen

    2014-01-01

    The reaction between carbonic acid and montmorillonite minerals was studied in order to provide a theoretical basis for analyzing changes in the physical properties of coal seams after CO2 injection and for optimizing CO2 pumping parameters. A single montmorillonite mineral of purity [90%was selected and subjected to reactions at 25, 35, and 45 ?C in carbonic acid solutions of varying acidity. The Si and Al concentrations in the solutions and the structure and elemental compositions of the montmorillonite before and after the reactions were analyzed using a spectrophotometer, an X-ray diffractometer, and an energy-dispersive X-ray spectrometer;kinetic reaction models were established for the dissolution of Si and Al in carbonic acid solutions in order to estimate the apparent activation energy of Si dissolution under different acidity conditions. The results indicate that Al dissolved rapidly and soon reached solubility equilibrium. On the other hand, Si concentration in the solutions increased rapidly and then gradually declined with vibrations, with maximum values at 25, 35, and 45 ?C, which were observed at approximately 96, 72, and 48 h, respectively. In addition, Si dissolution fitted the diffusion-controlled reaction model well;as the pH value decreased, the apparent activation energy of Si dissolution decreased, and Si became easier to dissolve. Furthermore, it was concluded that as a weak acid, carbonic acid causes little damage to the mineral structure of montmorillonite.

  1. Transesterification of canola, palm, peanut, soybean and sunflower oil with methanol, ethanol, isopropanol, butanol and tert-butanol to biodiesel: Modelling of chemical equilibrium, reaction kinetics and mass transfer based on fatty acid composition

    Graphical abstract: Modelling of chemical equilibrium, reaction kinetics and mass transfer for triglyceride transesterification with different alcohols based on fatty acid composition. - Highlights: • Catalysed transesterification to biodiesel with various oils, alcohols and catalysts. • Analysis of components and reactivity based on fatty acid composition of all species. • Simultaneous modelling of mass transfer, reaction kinetics and chemical equilibrium. • Diffusivities, distribution and mass transfer coefficients for individual components. • Correlation of kinetic parameters with molecular structure of reactants and products. - Abstract: Mechanism of alcoholysis (e.g. methanolysis) using different oils, alcohols and homogeneous base catalysts was utilized to devise chemical kinetics and thermodynamics based on fatty acid composition, differentiating among triglycerides, diglycerides, monoglycerides and fatty acid alkyl esters (e.g. fatty acid alkyl esters, FAME) with bonded gadoleic, linoleic, linolenic, oleic, palmitic and stearic acid-originating substituents. Their concentrations were measured using an optimized high-performance liquid chromatography (HPLC) method. Hydrodynamics and diffusion limitations in emulsion were considered in overall model by determining diffusivities, distribution coefficients, molar volumes, boiling points and viscosities of individual components. Pre-exponential factors and activation energies were related with structure of reactants, intermediates and products acknowledging number of carbons, double bonds and alkyl branches by linear and mixed response surface methodology. Developed model may be used with batch and continuous flow reactors, e.g. for novel micro-structured or industrial-scale process intensification, different vegetable or non-edible oils (waste cooking Jatropha or microalgae lipids)

  2. Are the Crystal Structures of Enantiopure and Racemic Mandelic Acids Determined by Kinetics or Thermodynamics?

    Hylton, Rebecca K; Tizzard, Graham J; Threlfall, Terence L; Ellis, Amy L; Coles, Simon J; Seaton, Colin C; Schulze, Eric; Lorenz, Heike; Seidel-Morgenstern, Andreas; Stein, Matthias; Price, Sarah L

    2015-09-01

    Mandelic acids are prototypic chiral molecules where the sensitivity of crystallized forms (enantiopure/racemic compound/polymorphs) to both conditions and substituents provides a new insight into the factors that may allow chiral separation by crystallization. The determination of a significant number of single crystal structures allows the analysis of 13 enantiopure and 30 racemic crystal structures of 21 (F/Cl/Br/CH3/CH3O) substituted mandelic acid derivatives. There are some common phenyl packing motifs between some groups of racemic and enantiopure structures, although they show very different hydrogen-bonding motifs. The computed crystal energy landscape of 3-chloromandelic acid, which has at least two enantiopure and three racemic crystal polymorphs, reveals that there are many more possible structures, some of which are predicted to be thermodynamically more favorable as well as slightly denser than the known forms. Simulations of mandelic acid dimers in isolation, water, and toluene do not differentiate between racemic and enantiopure dimers and also suggest that the phenyl ring interactions play a major role in the crystallization mechanism. The observed crystallization behavior of mandelic acids does not correspond to any simple "crystal engineering rules" as there is a range of thermodynamically feasible structures with no distinction between the enantiopure and racemic forms. Nucleation and crystallization appear to be determined by the kinetics of crystal growth with a statistical bias, but the diversity of the mandelic acid crystallization behavior demonstrates that the factors that influence the kinetics of crystal nucleation and growth are not yet adequately understood. PMID:26244445

  3. Temperature-controlled structure and kinetics of ripple phases in one- and two-component supported lipid bilayers

    Kaasgaard, Thomas; Leidy, Chad; Crowe, J.H.; Mouritsen, Ole G.; Jørgensen, Kent

    2003-01-01

    ripples was seen. From height profiles of the AFM images, estimates of the amplitudes of the different ripple phases are reported. To elucidate the processes of ripple formation and disappearance, a ripple-phase DPPC lipid bilayer was taken through the pretransition in the cooling and the heating......Temperature-controlled atomic force microscopy (AFM) has been used to visualize and study the structure and kinetics of ripple phases in one-component dipalmitoylphosphaticlylcholine (DPPC) and two-component dimyristoylphosphatidylcholine-distearoylphosphatidylcholine (DMPC-DSPC) lipid bilayers....... The lipid bilayers are mica-supported double bilayers in which ripple-phase formation occurs in the top bilayer. In one-component DPPC lipid bilayers, the stable and metastable ripple phases were observed. In addition, a third ripple structure with approximately twice the wavelength of the metastable...

  4. Effect of a Previous Acid Adaptation of Zygosaccharomyces bailii on its Growth Kinetic in Acidic Media

    Alex Tchuenchieu

    2014-11-01

    Full Text Available The growth response of Zygosaccharomyces bailii acid adapted cells was assessed in acidified media. Yeast cells were first pre-cultured in nutrient broth adjusted with hydrochloric, citric and malic acid to pH 4; 4.5; 5; 5.5; 6 and 6.5. Moreover, they were also grown in two controls consisting of nutrient broth and nutrient broth supplemented with 1% of glucose both adjusted at pH 7. The variation of pH before and after the growth along with yeast concentration was measured. The cells pre-cultured in controls conditions and in the three conditions at pH 5 were then each inoculated in six BHI medium consisting of BHI adjusted with hydrochloric, citric and malic acid at pH 5.5 and 3.5. The growth was monitored by spectrophotometry and the yeast concentration after incubation was obtained by microscopy using a Thoma cell chamber. DMFit 2.1 was used to plot the growth curves and to estimate the growth parameters. All the pre-cultures and cultures were made at 37°C during 24 hours. During the pre-cultures, an important decrease of pH was noted in nutrient broth supplemented with glucose, moving from 7 to 3.81. In all the other pre-cultures, just a little variation was observed ranging from -0.57 to 0.50. Growth was observed in all the conditions, except at pH4. By growing the cells coming from the selected pre-cultures conditions in the different acidic BHI media, it appears that acid adaptation enhance the growth at pH 5.5 no matter the acid contains in the medium and the acid to which the cells were adapted. However, this acid adaptation was not sufficient to initiate growth at pH 3.5 after 24 hours of incubation at 37°C. Growth rate was significantly affected by the pH of the pre-culture medium and the acid present in the culture medium. Pre-culture with glucose supplementation was the only parameter studied affecting the latency.

  5. Oxidation of Chalcones by Morpholinium Chlorochromate with Oxalic Acid as Catalyst: Kinetic and Mechanistic Study

    K. Rajalakshmi

    2013-01-01

    Full Text Available The kinetics of oxidation of chalcones by morpholinium chlorochromate (MCC has been studied in 55% acetic acid-water (v/v medium. The reaction showed unit order dependence each with respect to oxidant and catalyst and fractional order with respect to substrate and H+ ion. Increased ionic strength has no effect on the reaction rate. In the case of substituted chalcones, the order with respect to substrate varies depending upon the nature of the substituent present in the ring. In general, the electron withdrawing substituents retard the reaction rate while the electron releasing substituents enhance the rate of the reaction. From the kinetic data obtained, the activation parameters have been calculated and a suitable mechanism has been proposed.

  6. Super phosphoric acid catalyzed esterification of Palm Fatty Acid Distillate for biodiesel production: physicochemical parameters and kinetics

    Metre Anand V.

    2015-03-01

    Full Text Available In the present study the esterification of palm fatty acid distillate (PFAD, a by-product from palm oil industry, in the presence of super phosphoric acid (SPA catalyst was studied. The effects of various physico-chemical parameters such as temperature, PFAD to methanol molar ratio and amount of catalyst on the conversion of biodiesel were investigated. The percent conversion of FFA and properties of the biodiesel were determined following standard methodologies. Percent conversion of biodiesel was found to increase with the increase in PFAD to methanol molar ratio and at 1:12 molar ratio and 70°C temperature 95% conversion was achieved. Thermodynamic parameters were also evaluated in terms of Gibbs free energy, enthalpy and entropy at different molar ratio and temperatures. Both pseudo first and second order irreversible kinetics were applied to a wide range of experimental data. However, according to regression coefficient (R2 the second order described better experimental behavior of kinetic data.

  7. Kinetic studies on the carboxylation of 6-amino-penicillanic acid to 8-hydroxy-penillic acid

    Henriksen, Claus Maxel; Holm, SS; Schipper, D.;

    1997-01-01

    The carboxylation in aqueous solution of 6-amino-penicillanic acid (6-APA) to 8-hydroxy-penillic acid (8-HPA) was studied at 25 degrees C and pH 6.5. During sparging with either a citrate buffer or a chemically defined cultivation medium containing 6-APA with mixtures of carbon dioxide and air (2.......7-41% (v/v) CO2), the kinetics for conversion of 6-APA was followed by HPLC. In the citrate buffer 6-APA was converted by two competitive reactions each following first order kinetics with respect to the concentration of 6-APA: 1. carboxylation into 8-HPA; and 2. slow conversion into an unknown compound....... Formation of the unknown compound was not observed in the cultivation medium. The carboxylation of 6-APA was also found to be first order with respect to the concentration of dissolved carbon dioxide. The rate constant for formation of 8-HPA did not differ significantly in the cultivation medium compared to...

  8. System-level understanding of the potential acid-tolerance components of Acidithiobacillus thiooxidans ZJJN-3 under extreme acid stress.

    Feng, Shoushuai; Yang, Hailin; Wang, Wu

    2015-09-01

    In previous study, two extremely acidophilic strains Acidithiobacillus thiooxidans ZJJN-3 (collection site: bioleaching leachate) and ZJJN-5 (collection site: bioleaching wastewater) were isolated from a typical industrial bio-heap in China. Here, we unraveled the potential acid-tolerance components of ZJJN-3 by comparing the physiological differences with ZJJN-5 under different acid stresses. The parameters used for comparison included intracellular pH (pHin), capsule morphology, fatty acid composition of cell membrane, transcription of key molecular chaperones, H(+)-ATPase activities and NAD(+)/NADH ratio. It was indicated that the acid-tolerance of A. thiooxidans ZJJN-3 was systematically regulated. Capsule first thickened and then shed off along with increased acid stress. Cell membrane maintained the intracellular stability by up-regulating the proportion of unsaturated fatty acid and cyclopropane fatty acids. Meanwhile, the transcription of key repair molecular chaperones (GrpE-DnaK-DnaJ) was up-regulated by 2.2-3.5 folds for ensuring the proper folding of peptide. Moreover, low pHin promoted ZJJN-3 to biosynthesize more H(+)-ATPase for pumping H(+) out of cells. Furthermore, the NAD(+)/NADH ratio increased due to the decreased H(+) concentration. Based on the above physiological analysis, the potential acid-tolerance components of A. thiooxidans ZJJN-3 were first proposed and it would be useful for better understanding how these extremophiles responded to the high acid stress. PMID:26264736

  9. Quantitative analysis of myocardial kinetics of 15-p-[iodine-125] iodophenylpentadecanoic acid

    Myocardial extraction and the characteristic tissue clearance of radioactivity following bolus injections of a radioiodinated (125I) long chain fatty acid (LCFA) analog 15-p-iodophenylpentadecanoic acid (IPPA) were examined in the isolated perfused working rat heart. Radioactivity remaining in the heart was monitored with external scintillation probes. A compartmental model which included nonesterified tracer, catabolite, and complex lipid compartments successfully fitted tissue time-radioactivity residue curves, and gave a value for the rate of IPPA oxidation 1.8 times that obtained from steady-state release of tritiated water from labeled palmitic acid. The technique was sensitive to the impairment of LCFA oxidation in hearts of animals treated with the carnitine palmitoyltransferase I inhibitor, 2[5(4-chlorophenyl)pentyl]oxirane-2-carboxylate (POCA). IPPA or similar modified fatty acids may be better than 11C-labeled physiological fatty acids such as palmitate in this type of study, because efflux of unoxidized tracer and catabolite(s) from the heart are kinetically more distinct, and their contributions to the early data can be reliably separated. This technique may be suitable for extension to in vivo measurements with position tomography and appropriate modified fatty acids

  10. Kinetics of liquid-solid reactions in naphthenic acid conversion and Kraft pulping

    Yang, Ling

    Two liquid-solid reactions, in which the morphology of the solid changes as the reactions proceeds, were examined. One is the NA conversion in oil by decarboxylation on metal oxides and carbonates, and the other is the Kraft pulping in which lignin removal by delignification reaction. In the study of the NA conversion, CaO was chosen as the catalyst for the kinetic study from the tested catalysts based on NA conversion. Two reaction mixtures, carrier oil plus commercial naphthenic acids and heavy vacuum gas oil (HVGO) from Athabasca bitumen, were applied in the kinetic study. The influence of TAN, temperature, and catalyst loading on the NA conversion and decarboxylation were studied systematically. The results showed that the removal rate of TAN and the decarboxylation of NA were both independent of the concentration of NA over the range studied, and significantly dependent on reaction temperature. The data from analyzing the spent catalyst demonstrated that calcium naphthenate was an intermediate of the decarboxylation reaction of NA, and the decomposition of calcium naphthenate was a rate-determining step. In the study on the delignification of the Kraft pulping, a new mechanism was proposed for the heterogeneous delignification reaction during the Kraft pulping process. In particular, the chemical reaction mechanism took into account the heterogeneous nature of Kraft pulping. Lignin reacted in parallel with sodium hydroxide and sodium sulfide. The mechanism consists of three key kinetic steps: (1) adsorption of hydroxide and hydrosulfide ions on lignin; (2) surface reaction on the solid surface to produce degraded lignin products; and (3) desorption of degradation products from the solid surface. The most important step for the delignification process is the surface reaction, rather than the reactions occurring in the liquid phase. A kinetic model has, thus, been developed based on the proposed mechanism. The derived kinetic model showed that the mechanism

  11. Thermodynamic and kinetic modelling of the reduction of concentrated nitric acid

    This research thesis aimed at determining and quantifying the different stages of the reduction mechanism in the case of concentrated nitric acid. After having reported the results of a bibliographical study on the chemical and electrochemical behaviour of concentrated nitric media (generalities, chemical equilibriums, NOx reactivity, electrochemical reduction of nitric acid), the author reports the development and discusses the results of a thermodynamic simulation of a nitric environment at 25 C. This allowed the main species to be identified in the liquid and gaseous phases of nitric acid solutions. The author reports an experimental electrochemical investigation coupled with analytic techniques (infrared and UV-visible spectroscopy) and shows that the reduction process depends on the cathodic overvoltage, and identifies three potential areas. A kinetic modelling of the stationary state and of the impedance is then developed in order to better determine, discuss and quantify the reduction process. The application of this kinetic model to the preliminary results of an electrochemical study performed on 304 L steel is then discussed

  12. Kinetics of pyrite oxidation by hydrogen peroxide in phosphoric acid solutions

    VALENTINA DIMITRIJEVIC

    1999-12-01

    Full Text Available The kinetics of pyrite oxidation by hydrogen peroxide in phosphoric acid solutions were investigated. The effects of stirring, temperature, and particle size, as well as of the hydrogen peroxide and phosphoric acid concentrations were studied. The effect of phosphate ion addition was also examined. The oxidation kinetics was found to follow a shrinking core model, with the surface chemical reaciton as the rate-controlling step. This is in accord with an activation energy of 57 kJ mol-1 and a linear relationship between the rate constant and the reciprocal of the particle radius. The reaction order with respect to the hydrogen peroxide concentration was found to be equal to unity. Variation of the phosphoric acid concentration had practically no effect on the rate of pyrite oxidation. Addition of the phosphate ion in the relatively low concentration range (0.005-0.1 mol dm-3 had a highly negative influence on the rate of pyrite oxidation, indicating that this ion has an inhibiting effect on the oxidation of pyrite by hydrogen peroxide.

  13. Kinetics of Non-Catalytic Esterification of Free Fatty Acids Present in Jatropha Oil.

    Prasanna Rani, Karna Narayana; Ramana Neeharika, Tulasi Sri Venkata; Kumar, Thella Prathap; Satyavathi, Bankupalli; Sailu, Chintha

    2016-05-01

    Non-catalytic esterfication of free fatty acids (FFA) present in vegetable oils is an alternative pretreatment process for the biodiesel production. Biodiesel, consists of long-chain fatty acid methyl esters (FAME) and is obtained from renewable sources such as vegetable oils or animal fat. This study presents kinetics of thermal esterification of free fatty acids present in jatropha oil with methanol. The effect of process parameters like reaction time (1-5 h), temperature (170-190°C) and oil to methanol ratio (1:3-1:5) at constant pressure was investigated. The optimal conditions were found to be oil to methanol ratio of 1:4, 190°C, at 27.1 bar and 5 h which gave a maximum conversion of 95.1%. A second order kinetic model for both forward and backward reactions was proposed to study the reaction system. A good agreement was observed between the experimental data and the model values. The activation energy for forward reaction and the heat of reaction were found to be 36.364 Kcal/mol and 1.74 Kcal/mol respectively. PMID:27086997

  14. Kinetics and Quantitative Structure—Activity Relationship Study on the Degradation Reaction from Perfluorooctanoic Acid to Trifluoroacetic Acid

    Chen Gong

    2014-08-01

    Full Text Available Investigation of the degradation kinetics of perfluorooctanoic acid (PFOA has been carried out to calculate rate constants of the main elementary reactions using the multichannel Rice-Ramsperger-Kassel-Marcus theory and canonical variational transition state theory with small-curvature tunneling correction over a temperature range of 200~500 K. The Arrhenius equations of rate constants of elementary reactions are fitted. The decarboxylation is role step in the degradation mechanism of PFOA. For the perfluorinated carboxylic acids from perfluorooctanoic acid to trifluoroacetic acid, the quantitative structure–activity relationship of the decarboxylation was analyzed with the genetic function approximation method and the structure–activity model was constructed. The main parameters governing rate constants of the decarboxylation reaction from the eight-carbon chain to the two-carbon chain were obtained. As the structure–activity model shows, the bond length and energy of C1–C2 (RC1–C2 and EC1–C2 are positively correlated to rate constants, while the volume (V, the energy difference between EHOMO and ELUMO (ΔE, and the net atomic charges on atom C2 (QC2 are negatively correlated.

  15. Ion-exchange Resin Catalyzed Esterification of Lactic Acid with Isopropanol: a Kinetic Study

    Amrit P. Toor

    2011-05-01

    Full Text Available The kinetic behavior of esterification of lactic acid with isopropanol over an acidic cation exchange resin, Amberlyst 15, was studied under isothermal condition. Isopropyl lactate synthesized in this reaction is an important pharmaceutical intermediate. The experiments were carried out in a stirred batch reactor in the temperature range of 323.15 to 353.15 K. The effect of various parameters such as temperature, molar ratio and catalyst loading was studied. Variation in parameters on rate of reaction demonstrated that the reaction was intrinsically controlled. Kinetic modeling was performed using Eley-Rideal model which acceptably fits the experimental data. The activation energy was found to be 22.007 kJ/mol and frequency factor was 0.036809 l2 g-1 mol-1 min-1 for forward reaction. The value of entropy for the forward reaction was found to be 182.317 J K-1 mol-1 . © 2011 BCREC UNDIP. All rights reserved(Received: 19th January 2011, Revised: 16th March 2011; Accepted: 16th March 2011[How to Cite: A.P. Toor, M. Sharma, S. Thakur, and R. K. Wanchoo. (2011. Ion-exchange Resin Catalyzed Esterification of Lactic Acid with Isopropanol: a Kinetic Study. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1: 39-45. doi:10.9767/bcrec.6.1.791.39-45][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.791.39-45 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/791 ] | View in  

  16. Analysis of embryo, cytoplasm and maternal effects on fatty acid components in soybean (Glycine max Merill.)

    NING Hailong; LI Wenxia; LI Wenbin

    2007-01-01

    The quality of oil determined by the constituents and proportion of fatty acid components,and the understanding of heredity of fatty acid components are of importance to breeding good quality soybean varieties.Embryo,cytoplasmic and maternal effects and genotype×environment interaction effects for quality traits of soybean [Glycine max (L.) Merrill.] seeds were analyzed using a general genetic model for quantitative traits of seeds with parents,F1 and F2,of 20 crosses from a diallel mating design of five parents planted in the field in 2003 and 2004 in Harbin,China.The interaction effects of palmitic,stearic,and linoleic acid contents were larger than the genetic main effects,while the genetic main effects were equal to interaction effects for linolenic and oleic acid content.Among all kinds of genetic main effects,the embryo effects were the largest for palmitic,stearic,and linoleic acids,while the cytoplasm effects were the largest for oleic and linolenic acids.Among all kinds of interaction effects,the embryo interaction effects were the largest for fatty acids.The sum of additive and additive× environment effects were larger than that of dominance and dominance×environment effects for the linolenic acid content,but not for other quality traits.The general heritabilities were the main parts of heritabilities for palmitic and oleic acid contents,but the interaction was more important for stearic,linoleic,and linolenic acid contents.For the general heritability,maternal and cytoplasm heritabilities were the main components for palmitic,oleic,and linolenic acid contents.It was shown for the interaction heritabilities that the embryo interaction heritabilities were more important for oleic and linolenic acid contents,while the maternal interaction heritabilities were more important for linoleic acid content.Among selection response components,the maternal and cytoplasm general responses and/or interaction responses were more important for palmitic

  17. Kinetics of Acid-Catalyzed Dehydration of Cyclic Hemiacetals in Organic Aerosol Particles in Equilibrium with Nitric Acid Vapor.

    Ranney, April P; Ziemann, Paul J

    2016-04-28

    Previous studies have shown that 1,4-hydroxycarbonyls, which are often major products of the atmospheric oxidation of hydrocarbons, can undergo acid-catalyzed cyclization and dehydration in aerosol particles to form highly reactive unsaturated dihydrofurans. In this study the kinetics of dehydration of cyclic hemiacetals, the rate-limiting step in this process, was investigated in a series of environmental chamber experiments in which secondary organic aerosol (SOA) containing cyclic hemiacetals was formed from the reaction of n-pentadecane with OH radicals in dry air in the presence of HNO3. A particle beam mass spectrometer was used to monitor the formation and dehydration of cyclic hemiacetals in real time, and SOA and HNO3 were quantified in filter samples by gravimetric analysis and ion chromatography. Measured dehydration rate constants increased linearly with increasing concentration of HNO3 in the gas phase and in SOA, corresponding to catalytic rate constants of 0.27 h(-1) ppmv(-1) and 7.0 h(-1) M(-1), respectively. The measured Henry's law constant for partitioning of HNO3 into SOA was 3.7 × 10(4) M atm(-1), ∼25% of the value for dissolution into water, and the acid dissociation constant was estimated to be SOA and that dehydration of cyclic hemiacetals was catalyzed by molecular HNO3 rather than by H(+). The Henry's law constant and kinetics relationships measured here can be used to improve mechanisms and models of SOA formation from the oxidation of hydrocarbons in dry air in the presence of NOx, which are conditions commonly used in laboratory studies. The fate of cyclic hemiacetals in the atmosphere, where the effects of higher relative humidity, organic/aqueous phase separation, and acid catalysis by molecular H2SO4 and/or H(+) are likely to be important, is discussed. PMID:27043733

  18. Thermodynamics and kinetics of thermal decomposition of diamylamyl phosphonate-nitric acid systems

    Highlights: ► The thermal hazard characteristics of DAAP has been evaluated for the first time. ► The thermodynamic and kinetic parameters have also been derived wherever possible. ► The onset of decomposition of the acid-solvates depended on the nitric acid content. ► A clear trend was seen in the decomposition of acid-solvates of TBP, TiAP and DAAP. - Abstract: Thermal decomposition of neat diamylamyl phosphonate (DAAP), nitric acid-solvates of DAAP and 1.1 M DAAP/n-dodecane was studied calorimetrically in heat-wait-search mode for the first time. The neat DAAP decomposed beyond 500 K while DAAP·0.7HNO3, DAAP·HNO3 and DAAP·2.1HNO3 decomposed exothermally at 386, 381 and 366 K respectively, indicating the role of amount of nitric acid on decomposition. Mixture of DAAP and 8 M nitric acid decomposed at a lower temperature than the acid solvates with a larger excursion in temperature and pressure yielding hydrocarbons, CO2, CO, NOx and a reddish liquid or a black solid residue. Enthalpy of decomposition of DAAP·0.7HNO3, DAAP·HNO3 and DAAP·2.1HNO3 were found to be −237.7 ± 4.8, −348.9 ± 3.4 and −1002.1 ± 2.6 kJ mol−1 and the activation energy and pre-exponential factors were 127.5 ± 1.5, 121.8 ± 0.8 and 105.3 ± 1.2 kJ mol−1 and 9.0 × 1013, 1.4 × 1012 and 2.2 × 1010 lit mol−1 s 1, respectively. Heat capacity (Cp) of acid solvates were measured and used for deriving the enthalpy change.

  19. Thermodynamics and kinetics of thermal decomposition of dibutylalkyl and dipentylalkyl phosphonate-nitric acid systems

    Tributyl phosphate (TBP) is used in the reprocessing industry for the separation of uranium and plutonium from the spent nuclear fuels by PUREX process. A variety of dialkylalky/phosphonates were synthesised and their extraction behaviour on actinides was studied in this laboratory. The superior extraction characteristics of phosphonates make them useful for several metal recovery applications in the nuclear fuel cycle. However, higher solubility of phosphonates in aqueous phase as compared to TBP, introduces higher chances of the formation of thermally active 'red oil' like substances during the evaporation of aqueous streams. Thermal stability of neat and nitric acid solvated homologues of four dibutylalkyl phosphonates namely, dibutylpropyl phosphonate (DBPrP), dibutylbutyl phosphonate (DBBP), dibutylpentyl phosphonate (DBPP), dibutylhexyl phosphonate (DBHeP), and two dipentylalkyl phosphonates viz. dipentylbutyl phosphonate (DPBP), dipentylhexyl phosphonate (DPHeP) were studied. Experiments were conducted using an adiabatic calorimeter in heat-wait-search mode. Various stoichiometry of nitric acid-solvated DBalP and DPalP were prepared by equilibrating the respective organic with 4-15.6 M nitric acid followed by separation. Neat DBalP and DPalP are stable up to the temperature of ∼ 555 K while their acid-solvates decomposed in the temperature range 380-403 K. The results also indicated that the presence of nitric acid accelerated the decomposition of phosphonates. Decomposition of these acid solvated phosphonates is found to be exothermic and follows first order kinetics. The onset temperature, adiabatic temperature rise, pressure rise, decomposition enthalpy and activation energy were found to strongly depend on the nitric acid content of the acid-solvates. The studies also indicate that dibutylalkyl and dipentylalkyl phosphonates are also prone to form 'red oil' like substances under extreme conditions and can lead to run-away reactions

  20. Kinetic modeling of multi‐component crystallization of industrial‐grade oils and fats

    Hjorth, Jeppe L.; Miller, Rasmus L.; Woodley, John M.;

    2015-01-01

    Transient crystallization kinetics is investigated for complex, industrial‐grade vegetable oils consisting of more than ten triacylglycerols (TAG). The classical nucleation model has been used to describe primary nucleation, while secondary nucleation has been described by a semi‐empirical approach...... describe how higher cooling rates lead to formation of more meta‐stable crystals and smaller mean‐crystal sizes. : The model provides a good starting point for developing more realistic, transient models for TAG crystallization with the ability to accommodate processing conditions and complex chemical...

  1. Mechanism and Kinetics for the Dissolution of Apatitic Materials in Acid Solutions

    Calmanovici C.E.

    1997-01-01

    Full Text Available Abstract - This work concerns the study of the digestion step in the production process of phosphoric acid. Some qualitative experiments indicate that the difference between the pH at the surface of the phosphate and that in the bulk of the solution is negligible and that the dissolution is controlled by diffusion of products away from the phosphate particle. In further experiments, to isolate the dissolution phenomenon from the formation of calcium sulfate, the sulfuric acid normally used industrially is replaced by hydrochloric acid. The phosphate material used in our experiments is a model apatitic material: synthetic hydroxyapatite (HAP. The dissolution of calcium hydroxyapatite was studied with increasing amounts of calcium and phosphate at different temperatures. A simple method was developed for this observation based on the time required for complete dissolution of the HAP powder. The results confirm that the dissolution is controlled by a diffusional process through an interface of calcium and phosphate ions released from the solid surface. A kinetic model for the dissolution of apatitic materials is proposed which assumes a shrinking particle behaviour controlled by diffusion of calcium ions. The experimental results are fitted to this model to determine the mass transfer constant for HAP dissolution in acid solutions. The activation energy of the reaction is about 14kJ/mol. This study was carried on in conditions similar to the industrial ones for the production of phosphoric acid by the dihydrate-process

  2. Kinetics of D-lactic acid production by Sporolactobacillus sp. strain CASD using repeated batch fermentation.

    Zhao, Bo; Wang, Limin; Li, Fengsong; Hua, Dongliang; Ma, Cuiqing; Ma, Yanhe; Xu, Ping

    2010-08-01

    D-lactic acid was produced by Sporolactobacillus sp. strain CASD in repeated batch fermentation with one- and two-reactor systems. The strain showed relatively high energy consumption in its growth-related metabolism in comparison with other lactic acid producers. When the fermentation was repeated with 10% (v/v) of previous culture to start a new batch, D-lactic acid production shifted from being cell-maintenance-dependent to cell-growth-dependent. In comparison with the one-reactor system, D-lactic acid production increased approximately 9% in the fourth batch of the two-reactor system. Strain CASD is an efficient D-lactic acid producer with increased growth rate at the early stage of repeated cycles, which explains the strain's physiological adaptation to repeated batch culture and improved performance in the two-reactor fermentation system. From a kinetic point of view, two-reactor fermentation system was shown to be an alternative for conventional one-reactor repeated batch operation. PMID:20374976

  3. Competitive kinetics as a tool to determine rate constants for reduction of ferrylmyoglobin by food components.

    Jongberg, Sisse; Lund, Marianne N; Pattison, David I; Skibsted, Leif H; Davies, Michael J

    2016-05-15

    Competitive kinetics were applied as a tool to determine apparent rate constants for the reduction of hypervalent haem pigment ferrylmyoglobin (MbFe(IV)O) by proteins and phenols in aqueous solution of pH 7.4 and I=1.0 at 25°C. Reduction of MbFe(IV)O by a myofibrillar protein isolate (MPI) from pork resulted in kMPI=2.2 ± 0.1 × 10(4)M(-1)s(-1). Blocking of the protein thiol groups on the MPI by N-ethylmaleimide (NEM) markedly reduced this rate constant to kMPI-NEM=1.3 ± 0.4 × 10(3)M(-1)s(-1) consistent with a key role for the Cys residues on MPI as targets for haem protein-mediated oxidation. This approach allows determination of apparent rate constants for the oxidation of proteins by haem proteins of relevance to food oxidation and should be applicable to other systems. A similar approach has provided approximate apparent rate constants for the reduction of MbFe(IV)O by catechin and green tea extracts, though possible confounding reactions need to be considered. These kinetic data suggest that small molar excesses of some plant extracts relative to the MPI thiol concentration should afford significant protection against MbFe(IV)O-mediated oxidation. PMID:26775941

  4. Plasma kinetics of complement component C4: comparison of three models

    Plasma C4 kinetics were studied in members of a kindred with hereditary incomplete C4 deficiency and in control subjects. Test subjects received iodine 125-labeled C4 intravenously, and plasma disappearance curves for 125I-C4 were plotted. By nonlinear least-squares analysis, we fit two-, three-, and four-exponential models of plasma disappearance to the plasma curves of each subject. Goodness of fit was significantly better for all subjects with the three-exponential versus the two-exponential model (p less than 0.0005). No further improvement in curve fit was accomplished by using a four-exponential model (p greater than 0.5). Metabolic rates and extravascular/plasma ratios calculated from the two- and three-exponential models were significantly different. As judged by extravascular/plasma ratio, the two-exponential model underestimated the amount of extravascular C4. Furthermore, the two-exponential model significantly over-estimated catabolic and synthetic rates. Hence, our results show that C4 kinetics are not optimally described by a conventional, two-exponential model. A possible explanation for our findings is that in previous studies of C4 metabolism, the analysis of plasma radioactivity disappearance curves was done by inspection, whereas we used least-squares analysis, a method that determines the number of exponentials with greater reliability

  5. Complexes between ovalbumin nanoparticles and linoleic acid: Stoichiometric, kinetic and thermodynamic aspects.

    Sponton, Osvaldo E; Perez, Adrián A; Carrara, Carlos R; Santiago, Liliana G

    2016-11-15

    Stoichiometric, kinetic and thermodynamic aspects of complex formation between heat-induced aggregates of ovalbumin (ovalbumin nanoparticles, OVAn) and linoleic acid (LA) were evaluated. Extrinsic fluorescence data were fitted to modified Scatchard model yielding the following results: n: 49±2 LA molecules bound per OVA monomer unit and Ka: 9.80±2.53×10(5)M. Kinetic and thermodynamic properties were analyzed by turbidity measurements at different LA/OVA monomer molar ratios (21.5-172) and temperatures (20-40°C). An adsorption approach was used and a pseudo-second-order kinetics was found for LA-OVAn complex formation. This adsorption process took place within 1h. Thermodynamic parameters indicated that LA adsorption on OVAn was a spontaneous, endothermic and entropically-driven process, highlighting the hydrophobic nature of the LA and OVAn interaction. Finally, Atomic Force Microscopy imaging revealed that both OVAn and LA-OVAn complexes have a roughly rounded form with size lower than 100nm. PMID:27283701

  6. Kinetics and mechanism of sphalerite leaching by sodium nitrate in sulphuric acid solution

    Sokić M.

    2012-01-01

    Full Text Available Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time on the leaching degree of zinc were investigated and kinetic analysis of the process was accomplished. With temperature increasing from 60 to 90°C, the zinc leaching increased from 25.23% to 71.66% after 2 hours, i.e. from 59.40% to 99.83% after 4 hours. The selected kinetic model indicated that the diffusion through the product layer was the rate-controlling step during the sphalerite leaching. The activation energy was determined to be 55 kJ/mol in the temperature range 60-90°C. XRD, light microscopy and SEM/EDX analyses of the complex concentrate and leach residue confirmed formation of elemental sulphur and diffusion-controlled leaching mechanism.

  7. Kinetics of enzymatic synthesis of liquid wax ester from oleic acid and oleyl alcohol.

    Radzi, Salina Mat; Mohamad, Rosfarizan; Basri, Mahiran; Salleh, Abu Bakar; Ariff, Arbakariya; Rahman, Mohammad Basyaruddin Abdul; Rahman, Raja Noor Zaliha Raja Abdul

    2010-01-01

    The kinetics of wax ester synthesis from oleic acid and oleyl alcohol using immobilized lipase from Candida antartica as catalyst was studied with different types of impeller (Rushton turbine and AL-hydrofoil) to create different mixing conditions in 2l stirred tank reactor. The effects of catalyst concentration, reaction temperature, and impeller tip speed on the synthesis were also evaluated. Rushton turbine impeller exhibited highest conversion rate at lower impeller tip speed as compared to AL-hydrofoil impeller. A second-order reversible kinetic model from single progress curve for the prediction of fractional conversion at given reaction time was proposed and the corresponding kinetic parameter values were calculated by non-linear regression method. The results from the simulation using the proposed model showed satisfactory agreement with the experimental data. Activation energy shows a value of 21.77 Kcal/mol. The thermodynamic parameters of the process, enthalpy and entropy, were 21.15 Kcal/mol and 52.07 cal/mol.K, respectively. PMID:20124754

  8. Kinetics and Mechanism of Oxidation of Lactic Acid by Dihydroxyditelluratoargentate(Ⅲ) in Alkaline Medium

    2003-01-01

    The kinetics of the oxidation of lactic acid(Lac) by dihydroxyditelluratoargentate(Ⅲ)[abbreviated as DDA of Ag(Ⅲ)] anions was studied in an aqueous alkaline medium by conventional spectrophotometry in a temperature range of 25—40 ℃. The order of the redox reaction of lactic acid and DDA was found to be first-order. The rates increased with the increase in [OH-] and decreased with the increase in [tellurate]. No free radical was detected. In the view of this the dihydroxymonotelluratoargentate(Ⅲ) species(DMA) is assumed to be the active species. A plausible mechanism involving a two-electron transfer is proposed, and the rate equation derived from the mechanism can be used to explain all the experimental results. The activation parameters(25 ℃) and the rate constants of the rate-determining step along with the preequilibrium constants at different temperatures were evaluated.

  9. Hydrophobic amino acids as a new class of kinetic inhibitors for gas hydrate formation

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Lee, Bo Ram; Park, Da-Hye; Han, Kunwoo; Lee, Kun-Hong

    2013-08-01

    As the foundation of energy industry moves towards gas, flow assurance technology preventing pipelines from hydrate blockages becomes increasingly significant. However, the principle of hydrate inhibition is still poorly understood. Here, we examined natural hydrophobic amino acids as novel kinetic hydrate inhibitors (KHIs), and investigated hydrate inhibition phenomena by using them as a model system. Amino acids with lower hydrophobicity were found to be better KHIs to delay nucleation and retard growth, working by disrupting the water hydrogen bond network, while those with higher hydrophobicity strengthened the local water structure. It was found that perturbation of the water structure around KHIs plays a critical role in hydrate inhibition. This suggestion of a new class of KHIs will aid development of KHIs with enhanced biodegradability, and the present findings will accelerate the improved control of hydrate formation for natural gas exploitation and the utilization of hydrates as next-generation gas capture media.

  10. Kinetics of the Leaching Process of an Australian Gibbsitic Bauxite by Hydrochloric Acid

    Aichun Zhao

    2016-01-01

    Full Text Available Gibbsitic bauxite from Australia was leached by hydrochloric acid in this work. Analysis on kinetics for the extraction of Al2O3 was quantitatively studied. It was concluded that the hydrochloric acid leaching process of gibbsitic bauxite was controlled by chemical reaction. Moreover, the mechanism for the dissolution followed the equation, ln⁡k=39.44-1.66×104(1/T, with an apparent activation energy of 137.90 kJ/mol, according to the equation of k=Ae-Ea/RT. This work aims to provide a good theory support for the process control by using a new method of alumina production from the low grade bauxite.

  11. Kinetic study of the reduction of Np(VI) with humic acid

    237Np is one of the most long-life and toxic nuclides in the high level nuclear waste, and will become the primary hazard in the final nuclear waste disposal after a long time of storage, so it is important to study the chemical behaviour of Np. Humic acid is a kind of organic compound reduction in nature. The study of the kinetics of the reduction of Np(VI) with humic acid will afford a basis for further study of the chemical behaviour of Np in the environmental water. Considering the rapid exchange of Np valences during this experiment, extractants TTA and TOPO are used to analyze simultaneously three Np valences (VI), (V) and (IV)

  12. Kinetics and Mechanism of Oxidation of Lactic Acid by Dihydroxyditelluratoargentate(Ⅲ)in Alkaline Medium

    SHANJin-huan; WANGLi; LIUBao-sheng; SHENShi-gang

    2003-01-01

    The kinetics of the oxidation of lactic acid(Lac) by dihydroxyditelluratoargentate(Ⅲ)[abbreviated as DDA of Ag(Ⅲ)]anions was studied in an aqueous alkaline medium by conventional spectrophotometry in a temperature range of 25-40℃.The order of the redox reaction of lactic acid and DDA was found to be first-order.The rates increased with the increase in [OH-]and decreased with the increase in [tellurate].No free radical was detected.In the view of this the dihydroxymonotelluratoargentate(Ⅲ)species(DMA) is assumed to be the active species.A plausible mechanism involving a two-electron transfer is proposed,and the rate equation derived from the mechanism can be used to explain all the experimenttal results.The activation parameters(25℃)and the rate constants of the rate-determining step along with the preequilibrium constants at different temperatures were evaluated.

  13. A kinetic study of the oxidation of some amino acids by peroxydisulphate

    The present work deals with the study of redox reactions of some amino-acids (Leucine, Aspartic and Arganine) with peroxydisulphate. The kinetic study of the above reactions showed that these reactions followed first order with respect to peroxydisulphate and silver ion as catalyst and zero order with respect to the amino-acids. For these reactions, the activation energies and other thermodynamic parameters, namely entropy (ΔS≠) and free energy of activation (ΔG≠) were evaluated. The analysis of the reaction products by the (IR) revealed the presence of 2-butanone in the case of leucine, propanone in the case of aspartic and 2-3 butanone in the case of arganine. Plausible mechanisms were proposed for there are reactions in accordance with the experimentally observed rate law and the products formed. (Author)

  14. Quantitative evaluation of dichloroacetic acid kinetics in human--a physiologically based pharmacokinetic modeling investigation.

    Li, Ting; Schultz, Irv; Keys, Deborah A; Campbell, Jerry L; Fisher, Jeffrey W

    2008-03-12

    Dichloroacetic acid is a common disinfection by-product in surface waters and is a probable minor metabolite of trichloroethylene. Dichloroacetic acid (DCA) liver carcinogenicity has been demonstrated in rodents but epidemiological evidence in humans is not available. High doses of DCA ( approximately 50mg/kg) are used clinically to treat metabolic acidosis. Biotransformation of DCA by glutathione transferase zeta (GSTzeta) in the liver is the major elimination pathway in humans. GSTzeta is also inactivated by DCA, leading to slower systemic clearance and nonlinear pharmacokinetics after multiple doses. A physiologically based pharmacokinetic (PBPK) model was developed to quantitatively describe DCA biotransformation and kinetics in humans administered DCA by intravenous infusion and oral ingestion. GSTzeta metabolism was described using a Michaelis-Menten equation coupled with rate constants to account for normal GSTzeta synthesis, degradation and irreversible covalent binding and inhibition by the glutathione-bound-DCA intermediate. With some departures between observation and model prediction, the human DCA PBPK model adequately predicted the DCA plasma kinetics over a 20,000-fold range in administered doses. Apparent inhibition of GSTzeta mediated metabolism of DCA was minimal for low doses of DCA (microg/kg day), but was significant for therapeutic doses of DCA. Plasma protein binding of DCA was assumed to be an important factor influencing the kinetics of low doses of DCA (microg/kg day). Polymorphisms of GSTzeta may help explain inter-individual variability in DCA plasma kinetics and warrants evaluation. In conclusion, using a previously published rodent DCA PBPK model (Keys, D.A., Schultz, I.R., Mahle, D.A., Fisher, J.W., 2004. A quantitative description of suicide inhibition of dichloroacetic acid in rats and mice. Toxicol. Sci. 82, 381-393) and this human DCA PBPK model, human equivalent doses (HEDs) were calculated for a 10% increase in mice hepatic

  15. Evaluation of medium components by Plackett-Burman statistical design for lipase production by Candida rugosa and kinetic modeling.

    Rajendran, Aravindan; Palanisamy, Anbumathi; Thangavelu, Viruthagiri

    2008-03-01

    Lipase production by Candida rugosa was carried out in submerged fermentation. Plackett-Burman statistical experimental design was applied to evaluate the fermentation medium components. The effect of twelve medium components was studied in sixteen experimental trials. Glucose, olive oil, peptone and FeCl3.6H2O were found to have more significance on lipase production by Candida rugosa. Maximum lipase activity of 3.8 u mL(-1) was obtained at 50 h of fermentation period. The fermentation was carried out at optimized temperature of 30 degrees C, initial pH of 6.8 and shaking speed of 120 r/min. Unstructured kinetic models were used to simulate the experimental data. Logistic model, Luedeking-Piret model and modified Luedeking-Piret model were found suitable to efficiently predict the cell mass, lipase production and glucose consumption respectively with high determination coefficient(R2). From the estimated values of the Luedeking-Piret kinetic model parameters, alpha and beta, it was found that the lipase production by Candida rugosa is growth associated. PMID:18589820

  16. Evaluation of Medium Components by Plackett-Burman Statistical Design for Lipase Production by Candida rugosa and Kinetic Modeling

    Aravindan Rajendran; Anbumathi Palanisamy; Viruthagiri Thangavelu

    2008-01-01

    Lipase production by Candida rugosa was carried out in submerged fermentation. Plackett-Burman statistical experimental design was applied to evaluate the fermentation medium components. The effect of twelve medium components was studied in sixteen experimental trials.Glucose,olive oil,peptone and FeCl3·6H2O were found to have more significance on lipase production by Candida rugosa. Maximum lipase activity of 3.8 u mL-1 was obtained at 50 h of fermentation period. The fermentation was carried out at optimized temperature of 30℃, initial pH of 6.8 and shaking speed of 120 r/min. Unstructured kinetic models wereused to simulate the experimental data. Logistic model, Luedeking-Piret model and modified Luedeking-Piret model were foundsuitable to efficiently predict the cell mass, lipase production and glucose consumption respectively with high determination coefficient(R2). From the estimated values of the Luedeking-Piret kinetic model parameters, α and β, it was found that the lipase production by Candida rugosa is growth associated.

  17. Ionizing radiation induced attachment reactions of nucleic acids and their components

    An extensive bibliographic review is given of experimental and theoretical data on radiation-induced attachment reactions of nucleic acids and their components. Mechanisms of these reactions are reviewed. The reactions with water, formate, and alcohols, with amines and other small molecules, and with radiation sensitizers and nucleic acid-nucleic acid reactions are discussed. Studies of the reaction mechanisms show that many of the reactions occur by radical-molecule reactions, but radical-radical reactions also occur. Radiation modifiers become attached to nucleic acids in vitro and in vivo and there are indications that attachment may be necessary for the action of some sensitizers. (U.S.)

  18. Slow component of VO2 kinetics: Mechanistic bases and practical applications

    Jones, Andrew M; Grassi, Bruno; Christensen, Peter Møller; Krustrup, Peter; Bangsbo, Jens; Poole, David C

    2011-01-01

    with the progressive recruitment of additional (type II) muscle fibers that are presumed to have lower efficiency. Recent studies, however, indicate that muscle efficiency is also lowered (resulting in a 'mirror-image'V¿O2 slow component) during fatiguing, high-intensity exercise in which additional...... fiber recruitment is unlikely or impossible. Therefore, it appears that muscle fatigue underpins the V¿O2 slow component, although the greater fatigue-sensitivity of recruited type II fibers might still play a crucial role in the loss of muscle efficiency in both situations.Several interventions can...

  19. Kinetics of the oxidative hydroxylation of sodium hypophosphite in the presence of copper (II) chloride modified by humic (fulvo-) acid

    Zhaksyntay Kairbekov; Dina Akbayeva; Zhaniya Eshova; M. Bazhanovа

    2012-01-01

    It was established that in soft conditions (50-70oC, PO2 = 1 atm) sodium hypophosphite effectively is oxidized by oxygen in water solutions of copper(II) chloride  to give mainly a phosphorous acid. Humic (fulvo-) acid was extracted from brown coal of domestic deposit Kiyakty. For determination of optimum parameters of fulvo-acid extraction the laboratory experiments were carried out using the method of experiment planning. The kinetics, the intermediate and final products, optimal conditions...

  20. Effect of preliminary mechanical manganese tungstate activation on the kinetics of its decomposition by sulfuric acid

    Effect of mechanical manganese tungstate activation on the rate of its decomposition by the sulfuric acid has been investigated. Activation is carried out in the laboratory centrifugal planetary grinder (CPG) of periodic action operating under the impact-wearing down mode with centrifugal acceleration of balls with ∼ 5 mm in diameter (alloy VK-8) ∼ 25 g. ''Dry'' activation (grinding in the air) has been carried out at the ratio of balls to the concentrate by mass 1050:50 g; ''wet'' activation (grinding in water pulp) - at the ratio of balls : concentrate : water by mass 1000:50:50 g. Time of activation varies from 5 to 15 min. Grinding of manganese tungstate concentrates in the apparatuses of the CPG type both in the air and in water pulp is shown to lead to deep structure changes in manganese tungstate activated the further process of concentrate decomposition by the sulfuric acid. Sharp increase of rate and degree of manganese tungstate concentrates decomposition by sulfuric acid solutions has been established on the basis of the kinetics investigation that opens the way for application of decomposition by the sulfuric acid during tungsten raw material reprocessing

  1. Kinetics and Mechanism of Oxidation of Methimazole by Chlorite in Slightly Acidic Media.

    Chipiso, Kudzanai; Simoyi, Reuben H

    2016-06-01

    The kinetics and mechanism of the oxidation of methimazole (1-methyl-3H-imidazole), MMI, by chlorite in mildly acidic environments were studied. It is a complex reaction that gives oligo-oscillations in chlorine dioxide concentrations in excess chlorite conditions. The stoichiometry is strictly 2:1, with the sulfur center being oxidized to sulfate and the organic moiety being hydrolyzed to several indeterminate species. In excess MMI conditions over chlorite, the sulfinic acid and sulfonic acid were observed as major intermediates. The sulfenic acid, which was observed in the electrochemical oxidation of MMI, was not observed with chlorite oxidations. Initial reduction of chlorite produced HOCl, an autocatalytic species in chlorite oxidations. HOCl rapidly reacts with chlorite to produce chlorine dioxide, which, in turn, reacts rapidly with MMI to produce more chlorite. The reaction of chlorine dioxide with MMI is competitive, in rate, with the chlorite-MMI and HOCl-ClO2(-) reactions. This explains the oligo-oscillations in ClO2 concentrations. PMID:27126471

  2. Carbon-13 kinetic isotope effects in the decarbonylations of lactic acid containing 13C at the natural abundance level

    The 13C kinetic isotope fractionation in the decarbonylation of lactic acid of natural isotopic composition by sulfuric acid has been studied in the temperature range of 20-80 deg C. The 13C(1) isotope separation in the decarbonylation of lactic acid by concentrated sulfuric acid depends strongly on the temperature above 40 deg C. Below this temperature the 13C isotope effect in the decarbonylation of lactic acid by concentrated sulfuric acid is normal similarly as has been found in the decarbonylation of lactic [1-14C] acid. The experimental values of k(12C)/k(13C) ratios of isotopic rate constants for 12C and 13C are close to, but slightly higher than theoretical 13C-kinetic isotope effects calculated (neglecting tunneling) under the asumption that the C(1)-OH bond is broken in the rate-controlling step of the dehydration reaction. Dilution of concentrated sulfuric acid with water up to 1.4 molar (H2O)/(H2SO4) ratio caused the increase of the 13C isotope fractionation from 1.0273 found in concentrated sulfuric acid at 80.5 deg C to 1.0536±0.0008 (at 80.6 deg C). A discussion of the abnormally high temperature dependence of 14C and 13C isotope fractionation in this reaction and the discussion of the problem of relative 14C/13C kinetic isotope effects is given. (author) 18 refs.; 2 tabs

  3. Shikimic acid ozonolysis kinetics of the transition from liquid aqueous solution to highly viscous glass.

    Steimer, Sarah S; Berkemeier, Thomas; Gilgen, Anina; Krieger, Ulrich K; Peter, Thomas; Shiraiwa, Manabu; Ammann, Markus

    2015-12-14

    Ageing of particulate organic matter affects the composition and properties of atmospheric aerosol particles. Driven by temperature and humidity, the organic fraction can vary its physical state between liquid and amorphous solid, or rarely even crystalline. These transitions can influence the reaction kinetics due to limitations of mass transport in such (semi-) solid states, which in turn may influence the chemical ageing of particles containing such compounds. We have used coated wall flow tube experiments to investigate the reaction kinetics of the ozonolysis of shikimic acid, which serves as a proxy for oxygenated, water-soluble organic matter and can form a glass at room temperature. Particular attention was paid to how the presence of water influences the reaction, since it acts a plasticiser and thereby induces changes in the physical state. We analysed the results by means of a traditional resistor model, which assumes steady-state conditions. The ozonolysis rate of shikimic acid is strongly increased in the presence of water, a fact we attribute to the increased transport of O3 and shikimic acid through the condensed phase at lower viscosities. The analysis using the resistor model suggests that the system undergoes both surface and bulk reaction. The second-order rate coefficient of the bulk reaction is 3.7 (+1.5/-3.2) × 10(3) L mol(-1) s(-1). At low humidity and long timescales, the resistor model fails to describe the measurements appropriately. The persistent O3 uptake at very low humidity suggests contribution of a self-reaction of O3 on the surface. PMID:26536455

  4. The Effect of Oxygen Supply on the Dual Growth Kinetics of Acidithiobacillus thiooxidans under Acidic Conditions for Biogas Desulfurization

    Hyeong-Kyu Namgung; JiHyeon Song

    2015-01-01

    In this study, to simulate a biogas desulfurization process, a modified Monod-Gompertz kinetic model incorporating a dissolved oxygen (DO) effect was proposed for a sulfur-oxidizing bacterial (SOB) strain, Acidithiobacillus thiooxidans, under extremely acidic conditions of pH 2. The kinetic model was calibrated and validated using experimental data obtained from a bubble-column bioreactor. The SOB strain was effective for H2S degradation, but the H2S removal efficiency dropped rapidly at DO ...

  5. Atomic kinetic Monte Carlo modeling of multi-component Fe dilute alloys under irradiation

    The ageing of pressure vessel steels under radiation has been correlated with the formation of more or less dilute solute clusters which are investigated in this work using a multi-scale approach based on ab initio and atomistic kinetic Monte Carlo (AKMC) simulations. The microstructure evolution of Fe alloys is modeled by AKMC on a lattice, using pair interactions adjusted on DFT (Density Functional Theory) calculations. Several substitutional elements (Cu, Ni, Mn, Si, P) and foreign interstitials (C, N) are taken into account to describe the alloy. The point defect created by the irradiation, i.e. the vacancies and self interstitials have a tendency to form clusters. The evolution of these clusters is governed by the migration energy of the individual point defects which is very heavy in terms of computing time due to the large number of AKMC steps required. The structure of all the possible objects that can form is complex and some optimized and accelerated methods will be presented. The results obtained are in agreement with the experimental trends and indicate that the formation of solute clusters takes place via segregation mechanisms on the point defect clusters

  6. Kinetic investigation of the oxidation of N-alkyl anilines by peroxomonophosphoric acid in anionic surfactant sodium lauryl sulphate

    G P Panigrahi; Jagannath Panda

    2000-12-01

    Kinetics of oxidation of N-methyl and N-ethyl aniline by peroxomono-phosphoric acid (PMPA) in aqueous and 5% (v/v) acetonitrile medium respectively have been studied in presence of anionic micelles of sodium lauryl sulphate (SLS) at different H. Oxidation rate of both the substrates increases up to a certain [SLS] much below the critical micellar concentration (cmc) after which the rate is retarded. Kinetic data have been used to compute the binding constants of both substrate and oxidant with the micelle. A scheme explaining the kinetic data has been proposed.

  7. Labelling of nucleic acid components with tritium by hydrogenolysis of corresponding precursors

    To desalt the luates of liquid column chromatography containing components of the nucleic acids different types of activated carbons are used: AG-5, Ou-4, KAD, BAU (SU), Norit (GB) and Carboafin (CS). The Carborafin (CS) carbon proved to be the most efficient for the purpose. Dependences of the adsorption degree on pH, the time of the phases contact, temperature, concentration of the salt background (ammonium formite, lithium chloride) as well as adsorption isotherm are determined for the activated carbon. Desorption conditions of the nucleic acids components from the carbon are studied. It is shown that quantitative desorption is achieved when 1n solution of ammonia is used in 50% ethanole for 50-60 min. Data on practical application of the method to desalt the eluates containing tritiated nucleic acid components with a high activity are presented

  8. An Analytical Model Approach for the Dissolution Kinetics of Magnesite Ore Using Ascorbic Acid as Leaching Agent

    Nadeem Raza

    2013-01-01

    Full Text Available Ascorbic acid was used as leaching agent to investigate the dissolution kinetics of natural magnesite ore. The effects of various reaction parameters such as acid concentration, liquid-solid ratio, particle size, stirring speed, and temperature were determined on dissolution kinetics of the magnesite ore. It was found that the dissolution rate increased with increase in acid concentration, liquid-solid ratio, stirring speed, and temperature and decrease in the particle size of the ore. The graphical and statistical methods were applied to analyze the kinetic data, and it was evaluated that the leaching process was controlled by the chemical reaction, that is, . The activation energy of the leaching process was found to be 57.244 kJ mol−1 over the reaction temperature range from 313 to 343 K.

  9. Spectrophotometric method for fast quantification of ascorbic acid and dehydroascorbic acid in simple matrix for kinetics measurements.

    Gómez Ruiz, Braulio; Roux, Stéphanie; Courtois, Francis; Bonazzi, Catherine

    2016-11-15

    A simple, rapid and reliable method was developed for quantifying ascorbic (AA) and dehydroascorbic (DHAA) acids and validated in 20mM malate buffer (pH 3.8). It consists in a spectrophotometric measurement of AA, either directly on the solution added with metaphosphoric acid or after reduction of DHAA into AA by dithiothreitol. This method was developed with real time measurement of reactions kinetics in bulk reactors in mind, and was checked in terms of linearity, limits of detection and quantification, fidelity and accuracy. The linearity was found satisfactory on the range of 0-6.95mM with limits of detection and quantification of 0.236mM and 0.467mM, respectively. The method was found acceptable in terms of fidelity and accuracy with a coefficient of variation for repeatability and reproducibility below 6% for AA and below 15% for DHAA, and with a recovery range of 97-102% for AA and 88-112% for DHAA. PMID:27283671

  10. Kinetics of Glycoxidation of Bovine Serum Albumin by Glucose, Fructose and Ribose and Its Prevention by Food Components

    Izabela Sadowska-Bartosz

    2014-11-01

    Full Text Available The aim of this study was to compare the kinetics of the glycoxidation of bovine serum albumin (BSA as a model protein by three sugars: glucose, fructose and ribose, using fluorometric measurements of the content of advanced glycation end products (AGEs, protein-bound fructosamine, dityrosine, N'-formylkynurenine, kynurenine, tryptophan, the content of advanced oxidation protein products (AOPP, protein carbonyl groups, as well as thiol groups. Moreover, the levels of glycoalbumin and AGEs were determined by using an enzyme-linked immunosorbent assay. Based on the kinetic results, the optimal incubation time for studies of the modification of the glycoxidation rate by additives was chosen, and the effects of 25 compounds of natural origin on the glycoxidation of BSA induced by various sugars were examined. The same compounds were found to have different effects on glycoxidation induced by various sugars, which suggests caution in extrapolation from experiments based on one sugar to other sugars. From among the compounds tested, the most effective inhibitors of glycoxidation were: polyphenols, pyridoxine and 1-cyano-4-hydroxycinnamic acid.

  11. KINETIC STUDY OF PALMITIC ACID ESTERIFICATION CATALYZED BY Rhizopus oryzae RESTING CELLS

    RAMON CANELA

    2009-04-01

    Full Text Available

    ABSTRACT

    In the present study, a kinetic model for the biocatalytic synthesis of esters using Rhizopus oryzae resting cells is proposed. The kinetic study has been made in a range of 30-50 °C and atmospheric pressure. The Influence of operating variables, water content, pH, amount of mycelium was studied. Different values of temperature, initial mycelium concentration and acid/alcohol molar ratio were tested. Initial rates were estimated from the slope of the concentration of palmitic acid, or their corresponding ester at conversions of less than 10%, versus time and reported as mmol l-1 min -1. The values of kinetic constants were computed using the freeware program SIMFIT (http:\\www.simfit.man.ac.uk.

    Key words: bound lipase, esterification, fungal resting cells, Rhizopus oryzae, palmitic acid, propanol.


    RESUMEN

    En el presente estudio, un modelo cinético para la síntesis de esteres usando Rhizopus oryzae resting cells es propuesto. El estudio cinético fue realizado en un rango de temperatura de 30-50 ºC a presión atmosférica reducida. La influencia de las variables de operación tales como temperatura, pH y contenido de agua fueron estudiadas. Diferentes valores de concentración de micelio y relación molar de ácido/alcohol son ensayadas, Las velocidades iníciales se estimaron de la curva de concentración de acido palmítico, y su correspondiente conversión a ester en menos del 10%, frente a tiempo y reportadas en mmol I-1 min -1. Los valores de las constantes cinéticas fueron calculados usando el programa freeware SIMFIT (http:\\www.simfit.man.ac.uk.

    Palabras clave: Lipasas, esterificación, resting cells, Rhizopus oryzae, acido palmítico, propanol.

  12. Kinetic Studies on Wheat Straw Hydrolysis to Levulinic Acid%小麦秸秆制备乙酰丙酸的动力学研究

    常春; 马晓建; 岑沛霖

    2009-01-01

    Levulinic acid is considered as a promising green platform chemical derived from biomass. The kinetics of levulinic acid accumulation in the hydrolysis process of wheat straw was investigated in the study. Using dilute sulfuric acid as a catalyst, the kinetic experiments were performed in a temperature range of 190-230℃ and an acid concentration range of 1%-5% (by mass). A simple model of first-order series reactions was developed, which provided a satisfactory interpretation of the experimental results. The kinetics of main intermediates including sugar and 5-hydroxymethylfurfural (5-HMF) were also established. The kinetic parameters provided useful information for understanding the hydrolysis process.

  13. Accumulation and kinetics of 90Sr in fishes and other components of an artificial aquatic system

    Regularities are described of 90Sr transfer from water into the particular components of a simplified experimental aquatic system - the sediments, algae, invertebrates (gastropods) and fish - based on a model experiment simulating conditions of a section of the Jihlava River as influenced by the release of liquid wastes from the Dukovany nuclear power plant. Owing to their high abundance, both in nature and in the experiment, the aquatic algae and sediments are the most important accumulators of 90Sr. Nevertheless, the highest increase in the specific radionuclide concentrations and in the accumulation coefficients were found in aquatic gastropods and in fish bones. (author). 1 tab., 12 refs

  14. Catalytic Kinetic Determination of Micro Amounts of Oxalic Acid by Second-Order Derivative Oscillopolarography

    2001-01-01

    It was found that micro amounts of oxalate showed a very strong catalytic effect on the slow reaction between K2Cr2O7 and Orange Ⅳ in a diluted sulfuric acid medium in a water bath at 70 ℃. Orange Ⅳ exhibited a sensitive second-order derivative polarographic wave at -0.50 V(vs. SCE). This provides the basis for a sensitive and selective catalytic kinetic method for oxalate determination with second-order derivative oscillopolarography. The effects of sulphuric acid, K2Cr2O7, and orange Ⅳ concentrations, reaction temperature and reaction time were investigated. A calibration curve of oxalate in the range of 0.1—2.0 μg/mL was obtained by the fixed-time procedure. The detection limit was 0.03 μg/ mL. The possible interference from co-existing substances or ions was examined. The new method has a high sensitivity and a good selectivity compared to other existing methods for oxalic acid determination. It has been applied to the determination of micro amounts of oxalate in real urine samples with satisfactory results.

  15. The Inherent Reactor Kinetics for Transformation of Geniposidic Acid from Geniposide in a Microreactor

    Chiu-Lan Hsieh

    2015-01-01

    Full Text Available The ripe fruits of Gardenia jasminoides Ellis (Rubiaceae (GJ are widely used in chemical, food and medicinal industries. Crocin and geniposide, the main constituents of GJ, have shown a diversity of biological activities including sedative, anti-inflammatory and antipyretic. We propose some new bioactive chemicals could be derived from geniposide. The optimum transformation condition of geniposide into geniposidic acid still remains unclear. In order to develop a reactor, the information about the inherent reaction kinetics is required. In a microreactor (V =62.8 mL, geniposide (0.01 mole/L, 20 mL and NaOH (0.1 equivalent/L, pH=13, 10mL were left to react at 80, 70, 60, 50, and 40 oC and tracked with HPLC. Results indicated that the reaction obeyed the pseudo-first order kinetics, the corresponding pseudo-first order rate constants ( 1 k ' were 11.064 h -1 , 8.682 h -1 , 2.400 h -1 , 1.021 h -1 , and 0.750 h-1 , and the fractional conversions were 73.4%, 60.5%, 38.6%, 43.6%, and 51.8% at 0.50, 0.50, 0.833, 1.00, and 2.00 h. The energy of activation was 8.751 kJ mol-1 . Conclusively, this transformation obeys the pseudo-first order kinetics with a low energy of activation, 8.751 kJ mol-1 . The optimum transformations at 80oC and 70oC for 0.5 h were 73.4% and 60.5%, respectively.

  16. THE EFFECT OF EMI EHF ON ELECTRO - KINETIC POTENTIAL OF CELL NUCLEAR MEMBRANES OF WHEAT SEEDLINGS TREATED WITH HYBBERELLIC ACID

    Vardevanyan Poghos O

    2013-09-01

    Full Text Available The effect of hybberellic acid and EMI EHF on electro kinetic potential changes of cell nuclear membrane of wheat seedlings has been investigated. It was revealed that electro kinetic potential value depends on functional state of plant organism. It was reported that the treatment of wheat germs with hybberellic acid and EMI EHF induces a change of nuclear membrane surface charge. It was revealed that the combined influence of chemical as well as physical factors induces more pronounced response on biological systems as compared to separately. It was also observed that the effect of EMI EHF has significant effect on water resonant frequencies as compared to water non- resonant frequencies.

  17. Kinetic Modelling for Flavonoid Recovery from Red Grape (Vitis vinifera Pomace with Aqueous Lactic Acid

    Katerina Tzima

    2014-12-01

    Full Text Available This study was undertaken with the aim of establishing a correlation between the extraction yield in total flavonoids from red grape pomace and the extraction temperature, using 0.5% (w/v aqueous lactic acid as the solvent system. Extraction of flavonoids was found to obey second-order kinetics, and on such a basis, the yield in total flavonoids at saturation could be very effectively determined and correlated with temperature using non-linear regression. The results indicated that the extraction yield at saturation is highly correlated with temperature, following a quadratic function. The extract obtained at 40 °C had an optimal predicted total flavonoid yield of 13.27 mg rutin equivalents per gram of dry weight, and it was further analyzed by liquid chromatography-mass spectrometry to characterize its major constituents. The polyphenols detected were flavanols, flavonols and an anthocyanin. The outcome of this study outlined that temperatures above 40 °C are rather unfavorable for flavonoid extraction from red grape pomace, as suggested by the model established through kinetics.

  18. Dynamic modeling of in vitro lipid digestion: individual fatty acid release and bioaccessibility kinetics.

    Giang, T M; Gaucel, S; Brestaz, P; Anton, M; Meynier, A; Trelea, I C; Le Feunteun, S

    2016-03-01

    The aim of this study was to gain knowledge about the role of triacylglycerol (TAG) composition in fatty acids (FA) of o/w emulsions on both the pancreatic lipolysis kinetics and the bioaccessibility of released products (i.e. contained within the bile salt micellar phase). A mathematical model was developed and its predictions were compared to a set of experimental data obtained during an in vitro digestion of a whey protein stabilized emulsion. Modeling results show that FA residues of TAG were hydrolyzed at specific rates, inducing different bioaccessibility kinetics. The estimated lipolysis rate constants of the studied FA (C8:0, C10:0≫C18:1 n-9≫C12:0>C14:0>C16:0≈C16:1 n-7>C22:6 n-3) were in close agreement with the available literature on the substrate specificity of pancreatic lipase. Results also suggest that lipolysis products are very rapidly solubilized in the bile salt mixed micelles with no fractionation according to the FA carbon chain. PMID:26471670

  19. Aqueous chlorination of mefenamic acid: kinetics, transformation by-products and ecotoxicity assessment.

    Adira Wan Khalit, Wan Nor; Tay, Kheng Soo

    2016-05-18

    Mefenamic acid (Mfe) is one of the most frequently detected nonsteroidal anti-inflammatory drugs in the environment. This study investigated the kinetics and the transformation by-products of Mfe during aqueous chlorination. The potential ecotoxicity of the transformation by-products was also evaluated. In the kinetic study, the second-order rate constant (kapp) for the reaction between Mfe and free available chlorine (FAC) was determined at 25 ± 0.1 °C. The result indicated that the degradation of Mfe by FAC is highly pH-dependent. When the pH was increased from 6 to 8, it was found that the kapp for the reaction between Mfe and FAC was decreased from 16.44 to 4.4 M(-1) s(-1). Characterization of the transformation by-products formed during the chlorination of Mfe was carried out using liquid chromatography-quadrupole time-of-flight accurate mass spectrometry. Four major transformation by-products were identified. These transformation by-products were mainly formed through hydroxylation, chlorination and oxidation reactions. Ecotoxicity assessment revealed that transformation by-products, particularly monohydroxylated Mfe which is more toxic than Mfe, can be formed during aqueous chlorination. PMID:27062128

  20. Formic Acid Decomposition on Au catalysts: DFT, Microkinetic Modeling, and Reaction Kinetics Experiments

    Singh, Suyash; Li, Sha; Carrasquillo-Flores, Ronald; Alba-Rubio, Ana C.; Dumesic, James A.; Mavrikakis, Manos

    2014-04-01

    A combined theoretical and experimental approach is presented that uses a comprehensive mean-field microkinetic model, reaction kinetics experiments, and scanning transmission electron microscopy imaging to unravel the reaction mechanism and provide insights into the nature of active sites for formic acid (HCOOH) decomposition on Au/SiC catalysts. All input parameters for the microkinetic model are derived from periodic, self-consistent, generalized gradient approximation (GGA-PW91) density functional theory calculations on the Au(111), Au(100), and Au(211) surfaces and are subsequently adjusted to describe the experimental HCOOH decomposition rate and selectivity data. It is shown that the HCOOH decomposition follows the formate (HCOO) mediated path, with 100% selectivity toward the dehydrogenation products (CO21H2) under all reaction conditions. An analysis of the kinetic parameters suggests that an Au surface in which the coordination number of surface Au atoms is 4 may provide a better model for the active site of HCOOH decomposition on these specific supported Au catalysts.

  1. Dissolution kinetics of manganese dioxide ore in sulfuric acid in the presence of ferrous ion

    In this paper, kinetics of reductive leaching of manganese dioxide ore by ferrous ion in sulfuric acid media has been examined. Experimental results show that increasing temperature from 20 to 60 degC and decreasing are particle size from -16+20 to -60+100 mesh considerably enhance both the dissolution rate and efficiency. Molar ratios of Fe2+/MnO2 and H2SO4/MnO2 in excess to the stoichiometric amounts were needed for successful manganese dissolution. Under the optimum condition (are particle size of -60+100 mesh, Fe2+/MnO2 molar ratio of 3.0, H2SO4/MnO2 molar ratio of 2.0) manganese could be extracted with 95% efficiency by 20 minutes leaching at room temperature. A kinetic analysis based on dimensionless time method showed that shrinking core -ash diffusion control model fits the experimental results reasonably well. Value of activation energy was found to be 28.1 kJ/mole for the proposed mechanism

  2. Dissolution kinetics of uranium from a low grade uranium ore in acid lixiviant

    Kinetic studies on uranium dissolution were carried out on an uranium ore sample from Narwapahar, Jharkhand and a pre-concentrate obtained by physical beneficiation of the ore sample. The dissolution was effected by leaching the feed sample with sulphuric acid at a pH of 1.6-1.8 at 50 deg C with pyrolusite (MnO2) as the oxidant. The uranium dissolution was monitored at fixed time intervals by drawing samples and analyzing for the U3O8 content. It was continued up to a cumulative contact time of 12 hours. The experimental data was analyzed using 'shrinking unreacted core' (SUC) model. During the initial stages, the leaching was found to be chemical-reaction controlled and subsequently diffusion controlled. The rate constants for the uranium dissolution under the two different mechanisms have been estimated. (author)

  3. Kinetics and mechanism of the reaction of fluorine atoms with pentafluoropropionic acid.

    Vasiliev, E S; Knyazev, V D; Karpov, G V; Morozov, I I

    2014-06-12

    The kinetics of the reaction between fluorine atoms and pentafluoropropionic acid has been studied experimentally at T = 262-343 K. The overall reaction rate constant decreases with temperature: k1(T) = 6.1 × 10(-13) exp(+1166 K)/T) cm(3) molecule(-1) s(-1). The potential energy surface of the reaction has been studied using quantum chemistry. The results were used in transition state theory calculations of the temperature dependences of the rate constants of the two channels of the reaction. The abstraction channel ultimately producing HF, C2F5, and CO2 is dominant at the experimental temperatures; the addition-elimination channel producing C2F5 and CF(O)OH becomes important above 1000 K. PMID:24819330

  4. Intrinsic oxidation kinetics of sulfite catalyzed by peracetic acid under different water quality and light conditions

    2009-01-01

    Oxidation of sulfite is an important process in wet flue gas desulfurization.Using highly purified water or distilled water as a reaction medium and a transparent or an opaque intermittent reaction apparatus,the intrinsic oxidation kinetics of sulfite catalyzed by peracetic acid was investigated under four dif-ferent conditions.The reaction order of the reagents and the activation energy were obtained.The re-sults indicate that water quality and light have no obvious effects on the reaction order and activation energy,but have an influence on the reaction rate constant.The mechanism of the intrinsic reaction is proposed.The results derived with this mechanism are in good agreement with the experimental re-sults.

  5. Kinetic studies of acid inactivation of alpha-amylase from Aspergillus oryzae

    Carlsen, Morten; Nielsen, Jens Bredal; Villadsen, John

    1996-01-01

    The stability of alpha-amylase from Aspergillus oryzae has been studied at different pH. The enzyme is extremely stable at neutral pH (pH 5-8), whereas outside this pH-range a substantial loss of activity is observed. The acid-inactivation of alpha-amylase from A. oryzae was monitored on-line by a...... regains part of its activity, and the reactivation process also follows first-order kinetics. The irreversible loss of activity is found not to result from a protease contamination of the protein samples. A proposed model, where irreversibly inactivated a-amylase is formed both directly from the active...

  6. Kinetics of oxidation and dissolution of uranium dioxide in aqueous acid solutions

    The oxidation and dissolution of UO2 has been studied using electrochemical methods with an UO2 rotating disc electrode in acidic (pH 3) and non-complexing (trifluoromethanesulfonate: 0.1 mol L−1 NaCF3SO3) media. The effect of the experimental parameters such as scan rate (v) and rotation rate (ω) on the electrochemical signal has been studied. The rotation rate of the electrode does not influence the resulting signal, which indicates that only a charge transfer is involved in the UO2 oxidation kinetic. However, scan rate variations show different reactions involved in the UO2 oxidation. Linear sweep voltammetry and cyclic voltammetry coupled to X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS) measurements suggest two successive electrochemical reactions with an exchange of one electron for each of them and the formation of one intermediate species of U(V).

  7. Kinetic of the COLUMBO-TANTALITE dissolution in aqueous solutions of hydrofluoric acid

    The dissolution rate of a columbo-tantalite of the San Luis Province in aqueous solutions of hydrofluoric acid has been studied.Experiments at different temperatures were carried out in a pressure reactor.The experimental results show that the mineral dissolution increases with the reaction time.This effect is greater when the temperature increases from 348 up to 396 K, but it is little 493 K. The experimental data were treated with different models, which have been deduced for the kinetic study of solid-fluid non-catalytic heterogeneous reactions. As a result, the better model that fit the experimental data is a model based on the nucleation and growth theory.This model is physically according to the attack observed by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDXS) on the mineral residues.These residues show an irregular located-type attack

  8. Kinetics of oxidation of pentavalent neptunium by pentavalent vanadium in solutions of nitric acid

    Precek, Martin; Paulenova, Alena

    2010-03-01

    Management of the oxidation state of neptunium in the reprocessing of spent nuclear fuel by solvent extraction is very important. The kinetics of the oxidation of neptunium(V) by vanadium(V) in solutions of nitrate acid was investigated at constant ionic strength 4M. The reaction rate is first order with respect to Np(V) and V(V). The effects of proton concentration on the apparent second order rate constant k1" was determined for temperature 25°C as k1" = (0.99±0.03)·[H+]1.21M-1s-1. Activation parameters associated with the overall reaction have been calculated; the standard reaction enthalpy and entropy were 52.6±0.9 kJ/mol and -55.8±0.9 J/K/mol respectively.

  9. Kinetic study of enzymatic hydrolysis of acid-pretreated coconut coir

    Fatmawati, Akbarningrum; Agustriyanto, Rudy

    2015-12-01

    Biomass waste utilization for biofuel production such as bioethanol, has become more prominent currently. Coconut coir is one of lignocellulosic food wastes, which is abundant in Indonesia. Bioethanol production from such materials consists of more than one step. Pretreatment and enzymatic hydrolysis is crucial steps to produce sugar which can then be fermented into bioethanol. In this research, ground coconut coir was pretreated using dilute sulfuric acid at 121°C. This pretreatment had increased the cellulose content and decreased the lignin content of coconut coir. The pretreated coconut coir was hydrolyzed using a mix of two commercial cellulase enzymes at pH of 4.8 and temperature of 50°C. The enzymatic hydrolysis was conducted at several initial coconut coir slurry concentrations (0.1-2 g/100 mL) and reaction times (2-72 hours). The reducing sugar concentration profiles had been produced and can be used to obtain reaction rates. The highest reducing sugar concentration obtained was 1,152.567 mg/L, which was produced at initial slurry concentration of 2 g/100 mL and 72 hours reaction time. In this paper, the reducing sugar concentrations were empirically modeled as a function of reaction time using power equations. Michaelis-Menten kinetic model for enzymatic hydrolysis reaction is adopted. The kinetic parameters of that model for sulfuric acid-pretreated coconut coir enzymatic hydrolysis had been obtained which are Vm of 3.587×104 mg/L.h, and KM of 130.6 mg/L.

  10. Kinetics of the oxidative hydroxylation of tetraphosphorus in the presence of copper(II) chloride modified by humic (fulvo-) acid

    Zhaksyntay Kairbekov; Dina Akbayeva; Zh. Eshova

    2012-01-01

    It was established that in mild conditions (50-70 oC, РО2= 1 atm) white phosphorus effectively is oxidized by oxygen in water-toluene solutions of copper(II) chloride modified by humic (fulvo-) acid to give mainly phosphoric acid. Humic (fulvo-) acid was extracted from brown coal of domestic deposit Kiyakty. For determination of optimum parameters of fulvo-acid extraction the laboratory experiments were carried out using the method of experiment planning. The kinetics, intermediate and final ...

  11. A component of platypus (Ornithorhynchus anatinus) venom forms slow-kinetic cation channels.

    Kourie, J I

    1999-11-01

    The lipid bilayer technique is used to examine the biophysical properties of anion and cation channels frequently formed by platypus (Ornithorhynchus anatinus) venom (OaV). The OaV-formed anion channel in 250/50 mm KCl cis/trans has a maximum conductance of 857 +/- 23 pS (n = 5) in 250/50 mm KCl cis/trans. The current-voltage relationship of this channel shows strong inward rectification. The channel activity undergoes time-dependent inactivation that can be removed by depolarizing voltage steps more positive than the reversal potential for chloride, E(Cl), (+40 mV). The reversal potential of the OaV-formed slow current activity in 250/50 mm KCl cis/trans is close to the potassium equilibrium potential (E(K)) of -40 mV. The conductance values for the slow channel are 22.5 +/- 2.6 pS and 41.38 +/- 4.2 pS in 250/50 and 750/50 mm cis/trans, respectively. The gating kinetics of the slow ion channels are voltage-dependent. The channel open probability (P(o)) is between 0.1 and 0.8 at potentials between 0 and +140 mV. The channel frequency (F(o)) increases with depolarizing voltages between 0 and +140 mV, whereas mean open time (T(o)) and mean closed time (T(c)) decrease. Ion substitution experiments of the cis solution show that the channel has conductance values of 21.47 +/- 2. 3 and 0.53 +/- 0.1 pS in 250 mm KCl and choline Cl, respectively. The amplitude of the single channel current is dependent on [K(+)](cis) and the current reversal potential (E(rev)) responds to increases in [K(+)](cis) by shifting to more negative voltages. The increase in current amplitude as a function of increasing [K(+)](cis) can be best described by a third order polynomial fit. At +140 mV, the values of the maximal single channel conductance (gamma(max)) and the concentration for half maximal gamma (K(s)) are 38.6 pS and 380 mm and decline to 15.76 pS and 250 mm at 0 mV, respectively. The ion selectivity of the channel to K(+), Na(+), Cs(+) and choline(+) was determined in ion substitution

  12. Kinetics of the oxidative hydroxylation of tetraphosphorus in the presence of copper(II chloride modified by humic (fulvo- acid

    Zhaksyntay Kairbekov

    2012-12-01

    Full Text Available It was established that in mild conditions (50-70 oC, РО2= 1 atm white phosphorus effectively is oxidized by oxygen in water-toluene solutions of copper(II chloride modified by humic (fulvo- acid to give mainly phosphoric acid. Humic (fulvo- acid was extracted from brown coal of domestic deposit Kiyakty. For determination of optimum parameters of fulvo-acid extraction the laboratory experiments were carried out using the method of experiment planning. The kinetics, intermediate and final products, optimum conditions of new catalytic reaction of P4 oxidation by oxygen in water medium were defined by kinetics, volumometry, redox-potentiometry, 31Р{1Н} NMR spectroscopy and  titration. 

  13. Effects of Fructus Psoraleae Extract on the Intestinal Absorption Kinetics of Geniposide and Geniposidic Acid in Rat

    Yan Huo

    2014-06-01

    Full Text Available Cortex Eucommia has been used as a kidney-tonifying herbal medicine with a long history of compatibility with Fructus Psoraleae. Geniposide (GP and geniposidic acid (GPA are the two main chemical components in Cortex Eucommia. In the present study, the effects of Fructus Psoraleae extract (FPE on intestinal absorption kinetics of GP and GPA in rat were investigated. Twenty four male Sprague-Dawley rats were randomly assigned into four groups which were treated with GP, GPA, GP mixed with FPE and GPA mixed with FPE, respectively, by in situ intestinal perfusion for 3 h. The samples of intestinal perfusion solutions were collected every 30 min, and analyzed by ultra high performance liquid chromatography (UPLC. The curves of time and residual quantities of GP and GPA (lnx in the intestinal perfusion solution and the cumulative absorption rate were obtained. The results showed that FPE exhibited different effects on the intestinal absorption of GP and GPA in rat: it increased the intestinal absorption of GP (p < 0.05, while demonstrated no significant effect on the absorption of GPA.

  14. 4.2. The kinetics of nitric acid decomposition of calcined borosilicate raw material of Ak-Arkhar Deposit

    Present article is devoted to kinetics of nitric acid decomposition of calcined borosilicate raw material of Ak-Arkhar Deposit. The dependence of nitric acid decomposition of calcined boric raw material for extraction of boron oxide on temperature (20-100 deg C) and process duration (15-60 minutes) was defined. It was defined that at temperature increasing the extraction rate of boron oxide increases from 20.8 to 78.6%.

  15. Potential origin and formation for molecular components of humic acids in soils

    DiDonato, Nicole; Chen, Hongmei; Waggoner, Derek; Hatcher, Patrick G.

    2016-04-01

    Soil humic acids are the base soluble/acid insoluble organic components of soil organic matter. Most of what we know about humic acids comes from studies of their bulk molecular properties or analysis of individual fractions after extraction from soils. This work attempts to better define humic acids and explain similarities and differences for several soils varying in degrees of humification using advanced molecular level techniques. Our investigation using electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) and nuclear magnetic resonance spectroscopy (NMR) has given new insight into the distinctive molecular characteristics of humic acids which suggest a possible pathway for their formation. Humic acids from various ecosystems, climate regions and soil textural classes are distinguished by the presence of three predominant molecular components: lignin-like molecules, carboxyl-containing aliphatic molecules and condensed aromatic molecules that bear similarity to black carbon. Results show that humification may be linked to the relative abundance of these three types of molecules as well as the relative abundance of carboxyl groups in each molecular type. This work also demonstrates evidence for lignin as the primary source of soil organic matter, particularly condensed aromatic molecules often categorized as black carbon and is the first report of the non-pyrogenic source for these compounds in soils. We also suggest that much of the carboxyl-containing aliphatic molecules are sourced from lignin.

  16. KINETIC MODELING AND ISOTHERM STUDIES ON A BATCH REMOVAL OF ACID RED 114 BY AN ACTIVATED PLANT BIOMASS

    N. RAJAMOHAN

    2013-12-01

    Full Text Available In this paper, the dye Acid Red 114(AR 114 was removed from aqueous solutions using Acid-Activated Eichornia Crassipes (AAEC under batch conditions. The optimum conditions for AR 114 removal were found to be pH 1.5, adsorbent dosage = 1.25 g/L of solution and equilibrium time = 3 h. The equilibrium data were evaluated for compliance with Langmuir, Freundlich and Temkin isotherms and Langmuir isotherm was found to fit well. The maximum sorption capacity was estimated as 112.34 mg/g of adsorbent. Also, adsorption kinetics of the dye was studied and the rates of sorption were found to follow pseudo-second order kinetics with good correlation (R2 ≥ 0.997.The kinetic study at different temperatures revealed that the sorption was an endothermic process. The activation energy of the sorption process was estimated as 9.722 kJ/mol.

  17. Kinetics of chronic inflammation in Nile tilapia fed n‑3 and n‑6 essential fatty acids

    Róberson Sakabe

    2013-03-01

    Full Text Available The objective of this work was to investigate the effect of dietary supplementation with essential fatty acids on the kinetics of macrophage accumulation and giant cell formation in Nile tilapia (Oreochromis niloticus. The supplementation sources were soybean oil (SO, source of omega 6, n‑6 and linseed oil (LO, source of omega 3, n‑3, in the following proportions: 100% SO; 75% SO + 25% LO; 50% SO + 50% LO; 25% SO + 75% LO; and 100% LO (four replicates per treatment. After a feeding period of three months, growth performance was evaluated, and glass coverslips were implanted into the subcutaneous connective tissue of fish, being removed for examination at 2, 4, 6, and 8 days after implantation. Growth performance did not differ between treatments. Fish fed 100% linseed oil diet had the greatest macrophage accumulation and the fastest Langhans cell formation on the sixth day. On the eighth day, Langhans cells were predominant on the coverslips implanted in the fish feed 75 and 100% linseed oil. n‑3 fatty acids may contribute to macrophage recruitment and giant cell formation in fish chronic inflammatory response to foreign body.

  18. Oxidation of Tetracaine Hydrochloride by Chloramine-B in Acid Medium: Kinetic Modeling

    Jayachamarajapura Pranesh Shubha

    2014-01-01

    Full Text Available Tetracaine hydrochloride (TCH is one of the potent local anaesthetics. A kinetic study of oxidation of tetracaine hydrochloride by sodium N-chlorobenzenesulfonamide (chloramine-B or CAB has been carried in HClO4 medium at 303 K. The rate shows first-order dependence on [CAB]o, shows fractional–order dependence on [substrate]o, and is self-governing on acid concentration. Decrease of dielectric constant of the medium, by adding methanol, increased the rate. Variation of ionic strength and addition of benzenesulfonamide or NaCl have no significant effect on the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated. The stoichiometry of the reaction was found to be 1 : 5 and the oxidation products were identified by spectral analysis. The conjugate free acid C6H5SO2NHCl of CAB is postulated as the reactive oxidizing species. The observed results have been explained by plausible mechanism and the related rate law has been deduced.

  19. Adsorption of rhodamine B by acid activated carbon-Kinetic, thermodynamic and equilibrium studies

    Shanmugam Arivoli

    2009-08-01

    Full Text Available A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing Rhodamine B (RDB. The parameters studied include agitation time, initial dye concentration, carbon dose, pH and temperature. The adsorption followed first order kinetics and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm obtained from the Langmuir isotherm plots were 40.161, 35.700, 38.462 and 37.979 mg/g respectively at an initial pH of 7.0 at 30, 40, 50 and 60 0C. The temperature variation study showed that the RDB adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the RDB solutions. Almost 85% removal of RDB was observed at 60 0C. The Langmuir and Freundlich isotherms obtained, positive ?H0 value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of RDB by Banana bark carbon involves physisorption mechanism.

  20. Mathematic modelling of kinetics for the crystallization of tungstic acid from electrolytically treated sodium tungstate solution

    The nucleation and growth rate kinetics for the continuous crystallization of tungstic acid from solution was studied in a 0.8 1 evaporative mixed suspension, mixed product removal crystallizer. The crystallizer included a draft tube which improved the uniformity of the suspension. Experimental conditions which were varied during the experimental runs were drawdown time of the crystallizer, stirrer speed of the stirrer in solution, heat flux to the crystallizing solution and the suspension density of the crystallizing magma. X-ray diffraction patterns of the tungstic acid material produced confirmed that the material was crystalline and that it was in the tungsten monohydrate (WO3.H2O) form. The crystal size distribution of the crystallizer magma was obtained under steady state conditions and used to calculate the crystal nucleation and growth rates. The main nucleation mechanism in the crystallizing system was contact secondary nucleation and the crystal growth rates were found to be crystal size dependent. A size dependent growth rate model was proposed which was incorporated in the population balance equation. Good fits of the model to the data were obtained using this population balance equation. Analysis of the expressions derived for the nucleation and nuclei sized crystal growth rates indicated that the nucleation rate was a linear function of crystallizer magma suspension density and that there existed an inverse relationship between the nucleation rate and the crystal growth rate of the nuclei sized crystals

  1. Kinetics and Mechanistic Chemistry of Oxidation of Butacaine Sulfate by Chloramine-B in Acid Medium

    Shubha, Jayachamarajapura Pranesh; Kotabagi, Vinutha [Bosco Institute of Technology, Bangalore (India); Puttaswamy [Bangalore Univ., Bangalore (India)

    2012-11-15

    Butacaine sulfate is an ester of p-aminobenzoic acid which has been widely used as a local anaesthetic and it is a long standing agent particularly for spinal anaesthesia. For this reason, a kinetic study of oxidation of butacaine sulfate by sodium N-chlorobenzenesulfonamide (chloramine-B or CAB) has been carried out in HClO{sub 4} medium at 303 K in order to explore this redox system mechanistic chemistry. The rate shows a first-order dependence on both [CAB]{sub o}, and [substrate]{sub o}, and a fractional-order dependence on acid concentration. Decrease of dielectric constant of the medium, by adding methanol, increases the rate of the reaction. Variation of ionic strength and addition of benzenesulfonamide or NaCl have no significant effect on the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated. The stoichiometry of the reaction has been found to be 1:2 and the oxidation products have been identified by spectral analysis. The observed results have been explained by plausible mechanism and the related rate law has been deduced.

  2. Mechanistic study of secondary organic aerosol components formed from nucleophilic addition reactions of methacrylic acid epoxide

    Birdsall, A. W.; Miner, C. R.; Mael, L. E.; Elrod, M. J.

    2014-12-01

    Recently, methacrylic acid epoxide (MAE) has been proposed as a precursor to an important class of isoprene-derived compounds found in secondary organic aerosol (SOA): 2-methylglyceric acid (2-MG) and a set of oligomers, nitric acid esters, and sulfuric acid esters related to 2-MG. However, the specific chemical mechanisms by which MAE could form these compounds have not been previously studied with experimental methods. In order to determine the relevance of these processes to atmospheric aerosol, MAE and 2-MG have been synthesized and a series of bulk solution-phase experiments aimed at studying the reactivity of MAE using nuclear magnetic resonance (NMR) spectroscopy have been performed. The present results indicate that the acid-catalyzed MAE reaction is more than 600 times slower than a similar reaction of an important isoprene-derived epoxide, but is still expected to be kinetically feasible in the atmosphere on more acidic SOA. The specific mechanism by which MAE leads to oligomers was identified, and the reactions of MAE with a number of atmospherically relevant nucleophiles were also investigated. Because the nucleophilic strengths of water, sulfate, alcohols (including 2-MG), and acids (including MAE and 2-MG) in their reactions with MAE were found to be of similar magnitudes, it is expected that a diverse variety of MAE + nucleophile product species may be formed on ambient SOA. Thus, the results indicate that epoxide chain reaction oligomerization will be limited by the presence of high concentrations of non-epoxide nucleophiles (such as water); this finding is consistent with previous environmental chamber investigations of the relative humidity dependence of 2-MG-derived oligomerization processes and suggests that extensive oligomerization may not be likely on ambient SOA because of other competitive MAE reaction mechanisms.

  3. Kinetic studies on the extraction of uranium(VI) from phosphoric acid medium by bulk liquid membrane containing di-2-ethylhexyl phosphoric acid

    To go through the first stage of industrial solvent extraction process in order to recover uranium from phosphate rocks by liquid membrane techniques, as a simple model, the kinetics of facilitated transport of uranium(VI) from a dilute phosphoric acid medium into more concentrated phosphoric acid media as a receiving phase through a bulk liquid membrane containing di-2-ethylhexyl phosphoric acid as a carrier was studied. The influence of phosphoric acid concentration in the source and receiving phases, carrier concentration, type of solvent, stirring speed and temperature were investigated. The kinetic parameters (ke, ks, tmax, Jmax) were calculated for the interface reactions assuming two consecutive, irreversible first-order reactions. The activation energy values were calculated as 29.40 and 19.51 kJ mol-1 for extraction and stripping, respectively. The values of calculated activation energy indicated that both the extraction and stripping processes were controlled by mixed regime (both kinetic and diffusion). In addition, the influence of adding trioctyl-phosphine oxide into the membrane phase as a synergic agent on the transport kinetics was determined. (author)

  4. Kinetic properties of two Rhizopus exo-polygalacturonase enzymes hydrolyzing galacturonic acid oligomers using isothermal titration calorimetry

    The kinetic characteristics of two Rhizopus oryzae exo-polygalacturonases acting on galacturonic acid oligomers (GalpA) were determined using isothermal titration calorimetry (ITC). RPG15 hydrolyzing (GalpA)2 demonstrated a Km of 55 uM and kcat of 10.3 s^-1^ while RPG16 was shown to have greater af...

  5. Effects of inorganic components in acid rain on tube elongation of Camellia pollen

    Masaru, N.; Katsuhisa, F.; Sankichi, T.; Yutaka, W.

    1980-01-01

    Pollen grains of Camellia japonica were cultivated in culture plates containing individual inorganic components found in acid rain (SO/sub 4//sup 2 -/, NO/sub 3//sup -/, Cl/sup -/, H/sup +/, Pb/sup +2/, Mg/sup +2/ or Mn/sup +2/). In the case of three acids (HNO/sub 3/, HCl or H/sub 2/SO/sub 4/), a promotion of pollen tube elongation due to nitric acid or hydrogen chloride occurred in the range 0-0.5 millimole/litre and a marked inhibition was observed when the acid concentrations were above 0.6 millimole/litre (pH<3.2). Sulphuric acid promoted tube elongation in the range 0-0.2 millimole/litre and markedly inhibited tube elongation above 0.3 millimole/litre (pH<3.2). Nitric acid promoted tube elongation more than hydrogen chloride and sulphuric acid. However, individual inhibitions due to the three acids were similar to each other. In the case of three metallic salts (Pb(NO/sub 3/)/sub 2/, Mg(NO/sub 3/)/sub 2/ or Mn(NO/sub 3/)/sub 2/), those of lead and manganese showed a slight promotion of tube elongation at low concentrations (0.005-0.015 millimole/litre). However, the salt of magnesium had no effect in this range. Interaction of various combinations of three acids (HNOHNO/sub 3/, HCl and H/sub 2/SO/sub 4/) or three ammonium salts (NH/sub 4/NO/sub 3/, NH/sub 4/Cl and (NH/sub 4/)/sub 2/SO/sub 4/) were studied. A marked inhibition of tube elongation occurred above 0.47 millimole/litre (pH<3.2) with a combination of the three acids. However, no inhibition occurred in the same concentration range with a combination of the three ammonium salts.

  6. Characterization and mapping of the multi-component release kinetics of a Traditional Chinese Medicine dosage form using a modified LC/MS/MS method and chemomic release kinetic theory

    Hai-yan Li; Xiang-yong Cui; Feng Gao; Peter York; Qun Shao; Xian-zhen Yin; Tao Guo; Zhen Guo; Jing-kai Gu; Ji-wen Zhang

    2011-01-01

    It is essential to develop effective methods for the quality control of the traditional medicine with multiple components. However, few researches on the quality control have been conducted to interpret the holistic characteristics of the traditional medicine in terms of dissolution/release. In this study, the multi-component release kinetics of Traditional Chinese Medicine (TCM) dosage forms was characterized and mapped by multivariate analysis techniques in the field of “-omics”. The Liuwei...

  7. Impact of individual acid flue gas components on mercury capture by heat-treated activated carbon

    Jian-ming ZHENG; Jin-song ZHOU; Zhong-yang LUO; Ke-fa CEN

    2012-01-01

    Elemental mercury capture on heat-treated activated carbon (TAC) was studied using a laboratory-scale fixed bed reactor.The capability of TAC to perform Hg0 capture under both N2 and baseline gas atmospheres was studied and the effects of common acid gas constituents were evaluated individually to avoid complications resulting from the coexistence of multiple components.The results suggest that surface functional groups (SFGs) on activated carbon (AC) are vital to Hg0 capture in the absence of acid gases.Meanwhile,the presence of acid gas components coupled with defective graphitic lattices on TAC plays an important role in effective Hg0 capture.The presence of HCl,NO2,and NO individually in basic gases markedly enhances Hg0 capture on TAC due to the heterogeneous oxidation of Hg0 on acidic sites created on the carbon surface and catalysis by the defective graphitic lattices on TAC.Similarly,the presence of SO2 improves Hg0 capture by about 20%.This improvement likely results from the deposition of sulfur groups on the AC surface and oxidation of the elemental mercury by SO2 due to catalysis on the carbon surface.Furthermore,O2 exhibits a synergistic effect on Hg0 oxidation and capture when acid gases are present in the flue gases.

  8. Kinetic observation of rapid electron transfer between thymine and thymidine anion radicals and caffeic acid: a pulse radiolysis study

    Rapid electron transfer from thymine or thymidine anion radicals to caffeic acid with rate constant of 1 x 109 M-1s-1 was observed by pulse radiolysis, leading to the formation of anion radicals of caffeic acid which is characterized with absorption maximum at 360nm. Caffeic acid has a higher one-electron reduction potential than the target molecule (thymine or thymidine) and acts as a electrophilic protector which prevent the target anion radical from its irreversible protonation at C6 leading to its 5-yl radical via fast electron transfer. The kinetic demonstrations have provided dynamic evidence of charge transfer protection mechanism. (author)

  9. The active component of vanadium-molybdenum catalysts for the oxidation of acrolein to acrylic acid

    The catalytic properties of the vanadium-molybdenum oxide system were investigated in the oxidation of acrolein to acrylic acid. The active component of the catalyst is the compound VMo3O11, the maximum amount of which is observed at a content of 7-15 mole% V2O4. The compound VMo3O11 is formed in the thermodecomposition of silicomolybdovanadium heteropoly acids or isopoly compounds, reduced with respect to vanadium, and contains V4+ and Mo6+. The optimum treatment for the formation of this compound is treatment in the reaction mixture at 400 degrees C

  10. Kinetic models of reaction systems for the in situ epoxidation of unsaturated fatty acid esters and triglycerides

    Janković Milovan R.

    2004-01-01

    Full Text Available Mathematical models that describe the kinetics of reaction systems for the in situ epoxidation of unsaturated fatty acid esters or triglycérides with organic peracids are reviewed in this paper. The advantages and inadequacies of each model are discussed. A mono-phase pseudo-first order kinetic model was compared with a two phase model based on the Langmuir-Hinshelwood-Hougen-Watson (LHHW postulates proposed by the authors of this paper. The comparison was performed on the experimentally determined values for the in situ epoxidation of soybean oil by peracetic acid in the presence of different quantities of ion exchange resin used as the catalyst. It was concluded that a complete model for in situ epoxidation in the presence of ion exchange resin as the catalyst was still not given for perorganic acid formation. In particular, we report here the possibilities of the creation of an "ideal" model for in situ epoxidation.

  11. Kinetics of the oxidative hydroxylation of sodium hypophosphite in the presence of copper (II chloride modified by humic (fulvo- acid

    Zhaksyntay Kairbekov

    2012-12-01

    Full Text Available It was established that in soft conditions (50-70oC, PO2 = 1 atm sodium hypophosphite effectively is oxidized by oxygen in water solutions of copper(II chloride  to give mainly a phosphorous acid. Humic (fulvo- acid was extracted from brown coal of domestic deposit Kiyakty. For determination of optimum parameters of fulvo-acid extraction the laboratory experiments were carried out using the method of experiment planning. The kinetics, the intermediate and final products, optimal conditions of new catalytic reaction of NaH2PO2 oxidation by oxygen in water solution were defined by kinetics, volumometry, redox-potentiometry and a titration.

  12. Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: Kinetic, isotherm and thermodynamic studies

    Highlights: • Cr(VI) can oxidize biological molecules and be one of the most harmful substance. • Magnetic seperation techniques are used on different applications in many fields. • Magnetic systems can be used for rapid and selective removal as a magnetic processor. • We investigate properties of both new material and other magnetic adsorbents reported in the literatures on the adsorption of Cr(VI) ions. • No researchments were reported on adsorption of Cr(VI) with magnetic vinylphenyl boronic acid microparticles. - Abstract: Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)–vinylphenyl boronic acid(VPBA)) [m-poly(EG–VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG–VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG–VPBA) microparticles were characterized by N2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG–VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin–Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG–VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic

  13. Esterification with ethanol to produce biodiesel from high acidity raw materials. Kinetic studies and analysis of secondary reactions

    Pisarello, M.L.; Dalla Costa, B.; Mendow, G.; Querini, C.A. [Instituto de Investigaciones en Catalisis y Petroquimica (INCAPE)-(FIQ-UNL, CONICET), Santiago del Estero 2654-Santa Fe, S3000AOJ (Argentina)

    2010-09-15

    In this work, the esterification reaction of free fatty acids (FFA) in sunflower oil, coconut oil and concentrated FFA, with ethanol, methanol and ethanol 96%, using homogeneous acid catalysts to produce biodiesel is studied. Kinetic parameters are estimated with a simplified model, and then used to predict the reaction behavior. Reactions other than the reversible esterification are considered to explain the behavior that this system displays. Such reactions are the triglycerides conversion by acid catalyzed transesterification and hydrolysis. In addition, we include kinetic studies of the reaction that occur between the sulphuric acid and methanol (or ethanol), forming mono and dialkylsulphates. This reaction produces water and consumes methanol (or ethanol), and consequently has a direct impact in the esterification reaction rate and equilibrium conversion. The concentration of sulphuric acid decreases to less than 50% of the initial value due to the reaction with the alcohol. A minimum in the acidity due to the free fatty acids as a function of time was clearly observed during the reaction, which has not been reported earlier. This behavior is related to the consecutive reactions that take place during the esterification of FFA in the presence of triglycerides. The phase separation due to the presence of water, which is generated during the reaction, is also studied. (author)

  14. Uranium from phosphoric acid: kinetics studies of the solvent extraction processes for separation based on statistical data analysis

    Uranium is recovered from wet process phosphoric acid, an important secondary source, by solvent extraction technique. Kinetics of the mass transfer processes involved in extraction, scrubbing and stripping, solvent recovery operations are important for process equipment design. In this investigation we have reported results on the kinetics of separation of entrained solvent by diluent washing. The effect of stirring speed, O/A ratio and temperature has been studied. Experiments at elevated temperature (45 deg C) were carried out by preheating the WPA and Petrofin and then mixing the required volume before stirring for different time periods. (author)

  15. Biosorption of the metal-complex dye Acid Black 172 by live and heat-treated biomass of Pseudomonas sp. strain DY1: Kinetics and sorption mechanisms

    Du, Lin-Na; Wang, Bing [College of Life Science, Zhejiang University, 310058, Hangzhou, Zhejiang Province (China); Li, Gang [Department of Agriculture and Biotechnology, Wenzhou Vocational College of Science and Technology, 325006 Wenzhou, Zhejiang Province (China); Wang, Sheng [College of Life Science, Zhejiang University, 310058, Hangzhou, Zhejiang Province (China); Crowley, David E., E-mail: crowley@ucr.edu [Department of Environmental Science, University of California, Riverside, CA 92521 (United States); Zhao, Yu-Hua, E-mail: yhzhao225@zju.edu.cn [College of Life Science, Zhejiang University, 310058, Hangzhou, Zhejiang Province (China)

    2012-02-29

    Highlights: Black-Right-Pointing-Pointer The maximum amount of Acid Black 172 sorption was about 2.98 mmol/g biomass. Black-Right-Pointing-Pointer Amine groups played a major role in the biosorption of Acid Black 172. Black-Right-Pointing-Pointer The reasons of increased dye sorption by heat-treated biomass were proposed. - Abstract: The ability of Pseudomonas sp. strain DY1 to adsorb Acid Black 172 was studied to determine the kinetics and mechanisms involved in biosorption of the dye. Kinetic data for adsorption fit a pseudo-second-order model. Increased initial dye concentration could significantly enhance the amount of dye adsorbed by heat-treated biomass in which the maximum amount of dye adsorbed was as high as 2.98 mmol/g biomass, whereas it had no significant influence on dye sorption by live biomass. As treated temperature increased, the biomass showed gradual increase of dye sorption ability. Experiments using potentiometric titration and Fourier transform infrared spectroscopy (FTIR) indicated that amine groups (NH{sub 2}) played a prominent role in biosorption of Acid Black 172. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) analysis indicated that heat treatment of the biomass increased the permeability of the cell walls and denatured the intracellular proteins. The results of biosorption experiments by different cell components confirmed that intracellular proteins contributed to the increased biosorption of Acid Black 172 by heat-treated biomass. The data suggest that biomass produced by this strain may have application for removal of metal-complex dyes from wastewater streams generated from the dye products industry.

  16. Biosorption of the metal-complex dye Acid Black 172 by live and heat-treated biomass of Pseudomonas sp. strain DY1: Kinetics and sorption mechanisms

    Highlights: ► The maximum amount of Acid Black 172 sorption was about 2.98 mmol/g biomass. ► Amine groups played a major role in the biosorption of Acid Black 172. ► The reasons of increased dye sorption by heat-treated biomass were proposed. - Abstract: The ability of Pseudomonas sp. strain DY1 to adsorb Acid Black 172 was studied to determine the kinetics and mechanisms involved in biosorption of the dye. Kinetic data for adsorption fit a pseudo-second-order model. Increased initial dye concentration could significantly enhance the amount of dye adsorbed by heat-treated biomass in which the maximum amount of dye adsorbed was as high as 2.98 mmol/g biomass, whereas it had no significant influence on dye sorption by live biomass. As treated temperature increased, the biomass showed gradual increase of dye sorption ability. Experiments using potentiometric titration and Fourier transform infrared spectroscopy (FTIR) indicated that amine groups (NH2) played a prominent role in biosorption of Acid Black 172. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) analysis indicated that heat treatment of the biomass increased the permeability of the cell walls and denatured the intracellular proteins. The results of biosorption experiments by different cell components confirmed that intracellular proteins contributed to the increased biosorption of Acid Black 172 by heat-treated biomass. The data suggest that biomass produced by this strain may have application for removal of metal-complex dyes from wastewater streams generated from the dye products industry.

  17. Temperature dependence of relaxation times in proton components of fatty acids

    We examined the temperature dependence of relaxation times in proton components of fatty acids in various samples in vitro at 11 tesla as a standard calibration data for quantitative temperature imaging of fat. The spin-lattice relaxation time, T1, of both the methylene (CH2) chain and terminal methyl (CH3) was linearly related to temperature (r>0.98, P2 signal for calibration and observed the signal with 18% of CH3 to estimate temperature. These findings suggested that separating the fatty acid components would significantly improve accuracy in quantitative thermometry for fat. Use of the T1 of CH2 seems promising in terms of reliability and reproducibility in measuring temperature of fat. (author)

  18. The radiation crosslinking of poly(vinyl chloride) with trimethylolpropanetrimethacrylate. III. Effect of diundecyl phthalate: chemical kinetics of a three-component system

    The radiation chemistry of poly(vinyl chloride) (PVC) blended with trimethylolpropanetrimethacrylate (TMPTMA) and diundecyl phthalate (DUP) has been examined. This three-component mixture contains a base resin (PVC), a crosslinking sensitizer (TMPTMA), and a physical modifier (DUP). These are the basic components in any radiation-curable coating. The kinetics and mechanism of the crosslinking reactions were studied with reference to the dependence on radiation dose and blend composition. The polyfunctional TMPTMA underwent polymerization incorporating the PVC into a 3-dimensional network. DUP remained chemically inert during the irradiation, not being bound to the network. However, DUP by plasticizing the macromolecules and diluting the monomer, changed the kinetics extensively. DUP enhanced TMPTMA homopolymerization, TMPTMA grafting, and PVC crosslinking reaction rates. The effect of the competition between polymerization, grafting, and degradation reactions was examined in terms of enhanced mobility of the reacting species. The influence of these kinetics considerations in selecting a blend composition for a coating application was discussed

  19. The radiation crosslinking of poly(vinyl chloride) with trimethylolpropanetrimethacrylate. III. Effect of diundecyl phthalate: chemical kinetics of a three-component system

    Bowmer, T.N.; Vroom, W.I.; Hellman, M.Y.

    1983-08-01

    The radiation chemistry of poly(vinyl chloride) (PVC) blended with trimethylolpropanetrimethacrylate (TMPTMA) and diundecyl phthalate (DUP) has been examined. This three-component mixture contains a base resin (PVC), a crosslinking sensitizer (TMPTMA), and a physical modifier (DUP). These are the basic components in any radiation-curable coating. The kinetics and mechanism of the crosslinking reactions were studied with reference to the dependence on radiation dose and blend composition. The polyfunctional TMPTMA underwent polymerization incorporating the PVC into a 3-dimensional network. DUP remained chemically inert during the irradiation, not being bound to the network. However, DUP by plasticizing the macromolecules and diluting the monomer, changed the kinetics extensively. DUP enhanced TMPTMA homopolymerization, TMPTMA grafting, and PVC crosslinking reaction rates. The effect of the competition between polymerization, grafting, and degradation reactions was examined in terms of enhanced mobility of the reacting species. The influence of these kinetics considerations in selecting a blend composition for a coating application was discussed.

  20. Free fatty acids as a major component of the chlorosulfolipid membrane of Ochromonas danica

    Winicov, I.

    1985-01-01

    This work is an attempt to determine whether or not free fatty acids are components of the natural membrane of Ochromonas danica. If the FFAs were artifacts, they would most likely have been produced during solvent extraction or during the procedure for flagellar detachment. Attempts to denature putative solvent-activated lipase(s) through exposure to boiling isopropanol or by crosslinking the flagella with glutaraldehyde prior to extraction failed to eliminate the free fatty acid fraction, nor to significantly alter its composition. Exposure of flagella to albumin resulted in the net transfer of FFAs to the supernatant phase, showing their presence is not caused by solvent activated lipolysis. Finally levels of labelled free fatty acids failed to rise as a function of time after deflagellation in cells grown in the presence of (10-/sup 14/C)-oleic acid. Acid hydrolysis of the total labelled lipid at elevated temperature increased the percentage of counts occurring as unesterified fatty acids (from 2.6% to 64.8%). This, taken together with a corresponding loss of the more polar labelled material (66.8% to 8.2%) indicates that some esterified lipids were present, but probably not broken down during the isolation procedure.

  1. Free fatty acids as a major component of the chlorosulfolipid membrane of Ochromonas danica

    This work is an attempt to determine whether or not free fatty acids are components of the natural membrane of Ochromonas danica. If the FFAs were artifacts, they would most likely have been produced during solvent extraction or during the procedure for flagellar detachment. Attempts to denature putative solvent-activated lipase(s) through exposure to boiling isopropanol or by crosslinking the flagella with glutaraldehyde prior to extraction failed to eliminate the free fatty acid fraction, nor to significantly alter its composition. Exposure of flagella to albumin resulted in the net transfer of FFAs to the supernatant phase, showing their presence is not caused by solvent activated lipolysis. Finally levels of labelled free fatty acids failed to rise as a function of time after deflagellation in cells grown in the presence of [10-14C]-oleic acid. Acid hydrolysis of the total labelled lipid at elevated temperature increased the percentage of counts occurring as unesterified fatty acids (from 2.6% to 64.8%). This, taken together with a corresponding loss of the more polar labelled material (66.8% to 8.2%) indicates that some esterified lipids were present, but probably not broken down during the isolation procedure

  2. Soil Components Affecting Phosphate Sorption Parameters of Acid Paddy Soils in Guangdong Province

    2000-01-01

    Soil components affecting phosphate sorption parameters were studied using acid paddy soils derived from basalt, granite, sand-shale and the Pearl River Delta sediments, respectively, in Guangdong Province.For each soil, seven 2.50 g subsamples were equilibrated with 50 mL 0.02 mol L-1 (pH=7.0) of KCl containing 0, 5, 10, 15, 25, 50 and 100 ng P kg-1, respectively, in order to derive P sorption parameters (P sorption maximum, P sorption intensity factor and maximum buffer capacity) by Langmuir isotherm equation. It was shown that the main soil components influencing phosphate sorption maximum (Xm) included soil clay, pH,amorphous iron oxide (Feo) and amorphous aluminum oxide (Alo), with their effects in the order of Alo >Feo > pH > clay. Among these components, pH had a negative effect, and the others had a positive effect.Organic matter (OM) was the only soil component influencing P sorption intensity factor (K). The main components influencing maximum phosphate buffer capacity (MBC) consisted of soil clay, OM, pH, Feo and Alo, with their effects in the order of Alo > OM > pH > Feo > clay. Path analysis indicated that among the components with positive effects on maximum phosphate buffer capacity (MBC), the effect was in the order of Alo > Feo > Clay, while among the components with negative effects, OM > pH. OM played an important role in mobilizing phosphate in acid paddy soils mainly through decreasing the sorption intensity of phosphate by soil particles.

  3. Sorption of a branched nonylphenol and perfluorooctanoic acid on Yangtze River sediments and their model components

    Li, C L; R. Ji; Schaffer, A.; Sequaris, J.M.; Amelung, W.; H. Vereecken; E. Klumpp

    2012-01-01

    Many metabolites of organic surfactants such as nonylphenol (NP) and perfluorooctanoic acid (PFOA) are ubiquitously found in the environment and are toxic if not sorbed on soils and sediments. In this study, we quantified the sorption of the NP isomer with the highest endocrine activity, [4-(1-ethyl-1,3-dimethylpentyl) phenol] (NP111), and that of PFOA on Yangtze River sediments and its model components illite, goethite and natural organic matter. The sorption experiments were performed with ...

  4. Model Compounds for Heavy Crude Oil Components and Tetrameric Acids: Characterization and Interfacial Behaviour

    Nordgård, Erland Løken

    2009-01-01

    The tendency during the past decades in the quality of oil reserves shows that conventional crude oil is gradually being depleted and the demand being replaced by heavy crude oils. These oils contain more of a class high-molecular weight components termed asphaltenes. This class is mainly responsible for stable water-in-crude oil emulsions. Both heavy and lighter crude oils in addition contain substantial amounts of naphthenic acids creating naphthenate deposits in topside facilities.The asph...

  5. Optimization of medium components using orthogonal arrays for Linolenic acid production by Spirulina platensis

    This work describes the medium optimization of '-Linolenic acid (GLA) production by Spirulina platensis using one-factor and orthogonal array design methods. In the one-factor experiments, NaHCO3 (9 mg L-1), NaNO3 (13.5 mg L-1) and MgSO4•7H2O (11.85 mg L-1) proved to be the best components for GLA p...

  6. The kinetics of process dependent ammonia inhibition of methanogenesis from acetic acid.

    Wilson, Christopher Allen; Novak, John; Takacs, Imre; Wett, Bernhard; Murthy, Sudhir

    2012-12-01

    Advanced anaerobic digestion processes aimed at improving the methanization of sewage sludge may be potentially impaired by the production of inhibitory compounds (e.g. free ammonia). The result of methanogenic inhibition is relatively high effluent concentrations of acetic acid and other soluble organics, as well as reduced methane yields. An extreme example of such an advanced process is the thermal hydrolytic pretreatment of sludge prior to high solids digestion (THD). Compared to a conventional mesophilic anaerobic digestion process (MAD), THD operates in a state of constant inhibition driven by high free ammonia concentrations, and elevated pH values. As such, previous investigations of the kinetics of methanogenesis from acetic acid under uninhibited conditions do not necessarily apply well to the modeling of extreme processes such as THD. By conducting batch ammonia toxicity assays using biomass from THD and MAD reactors, we compared the response of these communities over a broad range of ammonia inhibition. For both processes, increased inhibitor concentrations resulted in a reduction of biomass growth rate (r(max) = μ(max)∙X) and a resulting decrease in the substrate half saturation coefficient (K(S)). These two parameters exhibited a high degree of correlation, suggesting that for a constant transport limited system, the K(S) was mostly a linear function of the growth rate. After correcting for reactor pH and temperature, we found that the THD and MAD biomass were both able to perform methanogenesis from acetate at high free ammonia concentrations (equivalent to 3-5 g/L total ammonia nitrogen), albeit at less than 30% of their respective maximum rates. The reduction in methane production was slightly less pronounced for the THD biomass than for MAD, suggesting that the long term exposure to ammonia had selected for a methanogenic pathway less dependent on those organisms most sensitive to ammonia inhibition (i.e. aceticlastic methanogens). PMID

  7. [Photocatalytic degradation kinetics of perfluorooctanoic acid (PFOA) in TiO2 dispersion and its mechanism].

    Li, Ming-Jie; Yu, Ze-Bin; Chen, Ying; Wang, Li; Liu, Qing; Liu, Yu-Xin; He, Li-Li

    2014-07-01

    Decomposition of perfluorooctanoic acid (PFOA) is of prime importance since it is recognized as a persistent organic pollutant and is widespread in the environment. Heterogeneous photocatalytic decomposition of PFOA by TiO2 (P25) was investigated under 254 nm UV light. Experimental conditions including initial pH, TiO2 content and PFOA concentration, were varied to demonstrate their effects on the decomposition of PFOA. It was observed that the photocatalytic degradation kinetics of PFOA could be fitted to the quasi-first-order equation. The pH played a determinant role in the decomposition of PFOA and the presence of O2 increased the degradation rate. Optimal conditions for a complete removal were obtained using 1.5 g x L(-1) TiO2 at pH 3 in air atmosphere, with a rate constant of 0.420 6 h(-1). The contribution experiments of various reactive species produced during the photocatalysis were also investigated with the addition of different scavengers and it was found that photogenerated holes (h+) was the major reactive species which was responsible for 66.1% of the degradation rate, and the *OH was involved in PFOA degradation as well. In addition, the photocatalytic experiment with the addition of NaF indicated that the adsorption of PFOA was of primary importance for the photocatalytic decomposition. Perfluorocarboxylic acids (PFCAs) with shorter carbon chain length as intermediates and products were identified with UPLC-QTOF/MS, and a possible mechanism for PFOA decomposition was proposed. PMID:25244845

  8. Lactic acid bacteria in dairy food: surface characterization and interactions with food matrix components.

    Burgain, J; Scher, J; Francius, G; Borges, F; Corgneau, M; Revol-Junelles, A M; Cailliez-Grimal, C; Gaiani, C

    2014-11-01

    This review gives an overview of the importance of interactions occurring in dairy matrices between Lactic Acid Bacteria and milk components. Dairy products are important sources of biological active compounds of particular relevance to human health. These compounds include immunoglobulins, whey proteins and peptides, polar lipids, and lactic acid bacteria including probiotics. A better understanding of interactions between bioactive components and their delivery matrix may successfully improve their transport to their target site of action. Pioneering research on probiotic lactic acid bacteria has mainly focused on their host effects. However, very little is known about their interaction with dairy ingredients. Such knowledge could contribute to designing new and more efficient dairy food, and to better understand relationships between milk constituents. The purpose of this review is first to provide an overview of the current knowledge about the biomolecules produced on bacterial surface and the composition of the dairy matter. In order to understand how bacteria interact with dairy molecules, adhesion mechanisms are subsequently reviewed with a special focus on the environmental conditions affecting bacterial adhesion. Methods dedicated to investigate the bacterial surface and to decipher interactions between bacteria and abiotic dairy components are also detailed. Finally, relevant industrial implications of these interactions are presented and discussed. PMID:25277266

  9. The viability of a nonenzymatic reductive citric acid cycle--kinetics and thermochemistry.

    Ross, David S

    2007-02-01

    The likelihood of a functioning nonenzymatic reductive citric acid cycle, recently proposed as the precursor to biosynthesis on early Earth, is examined on the basis of the kinetics and thermochemistry of the acetate --> pyruvate --> oxaloacetate --> malate sequence. Using data derived from studies of the Pd-catalyzed phosphinate reduction of carbonyl functions it is shown that the rate of conversion of pyruvate to malate with that system would have been much too slow to have played a role in the early chemistry of life, while naturally occurring reduction systems such as the fayalite-magnetite-quartz and pyrrhotite-pyrite-magnetite mineral assemblages would have provided even slower conversions. It is also shown that the production of pyruvate from acetate is too highly endoergic to be driven by a naturally occurring energy source such as pyrophosphate. It is thus highly doubtful that the cycle can operate at suitable rates without enzymes, and most unlikely that it could have participated in the chemistry leading to life. PMID:17136437

  10. Combined Kinetic Studies and Computational Analysis on Kojic Acid Analogs as Tyrosinase Inhibitors

    Carlyle Ribeiro Lima

    2014-07-01

    Full Text Available Tyrosinase is a key enzyme in melanin synthesis and widely distributed in plants and animals tissues. In mammals, this enzyme is related to pigment production, involved in wound healing, primary immune response and it can also contribute to catecholamines synthesis in the brain. Consequently, tyrosinase enzyme represents an attractive and selective target in the field of the medicine, cosmetics and bio-insecticides. In this paper, experimental kinetics and computational analysis were used to study the inhibition of tyrosinase by analogous of Kojic acid. The main interactions occurring between inhibitors-tyrosinase complexes and the influence of divalent cation (Cu2+ in enzymatic inhibition were investigated by using molecular docking, molecular dynamic simulations and electrostatic binding free energy by using the Linear Interaction Energy (LIE method. The results showed that the electrostatic binding free energy are correlated with values of constant inhibition (r2 = 0.97.Thus, the model obtained here could contribute to future studies of this important system and, therefore, eventually facilitate development of tyrosinase inhibitors.