KINETIC FORMULATION OF THE DENITRIFICATION PROCESS IN SOIL

1979 ◽  
Vol 59 (3) ◽  
pp. 249-257 ◽  
Author(s):  
C. M. CHO ◽  
J. G. MILLS
Keyword(s):  
Enzyme Kinetics ◽  
Maximum Concentration ◽  
Initial Rate ◽  
Zero Order ◽  
Gas Mixture ◽  
Disappearance Rate ◽  
High Accumulation ◽  
Kinetic Formulation ◽  
Initial Concentration ◽  
Denitrification Process

Kinetic formulation of denitrification process in soil was developed based on a model of competitive Michaelis-Menten type enzyme kinetics. Several values of parameters were chosen to plot the concentrations of NO−3, NO−2, N2O-N and N2-N at various times of incubation under different initial concentrations of NO−3. According to the model the disappearance rate of NO−3 was found to be independent of initial concentration of NO−3 and was nearly constant, similar to zero order rate of disappearance. The initial rate of NO−2 formation was independent of the NO−3 concentration. However, the maximum concentration of NO−2 and the time at which the maximum was found were found to be dependent upon the NO−3 concentration. When there was very little accumulation of NO−2 in the system, the initial rate of N2O formation was found to be independent of NO−3 concentration. However, if there was high accumulation of NO−2, the initial rate of N2O formation became inversely related to NO−3 concentration. The initiation of N2 formation was generally slower as the concentration of NO−3 increased. The composition of gas mixture, N2O and N2, was found to vary depending upon the initial NO−3 concentration and with the time of incubation. The formulation presented herein describes the features of denitrification experimentally observed fairly well.

Effects of pH, Temperature and Various Anions on Thiourea Disappearance in Aqueous Media with Titanium Dioxide Under UV-Irradiation. Photomineralization Kinetics

2001 ◽  
Vol 66 (4) ◽  
pp. 676-684 ◽  
Author(s):  
Abdelghani Boussaoud ◽  
Gerard Duc ◽  
Jean Pierre Meille ◽  
Michelle Petit-Ramel
Keyword(s):  
Titanium Dioxide ◽  
Uv Irradiation ◽  
Initial Rate ◽  
Aqueous Media ◽  
Inorganic Anions ◽  
Disappearance Rate ◽  
Initial Concentration ◽  
Effects Of Ph ◽  
Nitrite Nitrate ◽  
Kinetics Of

Disappearance of thiourea in aqueous suspensions of TiO2 or ZnO occurs under near-UV irradiation. The effects of some parameters such as initial concentration of thiourea, temperature, pH and common inorganic anions were examined. The results indicate that the process follows the Langmuir-Hinshelwood type kinetics. In the presence of anions such as nitrates, chlorides and sulfates, the initial disappearance rate of thiourea at pH 6 drops. It is found that the initial rate of thiourea disappearance increases when temperatue of reaction mixture increases. Finally, kinetics of thiourea photomineralization to nitrite, nitrate, sulfite and sulfate are established.

Vulcanization of Elastomers. 26. Vulcanization of Natural and Synthetic Rubbers by Sulfur in the Presence of Organic Bases

1960 ◽  
Vol 33 (3) ◽  
pp. 834-845
Author(s):  
Walter Scheele ◽  
Wolfgang Redetzky
Keyword(s):  
Initial Rate ◽  
Reaction Order ◽  
Research Work ◽  
Intermediate Compound ◽  
Sulfur Concentration ◽  
Kcal Mole ◽  
Initial Concentration ◽  
Organic Bases ◽  
Single Power ◽  
Theory And Experiment

Abstract In connection with earlier research work, we have carefully studied the decrease of sulfur during the vulcanization of Perbunan N 2818 in the presence of DPG, at various temperatures and with varied molar concentrations of sulfur and accelerator. We found : 1. The sulfur concentration decreases at all temperatures according to a time law of order 0.8. An activation energy of about 28 kcal/mole is derived from the temperature dependence of the rate constant. 2. The reaction order is independent of the initial concentration of reactants. 3. A discrepancy is found in the order of the reaction with respect to time and with respect to concentration, and it is clearly shown that the dependence of the initial rate on the initial concentration can not be expressed by a single power law. 4. The attempt is made to explain the discrepancy by postulating catalysis by an intermediate compound. The consequences from this consideration are compared with the experimental results, and, on the whole, agreement is found between theory and experiment.

Initial Rate Enzyme Kinetics

1977 ◽  
Vol 5 (1) ◽  
pp. 332-332
Author(s):  
PAUL C. ENGEL
Keyword(s):  
Enzyme Kinetics ◽  
Initial Rate

The Reaction of Ozone with SBR Rubbers

1959 ◽  
Vol 32 (4) ◽  
pp. 1062-1079 ◽  
Author(s):  
E. R. Erickson ◽  
R. A. Berntsen ◽  
E. L. Hill ◽  
Paul Kusy
Keyword(s):  
Initial Rate ◽  
Protective Action ◽  
Rate Data ◽  
High Solubility ◽  
Initial Concentration ◽  
Degree Of Protection ◽  
Effective Barrier ◽  
Gaseous Ozone ◽  
Low Concentrations ◽  
Oxidized Products

Abstract All SBR vulcanizates, when tested in a relaxed state, reacted with ozone of low concentrations to form a film of oxidized products which provided an effective barrier against further attack by gaseous ozone. SBR vulcanizates that were under stress, but which contained no effective antiozonant in their formulation, were readily attacked by ozone. The absorption of ozone appeared to begin with an initial rate of zero which was followed by rapidly increasing rates until a maximum had been reached, when ozone cracks were visible on the surface of the rubber. SBR vulcanizates that were under stress, but which contained an antiozonant, were protected from an attack by ozone to a degree that ranged from poor to excellent. The degree of protection depended (a) on the differential in the rates of reaction of the antiozonant and the rubber hydrocarbon with ozone, (b) on the initial concentration of the antiozonant on the surface of the vulcanizate which reacted with ozone to form a barrier of oxidized residues, and (c) on the rate of effusion of fresh antiozonant from within the rubber to the outer surface of the barrier. SBR vulcanizates containing a naphthenic processing oil as an extender were not so resistant to ozone as standard SBR vulcanizates. It is probable that the effectiveness of the antiozonants tested in these vulcanizates was reduced by their high solubility in the oil phase. SBR vulcanizates containing trioctyl phosphate as a plasticizer were vigorously attacked by ozone. It is possible that the gaseous ozone dissolved to some extent into the plasticizer phase, increasing the concentration of ozone in the area causing a more severe oxidation of the rubber. SBR vulcanizates that had been coated with an antiozonant by dipping the specimen several times into a solution of the antiozonant in a solvent were found to contain a higher concentration of the antioxonant directly on the surface of the vulcanizate than in the case where three parts of the antiozonant were added during vulcanization. A mechanism for the ozonization of SBR vulcanizates has been proposed which includes a possible mechanism for the protective action of antiozonants. A rate equation has been derived from this mechanism which was consistent with the experimental rate data.

Heterogeneous reaction of nitric acid with methyl sulfide

1985 ◽  
Vol 63 (10) ◽  
pp. 2805-2807
Author(s):  
Donald L. Singleton ◽  
Robert S. Irwin ◽  
Donald J. McKenney ◽  
George Paraskevopoulos
Keyword(s):  
Gas Chromatography ◽  
Infrared Spectroscopy ◽  
Nitric Acid ◽  
Initial Rate ◽  
Heterogeneous Reaction ◽  
Zero Order ◽  
Homogeneous Reaction ◽  
Gaseous Mixtures ◽  
First Order ◽  
Upper Limit

The reaction of gaseous mixtures of CH3SCH3 and HNO3, studied by infrared spectroscopy and gas chromatography, was found to occur heterogeneously. The products detected were NO2 and CH3S(O)CH3, and approximately one NO2 was formed for each CH3SCH3 consumed. The initial rate of formation of NO2 was first order in CH3SCH3 and zero order in HNO3. The mechanism is discussed, and an upper limit is determined for the rate constant of the homogeneous reaction.

Photodegradation of Phenol on Halogen-Doping TiO2 Nanoparticles Composites in Seawater

2011 ◽  
Vol 694 ◽  
pp. 355-359 ◽  
Author(s):  
Pei Chang Deng ◽  
Jie Zhen Hu ◽  
Hai Zeng Wang
Keyword(s):  
Photocatalytic Degradation ◽  
Chemical Reaction ◽  
Phenol Degradation ◽  
Order Reaction ◽  
Zero Order ◽  
Hydrothermal Route ◽  
Initial Concentration ◽  
Zero Order Reaction ◽  
Halogen Doping

Halogen-doping TiO2 (X/TiO2) have been prepared through a mild hydrothermal route. Using X/TiO2 as the photocatalyst, photodegradation of phenol was observed both in freshwater and seawater. The degradation velocity of phenol in seawater is smaller than it in freshwater. The phenol degradation is influenced by the photocatalyst dosage and pH of seawater. The chemical reaction of the photocatalytic degradation phenol is the zero order reaction. The influence of phenol initial concentration on its degradation velocity is small.

scholarly journals Flow-Based Systems for Rapid and High-Precision Enzyme Kinetics Studies

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Supaporn Kradtap Hartwell ◽  
Kate Grudpan
Keyword(s):  
Enzyme Kinetics ◽  
High Precision ◽  
Initial Rate ◽  
Enzymatic Reaction ◽  
High Volume ◽  
Manual Operation ◽  
Kinetics Studies ◽  
Time Control ◽  
The Many ◽  
Potential Use

Enzyme kinetics studies normally focus on the initial rate of enzymatic reaction. However, the manual operation of steps of the conventional enzyme kinetics method has some drawbacks. Errors can result from the imprecise time control and time necessary for manual changing the reaction cuvettes into and out of the detector. By using the automatic flow-based analytical systems, enzyme kinetics studies can be carried out at real-time initial rate avoiding the potential errors inherent in manual operation. Flow-based systems have been developed to provide rapid, low-volume, and high-precision analyses that effectively replace the many tedious and high volume requirements of conventional wet chemistry analyses. This article presents various arrangements of flow-based techniques and their potential use in future enzyme kinetics applications.

Initial rate enzyme kinetics

1976 ◽  
Vol 1 (7) ◽  
pp. 166
Author(s):  
Keith Tipton
Keyword(s):  
Enzyme Kinetics ◽  
Initial Rate
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