scholarly journals Kinetics of K release from soils of Brazilian coffee regions: effect of organic acids

2008 ◽  
Vol 32 (2) ◽  
pp. 533-540 ◽  
Author(s):  
Vladimir Antônio Silva ◽  
Giuliano Marchi ◽  
Luiz Roberto Guimarães Guilherme ◽  
José Maria de Lima ◽  
Francisco Dias Nogueira ◽  
...  
Keyword(s):  
Release Kinetics ◽  
Kinetic Studies ◽  
Release Rates ◽  
First Order ◽  
Potassium Release ◽  
Minas Gerais State ◽  
Soil Clay ◽  
Extractant Solution ◽  
Kinetics Of ◽  
K Release

Kinetic studies on soil potassium release can contribute to a better understanding of K availability to plants. This study was conducted to evaluate K release rates from the whole soil, clay, silt, and sand fractions of B-horizon samples of a basalt-derived Oxisol and a sienite-derived Ultisol, both representative soils from coffee regions of Minas Gerais State, Brazil. Potassium was extracted from each fraction after eight different shaking time periods (0-665 h) with either 0.001 mol L-1 citrate or oxalate at a 1:10 solid:solution ratio. First-order, Elovich, zero-order, and parabolic diffusion equations were used to parameterize the time dependence of K release. For the Oxisol, the first-order equation fitted best to the experimental data of K release, with similar rates for all fractions and independent of the presence of citrate or oxalate in the extractant solution. For all studied Ultisol fractions, in which K release rates increased when extractions were performed with citrate solution, the Elovich model described K release kinetics most adequately. The highest potassium release rate of the Ultisol silt fraction was probably due to the transference of "non-exchangeable" K to the extractant solution, whereas in the Oxisol exchangeable potassium represented the main K source in all studied fractions.

Models for potassium release kinetics of four Humic Gleysols high in clay by electro-ultrafiltration

2001 ◽  
Vol 81 (5) ◽  
pp. 603-611 ◽  
Author(s):  
N. Ziadi ◽  
R. R. Simard ◽  
T. S. Tran
Keyword(s):  
Solid Phase ◽  
Release Kinetics ◽  
Order Equation ◽  
K Uptake ◽  
First Order ◽  
Incremental Model ◽  
Release Data ◽  
First Time ◽  
Kinetics Of ◽  
K Release

The rate of K release from the soil solid phase to its solution, especially from its rapidly and slowly exchangeable forms, can affect plant K uptake. The electro-ultrafiltration (EUF) technique was used to kinetically characterize the K release from four soils (Humic Gleysols) from Abitibi-Temiscaming, Quebec, Canada. Potassium was desorbed from soils that received over 166 kg K ha-1 yr-1 from 1994 to 1996. The desorption was carried out for 58 min (4, 4, and every 5 min thereafter for a total of 12 desorptions) at 400 V and 80°C. The amount of K desorbed was between 199 and 342 mg kg-1. Cumulative K desorption was described by the following six equations: power function, simplified Elovich, extended Elovich, parabolic diffusion, zero-order, and first-order. An incremental first-order equation was also tested. The studied soils have large K supplying capacities as suggested by forage K-uptake and total soil K desorption by EUF. In general, all tested equations adequately described the K release by EUF from the four soils. The incremental first-order equation, used for the first time, described well the soil K release data. The k rate constant from this model was significantly related to forage K uptake (R2 = 0.58). Results from this study indicate that the investigated soils have large K reserves and that the incremental first-order equation and most of the cumulative ones are suitable for describing the kinetics of the large K release from these fine-textured Gleysols. Key Words: Potassium, desorption, cumulative model, incremental model

Analysis of K+ release kinetics of biomass ash with different pH

2014 ◽  
Vol 22 (2) ◽  
pp. 171-176
Author(s):  
Kan WANG ◽  
Zifang WANG ◽  
Ming GAO ◽  
Yaohua HUANG ◽  
Xiaofei HAN ◽  
...  
Keyword(s):  
Release Kinetics ◽  
Biomass Ash ◽  
Kinetics Of ◽  
K Release

Kinetics of the Ozonation of Tetrabromobisphenol-A in Wastewater

2011 ◽  
Vol 383-390 ◽  
pp. 2945-2950 ◽  
Author(s):  
Jie Zhang ◽  
Shi Long He ◽  
Mei Feng Hou ◽  
Li Ping Wang ◽  
Li Jiang Tian
Keyword(s):  
Rate Constants ◽  
Apparent Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Kinetic Studies ◽  
Tetrabromobisphenol A ◽  
First Order ◽  
Reaction Rate Constants ◽  
Pseudo First Order ◽  
Kinetics Of

The kinetics of TBBPA degradation by ozonation in semi-batch reactor was studied. The reaction rate constants of TBBPA with O3 and •OH were measured by means of direct ozone attack and competition kinetics, and the values of which were 6.10 l/(mol•s), 4.8×109 l/(mol•s), respectively. Results of kinetic studies showed that TBBPA degradation by ozonation under the different conditions tested followed the pseudo-first-order. The values of apparent rate constant of TBBPA degradation increased with the increase of ozone dosage and pH, but decreased with the increase of initial TBBPA concentration.

KINETIC STUDIES OF METHYL-BIS-β-CHLOROETHYLAMINE: III. THE KINETICS OF THE DIMERIZATION IN METHANOL

1948 ◽  
Vol 26b (2) ◽  
pp. 175-180 ◽  
Author(s):  
C. A. Winkler ◽  
A. W. Hay ◽  
A. L. Thompson
Keyword(s):  
Rate Constants ◽  
Initial Rate ◽  
Kinetic Studies ◽  
First Order ◽  
Rate Expression ◽  
Principal Reaction ◽  
Kinetics Of ◽  
Rate Controlling Step

The principal reaction of methyl-bis-β-chloroethylamine in methanol is dimerization, which results in one chlorine from each molecule becoming ionic, but this is accompanied by slight alcoholysis. The rate-controlling step is believed to be the first order formation of an ethylenimonium ion which reacts rapidly with one of its kind to form dimer. The rate expression as calculated from initial rate constants is k (initial) = 4.0 × 1013e−19600/RThr.−1.

scholarly journals   Copper release kinetics: Effect of two extractants and wheat (Triticum aestivum L.) rhizosphere

2012 ◽  
Vol 58 (No. 10) ◽  
pp. 471-476 ◽  
Author(s):  
H.R. Motaghian ◽  
A.R. Hosseinpur
Keyword(s):  
Citric Acid ◽  
Release Kinetics ◽  
Calcareous Soils ◽  
Triticum Aestivum L ◽  
First Order ◽  
Rhizosphere Soils ◽  
Copper Release ◽  
Successive Extraction ◽  
The Mean ◽  
Kinetics Of

The greenhouse experiment was performed to determine Cu release characteristics in the bulk and the rhizosphere of some calcareous soils using rhizobox. The kinetics of Cu release in the bulk and the rhizosphere soils were determined by successive extraction with diethylenetriaminepentaacetic acid-triethanolamine (DTPA-TEA) and 10 mmol/L citric acid in a period of 1 to 504 h at 25 ± 1°C. The results of kinetics study showed that Cu extracted using DTPA-TEA in the rhizosphere soils was significantly (P < 0.01) lower than the bulk soils, while Cu extracted using citric acid in the rhizosphere soils was significantly (P < 0.01) higher than the bulk soils. The mean of released Cu after 504 h using DTPA-TEA were 8.59 and 7.46 mg/kg in the bulk and the rhizosphere soils, respectively. The mean release of Cu after 504 h using citric acid was 14.73 and 16.05 mg/kg in the bulk and the rhizosphere soils, respectively. Release kinetics of Cu in two extractants conformed fairly well to parabolic diffusion, power function, and first order equations. The results of correlation analysis illustrated that a significant correlation between Cu desorption after 504 h with citric acid and Cu concentration in wheat was found (r = 0.96 and r = 0.90 in the rhizosphere and the bulk soils, respectively, P < 0.01). Therefore, application of 10 mmol/L citric acid extractant would be recommended in the future study on the kinetics of release of Cu in calcareous soils.  

scholarly journals Reactivity and kinetic studies of benzofuran hydrodeoxygenation over a Ni2P-O/MCM-41 catalyst

2019 ◽  
Vol 44 (4) ◽  
pp. 307-315 ◽  
Author(s):  
Xueya Dai ◽  
Hua Song ◽  
Hualin Song ◽  
Jing Gong ◽  
Feng Li ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Time Analysis ◽  
Liquid Ratio ◽  
Order Model ◽  
Free Products ◽  
First Order ◽  
Reaction Rate Constants ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Mcm 41

A nickel phosphide hydrodeoxygenation catalyst (Ni2P-O/MCM-41) was prepared using a new synthetic method. The as-prepared catalyst was evaluated in the hydrodeoxygenation of benzofuran, and the effects of reaction temperature, pressure, and the H2/liquid ratio were investigated. A pseudo first-order model was employed to describe the reaction kinetics of benzofuran hydrodeoxygenation over the Ni2P-O/MCM-41 catalyst. The reaction rate constants ( k1– k5) at different temperatures were determined according to this model. At 533 K, the conversion of 2-ethylphenol in to ethylbenzene began to increase dramatically, and the yield of O-free product, ethylcyclohexane, started to increase rapidly. At 573 K, 3.0 MPa, and a H2/liquid ratio of 500 (V/V), the conversion of benzofuran over Ni2P-O/MCM-41 reached 93%, and the combined yield of O-free products was 91%. Contact time analysis indicated that demethylation was not favored over the Ni2P-O/MCM-41 catalyst.

scholarly journals   Potassium release kinetics and its correlation with pinto bean (Phaseolus vulgaris) plant indices

2012 ◽  
Vol 58 (No. 7) ◽  
pp. 328-333 ◽  
Author(s):  
A.R. Hosseinpur ◽  
H.R. Motaghian ◽  
M.H. Salehi
Keyword(s):  
Release Kinetics ◽  
Calcareous Soils ◽  
Bean Plant ◽  
Pinto Bean ◽  
Successive Extraction ◽  
Release Studies ◽  
Function Models ◽  
Kinetics Of ◽  
Total Reaction Time ◽  
K Release

The rate of potassium (K) release from soils is a dynamic process, and it is important to the evaluation of soil K availability to plant. The objectives of this study were to determine K release characteristics and the correlation of these parameters with bean plant indices in surface soils of 15 calcareous soils. The kinetics of K release was determined by successive extraction with 0.01 mol/L CaCl<sub>2</sub> in a period of 2&ndash;2017 h at 25 &plusmn; 1&deg;C. The results showed that the cumulative K&rlm; release ranged from 111 to 411 mg/kg. A plot of cumulative amount of K released showed a discontinuity in slope at 168 h. Thus, two equations were applied to segments of the total reaction time (2 to 168 and 168 to 2017 h). The amounts of K released during 2&ndash;168 and 168&ndash;2017 h ranged from 55 to 299 and 44 to 119 mg/kg, respectively. Release kinetics of K conformed fairly well to parabolic diffusion, simplified Elovich and power function models in two segments. Potassium released after 2&ndash;168 and 168&ndash;2017 h and K release rate constants were significantly correlated (P &lt; 0.05) with bean plant indices, while correlation between K extracted by using 1 mol/L NH<sub>4</sub>OAc (ammonium acetate) and plant indices was not significant. The results of this research showed that information obtained from K release studies in laboratory and kinetics equation parameters can help to estimate the K supplying power of soils. &nbsp;

KINETIC STUDIES ON THE HYDROLYSIS OF BENZOYLCHOLINE BY HUMAN SERUM CHOLINESTERASE

1956 ◽  
Vol 34 (1) ◽  
pp. 637-653 ◽  
Author(s):  
W. Kalow ◽  
K. Genest ◽  
N. Staron
Keyword(s):  
Kinetic Studies ◽  
Reaction Rates ◽  
Serum Cholinesterase ◽  
Initial Reaction ◽  
Ultraviolet Spectrophotometry ◽  
First Order ◽  
Low Concentrations ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations

Benzoylcholine stands out from other known substrates of serum cholinesterase because of its high apparent affinity for this enzyme combined with a rapid rate of destruction. The reaction kinetics of the hydrolysis of benzoylcholine can be studied by ultraviolet spectrophotometry, since the absorbance decreases in proportion to the concentration of substrate. Kinetic data obtained by measuring initial reaction rates, and by analyzing continuous hydrolysis curves, are the same within the range of experimental error. The enzymatic data are compatible with the assumption that in the presence of high substrate concentrations a complex consisting of esterase and two substrate molecules is formed. This complex is hydrolyzed more slowly than the complex containing one molecule of substrate which is formed at low concentrations of benzoylcholine. Alkaline hydrolysis of benzoylcholine follows the kinetics of a first order reaction.

scholarly journals Kinetic studies of oxidized nicotinamide–adenine dinucleotide-facilitated reactions of d-glyceraldehyde 3-phosphate dehydrogenase

1974 ◽  
Vol 143 (2) ◽  
pp. 353-363 ◽  
Author(s):  
Patricia J. Harrigan ◽  
David R. Trentham
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Temperature Jump ◽  
Reaction Pathway ◽  
Kinetic Studies ◽  
Rate Equations ◽  
First Order ◽  
Diffusion Controlled ◽  
Relaxation Temperature ◽  
Pig Muscle ◽  
Kinetics Of

The kinetics of the acylation of d-glyceraldehyde 3-phosphate dehydrogenase from pig muscle by 1,3-diphosphoglycerate in the presence of NAD+ has been analysed by using the relaxation temperature-jump method. At pH7.2 and 8°C the rate of acylation of the NAD+-bound (or holo-) enzyme was 3.3×105m−1·s−1 and the rate of phosphorolysis, the reverse reaction, was 7.5×103m−1·s−1. After a temperature-jump perturbation the equilibrium of NAD+ binding to the acyl-enzyme was re-established more rapidly than that of the acylation. The rate of phosphorolysis of the apoacylenzyme from sturgeon muscle and of aldehyde release from the d-glyceraldehyde 3-phosphate–apoenzyme complex were ≤40m−1·s−1 and ≤12s−1 respectively at pH8.0 and 22°C, which means that both processes are too slow to contribute significantly to the reaction pathway of the reversible NAD+-linked oxidative phosphorylation of d-glyceraldehyde 3-phosphate. Phosphorolysis of both acyl-apoenzyme and acyl-holoenzyme was first-order in Pi up to 100mm-Pi and more. PO43− could be the reactive species of the phosphorolysis of the acyl-holoenzyme, in which case phosphorolysis is a diffusion-controlled reaction, although other kinetically indistinguishable rate equations for the reaction are possible.

Sign in / Sign up

Export Citation Format

Share Document