A Kinetic Model for Autotrophic Denitrification using Sulphur:Limestone Reactors

2003 ◽  
Vol 38 (1) ◽  
pp. 183-192 ◽  
Author(s):  
Ashref Darbi ◽  
Thiruvenkatachari Viraraghavan
Keyword(s):  
Particle Size ◽  
Kinetic Model ◽  
Reaction Rate ◽  
Average Particle Size ◽  
Order Reaction ◽  
Average Particle ◽  
Thiobacillus Denitrificans ◽  
Autotrophic Denitrification ◽  
Reaction Rate Constants ◽  
Kinetics Of

Abstract The kinetics of autotrophic denitrification of groundwater by Thiobacillus denitrificans in a sulfur:limestone upflow reactor was examined in order to predict effluent concentrations. Experiments were performed using water containing 60 and 90 mg NO3—N/L and sulfur and limestone with average particle size of 3.5 mm. Results clearly showed that nitrate was completely removed from 60 and 90 mg NO3—N/L influent concentrations. The results showed that the autotrophic denitrification rates in sulfur:limestone reactors can be described by half-order kinetics. The half-order reaction rate constants for the entire media were estimated at 1.34 and 1.54 mg1/2/L1/2 h for influent concentrations of 60 and 90 mg NO3—N/L, respectively.

Kinetic study and modeling of the solid-state reaction Y2BaCuO5 + 3BaCuO2 + 2CuO ⇉ 2YBa2Cu3O6.5−x + xO2

1990 ◽  
Vol 5 (10) ◽  
pp. 2056-2065 ◽  
Author(s):  
Nae-Lih Wu ◽  
Ta-Chin Wei ◽  
Shau-Y Hou ◽  
S-Yen Wong
Keyword(s):  
Particle Size ◽  
Solid State ◽  
Solid State Reaction ◽  
Size Dependence ◽  
Average Particle Size ◽  
Average Particle ◽  
Fractional Conversion ◽  
X Ray ◽  
Unreacted Core ◽  
Kinetics Of

The kinetics of the solid-state reaction Y2BaCuO5 + 3BaCuO2 + 2CuO ⇉ 2YBa2Cu3O6.5−x + xO2 was studied by using x-ray diffractometric and thermogravimetric analyses. Both analyses established that the reaction was well described by the kinetic equation: 1 − 3(1 − F)2/3 + 2(1 − F) = k0 exp(− E/RT)t, where F is the fractional conversion of a calcined powder, E is 520 kcal/molc and, for a rcactant mixture with an average particle size of 3 μm, k0 is 2.03 ⊠ 1092 min−1. An unreacted-core shrinking model was proposed to obtain the particle-size dependence of the reaction, and predicted that the pre-exponential constant k0 changed with reactant particle size by k0 = 2.03 ⊠ 1092(3/d)2 exp(4/d − 4/3), where d is the average reactant particle size in μm.

Effects of Carrageenan and Chitosan as Coating Materials on the Thermal Degradation of Microencapsulated Phycocyanin from Spirulina sp.

2019 ◽  
Vol 15 (5-6) ◽  
Author(s):  
H. Hadiyanto ◽  
Marcelinus Christwardana ◽  
Meiny Suzery ◽  
Heri Sutanto ◽  
Ayu Munti Nilamsari ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Thermal Degradation ◽  
Rate Constants ◽  
Reaction Rate ◽  
Order Reaction ◽  
Coating Materials ◽  
First Order ◽  
Reaction Rate Constants ◽  
Kinetics Of

AbstractPhycocyanin is a natural substance that can be used as an antioxidant and food colorant. The quality of phycocyanin deteriorates when it is exposed to heat, and such deterioration is evidenced by decreases in its antioxidant activity and color. Encapsulation, which introduces a coating material over a substance of interest, has been applied to prevent changes in substance quality. The objective of the present research is to evaluate the kinetics of thermal degradation of phycocyanin coated with carrageenan or chitosan. Encapsulated phycocyanin samples were exposed to temperatures of 40, 50, or 60 °C for 90 min, and kinetics of the resulting degradation was evaluated to determine changes in sample quality. The results showed that the thermal degradation of encapsulated phycocyanin at 40–60 °C follows first-order reaction kinetics with reaction rate constants (k) of 4.67–9.17 × 10–5 s-1 and 3.83–7.67 × 10–5 s-1 for carrageenan and chitosan, respectively, and that the k of encapsulated phycocyanin is slower than that obtained from samples without the coating materials (control). Encapsulation efficiencies (EE) of 68.66 % and 76.45 %, as well as loading capacities of 45.28 % and 49.16 %, were, respectively, obtained for carrageenan and chitosan.

scholarly journals Kinetics and Photodegradation Study of Aqueous Methyltert-Butyl Ether Using Zinc Oxide: The Effect of Particle Size

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Zaki S. Seddigi ◽  
Saleh A. Ahmed ◽  
Shahid P. Ansari ◽  
Ekram Danish ◽  
Abdullah Abu Alkibash ◽  
...  
Keyword(s):  
Particle Size ◽  
Zinc Oxide ◽  
Order Reaction ◽  
Average Particle ◽  
Particle Sizes ◽  
Mercury Lamp ◽  
Butyl Ether ◽  
First Order ◽  
Effect Of Particle Size ◽  
Kinetics Of

Zinc oxide of different average particle sizes 25 nm, 59 nm, and 421 nm as applied in the photodegradation of MTBE. This study was carried out in a batch photoreactor having a high pressure mercury lamp. Zinc oxide of particle size of 421 nm was found to be the most effective in degrading MTBE in an aqueous solution. On using this type of ZnO in a solution of 100 ppm MTBE, the concentration of MTBE has decreased to 5.1 ppm after a period of five hours. The kinetics of the photocatalytic degradation of MTBE was found to be a first order reaction.

scholarly journals Kinetics of Heavy Metal Ion Adsorption on to, and Proton Release from, Electrolytic Manganese Dioxide

1998 ◽  
Vol 16 (1) ◽  
pp. 39-50 ◽  
Author(s):  
Madhav P. Dahal ◽  
Geoffrey A. Lawrance ◽  
Marcel Maeder
Keyword(s):  
Kinetic Model ◽  
Metal Ions ◽  
Manganese Dioxide ◽  
Metal Ion ◽  
Average Particle Size ◽  
Transition Metal Ions ◽  
Average Particle ◽  
Electrolytic Manganese Dioxide ◽  
Electrolytic Manganese ◽  
Kinetics Of

The kinetics of adsorption of lead(II), as well as of copper (II), zinc(II) and thallium(I), on commercial electrolytic manganese dioxide (EMD) powder of different size fractions has been followed by a pH-stat method involving the computer-controlled neutralisation of released protons from the EMD at a fixed pH with hydroxide ion. Base uptake versus time profiles in all cases indicated a rapid initial change followed by a slower process. These can be interpreted in terms of either a solution kinetic model or an adsorption kinetic model. In the former analysis, the adsorption-time profile can be interpreted in terms of two, or at most three, exponentials. The contribution of the first fast step increases with decreasing average particle size (or increasing surface area), consistent with its interpretation as being associated with the replacement of accessible protons on the exposed surface of the EMD by metal ions. The slower rate processes can be considered to be associated with adsorption in less accessible clefts or pores in the structure. In the diffusion model, the experimental data were fitted to the equation of diffusion in a sphere, fitting again requiring a first initial step followed by a slower step, with one diffusion coefficient having typically an upper limit of 10-9 and the other a lower limit of 10-11 cm2/s. For the complete reaction, the moles of protons released per mole of metal ion adsorbed were also measured and found to be relatively insensitive with respect to pH, metal ion concentration, electrolyte concentration and EMD size fraction. At pH 4, the H+: Mn+ ratio ranged from 1.4 to 2.1 (±0.1) for divalent transition metal ions, consistent with dominant chelation of the divalent metal ion to two adjacent oxygen sites on the surface; for thallium(I), a low ratio (0.5) indicated a different mode of surface attachment.

Kinetic Investigations of Biodiesel from Cottonseed Oil and Ethanol by Transesterification in Biomaterial and its Application

2012 ◽  
Vol 578 ◽  
pp. 73-77 ◽  
Author(s):  
Jin Si Chen ◽  
Xian Guo Hu ◽  
Xiang Yang Wang ◽  
Yu Fu Xu ◽  
En Zhu Hu
Keyword(s):  
Potassium Hydroxide ◽  
Reaction Rate ◽  
Cottonseed Oil ◽  
Order Reaction ◽  
Order Model ◽  
Reaction Rate Constants ◽  
Pseudo Second Order ◽  
Zero Order Reaction ◽  
Kinetic Investigations ◽  
Kinetics Of

The kinetics of transesterification for biodiesel produced by cottonseed oil and ethanol in catalyst (potassium hydroxide) was investigated. The reaction of transesterification can be described by pseudo second order model for the initial stages of the reaction, followed by zero order reaction. The reaction rate constants for transestentcation of cottonseed oil with ethanol at 40°C, 60°C and 78°C are 0.0996, 0.1126and0.1286 L•mol-1/min-1 respectively, and the activation energy of transesterification is 21.6075kJ/mol．

Kinetics of Reductive Dechlorination of DDT in Soil with Zero-Valent Iron

2011 ◽  
Vol 295-297 ◽  
pp. 1236-1239
Author(s):  
Yin Hai Lang ◽  
Min Jie Wang ◽  
Nan Nan Wang
Keyword(s):  
Kinetic Model ◽  
Reductive Dechlorination ◽  
Reaction Rate ◽  
Zero Valent Iron ◽  
Order Kinetic ◽  
First Order ◽  
Reaction Rate Constants ◽  
Order Kinetic Model ◽  
Pseudo First Order ◽  
Kinetics Of

In this study, reductive dechlorination of DDT compounds by zero-valent iron in Jiangxi red soil was investigated. DDT compounds were effectively dechlorinated by zero-valent iron. The pseudo-first-order kinetic model for 2,4¢-DDT and 4,4¢-DDT reduction with zero-valent iron was proposed. The reaction rate constants for 2,4¢-DDT and 4,4¢-DDT were 1.19´10-2(min-1) and 1.44´10-2(min-1), respectively. The dechlorination of 2,4¢-DDT and 4,4¢-DDT were mainly affected by the specific surface area of iron. The data from the variable-pH experiments (between 3.6 and 8.8) suggested that pH does not play a role in the rate-determination step.

Modelling of Moisture Content, β-Carotene and Deformation Variation during Drying of Carrot

2019 ◽  
Vol 15 (7) ◽  
Author(s):  
Souad Timoumi ◽  
Daoued Mihoubi ◽  
Fethi Zagrouba
Keyword(s):  
Reaction Rate ◽  
Order Reaction ◽  
Convective Drying ◽  
Agricultural Product ◽  
First Order ◽  
Reaction Rate Constants ◽  
Drying Model ◽  
Kinetics Of ◽  
Β Carotene ◽  
Carotene Degradation

AbstractIn this work a two-dimensional convective drying model of heat, mass and momentum transfer is developed taking account of the shrinkage and the quality degradation of carrots. The kinetics of β-carotene degradation in dried agricultural product is considered to follow a first-order reaction. Temperature dependence of the reaction rate constants followed the Arrhenius relationship. The developed model, describes the strong coupling between mass, heat and momentum transfers, shrinkage and quality (β-carotene) changes and takes into account the dehydration of the solid caused by a temperature increase.

Effect of ferrous ion concentration on the kinetics of radiation-induced iron-oxide nanoparticle formation and growth

2017 ◽  
Vol 19 (1) ◽  
pp. 695-708 ◽  
Author(s):  
T. I. Sutherland ◽  
C. J. Sparks ◽  
J. M. Joseph ◽  
Z. Wang ◽  
G. Whitaker ◽  
...  
Keyword(s):  
Particle Size ◽  
Kinetic Modelling ◽  
Average Particle Size ◽  
Ion Concentration ◽  
Iron Oxide Nanoparticle ◽  
Average Particle ◽  
Gamma Radiolysis ◽  
Radiation Induced ◽  
Oxide Nanoparticle ◽  
Kinetics Of

Magnetite nanoparticles with a narrow size distribution were produced via gamma-radiolysis of FeSO4 solutions. The average particle size increased with [Fe2+]0. A multistage mechanism (supported by radiolysis kinetic modelling) is described that can explain the observed dependence of particle size on [Fe2+]0.

scholarly journals Passage kinetics of digesta in horses fed with coastcross hay ground to different degrees

2014 ◽  
Vol 38 (5) ◽  
pp. 506-514 ◽  
Author(s):  
Vinicius Pimentel Silva ◽  
Fernando Queiroz de Almeida ◽  
Róbson Ricardo Moreira Pimentel ◽  
Fernanda Nascimento de Godoi ◽  
Tiago Marques dos Santos ◽  
...  
Keyword(s):  
Particle Size ◽  
Liquid Phase ◽  
Transit Time ◽  
Solid Phase ◽  
Average Particle Size ◽  
Neutral Detergent Fiber ◽  
Average Particle ◽  
Passage Rate ◽  
The Right ◽  
Kinetics Of

This study was conducted to evaluate the kinetics, physicochemical characteristics and particle size of digesta in the right ventral colon (RVC) of horses fed coastcross hay ground to different degrees. Four horses fitted with cannulae in the RVC were used and were fed the following forms of hay: long, chopped, ground to 5 mm and ground to 3 mm. A Latin Square 4x4 study design was used. Each experimental period included 10 days for diet adaptation, four days for feces collection and one day for digesta collection. The kinetics of the particulate and solute phases of digesta were evaluated based on the mean retention time (MRT), passage rate (k) and transit time (TT) using two external markers: Cr-NDF and Co-EDTA. The TT of solid phase digesta was 3 hours longer (P<0.05) for ground hay than with the other physical forms of hay. There was no difference (P>0.05) in k or MRT in either the liquid or solid phase of digesta as a function of the different degrees of hay grinding. However, the liquid phase of digesta presented a higher k than the solid phase, with values of 3.28 and 2.73 h-1 being obtained, respectively. The smallest particle size and the lowest neutral detergent fiber contents in colon digesta were observed when hay ground to 3 mm was offered, leading to values of 0.51 mm and 53.46%, respectively. Grinding the hay increased the transit time of the liquid phase in the digestive tract of the horses, whereas no change in the kinetics of the solid phase digesta was observed. The grinding of hay reduced the NDF and the average particle size in the right ventral colon.

scholarly journals Reaction Rate Analysis of Manganese Ore Prereduction in CO-CO2 Atmosphere

2021 ◽  
Author(s):  
Trine Asklund Larssen ◽  
Dieter Senk ◽  
Merete Tangstad
Keyword(s):  
Particle Size ◽  
Reaction Rate ◽  
Average Particle Size ◽  
Reduction Rate ◽  
Reaction Rates ◽  
Average Particle ◽  
State Reduction ◽  
Manganese Ores ◽  
Rate Analysis ◽  
Co Concentration

AbstractVariations in energy efficiency and climate gas emissions in production of manganese ferroalloys are largely related to the solid-state reduction of the manganese ores used as raw material in the production. The gas-solid reduction is known to be dependent on the ore characteristics, making information on the factors governing the kinetics crucial. A reaction rate analysis of thermogravimetric data obtained for the reduction of Comilog and Nchwaning manganese ores in CO-CO2 atmosphere was performed. Experimental variables were CO partial pressure, ore particle size, temperature regimes (isothermal/non-isothermal), as well as heating rate for non-isothermal experiments. The effects of particle size, CO-concentration, and temperature on the reaction rates were quantified. It was found that the reduction rate of both ores was proportional to the inverse average particle size. Different sensitivities towards the CO-concentration in the gas feed was determined, where the rate of Comilog-ore was proportional to $$ p_{\text{CO}}^{0.7} $$ p CO 0.7 , and Nchwaning to $$ p_{\text{CO}}^{1.5} $$ p CO 1.5 . The activation energy of Comilog ore was estimated to be 17 kJ/mol, whereas 63 kJ/mol was found for Nchwaning ore.

Sign in / Sign up

Export Citation Format

Share Document