scholarly journals Determination of the Reaction Rate Controlling Resistance of Goethite Iron Ore Reduction Using CO/CO2 Gases from Wood Charcoal

2021 ◽  
Vol 3 (1) ◽  
pp. 27
Author(s):  
Joseph Ogbezode ◽  
Olufemi Ajide ◽  
Soji Ofi ◽  
Oluleke Oluwole
Keyword(s):  
Reduction Process ◽  
Wood Charcoal ◽  
Average Particle ◽  
Average Percentage ◽  
Run Off ◽  
Ash Layer ◽  
Shrinking Core ◽  
Edx Analyses ◽  
Kinetics Of

In the present work, an attempt is made to use non-contact charcoal in the reduction of run-off mine goethite ore at heating temperatures above 570 °C. The reduction mechanism was adopted, following Levenspiel’s relations for the shrinking core model at different stages of reduction. The non-contact charcoal reduction approach is adopted to maximize the benefit of using CO/CO2 gases from charcoal for reduction without the need for beneficiation and concentration. The rate-controlling steps for the reduction kinetics of average particle sizes 5, 10, 15, and 20 mm at 570, 700, 800, 900, and 1000 °C were studied after heat treatment of the ore-wood charcoal at a total reduction time of 40 min using activated carbon reactor. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses were done to investigate the spectrometric phase change and metallic components of the ore sample after reduction, respectively. The average percentage of the metallic iron content (56.6, 60.8, and 61.7%) and degree of metallization (91.62, 75.96, and 93.6%) are achieved from the SEM/EDX analysis of the reduced ore sample at reduction temperatures of 570, 800, and 1000 °C, respectively. The results indicate the tendency for high carbon deposit at the wustite stage of the reduction process at the lowest of temperature 570oC and the residence time of at 10 min. This study demonstrates that diffusion through the ash layer is the controlling resistance of the overall reduction process.

Kinetics of synthesizing process for obtaining iron nanopowder by chemical-metallurgical method under isothermal conditions

2021 ◽  
pp. 72-77
Author(s):  
Tien Hiep Nguyen ◽  
◽  
Van Minh Nguyen ◽  
Keyword(s):  
Hydrogen Reduction ◽  
Average Particle Size ◽  
Chemical Deposition ◽  
Reduction Process ◽  
Nitrogen Adsorption ◽  
Specific Rate ◽  
Average Particle ◽  
Isothermal Conditions ◽  
Electron Microscopes ◽  
Kinetics Of

In this work the kinetics of synthesizing process of metallic iron nanopowder by hydrogen reduction from α-FeOOH hydroxide under isothermal conditions were studied. α-FeOOH nanopowder was prepared in advance by chemical deposition from aqueous solutions of iron nitrate Fe(NO3)3 (10 wt. %) and alkali NaOH (10 wt. %) at room temperature, pH = 11, under the condition of continuous stirring. The hydrogen reduction process of α-FeOOH nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 390 to 470 °C. The study of the crystal structure and composition of the powders was performed by X-ray phase analysis. The specific surface area S of the samples was measured using BET method by low-temperature nitrogen adsorption. The average particle size D of powders was determined via the measured S value. The size characteristics and morphology of the particles were investigated by transmission and scanning electron microscopes. The calculation of the kinetic parameters of the hydrogen reduction process of α-FeOOH under isothermal conditions was carried out by the Gray-Weddington model and Arrhenius equation. It is shown that the rate constant of reduction at 470 °C is approximately 2.2 times higher than in the case at 390 °C. The effective activation energy of synthesizing process of iron nanopowder by hydrogen reduction from α-FeOOH was ~38 kJ/mol, which indicates a mixed reaction mode. In this case, the kinetics overall process is limited by both the kinetics of the chemical reaction and the kinetics of diffusion, respectively, an expedient way to accelerate the process by increasing the temperature or eliminate the diffusion layer of the reduction product by intensive mixing. It is show that Fe nanoparticles obtained by hydrogen reduction of its hydroxide at 410 °C, corresponding to the maximum specific rate of the reduction process, are mainly irregular in shape, evenly distributed, the size of which ranges from several dozens to 100 nm with an average value of 75 nm.

scholarly journals Kinetics of Iron Bioleaching using Isolated Leptospirillum Ferriphilum: Effect of Temperature

2019 ◽  
Vol 8 (12) ◽  
pp. 76-81
Keyword(s):  
Average Particle Size ◽  
Effect Of Temperature ◽  
Average Particle ◽  
Optimum Temperature ◽  
Leptospirillum Ferriphilum ◽  
Ash Layer ◽  
Initial Ph ◽  
Kinetics Of ◽  
Rate Controlling Step ◽  
Leaching Efficiency

This study was designed to investigate the effect of temperature on iron bioleaching kinetics using Leptospirillum ferriphilum. The bacteria were isolated and subjected to molecular characterization technique for confirming L. ferriphilum. Using the isolate, bioleaching data were collected in the temperature range of 298–318 K at an initial pH of 1.5 and 5% pulp density with an average particle size being 300 µm. The results of experiments concluded that leaching efficiency increases with temperature and maximum of 93.85% were observed after 20 days at 313 K. The bioleaching kinetics indicated that the maximum rate (rate constant: 0.1452 d1 ) was found in the experiment conducted at the optimum temperature, and the rate-controlling step was “diffusion through ash layer.” The activation energy was calculated to be 37.59 kJ/mol. From the thermodynamic study of the bioleaching system, ∆H˚ and ∆S˚ were found to be 0.7399 × 10−3 and 28.512 J/mol, respectively

scholarly journals Effect of FE (II) Concentration on Bioleaching of Zinc from Sphalerite using Leptospirillum Ferriphilum: Kinetic Aspects

2019 ◽  
Vol 9 (1) ◽  
pp. 1492-1498
Keyword(s):  
Inoculum Size ◽  
Molecular Techniques ◽  
Leaching Rate ◽  
Experimental Conditions ◽  
Leptospirillum Ferriphilum ◽  
Ash Layer ◽  
Initial Ph ◽  
System Temperature ◽  
Shrinking Core ◽  
Kinetics Of

The objective of this study was to isolate an acidophilic iron-oxidizing bacterium, Leptospirillum ferriphilum, and explore the impacts of initial Fe(II) concentration on the bioleaching kinetics of zinc retrieval from sphalerite concentrate. L. ferriphilum strain was successfully isolated from Chitradurga mine, Karnataka, India, and molecular techniques for DNA sequencing were applied. The obtained nucleotide sequence was deposited to GenBank and accession number KF743135 was granted. The effect of Fe(II) on the iron-based bioleaching kinetics of zinc leaching using the L. ferriphilum isolate was ascertained under the following experimental conditions: inoculum size, 10% (v/v); bioleaching period, 20 days; system temperature, 301±2 K; initial pH, 3; pulp density 5% (w/v); and Fe(II) concentration in the medium, 1–9 g/L. The results demonstrated that efficiency of bioleaching was highly influenced by concentration of Fe(II) and maximized yield of 87.85% zinc was obtained at 7 g/L. The kinetic study specify that the rate constant estimations of zinc biosolubilization were moderately high at 7 g/L Fe(II), and the kinetic analysis using shrinking core model showed that the leaching rate is constrained by ash layer diffusion step

scholarly journals Bioleaching kinetics of trace metals from coal ash using Pseudomonas spp.

2019 ◽  
Vol 268 ◽  
pp. 01010
Author(s):  
Denvert Pangayao ◽  
Michael Angelo Promentilla ◽  
Susan Gallardo ◽  
Eric van Hullebusch
Keyword(s):  
Coal Ash ◽  
Pseudomonas Spp ◽  
Controlling Mechanism ◽  
Ash Layer ◽  
Copper Manganese ◽  
Initial Ph ◽  
Shrinking Core ◽  
Linear Plot ◽  
Kinetics Of ◽  
Layer Control

The kinetics of bioleaching of chromium, copper, manganese and zinc from coal ash using Pseudomonas spp. isolated from coal ash pond was investigated. From the previous study, parameters used for bioleaching were 1% pulp density, 90 rpm, 37°C and 5 ml inoculum was placed in a 100 ml fresh medium with the ash. These conditions were used for bioleaching of coal ash for 30 days. Moreover, the initial pH of the solution is 8.20 and decreases to 8.61. After 30 days of bioleaching, the maximum metal leached were 13.77% Cr, 14.61% Cu, 6.33% Mn and 12.18% Zn. Assuming that the coal ash will shrink uniformly with respect to time using Shrinking Core Model, the kinetic data showed linear plot for percent metal leached versus time, suggested that diffusion through ash layer control was the rate controlling mechanism.

scholarly journals Kinetics of Pb and Zn leaching from zinc plant residue by sodium hydroxide

2015 ◽  
Vol 51 (1) ◽  
pp. 89-95 ◽  
Author(s):  
M. Erdem ◽  
M. Yurten
Keyword(s):  
Plant Residue ◽  
Core Model ◽  
Diffusion Control ◽  
Shrinking Core Model ◽  
Zinc Plant ◽  
Ash Layer ◽  
Shrinking Core ◽  
Important Amount ◽  
Increasing Demand ◽  
Kinetics Of

In the hydrometallurgical zinc production processes, important amount of hazardous solid extraction residue containing unextractable Zn and Pb is generated. Due to increasing demand of metals and the depletion of high grade natural resources, these types of wastes are gaining great importance in the metallurgical industries. In this study, selective leaching and leaching kinetics of Pb and Zn from zinc extraction residue were investigated. For this purpose; the effects of NaOH concentration, contact time, stirring speed and temperature on the Pb and Zn recovery from the residue were studied. The shrinking core model was applied to the results of the experiments. Leaching results showed that 85.55% Pb and 21.3 % Zn could be leached under the optimized conditions. The leaching of Pb and Zn were found to fit well to shrinking core model with ash layer diffusion control. Activation energy values for Pb and Zn leaching were calculated to be 13.645 and 22.59 kJ/mol, respectively.

A New Method for Direct Determination of the Recoilless Fraction with Application to Magnetic Nanoparticles

2002 ◽  
Vol 721 ◽  
Author(s):  
Monica Sorescu
Keyword(s):  
Room Temperature ◽  
Average Particle Size ◽  
Direct Determination ◽  
Average Particle ◽  
Lattice Method ◽  
Recoilless Fraction ◽  
Single Room ◽  
Magnetite Particles ◽  
Physical Mixtures

AbstractWe propose a two-lattice method for direct determination of the recoilless fraction using a single room-temperature transmission Mössbauer measurement. The method is first demonstrated for the case of iron and metallic glass two-foil system and is next generalized for the case of physical mixtures of two powders. We further apply this method to determine the recoilless fraction of hematite and magnetite particles. Finally, we provide direct measurement of the recoilless fraction in nanohematite and nanomagnetite with an average particle size of 19 nm.

Determination of microbiological activity during the processing of frost damaged sugar beets

2014 ◽  
pp. 228-231 ◽  
Author(s):  
Maciej Wojtczak ◽  
Aneta Antczak-Chrobot ◽  
Edyta Chmal-Fudali ◽  
Agnieszka Papiewska
Keyword(s):  
Sugar Beet ◽  
Microbiological Activity ◽  
Microbiological Contamination ◽  
Sugar Beets ◽  
Bacterial Metabolites ◽  
Kinetics Of

The aim of the study is to evaluate the kinetics of the synthesis of dextran and other bacterial metabolites as markers of microbiological contamination of sugar beet.

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

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