scholarly journals Electrolytic iron production from alkaline suspensions of solid oxides: compared cases of hematite, iron ore and iron-rich Bayer process residues

2020 ◽  
Vol 10 (2) ◽  
pp. 95-102 ◽  
Author(s):  
Abdoulaye Maihatchi ◽  
Marie-Noëlle Pons ◽  
Quentin Ricoux ◽  
Frederic Goettmann ◽  
Francois Lapicque
Keyword(s):  
Current Density ◽  
Red Mud ◽  
Iron Ore ◽  
Cathode Surface ◽  
Particle Surface ◽  
Bayer Process ◽  
Solid Oxides ◽  
Mineral Phases ◽  
Reductive Treatment ◽  
Very High

Iron can be produced by the direct electrochemical reduction of hematite particles suspended in hot, concentrated NaOH solutions. Because various other iron sources can be considered, the present work was aimed at investigating the electrolytic treatment of the “red mud” generated by the Bayer process for alumina preparation from bauxite. Such sources contain very high amounts of impurities, in particular silicon and aluminium oxide-based minerals, in addition to other mineral phases. Electrolytic reductive treatment of the industrial red mud sample was shown to be possible but with both lower current density and current efficiency than for pure hematite. After deposition tests at a fixed current density, further experiments in simulation tests have been carried out for better understanding. In particular, hematite particles were tested with and without impurities introduced in the solution. Presence of little soluble impurities at the particle surface appear to hinder the reactivity of the suspended particles at the cathode surface, whereas side-hydrogen reaction still occurs. 

Effect of soil amendment with bauxite Bayer process residue (red mud) on the availability of phosphorus in very sandy soils

Soil Research ◽  
2003 ◽  
Vol 41 (6) ◽  
pp. 1229 ◽  
Author(s):  
Katherine Snars ◽  
Robert Gilkes ◽  
Jeffrey Hughes
Keyword(s):  
Red Mud ◽  
Soil Amendment ◽  
Chemical Properties ◽  
Sandy Soils ◽  
Bayer Process ◽  
Dilute Acid ◽  
Retention Capacity ◽  
Pasture Production ◽  
Very High ◽  
P Retention

The chemical properties of red mud, a by-product of Bayer process refining of bauxite to alumina, make disposal of the material problematic. It is very alkaline (pH >11), contains a large amount of sesquioxides, and thus has a very high P retention capacity. These characteristics have encouraged its use as a soil amendment to enhance P retention of soils so as to reduce leaching of P. To investigate the effect of added red mud on the availability of existing P in sandy soils an incubation experiment was conducted using 3 types of red mud (untreated red mud, red mud amended with 5% gypsum, and red mud leached with dilute acid to remove all soluble salts) mixed with 12 podsol topsoils at rates of 0, 2.5, 5, 10, 20, and 40�t/ha. The mixtures were incubated wet for 28 days in the dark at 20°C, both with and without a microbial inhibitor. The decrease in 0.5 M sodium bicarbonate extractable phosphorus (bic-P) was 40–60% of initial bic-P at 40 t/ha of all 3 red muds after wet incubation without microbial suppressant. This decreased to 20–40% after drying or with addition of the microbial suppressant. The decrease in bic-P was not due to the increase in pH due to red mud application and appears to involve both chemical and microbial actions. The increase in soil pH of up to 3 units would be beneficial for pasture production at most rates of red mud application and the associated increase in electrical conductivity is not sufficient to affect plant growth.

Microstructure Development in a High Current Density NbTi Superconducting Composite

1985 ◽  
Vol 43 ◽  
pp. 186-189
Author(s):  
P. J. Lee ◽  
D. C. Larbalestier
Keyword(s):  
Current Density ◽  
High Current Density ◽  
Cold Drawing ◽  
Heat Treatments ◽  
Grain Structure ◽  
Fine Grain ◽  
Boundary Film ◽  
Quantitative Basis ◽  
Cold Worked ◽  
Very High

Several features of the metallurgy of superconducting composites of Nb-Ti in a Cu matrix are of interest. The cold drawing strains are generally of order 8-10, producing a very fine grain structure of diameter 30-50 nm. Heat treatments of as little as 3 hours at 300 C (∼ 0.27 TM) produce a thin (1-3 nm) Ti-rich grain boundary film, the precipitate later growing out at triple points to 50-100 nm dia. Further plastic deformation of these larger a-Ti precipitates by strains of 3-4 produces an elongated ribbon morphology (of order 3 x 50 nm in transverse section) and it is the thickness and separation of these precipitates which are believed to control the superconducting properties. The present paper describes initial attempts to put our understanding of the metallurgy of these heavily cold-worked composites on a quantitative basis. The composite studied was fabricated in our own laboratory, using six intermediate heat treatments. This process enabled very high critical current density (Jc) values to be obtained. Samples were cut from the composite at many processing stages and a report of the structure of a number of these samples is made here.

RESTORATION OF MACHINE PARTS WITH GALVANIZED ZINC COATINGS

2020 ◽  
Vol 4 (141) ◽  
pp. 140-147
Author(s):  
MIKHAIL VIKHAREV ◽  
◽  
VLADIMIR YUDIN ◽  
VESELOVSKIY NIKOLAY ◽  
◽  
...  
Keyword(s):  
Current Density ◽  
Cathode Surface ◽  
Zinc Coating ◽  
Cathode Current Density ◽  
Research Purpose ◽  
Cathode Layer ◽  
Properties Of Coatings ◽  
Chemical Polarization ◽  
Cathode Current ◽  
Zinc Coatings

The article shows the role of electroplating in the restoration of parts, indicates the advantages of restoring parts with electroplating over other methods, and gives the characteristics and properties of coatings obtained by electroplating. (Research purpose) The research purpose is in increasing the speed of application of zinc electroplating when restoring parts. (Materials and methods) The cathode current density has a decisive influence on the coating speed. The main reason for limiting the cathode current density during galvanizing from sulfuric acid electrolytes is the chemical polarization of the cathode. The article presents a study on the designed installation for the application of galvanic coatings. When applying coatings to the internal surfaces of parts, there was used a device with activating elements having an electromechanical rotation drive. This device prevents depletion of the near-cathode layer of the electrolyte and reduces the chemical polarization of the cathode. Elements made of moisture-resistant skin were used as activators. (Results and discussion) The article presents the results of experiments as a dependence of the coating speed on the speed of the activator relative to the restoring surface. It also presents the relationship between the size of the abrasive grains of the activating elements, the force of their pressing against the cathode surface, the speed of movement of the activator and the speed of applying the zinc coating, as well as its quality. By activating the cathode surface, it was possible to raise the operating current density to 100-150 amperes per square decimeter. The speed of application of zinc coatings is 16-25 micrometers per minute. (Conclusions) In the course of research, authors determined the conditions of electrolysis during galvanizing, which provide a significant increase in the cathode current density and the rate of application of these coatings during the restoration of parts.

Complex Additives on the Basis of Red Mud for Intensification of Iron-Ore Sintering and Pelletizing

2015 ◽  
pp. 107-111
Author(s):  
Gennadiy Podgorodetskiy ◽  
Vladislav Gorbunov ◽  
Andrey Panov ◽  
Sergey Petrov ◽  
Sergey Gorbachev
Keyword(s):  
Red Mud ◽  
Iron Ore ◽  
Iron Ore Sintering ◽  
Ore Sintering

Production of Free Radicals Arising from the Surface Activity of Minerals and Oxygen. Part I. Iron Mine Ores

1985 ◽  
Vol 5 (6) ◽  
pp. 1061-1078 ◽  
Author(s):  
Dominique Costa ◽  
Joelle Guignard ◽  
Roger Zalma ◽  
Henri Pezerat
Keyword(s):  
Surface Activity ◽  
Iron Ore ◽  
Particle Surface ◽  
Radical Oxygen Species ◽  
Lung Cancers ◽  
Surface Sites ◽  
Iron Mine ◽  
Mineral Dusts ◽  
Trapping Agent ◽  
Excess Incidence

The excess incidence of lung cancers observed in many metal mines probably is not only correlated with radioactivity but also with the inhaled dusts. In an attempt to determine a possible mechanism of carcinogenicity related to the surface activity of dusts, using the spin-trapping agent and ESR spectroscopy, one can demonstrate that some mineral dusts from iron ore mines are very active in an oxidative process in aqueous medium, implying the formation of radical oxygen species on reducing surface sites of the solid. This reducing surface activity of the dusts depends on the presence of Fe2+ ion in the lattice and on the process of activation and passivation of the surface sites. The more simple process of activation is the dissolution of the oxidized coating on the particle surface. Among the oxides, oxyhydroxides, carbonates, and silicates, the magnesium-iron phyllosilicates (chlorite, biotite, berthierine) appear the most active. The siderite FeCO3 is also active, but the iron oxides and oxyhydroxides are generally nonactive.

A high critical current density MOCVD coated conductor with strong vortex pinning centers suitable for very high field use

2009 ◽  
Vol 22 (5) ◽  
pp. 055013 ◽  
Author(s):  
Z Chen ◽  
F Kametani ◽  
Y Chen ◽  
Y Xie ◽  
V Selvamanickam ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
High Field ◽  
Vortex Pinning ◽  
Coated Conductor ◽  
High Critical Current Density ◽  
Pinning Centers ◽  
Strong Vortex ◽  
Very High

Very high current density pseudomorphic double channel In0.49Ga0.51P/In0.3Ga0.7As/GaAs HEMT

1997 ◽  
Vol 33 (7) ◽  
pp. 627 ◽  
Author(s):  
H.-P.D. Yang ◽  
F.C. Hwang
Keyword(s):  
Current Density ◽  
High Current Density ◽  
High Current ◽  
Double Channel ◽  
Very High

Red Mud Flocculants Used in the Bayer Process

2013 ◽  
pp. 425-430
Author(s):  
F. Ballentine ◽  
M. E. Lewellyn ◽  
S. A. Moffatt
Keyword(s):  
Red Mud ◽  
Bayer Process
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