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Showing papers on "Hematite published in 1973"


Journal ArticleDOI
01 May 1973
TL;DR: In this article, a study of the adsorption on hematite (α-Fe2O3) of alkali, alkali earth, chloride, nitrate, sulphate and phosphate ions was made.
Abstract: A study has been made of the adsorption on hematite (α-Fe2O3) of alkali, alkali earth, chloride, nitrate, sulphate and phosphate ions. Use has been made of colloid chemical techniques such as direct determination of surface charge and countercharge and stability studies. In most cases, the results can be explained satisfactorily in terms of the Gouy-Stern theory. All bivalent ions studied produce a shift in the point of zero charge. In Ba(NO3)2 solutions, a restabilization region was observed, indicating superequivalent adsorption of Ba2+. No such irregular series could be observed with K2SO4 or monovalent electrolytes. Phosphate adsorbs very strongly. The isotherms are of the “High Affinity” type. The affinity decreases with decreasing charge contrast between phosphate ions and hematite surface. At high phosphate concentrations, the maximally adsorbed amount of phosphate, if plotted as a function of pH passes through a maximum at pH = pK2. Phosphate ions can also produce restabilization of hematite sols. The sorption process probably proceeds through an exchange against surface OH− or H2O groups. Under given conditions, phosphate ions can be considered as “potential determining.”

254 citations


Journal ArticleDOI
TL;DR: In this paper, a two-constant rate equation was developed which successfully described the rate of phosphate adsorption by hematite and gibbsite conformed to the Freundlich equation.
Abstract: The phosphate adsorption by hematite and gibbsite conformed to the Freundlich equation. The rate of phosphate adsorption was rapid initially and decreased with prolonged reaction time. A two-constant rate equation was developed which successfully described the rate of phosphate adsorption. T

218 citations


Journal ArticleDOI
TL;DR: In this paper, the authors show that the published miscibility gap is too wide (by approximately 15 mole percent at 600°C) and that the consolute temperature is at least 150°C too high.
Abstract: Note: This paper is dedicated to Aaron and Elizabeth Waters on the occasion of Dr. Waters' retirement. Recent analytical data on the compositions of natural hematite-ilmenite solid solutions suggest that the miscibility gap of Carmichael (1961) cannot be correct. Attempts to redetermine the miscibility gap under hydrothermal conditions have been only partly successful, for with the oxygen buffers currently available, it is not possible to retain both hematite and ilmenite phases in a given experiment. Despite the fact that the hydrothermal experiments do not give the maximum solubilities of Fe2O3 in ilmenite and FeTiO3 in hematite, they nevertheless show that the published miscibility gap is too wide (by approximately 15 mole percent at 600°C) and that the consolute temperature is at least 150°C too high.

44 citations


Patent
Franz Hund1
19 Sep 1973
TL;DR: In this article, the red iron (III) oxide pigment was obtained by the use of a foreign modifying substance in the presence of a lattice-distorted, chemically reactive finely divided delta-FeOOH seeds.
Abstract: In the production of a precipitated red iron (III) oxide pigment of hematite structure wherein an aqueous iron (II) salt solution is mixed with an aqueous alkali solution in substantially equivalent quantities to produce an aqueous suspension of iron (II) hydroxide or carbonate, the suspension is oxidized by passing oxygen-containing gases through it with stirring under atmospheric pressure at a temperature of about 0° to 50°C, and the resulting iron (III) seed suspension is allowed to grow into precipitated red iron (III) oxide pigment by further oxidation with an oxygen-containing gas at a temperature of about 50° to 100°C in the presence of more iron (II) salt and alkali solution or in the presence of iron (II) salt and metallic iron at a pH-value kept in the acid range, the improvement which comprises producing the iron (III) seed suspension in the presence of a foreign modifying substance so that lattice-distorted, chemically reactive finely divided delta-FeOOH seeds are formed, whereby the resulting red iron (III) oxide pigment contains less than about 15 % by weight of α-FeOOH. The modifying substance may be a chloride of magnesium, calcium or aluminum, vanadium pentoxide, sodium phosphate, erythritol, mannitol, glyceric acid, K, Na-tartrate, Na-citrate, ribose, glucose, fructose, tannin, or NH 4 --, Ca--, Al--, Fe or Mg-lignin sulfonate.

42 citations


Journal ArticleDOI
TL;DR: In this article, the assemblages rutile-hematite, hematite and magnetite are found in interlayered sedimentary beds of single outcrops in western New Hampshire.
Abstract: The assemblages rutile-hematite, hematite, hematite-magnetite, hematite-ilmenite-magnetite, and ilmenite-magnetite occur in sillimanite- and kyanite-grade quartzites exposed in western New Hampshire. Different assemblages are found in interlayered sedimentary beds of single outcrops. Magnetites are nearly pure Fe3O4 and contain trace amounts of Al, Si, Ti, V, Cr, Mn, and Ni. Magnetites in contact with hematites contain up to 0.4 weight % MnO, but magnetites in contact with ilmenites containing up to 2.3 weight % MnO have no detectable Mn. Ilmenite is enriched in Mn relative to coexisting hematite, and hematite is so enriched with respect to magnetite. Systematic partitioning of elements between oxide minerals and absence of crossing tie lines suggest that the minerals attained chemical equilibrium during regional metamorphism. None of the assemblages are divariant because of the presence of components in addition to FeO, Fe2O3, and TiO2; therefore, none of them constitute oxygen buffers. Nevertheless, gradients in \(\mu _{O_2 } \)between adjacent sedimentary beds can be measured using variations of oxide mineral composition in trivariant and quadrivariant phase assemblages. Oxygen behaved as an “initial value” component or “inert” component during regional metamorphism. It is likely that the \(\mu _{O_2 } \)gradients are due to differences in bulk composition of sedimentary beds at the time of deposition.

40 citations


Journal ArticleDOI
TL;DR: In this paper, the oxidation properties of iron have been investigated at temperatures in the range 800-1000° C in oxygen over the pressure range 0.3-760 Torr.
Abstract: The oxidation properties of iron have been investigated at temperatures in the range 800–1000° C in oxygen over the pressure range 0.3–760 Torr. A duplex scale consisting of wustite and magnetite was formed during the earliest intervals examined. Hematite grew on the magnetite surface after an induction period which decreased with increasing oxygen pressure; this oxide developed as whiskers and platelets at temperatures less than 860° C and as small grains at higher temperatures. Iron transport occurs through the scale and involves short-circuit diffusion in the hematite layer. The oxidation kinetics obeyed a parabolic law independent of oxygen pressure since multilayer scale growth was directly dependent on the lattice diffusivity of iron and the iron gradient established in the wustite layer.

35 citations


Journal ArticleDOI
TL;DR: Pseudomorphic after pyrite framboids, similar size distribution and physical features, biogenic associations as discussed by the authors, similar shape distribution, similar shape and similar shape features.
Abstract: Pseudomorphic after pyrite framboids, similar size distribution and physical features, biogenic associations

31 citations


Journal ArticleDOI
TL;DR: In this article, the optimum conditions for hematite growth were found to be: 5 M NaOH; crystallization temperature, 385-445 °C; percent fill, 71-77%; δT, 5 °C, and seed orientation (1012) and (0001).

28 citations


Journal ArticleDOI
TL;DR: In this article, a concept on the origin of hematite in red-bed deposits as a result of the alteration of ferrihydrite (a hydrous iron oxide with a composition 2.5 Fe2O3 · 4.5 H2O).

23 citations


Journal ArticleDOI
TL;DR: In this article, the main Mossbauer parameters of stoichiometric wustite have been obtained for the paramagnetic and antiferromagnetic regions for the reduction process of hematite at temperatures up to 425 °C.
Abstract: By means of the Mossbauer effect, the wustite formed during the reduction process of hematite below 570 °C has been studied. The main Mossbauer parameters of stoichiometric wustite have been obtained for the paramagnetic and antiferromagnetic regions. The hematite reduction is shown to proceed through the stoichiometric wustite at temperatures up to 425 °C.

21 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of lime and silica addition on the reducibility of sintered iron ore and synthetic hematite pellets was investigated, and it was shown that adding lime and/or silica (up to about 10% total) has little effect on the reduction at 900°C.



01 Jan 1973
TL;DR: Artificial meteor ablation was performed on natural minerals, composed predominately of magnetite and hematite, using an arc heated plasma stream of air as mentioned in this paper, which indicated most was composed of two or more minerals.
Abstract: Artificial meteor ablation was performed on natural minerals, composed predominately of magnetite and hematite, using an arc heated plasma stream of air. Analysis of the ablated debris indicated most was composed of two or more minerals. The more volatile elements were depleted and the relative abundance of Fe increased as a result of both volatile depletion and a reduction in its oxidation state. Hematite was converted to magnetite in the ablation zone, and quartz and apatite minerals were converted to an Fe-rich glass consisting of varying amounts of Si, P, Cl, and Ca, depending upon the accessory minerals available at the time of melting. Artificially created ablation products from iron oxides exhibited unique properties depending on the composition of the original material and the environmental conditions of formation. In addition to the accepted elemental criteria, these properties were morphologic characteristics, textural parameters, and the existence of metastable minerals.

Journal ArticleDOI
TL;DR: In this paper, the authors unify deposits, the material of which had been supplied as thermal solutions and deposited predominantly on the sea floor, under the name of thermal-sedimentary under the assumption that the iron of such deposits had been extracted as Fe2+ from rocks by waters heated by the subterranian heat.
Abstract: The author unites deposits, the material of which had been supplied as thermal solutions and deposited predominantly on the sea floor, under the name of thermal-sedimentary. It is assumed that the iron of such deposits had been extracted as Fe2+ from rocks by waters heated by the subterranian heat. The ferruginous precipitates producing thermal-sedimentary iron ores are formed, in the author's opinion, at discharge points of thermal solutions. Iron contained in them is precipitated as ferrihydrite (2.5Fe2O3·4.5H2O), which spontaneously transforms into hematite.

Patent
05 Oct 1973
TL;DR: In this paper, a highly sorbent iron oxide is prepared by reducing hematite to magnetite followed by a low temperature oxidation prior to contact with sulfur dioxide, which is a more effective form of iron oxide sorbent for the oxides of sulfur.
Abstract: A highly sorbent iron oxide is prepared by reducing hematite to magnetite followed by a low temperature oxidation prior to contact with sulfur dioxide. The oxidized solids obtained in this manner are a more effective form of iron oxide sorbent for the oxides of sulfur.


Journal ArticleDOI
J. Bessiéres1, R. Baro1
TL;DR: The method of Hartman and Perdok using the concept of Periodic Bond Chain has been used to determine theoretically the equilibrium form of hematite α-Fe 2 O 3 crystals.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the misfit dislocation network consists of a three-fold, symmetric dislocation configuration of half partial dislocations, which is in good agreement with those predicted from the postulated model of the network.

Journal ArticleDOI
J. Bessiéres1, R. Baro1
TL;DR: In this paper, the faces formed on crystals of hematite α-Fe 2 O 3, which were obtained by a gaseous phase transport reaction, have been indexed and the order of frequency of the faces is in agreement with the theoretical prediction with the exceptions of (00.1) and {10.1}.

01 Feb 1973
TL;DR: The fundamental aspects of the reduction process are rather complex and it is therefore important that these fundamentals be throughly understood in the development of a new process if sucess is to be achieved as discussed by the authors.
Abstract: Iron ore reduction is the conversion of iron oxide minerals to metallic iron The chemical reactions inv-olved take place in the blast furnace during the prod-uction of hot metal or in the several proposed solid- state processes that produce sponge iron Because there are three oxides of iron, hematite magnetite and wustite and because both carbon and hydrogen are used as reducing agents, the fundamental aspects of the reduction process are rather complex It is therefore important that these fundamentals be throughly understood in the development of a new process if sucess is to be achieved

Journal ArticleDOI
Seizo Watarai1
TL;DR: In this paper, the spin-wave theory was developed for the study of the acoustic soft-magnon modes in hematite (α-Fe 2 O 3 ) and the energies ω 0 of the softmodes were approximately given as ω ∞| T M -T | 1/2 near the Morin phase transition temperature T M and the results were compared with the AFMR experiments.
Abstract: The spin-wave theory is developed for the study of the acoustic soft-magnon modes in hematite (α-Fe 2 O 3 ). The energies ω 0 of the soft-modes are approximately given as ω 0 ∞| T M - T | 1/2 near the Morin phase transition temperature T M and the results are compared with the AFMR experiments.

Patent
25 Jan 1973
TL;DR: In this article, the passing of highly conc electric alternating current through the preheated raw material generating heat arising form the Joule effect and electromagnetic forces resulting in the fast reduction and agglomeration into granules and rod shaped particles of the iron ore and the softening and separation of the gangue which coagulates into pumice stone.
Abstract: The extraction comprises the passing of highly conc electric alternating current through the preheated raw material generating heat arising form the Joule-effect and electromagnetic forces resulting in the fast reduction and agglomeration into granules and rod shaped particles of the iron ore and the softening and separation of the gangue which coagulates into pumice stone The process is used for the redn of hematite, magnetite and natural iron stone It is highly efficient and may be carried out in revolving shaft or endless belt type furnaces

01 Feb 1973
TL;DR: In this paper, a rotary kiln for the production of sponge iron using hematite pellets, bituminous coal and nut coke was examined by microscopial and X-ray methods.
Abstract: Ring formation and heavy build-up in an experimental rotary kiln for production of sponge iron using hematite pellets, bituminous coal and nut coke have been described. The build-up from different parts of the kiln was visually examined and its mineral composition was studies in detail by microscopial and X-ray methods. Besides some metallic iron, the minerals identified were magnetite, fayalite, wustite, iron cordierite, hercynite, anorthite and traces of haematite in different combinations. Relevant binary, ternary and quartenary phase diagrams concerning the obse-rved mineral assemblages were examined in detail. The occurrence of the observed minerals was explained in the light of known phase diagrams. The actual chemical anal-ysis of a sample from the zone of heavy build-up was composed of mainly of FeO. Fe20 A1203 and Si02 (besides some mtallic iron) and this composition was located in relevant phase diagram. The minimum temperature at which liquid would form was indicated from a study of these diagrams.The factors responsible for the build-up were examined.

Journal ArticleDOI
C. Baltzinger1, R. Baro1
TL;DR: In this paper, external forms of etch figures observed on the faces {01.2} of hematite, have shown the influence of the speed of dissolution in the glide plane and the density of ions along directions parallel to those faces.


Journal ArticleDOI
TL;DR: In this paper, the results obtained by a laboratolY scale batch test of the agglomeration oj hematite Jrom aqueos suspension are summarized.
Abstract: In this paper the results obtained by a laboratolY scale batch testJor the agglomeration oj hematite Jrom aqueos suspension are summariz.ed. A large scale maillifacture must be examined, in order to industriali ze the agglomeration method. In the industrial scale process, the Jollowing /Joillts should be remarked. The compression strength oj green /Jellets /Jroduced by the agglomeration method with coal tar as the bridging liquid takes a millimum value at the dring temperature rallge oj 300° to 600°C. T o solve this problem , the Jollowing methods can be considered. (1 ) Establishment oj the drillg /Jrocess at the temperature range oj 300° to 600°C. (2 ) Agglomeration by the use oj bridging liquid which is !lot fired at the temperatures oj 300° to 6'00 'C. The increase oj the amount oj cOlli ill. /Jellet decreases the compressioll strellgth oj reduced pellets. Therefore, the amoullt of coal in pellet should be kept down as low as possible ill order to avoid the degradation oj pellets.


Book ChapterDOI
01 Jan 1973
TL;DR: The most important mineral of the common “rust”, alpha-FeOOH, is usually accompanied by amorphous (not yet crystallized) ferric hydroxide of the same color.
Abstract: The iron content of the earth’s crust averages 5%. At the earth’s surface iron is tied up as green or black ferrous-ferric iron in the ferromagnesian silicates, as the black ferrous-ferric oxide magnetite, as the yellowish ferrous sulphides, pyrite and marcasite; as the grey to dark-brown ferrous carbonate siderite, and as the red or black ferric oxide hematite. The last is not only a common pigment in rock but can also accumulate as our most important iron ore. In humid atmospheres the brown to ochre-brown ferric hydroxide, goethite, is the most important mineral of the common “rust”, alpha-FeOOH. Goethite is usually accompanied by amorphous (not yet crystallized) ferric hydroxide of the same color. Natural rust is summarized as the “mineral” limonite which is not a mineral in the true sense. All the minerals mentioned here tend to adjust to the humid or semi-humid atmospheric surface conditions as they weather to ferric hydroxide or limonite. Metallic iron also changes to rust, mostly amorphous ferric hydroxide with some magnetic brown maghemite, gamma-Fe2O3. Crystallization or aging of the non-crystalline ferric hydroxide leads to the formation of submicroscopic goethite. In some rare instances deep orange gamma-FeOOH, lepidocrocite, can form.