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Oxidation of pyrite in coal to magnetite ScienceDirect

May 01, 1984 Although oxid- ation may start at lower temperatures, the pyrite in all the samples studied, when heated in an anoxic atmosphere, showed significant changes in magnetization (oxidation) at > % 390. Initially, the pyrite is partially converted to magnetite and, if the heating is stopped, the fraction of each free grain converted is sufficiently high to make the grain easily separable in a

Decomposition and oxidation of pyrite Request PDF

A strong candidate for this signature is pyrite, which starts to decompose at 400-500°C, giving rise to a magnetisation increase at approximately 500°C (Passier et al., 2001;Weaver et al., 2002

Magnetic monitoring of pyrite alteration with temperature

This magnetite persists or can change afterwards to more oxidised iron oxide such as hematite, as observed during cooling in our samples. The oxidation of magnetite de-pends once more on experimental conditions (time of heating) and/or the degree of al-teration of pyrite. The thermomagnetic behaviour of pyrite allows its identification in sediment;

Replacement of magnetite by pyrite under hydrothermal

Qian et al. (2009 Qian et al. (,2010 presented an experimental study on the sulfidation of magnetite to form pyrite/marcasite under hydrothermal conditions (90e300 C, vapor saturated pressures

Magnetic properties related to thermal treatment of pyrite

Jul 16, 2008 In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ∼20 and ∼30 mT, respectively. Whereas in air, the pyrite is ultimately oxidized

Decomposition and oxidation of pyrite Request PDF

Pyrite present in coal undergoes oxidation at elevated temperatures to form iron oxide (hematite), magnetite and sulfur dioxide during heat treatment (Hu et al. 2006; Matjie et al. 2011;Matjie

Replacement of magnetite by pyrite under hydrothermal

Qian et al. (2009 Qian et al. (,2010 presented an experimental study on the sulfidation of magnetite to form pyrite/marcasite under hydrothermal conditions (90e300 C, vapor saturated pressures

Earliest microbially mediated pyrite oxidation in ~ 3.4

Jan 03, 2011 From a biological viewpoint, oxidation of pyrite by extant Fe- and S-oxidising microbes results in precipitation of insoluble Fe-hydroxides that, on geologic timescales, dehydrate to haematite (Fe 2 O 3) or are reduced to magnetite (Fe 3 O 4) (Posth et al., 2008).

Decomposition and oxidation of pyrite ScienceDirect

Jan 01, 2006 The oxidation of pyrrhotite in a molten state was thought to be controlled by the diffusion of oxygen through gas and liquid film in this model, due to the relatively fast oxidation reaction at such high temperatures. ten Brink et al. used a similar model for the transformation of pyrite in a flame environment. It was observed that the

Magnetic properties related to thermal treatment of pyrite

Jul 16, 2008 Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ∼1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite → pyrrhotite → magnetite → hematite.

Magnetic properties related to thermal treatment of pyrite

At temperatures ≥400°C, the magnetization rose sharply which likely indicated the neoformation of iron oxides (e.g., magnetite or pyrrhotite from oxidation of pyrite (e.g., Wang et al., 2008).

Pyrite Oxidation Mechanism by Oxygen in Aqueous Medium

Nov 08, 2015 Pearson19 showed that, in the pyrite oxidation process, a minimum of 7 electron-transfer steps are necessary to describe completely the oxidation on the pyrite surface. Furthermore, it is well-known that different bacteria can catalyze the pyrite oxidation at a much rapid rate, making its mechanism even more complex.20

Geochemistry and iron isotope systematics of coexisting Fe

May 01, 2020 In the case of pyrite, the increased covalence in the Fe S bond results in stronger bonds, despite the lower oxidation state of iron (Blanchard et al., 2009). Therefore, the pyrite could have heavier iron isotopic composition when equilibrating with magnetite or ilmenite.

Pyrite oxidation in shales: Implications for palaeo-redox

Jul 01, 2019 (A) Higher surface area for pyrite oxidation and Fe (oxyhydr)oxide precipitation to take place (Chandra and Gerson, 2010; Heidari et al., 2017); in both BSB.1 and BSB.2, pyrite grains had a smaller average ECD than in QVS.1 and QVS.2; (B) The flow rate of oxygenated water (Heidari et al., 2017), linked to permeability, may also have been higher

Minerals of Alabama Encyclopedia of Alabama

Aug 13, 2007 Pyrite (iron disulfide), known popularly as fool's gold, is a common mineral in the Piedmont and occurs in metamorphic, igneous, and sedimentary rocks. Pyrite deposits in the Hillabee Greenstone geologic formation in the vicinity of Pyriton, Clay County, were first mined in the 1850s by mining companies to produce sulphur acid and elemental sulfur.

Magnetic properties and geochemistry of the active

The present site of active oxidation is at the top of the organic rich layer (van Santvoort et al. 1996). Organic carbon and pyrite are oxidized at this oxidation front. The decrease of C org starts at shallower depth in the cores than the decrease of Fe pyr . This indicates that the depth of oxidation of organic matter is shallower than the

Formation of As(II)-pyrite during experimental replacement

A ‘new’ type of arsenian pyrite was formed during experimental replacement of magnetite under hydrothermal conditions (T = 125 and 220 °C; Psat) and in the presence of S(-II) and various As

micromill steel oxidation of pyrite in coal to magnetite

micromill steel oxidation of pyrite in coal to magnetite. From pyrite heating in n,whereas the residue when heated in co denotes the presence of magnetite it was proposed that co dissociates in co and o after heating to c, so transformation in co involved partial oxidation to magnetite, in accordance with equation fes co g fe o fe o cos g so g

Corrosion and Scaling Deposits in the Berlín Geothermal

Once formed, the magnetite transforms to hematite with the presence of O 2 and pyrite and pyrrhotite with the presence of H 2S. 3.2 Fe-hydroxides: goethite Goethite belongs to the group of iron hydroxide and usually occurs with hematite, pyrite, pyrrhotite and other sulfide minerals. It is mostly a product of surface oxidation of Fe

Magnetic properties related to thermal treatment of pyrite

Jul 16, 2008 Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ∼1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite → pyrrhotite → magnetite → hematite.

Magnetic properties related to thermal treatment of pyrite

Hu et al. [9] pro-posed the decomposition and oxidation processes of pyrite as follows: pyrite→pyrrhotite→troilite→iron for the transformation of pyrite in inert atmospheres. He and his coworkers also concluded that as oxidation products, hematite forms at high temperatures (900-1000℃) with high oxygen concentration, while magnetite

micromill steel oxidation of pyrite in coal to magnetite

micromill steel oxidation of pyrite in coal to magnetite. From pyrite heating in n,whereas the residue when heated in co denotes the presence of magnetite it was proposed that co dissociates in co and o after heating to c, so transformation in co involved partial oxidation to magnetite, in accordance with equation fes co g fe o fe o cos g so g

Magnetic properties and geochemistry of the active

The present site of active oxidation is at the top of the organic rich layer (van Santvoort et al. 1996). Organic carbon and pyrite are oxidized at this oxidation front. The decrease of C org starts at shallower depth in the cores than the decrease of Fe pyr . This indicates that the depth of oxidation of organic matter is shallower than the

(PDF) Earliest microbially-mediated pyrite oxidation in ~3

From a biological viewpoint, oxidation of pyrite by extant Fe-and S-oxidising microbes results in precipitation of insoluble Fe-hydroxides that, on geologic timescales, dehydrate to haematite (Fe 2 O 3 ) or are reduced to magnetite (Fe 3 O 4 ) (Posth et al., 2008).

THERMAL ANALYSIS AND KINETICS OF THE

pyrite oxidation process Peak E a / kJ mole-1 Kissinger Ozawa I63 70 II 70 78 III 253 264 IV 188 203 V106 120 Calculated values of the activation energy for the chalcopyrite-pirite oxidation indicate that all stages of the process occur in the kinetic field. CONCLUSIONS The chalcopyrite-pyrite

Magnetite dissolution, diachronous greigite formation, and

Detailed rock magnetic and electron microscope analyses indicate that the magnetic signature of Neogene marine sediments from the east coast of New Zealand is dominated by the authigenic iron sulphide greigite. The greigite is present as a mixed population of stable single domain and superparamagnetic grains, which is consistent with authigenic growth from solution.

Corrosion and Scaling Deposits in the Berlín Geothermal

Once formed, the magnetite transforms to hematite with the presence of O 2 and pyrite and pyrrhotite with the presence of H 2S. 3.2 Fe-hydroxides: goethite Goethite belongs to the group of iron hydroxide and usually occurs with hematite, pyrite, pyrrhotite and other sulfide minerals. It is mostly a product of surface oxidation of Fe

Minerals of Alabama Encyclopedia of Alabama

Aug 13, 2007 Pyrite (iron disulfide), known popularly as fool's gold, is a common mineral in the Piedmont and occurs in metamorphic, igneous, and sedimentary rocks. Pyrite deposits in the Hillabee Greenstone geologic formation in the vicinity of Pyriton, Clay County, were first mined in the 1850s by mining companies to produce sulphur acid and elemental sulfur.

INVESTIGATING THE OXIDATION PHENOMENA OF

The oxidation fraction or the degree of oxidation orf the magnetite pellets exposed to different isothermal temperatures and different O 2 content in oxidizing gas with respect to time is shown in Fig. 2. The oxidation continuously increases with time under the giventhermal and gaseous atmosphere.

(PDF) In situ high-temperature phase transformation

On the other hand in CO 2,at low enough temperatures, pyrite undergoes thermal decompositions to yield pyrrhotite, though presence of small amounts of oxygen may promote the oxide formation [26].In CO 2,formation of magnetite and smaller amounts of hematite at higher temperatures, as shown in Fig. 4, can be attributed to the instability of

Electrical Properties of Magnetite- and Hematite-Rich

magnetite), the ilmenohematite (ilmentite–hematite) series and the pseudobrookite series (Figure 1) (Carmichael, 1989). SUMMARY Magnetite and hematite are common iron-oxides, being found in sedimentary, metamorphic and igneous environments and being associated with a wide variety of deposits styles, including orogenic gold, iron-oxide

Pyrite Wikipedia

Pyrite oxidation is sufficiently exothermic that underground coal mines in high-sulfur coal seams have occasionally had serious problems with spontaneous combustion. The solution is the use of buffer blasting and the use of various sealing or cladding agents

MECHANISMS OF PYRITE OXIDATION TO NON-SLAGGING

Pyrite (FeS 2) is transformed to troilite (FeS), which is oxidized to wusite (FeO). The troilite-to-wusite transformation involves oxidation of an oxysulfide melt (Fe-S-O) melt to an iron-oxide melt (Fe-O) melt. Magnetite (Fe 3 O 4, really, FeO·Fe 2O 3) crystallizes from the oxide melt after complete melt oxidation.