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Walter, Dirk; Buxbaum, Gunter; Laqua, W.

doi:10.1023/a:1010187921227

Cited by 151 publications

(83 citation statements)

References 21 publications

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“…At 275 °C, the ore was undergoing dehydration or decomposition of goethite to become hematite. This corresponds to previous study 4 that reports the dehydration of goethite to hematite occurs at temperature range from 274 °C to 305 °C. At 550 °C, the ore were also undergoing an endothermic reaction which known as dehydroxylation of serpentine.…”

Section: Resultssupporting

confidence: 92%

Extraction of nickel from nickel limonite ore using dissolved gaseous SO2 – air

Wulandari¹,

Soerawidjaja²,

Joshua³

et al. 2017

AIP Conference Proceedings

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Section: Resultssupporting

confidence: 92%

Extraction of nickel from nickel limonite ore using dissolved gaseous SO2 – air

Wulandari¹,

Soerawidjaja²,

Joshua³

et al. 2017

AIP Conference Proceedings

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“…This decrease in mass is associated with the removal of residual water and with goethite dehydroxylation, which starts at about 200°C. [33][34][35][36][37][38] This result is confirmed by XRD analysis reported in Table 2, where the presence of goethite is indicated at 25°C while this phase is no longer detected at 310 and 390°C. In addition, the decrease in mass is greater in the pellets due to dehydration of bentonite, which is added during its fabrication, as shown in Fig.…”

Section: Figures 3(a)-3(c)supporting

confidence: 74%

Induration Process of Pellets Prepared from Mixed Magnetite–35% Hematite Concentrates

et al. 2014

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To explore the possibility of successfully processing iron ore pellets with a high content of hematite, thermogravimetric tests were performed to study the induration process of pellets composed of a mixture of iron ore concentrates (magnetite and 35% wt of hematite). Thermogravimetric tests were performed nonisothermally from 25°C to 1 400°C using two heating rates, 5 and 50°C/min. To identify the reactions involved and to follow the microstructural evolution throughout the induration process, selected tests were arrested at predetermined temperatures, and samples were rapidly cooled to room temperature for later characterization using X-ray diffraction (XRD) and scanning electron microscopy (SEM) along with energy dispersive spectroscopy (EDS). It was found that the formation of phases such as calcium ferrite (CF), magnesium ferrite (MF), silico-ferrites of calcium (SCF) and silico-ferrites of calcium and aluminum (SCFA) are influenced by the heating rate. The microstructure of the fired pellet processed at 50°C/min showed compact small grains of the sintered phase of the secondary hematite (SH), partially surrounded by a slag phase. In contrast, the fired pellet processed at 5°C/min exhibited a microstructure consisting of the SH phase with a faceted morphology surrounded by a relatively large amount of the slag phase. The results suggest that the pellet processed at 50°C/min had a more satisfactory response to the induration process.

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“…7,29,30) However, Schwertmann 20) did not agree with this interpretation and proposed the existence of two different types of goethite to explain the double peak. We believe that the formation of a hematite coating indeed requires a higher temperature to complete the reaction.…”

Section: Mössbauer Experimentsmentioning

confidence: 98%

“…Similar curves have been reported by several authors. [6][7][8][9] The interpretation of these curves is at first sight rather simple: the initial loss of mass up to 100°C is due to moisture, whereas the major loss of mass near 250°C (GD) and 310°C (KE01 and KE07) is due to the decomposition of goethite. The different decomposition temperatures are related to the origin of the goethites present in these samples.…”

Section: Introductionmentioning

confidence: 99%

“…-The first region up to about 150°C is named moisture, hydroscopic moisture, surface water, onset of bulk and surface dehydration, non-stoichiometric hydroxyl units (excess water), surface adsorbed water, chemisorbed surface water and adsorbed water; 2,7,8,10,[12][13][14][15] -The second region goes up to about 200-230°C, depending on the sample characteristics (particle size, morphology, synthetic or natural, etc.) and is named as bulk dehydration and surface dehydration/dehydroxylation, nonstoichiometric water from bulk and surface, weakly bound OH groups, surface-bound and bulk-sequestered water, loosely bound hydroxyl units, dehydration from hydrogenbonded water or dehydroxylation of surface; 6,[14][15][16][17] -The third region comprises the transformation of goethite into hematite, which is completed below 400°C.…”

Section: Introductionmentioning

confidence: 99%

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Quantification of Moisture Contents in Iron and Manganese Ores

et al. 2013

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The moisture contents of several synthetic and natural goethite-bearing samples were determined by the loss-of-mass method and by the Karl-Fischer titration. It was found that drying at 105°C did not remove all the water from these samples, and that temperatures above 200°C would be required to completely remove the adsorbed water. The multiple peaks observed in the TGA and DSC measurements are not due to the dehydroxylation of goethite, but are due to the release of adsorbed water. The decomposition of goethite into hematite occurs with the release of adsorbed water from room temperature up to the onset of the main dehydroxylation peak. The dehydroxylation occurs in a broad range of temperatures due to the existence of a particle-size distribution, surface hydroxyls and formation of a hematite coating. The determination of all adsorbed water is best performed by adding the powdered sample into the KarlFischer reaction vessel.

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Cited by 151 publications

References 21 publications

Extraction of nickel from nickel limonite ore using dissolved gaseous SO2 – air

Extraction of nickel from nickel limonite ore using dissolved gaseous SO2 – air

Induration Process of Pellets Prepared from Mixed Magnetite–35% Hematite Concentrates

Quantification of Moisture Contents in Iron and Manganese Ores

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