Raman spectroscopy as a tool to characterize heterogenite (CoO·OH) (Katanga Province, Democratic Republic of Congo)

Burlet, Christian; Vanbrabant, Yves; Goethals, Herman; Thys, Tom; Dupin, L.

doi:10.1016/j.saa.2011.03.007

Cited by 19 publications

(16 citation statements)

References 21 publications

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“…Anyway, the intense light absorption of the black material promotes the transformation of (hydroxylated) CoO into Co 3 O 4 under the laser beam. The observation of a band at $ 1140 cm À 1 is also consistent with hydroxylated CoO [44]. Traces of metal transition oxides are commonly observed in similar compounds [46].…”

Section: Raman Scatteringsupporting

confidence: 69%

“…A reference spectrum given in Fig. 3 has been obtained by heating of CoOOH heterogenite [44]. The small wavenumber shift and relative intensity change arise from the (pre)resonance Raman effect [45].…”

Section: Raman Scatteringmentioning

confidence: 99%

“…Raman signatures of as-prepared LSCF6428 ceramic at different surface area/laser power/wavelengths and of Co 3 O 4 obtained by thermal treatment of CoOOH[44]. (*corresponds to Co 3 O 4 traces).…”

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confidence: 99%

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Chemical and structural stability of La0.6Sr0.4Co0.2Fe0.8O3− ceramic vs. medium/high water vapor pressure

Upasen

Batocchi

Mauvy

et al. 2015

Ceramics International

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During the last decades, perovskite-type oxides have received large attention as potential electrolytes and electrodes for Solid Oxide Fuel Cells (SOFC), including Proton Ceramic Fuel Cells (PCFC), gas separation membranes and High Temperature Steam Electrolysers (HTSE). A thermal treatment in an autoclave, at a temperature close to an operating temperature, was used to measure the chemical stability of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 À δ (LSCF6428) ceramic under medium and high water pressure ( $20 and 40 bar). This mixed ionicÀ electronic conductor (MIEC) exhibits interesting properties as cathode of fuel cell materials. The reactivity rate of the investigated LSCF6428 sample under the protonation process conditions (several weeks at 550 1C using CO 2 -free and CO 2 -saturated water) was studied in order to evaluate a potential use of this compound. Bulk and surface structural/chemical changes were characterized by optical microscopy, TGA, dilatometry, Raman and ATR-FTIR spectroscopy. The results revealed only minor surface modifications in the case of ceramic treated under medium vapor pressure (20 bar) using CO 2 -free water. On the contrary, under higher pressure (40 bar) and CO 2 -saturated water several second phases were detected, namely strontianite, cobalt oxides and hematite. The chemical/structural stability of LSCF6428 is compared with previously investigated RareEarth nickelate ceramics: La 2 NiO 4 þ δ / Pr 2 NiO 4 þ δ / Nd 2 NiO 4 þ δ .

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Section: Raman Scatteringsupporting

confidence: 69%

Section: Raman Scatteringmentioning

confidence: 99%

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Chemical and structural stability of La0.6Sr0.4Co0.2Fe0.8O3− ceramic vs. medium/high water vapor pressure

Upasen

Batocchi

Mauvy

et al. 2015

Ceramics International

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“…Manganite, asbolane and lithiophorite are actually commonly encountered in the Co oxidized ore, even within a single specimen. Heterogenite is also commonly amorphous or poorlycrystalline, with size below micrometer (Burlet et al, 2011 (Figure 10). Consequently, the weathering process has resulted in the mobilization and redistribution of the REE affected by the nature of secondary mineral formation (e.g., Mn oxi-hydroxides).…”

Section: Supergene Formation Of Heterogenite and Ree Competition Withmentioning

confidence: 99%

“…Heterogenite (CoOOH) is the most abundant cobalt oxide in the Copperbelt. Previous works on the Katanga heterogenite (Hey, 1962;Deliens, 1974;Deliens and Goethals, 1973;Gauthier and Deliens, 1999;Burlet et al, 2011;Vanbrabant, 2013) distinguished two subtypes of heterogenite: (i) rhombohedral heterogenite 3R is the most abundant variety (Deliens, 1974), and (ii) heterogenite 2H, which is a hexagonal polytype defined by Deliens and Goethals (1973). Recent Raman microspectroscopy analyses coupled with electron backscattered diffraction (EBSD), however have shown that heterogenite is commonly poorly crystallized Burlet et al (2011).…”

mentioning

confidence: 99%

Rare earth element fractionation in heterogenite (CoOOH): implication for cobalt oxidized ore in the Katanga Copperbelt (Democratic Republic of Congo)

Decrée

Pourret

Baele

2015

Journal of Geochemical Exploration

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Heterogenite (CoOOH) is the most abundant cobalt oxide mineral in the Katanga Copperbelt, which hosts around half of the world's known reserves of mineable cobalt. Heterogenite formed by the oxidation of Co-sulfides and accumulated as residual deposits during a Pliocene weathering event. Bulk analysis samples of oxidized cobalt ore samples containing with variable heterogenite concentration display two rare earth element (REE) patterns: (i) Type 1 is enriched in middle REE, with a negative cerium anomaly and a relatively low REE content; (ii) Type 2 is variably enriched in light REE (LREE), without a cerium anomaly and *Revised Manuscript with No Changes Marked Click here to view linked References with higher REE content. However, in situ LA-ICP-MS reveals that the Type patterns are due to the mixing of heterogenite with a LREE-rich mineral. Weathering processes leading to heterogenite formation mainly consist of water-rock interactions at high Co activity, in the near-surface environment. These result in the formation of a lateritic deposit. Heterogenite precipitates at near-neutral pH conditions together with manganese oxides. REE are mainly fractionated between these Co-and Mn-oxide minerals. In the deeper part of the oxidized profile, cobalt activity decreases and the heterogenite stability field shifts to alkaline pH conditions due to the dissolution of dolostone in the bedrock. In such an alkaline environment, REE speciation is mainly driven by carbonate complexation/precipitation. This environment would be favorable for the formation of REErich carbonate which is intimately associated with heterogenite (LREE-rich Type 2 patterns). The combined whole-rock and in situ geochemical analyses presented here clearly help (1) to distinguish the REE signature of the Co oxidized ore (mineral paragenesis comprizing heterogenite) and of heterogenite itself, and subsequently (2) to highlight two different chemical environments for the formation of heterogenite in supergene ores. This study therefore improves the understanding of REE behaviour and metal mobility in nearsurface environments, and more particularly in environments where the supergene ores form. In the future, the approach developped here can be applied to other Co-Ni-Mn lateritic deposits such as those in New-Caledonia and Cameroon.

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Mineralogical Characterization of Cobaltic Oxides from the Democratic Republic of Congo

2013

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Raman spectroscopy as a tool to characterize heterogenite (CoO·OH) (Katanga Province, Democratic Republic of Congo)

Cited by 19 publications

References 21 publications

Chemical and structural stability of La0.6Sr0.4Co0.2Fe0.8O3− ceramic vs. medium/high water vapor pressure

Chemical and structural stability of La0.6Sr0.4Co0.2Fe0.8O3− ceramic vs. medium/high water vapor pressure

Rare earth element fractionation in heterogenite (CoOOH): implication for cobalt oxidized ore in the Katanga Copperbelt (Democratic Republic of Congo)

Mineralogical Characterization of Cobaltic Oxides from the Democratic Republic of Congo

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