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See detailMinéralogie et propriétés physico-chimiques des smectites de Bana et Sabga (Cameroun). Utilisation dans la décoloration d'une huile végétale alimentaire
Mache, Jacques Richard ULg

Doctoral thesis (2013)

In this study, clay samples were collected in the localities of Bana and Sabga, in the regions of the west and north-west Cameroon, respectively. The purpose of this study was to determine their ... [more ▼]

In this study, clay samples were collected in the localities of Bana and Sabga, in the regions of the west and north-west Cameroon, respectively. The purpose of this study was to determine their mineralogical composition, their physico-chemical properties and to assess their potential use in the bleaching process of palm oil, which is the main edible vegetable oil produced and refined in Cameroon. <br /> The results obtained from the analyses (XRD, FTIR, DTA / TGA and SEM) revealed that montmorillonite is the main clay mineral in these materials. It is associated with kaolinite and mica. Non-clay minerals such as quartz, anatase, cristobalite, K-feldspar and heulandite are also identified in variable quantities. Chemical analyses of the major elements show that the clays from Bana and Sabga consist mainly of the follow oxides such as SiO2, Al2O3 and Fe2O3. Bana clays have a cation exchange capacity (CEC) between 50 and 60 meq/100 g and a specific surface area between 50 and 60 m2/ g. Sabga clays have a lower capacity cation exchange (38- 46 meq/100 g) and a wider range of specific surface area (33-90 m2 / g). The characterization of the natural clays allowed to select of one sample by locality for sulfuric acid treatment. <br />The acid treatment of these materials led to structural, morphological and textural changes. Analysis by X-ray diffraction showed a progressive decrease in the intensity of the (001) reflection of montmorillonite and a shift of its basal d001-value. Treatment with more acid concentration causes an increase in the surface area of the obtained products and a decrease in cation exchange capacity. <br />The assessment of the bleaching power of natural and acid-activated Bana clay in palm oil decolorization shows that the activated clay has a high bleaching capacity (~ 87%) compared to the natural clay (~ 55%). palm oil Bleaching by these clay materials does not deteriorate the bleached oil. These materials can thus be used as bleaching earths in the refining oil process. [less ▲]

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See detailMineralogy and crystal chemistry of natural and synthetic uranyl oxysalts
Dal Bo, Fabrice ULg

Doctoral thesis (2016)

Since 1960, the number of described uranyl mineral species has been multiplied by three. To date more than 200 mineral species containing uranium as a main structural element are reported in Nature, and ... [more ▼]

Since 1960, the number of described uranyl mineral species has been multiplied by three. To date more than 200 mineral species containing uranium as a main structural element are reported in Nature, and the crystal structures have been determined and refined for only one third of them. Furthermore, many new uranyl minerals are still reported to data, showing sometimes novel chemical compositions and structural arrangements. The uranium mineralogy is a fascinating subject, and an essential field of research as it contributes to the improvement of the management techniques of nuclear waste. The first part of this work was dedicated to the mineralogical characterisation of uranyl minerals, and especially of the autunite-type minerals, occurring in the Rabejac deposit. Indeed, the identification analyses have shown that many samples contain uranyl arsenates of the autunite and meta-autunite groups. Electron-microprobe chemical analyses performed on these minerals species indicate that the P content in (meta-)zeunerite and (meta-)uranospinite is significant in several samples, confirming the solid-solution series between uranyl arsenates and phosphates. Also, cationic substitutions occurring on the A site were observed, especially in uranospinite samples, in which significant amount of Ca is substituted for Mg. Single-crystal X-ray diffraction experiments have been performed on many members of the (meta-)zeunerite-(meta-)torbernite series, and the crystallographic parameters were put into correlation with the variation of the chemical composition. The crystal structure of arsenuranospathite, the Asanalogue of the Al-bearing uranyl phosphate uranospathite, was solved for the first time, indicating that these two minerals are isostructural (Dal Bo et al., 2015). Also, a structure model is proposed for metauranocircite-I, one of the Ba-bearing uranyl phosphate of the meta-autunite group. Investigations of uranyl mineral samples from other localities have allowed to discover single-crystals of bassetite, one of the Fe end-members of the autunite group. The crystal structure of bassetite was also solved for the first time, and these new structural data were presented in parallel to those obtained on saléeite, the Mg-analogue of bassetite (Dal Bo et al., 2016). Thanks to these new data, a discussion about the mineral hierarchy of the (meta-)autunite group is proposed. In addition, the crystal structure of the rare Al-bearing uranyl phosphate furongite from the Kobokobo pegmatite was determined, showing that this mineral species has unique and novel structural features. This specific study, as well as the redefinition of the structural formula of phuralumite, was the occasion to provide a review about the formation of Al polyhedra clusters in uranyl minerals, and to try to elucidate their physicochemical conditions of crystallisation. Many new crystallographic data were also collected on uranyl minerals for which the crystal structure was already reported in the literature. Therefore, it was possible to confirm the previous studies, or to highlight important discrepancies, especially in the case of the Al-bearing uranyl phosphate phuralumite. The H-bonds networks, which are essential for the stability of the structure, have been established in the structure of the uranyl carbonate liebigite, and in the structure of the uranyl silicates cuprosklodowskite, kasolite and soddyite. The second part of this work was devoted to the hydrothermal synthesis of uranyl oxysalts. The experimental conditions, as well as the chemical systems, were chosen in agreement with the conditions occurring in natural uranium deposits, or in geological repositories. A new compound, Be[(UO2)(PO4)]2(H2O)2.5, has been synthesized at low temperature. This is the third Be-bearing uranyl phosphate reported to date, and its crystal structure is based upon sheets showing the uranophane anion topology, typical of uranyl silicates occurring in the oxidation zone of the uranium deposits. The well-known Ba[(UO2)3(MoO4)4(H2O)](H2O)3 and (NH4)2[(UO2)(MoO4)2](H2O) compounds have been synthesized, and new crystallographic data were collected on them. In addition, it was possible to determine the hydrogen-bonds networks for the first compound, and to redefine the Mo6+ coordination polyhedra in the second one. [less ▲]

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See detailMineralogy and petrography of phosphate minerals from pegmatites of the Conselheiro Pena district, Minas Gerais, Brazil
Baijot, Maxime ULg; Hatert, Frédéric ULg; Philippo, Simon

in Acta Mineralogica-Petrographica, Abstract series (2010), 6

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See detailMineralogy and petrography of phosphate minerals from Sapucaia and Boca Rica pegmatites, Minas Gerais, Brazil
Baijot, Maxime ULg; Hatert, Frédéric ULg; Philippo, Simon et al

in Estudios Geologicos (2009), 19(2), 47-51

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See detailMineralogy and physico-chemical properties of alluvial clays from
Nzeugang Nzeukou; Fagel, Nathalie ULg; Njoya, André et al

in Applied Clay Science (2013), 83-84

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See detailMineralogy and physico-chemical properties of alluvial clays from Sanaga valley (Center, Cameroon): Suitability for ceramic application,
Nzeukou, Aubin; Fagel, Nathalie ULg; Njoya, André et al

in Applied Clay Science (2013), (83-84), 238-243

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See detailMineralogy of fine particles in slurry from multispectral imaging
Leroy, Sophie ULg; Dislaire, Godefroid ULg; Barnabé, Pierre ULg et al

Conference (2014, September 02)

Quantitative mineralogy of fine particles in slurry from multispectral imaging Sophie Leroy, Godefroid Dislaire, Pierre Barnabé and Eric Pirard Mineral processing especially in its final stages relies ... [more ▼]

Quantitative mineralogy of fine particles in slurry from multispectral imaging Sophie Leroy, Godefroid Dislaire, Pierre Barnabé and Eric Pirard Mineral processing especially in its final stages relies heavily on the differential behavior of particles in pulps. In order to monitor hydrocyclones and flotation cells in almost real time, it is important to develop at line particle characterization providing information on particle distribution but also mineralogy. A sampling device has been elaborated based on a flow cell with variable wall spacing linked to a high pressure peristaltic pump. This setup allows for dispersion and dilution of the mineral slurry into the cell. Depending on the ore or gangue minerals to be controlled, particles can be imaged either in diffuse reflectance or in transmittance mode. A simple multispectral imaging module has been designed to acquire images at eight different wavelengths. The design is based on a series of dichroic filters thereby avoiding any moving part and enabling a very fast acquisition of multispectral images. Imaging artifacts due, among others, to specular reflectance from the glass window are minimized. Multispectral classification is used to outline particles appearing in the field of view and to qualify their main mineral component. In particular, areas reflecting a meaningful and discriminative spectrum are identified and compared to a multispectral database. The database is continuously enriched through testing of pure mineral particles under similar pulp conditions (dilution, grain size,…). Results of final classification are compared to the modal analysis obtained from polished blocks and conventional reflected light microscopy. The technology developed in this work sets the basis for at line monitoring of ore slurries with reasonably simple mineralogy. Extension of the spectral range is being considered for future developments. [less ▲]

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See detailMinerals and trace elements in traditional foods of rural areas of Lhasa Prefecture, Tibet Autonomous Region (P.R. China)
DERMIENCE, Michael ULg; Li, Xiao Wei; Mathieu, Françoise et al

in Journal of Food Composition and Analysis (2014), 35(2),

Traditional foods play a major role in the diet of rural people living in the Tibet Autonomous Region of the People's Republic of China. Because these foods are mainly derived from local agriculture as ... [more ▼]

Traditional foods play a major role in the diet of rural people living in the Tibet Autonomous Region of the People's Republic of China. Because these foods are mainly derived from local agriculture as well as artisanal production, their mineral composition may show significant discrepancies when compared with food composition data. This study aims at providing relevant data on the mineral composition of the main Tibetan foods. Sixteen different foodstuffs were sampled, including water, concentrated brewed black tea, chang, tsampa, wheat flour, dried cheese, dried yak meat, dried mutton, blood sausage, dried wild peaches, dried Chinese radish, and dried nettles. They were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) for 19 minerals: Na, K, P, Ca, Mg, Fe, Zn, Mn, Cu, Ni, Se, Mo, Al, As, Cr, Co, Cd, Pb, and V. The validity of the results was ensured by the use of standard reference materials. A statistical comparison of the mean mineral contents of the analyzed foods against food composition data from the China Food Composition (CFC) table was carried out. It revealed significant discrepancies, emphasizing the importance of food analysis for nutritional assessment in Tibet autonomous region. To the best of our knowledge, the mineral compositions of some traditional Tibetan foods are here reported for the first time. [less ▲]

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See detailMinerals discovered in paleolithic black pigments by transmission electron microscopy and micro-X-ray absorption near-edge structure
Chalmin, Emilie; Vignaud; Salomon, Hélène ULg et al

in Applied Physics A : Materials Science & Processing (2006)

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See detailLes minéraux de Belgique
Hatert, Frédéric ULg; Deliens, Michel; Fransolet, André-Mathieu ULg et al

Book - Museum des Sciences Naturelles (2002)

Detailed reference viewed: 40 (4 ULg)
See detailLes minéraux de la région de Bastogne: observations nouvelles
Hatert, Frédéric ULg

Conference (2000)

Detailed reference viewed: 22 (4 ULg)
See detailLes minéraux et vitamines chez la vache laitière
Beckers, Yves ULg

Conference given outside the academic context (2002)

Detailed reference viewed: 8 (0 ULg)
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See detailLes minéraux secondaires en relation avec les sulfures de la région de Vielsalm, Belgique
Hatert, Frédéric ULg; Blondieau, Michel; Dehove, José et al

in Bulletin de la Société Royale des Sciences de Liège (1998), 67

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See detailMines as lower reservoir of an UPSH (Underground Pumped Storage Hydroelectricity): groundwater impacts and feasibility
Bodeux, Sarah ULg; Pujades, Estanislao ULg; Orban, Philippe ULg et al

Poster (2016, April 20)

The energy framework is currently characterized by an expanding use of renewable sources. However, their inter- mittence could not afford a stable production according to the energy demand. Pumped Storage ... [more ▼]

The energy framework is currently characterized by an expanding use of renewable sources. However, their inter- mittence could not afford a stable production according to the energy demand. Pumped Storage Hydroelectricity (PSH) is an efficient possibility to store and release electricity according to the demand needs. Because of the topographic and environmental constraints of classical PSH, new potential suitable sites are rare in countries whose topography is weak or with a high population density. Nevertheless, an innovative alternative is to construct Underground Pumped Storage Hydroelectricity (UPSH) plants by using old underground mine works as lower reservoir. In that configuration, large amount of pumped or injected water in the underground cavities would impact the groundwater system. A representative UPSH facility is used to numerically determine the interactions with surrounding aquifers Different scenarios with varying parameters (hydrogeological and lower reservoir char- acteristics, boundaries conditions and pumping/injection time-sequence) are computed. Analysis of the computed piezometric heads around the reservoir allows assessing the magnitude of aquifer response and the required time to achieve a mean pseudo-steady state under cyclic solicitations. The efficiency of the plant is also evaluated taking the leakage into the cavity into account. Combining these two outcomes, some criterions are identified to assess the feasibility of this type of projects within potential old mine sites from a hydrogeological point of view. [less ▲]

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