Manganese and cobalt redox cycling in laterites; Biogeochemical and bioprocessing implications

This research was developed during the PhD studies of Agustín Solano Arguedas in the University of Manchester, United Kingdom. PhD scholarship was funded by the Ministerio de Ciencia, Tecnología y Telecomunicaciones (MICITT) of the Government of Costa Rica and the Universidad de Costa Rica (UCR). Agustín Solano Arguedas is a researcher at the Unidad de Recursos Forestales (Reforesta, Unit of Forest Resources) of the Instituto de Investigaciones en Ingeniería (INII, Engineering Research Institute), UCR.Cobalt is essential for the modern technology that underpins the decarbonisation of our economies, but its supply is limited leading to its designation as a critical metal. Cobalt biogeochemistry is poorly understood, yet knowledge of how biogeochemical cycling impacts cobalt behaviour could assist the development of new techniques to recover cobalt from ores, and so improve the security of supply. Laterites are an important source of cobalt, they are primarily processed for nickel using energy or chemical intensive processes, with cobalt recovered as a by-product. Metal-reducing conditions were stimulated in laterite sediment microcosms by the addition of simple and cheaply available organic substrates (acetate or glucose). At the end of the experiment the amount of easily recoverable cobalt (aqueous or extractable with acetic acid) increased from < 1% to up to 64%, which closely mirrored the behaviour of manganese, while only a small proportion of iron was transformed into an easily recoverable phase. Sequencing of the microbial community showed that the addition of organic substrates stimulated the growth of indigenous prokaryotes closely related to known manganese(IV)/iron(III)-reducers, particularly from the Clostridiales, and that fungi assigned to Penicillium, known to produce organic acids beneficial for leaching cobalt and nickel from laterites, were identified. Overall, the results indicate that the environmental behaviour of cobalt in laterites is likely to be controlled by manganese biogeochemical cycling by microorganisms. These results are compelling given that similar behaviour was observed in four laterites (Acoje, Çaldağ, Piauí and Shevchenko) from different continents. A new bioprocessing strategy is proposed whereby laterites are treated with an organic substrate to generate metal-reducing conditions, then rinsed with acetic acid to remove the cobalt. Not only are organic substrates environmentally-friendly and potentially sourced from waste carbon substrates, a minimal amount of iron oxides was mobilised and consequently less waste generated.Natural Environment Research Council/[CoG3 NE/M011518/1]/NERC/Reino UnidoDiamond Light Source/[SP16735]//Reino UnidoDiamond Light Source/[SP17313]//Reino UnidoOffice of Science User Facility/[DE-AC02-05CH11231]//Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ingeniería::Instituto Investigaciones en Ingeniería (INII

Erodibility of Cultivated Soils in the Foumbot Area (West Cameroon)

Agricultural lands in Western highlands of Cameroon are likely to face severe erosion because of the interactions of the following factors: high intensity of agricultural activities, poor farming practices and high rainfall intensity. However, the severity of this soil erosion can vary significantly with the ease with which soil is detached and transported by erosion agents. That is why a study was carried out in the Foumbot area in order to evaluate the soil erosion risk variation with some soil types. Thirty one soil samples were collected at 0–20 cm depth from three main soil types encountered in the area (Andosols, Acrisols and Ferralsols). Soil samples were analyzed for particle size distribution (Total clay, Total silt, Water dispersible clay, Water dispersible silt), Soil organic matter, Soil reaction, CEC, Exchangeable bases, clay dispersion ratio, dispersion ratio, clay aggregation and Mean weight diameter). Soil erodibility indicators were determined and used to estimate soil erosion risk for the three soil types. The results showed high dispersive potential of the three soil types. Soil characteristics and the deriving soil erodibility vary from one soil type to another. The most vulnerable soils are the Acrisols and the less erodible are the Andosols. Soil mineralogy seems to be the key factor regulating soil erodibility variation in the area. The Water-Dispersible Silt (WDS) correlates positively with the Soil organic matter (r=+0.67, p=0.000). The Water-Dispersible Clay (WDC) significantly correlates negatively with the soil organic matter (r=-0.61, p=0.000). WDC also showed significant negative correlation with calcium (r=-0.67, p=0.016) and potassium (r=-0.74, p=0.000). Based on its strong correlation with erodibility parameters, soil organic matter content appeared as the main soil characteristic through which soil conservation measures could easily be implemented in the studied area

Study of physical and mechanical applications on ceramics of the lateritic and alluvial clayey mixtures of the Yaoundé region (Cameroon)

International audienceCeramic products were prepared by mixing lateritic and alluvial clayey materials of Yaoundé (Cameroon) in the humid tropical region, with 20, 50 and 80 wt.% of alluvial clay respectively in lateritic clay. Samples were grounded and sieved and powders obtained were shaped by uniaxial pressing of wet granules and fired under low temperatures between 350 and 1050 °C. Open porosity, bulk density and flexural strength were the principal properties characterised. Results indicates that a maximum of 80 wt.% of alluvial clayey material must be added to lateritic clays of Yaoundé, to obtain weakly porous ceramics and to attain the bulk density ranging from 1.56 to 1.97 g/m3 and a flexural strength of 6–19.85 MPa would be equivalent alluvial clay ceramics. But ceramics with lesser amount of alluvial clayey materials also have interesting flexural strengths in the range of 5–16 MPa, thus higher than porous lateritic clay ceramics

Ceramic with potential application of ngwenfon alluvial clays (noun, west cameroon) in building construction: Mineralogy, physicochemical composition and thermal behaviour

Our aim is to characterize four types of alluvial clays from the locality of Ngwenfon situated 35 km from Foumban (West Cameroon). X-ray diffraction, thermal analysis, chemical composition, particle size distribution, organic matter content and plasticity were investigated in raw clay materials in order to determine their suitability for building material and firing bricks in particular. Ceramics properties such as linear shrinkage, water absorption, flexural strength, compressive strength, bulk density and mineral neoformations were also investigated by firing specimen bricks at a temperature range of 800 °C–1150 °C. Kaolinite, quartz, goethite, feldspar and illite represent the dominant mineral phases, in addition to minor quantities of chlorite, gibbsite, anatase and plagioclase. The main oxides are; SiO2, Al2O3, and Fe2O3. The physical parameters of the alluvial clays display a continuous and various particles size with a relatively high plastic index (12%–36%) and high organic matter contents (9%–13%). A significant densification has been observed at a temperature of 1150 °C. This was confirmed by the appearance of new mineral phases such as mullite, cristobalite and spinel, which are responsible for the increased mechanical strength and a reduction in water absorption. Most of the alluvial clays from Ngwenfon display suitable ceramic properties at sintering range from 1000 °C to 1150 °C. However, the black clays, with low ceramic properties at temperatures of 1150 °C, are inappropriate for fired brick production. These black clays are characterized by a compressive strength lower than the required value of 20 MPa for the standard reference. © 2018 Elsevier LtdCharacterisation et valorisation des argiles de Foumban (Ouest Cameroun

Geochemistry of the Paleocene-Eocene and Miocene-Pliocene clayey materials of the eastern part of the Wouri River (Douala sub-basin, Cameroon) : influence of parent rocks

Major and trace element concentrations of clay deposits of the Missole II and Bomkoul respectively from the Paleocene-Eocene N'Kapa Formation and the Miocene-Pliocene-Matanda-Wouri Formation in the eastern part of the Wouri River in the Douala sub-basin of Cameroon have been investigated to identify the parent rocks. To carry out this study, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry (ICP/AES) and inductively coupled plasma-mass spectrometry (ICP/MS) were performed to determine respectively the mineralogical and chemical data of Missole II and Bomkoul clayey materials. Clay sediments are essentially kaolinitic and illitic, and kaolinitic and smectitic respectively in both sites. They are generally siliceous, aluminous with small iron and bases (MgO, CaO, Na2O, and K2O) contents. Samples of Missole II profiles are more siliceous than those from the Bomkoul grey and dark grey clayey materials. Clayey materials have high Chemical Index of Alteration (CIA = 80-99.34) which suggests that they are strongly weathered under humid tropical climate before and after their deposition in the coastal plain. The value of Eu/Eu* (0.48-0.61), La/Sc (2.15-20.50), Th/Sc (0.74-2.25), Th/Co (1.08-8.33), and Cr/Th (5.24-13.55) ratios support essentially a silicic or felsic parent rocks. Total REE concentrations reflect the variations in their grain-size fractions. Chondrite-normalised REE patterns with LREE enrichment, flat HREE, and negative Eu anomaly are attributed essentially to silicic or felsic parent rocks like those from weathered materials developed from the gneisses around the coastal plain in the littoral part of Cameroon (Noa Tang et al., 2012), main characteristic of Paleocene-Eocene and Miocene-Pliocene clay sediments of Missole II and Bomkoul areas

Geological study of sedimentary clayey materials of the Bomkoul area in the Douala region (Douala sub-basin, Cameroon) for the ceramic industry

A geological study carried out in the Bomkoul area (Douala sub-basin, Cameroon) has revealed the presence of heterogeneous clayey materials on hills (80-120 m altitude). The clay deposits are thick at the upper slope where sandstones and sandy-clay overlying clay layers, and thin at the middle and lower slopes where weathered clays overlying clay layers. Clayey materials identified are grey, dark-grey and mottled in color, with sandy-clay, clayey-silt, silty-clay and clay textures. Raw materials are mostly made up of fine particles ranging from 52 to 82% clay and silt in the mottled clayey material, 50 to 82% clay and silt in the dark-grey clayey material and 70 to 85% in the grey clayey material. Their chemical composition is characterized by silica (<70% SiO2), alumina (<32% Al2O3) and iron (1 to 16% Fe2O3). The main clay minerals are disorganized and poorly crystallized kaolinite and few smectite. The physical, mineralogical and geochemical properties of these materials presented and discussed in this work show that the clayey raw materials of the Bomkoul area have a good potential for pottery as well as brick, tile and soil sandstone manufacture

Occurences of kaolin in Koutaba (west Cameroon): Mineralogical and physicochemical characterization for use in ceramic products

peer reviewedaudience: researcherThirty clay samples collected from three hills in Koutaba (west Cameroon) were characterized in order to evaluate their potential use as raw materials for ceramics. After preliminary mineralogical identification by X-ray diffraction, three representative samples from the three different hills, referred to hereafter as K1M, K2M and K3M, were selected for further investigation by X-ray fluorescence, plasticity, granularity and thermogravimetric analysis. The main clay minerals are kaolinite (32–51%) and illite (up to 12%). Additional major phases are quartz (32–52%), goethite (6–7%) and feldspars (0–4%). The chemical composition showed variable amounts of SiO2 (60–72%), Al2O3(15–20%) and Fe2O3 (1–9%), in accordance with the quartz abundance in all of the samples studied. The particle-size distribution showed a large proportion of silty fraction (64–88%) with moderate sandy (9–19%) and clayey fractions ( < 5% for K2M, 12% for K1M and 20% for K3M). All of the clays showed moderate plasticity-index values (8–11%). Because of these characteristics, K1M and K3M may be suitable for use in common bricks and hollow ceramic products. Sieving or the addition of ball clays is recommended to increase the plasticity of sample K2M for use in common bricks