Jean Aime MBEY

Eco-Friendly Activating Solutions from Cocoa Pod Ash and Rice Husk Ash for Geopolymerization

Cyprien Joël Ekani, Paul Venyité, Jean Marie Kepdieu, Chantale Njiomou Djangang, Philippe Blanchart, Jean Aimé Mbey

Silicon

• #concrete and cement materials research
• #clay minerals and soil interactions
• #microbial applications in construction materials
• #geopolymer

Synthesis of an exfoliated kaolinite–poly(urea–formaldehyde) nanocomposite

Hervé Barye Tatang, Jacques Richard Mache, Cyrill Joël Ngally Sabouang, Angélina Razafitianamaharavo, Renaud Gley, Sakéo Kong et 1 autre(s)

RSC Advances

In this study, kaolinite-poly(urea-formaldehyde) was successfully prepared through the polymerization of urea intercalated within the kaolinite structure. Polymerization was carried out under ambient conditions by immersing kaolinite-urea in formaldehyde. Evidence of urea intercalation and polymerization was obtained from FTIR, XRD, and thermal analysis (TG-DSC). The XRD pattern of the kaolinite-poly(urea-formaldehyde) composite shows that polymerization induces exfoliation of the kaolinite layers, leading to the formation of a nanocomposite. Textural analysis through nitrogen adsorption on raw kaolinite and kaolinite-urea demonstrates that polymerization mainly occurs within the interlayer. Water resistance tests show that poly(urea-formaldehyde) within the nanocomposite is less sensitive to decomposition when immersed in water compared to pristine poly(urea-formaldehyde). Additionally, a self-healing effect was observed for poly(urea-formaldehyde) in the nanocomposite, indicating that fragments from the decomposition of the intercalated polymer when immersed in water remain trapped within the composite matrix owing to interactions with kaolinite mineral layers. Modeling of kaolinite-poly(urea-formaldehyde) interactions allows for the proposal of a mechanism for the interlayer polymerization of intercalated urea.

• #clay minerals and soil interactions
• #polymer nanocomposites and properties
• #mesoporous materials and catalysis
• #nanocomposite

Use of Lomo-Nord Shales in Ivory Coast for the Adsorption Treatment of Humic Acid Extracted from Leachate from the Akouédo Landfill

Yoh Coulibaly, Tiangoua Koné, Sandotin Coulibaly, Jean Aimé Mbey, Lacina Coulibaly, Emmanuel Djoufac Woumfo

International Journal of Environmental Monitoring and Analysis

The environmental pollution caused by the mismanagement of household waste dumps and their leachate in developing countries has led researchers to explore adsorption treatment processes using shales from Côte d'Ivoire. To carry out this study, mineralogical characterization by X-ray Diffraction and Infrared of the shales was required prior to treatment. Using humic acid extracted from the leachates, adsorption tests were carried out using batch adsorption tests, and the optimum adsorption parameters were determined and modeled. The results of the mineralogical characterization revealed the presence of certain minerals. Batch adsorption treatment using slate from Côte d'Ivoire showed that the optimum concentration of slate to use was 30 g/L for a concentration of 15 mg/L humic acid. The duration of agitation at equilibrium was 60 minutes, with a maximum adsorption rate of 92 %. The effect of pH on the adsorption of humic acids showed that, in general, the evolution of adsorption rates was inversely proportional to the increase in pH. The highest yields were obtained at pH levels between 3.5 and 5.5. The results of the influence of the initial concentration of humic acids showed an increase in adsorption efficiency with the increase in the initial concentration up to 100 mg/L. The pseudo-second order model better described the adsorption of humic acid on the shale; it is accompanied by intra-particle diffusion, therefore by a contribution of active sites inside the pores.

• #phosphorus and nutrient management
• #mine drainage and remediation techniques
• #leachate
• #adsorption

Kaolinites structural defects related to urea and dimethyl sulfoxide intercalation

Hervé Barye Tatang, Jean Aimé Mbey, Cyrill Joël Ngally Sabouang, Jacques Richard Mache, Renaud Gley, Sakéo Kong

Applied Clay Science

• #clay minerals and soil interactions
• #co2 sequestration and geologic interactions
• #concrete and cement materials research
• #intercalation (chemistry)

Porous refractory ceramics using agrowastes and some kaolinitic clays

Amadou Pountouenchi, E.J.A. Ndzana, Ibrahim Cherif Mountapbeme, Saliou Njuhou, André Njoya, Nathalie Fagel et 3 autre(s)

Open Ceramics

In the purpose of making low cost porous refractories bricks, two kaolin named MY3 and KG from the locality of Foumban in Cameroon are used together with a rice husks (Br) and coffee residues (Rc). The formulations made of mixture of chamotte, raw clay as a binder and agricultural wastes in varying proportions, are fired at 1200 °C for 4 h. The addition of chamotte from 10 to 60 % in the studied clays, contributes to a reduction of firing shrinkage. The mineralogy of the products is made of mullite (34–38 %) which is associated to cristobalite (10–19 %), quartz (14–20 %) and amorphous phase (23–39 %). The addition of 10–20 % of agrowastes causes a reduction in the apparent density of 13 % and an increase in the open porosity of 14 %.

• #recycling and utilization of industrial and municipal waste in materials production
• #bauxite residue and utilization
• #concrete and cement materials research
• #grog

Provenance and depositional environment of the Mbam River overbank clay deposits, Central Africa: evidence from mineralogical and geochemical variations

Christophe Enock Embom, Jean Aimé Mbey, Vincent Laurent Onana, Paul‐Désiré Ndjigui

Arabian Journal of Geosciences

• #geochemistry and elemental analysis
• #geochemistry and geologic mapping
• #geological and geochemical analysis
• #geology

Review of: "Investigation of Mechanical Properties of Sisal Fiber and Sugar Palm Fiber Reinforced Hybrid Composites"

Jean Aimé Mbey

• #natural fiber reinforced composites
• #sisal
• #composite material
• #fiber

Correction: Microwave Assist Synthesis of Na-zeolite/Hydroxysodalite from a Kaolin: Effect of the Microwave Power

Patrick Kwimi Tchatat, Cyrill Joël Ngally Sabouang, Jacques Richard Mache, Sandotin Lassina Coulıbaly, Jean Mermoz Siéwé, Jean Aimé Mbey

Chemistry Africa

• #chemical synthesis and characterization
• #zeolite catalysis and synthesis
• #microwave
• #zeolite

Experimental and Numerical Study of Mechanical Behaviour of Fired Clay Bricks after Exposure to High Temperatures

Jean Calvin Bidoung, Léon Arnaud Mpoung, Jean Aimé Mbey, Jean Raymond Lucien Meva’a

Journal of Minerals and Materials Characterization and Engineering

This paper reports the modeling of residual compressive strength of fired clay bricks submitted to elevated temperature. Five formulations were used and the explored temperatures were 95?C, 200?C, 550?C, 700?C and 950?C. The stress–strain relationships and the mechanical properties (including Young’s modulus and compressive strength) were assessed using a uniaxial compressive strength machine. A proposed model equation was established and found satisfying. The elastic modulus was evaluated and tested with one existing model together with two proposed models. The proposed model was both satisfying and even more precise than the existing one. The overall results show that the effect of temperature on the mechanical properties of clays can be accurately described through the definition of thermal damage using elastic modulus.

• #fire effects on concrete materials
• #structural response to dynamic loads
• #advanced ceramic materials synthesis
• #compressive strength

Influence of the Extraction Location on the Physical and Mechanical Properties of the Pseudo-Trunk Banana Fibers

Laurent Libog, Florent Biyeme, Achille Désiré Omgba Betené, Achille Bernard Biwôlé, Bénoît Ndiwé, Jonas Peequeur Essome Mbang et 3 autre(s)

Figshare

The specific properties and availability of banana pseudo-trunk fibers make them a promising alternative for the development of green composites. However, the wide dispersion of their properties can hinder their use. In this study, the influence of the sampling area of the banana pseudo-trunk on the physical and mechanical properties of the fibers was evaluated. Prior to retting, the trunk was sampled longitudinally (bottom, middle and top) and transversely (periphery, intermediate and heart). Gravimetric tests were carried out and revealed variations in water absorption (347.1–517.4%), density (0.92–1.45 g.cm⁻³) and linear mass (25 -34tex). Tensile tests were also performed and showed a significant effect of fiber location on Young’s modulus (6.60–34.6GPa), tensile strength (91-350MPa) and elongation at the break (0.9–2.6%). Due to diameter scatter, variations of 42% were found for fibers in the same area. In a region, the physical properties increase from the periphery to the core, and the mechanical properties decrease in the same direction, except for elongation. The results of this study showed good agreement with those of other natural fiber types. However, we recommend the peripheral areas of the pseudo-trunk to extract reinforcing fibers from composites because of their low density (0.9 g.cm⁻³) and their high stiffness (34GPa).

• #natural fiber reinforced composites
• #trunk
• #extraction (chemistry)
• #computer science

Influence of the Extraction Location on the Physical and Mechanical Properties of the Pseudo-Trunk Banana Fibers

Laurent Libog, Florent Biyeme, Achille Désiré Omgba Betené, Achille Bernard Biwôlé, Bénoît Ndiwé, Jonas Peequeur Essome Mbang et 3 autre(s)

Journal of Natural Fibers

The specific properties and availability of banana pseudo-trunk fibers make them a promising alternative for the development of green composites. However, the wide dispersion of their properties can hinder their use. In this study, the influence of the sampling area of the banana pseudo-trunk on the physical and mechanical properties of the fibers was evaluated. Prior to retting, the trunk was sampled longitudinally (bottom, middle and top) and transversely (periphery, intermediate and heart). Gravimetric tests were carried out and revealed variations in water absorption (347.1–517.4%), density (0.92–1.45 g.cm−3) and linear mass (25 -34tex). Tensile tests were also performed and showed a significant effect of fiber location on Young’s modulus (6.60–34.6GPa), tensile strength (91-350MPa) and elongation at the break (0.9–2.6%). Due to diameter scatter, variations of 42% were found for fibers in the same area. In a region, the physical properties increase from the periphery to the core, and the mechanical properties decrease in the same direction, except for elongation. The results of this study showed good agreement with those of other natural fiber types. However, we recommend the peripheral areas of the pseudo-trunk to extract reinforcing fibers from composites because of their low density (0.9 g.cm−3) and their high stiffness (34GPa).

• #natural fiber reinforced composites
• #bamboo properties and applications
• #tree root and stability studies
• #retting

Interactions between Humic Acid and the Mineral Surface of Laterite at Different Environmental pH

Yoh Coulibaly, Jean Aimé Mbey, Sandotin Lassina Coulıbaly, Tiangoua Koné, Lacina Coulibaly, Emmanuel Djoufac Woumfo

Journal of Global Ecology and Environment

Organic compounds such as humic substances in the natural environment, especially in aquatic environments, are source of environmental problems. The stability of humic compounds in the soil is due to their adsorption on colloid surfaces through reactions with cations to form organ- mineral complexes. Many parameters such as pH, ionic strength. can affect the adsorption of humic substance on mineral surfaces. This study was initiated to investigate the use of a natural geo-material such as laterite for recovery and environmental application through batch adsorption tests. Since this system is a closed and agitated system, it makes it possible to obtain the maximum conditions for adsorption. Lateritic soil are abundant in tropical soil and exhibits some specificities that could promote humic acids-soil interactions. So, the analysis of pH influence on humic acid-laterite interactions is monitores through batch adsorption tests of a commercial humic acid at different pH (4.5; 6.5 and 8.5). The adsorption kinetic yield (R) is followed at each pH. Prior to the adsoption test, the raw laterite was analysed using infrared spectroscopy. The results of the kinetics of humic acid adsorption yield at different pH (4.5; 6.5 and 8.5) showed that the adsorption yield was inversely proportional to the increase of pH. The highest yield is obtained at pH 4.5 (94.56 %). Infrared analyzes of the laterite before and after adsorption shows that the surface of the laterite has undergone modifications associated to humic acid presence in the complexe after adsorption test. However, the media most affected by adsorption were observed at pH 8.5 and pH 4.5. The changes observed are due to the interactions between the aluminum oxides of gibbsite-AH (Al(OH)2–O–R) and kaolinite-AH (Si2O5Al2(OH)3–OH–R present on the surface of materials and the bonds of carboxylic, aromatic, phenolic, etc. groups confirms the adsorption reaction between humic acid and laterite.

• #marine and environmental studies
• #laterite
• #adsorption
• #humic acid

Microwave Assist Synthesis of Na-zeolite/Hydroxysodalite from a Kaolin: Effect of the Microwave Power

Patrick Kwimi Tchatat, Cyrill Joël Ngally Sabouang, Jacques Richard Mache, Sandotin Lassina Coulıbaly, Jean Mermoz Siéwé, Jean Aimé Mbey

Chemistry Africa

• #zeolite catalysis and synthesis
• #chemical synthesis and characterization
• #clay minerals and soil interactions
• #zeolite

DMSO Deintercalation in Kaolinite–DMSO Intercalate: Influence of Solution Polarity on Removal

Berenger ZOGO MFEGUE, Jean Aimé Mbey, Sandotin Lassina Coulıbaly, Vincent Laurent Onana, Paul‐Désiré Ndjigui

Journal of Composites Science

This study focused on the deintercalation of dimethyl sulfoxide (DMSO) from a kaolinite–DMSO complex in various solvents. The use of kaolinite as filler in polymer–clay composite generally faced the difficulty of kaolinite dispersion due to its high cohesion. For improved dispersion of kaolinite within a given matrix, previous intercalation of small polar molecules is usually done prior to its displacement during composite-making. The influence of the solvent polarity on the deintercalation in analyzed here to understand its role during the deintercalation process. The intercalation of the DMSO was done by solution-mixing and its displacement was done in distilled water, ethyl acetate, and acetone. The products of deintercalation were analyzed using Fourier transform infra-red (FTIR), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The weakening of the kaolinite cohesion after DMSO intercalation is demonstrated through the broadening of the diffraction peak associated with the kaolinite on XRD patterns. From FTIR spectra, the weakening is associated with the displacement to low wavenumbers of the Si–O or Al–O vibration bands within the kaolinite–DMSO complex. The kaolinite dehydroxylation temperatures from DSC show that the rate of DMSO displacement affects the ordering of the recovered kaolinite. The crystallite size of the kaolinite is reduced from the raw to the recovered kaolinite after DMSO displacement, indicating an exfoliation of the kaolinite. From these results, it is found that the removal of the DMSO from the kaolinite–DMSO complex is influenced by solvent polarity. The higher the polarity, the greater the removal of the DMSO from the complex. Solvent polarity affects the rate of DMSO displacement, which influences the ordering of the recovered kaolinite. It is suggested that solvent polarity can be used to control the removal rate of DMSO, which may be key to the dispersion of the kaolinite platelets.

• #polymer nanocomposites and properties
• #clay minerals and soil interactions
• #fiber-reinforced polymer composites
• #kaolinite

Intercalation of Ciprofloxacin in Naturally Occurring Smectite from Bana: Potentiality as Drug Delivery System and Antimicrobial Effects on <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>

Carine Feudjio Memenfo, Nicolas Tabary, Jean Aimé Mbey, Stéphanie Degoutin, Frédéric Cazaux, Maryse Bacquet et 3 autre(s)

Journal of Materials Science and Chemical Engineering

Ciprofloxacin (CFX) was loaded on Bana clay (Cameroon) and CFX loaded-clays have been evaluated as drug delivery system. Raw clays and CFX loaded compounds have been characterized by some physico-chemicals methods. In vitro release studies have been done in gastric and phosphate buffer experimental mediums; bacteriological studies have been made up on Escherichia coli and Staphylococcus aureus. X-ray diffractometry patterns of loaded compounds show a basal spacing increasing due to CFX intercalation. On Fourier-Transformed Infrared spectrometry spectra, appearance of CFX characteristic bands and shifting of certain bands already presents on clay confirmed CFX intercalation. After 96 h of CFX released from release mediums, prolonged and continue profiles have been observed. Diffusion tests displayed an inhibition radius of ~2 cm on gelose seeded with Escherichia coli and Staphylococcus aureus due to CFX. The overall results show a modified release of ciprofloxacin with an effective antibacterial activity, giving the way for a new ciprofloxacin drug delivery system using Bana clay as carrier.

• #clay minerals and soil interactions
• #therapeutic uses of natural elements
• #geotechnical and construction materials studies
• #escherichia coli

The thermal dehydroxylation of kaolinite using thermogravimetric analysis and Controlled rate thermal analysis

Jean Aimé Mbey, Cyrill Joël Ngally Sabouang, Thomas Beauregard Makon, Sandotin Lassina Coulıbaly, Sakéo Kong

Journal of the Cameroon academy of sciences

The aim of this work was to identify parameters that could influence the conversion of kaolinite into metakaolinite. To this end, the dehydroxylation of four kaolinites, using controlled rate thermal analysis (CRTA) and thermogravimetric analysis (TGA), was investigated. X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) were used to confirm the kaolinitic nature of the samples. Their crystallinity was evaluated using the Hinckley index from the XRD patterns and transmission electron microscopy (TEM) was used for morphological observation of the clay platelets. The thermal analyses of the samples indicate, for all samples, low defects as revealed by the low amount of adsorbed water on the clay surface. The dehydroxylation temperature from both techniques was influenced by the sample crystallinity and particle size. It was observed from both techniques that increase crystallinity resulted in highdehydroxylation temperature. Also, the influence of the clay platelets size on the dehydroxylation temperature, is proposed. All the results indicate that crystallinity and particle size are parameters that could be used to control the temperature for the conversion of kaolinite to metakaolinite. Keywords: Kaolinite; Crystallinity, Dehydroxylation; Thermal analysis

• #clay minerals and soil interactions
• #thermal and kinetic analysis
• #concrete and cement materials research
• #crystallinity

DMSO Intercalation in Selected Kaolinites: Influence of the Crystallinity

Jean Aimé Mbey, Jean Mermoz Siéwé, Cyrill Joël Ngally Sabouang, Angélina Razafitianamaharavo, Sakéo Kong, Fabien Thomas

ChemEngineering

The present study deals with the relation between crystalline order in kaolinites and their ability to intercalate DMSO. Raw clays and kaolinite–DMSO complexes are analyzed using FTIR, XRD powder diffraction and differential scanning calorimetry and thermogravimetric analysis (DSC-TGA). The crystallinity is accessed using the Hinckley index (HI) from the raw clays’ XRD patterns and the p2 factor from their FTIR spectra. The intercalation ratio is evaluated from XRD and compared among the samples. The thermal analyses show a decrease in the dehydroxylation temperature in the DMSO–kaolinite complexes, indicating a decrease in the interlayer cohesion that may be useful to improve the delamination of kaolinite. The analysis of the coherent scattering domain size in the raw and the DMSO-intercalated samples indicates that the ordering is not affected during the DMSO intercalation. From these results, it is deduced that DMSO intercalation is favored by an increased crystallinity, as revealed by the intercalation ratio from XRD and the DSMO release during DSC-TGA analysis.

• #clay minerals and soil interactions
• #polymer nanocomposites and properties
• #soil and unsaturated flow
• #intercalation (chemistry)

Improved microstructure and free efflorescence geopolymer binders

Chantale Njiomou Djangang, Jean Aimé Mbey, Cyprien Joël Ekani, Severin Tabou Tiam, Philippe Blanchart, Daniel Njopwouo

SN Applied Sciences

• #concrete and cement materials research
• #magnesium oxide properties and applications
• #recycling and utilization of industrial and municipal waste in materials production
• #geopolymer

Phosphoric acid activation of volcanic ashes: Influence of the molar ratio R = (MgO + CaO) / P2O5 on reactivity of volcanic ash and strength of obtained cementitious material

B.I. Djon Li Ndjock, Rafael Robayo–Salazar, Ruby Mejía de Gutiérrez, Jean Baenla, Jean Aimé Mbey, Martin Cyr et 1 autre(s)

Journal of Building Engineering

• #concrete and cement materials research
• #magnesium oxide properties and applications
• #recycling and utilization of industrial and municipal waste in materials production
• #phosphoric acid

Preliminary study on the use of corn cob as pore forming agent in lightweight clay bricks: Physical and mechanical features

Dalisiane Elodie Njeumen Nkayem, Jean Aimé Mbey, B.B. Kenne Diffo, D. Njopwouo

Journal of Building Engineering

• #recycling and utilization of industrial and municipal waste in materials production
• #building materials and conservation
• #hygrothermal properties of building materials
• #flexural strength

Mineralogical, physical and mechanical features of ceramic products of the alluvial clastic clays from the Ngog-Lituba region, Southern Cameroon

Paul‐Désiré Ndjigui, Jean Aimé Mbey, Aubin Nzeugang Nzeukou

Journal of Building Engineering

• #recycling and utilization of industrial and municipal waste in materials production
• #absorption of water
• #hematite
• #flexural strength

Talc-based cementitious products: Effect of talc calcination

C.J. Ngally Sabouang, Jean Aimé Mbey, Frédéric Hatert, D. Njopwouo

Journal of Asian Ceramic Societies

This study reports the use of calcined talc for cementitious products making. The calcination is used to enhance the availability of magnesium from talc to react with phosphate for cement phase formation. It is shown that previous calcination of talc leads to products having enhanced mechanical performance due to the formation of more cement phase than in products based on raw talc. Talc fired at 900 °C was found to be the one in which magnesium release was maximal. Firing at temperature higher than 900 °C leads to the stabilization of enstatite, which decreased the magnesium availability. The cement phase is struvite, which was better detected on the X-ray patterns of the products involving fired talc. All the products have very rapid setting time and low shrinkage.

• #magnesium oxide properties and applications
• #concrete and cement materials research
• #recycling and utilization of industrial and municipal waste in materials production
• #talc

Mineralogical and physicochemical characterization of Ngaye alluvial clays (Northern Cameroon) and assessment of its suitability in ceramic production

Soureiyatou Fadil-Djenabou, Paul‐Désiré Ndjigui, Jean Aimé Mbey

Journal of Asian Ceramic Societies

This study reports the physicochemical analysis of three alluvial clastic clays from the Ngaye River in northern Cameroon. X-ray diffraction, infra-red spectroscopy, scanning electron microscopy and thermal analysis are used to establish the mineralogical composition. It is found that the main clay minerals in these samples are kaolinite, muscovite-illite and smectite associated with quartz, goethite, feldspars and anatase. This mineralogical assemblage is in accordance with the chemical analysis which further confirmed the high quartz proportion. The low content in fluxing agent is indicated by the low contents in Na2O, K2O, MgO and CaO. The low content in fluxing agent and high sand proportion result in poor vitrification in ceramic testing brick obtained at 900 °C, 1000 °C and 1100 °C. For all the firing temperatures, linear shrinkage varied from 0.7% to 2.6%, weight loss varied from 3.5% to 7%, bulk density varied from 1.6 to 1.8 g/m3, water absorption decreased from 20.7% to 12.7%, and flexural strength (σ) varied from 0.60 to 2.07 MPa.

• #recycling and utilization of industrial and municipal waste in materials production
• #clay minerals and soil interactions
• #concrete and cement materials research
• #kaolinite

Mineralogical, Physicochemical Properties of smectite clays from Bana (Western Cameroon) and Preliminary test as Potential oil bleaching earth

Jacques Richard Mache, P. Signing, Jean Aimé Mbey, F. Thomas, D. Njopwouo, Nathalie Fagel

Open Repository and Bibliography (University of Liège)

• #clay minerals and soil interactions
• #therapeutic uses of natural elements
• #clay minerals
• #geology

Talc as raw material for cementitious products formulation

C.J. Ngally Sabouang, Jean Aimé Mbey, Liboum, Fabien Thomas, D. Njopwouo

Journal of Asian Ceramic Societies

This study reports the characterization of a talc from Cameroon as a possible source material for cement formulation. To that end, the talc sample was characterized and mixed with a solution of sodium polyphosphate to formulate the cementitious products. Addition of magnesia (MgO) was done to analyze the effect of available MgO on the products. Fourier transform infrared, X-rays diffraction, linear shrinkage, compressive strength and scanning electron microscopy were used to analyze the products. The compressive strength increased with addition of MgO and the linear shrinkage decreased. All the analyses indicate that talc is a raw material of interest in cementitious products formulation; however, the inclusion of the MgO is a key factor for a better performance of the products.

• #magnesium oxide properties and applications
• #concrete and cement materials research
• #recycling and utilization of industrial and municipal waste in materials production
• #talc

Films composites amidon de manioc-kaolinite : influence de la dispersion de l'argile et des interactions argile-amidon sur les propriétés des films

Jean Aimé Mbey

Publications Et Travaux Academiques de Lorraine (Universite de Lorraine)

In this study, composites films made from glycerol plasticized cassava starch and a kaolinite clay, as mineral filler, were studied. The origin and mechanisms of clay-starch interactions and their role on films properties are examined. To deal with the unexpandable nature of kaolinite, an analysis of its exfoliation mechanism was done through dimethylsulfoxide (DMSO) intercalation followed by DMSO displacement using ethyl acetate and ammonium acetate. The crystalline structure of kaolinite is deeply disordered upon DMSO displacement because of a random reassociation of the clay layers. A better dispersion of the intercalated kaolinite within a polymer matrix is then expected. This expectation was confirmed by the comparison of microscopes and X-ray diffraction analyses on films charged with various dosages of raw or DMSO intercalated kaolinite. The lowering of the glass transition temperature and the elastic modulus together with the increase of barrier effects to thermal decomposition, water vapour diffusion and visible UV transmission, confirmed that the intercalated kaolinite is better dispersed. The starch chain orientation coupled to increase starch/glycerol miscibility due to the transportation of glycerol at the interface by clay particles are the two mechanisms that better explained plasticization effect induced by the filler. The interference of starch-kaolinite interactions on starch chain-chain interactions caused a decrease of starch matrix cristallinity that contribute to increase plasticization. The starch-kaolinite interactions are found to be weak due electrostatic repulsion associated to some weak associative forces due to hydrogen bonds

• #clay minerals and soil interactions
• #chemistry
• #humanities
• #molecular biology

Smectite clay from the Sabga deposit (Cameroon): mineralogical and physicochemical properties

Jacques Richard Mache, P. Signing, André Njoya, Frankline Kunyukubundo, Jean Aimé Mbey, D. Njopwouo et 1 autre(s)

Clay Minerals

Abstract The physicochemical and mineralogical characterization of the <250 μm particle-size fraction from six clay-rich samples from the Sabga deposit (north-west, Cameroon) were carried out to evaluate their potential applications. The major clay mineral is dioctahedral smectite and minor kaolinite is present in three of the clay samples. Cristobalite, feldspars, ilmenite and heulandite are accessory minerals. Application of the Greene-Kelly test revealed that the smectite present is montmorillonite. The chemical composition (wt.%) of the bulk clays consists of (66–70%) SiO 2 , (13–16%) Al 2 O 3 and (2–7%) Fe 2 O 3 . Physico-chemical characterization of the clays showed that the cation exchange capacity (CEC) and the specific surface area range from 38 to 46 meq/100 g and from 33 to 90 m 2 /g respectively. The physical and chemical properties are fully compatible with potential uses in environmental applications. After purification and chemical modification, these materials could also be used in refining edible oil as adsorbent, waste water treatment and wine technology.

• #clay minerals and soil interactions
• #iron oxide chemistry and applications
• #therapeutic uses of natural elements
• #clay minerals

Synthesis of volcanic ash-based geopolymer mortars by fusion method: Effects of adding metakaolin to fused volcanic ash

H. Tchakoute Kouamo, Jean Aimé Mbey, Antoine Elimbi, B.B. Kenne Diffo, D. Njopwouo

Ceramics International

• #concrete and cement materials research
• #recycling and utilization of industrial and municipal waste in materials production
• #building materials and conservation
• #metakaolin

The effect of adding alumina-oxide to metakaolin and volcanic ash on geopolymer products: A comparative study

H. Tchakoute Kouamo, Antoine Elimbi, Jean Aimé Mbey, Cyrill Joël Ngally Sabouang, D. Njopwouo

Construction and Building Materials

• #concrete and cement materials research
• #innovative concrete reinforcement materials
• #magnesium oxide properties and applications
• #metakaolin

The role of the starch matrix-kaolinite filler interface in composite biopolymer films

Sandrine Hoppe, Jean Aimé Mbey, Fabien Thomas

HAL (Le Centre pour la Communication Scientifique Directe)

International audience

• #engineering technology and methodologies
• #adsorption, diffusion, and thermodynamic properties of materials
• #biopolymer
• #composite number

Flocculation of Kaolinite Suspensions in Water by Coconut Cream Casein

Jacques K. Fatombi, Jean Aimé Mbey, Taofiki Aminou, Bruno Lartiges, Nikita Topanou, Odile Barrès et 1 autre(s)

Journal of Water Resource and Protection

The flocculation of kaolinite colloidal particles was carried out at pH = 6 in suspension of initial turbidity varying between 24 NTU and 102 NTU by a casein extracted from Cocos nucifera cream. During Jar-test essays, 90% to 99% of colloids were eliminated in the sediments. The optimal doses of casein used depend on the initial colloids concentrations of the suspension and were found to be 60 mg/L and 100 mg/L respectively for suspensions having turbidity of 24 NTU and 102 NTU. The corresponding residual turbidity are respectively 2.80 NTU and 10.22 NTU for clarified water. The structural analysis of the freeze-dried sediments by FTIR shows sharp adsorption bands at 1558 cm–1 and 1653 cm–1, indicating the presence of casein in the sediment. The flocculation process between the particles of kaolinite and the coconut casein is adsorption and bridging.

• #coagulation and flocculation studies
• #clay minerals and soil interactions
• #coastal wetland ecosystem dynamics
• #flocculation