Currently, in a context of sustainable development, the economic and environmental challenges incite, to valorize local materials such as clays and agro-industrial waste. It is in this approach that a new category of ...Currently, in a context of sustainable development, the economic and environmental challenges incite, to valorize local materials such as clays and agro-industrial waste. It is in this approach that a new category of compressed earth bricks (BTC) stabilized with shea meal (TK) and cement was proposed. The purpose of this paper is to investigate the effect of shea meal rate on the thermal conductivity properties of cement stabilized earth bricks. A lateritic clay (Lat) mainly composed of kaolinite (38.44%), quartz (24.94%), goethite (12.28%), hematite (4.44%) and illite (19.9%) was used to make bricks. Different mix designs made up of lateritic clay and 5% cement were studied. The shea meal is added as a partial lateritic clay replacement in different proportions. The thermal conductivity was determined by hot disk method and correlated to both porosity and density of elaborated materials. The results obtained show that the thermal conductivity and density of bricks decrease respectively from 0.72 W·m-1·K-1 to 0.52 W·m-1·K-1 and from 2.77 g·cm-3 to 2.52 g·cm-3. The presence of shea meal within the material generates pore formation, which may partly explain the improvement of the thermal insulation properties. A positive correlation was noted between density and thermal conductivity of these materials.展开更多
The aim of this work was to test the adsorption efficiency of copper (II) ions in an aqueous solution on Natural Smectite (NS) and Activated Carbon (AC). The experiments carried out in batch mode made it possible to d...The aim of this work was to test the adsorption efficiency of copper (II) ions in an aqueous solution on Natural Smectite (NS) and Activated Carbon (AC). The experiments carried out in batch mode made it possible to determine the stirring time, the adsorbent mass, the pH, the initial concentration of copper (II) ions, the isotherms and the adsorption kinetics. It appears that the stirring time was 15 minutes for the AC and 20 minutes for the NS. The adsorption was at maximum for the two adsorbents at optimum pH of 3.5 for a mass of 0.05 g each. The quantity of copper (II) ions adsorbed was 26.6 mg/L for NS and 36.6 mg/g for AC of a concentration of 600 mg/L each. The Langmuir isotherm was the one that best described the adsorption process for the two adsorbents. The adsorption kinetics obtained was that of the pseudo second-order for our two adsorbents. The results obtained showed that these two adsorbents were effective for the adsorption of copper (II) ions in an aqueous solution.展开更多
This work focuses on the analysis of the chemical composition of soils dedicated to agriculture in order to assess the impacts of manganese mining activity in the city of Moanda in South-East Gabon. The result of the ...This work focuses on the analysis of the chemical composition of soils dedicated to agriculture in order to assess the impacts of manganese mining activity in the city of Moanda in South-East Gabon. The result of the analysis obtained using wavelength dispersive X-ray fluorescence revealed the presence of twenty-seven elements in the seventeen soil samples collected namely: Na, K, Rb, Mg, Ca, Sr, Ba, Ti, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Cr, Mn, Al, O, C, P, S, Si, I, Ac and Th. Iron (Fe), aluminum (Al) and manganese (Mn) were respectively higher. The practice of agriculture near mining sites is not without risks for the quality of agricultural products and the health of the population.展开更多
Particles of TiO2 modified with poly 3-(2-thienyl) aniline (PThA) and occluded in poly 2,2 bithiophene (PBTh), were subjected to optical, electrochemical impedance spectroscopic (EIS) and photoelectrochemical (PEC) in...Particles of TiO2 modified with poly 3-(2-thienyl) aniline (PThA) and occluded in poly 2,2 bithiophene (PBTh), were subjected to optical, electrochemical impedance spectroscopic (EIS) and photoelectrochemical (PEC) investigation in aqueous, acetate, citrate, and phosphate electrolytes. EIS studies revealed that the assembly film of TiO2/PThA/PBTh possess porous-type structure. They also confirmed the approximate value of Ef obtained from electrochemical studies. Both EIS and optical studies indicated that ac conductivity is much greater than dc conductivity. Guided by the properties of PBTh, no large changes in the energy band structure occurred due to occlusion of TiO2 in PBTh films. Occlusion of TiO2/PThA into the network structure of PBTh inhibits the energy dissipation process and impeded charge polarization process of the material. Photoelectrochemical outcome suggested possible band alignments between the organic film and TiO2 and formation of hybrid sub-bands. Inclusion of TiO2 in the thiophene-based polymers enhanced the charge separation and consequently charge transfer processes and widen the absorption in visible light range.展开更多
文摘Currently, in a context of sustainable development, the economic and environmental challenges incite, to valorize local materials such as clays and agro-industrial waste. It is in this approach that a new category of compressed earth bricks (BTC) stabilized with shea meal (TK) and cement was proposed. The purpose of this paper is to investigate the effect of shea meal rate on the thermal conductivity properties of cement stabilized earth bricks. A lateritic clay (Lat) mainly composed of kaolinite (38.44%), quartz (24.94%), goethite (12.28%), hematite (4.44%) and illite (19.9%) was used to make bricks. Different mix designs made up of lateritic clay and 5% cement were studied. The shea meal is added as a partial lateritic clay replacement in different proportions. The thermal conductivity was determined by hot disk method and correlated to both porosity and density of elaborated materials. The results obtained show that the thermal conductivity and density of bricks decrease respectively from 0.72 W·m-1·K-1 to 0.52 W·m-1·K-1 and from 2.77 g·cm-3 to 2.52 g·cm-3. The presence of shea meal within the material generates pore formation, which may partly explain the improvement of the thermal insulation properties. A positive correlation was noted between density and thermal conductivity of these materials.
文摘The aim of this work was to test the adsorption efficiency of copper (II) ions in an aqueous solution on Natural Smectite (NS) and Activated Carbon (AC). The experiments carried out in batch mode made it possible to determine the stirring time, the adsorbent mass, the pH, the initial concentration of copper (II) ions, the isotherms and the adsorption kinetics. It appears that the stirring time was 15 minutes for the AC and 20 minutes for the NS. The adsorption was at maximum for the two adsorbents at optimum pH of 3.5 for a mass of 0.05 g each. The quantity of copper (II) ions adsorbed was 26.6 mg/L for NS and 36.6 mg/g for AC of a concentration of 600 mg/L each. The Langmuir isotherm was the one that best described the adsorption process for the two adsorbents. The adsorption kinetics obtained was that of the pseudo second-order for our two adsorbents. The results obtained showed that these two adsorbents were effective for the adsorption of copper (II) ions in an aqueous solution.
文摘This work focuses on the analysis of the chemical composition of soils dedicated to agriculture in order to assess the impacts of manganese mining activity in the city of Moanda in South-East Gabon. The result of the analysis obtained using wavelength dispersive X-ray fluorescence revealed the presence of twenty-seven elements in the seventeen soil samples collected namely: Na, K, Rb, Mg, Ca, Sr, Ba, Ti, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Cr, Mn, Al, O, C, P, S, Si, I, Ac and Th. Iron (Fe), aluminum (Al) and manganese (Mn) were respectively higher. The practice of agriculture near mining sites is not without risks for the quality of agricultural products and the health of the population.
文摘Particles of TiO2 modified with poly 3-(2-thienyl) aniline (PThA) and occluded in poly 2,2 bithiophene (PBTh), were subjected to optical, electrochemical impedance spectroscopic (EIS) and photoelectrochemical (PEC) investigation in aqueous, acetate, citrate, and phosphate electrolytes. EIS studies revealed that the assembly film of TiO2/PThA/PBTh possess porous-type structure. They also confirmed the approximate value of Ef obtained from electrochemical studies. Both EIS and optical studies indicated that ac conductivity is much greater than dc conductivity. Guided by the properties of PBTh, no large changes in the energy band structure occurred due to occlusion of TiO2 in PBTh films. Occlusion of TiO2/PThA into the network structure of PBTh inhibits the energy dissipation process and impeded charge polarization process of the material. Photoelectrochemical outcome suggested possible band alignments between the organic film and TiO2 and formation of hybrid sub-bands. Inclusion of TiO2 in the thiophene-based polymers enhanced the charge separation and consequently charge transfer processes and widen the absorption in visible light range.
