Since their discovery, zeolites have generated significant interest in various technological fields, such as molecular sieves, ion exchangers, catalysts, and especially as adsorbents. This article focuses on character...Since their discovery, zeolites have generated significant interest in various technological fields, such as molecular sieves, ion exchangers, catalysts, and especially as adsorbents. This article focuses on characterizing the types of zeolites present in Sangarédi bauxite. To achieve this objective, we conducted a physico-chemical characterization (moisture, particle size, volumetric density, porosity) and determined the optimal conditions for activating the zeolite samples (15% H2SO4 concentration, L/S ratio of 2, temperature of 70˚C, duration of 3 hours). Techniques used to characterize the samples included desiccation gravimetry, mechanical sieving, X-ray fluorescence (atomic percentage), X-ray diffraction, BET method, and water pycnometry. Additionally, we assessed the adsorption capacity of zeolites activated by the elimination of methylene blue in an aqueous solution, which was selected as a model water pollutant. According to X-ray fluorescence and diffraction data, there are nine types of zeolite in Sangarédi bauxite, divided into five families. Regarding physical activation, a good porous structure was observed at a temperature of 300˚C to 340˚C for 4 hours. Above this range, material condensation occurs, leading to a sudden increase in mass loss, which can be explained by a change in their crystalline structure. After treatment with sulfuric acid, the activated samples showed an increase in specific surface area (from 72 to 130.25 m2∙g−1 on average) and porosity (from 0.07% to 0.3%), as well as an increased susceptibility to methylene blue discoloration (from 13.58% to 30.35%). These results confirm the improvement in the microporous structure and the formation of a more developed molecular sieve network. Thanks to the identified structural and textural characteristics, it can be concluded that the activated zeolites obtained are extremely reactive materials and can be used effectively in water treatment.展开更多
The chemical and mineralogical composition of bauxite deposits is a key factor in the profitability of refining processes. The study of bauxites from the Saföfö site has assessed variations in chemical and m...The chemical and mineralogical composition of bauxite deposits is a key factor in the profitability of refining processes. The study of bauxites from the Saföfö site has assessed variations in chemical and mineralogical composition under various conditions, as well as the optimum conditions for their exploitation. The methodologies used in this study include experimental methods for determining moisture content, chemical composition, mineralogical composition, and specific density of bauxite. The results show significant variation in moisture content among the bauxite samples, with values ranging from 2.90% to 17.80%. The silica percentages in the samples range from 1.69% to 8.14%, while alumina percentages vary from 36.81% to 54.03%. After calcination, alumina oxide percentages range from 40% to 75%. After chemical activation, alumina oxides Al2O3 range from 40% to over 50%. Gibbsite is the most abundant mineral, accounting for about 60% - 70% of the total composition of the bauxite samples. Samples A to F have bulk densities varying between approximately 3.6 and 3.9. Sample B has the highest density, around 3.9, while sample C has the lowest, at around 3.5. Bauxite mining at the Saföfö site offers significant potential for the alumina industry, provided appropriate processing methods are selected to maximize quality and profitability while minimizing environmental impact.展开更多
The aim of the study is to identify sources of atmospheric pollutants and assess their impact on the health of Conakry’s population. Ten contaminant sources were identified. Sampling was conducted on suspended partic...The aim of the study is to identify sources of atmospheric pollutants and assess their impact on the health of Conakry’s population. Ten contaminant sources were identified. Sampling was conducted on suspended particles and gases. Physicochemical methods were used to determine pollutant levels. The results show that CO2 is the highest gaseous pollutant at the Dar es Salaam landfill (708 μg/m3), followed by CO (354 μg/m3). The highest content of volatile organic compounds (VOC) was observed at the Tombo thermal power plant (475 μg/m3). Nitrogen oxides and hydrocarbon pollutants (NOx and CnH2n+2) at each site were relatively stable, with levels between (100 - 150 μg/m3) and (450 μg/m3), respectively. Suspended particulates (PM10 and PM2.5) measured at various locations showed higher PM10 levels than PM2.5. In particular, the highest PM10 content was observed at the Sangoyah soap factory (410 μg/m3), followed by the Madina market (319 μg/m3) and the Dar-Es-Salam landfill (318 μg/m3). As indicated by the results, these contamination levels far exceed European and World Health Organization standards. This study highlights the need to adopt a strategy to reduce pollution levels at these critical points to protect the health of the city’s population.展开更多
文摘Since their discovery, zeolites have generated significant interest in various technological fields, such as molecular sieves, ion exchangers, catalysts, and especially as adsorbents. This article focuses on characterizing the types of zeolites present in Sangarédi bauxite. To achieve this objective, we conducted a physico-chemical characterization (moisture, particle size, volumetric density, porosity) and determined the optimal conditions for activating the zeolite samples (15% H2SO4 concentration, L/S ratio of 2, temperature of 70˚C, duration of 3 hours). Techniques used to characterize the samples included desiccation gravimetry, mechanical sieving, X-ray fluorescence (atomic percentage), X-ray diffraction, BET method, and water pycnometry. Additionally, we assessed the adsorption capacity of zeolites activated by the elimination of methylene blue in an aqueous solution, which was selected as a model water pollutant. According to X-ray fluorescence and diffraction data, there are nine types of zeolite in Sangarédi bauxite, divided into five families. Regarding physical activation, a good porous structure was observed at a temperature of 300˚C to 340˚C for 4 hours. Above this range, material condensation occurs, leading to a sudden increase in mass loss, which can be explained by a change in their crystalline structure. After treatment with sulfuric acid, the activated samples showed an increase in specific surface area (from 72 to 130.25 m2∙g−1 on average) and porosity (from 0.07% to 0.3%), as well as an increased susceptibility to methylene blue discoloration (from 13.58% to 30.35%). These results confirm the improvement in the microporous structure and the formation of a more developed molecular sieve network. Thanks to the identified structural and textural characteristics, it can be concluded that the activated zeolites obtained are extremely reactive materials and can be used effectively in water treatment.
文摘The chemical and mineralogical composition of bauxite deposits is a key factor in the profitability of refining processes. The study of bauxites from the Saföfö site has assessed variations in chemical and mineralogical composition under various conditions, as well as the optimum conditions for their exploitation. The methodologies used in this study include experimental methods for determining moisture content, chemical composition, mineralogical composition, and specific density of bauxite. The results show significant variation in moisture content among the bauxite samples, with values ranging from 2.90% to 17.80%. The silica percentages in the samples range from 1.69% to 8.14%, while alumina percentages vary from 36.81% to 54.03%. After calcination, alumina oxide percentages range from 40% to 75%. After chemical activation, alumina oxides Al2O3 range from 40% to over 50%. Gibbsite is the most abundant mineral, accounting for about 60% - 70% of the total composition of the bauxite samples. Samples A to F have bulk densities varying between approximately 3.6 and 3.9. Sample B has the highest density, around 3.9, while sample C has the lowest, at around 3.5. Bauxite mining at the Saföfö site offers significant potential for the alumina industry, provided appropriate processing methods are selected to maximize quality and profitability while minimizing environmental impact.
文摘The aim of the study is to identify sources of atmospheric pollutants and assess their impact on the health of Conakry’s population. Ten contaminant sources were identified. Sampling was conducted on suspended particles and gases. Physicochemical methods were used to determine pollutant levels. The results show that CO2 is the highest gaseous pollutant at the Dar es Salaam landfill (708 μg/m3), followed by CO (354 μg/m3). The highest content of volatile organic compounds (VOC) was observed at the Tombo thermal power plant (475 μg/m3). Nitrogen oxides and hydrocarbon pollutants (NOx and CnH2n+2) at each site were relatively stable, with levels between (100 - 150 μg/m3) and (450 μg/m3), respectively. Suspended particulates (PM10 and PM2.5) measured at various locations showed higher PM10 levels than PM2.5. In particular, the highest PM10 content was observed at the Sangoyah soap factory (410 μg/m3), followed by the Madina market (319 μg/m3) and the Dar-Es-Salam landfill (318 μg/m3). As indicated by the results, these contamination levels far exceed European and World Health Organization standards. This study highlights the need to adopt a strategy to reduce pollution levels at these critical points to protect the health of the city’s population.
