To meet the ever-increasing construction demands around the world during recent years,reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of...To meet the ever-increasing construction demands around the world during recent years,reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of fine-grained soils.Although lime stabilization increases the compressive strength of soils,it reduces the soil ductility at the same time.Recent research shows that random fiber inclusion modifies the brittleness of soils.In the current research,the effects of lime and polypropylene(PP)fiber additions on such characteristics as compressive and shear strengths,failure strain,secant modulus of elasticity(E50)and shear strength parameters of mixtures were investigated.Kaolinite was treated with 1%,3% and 5% lime by dry weight of soil and reinforced with 0.1% monovalent PP fibers with the length of 6 mm.Samples were prepared at optimum conditions and cured at 35℃ for 1 d,7 d and 28 d at 90% relative humidity and subsequently subjected to uniaxial and triaxial compression tests(UCT and TCT)under cell pressures of 25 kPa,50 kPa and 100 kPa.Results showed that inclusion of random PP fibers to clay-lime mixtures increases both compressive and shear strengths as well as the ductility.Lime content and curing period were found to be the most influential factors.Scanning electron microscopy(SEM)analysis showed that lime addition and the formation of cementitious compounds bind soil particles and increase soil/fiber interactions at interface,leading to enhanced shear strength.The more ductile the stabilized and reinforced composition,the less the cracks in roads and waste landfill covers.展开更多
We studied the states of rare earth elements in ore of the Xianglushan rare earth deposit. Rare earth ore samples were tested and examined by scanning electron microscope, electron probe, and chemical leaching. No ind...We studied the states of rare earth elements in ore of the Xianglushan rare earth deposit. Rare earth ore samples were tested and examined by scanning electron microscope, electron probe, and chemical leaching. No independent rare earth minerals were detected by scanning electron microscope. Elements detected by the electronic probe for the in situ micro-zone of the sample included: O,Al, Si, Ca, Mg, Fe, Ti, K, Na, S, Cl, C, Cu, Cr, V, and Pt.Rare earth elements were not detected by electron probe.(NH_4)_2 SO_4,(NH_4)Cl, NaCl, and H_2 SO_4 were used as reagents in chemical leaching experiments that easily leached out rare earth elements under the action of 10%reagent, indicating that the rare earth elements in ore are mainly in the ionic state rather than present as rare earth minerals.展开更多
Geopolymers are an alternative to Portland cement, well known for their contribution to greenhouse gas emissions. Finding materials that can validly replace Portland cement is a challenge. It is in this logic that thi...Geopolymers are an alternative to Portland cement, well known for their contribution to greenhouse gas emissions. Finding materials that can validly replace Portland cement is a challenge. It is in this logic that this work was undertaken with the objective of characterizing two local clay resources of Togo as raw materials for geopolymers. The physico-chemical properties of these clays were determined by characterization using X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric (TGA) and elemental analysis (ICP-OES). The results show that these clays contain kaolinite and therefore can be used in the formulation of geopolymers. The characterized clays underwent heat treatments transforming the crystalline phases into more reactive amorphous phases and then were activated by an alkaline solution in order to formulate the geopolymer materials. These elaborated materials were analyzed by Fourier transform infrared to identify the types of bonds formed. The results of these analyses show that these two local clays are well suited to be used in synthesizing geopolymers. Our future work will focus on the constraints of consolidation as well as the mechanical properties of these geopolymer materials.展开更多
In order to contribute to the valorisation of the clay materials of Ivory Coast in the depollution of wastewater, the physicochemical and mineralogical characterization of three clay samples taken in Agboville (AGB), ...In order to contribute to the valorisation of the clay materials of Ivory Coast in the depollution of wastewater, the physicochemical and mineralogical characterization of three clay samples taken in Agboville (AGB), Bingerville (BIN) and Katiola (KAT) was carried out. The objective of this work was to compare the properties of the clays in order to identify the one that is likely to have interesting adsorptive capacities to clean up contaminated water. These clays were studied by chemical analysis, X-ray diffraction, scanning electron microscopy and thermal analysis. In addition, their specific surface areas and cation exchange capacities were determined. The AGB clay is composed of 75.51% kaolinite, 14.20% illite and 9.26% quartz. The BIN clay contains 52.21% kaolinite, 6.23% illite, 17.50% quartz and 15.71% goethite. As for the KAT clay, it contains 48.08% kaolinite, 3.55% illite, 20.14% smectite, 6.11% quartz and 16.86% goethite. Their thermal behavior and microstructure are in agreement with their mineralogy. The measured specific surface areas and cation exchange capacities are consistent with literature values. The KAT clay has the highest specific surface and cation exchange capacity. In the light of the results obtained, the KAT clay appears to be more effective in depolluting water than the BIN and AGB clays.展开更多
为深入了解煤泥浮选过程中硅酸钠对黏土矿物的选择性抑制机理,以煤和高岭石为研究对象,通过单矿物浮选试验、Zeta电位测定、X射线光电子能谱(XPS)分析,研究了硅酸钠对煤和高岭石浮选行为的影响。试验结果表明:p H值在7左右、硅酸钠用量...为深入了解煤泥浮选过程中硅酸钠对黏土矿物的选择性抑制机理,以煤和高岭石为研究对象,通过单矿物浮选试验、Zeta电位测定、X射线光电子能谱(XPS)分析,研究了硅酸钠对煤和高岭石浮选行为的影响。试验结果表明:p H值在7左右、硅酸钠用量为1 000 g/t时,煤和高岭石的分离效果最好,煤的可燃体回收率可达60.44%,灰分为8.03%;硅酸钠使煤和高岭石表面电位负移,增大了矿物间的静电斥力,p H值为中性时,煤和高岭石表面电位分别降低了6 m V和16 m V;XPS分析结果显示,与硅酸钠作用后,煤与高岭石表面Si原子相对含量增加,并且硅原子2P原子轨道(Si 2p)结合能变化值分别为-0.02、-0.19 e V,证明了硅酸钠在煤和高岭石表面的吸附为物理吸附,吸附量的不同是造成硅酸钠选择性抑制的主要原因。展开更多
Clays are among the most essential industrial minerals due to their unique physicochemical properties and versatile usage. This paper used Statistical Package for Social Sciences (SPSS) software to characterize five c...Clays are among the most essential industrial minerals due to their unique physicochemical properties and versatile usage. This paper used Statistical Package for Social Sciences (SPSS) software to characterize five clay deposits for their physical and chemical compositions. The package, was employed to carry out the Analysis of Variance (ANOVA) by Post-Hoctambane multiple comparisons and Kristal Wallis at 5% confidence level for the f- and t-tests respectively. The analysis of variance of the chemical components of the samples by post-hoc (f8, 36 = 52.40, p 8, 37.38 and p 2 and Al2O3. Pearson bivariate correlation statistical tool was also used to establish if significant positive interrelationships exist between the parameters in each site of the clay samples at (p < 0.01 and p < 0.05). The result of the correlation indicates a very significant, strong and positive coefficient p-values above 0.900 between the chemical and physicalproperties. Pearson bivariate correlation coefficient between the chemical and physical parameters of the clay samples indicates very significant, strong and positive correlations with p-values above 0.900 at (p < 0.01 and <0.05). The overall physicochemical results indicate that most of the clay samples will meet the requirements for some industrial applications with minimal processing.展开更多
The interface electrochemical properties of clay were theoretically analyzed to obtain some relationships among point of zero net charge （PZNC）, point of zero net proton charge （PZNPC）, intrinsic surface reaction ...The interface electrochemical properties of clay were theoretically analyzed to obtain some relationships among point of zero net charge （PZNC）, point of zero net proton charge （PZNPC）, intrinsic surface reaction equilibrium constants （K in 1-pK model, Ka1^int and Ka2^int in 2-pK model, ＊KNa^int and ＊KNO3^int in inert electrolyte chemical binding model） and structural negative charge density （σst） of clay, and some interface electrochemical parameters of kaolinite were measured. The following main conclusions were obtained. For clay possessing structural negative charges, the PZNC independent of electrolyte concentration （c） should exist just as amphoteric solid without structural charges such as oxides or hydroxides. A common intersection point （CIP） should appear among the potentiometric （or acid-base） titration curves at different c and the pH at the CIP should be PHPZNC. A CIP among potentiometric titration curves at different c for kaolinite was observed, and the value of PHPZNC of kaolinite was 2.16. The values of pHPZNPC were decreased with increasing c, which arises from the presence of structural negative charges of kaolinite. In addition, it was observed that a good linear relationship existed between pHPZNPC and 1g c. According to the values of PHPZNC and σst measured, the intrinsic surface reaction equilibrium constants, pK and pKa1^int and pKa2^int of 1-pK and 2-pK models could be directly calculated for clay, and the values of pK, pKa1^int and pKa2^int for kaolinite were 2.93, 1.90 and 3.97, respectively. These experimental values of pKa1^int and pKa2^int for kaolinite are obviously lower than those optimized with fitting programs in literatures, which maybe arises from the introduction of a type of permanent negatively charged sites in the models of literatures. An interesting result obtained in this study is that the inert electrolyte chemical binding does not exist for kaolinite, which also arises from the presence of structural negative charges.展开更多
Denatonium benzoate is an aversive agent proposed for use in certain anti-freeze formulations to reduce poisoning events of pets and humans. Unfortunately, the sorption properties of denatonium cations to soil and/or ...Denatonium benzoate is an aversive agent proposed for use in certain anti-freeze formulations to reduce poisoning events of pets and humans. Unfortunately, the sorption properties of denatonium cations to soil and/or soil components have not been investigated. In this paper, denatonium sorption to reference kaolinite clay under varied pH, ionic strength, and cation identity is described. The data clearly indicate that the nature of the background electrolyte cation modulates denatonium sorption with enhanced sorption occurring the presence of potassium ions versus minimal sorption occurring in a calcium chloride electrolyte at each pH studied as estimated using Dubinin-Raduskevich (D-R) isotherms. The effect of background electrolyte concentration on sorption was consistent with an ion-exchange process wherein the sorption capacity increased with decreased background electrolyte concentration. An interesting and unexpected observation of increased sorption capacity (estimated using the D-R model) with decreasing pH was observed in 10 mM CaCl2 in contrast to an observed and expected increase in denatonium sorption to kaolinite in the presence of either of 10 mM NaCl or 10 mM KCl. Estimates of the mean sorption energy using D-R isotherms ranging from 2.65 kJ/mol in 10 mM CaCl2 at pH 4 to 4.68 kJ/mol at pH 10 suggesting that the sorption process is not exclusively ion-exchange.展开更多
Nigeria is the highest consumer of aluminium in Africa but lacks bauxite deposits. The replacement of bauxite alumina with other alumina bearing resources (clays in particular) has been proposed. The present study inv...Nigeria is the highest consumer of aluminium in Africa but lacks bauxite deposits. The replacement of bauxite alumina with other alumina bearing resources (clays in particular) has been proposed. The present study investigated the thermal treatment required to activate Edda clay from southeastern Nigeria for optimal leaching of alumina. The clay is composed mainly of kaolinite and quartz, assaying 24.65% Al2O3 and 52.81% SiO2. Thermal activation of the clay prior to leaching transformed the crystalline kaolinite mineral to an amorphous phase (metakaolinite) in which the alumina became soluble. Clay samples passing 300 μm sieve were calcined at temperatures of 500°C, 600°C, 700°C, 800°C, and 900°C at holding times of 30, 60, and 90 minutes in each case. The uncalcined clay and sample heated at 1000°C (for 60 minutes) were used in the control experiments. Leaching of alumina from the resulting clay calcines was done in 1 M hydrochloric acid solution at room temperature using a solid/liquid ratio of 0.02 g/ml and shaking speed of 100 rpm. The solubility data based on the percentage of Al ions taken into leach solution showed that the sample calcined at 700°C (for 60 minutes) responded to leaching better than other samples. Samples calcined for 60 minutes at all temperatures studied were found to respond more than those held for 30 or 90 minutes. Studies on the activation energy of leaching revealed that calcines produced at 700°C (for 60 minutes) had both the highest leaching response (49.96% after 1 hour at leaching temperature of 100°C) and the lowest activation energy of 24.47 kJ/mol. It is concluded therefore that Edda kaolinite clay should be thermally activated for alumina yield by heating up to 700°C and holding for 60 minutes. The clay deposit is therefore a potential alternative resource for alumina production.展开更多
文摘To meet the ever-increasing construction demands around the world during recent years,reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of fine-grained soils.Although lime stabilization increases the compressive strength of soils,it reduces the soil ductility at the same time.Recent research shows that random fiber inclusion modifies the brittleness of soils.In the current research,the effects of lime and polypropylene(PP)fiber additions on such characteristics as compressive and shear strengths,failure strain,secant modulus of elasticity(E50)and shear strength parameters of mixtures were investigated.Kaolinite was treated with 1%,3% and 5% lime by dry weight of soil and reinforced with 0.1% monovalent PP fibers with the length of 6 mm.Samples were prepared at optimum conditions and cured at 35℃ for 1 d,7 d and 28 d at 90% relative humidity and subsequently subjected to uniaxial and triaxial compression tests(UCT and TCT)under cell pressures of 25 kPa,50 kPa and 100 kPa.Results showed that inclusion of random PP fibers to clay-lime mixtures increases both compressive and shear strengths as well as the ductility.Lime content and curing period were found to be the most influential factors.Scanning electron microscopy(SEM)analysis showed that lime addition and the formation of cementitious compounds bind soil particles and increase soil/fiber interactions at interface,leading to enhanced shear strength.The more ductile the stabilized and reinforced composition,the less the cracks in roads and waste landfill covers.
基金funded by the Guizhou Geological exploration fund (No. [2015]21)the Guizhou Geological mineral science cooperation fund (Nos. [2015]5, [2016]5, [2017]1092)
文摘We studied the states of rare earth elements in ore of the Xianglushan rare earth deposit. Rare earth ore samples were tested and examined by scanning electron microscope, electron probe, and chemical leaching. No independent rare earth minerals were detected by scanning electron microscope. Elements detected by the electronic probe for the in situ micro-zone of the sample included: O,Al, Si, Ca, Mg, Fe, Ti, K, Na, S, Cl, C, Cu, Cr, V, and Pt.Rare earth elements were not detected by electron probe.(NH_4)_2 SO_4,(NH_4)Cl, NaCl, and H_2 SO_4 were used as reagents in chemical leaching experiments that easily leached out rare earth elements under the action of 10%reagent, indicating that the rare earth elements in ore are mainly in the ionic state rather than present as rare earth minerals.
文摘Geopolymers are an alternative to Portland cement, well known for their contribution to greenhouse gas emissions. Finding materials that can validly replace Portland cement is a challenge. It is in this logic that this work was undertaken with the objective of characterizing two local clay resources of Togo as raw materials for geopolymers. The physico-chemical properties of these clays were determined by characterization using X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric (TGA) and elemental analysis (ICP-OES). The results show that these clays contain kaolinite and therefore can be used in the formulation of geopolymers. The characterized clays underwent heat treatments transforming the crystalline phases into more reactive amorphous phases and then were activated by an alkaline solution in order to formulate the geopolymer materials. These elaborated materials were analyzed by Fourier transform infrared to identify the types of bonds formed. The results of these analyses show that these two local clays are well suited to be used in synthesizing geopolymers. Our future work will focus on the constraints of consolidation as well as the mechanical properties of these geopolymer materials.
文摘In order to contribute to the valorisation of the clay materials of Ivory Coast in the depollution of wastewater, the physicochemical and mineralogical characterization of three clay samples taken in Agboville (AGB), Bingerville (BIN) and Katiola (KAT) was carried out. The objective of this work was to compare the properties of the clays in order to identify the one that is likely to have interesting adsorptive capacities to clean up contaminated water. These clays were studied by chemical analysis, X-ray diffraction, scanning electron microscopy and thermal analysis. In addition, their specific surface areas and cation exchange capacities were determined. The AGB clay is composed of 75.51% kaolinite, 14.20% illite and 9.26% quartz. The BIN clay contains 52.21% kaolinite, 6.23% illite, 17.50% quartz and 15.71% goethite. As for the KAT clay, it contains 48.08% kaolinite, 3.55% illite, 20.14% smectite, 6.11% quartz and 16.86% goethite. Their thermal behavior and microstructure are in agreement with their mineralogy. The measured specific surface areas and cation exchange capacities are consistent with literature values. The KAT clay has the highest specific surface and cation exchange capacity. In the light of the results obtained, the KAT clay appears to be more effective in depolluting water than the BIN and AGB clays.
文摘为深入了解煤泥浮选过程中硅酸钠对黏土矿物的选择性抑制机理,以煤和高岭石为研究对象,通过单矿物浮选试验、Zeta电位测定、X射线光电子能谱(XPS)分析,研究了硅酸钠对煤和高岭石浮选行为的影响。试验结果表明:p H值在7左右、硅酸钠用量为1 000 g/t时,煤和高岭石的分离效果最好,煤的可燃体回收率可达60.44%,灰分为8.03%;硅酸钠使煤和高岭石表面电位负移,增大了矿物间的静电斥力,p H值为中性时,煤和高岭石表面电位分别降低了6 m V和16 m V;XPS分析结果显示,与硅酸钠作用后,煤与高岭石表面Si原子相对含量增加,并且硅原子2P原子轨道(Si 2p)结合能变化值分别为-0.02、-0.19 e V,证明了硅酸钠在煤和高岭石表面的吸附为物理吸附,吸附量的不同是造成硅酸钠选择性抑制的主要原因。
文摘Clays are among the most essential industrial minerals due to their unique physicochemical properties and versatile usage. This paper used Statistical Package for Social Sciences (SPSS) software to characterize five clay deposits for their physical and chemical compositions. The package, was employed to carry out the Analysis of Variance (ANOVA) by Post-Hoctambane multiple comparisons and Kristal Wallis at 5% confidence level for the f- and t-tests respectively. The analysis of variance of the chemical components of the samples by post-hoc (f8, 36 = 52.40, p 8, 37.38 and p 2 and Al2O3. Pearson bivariate correlation statistical tool was also used to establish if significant positive interrelationships exist between the parameters in each site of the clay samples at (p < 0.01 and p < 0.05). The result of the correlation indicates a very significant, strong and positive coefficient p-values above 0.900 between the chemical and physicalproperties. Pearson bivariate correlation coefficient between the chemical and physical parameters of the clay samples indicates very significant, strong and positive correlations with p-values above 0.900 at (p < 0.01 and <0.05). The overall physicochemical results indicate that most of the clay samples will meet the requirements for some industrial applications with minimal processing.
基金Project supported by National Key Basic Research Program of China （No. 2004CB418504）, the National Natural Science Foundation of China （No. 20573065） and the Natural Science Foundation of Shandong Province of China （No. Z2005B02）.
文摘The interface electrochemical properties of clay were theoretically analyzed to obtain some relationships among point of zero net charge （PZNC）, point of zero net proton charge （PZNPC）, intrinsic surface reaction equilibrium constants （K in 1-pK model, Ka1^int and Ka2^int in 2-pK model, ＊KNa^int and ＊KNO3^int in inert electrolyte chemical binding model） and structural negative charge density （σst） of clay, and some interface electrochemical parameters of kaolinite were measured. The following main conclusions were obtained. For clay possessing structural negative charges, the PZNC independent of electrolyte concentration （c） should exist just as amphoteric solid without structural charges such as oxides or hydroxides. A common intersection point （CIP） should appear among the potentiometric （or acid-base） titration curves at different c and the pH at the CIP should be PHPZNC. A CIP among potentiometric titration curves at different c for kaolinite was observed, and the value of PHPZNC of kaolinite was 2.16. The values of pHPZNPC were decreased with increasing c, which arises from the presence of structural negative charges of kaolinite. In addition, it was observed that a good linear relationship existed between pHPZNPC and 1g c. According to the values of PHPZNC and σst measured, the intrinsic surface reaction equilibrium constants, pK and pKa1^int and pKa2^int of 1-pK and 2-pK models could be directly calculated for clay, and the values of pK, pKa1^int and pKa2^int for kaolinite were 2.93, 1.90 and 3.97, respectively. These experimental values of pKa1^int and pKa2^int for kaolinite are obviously lower than those optimized with fitting programs in literatures, which maybe arises from the introduction of a type of permanent negatively charged sites in the models of literatures. An interesting result obtained in this study is that the inert electrolyte chemical binding does not exist for kaolinite, which also arises from the presence of structural negative charges.
文摘Denatonium benzoate is an aversive agent proposed for use in certain anti-freeze formulations to reduce poisoning events of pets and humans. Unfortunately, the sorption properties of denatonium cations to soil and/or soil components have not been investigated. In this paper, denatonium sorption to reference kaolinite clay under varied pH, ionic strength, and cation identity is described. The data clearly indicate that the nature of the background electrolyte cation modulates denatonium sorption with enhanced sorption occurring the presence of potassium ions versus minimal sorption occurring in a calcium chloride electrolyte at each pH studied as estimated using Dubinin-Raduskevich (D-R) isotherms. The effect of background electrolyte concentration on sorption was consistent with an ion-exchange process wherein the sorption capacity increased with decreased background electrolyte concentration. An interesting and unexpected observation of increased sorption capacity (estimated using the D-R model) with decreasing pH was observed in 10 mM CaCl2 in contrast to an observed and expected increase in denatonium sorption to kaolinite in the presence of either of 10 mM NaCl or 10 mM KCl. Estimates of the mean sorption energy using D-R isotherms ranging from 2.65 kJ/mol in 10 mM CaCl2 at pH 4 to 4.68 kJ/mol at pH 10 suggesting that the sorption process is not exclusively ion-exchange.
文摘Nigeria is the highest consumer of aluminium in Africa but lacks bauxite deposits. The replacement of bauxite alumina with other alumina bearing resources (clays in particular) has been proposed. The present study investigated the thermal treatment required to activate Edda clay from southeastern Nigeria for optimal leaching of alumina. The clay is composed mainly of kaolinite and quartz, assaying 24.65% Al2O3 and 52.81% SiO2. Thermal activation of the clay prior to leaching transformed the crystalline kaolinite mineral to an amorphous phase (metakaolinite) in which the alumina became soluble. Clay samples passing 300 μm sieve were calcined at temperatures of 500°C, 600°C, 700°C, 800°C, and 900°C at holding times of 30, 60, and 90 minutes in each case. The uncalcined clay and sample heated at 1000°C (for 60 minutes) were used in the control experiments. Leaching of alumina from the resulting clay calcines was done in 1 M hydrochloric acid solution at room temperature using a solid/liquid ratio of 0.02 g/ml and shaking speed of 100 rpm. The solubility data based on the percentage of Al ions taken into leach solution showed that the sample calcined at 700°C (for 60 minutes) responded to leaching better than other samples. Samples calcined for 60 minutes at all temperatures studied were found to respond more than those held for 30 or 90 minutes. Studies on the activation energy of leaching revealed that calcines produced at 700°C (for 60 minutes) had both the highest leaching response (49.96% after 1 hour at leaching temperature of 100°C) and the lowest activation energy of 24.47 kJ/mol. It is concluded therefore that Edda kaolinite clay should be thermally activated for alumina yield by heating up to 700°C and holding for 60 minutes. The clay deposit is therefore a potential alternative resource for alumina production.
