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
Coordination compounds of modified diamine,the basic unit of which are ethylenediamine,with that of Co(Ⅱ)are prepared.The modified diamines are ethylenediaceticacid(EDDA)and N,N,N,N-tetaraethylene-1,2-diamine(TEEDA)....Coordination compounds of modified diamine,the basic unit of which are ethylenediamine,with that of Co(Ⅱ)are prepared.The modified diamines are ethylenediaceticacid(EDDA)and N,N,N,N-tetaraethylene-1,2-diamine(TEEDA).These diamines are characterized through ^(1)H-NMR,^(13)C-NMR,elemental analysis and IR techniques.Cobalt(Ⅱ)complexes of these two ligands were prepared and characterized by physical measurements including elemental analysis,IR,UVVisible,magnetic susceptibilities and conductance measurements.Antibacterial activities are also carried out in order to investigate the biological activity upon complexation.They were screened against four pathogenic bacteria like Escherichia coli,Pseudomonas aeroginosa,Klesbella pneumonia and Staphylococcus aureus.The results showed significant enhancement in activities.展开更多
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.
文摘Coordination compounds of modified diamine,the basic unit of which are ethylenediamine,with that of Co(Ⅱ)are prepared.The modified diamines are ethylenediaceticacid(EDDA)and N,N,N,N-tetaraethylene-1,2-diamine(TEEDA).These diamines are characterized through ^(1)H-NMR,^(13)C-NMR,elemental analysis and IR techniques.Cobalt(Ⅱ)complexes of these two ligands were prepared and characterized by physical measurements including elemental analysis,IR,UVVisible,magnetic susceptibilities and conductance measurements.Antibacterial activities are also carried out in order to investigate the biological activity upon complexation.They were screened against four pathogenic bacteria like Escherichia coli,Pseudomonas aeroginosa,Klesbella pneumonia and Staphylococcus aureus.The results showed significant enhancement in activities.
