Adsorption of Cu and Ni from AMD using activated bentonite
- Ntuli, Freeman, Falayi, Thabo, Molala, Panelope
- Authors: Ntuli, Freeman , Falayi, Thabo , Molala, Panelope
- Date: 2014
- Subjects: Bentonite , Copper adsorption , Langmuir kinetic models , Nickel adsorption
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/387938 , uj:4901 , ISSN 2349-1442 , http://hdl.handle.net/10210/12996
- Description: The ability of activated bentonite to adsorb Cu and Ni was investigated. 6 % solid loading was chosen as the optimum solid loading for activated bentonite with 94.85% Cu and 92.05% Ni removal after 3 hours of agitation. The adsorption process followed the Langmuir isotherm and pseudo second order kinetic models. The maximum adsorption capacities were 0.297 and 0.235 mg/g for Cu and Ni respectively. The adsorption of Cu and Ni was thermodynamically spontaneous. Cu adsorption was endothermic whilst Ni adsorption was exothermic. Activated bentonite could be used for two cycles of adsorption without regeneration.
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- Authors: Ntuli, Freeman , Falayi, Thabo , Molala, Panelope
- Date: 2014
- Subjects: Bentonite , Copper adsorption , Langmuir kinetic models , Nickel adsorption
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/387938 , uj:4901 , ISSN 2349-1442 , http://hdl.handle.net/10210/12996
- Description: The ability of activated bentonite to adsorb Cu and Ni was investigated. 6 % solid loading was chosen as the optimum solid loading for activated bentonite with 94.85% Cu and 92.05% Ni removal after 3 hours of agitation. The adsorption process followed the Langmuir isotherm and pseudo second order kinetic models. The maximum adsorption capacities were 0.297 and 0.235 mg/g for Cu and Ni respectively. The adsorption of Cu and Ni was thermodynamically spontaneous. Cu adsorption was endothermic whilst Ni adsorption was exothermic. Activated bentonite could be used for two cycles of adsorption without regeneration.
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Desilication of fly ash and geotechnical applications of the desilicated fly ash
- Authors: Falayi, Thabo
- Date: 2016
- Subjects: Geotechnical engineering , Engineering geology , Soil stabilization , Fly ash
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/233013 , uj:23780
- Description: D.Phil. (Civil Engineering Science) , Abstract: Silica was leached from fly ash (FA) produced by Camden power station (South Africa). The residue, desilicated fly ash (DFA) was then stabilised using lime and alkaline activation. The stabilised residue was then used as a soil stabiliser. Camden FA was found to have a basic pH (10.7) whilst DFA was more basic (12.3) due to a higher K2O content.The major difference between DFA and FA was the presence of a zeolite (Phillipsite K) in DFA. Radiological analysis showed that the activity concentrations of 226Ra, 232Th and 40K for both DFA and FA were below the limits of the South African Government Gazette of 2006. Silica was leached from FA using KOH. The leaching parameters investigated were leaching time, KOH concentration, agitation speed, FA particle size, leaching temperature and liquid solid ratio (L/S). It was found that the optimum leaching conditions were leaching time of 6 h, 3 M KOH, 500 rpm agitation speed, 25 L/S ratio, leaching temperature of 100˚C. The yield was found to be 283.7 g of silica per kg of FA. Silica leaching followed a modified Jander equation kinetics with an N value of 1.48 and an activation energy of 5.9 kJ/mol. DFA was stabilised using lime at elevated temperatures. DFA and lime were mixed in different ratios at optimum moisture content and maximum dry density and then cured at 40ºC, 80ºC and 100ºC for 4 days. 80ºC was found to be the optimum curing temperature. The DFA: lime ratio of 70:30 was found to have an average UCS of 8.8 MPa. Lime consumption was found to follow modified Jander kinetics with activation energy of 16 kJ/mol. Toxicity leaching tests showed a 79% reduction in the leachability of trace and heavy metals. The composite met the minimum requirement of ASTM C34-13 and South African burnt clay standard (SANS227:2007). The influence of open porosity, sum of hydration products and extent of DFA hydration on the strength of DFA lime composites was also studied. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of fly ash/desilicated fly ash hydration and sum of hydration products) had the greatest influence on the UCS than individually with correlation coefficients above 0.98. The use of DFA-lime composite as a stabiliser for expansive soil was also studied. A 70:30 DFA: lime composite was used as the stabiliser. The 30% stabilised soil was found to have a UCS of 4.1 MPa. The stabilised soil met the minimum requirements for the American Concrete Institute’s requirements for backfill material. A 40% addition of FA: lime composite was the optimum for the stabilisation of the same expansive soil. DFA composite stabilisation was better than the FA composite stabilisation due to a superior UCS (4.1 vs 2.62 MPa), better 24 h soak UCS (3.62 vs 0.98 MPa) and a better saturation coefficient 0.35 vs 0.68...
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- Authors: Falayi, Thabo
- Date: 2016
- Subjects: Geotechnical engineering , Engineering geology , Soil stabilization , Fly ash
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/233013 , uj:23780
- Description: D.Phil. (Civil Engineering Science) , Abstract: Silica was leached from fly ash (FA) produced by Camden power station (South Africa). The residue, desilicated fly ash (DFA) was then stabilised using lime and alkaline activation. The stabilised residue was then used as a soil stabiliser. Camden FA was found to have a basic pH (10.7) whilst DFA was more basic (12.3) due to a higher K2O content.The major difference between DFA and FA was the presence of a zeolite (Phillipsite K) in DFA. Radiological analysis showed that the activity concentrations of 226Ra, 232Th and 40K for both DFA and FA were below the limits of the South African Government Gazette of 2006. Silica was leached from FA using KOH. The leaching parameters investigated were leaching time, KOH concentration, agitation speed, FA particle size, leaching temperature and liquid solid ratio (L/S). It was found that the optimum leaching conditions were leaching time of 6 h, 3 M KOH, 500 rpm agitation speed, 25 L/S ratio, leaching temperature of 100˚C. The yield was found to be 283.7 g of silica per kg of FA. Silica leaching followed a modified Jander equation kinetics with an N value of 1.48 and an activation energy of 5.9 kJ/mol. DFA was stabilised using lime at elevated temperatures. DFA and lime were mixed in different ratios at optimum moisture content and maximum dry density and then cured at 40ºC, 80ºC and 100ºC for 4 days. 80ºC was found to be the optimum curing temperature. The DFA: lime ratio of 70:30 was found to have an average UCS of 8.8 MPa. Lime consumption was found to follow modified Jander kinetics with activation energy of 16 kJ/mol. Toxicity leaching tests showed a 79% reduction in the leachability of trace and heavy metals. The composite met the minimum requirement of ASTM C34-13 and South African burnt clay standard (SANS227:2007). The influence of open porosity, sum of hydration products and extent of DFA hydration on the strength of DFA lime composites was also studied. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of fly ash/desilicated fly ash hydration and sum of hydration products) had the greatest influence on the UCS than individually with correlation coefficients above 0.98. The use of DFA-lime composite as a stabiliser for expansive soil was also studied. A 70:30 DFA: lime composite was used as the stabiliser. The 30% stabilised soil was found to have a UCS of 4.1 MPa. The stabilised soil met the minimum requirements for the American Concrete Institute’s requirements for backfill material. A 40% addition of FA: lime composite was the optimum for the stabilisation of the same expansive soil. DFA composite stabilisation was better than the FA composite stabilisation due to a superior UCS (4.1 vs 2.62 MPa), better 24 h soak UCS (3.62 vs 0.98 MPa) and a better saturation coefficient 0.35 vs 0.68...
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Absorption of heavy metals and neutralisation of acid mine drainage using clay minerals
- Authors: Falayi, Thabo
- Date: 2014-06-04
- Subjects: Acid main drainage - Purification , Water - Purification - Adsorption , Clay
- Type: Thesis
- Identifier: uj:11389 , http://hdl.handle.net/10210/11027
- Description: M.Tech. (Chemical Engineering) , Please refer to full text to view abstract
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- Authors: Falayi, Thabo
- Date: 2014-06-04
- Subjects: Acid main drainage - Purification , Water - Purification - Adsorption , Clay
- Type: Thesis
- Identifier: uj:11389 , http://hdl.handle.net/10210/11027
- Description: M.Tech. (Chemical Engineering) , Please refer to full text to view abstract
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Adsorption, kinetic and thermodynamic study of Al, Mn and Fe adsorption with natural attapulgite
- Ntuli, Freeman, Falayi, Thabo, Mabasa, Cyril
- Authors: Ntuli, Freeman , Falayi, Thabo , Mabasa, Cyril
- Date: 2015
- Subjects: Attapulgite , Aluminum , Manganese , Iron , Adsorption
- Type: Article
- Identifier: uj:5126 , ISBN 978-1-61804-270-5 , http://hdl.handle.net/10210/14089
- Description: Natural attapulgite was utilized as an adsorbent for the removal of Al, Fe and Mn from a mixed metal effluent. Adsorption experiments were carried out by agitation of a fixed amount of attapulgite with a fixed volume of effluent waste stream in a thermostatic shaker for varying times. Attapulgite showed that it was capable of neutralising the acidic waste stream effluent as pH after 3 hour rose from 2 to 7.46. 4% solid loading of attapulgite could remove 85% Mn(II), 90% Al(III) and 100% Fe(III) The experimental data best fit Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models and the adsorption mechanism was physisorption. The adsorption process fitted well the pseudo second order kinetics for all metal ions studied. Thermodynamic data showed that Fe(III) and Mn(II) adsorption was thermodynamically spontaneous whilst Al(III) was not thermodynamically spontaneous. The process is endothermic for all metal ions. An increase in temperature resulted in an increase in spontaneity of the adsorption process. An increase in metal concentration resulted in an increase in amount of metal ion adsorbed per unit weight of attapulgite.
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- Authors: Ntuli, Freeman , Falayi, Thabo , Mabasa, Cyril
- Date: 2015
- Subjects: Attapulgite , Aluminum , Manganese , Iron , Adsorption
- Type: Article
- Identifier: uj:5126 , ISBN 978-1-61804-270-5 , http://hdl.handle.net/10210/14089
- Description: Natural attapulgite was utilized as an adsorbent for the removal of Al, Fe and Mn from a mixed metal effluent. Adsorption experiments were carried out by agitation of a fixed amount of attapulgite with a fixed volume of effluent waste stream in a thermostatic shaker for varying times. Attapulgite showed that it was capable of neutralising the acidic waste stream effluent as pH after 3 hour rose from 2 to 7.46. 4% solid loading of attapulgite could remove 85% Mn(II), 90% Al(III) and 100% Fe(III) The experimental data best fit Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models and the adsorption mechanism was physisorption. The adsorption process fitted well the pseudo second order kinetics for all metal ions studied. Thermodynamic data showed that Fe(III) and Mn(II) adsorption was thermodynamically spontaneous whilst Al(III) was not thermodynamically spontaneous. The process is endothermic for all metal ions. An increase in temperature resulted in an increase in spontaneity of the adsorption process. An increase in metal concentration resulted in an increase in amount of metal ion adsorbed per unit weight of attapulgite.
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Influence of open porosity, hydration products and extent of hydration on the strength of desilicated lime fly ash composites
- Falayi, Thabo, Okonta, Felix Ndubisi, Ntuli, Freeman
- Authors: Falayi, Thabo , Okonta, Felix Ndubisi , Ntuli, Freeman
- Date: 2017
- Subjects: Multivariate analysis , Hydration products , Open porosity
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/249019 , uj:25908 , Citation: Falayi, T., Okonta, F.N. & Ntuli, F. 2017. Influence of open porosity, hydration products and extent of hydration on the strength of desilicated lime fly ash composites.
- Description: Abstract: The prediction of strength of lime ash composites is critical for quality control, material performance monitoring and material serviceability limit state. A study was conducted to investigate the influence of open porosity (an index of micro grain alignment and macro particle parking), sum of hydration products and extent of hydration of desilicated fly ash (DFA) on the unconfined compressive strength (UCS) of DFA lime composites. A comparison with as received fly ash (FA) was also done. The wet and dry cycle durability of DFA and as received FA composites was also investigated. The DFA and FA composites were found to have a UCS of 8.6 MPa and 7.9 MPa respectively. The FA composite was found to be more durable than the DFA composite as after 10 wet and dry cycles the composites had a UCS of 3.5 and 1.8 MPa respectively. Statistical correlation between UCS and open porosity, extent of FA/DFA hydration and sum of hydration products was implemented by Multivariate analysis. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of FA/DFA hydration and sum of hydration products) had the greatest influence on the UCS than individually. This study shows that no single parameter on its own can adequately be used to predict UCS of FA/DFA lime composites. Correlation coefficients above 0.98 were found to describe the relationship between the three parameters and UCS for each composite. Thus could account for differences in durability or soaked strength of materials with equal initial dry strength.
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- Authors: Falayi, Thabo , Okonta, Felix Ndubisi , Ntuli, Freeman
- Date: 2017
- Subjects: Multivariate analysis , Hydration products , Open porosity
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/249019 , uj:25908 , Citation: Falayi, T., Okonta, F.N. & Ntuli, F. 2017. Influence of open porosity, hydration products and extent of hydration on the strength of desilicated lime fly ash composites.
- Description: Abstract: The prediction of strength of lime ash composites is critical for quality control, material performance monitoring and material serviceability limit state. A study was conducted to investigate the influence of open porosity (an index of micro grain alignment and macro particle parking), sum of hydration products and extent of hydration of desilicated fly ash (DFA) on the unconfined compressive strength (UCS) of DFA lime composites. A comparison with as received fly ash (FA) was also done. The wet and dry cycle durability of DFA and as received FA composites was also investigated. The DFA and FA composites were found to have a UCS of 8.6 MPa and 7.9 MPa respectively. The FA composite was found to be more durable than the DFA composite as after 10 wet and dry cycles the composites had a UCS of 3.5 and 1.8 MPa respectively. Statistical correlation between UCS and open porosity, extent of FA/DFA hydration and sum of hydration products was implemented by Multivariate analysis. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of FA/DFA hydration and sum of hydration products) had the greatest influence on the UCS than individually. This study shows that no single parameter on its own can adequately be used to predict UCS of FA/DFA lime composites. Correlation coefficients above 0.98 were found to describe the relationship between the three parameters and UCS for each composite. Thus could account for differences in durability or soaked strength of materials with equal initial dry strength.
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Thermally activated attapulgite as an adsorbent for heavy metals
- Ntuli, Freeman, Falayi, Thabo, Dlamini, Thabani
- Authors: Ntuli, Freeman , Falayi, Thabo , Dlamini, Thabani
- Date: 2013
- Subjects: Adsorption , Attapulgite , Heavy metals , Langmuir isotherm
- Type: Article
- Identifier: uj:4854 , http://hdl.handle.net/10210/12530
- Description: Thermal activation of attapulgite was investigated. Attapulgite calcined at 6000C was used as an adsorbent for heavy metals in AMD. The effect of solid loading, residence time and adsorption temperature was investigated. Activated attapulgite showed that it could remove more than 99% of Fe, Cu, Co and Ni from AMD. Langmuir isotherm gave the best fit for the adsorption process with maximum adsorption capacities of 8.97, 0.20, 0.32 and 0.32 for Fe, Ni, Cu and Co respectively. The adsorption of Cu and Ni was thermodynamically. The results show that thermally activated attapulgite has potential as an adsorbent for heavy metals from AMD.
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- Authors: Ntuli, Freeman , Falayi, Thabo , Dlamini, Thabani
- Date: 2013
- Subjects: Adsorption , Attapulgite , Heavy metals , Langmuir isotherm
- Type: Article
- Identifier: uj:4854 , http://hdl.handle.net/10210/12530
- Description: Thermal activation of attapulgite was investigated. Attapulgite calcined at 6000C was used as an adsorbent for heavy metals in AMD. The effect of solid loading, residence time and adsorption temperature was investigated. Activated attapulgite showed that it could remove more than 99% of Fe, Cu, Co and Ni from AMD. Langmuir isotherm gave the best fit for the adsorption process with maximum adsorption capacities of 8.97, 0.20, 0.32 and 0.32 for Fe, Ni, Cu and Co respectively. The adsorption of Cu and Ni was thermodynamically. The results show that thermally activated attapulgite has potential as an adsorbent for heavy metals from AMD.
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Kinetic and thermodynamic parameters of silica leaching from Camden power station fly ash
- Falayi, Thabo, Ntuli, Freeman, Okonta, Felix Ndubisi
- Authors: Falayi, Thabo , Ntuli, Freeman , Okonta, Felix Ndubisi
- Date: 2015
- Subjects: Fly ash , Leaching , Potassium silicate , Silicate leaching
- Type: Article
- Identifier: uj:5142 , ISBN 978-1-61804-270-5 , http://hdl.handle.net/10210/14120
- Description: Fly ash from a South African power station ash dam was used. The fly ash approximated Class F fly ash but had a loss on ignition greater than 6%. The leaching parameters investigated were leaching time, KOH concentration, agitation speed, fly ash particle size, leaching temperature and liquid solid ratio (L/S). It was found that the optimum leaching conditions were leaching time of 6 h, 3M KOH, 500 rpm agitation speed, 25 L/S ratio, leaching temperature of 100˚C. Silica leaching followed a modified Jander equation kinetics with an N value of 1.48 and an activation energy of 5.9 kJ/mol.
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- Authors: Falayi, Thabo , Ntuli, Freeman , Okonta, Felix Ndubisi
- Date: 2015
- Subjects: Fly ash , Leaching , Potassium silicate , Silicate leaching
- Type: Article
- Identifier: uj:5142 , ISBN 978-1-61804-270-5 , http://hdl.handle.net/10210/14120
- Description: Fly ash from a South African power station ash dam was used. The fly ash approximated Class F fly ash but had a loss on ignition greater than 6%. The leaching parameters investigated were leaching time, KOH concentration, agitation speed, fly ash particle size, leaching temperature and liquid solid ratio (L/S). It was found that the optimum leaching conditions were leaching time of 6 h, 3M KOH, 500 rpm agitation speed, 25 L/S ratio, leaching temperature of 100˚C. Silica leaching followed a modified Jander equation kinetics with an N value of 1.48 and an activation energy of 5.9 kJ/mol.
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Extraction and precipitation of phosphorous from sewage sludge : a feasibility study.
- Ntuli, Freeman, Falayi, Thabo, Mhlungu, Mbalenhle, Thifhelimbilu, Portia
- Authors: Ntuli, Freeman , Falayi, Thabo , Mhlungu, Mbalenhle , Thifhelimbilu, Portia
- Date: 2013
- Subjects: Sewage sludge , Phosphorous
- Type: Article
- Identifier: uj:4855 , http://hdl.handle.net/10210/12531
- Description: Sewage sludge from ERWAT (East Rand Water Care Company) was investigated to determine its potential as a source of P. The raw sewage sludge was found to be a potential source of P. At least 84% P could be leached from the raw sewage sludge after 60 min using either HCl or H2SO4. Selective precipitation of P as magnesium tetraphosphate could be achieved using ammonia and magnesium oxide to give yield a 92.2% pure magnesium tetraphosphate and 9.8% P.
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- Authors: Ntuli, Freeman , Falayi, Thabo , Mhlungu, Mbalenhle , Thifhelimbilu, Portia
- Date: 2013
- Subjects: Sewage sludge , Phosphorous
- Type: Article
- Identifier: uj:4855 , http://hdl.handle.net/10210/12531
- Description: Sewage sludge from ERWAT (East Rand Water Care Company) was investigated to determine its potential as a source of P. The raw sewage sludge was found to be a potential source of P. At least 84% P could be leached from the raw sewage sludge after 60 min using either HCl or H2SO4. Selective precipitation of P as magnesium tetraphosphate could be achieved using ammonia and magnesium oxide to give yield a 92.2% pure magnesium tetraphosphate and 9.8% P.
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Durability of desilicated fly ash lime composites
- Falayi, Thabo, Sithole, Thandiwe, Okonta, Felix
- Authors: Falayi, Thabo , Sithole, Thandiwe , Okonta, Felix
- Date: 2019
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/402366 , uj:33669 , Citation: Falayi, T., Sithole, T. & Okonta, F. 2019. Durability of desilicated fly ash lime composites.
- Description: Abstract: Remediation of residual fly ash from coal fired electric power plants is beneficial to the environment. The chemical, physical, geotechnical and radiological properties of desilicated fly ash (DFA) were investigated. The DFA: lime ratio of 70:30 composite was found to have an average UCS of 8.8 MPa showing 19.5% water absorption after a 24 h soak with a corresponding 23.5% reduction in UCS. The composite was found to meet the minimum UCS requirements after 8 wet and dry cycles but with failure at 10 cycles. The composite was found not to be resistant to acid attack at pH 2 and hence could not be used in the vicinity where landfill leachate may come into contact with the composite. The composite had relative stability against acid rain and normal rain. The composite met the minimum requirement of ASTM C34-13, and thus provide an opportunity for high volume utilization of the residual ash for construction of load bearing walls.
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- Authors: Falayi, Thabo , Sithole, Thandiwe , Okonta, Felix
- Date: 2019
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/402366 , uj:33669 , Citation: Falayi, T., Sithole, T. & Okonta, F. 2019. Durability of desilicated fly ash lime composites.
- Description: Abstract: Remediation of residual fly ash from coal fired electric power plants is beneficial to the environment. The chemical, physical, geotechnical and radiological properties of desilicated fly ash (DFA) were investigated. The DFA: lime ratio of 70:30 composite was found to have an average UCS of 8.8 MPa showing 19.5% water absorption after a 24 h soak with a corresponding 23.5% reduction in UCS. The composite was found to meet the minimum UCS requirements after 8 wet and dry cycles but with failure at 10 cycles. The composite was found not to be resistant to acid attack at pH 2 and hence could not be used in the vicinity where landfill leachate may come into contact with the composite. The composite had relative stability against acid rain and normal rain. The composite met the minimum requirement of ASTM C34-13, and thus provide an opportunity for high volume utilization of the residual ash for construction of load bearing walls.
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