Laccase production by selected bacteria species isolated from some aquatic and terrestrial milieu of the Eastern Cape : applications in wastewater treatment
- Authors: Unuofin, John Onolame
- Date: 2018
- Subjects: Laccase Sewage -- Purification -- Biological treatment Water -- Purification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9626 , vital:34810
- Description: Aromatic pollutants are a diverse group of chemicals which are continuously produced from industrialization, urbanization and sophistication in technological advancement. Pristine water source polluted by these chemicls makes the water unsafe for human consumption, and as well disrupts the trophic structure of the aquatic milieu. Physico-chemical treatment techniques employed so far have been accompanied by major drawbacks which have overriden the relative successes recorded, hence, greener, simpler and more efficient methods of pollutant transformation is imperative. The prospect of enzymatic treatment of pollutants has gradually been receiving growing attention in contemporary times due to the their environmental friendliness and production economic feasiblity. Laccase, a multicopper oxidase has heightened its appeal towards environmental and biotechnological applications due to its broad substrate specificity and its requirement of atmospheric molecular oxygen as a cosubstrate and the discharge of water as the byproduct. Hence, this present study was designed to evaluate the biotechnological potentials of laccases produced by some bacteria species from some aquatic biomes of the Eastern Cape Province, South Africa. The laccase-producing bacteria were isolated from selected environmental samples by selective enrichment using selective aromatic compounds as sole carbon source and subsequently, laccase-screening phenolic substrates. The laccase-producing bacteria were identified by molecular techniques as proteobacteria belonging to the following genera: Achromobacter, Bordetella, Citrobacter, Pseudomonas and Stenotrophomonas. Optimisation of laccase production in a submerged fermentation was by traditional and statistical methods, where four isolates (Hb9c; Achromobacter xylosoxidans HWN16, Hb16c; Bordetella bronchisepta HSO16, Berl11b2; Stenotrophomonas maltophilia BIJ16, Ie1c; Citrobacter freundii LLJ16) were evaluated for the fermentative production of laccase from lignocellulosic agroindustrial residues. Predictions from statistical optimisation showed that weakly acidic conditions (pH 5) and low agitation speed (100 rpm) were required for maximum laccase production from mandarin peelings (0.5 g/200 mL) and NaNO3 (0.25 g/200 mL) in Hb9c, maize stover (0.50 g/200 mL) and NaNO3 (0.050 g/200mL) in Berl11b2 while a lower agitation speed (50 rpm) was required for maximum laccase output from 2.0 g/200 mL maize stover and 0.050 g/200 mL KNO3 in Ie1c. However, 2.50 g/200 mL wheat bran, 0.050 g/200 mL yeast extract and 50 rpm agitiation under acidic conditions (pH3) yielded maximum laccase titres in Hb16c. Further characterisation of Hb9c and Ie1c laccase secretions portrayed their polyextremotolerant capacities. They were active at a broad range of tempertaure (0-90 degreesC); with optima at 70°C (Hb9c) and 60°C (Ie1c), pH (3-11); with optima at pH 6 (Ie1c) and pH 8 (Hb9c), respectively, and were equally thermo- and pH-stable. Their activities were either improved or left unabated by high concentrations of cations, detergents, and chloride. In addition, catalytic activities of Hb9c and Ie1c laccase secretions increased when they were preincubated with 2 – 20 percent of fluoride, a potent inhibitor. Consequently, a molecular perspective depicted the isolates to have multiple homologous laccase encoding genes. The enzymes were successfully immobilised on solid supports comprising gelatin and Na-alginate with a recovery of cca. 85 percent residual activity after 8 cycles of oprertional stability experiments. The immobilised laccases were remarkable in the decolourisation of synthetic dyes, albeit, free forms also elicited satisfactory performances. Ultimately, the application of free laccases in denim bleaching, individually or with a blend of a mediator, ABTS, showed that denim colours could be bleached without the need for chemical bleaching agents. The results obtained suggest the bacteria laccases produced from lignocellulosic wastes may serve as potent degraders of phenolic pollutants in water and, may also contribute to the bioeconomy and promote greener techniques for industrial applications.
- Full Text:
- Date Issued: 2018
- Authors: Unuofin, John Onolame
- Date: 2018
- Subjects: Laccase Sewage -- Purification -- Biological treatment Water -- Purification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9626 , vital:34810
- Description: Aromatic pollutants are a diverse group of chemicals which are continuously produced from industrialization, urbanization and sophistication in technological advancement. Pristine water source polluted by these chemicls makes the water unsafe for human consumption, and as well disrupts the trophic structure of the aquatic milieu. Physico-chemical treatment techniques employed so far have been accompanied by major drawbacks which have overriden the relative successes recorded, hence, greener, simpler and more efficient methods of pollutant transformation is imperative. The prospect of enzymatic treatment of pollutants has gradually been receiving growing attention in contemporary times due to the their environmental friendliness and production economic feasiblity. Laccase, a multicopper oxidase has heightened its appeal towards environmental and biotechnological applications due to its broad substrate specificity and its requirement of atmospheric molecular oxygen as a cosubstrate and the discharge of water as the byproduct. Hence, this present study was designed to evaluate the biotechnological potentials of laccases produced by some bacteria species from some aquatic biomes of the Eastern Cape Province, South Africa. The laccase-producing bacteria were isolated from selected environmental samples by selective enrichment using selective aromatic compounds as sole carbon source and subsequently, laccase-screening phenolic substrates. The laccase-producing bacteria were identified by molecular techniques as proteobacteria belonging to the following genera: Achromobacter, Bordetella, Citrobacter, Pseudomonas and Stenotrophomonas. Optimisation of laccase production in a submerged fermentation was by traditional and statistical methods, where four isolates (Hb9c; Achromobacter xylosoxidans HWN16, Hb16c; Bordetella bronchisepta HSO16, Berl11b2; Stenotrophomonas maltophilia BIJ16, Ie1c; Citrobacter freundii LLJ16) were evaluated for the fermentative production of laccase from lignocellulosic agroindustrial residues. Predictions from statistical optimisation showed that weakly acidic conditions (pH 5) and low agitation speed (100 rpm) were required for maximum laccase production from mandarin peelings (0.5 g/200 mL) and NaNO3 (0.25 g/200 mL) in Hb9c, maize stover (0.50 g/200 mL) and NaNO3 (0.050 g/200mL) in Berl11b2 while a lower agitation speed (50 rpm) was required for maximum laccase output from 2.0 g/200 mL maize stover and 0.050 g/200 mL KNO3 in Ie1c. However, 2.50 g/200 mL wheat bran, 0.050 g/200 mL yeast extract and 50 rpm agitiation under acidic conditions (pH3) yielded maximum laccase titres in Hb16c. Further characterisation of Hb9c and Ie1c laccase secretions portrayed their polyextremotolerant capacities. They were active at a broad range of tempertaure (0-90 degreesC); with optima at 70°C (Hb9c) and 60°C (Ie1c), pH (3-11); with optima at pH 6 (Ie1c) and pH 8 (Hb9c), respectively, and were equally thermo- and pH-stable. Their activities were either improved or left unabated by high concentrations of cations, detergents, and chloride. In addition, catalytic activities of Hb9c and Ie1c laccase secretions increased when they were preincubated with 2 – 20 percent of fluoride, a potent inhibitor. Consequently, a molecular perspective depicted the isolates to have multiple homologous laccase encoding genes. The enzymes were successfully immobilised on solid supports comprising gelatin and Na-alginate with a recovery of cca. 85 percent residual activity after 8 cycles of oprertional stability experiments. The immobilised laccases were remarkable in the decolourisation of synthetic dyes, albeit, free forms also elicited satisfactory performances. Ultimately, the application of free laccases in denim bleaching, individually or with a blend of a mediator, ABTS, showed that denim colours could be bleached without the need for chemical bleaching agents. The results obtained suggest the bacteria laccases produced from lignocellulosic wastes may serve as potent degraders of phenolic pollutants in water and, may also contribute to the bioeconomy and promote greener techniques for industrial applications.
- Full Text:
- Date Issued: 2018
Skilled Migrants and Remittances in a Development Context: A Social Value Analysis of Skills and Home Remittances among Zimbabweans living in East London, South Africa
- Authors: Mafuso, Leo Tsakata
- Date: 2018
- Subjects: Migration Emigrant remittances Migrant labor
- Language: English
- Type: Thesis , Doctoral , PhD(Sociology)
- Identifier: http://hdl.handle.net/10353/8840 , vital:33672
- Description: Against the backdrop of a growing orthodoxy that places the issue of home remittances by a country’s emigrant citizens at the centre of national and international development, this study presents a social value analysis of skills and home remittances in the Zimbabwean context. The study unveils the narratives of skilled Zimbabwean citizens living and working in East London, South Africa, with specific regard to the extent to which the revenues gained by the Zimbabwean economy through home remittances offset the skills lost by the same economy through the emigration of its skilled citizens. A mixed-methods approach was adopted, with data drawn from a survey of 158 skilled Zimbabweans, three key informant interviews (with officers of immigration stakeholder organisations) and one focus group discussion. The study found that an overwhelming majority of survey respondents regularly remitted money home, and believed that such remittances helped them to fulfil filial and other familial obligations, besides being vital to the Zimbabwean economy as a whole. They emphasised, however, that the total value of home remittances, though substantial in monetary terms, was miniscule when compared to the skills the country had lost as a result of migration. Respondents expressed the view that home remittances could not substitute for the skills lost by a country and that the proper utilisation of, and compensation for, their skills at home would develop their country faster. The study thus cuts through the dominant discourse on the developmental significance of home remittances and provides insights into the importance of skilled professionals in the Zimbabwean context, and the developmental consequences of seeing them simply as “remitters” of foreign exchange. By privileging the perspectives of skilled migrants, the study highlights how skilled professionals see themselves and their role within the migration-development debate. This therefore was a study of the migration-remittance-development nexus as though the migrant mattered.
- Full Text:
- Date Issued: 2018
- Authors: Mafuso, Leo Tsakata
- Date: 2018
- Subjects: Migration Emigrant remittances Migrant labor
- Language: English
- Type: Thesis , Doctoral , PhD(Sociology)
- Identifier: http://hdl.handle.net/10353/8840 , vital:33672
- Description: Against the backdrop of a growing orthodoxy that places the issue of home remittances by a country’s emigrant citizens at the centre of national and international development, this study presents a social value analysis of skills and home remittances in the Zimbabwean context. The study unveils the narratives of skilled Zimbabwean citizens living and working in East London, South Africa, with specific regard to the extent to which the revenues gained by the Zimbabwean economy through home remittances offset the skills lost by the same economy through the emigration of its skilled citizens. A mixed-methods approach was adopted, with data drawn from a survey of 158 skilled Zimbabweans, three key informant interviews (with officers of immigration stakeholder organisations) and one focus group discussion. The study found that an overwhelming majority of survey respondents regularly remitted money home, and believed that such remittances helped them to fulfil filial and other familial obligations, besides being vital to the Zimbabwean economy as a whole. They emphasised, however, that the total value of home remittances, though substantial in monetary terms, was miniscule when compared to the skills the country had lost as a result of migration. Respondents expressed the view that home remittances could not substitute for the skills lost by a country and that the proper utilisation of, and compensation for, their skills at home would develop their country faster. The study thus cuts through the dominant discourse on the developmental significance of home remittances and provides insights into the importance of skilled professionals in the Zimbabwean context, and the developmental consequences of seeing them simply as “remitters” of foreign exchange. By privileging the perspectives of skilled migrants, the study highlights how skilled professionals see themselves and their role within the migration-development debate. This therefore was a study of the migration-remittance-development nexus as though the migrant mattered.
- Full Text:
- Date Issued: 2018
Social work management tasks : the experiences of frontline social workers in the nonprofit organisation sector in Port Elizabeth
- Authors: Perumal, Nevashnee
- Date: 2018
- Subjects: Social service Non-governmental organizations -- Eastern Cape -- Social services
- Language: English
- Type: Thesis , Doctoral , Social Work
- Identifier: http://hdl.handle.net/10353/9756 , vital:34912
- Description: In South Africa, social workers learn how to operationalise the management functions of planning, organising, leading and controlling “on the job” by modelling and following existing managers and/or senior social workers. This points to the use of predictive knowledge, where management decisions are made based on patterns from past experiences, educated guesses and observations, which are limited to individual, personal experiences. For the frontline social worker responding to the dynamic demands of developmental social work, with limited work experience and no formal management training and support, there are several consequences for the Nonprofit Organisation sector and the frontline social worker executing these management tasks. Therefore, this study aimed to gain an understanding of the range of management tasks that frontline social workers undertake in the Nonprofit Organisation sector in operationalising the management functions of planning, organising, leading and controlling. This study employed a descriptive case study design, within the qualitative approach, and was exploratory in nature. In-depth individual interviews were conducted with nineteen frontline social workers from three established Nonprofit Organisations in Port Elizabeth. Qualitative thematic analysis was employed as a data analysis strategy. One focus group was conducted with five middle managers from the same three NPOs. Both phases of data collection were guided by interview themes, which were aligned to the objectives of the study. The major findings indicated that management tasks ranged from workload management, relationship management, information management, human resource management to self-management, and that all these tasks led to frontline social workers developing innovative management strategies as a consequence of undertaking management tasks. Predictive knowledge was magnified as a positive tool as compared to prescriptive knowledge. In light of these findings, it is recommended that organisational support and adjustments are made by the boards of management and directors of the relevant Nonprofit Organisations by specifically providing support to frontline social workers so as to enhance their execution of management tasks. Hence, this study proposes a framework with strategies to support frontline social workers as well as practice guidelines for Nonprofit Organisations’ boards of management and frontline social workers in undertaking their daily management tasks.
- Full Text:
- Date Issued: 2018
- Authors: Perumal, Nevashnee
- Date: 2018
- Subjects: Social service Non-governmental organizations -- Eastern Cape -- Social services
- Language: English
- Type: Thesis , Doctoral , Social Work
- Identifier: http://hdl.handle.net/10353/9756 , vital:34912
- Description: In South Africa, social workers learn how to operationalise the management functions of planning, organising, leading and controlling “on the job” by modelling and following existing managers and/or senior social workers. This points to the use of predictive knowledge, where management decisions are made based on patterns from past experiences, educated guesses and observations, which are limited to individual, personal experiences. For the frontline social worker responding to the dynamic demands of developmental social work, with limited work experience and no formal management training and support, there are several consequences for the Nonprofit Organisation sector and the frontline social worker executing these management tasks. Therefore, this study aimed to gain an understanding of the range of management tasks that frontline social workers undertake in the Nonprofit Organisation sector in operationalising the management functions of planning, organising, leading and controlling. This study employed a descriptive case study design, within the qualitative approach, and was exploratory in nature. In-depth individual interviews were conducted with nineteen frontline social workers from three established Nonprofit Organisations in Port Elizabeth. Qualitative thematic analysis was employed as a data analysis strategy. One focus group was conducted with five middle managers from the same three NPOs. Both phases of data collection were guided by interview themes, which were aligned to the objectives of the study. The major findings indicated that management tasks ranged from workload management, relationship management, information management, human resource management to self-management, and that all these tasks led to frontline social workers developing innovative management strategies as a consequence of undertaking management tasks. Predictive knowledge was magnified as a positive tool as compared to prescriptive knowledge. In light of these findings, it is recommended that organisational support and adjustments are made by the boards of management and directors of the relevant Nonprofit Organisations by specifically providing support to frontline social workers so as to enhance their execution of management tasks. Hence, this study proposes a framework with strategies to support frontline social workers as well as practice guidelines for Nonprofit Organisations’ boards of management and frontline social workers in undertaking their daily management tasks.
- Full Text:
- Date Issued: 2018
Barriers to and enablers of climate change adaptation in four South African municipalities, and implications for community based adaptation
- Authors: Spires, Meggan Hazel
- Date: 2015
- Subjects: Climatic changes -- South Africa , Climatic changes -- Risk management -- South Africa , Climatic changes -- Social aspects -- South Africa , Climate change mitigation -- South Africa , Climatic changes -- Government policy -- South Africa , Municipal government -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4787 , http://hdl.handle.net/10962/d1018913
- Description: The focus of this study is on understanding the multiple and interacting factors that hinder or enable municipal planned climate change adaptation, here called barriers and enablers respectively, and their implications for community based adaptation. To do this I developed a conceptual framework of barriers to and enablers of planned climate change adaptation, which informed a systematic literature review of barriers to planned community based adaptation in developing countries. In this framework barriers were grouped into resource, social and physical barriers. I then conducted empirical case study analysis using qualitative research methods in four South African municipalities to understand what barriers and enablers manifested in these contexts. In light of the reflexive nature of my methodology, my framework was adjusted based on my empirical findings, where contextual barriers were found to better represent the empirical results and subsumed physical barriers. I found my framework useful for analysis, but in the empirical cases, barriers and enablers overlaid and interacted so significantly that in reality it was often difficult to separate them. A key finding was that enablers tended to be more about the way things are done, as opposed to direct opposites of barriers. Comparison of barriers and enablers across the case studies revealed a number of key themes. Municipalities struggle to implement climate change adaptation and community based adaptation within contexts of significant social, economic and ecological challenges. These contextual barriers, when combined with certain cognitive barriers, lead to reactive responses. Existing municipal systems and structures make it difficult to enable climate change adaptation, which is inherently cross‐sectoral and messy, and especially community based adaptation that is bottom‐up and participatory. Lack of locally applicable knowledge, funding and human resources were found to be significant resource barriers, and were often underlain by social barriers relating to perceptions, norms, discourses and governance challenges. Enablers of engaged officials, operating within enabling organisational environments and drawing on partnerships and networks, were able to overcome or circumvent these barriers. When these enablers coincided with windows of opportunity that increased the prioritisation of climate change within the municipality, projects with ancillary benefits were often implemented. Analysis of the barriers and enablers identified in the literature and case studies, informed discussion on whether municipalities are able to implement community based adaptation as defined in the literature, as well as the development of recommendations for how municipal planned climate change adaptation and community based adaptation can be further understood and enabled in the future. These recommendations for practice and research include: (a) To acknowledge and understand the conceptual framings of municipal climate change work, as these framings inform the climate change agenda that is pursued, and hence what municipal climate change adaptation work is done and how it was done. (b) The need for further research into the social barriers that influence the vital enablers of engaged officials, enabling organisational environments, and partnerships and networks. (c) To learn from pilot community‐level interventions that have been implemented by municipalities, as well as from other disciplines and municipalities. (d) To develop top‐down/bottom‐up approaches to enable municipal planned climate change adaptation and community based adaptation, that benefits from high level support and guidance, as well as local level flexibility and learning‐by‐doing. (e) To develop viable mechanisms for municipalities to better engage with the communities they serve.
- Full Text:
- Date Issued: 2015
- Authors: Spires, Meggan Hazel
- Date: 2015
- Subjects: Climatic changes -- South Africa , Climatic changes -- Risk management -- South Africa , Climatic changes -- Social aspects -- South Africa , Climate change mitigation -- South Africa , Climatic changes -- Government policy -- South Africa , Municipal government -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4787 , http://hdl.handle.net/10962/d1018913
- Description: The focus of this study is on understanding the multiple and interacting factors that hinder or enable municipal planned climate change adaptation, here called barriers and enablers respectively, and their implications for community based adaptation. To do this I developed a conceptual framework of barriers to and enablers of planned climate change adaptation, which informed a systematic literature review of barriers to planned community based adaptation in developing countries. In this framework barriers were grouped into resource, social and physical barriers. I then conducted empirical case study analysis using qualitative research methods in four South African municipalities to understand what barriers and enablers manifested in these contexts. In light of the reflexive nature of my methodology, my framework was adjusted based on my empirical findings, where contextual barriers were found to better represent the empirical results and subsumed physical barriers. I found my framework useful for analysis, but in the empirical cases, barriers and enablers overlaid and interacted so significantly that in reality it was often difficult to separate them. A key finding was that enablers tended to be more about the way things are done, as opposed to direct opposites of barriers. Comparison of barriers and enablers across the case studies revealed a number of key themes. Municipalities struggle to implement climate change adaptation and community based adaptation within contexts of significant social, economic and ecological challenges. These contextual barriers, when combined with certain cognitive barriers, lead to reactive responses. Existing municipal systems and structures make it difficult to enable climate change adaptation, which is inherently cross‐sectoral and messy, and especially community based adaptation that is bottom‐up and participatory. Lack of locally applicable knowledge, funding and human resources were found to be significant resource barriers, and were often underlain by social barriers relating to perceptions, norms, discourses and governance challenges. Enablers of engaged officials, operating within enabling organisational environments and drawing on partnerships and networks, were able to overcome or circumvent these barriers. When these enablers coincided with windows of opportunity that increased the prioritisation of climate change within the municipality, projects with ancillary benefits were often implemented. Analysis of the barriers and enablers identified in the literature and case studies, informed discussion on whether municipalities are able to implement community based adaptation as defined in the literature, as well as the development of recommendations for how municipal planned climate change adaptation and community based adaptation can be further understood and enabled in the future. These recommendations for practice and research include: (a) To acknowledge and understand the conceptual framings of municipal climate change work, as these framings inform the climate change agenda that is pursued, and hence what municipal climate change adaptation work is done and how it was done. (b) The need for further research into the social barriers that influence the vital enablers of engaged officials, enabling organisational environments, and partnerships and networks. (c) To learn from pilot community‐level interventions that have been implemented by municipalities, as well as from other disciplines and municipalities. (d) To develop top‐down/bottom‐up approaches to enable municipal planned climate change adaptation and community based adaptation, that benefits from high level support and guidance, as well as local level flexibility and learning‐by‐doing. (e) To develop viable mechanisms for municipalities to better engage with the communities they serve.
- Full Text:
- Date Issued: 2015
Oxidative desulfurization of fuel oils-catalytic oxidation and adsorptive removal of organosulfur compounds
- Authors: Ogunlaja, Adeniyi Sunday
- Date: 2014
- Subjects: Organosulfur compounds , Organosulfur compounds -- Oxidation , Organosulfur compounds -- Absorption and adsorption , Petroleum as fuel , Catalysis , Imprinted polymers , Molecular imprinting , Nanofibers , Electrospinning
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4498 , http://hdl.handle.net/10962/d1013152
- Description: The syntheses and evaluation of oxidovanadium(IV) complexes as catalysts for the oxidation of refractory organosulfur compounds in fuels is presented. The sulfones produced from the oxidation reaction were removed from fuel oils by employing molecularly imprinted polymers (MIPs). The oxidovanadium(IV) homogeneous catalyst, [V ͥ ͮ O(sal-HBPD)], as well as its heterogeneous polymer supported derivatives, poly[V ͥ ͮ O(sal-AHBPD)] and poly[V ͥ ͮ O(allylSB-co-EGDMA)], were synthesized and fully characterized by elemental analysis, FTIR, UV-Vis, XPS, AFM, SEM, BET and single crystal XRD for [V ͥ ͮ O(sal-HBPD)]. The MIPs were also characterized by elemental analysis, FTIR, SEM, EDX and BET. The catalyzed oxidation of fuel oil model sulfur compounds, thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), was conducted under batch and continuous flow processes at 40°C by using tert-butylhydroperoxide (t-BuOOH) as oxidant. The continuous flow oxidation process presented the highest overall conversions and very high selectivity for sulfones. Maximum oxidation conversions of 71%, 89%, 99% and 88% was achieved for TH, BT, DBT and 4,6-DMDBT respectively when poly[V ͥ ͮ O(allylSB-co-EGDMA)] was employed at a flow-rate of 1 mL/h with over 90% sulfone selectivity. The process was further applied to the oxidation of hydro-treated diesel containing 385 ± 4.6 ppm of sulfur (mainly dibenzothiophene and dibenzothiophene derivatives), and this resulted to a high sulfur oxidation yield (> 99%), thus producing polar sulfones which are extractible by polar solid phase extractants. Adsorption of the polar sulfone compounds was carried-out by employing MIPs which were fabricated through the formation of recognition sites complementary to oxidized sulfur-containing compounds (sulfones) on electrospun polybenzimidazole (PBI) nanofibers, cross-linked chitosan microspheres and electrospun chitosan nanofibers. Adsorption of benzothiophene sulfone (BTO₂), dibenzothiophene sulfone (DBTO₂) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO₂) on the various molecularly imprinted adsorbents presented a Freundlich (multi-layered) adsorption isotherm which indicated interaction of adsorbed organosulfur compounds. Maximum adsorption observed for BTO₂, DBTO₂ and 4,6-DMDBTO₂ respectively was 8.5 ± 0.6 mg/g, 7.0 ± 0.5 mg/g and 6.6 ± 0.7 mg/g when imprinted chitosan nanofibers were employed, 4.9 ± 0.5 mg/g, 4.2 ± 0.7 mg/g and 3.9 ± 0.6 mg/g on molecularly imprinted chitosan microspheres, and 28.5 ± 0.4 mg/g, 29.8 ± 2.2 mg/g and 20.1 ± 1.4 mg/g on molecularly imprinted PBI nanofibers. Application of electrospun chitosan nanofibers on oxidized hydro-treated diesel presented a sulfur removal capacity of 84%, leaving 62 ± 3.2 ppm S in the fuel, while imprinted PBI electrospun nanofibers displayed excellent sulfur removal, keeping sulfur in the fuel after the oxidation/adsorption below the determined limit of detection (LOD), which is 2.4 ppm S. The high level of sulfur removal displayed by imprinted PBI nanofibers was ascribed to hydrogen bonding effects, and π-π stacking between aromatic sulfone compounds and the benzimidazole ring which were confirmed by chemical modelling with density functional theory (DFT) as well as the imprinting effect. The home-made pressurized hot water extraction (PHWE) system was applied for extraction/desorption of sulfone compounds adsorbed on the PBI nanofibers at a flow rate of 1 mL/min and at 150°C with an applied pressure of 30 bars. Application of molecularly imprinted PBI nanofibers for the desulfurization of oxidized hydro-treated fuel showed potential for use in refining industries to reach ultra-low sulfur fuel level, which falls below the 10 ppm sulfur limit which is mandated by the environmental protection agency (EPA) from 2015.
- Full Text:
- Date Issued: 2014
- Authors: Ogunlaja, Adeniyi Sunday
- Date: 2014
- Subjects: Organosulfur compounds , Organosulfur compounds -- Oxidation , Organosulfur compounds -- Absorption and adsorption , Petroleum as fuel , Catalysis , Imprinted polymers , Molecular imprinting , Nanofibers , Electrospinning
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4498 , http://hdl.handle.net/10962/d1013152
- Description: The syntheses and evaluation of oxidovanadium(IV) complexes as catalysts for the oxidation of refractory organosulfur compounds in fuels is presented. The sulfones produced from the oxidation reaction were removed from fuel oils by employing molecularly imprinted polymers (MIPs). The oxidovanadium(IV) homogeneous catalyst, [V ͥ ͮ O(sal-HBPD)], as well as its heterogeneous polymer supported derivatives, poly[V ͥ ͮ O(sal-AHBPD)] and poly[V ͥ ͮ O(allylSB-co-EGDMA)], were synthesized and fully characterized by elemental analysis, FTIR, UV-Vis, XPS, AFM, SEM, BET and single crystal XRD for [V ͥ ͮ O(sal-HBPD)]. The MIPs were also characterized by elemental analysis, FTIR, SEM, EDX and BET. The catalyzed oxidation of fuel oil model sulfur compounds, thiophene (TH), benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), was conducted under batch and continuous flow processes at 40°C by using tert-butylhydroperoxide (t-BuOOH) as oxidant. The continuous flow oxidation process presented the highest overall conversions and very high selectivity for sulfones. Maximum oxidation conversions of 71%, 89%, 99% and 88% was achieved for TH, BT, DBT and 4,6-DMDBT respectively when poly[V ͥ ͮ O(allylSB-co-EGDMA)] was employed at a flow-rate of 1 mL/h with over 90% sulfone selectivity. The process was further applied to the oxidation of hydro-treated diesel containing 385 ± 4.6 ppm of sulfur (mainly dibenzothiophene and dibenzothiophene derivatives), and this resulted to a high sulfur oxidation yield (> 99%), thus producing polar sulfones which are extractible by polar solid phase extractants. Adsorption of the polar sulfone compounds was carried-out by employing MIPs which were fabricated through the formation of recognition sites complementary to oxidized sulfur-containing compounds (sulfones) on electrospun polybenzimidazole (PBI) nanofibers, cross-linked chitosan microspheres and electrospun chitosan nanofibers. Adsorption of benzothiophene sulfone (BTO₂), dibenzothiophene sulfone (DBTO₂) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO₂) on the various molecularly imprinted adsorbents presented a Freundlich (multi-layered) adsorption isotherm which indicated interaction of adsorbed organosulfur compounds. Maximum adsorption observed for BTO₂, DBTO₂ and 4,6-DMDBTO₂ respectively was 8.5 ± 0.6 mg/g, 7.0 ± 0.5 mg/g and 6.6 ± 0.7 mg/g when imprinted chitosan nanofibers were employed, 4.9 ± 0.5 mg/g, 4.2 ± 0.7 mg/g and 3.9 ± 0.6 mg/g on molecularly imprinted chitosan microspheres, and 28.5 ± 0.4 mg/g, 29.8 ± 2.2 mg/g and 20.1 ± 1.4 mg/g on molecularly imprinted PBI nanofibers. Application of electrospun chitosan nanofibers on oxidized hydro-treated diesel presented a sulfur removal capacity of 84%, leaving 62 ± 3.2 ppm S in the fuel, while imprinted PBI electrospun nanofibers displayed excellent sulfur removal, keeping sulfur in the fuel after the oxidation/adsorption below the determined limit of detection (LOD), which is 2.4 ppm S. The high level of sulfur removal displayed by imprinted PBI nanofibers was ascribed to hydrogen bonding effects, and π-π stacking between aromatic sulfone compounds and the benzimidazole ring which were confirmed by chemical modelling with density functional theory (DFT) as well as the imprinting effect. The home-made pressurized hot water extraction (PHWE) system was applied for extraction/desorption of sulfone compounds adsorbed on the PBI nanofibers at a flow rate of 1 mL/min and at 150°C with an applied pressure of 30 bars. Application of molecularly imprinted PBI nanofibers for the desulfurization of oxidized hydro-treated fuel showed potential for use in refining industries to reach ultra-low sulfur fuel level, which falls below the 10 ppm sulfur limit which is mandated by the environmental protection agency (EPA) from 2015.
- Full Text:
- Date Issued: 2014
The national curriculum statement on writing practice design for grades 11 and 12: implications for academic writing in higher education
- Authors: Townsend, Rodwell
- Date: 2010
- Subjects: Literacy -- Study and teaching (Higher) -- South Africa , Information literacy -- Study and teaching (Higher) -- South Africa , Academic writing -- Study and teaching (Higher) -- South Africa , Curriculum change -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:8368 , http://hdl.handle.net/10948/1125 , Literacy -- Study and teaching (Higher) -- South Africa , Information literacy -- Study and teaching (Higher) -- South Africa , Academic writing -- Study and teaching (Higher) -- South Africa , Curriculum change -- South Africa
- Description: This study examines the role of academic literacies and academic-writing practices at two diverse South African senior secondary schools and the implications that these practices have for academic-literacy teaching in Higher Education (HE). As student academic writing is central to teaching, learning and assessment in HE, learner academic-writing standards at schools will often impact on academic success in HE. This is a concern for HE as research from South African schooling contexts have found that students from secondary schools are seldom equipped to cope with the demands of HE writing practices. In addition, the introduction of a new curriculum (National Curriculum Statement – NCS) based on the principles of the South African constitution and informed by the Bill of Rights, impacted for the first time on senior secondary schools in 2006, when it was implemented in grade 10, and HE received its first cohort of matriculants with an NCS educational background in 2009. Therefore, this study specifically explores teachers' writing practices within an NCS writing-practice design for grades 11 and 12, and assesses its current implications for academic-writing practices in HE. Critical ethnography was selected as the primary methodology as it is concerned with multiple perspectives and explores local-practice contexts. Therefore, it provides a holistic understanding of the complexity of writing practices by examining the participants' writing-practice perceptions, observing their teaching practices and analysing their written responses or feedback to first and final drafts. The data/study sample consisted of three grades 11 and one grade 12 English Home Language and English First Additional Language teachers as well as selected learners from two secondary schools in the Port Elizabeth district. The data was collected by means of classroom observations, teacher interviews and learner samples of academic writing. Although this study focused on the teaching of academic writing by the four teachers, literacy understandings were also explored by describing what literacy practices subjectively meant to the four teachers by determining the meanings they collectively and individually gave to dominant literacy practices in academic writing, especially feedback practices in text production. A detailed examination of the new NCS requirements suggest that it offers an understanding of knowledge as a social construct, advocates a multiple literacies approach to teaching and learning, and allows for a process approach to cognitively-demanding writing which takes cognisance of the rhetorical, social and cultural dimensions of literacy. Collectively, the ASs in LO3 reflect a process approach to writing, from planning, drafting, feedback, revision to presentation of the final text. It also considers the specific rhetorical dimensions of purpose, audience, and context. Therefore, these NCS writing practices should benefit learners advancing to HE. This study argues that if teachers in secondary schools were to adhere more closely to the NCS's LO3 and its ASs implementation guidelines, learners would be better prepared to cope with HE academic-writing requirements. Instead, the study found that the teachers tended to reduce writing practices to the mastery of discrete sets of technical skills with a focus on surface features of language like spelling and grammar. In addition, the study found that when the teachers' perceptions of the NCS and their own classroom-writing practices were explored, they tended to resist a social-practice approach to academic writing, and, as a result, mostly adapted LO3 of the NCS rather than adopting it as intended by the policy-makers. Similar to other South African studies, this study concludes that teachers remain largely rooted in their autonomous teaching practices favouring traditional methods with which they are familiar over curricula policies which could emancipate learners toward levels of achievement which would better prepare them for both HE and the world of work. In other words, teachers in the sample tend to conserve their traditional methodologies which are predominantly informed by deficit views of learners‟ problems, selectively including new policy requirements which create the impression of compliance, rather than fundamentally altering their approaches pedagogically in the classroom and their academic-writing practices in particular.
- Full Text:
- Date Issued: 2010
- Authors: Townsend, Rodwell
- Date: 2010
- Subjects: Literacy -- Study and teaching (Higher) -- South Africa , Information literacy -- Study and teaching (Higher) -- South Africa , Academic writing -- Study and teaching (Higher) -- South Africa , Curriculum change -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:8368 , http://hdl.handle.net/10948/1125 , Literacy -- Study and teaching (Higher) -- South Africa , Information literacy -- Study and teaching (Higher) -- South Africa , Academic writing -- Study and teaching (Higher) -- South Africa , Curriculum change -- South Africa
- Description: This study examines the role of academic literacies and academic-writing practices at two diverse South African senior secondary schools and the implications that these practices have for academic-literacy teaching in Higher Education (HE). As student academic writing is central to teaching, learning and assessment in HE, learner academic-writing standards at schools will often impact on academic success in HE. This is a concern for HE as research from South African schooling contexts have found that students from secondary schools are seldom equipped to cope with the demands of HE writing practices. In addition, the introduction of a new curriculum (National Curriculum Statement – NCS) based on the principles of the South African constitution and informed by the Bill of Rights, impacted for the first time on senior secondary schools in 2006, when it was implemented in grade 10, and HE received its first cohort of matriculants with an NCS educational background in 2009. Therefore, this study specifically explores teachers' writing practices within an NCS writing-practice design for grades 11 and 12, and assesses its current implications for academic-writing practices in HE. Critical ethnography was selected as the primary methodology as it is concerned with multiple perspectives and explores local-practice contexts. Therefore, it provides a holistic understanding of the complexity of writing practices by examining the participants' writing-practice perceptions, observing their teaching practices and analysing their written responses or feedback to first and final drafts. The data/study sample consisted of three grades 11 and one grade 12 English Home Language and English First Additional Language teachers as well as selected learners from two secondary schools in the Port Elizabeth district. The data was collected by means of classroom observations, teacher interviews and learner samples of academic writing. Although this study focused on the teaching of academic writing by the four teachers, literacy understandings were also explored by describing what literacy practices subjectively meant to the four teachers by determining the meanings they collectively and individually gave to dominant literacy practices in academic writing, especially feedback practices in text production. A detailed examination of the new NCS requirements suggest that it offers an understanding of knowledge as a social construct, advocates a multiple literacies approach to teaching and learning, and allows for a process approach to cognitively-demanding writing which takes cognisance of the rhetorical, social and cultural dimensions of literacy. Collectively, the ASs in LO3 reflect a process approach to writing, from planning, drafting, feedback, revision to presentation of the final text. It also considers the specific rhetorical dimensions of purpose, audience, and context. Therefore, these NCS writing practices should benefit learners advancing to HE. This study argues that if teachers in secondary schools were to adhere more closely to the NCS's LO3 and its ASs implementation guidelines, learners would be better prepared to cope with HE academic-writing requirements. Instead, the study found that the teachers tended to reduce writing practices to the mastery of discrete sets of technical skills with a focus on surface features of language like spelling and grammar. In addition, the study found that when the teachers' perceptions of the NCS and their own classroom-writing practices were explored, they tended to resist a social-practice approach to academic writing, and, as a result, mostly adapted LO3 of the NCS rather than adopting it as intended by the policy-makers. Similar to other South African studies, this study concludes that teachers remain largely rooted in their autonomous teaching practices favouring traditional methods with which they are familiar over curricula policies which could emancipate learners toward levels of achievement which would better prepare them for both HE and the world of work. In other words, teachers in the sample tend to conserve their traditional methodologies which are predominantly informed by deficit views of learners‟ problems, selectively including new policy requirements which create the impression of compliance, rather than fundamentally altering their approaches pedagogically in the classroom and their academic-writing practices in particular.
- Full Text:
- Date Issued: 2010
Solid state thermal decomposition of amide complexes of nickel(II) chloride
- Nelwamondo, Aubrey Ndifelani
- Authors: Nelwamondo, Aubrey Ndifelani
- Date: 1997
- Subjects: Decomposition (Chemistry) Materials -- Thermal properties Amides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4345 , http://hdl.handle.net/10962/d1005008
- Description: The thermal decompositions of a series of amide complexes of nickel(II) chloride have been studied. Thermochemical, kinetic, structure and solid-state stability correlations have been investigated. Complexes containing homologous amide ligands (L) of the form NiLCℓ₂, Ni₃L₂Cℓ₆, Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ (where M = Ni(II), Co(II) or Cu(II)) have been prepared. Chemical analysis, spectral and thermogravimetric measurements were used to characterize the complexes and their decomposition stoichiometries. Three sets of reactions were identified as yielding stable products in a single step: (i) NiLCℓ₂ (s) → NiCℓ₂ (s) + L (g) (ii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + 2L (g) (iii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + L (g) Characterization of the processes in the ML₂Cℓ₂ and NiL₂Cℓ₂(2H₂0) complexes was not straightforward. Reaction enthalpies (ΔH) were determined using DSC. The orders of the reaction onset temperatures (Tc), peak temperatures (Tmax) and ΔHL values for the NiCℓ₂ system were: N-methylacetamide < acetamide < N-methylformamide, suggesting the importance of steric hindrance of the methyl-substituent groups in the amide skeleton. In the Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ systems no simple orders could be deduced. The Te and Tmax sequences obtained from analogous metal(II) chloride complexes indicated that the copper(II) complexes were the least stable. The kinetics of the loss of L from NiLCℓ₂ complexes were investigated using isothermal TG, non-isothermal TG and DSC measurements. The contracting geometry models described the course of the decompositions in the most satisfactory manner. Apparent activation energies ( Ea) were estimated from Arrhenius plots of rate coefficients from: (i) an approximate zero-order relationship, (ii) the contracting-area (R2) and contracting-volume (R3) equations, (iii) a new empirical (B2) expression, (iv) the half-life ( 1/t₀.₅) and (v) the characteristic feature of the rate-time curve ( 1/tmax/2 ). The non-dependence of Ea on the rate equation used supports the reliability of the kinetic parameters. Non-isothermal experiments were analyzed by the Coats-Redfern, the modified BorchardtDaniels and the Kissinger methods. Arrhenius parameters were in keeping with results from the isothermal kinetic measurements. The values of Ea obtained for the NiLCℓ₂ system increased with an increase in basicity of the amide ligands. No straightforward correlation was found between Ea and Te, Tmax, ΔHL or spectral properties.
- Full Text:
- Date Issued: 1997
- Authors: Nelwamondo, Aubrey Ndifelani
- Date: 1997
- Subjects: Decomposition (Chemistry) Materials -- Thermal properties Amides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4345 , http://hdl.handle.net/10962/d1005008
- Description: The thermal decompositions of a series of amide complexes of nickel(II) chloride have been studied. Thermochemical, kinetic, structure and solid-state stability correlations have been investigated. Complexes containing homologous amide ligands (L) of the form NiLCℓ₂, Ni₃L₂Cℓ₆, Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ (where M = Ni(II), Co(II) or Cu(II)) have been prepared. Chemical analysis, spectral and thermogravimetric measurements were used to characterize the complexes and their decomposition stoichiometries. Three sets of reactions were identified as yielding stable products in a single step: (i) NiLCℓ₂ (s) → NiCℓ₂ (s) + L (g) (ii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + 2L (g) (iii) Ni₃LCℓ₆ (s) → 3NiCℓ₂ (s) + L (g) Characterization of the processes in the ML₂Cℓ₂ and NiL₂Cℓ₂(2H₂0) complexes was not straightforward. Reaction enthalpies (ΔH) were determined using DSC. The orders of the reaction onset temperatures (Tc), peak temperatures (Tmax) and ΔHL values for the NiCℓ₂ system were: N-methylacetamide < acetamide < N-methylformamide, suggesting the importance of steric hindrance of the methyl-substituent groups in the amide skeleton. In the Ni₃LCℓ₆, NiL₂Cℓ₂(2H₂0) and ML₂Cℓ₂ systems no simple orders could be deduced. The Te and Tmax sequences obtained from analogous metal(II) chloride complexes indicated that the copper(II) complexes were the least stable. The kinetics of the loss of L from NiLCℓ₂ complexes were investigated using isothermal TG, non-isothermal TG and DSC measurements. The contracting geometry models described the course of the decompositions in the most satisfactory manner. Apparent activation energies ( Ea) were estimated from Arrhenius plots of rate coefficients from: (i) an approximate zero-order relationship, (ii) the contracting-area (R2) and contracting-volume (R3) equations, (iii) a new empirical (B2) expression, (iv) the half-life ( 1/t₀.₅) and (v) the characteristic feature of the rate-time curve ( 1/tmax/2 ). The non-dependence of Ea on the rate equation used supports the reliability of the kinetic parameters. Non-isothermal experiments were analyzed by the Coats-Redfern, the modified BorchardtDaniels and the Kissinger methods. Arrhenius parameters were in keeping with results from the isothermal kinetic measurements. The values of Ea obtained for the NiLCℓ₂ system increased with an increase in basicity of the amide ligands. No straightforward correlation was found between Ea and Te, Tmax, ΔHL or spectral properties.
- Full Text:
- Date Issued: 1997
The structure of an irrigation scheme
- Authors: Holbrook, Gregory Martin
- Date: 1993
- Subjects: Tyefu Irrigation Scheme -- South Africa -- Eastern Cape , Agricultural development projects -- South Africa -- Ciskei , Irrigation -- South Africa -- Ciskei , Xhosa (African people) -- Economic conditions , Xhosa (African people) -- Social life and customs
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2101 , http://hdl.handle.net/10962/d1002664 , Tyefu Irrigation Scheme -- South Africa -- Eastern Cape , Agricultural development projects -- South Africa -- Ciskei , Irrigation -- South Africa -- Ciskei , Xhosa (African people) -- Economic conditions , Xhosa (African people) -- Social life and customs
- Description: Faced with problems related to the sustainability and advisability of contemporary irrigation development in Africa, anthropologists have increasingly looked to economic and political explanations for the success or failure of those development schemes. Instead of seeking explanations in these isolated areas, this thesis has argued that irrigation development needs to be understood through relationships within and between politics, economics, social structure and culture. In order to uncover those interactions with regard to the Tyefu Irrigation Scheme in the southern African homeland of Ciskei, reference has been made, firstly, to the mechanisms underlying contemporary state expansion and secondly, to the interaction between external forces, structures and surface forms through time. Anthropological fieldwork techniques have been used to provide detailed descriptions of everyday communications within and between groups associated with the development. Ethnography allows implementation to be conceptualized in terms of the interaction between local level structures and structures associated with the planning and construction of irrigation development itself. When the effect of external forces on the interaction between structures and forms is then taken into account principles emerge that reflect local and historical transformations. These in turn suggest the form of contemporary state expansion in southern Africa, as well as its bearing on daily life on the rural periphery.
- Full Text:
- Date Issued: 1993
- Authors: Holbrook, Gregory Martin
- Date: 1993
- Subjects: Tyefu Irrigation Scheme -- South Africa -- Eastern Cape , Agricultural development projects -- South Africa -- Ciskei , Irrigation -- South Africa -- Ciskei , Xhosa (African people) -- Economic conditions , Xhosa (African people) -- Social life and customs
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2101 , http://hdl.handle.net/10962/d1002664 , Tyefu Irrigation Scheme -- South Africa -- Eastern Cape , Agricultural development projects -- South Africa -- Ciskei , Irrigation -- South Africa -- Ciskei , Xhosa (African people) -- Economic conditions , Xhosa (African people) -- Social life and customs
- Description: Faced with problems related to the sustainability and advisability of contemporary irrigation development in Africa, anthropologists have increasingly looked to economic and political explanations for the success or failure of those development schemes. Instead of seeking explanations in these isolated areas, this thesis has argued that irrigation development needs to be understood through relationships within and between politics, economics, social structure and culture. In order to uncover those interactions with regard to the Tyefu Irrigation Scheme in the southern African homeland of Ciskei, reference has been made, firstly, to the mechanisms underlying contemporary state expansion and secondly, to the interaction between external forces, structures and surface forms through time. Anthropological fieldwork techniques have been used to provide detailed descriptions of everyday communications within and between groups associated with the development. Ethnography allows implementation to be conceptualized in terms of the interaction between local level structures and structures associated with the planning and construction of irrigation development itself. When the effect of external forces on the interaction between structures and forms is then taken into account principles emerge that reflect local and historical transformations. These in turn suggest the form of contemporary state expansion in southern Africa, as well as its bearing on daily life on the rural periphery.
- Full Text:
- Date Issued: 1993
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