The use of carbon nanotubes co-polymerized with calixarenes for the removal of cadmium and organic contaminants from water
- Authors: Makayonke, Nozuko Thelma
- Date: 2012-05-02
- Subjects: Water pollution , Nanotubes , Calixarenes , Organic water pollutants , Cadmium toxicology , Carbon , Nanostructured materials , Water purification , Organic compounds removal , Cadmium removal
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/${Handle} , uj:2231 , http://hdl.handle.net/10210/4671
- Description: M.Sc. , The contamination of water by toxic compounds is one of the most serious environmental problems today. These toxic compounds mostly originate from industrial effluents, agriculture runoff, natural sources (e.g. heavy metals in water from rocks and soil erosion) and human waste. The contamination, which is both “organic” and “inorganic” has an impact on the environment and human health. The demand for water and the pressure to re-use this valuable resource has increased the need for improved techniques and materials to remove pollutants from water. The Nanomaterials Science research group at the University of Johannesburg has focused on developing synthetic polymers that can be employed in water treatment and pollutant monitoring. Recently, cyclodextrins (CD) and carbon nanotubes (CNTs) have been included in polymers for this application. For example, CD-co-hexamethylene-/toluene-diisocyanate polyurethanes and CNT-modified equivalents have been developed and have been successfully applied in removing organic contaminants from water to very low levels.1 Calixarenes are synthetic analogues of cyclodextrins that can be exploited via chemical modification to express a range of properties. In the present study, calixarenes, thiacalixarenes and carbon nanotube-based polymeric materials incorporating these molecules have been synthesised, characterised and tested for removing both organic pollutants (such as p-nitrophenol) and inorganic pollutants (Cd2+, Pb2+) from water. Lead(II) and Cadmium(II) are a threat in South Africa because of their toxicity, and while p-nitrophenol is much less of a problem it represents a useful model organic pollutant. The absorption capacity of the polymers towards heavy metals and organic contaminants was tested by mixing the polymer with synthetic water containing known concentration of the contaminants at about 10 mg/L. Atomic absorption spectrometry (AAS) and ultraviolet-visible spectrometry (UV-vis) were used to determine the levels of heavy metals and organic contaminants, respectively. The target pollutants (Cd2+, 1 see KL Salipira MTech dissertation, University of Johannesburg 2008 Pb2+ and p-nitrophenol) were all successfully removed from water by the various polymers, however the degree of removal and loading capacities of the polymers differed. This information gives some insight into what functional components are needed for making successful adsorbents. It was observed, for example, that ptert- butylcalix[8]arene/hexamethylene diisocyanate (C8A/HMDI) had a higher adsorption capacity towards p-nitrophenol and Pb2+ than towards Cd2+, and also a higher capacity than the corresponding calix[4]arene polymers with smaller calixarene cavities.
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- Authors: Makayonke, Nozuko Thelma
- Date: 2012-05-02
- Subjects: Water pollution , Nanotubes , Calixarenes , Organic water pollutants , Cadmium toxicology , Carbon , Nanostructured materials , Water purification , Organic compounds removal , Cadmium removal
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/${Handle} , uj:2231 , http://hdl.handle.net/10210/4671
- Description: M.Sc. , The contamination of water by toxic compounds is one of the most serious environmental problems today. These toxic compounds mostly originate from industrial effluents, agriculture runoff, natural sources (e.g. heavy metals in water from rocks and soil erosion) and human waste. The contamination, which is both “organic” and “inorganic” has an impact on the environment and human health. The demand for water and the pressure to re-use this valuable resource has increased the need for improved techniques and materials to remove pollutants from water. The Nanomaterials Science research group at the University of Johannesburg has focused on developing synthetic polymers that can be employed in water treatment and pollutant monitoring. Recently, cyclodextrins (CD) and carbon nanotubes (CNTs) have been included in polymers for this application. For example, CD-co-hexamethylene-/toluene-diisocyanate polyurethanes and CNT-modified equivalents have been developed and have been successfully applied in removing organic contaminants from water to very low levels.1 Calixarenes are synthetic analogues of cyclodextrins that can be exploited via chemical modification to express a range of properties. In the present study, calixarenes, thiacalixarenes and carbon nanotube-based polymeric materials incorporating these molecules have been synthesised, characterised and tested for removing both organic pollutants (such as p-nitrophenol) and inorganic pollutants (Cd2+, Pb2+) from water. Lead(II) and Cadmium(II) are a threat in South Africa because of their toxicity, and while p-nitrophenol is much less of a problem it represents a useful model organic pollutant. The absorption capacity of the polymers towards heavy metals and organic contaminants was tested by mixing the polymer with synthetic water containing known concentration of the contaminants at about 10 mg/L. Atomic absorption spectrometry (AAS) and ultraviolet-visible spectrometry (UV-vis) were used to determine the levels of heavy metals and organic contaminants, respectively. The target pollutants (Cd2+, 1 see KL Salipira MTech dissertation, University of Johannesburg 2008 Pb2+ and p-nitrophenol) were all successfully removed from water by the various polymers, however the degree of removal and loading capacities of the polymers differed. This information gives some insight into what functional components are needed for making successful adsorbents. It was observed, for example, that ptert- butylcalix[8]arene/hexamethylene diisocyanate (C8A/HMDI) had a higher adsorption capacity towards p-nitrophenol and Pb2+ than towards Cd2+, and also a higher capacity than the corresponding calix[4]arene polymers with smaller calixarene cavities.
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Application of monometallic and bimetallic dendrimer encapsulated nanoparticles (DENs) and their catalytic evaluation on reduction of 4-nitrophenol
- Authors: Patala, Rapelang
- Date: 2016
- Subjects: Dendrimers , Dendrimers - Synthesis , Catalysis , Inorganic compounds - Analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/226086 , uj:22850
- Description: M.Sc. (Chemistry) , Abstract: The compound 4-nitrophenol found in wastewater streams is mainly the result of industrial and agricultural production. Having adverse health effects associated with it, 4-nitrophenol should be removed from the environment or converted to less hazardous forms as efficiently as possible. Feasible techniques to get rid of this chemical compound are of great research interest. The synthesized nanoparticles encapsulated inside dendrimers (DENs) will be evaluated for catalytic activity against the reaction of 4-nitrophenol reduction. Transition metal nanoparticles find their application in catalysis; this makes them to be of great technological importance. They can be synthesized by evaporation, condensation and chemical or electrochemical reduction of metal salts in the presence of stabilizers. Dendrimers were used as templates for the synthesis of both monometallic and bimetallic nanoparticles which were evaluated as catalysts for the reduction of 4-nitrophenol. We also focused on comprehensive kinetic analysis of 4-nitrophenol reduction using dendrimer encapsulated metal nanoparticles (DENs). The adsorption rates and reaction rates were found and evaluated, and it could be concluded that bimetallic catalysts were more catalytically active than monometallic ones. Different ratios of bimetallic (AuPd) nanoparticles were also supported on different mesoporous metal oxides (MMOs) and their catalytic activity evaluated on reduction of 4-nitrophenol. The results were interpreted in the light of Langmuir Hinshelwood model. The AuPd bimetallic nanoparticles supported on MMOs showed synergistic effect. With the use of power rate law it was shown that 4-nitrophenol reduction follows first order kinetics.
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- Authors: Patala, Rapelang
- Date: 2016
- Subjects: Dendrimers , Dendrimers - Synthesis , Catalysis , Inorganic compounds - Analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/226086 , uj:22850
- Description: M.Sc. (Chemistry) , Abstract: The compound 4-nitrophenol found in wastewater streams is mainly the result of industrial and agricultural production. Having adverse health effects associated with it, 4-nitrophenol should be removed from the environment or converted to less hazardous forms as efficiently as possible. Feasible techniques to get rid of this chemical compound are of great research interest. The synthesized nanoparticles encapsulated inside dendrimers (DENs) will be evaluated for catalytic activity against the reaction of 4-nitrophenol reduction. Transition metal nanoparticles find their application in catalysis; this makes them to be of great technological importance. They can be synthesized by evaporation, condensation and chemical or electrochemical reduction of metal salts in the presence of stabilizers. Dendrimers were used as templates for the synthesis of both monometallic and bimetallic nanoparticles which were evaluated as catalysts for the reduction of 4-nitrophenol. We also focused on comprehensive kinetic analysis of 4-nitrophenol reduction using dendrimer encapsulated metal nanoparticles (DENs). The adsorption rates and reaction rates were found and evaluated, and it could be concluded that bimetallic catalysts were more catalytically active than monometallic ones. Different ratios of bimetallic (AuPd) nanoparticles were also supported on different mesoporous metal oxides (MMOs) and their catalytic activity evaluated on reduction of 4-nitrophenol. The results were interpreted in the light of Langmuir Hinshelwood model. The AuPd bimetallic nanoparticles supported on MMOs showed synergistic effect. With the use of power rate law it was shown that 4-nitrophenol reduction follows first order kinetics.
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Carbon footprint analysis in the preparation of the platinum nanophase electro catalyst composite electrode
- Mabiza, Junior, Mbohwa, Charles
- Authors: Mabiza, Junior , Mbohwa, Charles
- Date: 2013
- Subjects: Carbon footprint analysis , Platinum group , Nanostructured materials , Life Cycle Inventory Assessment , Electrodes
- Type: Article
- Identifier: uj:6161 , http://hdl.handle.net/10210/13765
- Description: A new approach in the use of PGMs for the highly catalytic activity in the production of hydrogen by water electrolysis, is to reduce PGMs into nanometer size (nanophase), then integrate them into electrodes. Water electrolysis is an environmental friendly process of producing hydrogen. This study was for the cognition of likely impacts to environment with regard to the manufacturing process of the composite electrode. The Life Cycle Inventory Assessment method and the carbon footprint calculation in the preparation of the composite electrode were essentially assisted by the Umberto for carbon footprint software, which helped to build an inventory analysis and provided a useful database of materials with respective carbon footprints. Direct emissions were likely involved when heating, calcinating, drying materials. Palliative recommendations were suggested in accordance with the types of emissions identified.
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- Authors: Mabiza, Junior , Mbohwa, Charles
- Date: 2013
- Subjects: Carbon footprint analysis , Platinum group , Nanostructured materials , Life Cycle Inventory Assessment , Electrodes
- Type: Article
- Identifier: uj:6161 , http://hdl.handle.net/10210/13765
- Description: A new approach in the use of PGMs for the highly catalytic activity in the production of hydrogen by water electrolysis, is to reduce PGMs into nanometer size (nanophase), then integrate them into electrodes. Water electrolysis is an environmental friendly process of producing hydrogen. This study was for the cognition of likely impacts to environment with regard to the manufacturing process of the composite electrode. The Life Cycle Inventory Assessment method and the carbon footprint calculation in the preparation of the composite electrode were essentially assisted by the Umberto for carbon footprint software, which helped to build an inventory analysis and provided a useful database of materials with respective carbon footprints. Direct emissions were likely involved when heating, calcinating, drying materials. Palliative recommendations were suggested in accordance with the types of emissions identified.
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Synthesis of carbon hybrid nanostructures and their applications in the solid phase extraction of mycotoxins and cyanotoxins in different matrices
- Authors: Mashile, Geaneth Pertunia
- Date: 2017
- Subjects: Nanostructured materials , Carbon nanotubes , Mycotoxins - Synthesis , Cyanobacterial toxins
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/236134 , uj:24159
- Description: M.Sc. (Nanoscience) , Abstract: Climate change and other environmental factors play a role in the extensive growth of cyanotoxins and aflatoxins in natural water and agricultural commodities respectively. This poses serious concern due to their effect on food availability and safe drinking water supply more especially in human health. Therefore, the aim of the study was to apply nano-adsorbent (silica@multiwalled carbon nanotubes and activated carbon@iron oxide@manganese oxide) for the extraction and preconcetration of these toxins. The subsequent paragraphs discuss the summary of results obtained when each composite was applied for preconcentration of toxins. A simple, rapid and effective method based on dispersive solid phase microextraction (DSPME) and UV-Vis spectrophotometer was developed for the preconcetration and determination of microcystin-LR (MC-LR) in environmental matrices. An activated carbon@ iron oxide@manganese oxide composite was used as solid phase material. The composite was characterized by scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscope (TEM), X-ray powder diffraction (XRD), nitrogen adsorption and FTIR. The factors affecting the DSPME were optimised using multivariate strategy. Under optimised condition, the LOD, LOQ, repeatability (n=10), reproducibility (n = 5) and preconcentration factor were 0.5 μg L−1, 1.7 μg L−1, 3.1, 4.5% and 50, respectively. The percentage recovery of MC-LR in spiked water samples was found to be 98.5%. The developed method DSPME/UV method was simple, rapid, cost-effective and can be used for the detection of MC-LR in real samples without any expensive or challenging equipment. The reliable, simple, rapid and cost-effective extraction method based on an (Ultrasonic-Assisted dispersive solid phase microextraction) UA-DSPME method using silica@multiwalled carbon nanotubes hybrid nanostructures combined with spectrophotometric detection was applied for the first time for preconcentration and determination of aflatoxin B1 (AFB1) in liquid milk samples. Two level factorial design and central composite design in combination with response surface methodology was used to evaluate the factors affecting extraction and preconcentration procedure. The influence of different variables including mass of adsorbent, extraction time, eluent volume and sample volume was investigated in the optimization study. Under the optimal conditions, a dynamic linear range of 0.3–250 μg L−1 with limits of detection of 0.1 μg L−1 was obtained. The...
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- Authors: Mashile, Geaneth Pertunia
- Date: 2017
- Subjects: Nanostructured materials , Carbon nanotubes , Mycotoxins - Synthesis , Cyanobacterial toxins
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/236134 , uj:24159
- Description: M.Sc. (Nanoscience) , Abstract: Climate change and other environmental factors play a role in the extensive growth of cyanotoxins and aflatoxins in natural water and agricultural commodities respectively. This poses serious concern due to their effect on food availability and safe drinking water supply more especially in human health. Therefore, the aim of the study was to apply nano-adsorbent (silica@multiwalled carbon nanotubes and activated carbon@iron oxide@manganese oxide) for the extraction and preconcetration of these toxins. The subsequent paragraphs discuss the summary of results obtained when each composite was applied for preconcentration of toxins. A simple, rapid and effective method based on dispersive solid phase microextraction (DSPME) and UV-Vis spectrophotometer was developed for the preconcetration and determination of microcystin-LR (MC-LR) in environmental matrices. An activated carbon@ iron oxide@manganese oxide composite was used as solid phase material. The composite was characterized by scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscope (TEM), X-ray powder diffraction (XRD), nitrogen adsorption and FTIR. The factors affecting the DSPME were optimised using multivariate strategy. Under optimised condition, the LOD, LOQ, repeatability (n=10), reproducibility (n = 5) and preconcentration factor were 0.5 μg L−1, 1.7 μg L−1, 3.1, 4.5% and 50, respectively. The percentage recovery of MC-LR in spiked water samples was found to be 98.5%. The developed method DSPME/UV method was simple, rapid, cost-effective and can be used for the detection of MC-LR in real samples without any expensive or challenging equipment. The reliable, simple, rapid and cost-effective extraction method based on an (Ultrasonic-Assisted dispersive solid phase microextraction) UA-DSPME method using silica@multiwalled carbon nanotubes hybrid nanostructures combined with spectrophotometric detection was applied for the first time for preconcentration and determination of aflatoxin B1 (AFB1) in liquid milk samples. Two level factorial design and central composite design in combination with response surface methodology was used to evaluate the factors affecting extraction and preconcentration procedure. The influence of different variables including mass of adsorbent, extraction time, eluent volume and sample volume was investigated in the optimization study. Under the optimal conditions, a dynamic linear range of 0.3–250 μg L−1 with limits of detection of 0.1 μg L−1 was obtained. The...
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β-cyclodextrin dendritic-polymers and nanostructured materials for water treatment
- Authors: Malinga, Soraya Phumzile
- Date: 2013-07-24
- Subjects: Nanostructured materials , Cyclodextrins , Water purification - Membrane filtration , Dendrimers
- Type: Thesis
- Identifier: uj:7670 , http://hdl.handle.net/10210/8538
- Description: D.Phil. (Chemistry) , The application of dendritic-based materials has attracted great interest. For the first time this research has investigated the feasibility of poly (propyleneimine) (PPI) dendrimers and hyperbranched polyethyleneimine (HPEI) in combination with beta-cyclodextrin (β-CD) embedded in polysulfone (PSf) membrane for water treatment. The advantage of embedding these conjugates (β-CD-PPI and β-CD-HPEI) in PSf membranes is the presence of numerous nanocavities which can act as water channels allowing easy water passage through the membrane improving water permeability. Secondly, the presence of functional groups such as –OH and –NH greatly improves hydrophilicity of membranes. Commercial polysulfone (PSf) ultrafiltration membranes were crosslinked with β-cyclodextrin-poly (propyleneimine) (β-CD-PPI) and β-cyclodextrin-hyperbranched polyethyleneimine (β-CD-HPEI) using trimesoyl chloride (TMC) by interfacial polymerisation. These membranes were used in the rejection of Aldrich humic acid (molecular weight: 4.1 kDa) from synthetic water samples prepared in the laboratory. Moreover, β-cyclodextrin-poly (propyleneimine) (β-CD-PPI) was used as a host for the preparation of Fe/Ni nanoparticles. The new membranes were synthesised by crosslinking β-CD-PPI with trimesoyl chloride and subsequently loading Fe/Ni nanoparticles and this was supported on a commercial polysulphone (PSf) layer for the degradation of 2,4,6-trichlorophenol (2,4,6-TCP). The membrane surfaces were characterised using Fourier transform infrared/attenuated total reflectance (FT-IR/ATR) spectroscopy , scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution transmission electron microscopy (HR-TEM), water-contact angle, and water-intake capacity...
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- Authors: Malinga, Soraya Phumzile
- Date: 2013-07-24
- Subjects: Nanostructured materials , Cyclodextrins , Water purification - Membrane filtration , Dendrimers
- Type: Thesis
- Identifier: uj:7670 , http://hdl.handle.net/10210/8538
- Description: D.Phil. (Chemistry) , The application of dendritic-based materials has attracted great interest. For the first time this research has investigated the feasibility of poly (propyleneimine) (PPI) dendrimers and hyperbranched polyethyleneimine (HPEI) in combination with beta-cyclodextrin (β-CD) embedded in polysulfone (PSf) membrane for water treatment. The advantage of embedding these conjugates (β-CD-PPI and β-CD-HPEI) in PSf membranes is the presence of numerous nanocavities which can act as water channels allowing easy water passage through the membrane improving water permeability. Secondly, the presence of functional groups such as –OH and –NH greatly improves hydrophilicity of membranes. Commercial polysulfone (PSf) ultrafiltration membranes were crosslinked with β-cyclodextrin-poly (propyleneimine) (β-CD-PPI) and β-cyclodextrin-hyperbranched polyethyleneimine (β-CD-HPEI) using trimesoyl chloride (TMC) by interfacial polymerisation. These membranes were used in the rejection of Aldrich humic acid (molecular weight: 4.1 kDa) from synthetic water samples prepared in the laboratory. Moreover, β-cyclodextrin-poly (propyleneimine) (β-CD-PPI) was used as a host for the preparation of Fe/Ni nanoparticles. The new membranes were synthesised by crosslinking β-CD-PPI with trimesoyl chloride and subsequently loading Fe/Ni nanoparticles and this was supported on a commercial polysulphone (PSf) layer for the degradation of 2,4,6-trichlorophenol (2,4,6-TCP). The membrane surfaces were characterised using Fourier transform infrared/attenuated total reflectance (FT-IR/ATR) spectroscopy , scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution transmission electron microscopy (HR-TEM), water-contact angle, and water-intake capacity...
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Development of an electrochemical cholesterol biosensor based on poly (propylene imine) dendrimer- quantum dots nanocomposite
- Authors: Mokwebo, Kefilwe Vanessa
- Date: 2018
- Subjects: Electrochemical sensors , Biosensors , Quantum dots , Nanostructured materials , Dendrimers in medicine , Cholesterol - Physiological effect
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279597 , uj:30029
- Description: M.Sc. (Nanoscience) , Abstract: One of the parameters that cause cardiovascular diseases (CVDs) is high level of cholesterol in the blood. Therefore, monitoring of cholesterol level is of great importance, especially to elderly people and people with high risk of such diseases. This work explores the applicability of poly (propylene imine) dendrimer (PPI) and CdTe/CdSe/ZnSe quantum dots (QDs) in developing a suitable platform for the development of an enzyme-based electrochemical cholesterol biosensor with enhanced analytical performance. The as-synthesized mercaptopropionic acid (MPA) capped CdTe/CdSe/ZnSe QDs was synthesized in an aqueous phase and characterized using photoluminescence (PL) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), powdered X-ray diffraction (XRD), fourier transform infrared (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The absorption and emission maxima red-shifted as the reaction time and shell growth increased. The increase in PL intensities shows proper passivation of the QDs surface with PL quantum yield (PLQY) of 33.8 %, 69.2 % and 57 %, for CdTe, CdTe/CdSe and CdTe/CdSe/ZnSe QDs respectively. The XRD patterns of all the as-synthesized QDs consist of three diffraction peaks corresponding to (111), (220) and (311) cubic zinc blended structures. The estimated particle size of CdTe/CdSe/ZnSe QDs from XRD and TEM are 4.32 and 4.08 nm, respectively while the EDX confirmed the presence of corresponding elements. For biosensor design, PPI dendrimer was electrochemically deposited on glassy carbon electrode (GCE) and characterized using cyclic voltammetry (CV) and impedance spectroscopy (EIS) in both phosphate buffer solution (PBS) and ferricyanide solution ([Fe(CN)6]-3/-4) This was followed by drop-drying the QDs on the electrode to form GCE/PPI/QDs. Finally, cholesterol oxidase (ChOx) was drop-dried on the GCE/PPI/QDs electrode to produce GCE/PPI/QDs/ChOx-based electrochemical cholesterol biosensor. Scanning electron microscopy (SEM) was used to characterize screen printed carbon electrode (SPCE) as it was modified with different materials and was able to capture the nano-globular morphology of PPI dendrimer. The GCE/PPI/QDs/ChOx based cholesterol biosensor was able to detect cholesterol in the range 0.1-10 mM with a...
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- Authors: Mokwebo, Kefilwe Vanessa
- Date: 2018
- Subjects: Electrochemical sensors , Biosensors , Quantum dots , Nanostructured materials , Dendrimers in medicine , Cholesterol - Physiological effect
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279597 , uj:30029
- Description: M.Sc. (Nanoscience) , Abstract: One of the parameters that cause cardiovascular diseases (CVDs) is high level of cholesterol in the blood. Therefore, monitoring of cholesterol level is of great importance, especially to elderly people and people with high risk of such diseases. This work explores the applicability of poly (propylene imine) dendrimer (PPI) and CdTe/CdSe/ZnSe quantum dots (QDs) in developing a suitable platform for the development of an enzyme-based electrochemical cholesterol biosensor with enhanced analytical performance. The as-synthesized mercaptopropionic acid (MPA) capped CdTe/CdSe/ZnSe QDs was synthesized in an aqueous phase and characterized using photoluminescence (PL) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), powdered X-ray diffraction (XRD), fourier transform infrared (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The absorption and emission maxima red-shifted as the reaction time and shell growth increased. The increase in PL intensities shows proper passivation of the QDs surface with PL quantum yield (PLQY) of 33.8 %, 69.2 % and 57 %, for CdTe, CdTe/CdSe and CdTe/CdSe/ZnSe QDs respectively. The XRD patterns of all the as-synthesized QDs consist of three diffraction peaks corresponding to (111), (220) and (311) cubic zinc blended structures. The estimated particle size of CdTe/CdSe/ZnSe QDs from XRD and TEM are 4.32 and 4.08 nm, respectively while the EDX confirmed the presence of corresponding elements. For biosensor design, PPI dendrimer was electrochemically deposited on glassy carbon electrode (GCE) and characterized using cyclic voltammetry (CV) and impedance spectroscopy (EIS) in both phosphate buffer solution (PBS) and ferricyanide solution ([Fe(CN)6]-3/-4) This was followed by drop-drying the QDs on the electrode to form GCE/PPI/QDs. Finally, cholesterol oxidase (ChOx) was drop-dried on the GCE/PPI/QDs electrode to produce GCE/PPI/QDs/ChOx-based electrochemical cholesterol biosensor. Scanning electron microscopy (SEM) was used to characterize screen printed carbon electrode (SPCE) as it was modified with different materials and was able to capture the nano-globular morphology of PPI dendrimer. The GCE/PPI/QDs/ChOx based cholesterol biosensor was able to detect cholesterol in the range 0.1-10 mM with a...
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Mechanical and tribological properties of nanoceramics dispersion strengthened 2205 duplex stainless steel
- Mphahlele, Mahlatse Ramaesele
- Authors: Mphahlele, Mahlatse Ramaesele
- Date: 2018
- Subjects: Ceramic materials - Mechanical properties , Ceramic materials - Fatigue , Nanostructured materials , Tribology , Mechanical wear
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269167 , uj:28590
- Description: M.Tech. (Chemical Engineering) , Abstract: Conventional Duplex Stainless Steel used in industrial applications suffers degradation in wear and mechanical properties. A good approach to solve these problems is the dispersion of second phase nanoparticles into duplex stainless steel matrix to improve its strength and properties. Taking the advantage of the high hardness and high chemical stability of titanium nitride (TiN), efforts were made to disperse varying amounts of TiN nanoparticles into the matrices of SAF 2205 to enhance its properties. Hence the mechanical properties and tribological behaviour of the duplex stainless steel (SAF 2205 DSS) strengthened with varied amounts of titanium-based ceramics using nanoindentation system and tribometers were studied. The elastic and plastic deformation properties of the DSS composite materials were determined with a nanoindenter together with the wear behavior of the DSS samples using the strain-to-break (H/Er) and the plastic deformation (H3/Er2) parameters. Also the wear characteristics were estimated with a Tribometer, and Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) was employed to evaluate the morphology and chemistry of the wear scar of the DSS composite. The TiN nanoceramics reinforced SAF 2205 composites were fabricated using spark plasma sintering using optimized process parameters: sintering pressure (50MPa), sintering temperature (1150 oC), heating rate (100 oC/min) and sintering holding time (15 minutes). The TiN dispersions into the SAF were varied between 0 - 8 wt% at an interval of 2 wt%. Nanoindentation technique was used to access the plastic (H) properties, elastic (E) properties, the strain-to-break parameter (H/Er) and the resistance to plastic deformation parameter (H3/Er2) behaviour of the composites under loading and unloading conditions. The wear properties of coefficient of friction, wear loss, wear and specific wear rates under dry sliding conditions and varying loads and worn surface were investigated. The microstructures and worn surfaces of the composites were then evaluated using JEOL Scanning Electron Microscopy (FESEM, JSM-7600F). The results show that the TiN is evenly dispersed in the duplex matrix with a general tendency to locate itself at the grain boundaries. The mechanical properties improved considerably as the TiN content increased, resulting from grain boundary refinements and better dispersion strengthening mechanisms. The grain boundaries have better hardness and reduced young modulus compared to the grains. Furthermore, the ratios H/Er and H3/Er2 increased as the TiN composition increases which demonstrates that the nanocomposites wear resistance is favourable and it was in good correlation with the wear test data. The worn mechanism was a mixed mode of adhesive-abrasive at lower TiN composition but at higher TiN content, the adhesive mechanism prevails. This study established that increasing the addition of nanosized titanium nitride confers better microstructural properties, nanoindentation properties and wear behaviour on spark plasma sintered SAF 2205. Nanocomposite with DSS–6 % TiN reinforcement is recommended for industrial applications.
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- Authors: Mphahlele, Mahlatse Ramaesele
- Date: 2018
- Subjects: Ceramic materials - Mechanical properties , Ceramic materials - Fatigue , Nanostructured materials , Tribology , Mechanical wear
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269167 , uj:28590
- Description: M.Tech. (Chemical Engineering) , Abstract: Conventional Duplex Stainless Steel used in industrial applications suffers degradation in wear and mechanical properties. A good approach to solve these problems is the dispersion of second phase nanoparticles into duplex stainless steel matrix to improve its strength and properties. Taking the advantage of the high hardness and high chemical stability of titanium nitride (TiN), efforts were made to disperse varying amounts of TiN nanoparticles into the matrices of SAF 2205 to enhance its properties. Hence the mechanical properties and tribological behaviour of the duplex stainless steel (SAF 2205 DSS) strengthened with varied amounts of titanium-based ceramics using nanoindentation system and tribometers were studied. The elastic and plastic deformation properties of the DSS composite materials were determined with a nanoindenter together with the wear behavior of the DSS samples using the strain-to-break (H/Er) and the plastic deformation (H3/Er2) parameters. Also the wear characteristics were estimated with a Tribometer, and Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) was employed to evaluate the morphology and chemistry of the wear scar of the DSS composite. The TiN nanoceramics reinforced SAF 2205 composites were fabricated using spark plasma sintering using optimized process parameters: sintering pressure (50MPa), sintering temperature (1150 oC), heating rate (100 oC/min) and sintering holding time (15 minutes). The TiN dispersions into the SAF were varied between 0 - 8 wt% at an interval of 2 wt%. Nanoindentation technique was used to access the plastic (H) properties, elastic (E) properties, the strain-to-break parameter (H/Er) and the resistance to plastic deformation parameter (H3/Er2) behaviour of the composites under loading and unloading conditions. The wear properties of coefficient of friction, wear loss, wear and specific wear rates under dry sliding conditions and varying loads and worn surface were investigated. The microstructures and worn surfaces of the composites were then evaluated using JEOL Scanning Electron Microscopy (FESEM, JSM-7600F). The results show that the TiN is evenly dispersed in the duplex matrix with a general tendency to locate itself at the grain boundaries. The mechanical properties improved considerably as the TiN content increased, resulting from grain boundary refinements and better dispersion strengthening mechanisms. The grain boundaries have better hardness and reduced young modulus compared to the grains. Furthermore, the ratios H/Er and H3/Er2 increased as the TiN composition increases which demonstrates that the nanocomposites wear resistance is favourable and it was in good correlation with the wear test data. The worn mechanism was a mixed mode of adhesive-abrasive at lower TiN composition but at higher TiN content, the adhesive mechanism prevails. This study established that increasing the addition of nanosized titanium nitride confers better microstructural properties, nanoindentation properties and wear behaviour on spark plasma sintered SAF 2205. Nanocomposite with DSS–6 % TiN reinforcement is recommended for industrial applications.
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Toxicity assessment of multiwalled carbon nanotubes and fullerenes to Pseudokirchneriella subcapitata, Daphnia magna and Poecilia reticulata in simulated fresh water systems
- Authors: Nyembe, Dumsile W.
- Date: 2016
- Subjects: Nanotechnology - Toxicity testing , Nanostructured materials , Nanotubes
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/124853 , uj:20966
- Description: Abstract: A huge variety of benefits are expected from the application of carbon based nanomaterials. Currently, the nanoproducts that can be found on the market can be classified as consumer products whereas future applications are presumed to encompass areas such as medicine, water purification and industrial applications. Nanomaterials are used mainly for their unique physicochemical properties which are known to improve products’ characteristics. Contrary to the physicochemical goodness, it is these very unique properties that have since raised health and the environmental concerns for. For the sustainability of this innovation and protection of the environment as well as human health, pro-active effort to understand and alleviate potential risks is vital. Current knowledge on nanoecotoxicology is clouded by uncertainties pertaining their fate and behaviour in the environment. With the increase in nanotechnology, carbon-based nanomaterials’ (CBN) have been earmarked for water purification. Their (CBN) behaviour in the aquatic environment, their biovailability in aquatic systems, interaction with and internalization by living organisms and their sub-lethal effects to aquatic organisms are key-determinates to their toxicity, yet they have only just began to emerge. The overarching aim of this thesis therefore was to address the existing gap in knowledge and further bring understanding of fate and behaviour of multi-walled carbon nanotubes (MWCNT) and fullerenes (C60) and their acute and sub-lethal toxicity to algae (Pseudokirchneriella subcapitata), daphnia (Daphnia magna) and fish (Poecilia reticulata) in simulated fresh water systems of varied salinity. The MWCNT and C60 were successfully synthesized using nebulized spray pyrolysis and chemical vapour deposition, respectively, as evidenced by characteristic peaks (D and G bands) identified using Raman spectroscopy. Acid oxidation of p-MWCNT and p-C60 yielded o-MWCNT and o-C60 respectively... , Ph.D. (Chemistry)
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- Authors: Nyembe, Dumsile W.
- Date: 2016
- Subjects: Nanotechnology - Toxicity testing , Nanostructured materials , Nanotubes
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/124853 , uj:20966
- Description: Abstract: A huge variety of benefits are expected from the application of carbon based nanomaterials. Currently, the nanoproducts that can be found on the market can be classified as consumer products whereas future applications are presumed to encompass areas such as medicine, water purification and industrial applications. Nanomaterials are used mainly for their unique physicochemical properties which are known to improve products’ characteristics. Contrary to the physicochemical goodness, it is these very unique properties that have since raised health and the environmental concerns for. For the sustainability of this innovation and protection of the environment as well as human health, pro-active effort to understand and alleviate potential risks is vital. Current knowledge on nanoecotoxicology is clouded by uncertainties pertaining their fate and behaviour in the environment. With the increase in nanotechnology, carbon-based nanomaterials’ (CBN) have been earmarked for water purification. Their (CBN) behaviour in the aquatic environment, their biovailability in aquatic systems, interaction with and internalization by living organisms and their sub-lethal effects to aquatic organisms are key-determinates to their toxicity, yet they have only just began to emerge. The overarching aim of this thesis therefore was to address the existing gap in knowledge and further bring understanding of fate and behaviour of multi-walled carbon nanotubes (MWCNT) and fullerenes (C60) and their acute and sub-lethal toxicity to algae (Pseudokirchneriella subcapitata), daphnia (Daphnia magna) and fish (Poecilia reticulata) in simulated fresh water systems of varied salinity. The MWCNT and C60 were successfully synthesized using nebulized spray pyrolysis and chemical vapour deposition, respectively, as evidenced by characteristic peaks (D and G bands) identified using Raman spectroscopy. Acid oxidation of p-MWCNT and p-C60 yielded o-MWCNT and o-C60 respectively... , Ph.D. (Chemistry)
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Towards the synthesis of doped carbon nanotube/polysulfone nanofiltration membranes for the removal of organic pollutants from water
- Authors: Yokwana, Kholiswa
- Date: 2014-06-26
- Subjects: Organic water pollutants , Carbon composites , Nanostructured materials , Nanotubes
- Type: Thesis
- Identifier: uj:11603 , http://hdl.handle.net/10210/11315
- Description: M.Tech. (Chemistry) , Please refer to full text to view abstract
- Full Text:
- Authors: Yokwana, Kholiswa
- Date: 2014-06-26
- Subjects: Organic water pollutants , Carbon composites , Nanostructured materials , Nanotubes
- Type: Thesis
- Identifier: uj:11603 , http://hdl.handle.net/10210/11315
- Description: M.Tech. (Chemistry) , Please refer to full text to view abstract
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Synthesis and characterization of mesoporous silica/titania nanocomposites : potential additives for dye sensitized solar cells (DSSCs)
- Authors: Akawa, Mpingana Ndilimeke
- Date: 2017
- Subjects: Dye-sensitized solar cells , Nanostructured materials , Mesoporous materials , Silica , Titanium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235628 , uj:24100
- Description: M.Sc. (Nanoscience) , Abstract: The photoanode is an important part of the DSSCs as it is the medium for dye adsorption, electron transport and electrolyte diffusion. The composition and morphology of the photoanode therefore directly influences the performance of the cell. Optimising the morphology of the photoanode is therefore one of the key factors in improving the performance of the DSSCs. This work entailed the synthesis of titania supported on silica nanocomposites for use as light scattering materials in the photoanode with the motivation of optimising the morphology of the photoanode and further enhance the energy conversion efficiency of the DSSCs. The silica support materials, specifically mesoporous silica, SBA-15 and non-mesoporous SiO2 were synthesized through the soft-template acid catalyzed sol-gel method and base catalyzed sol-gel method respectively. Two SBA-15 nanomaterials were synthesized by varying the hydrolysis and aging times which resulted in materials of different textural and morphological properties. These silica support materials (SiO2, SBA-15 A1 and SBA-15 A2) were used as support materials for the synthesis of TiO2 supported on silica nanocomposites. Also, TiO2 nanoparticles of size 19.32 ±3.70 nm (n = 193) were synthesized for use as active site of the photoanode. The physical, chemical and optical properties of the nanoparticles and nanocomposites were studied using FTIR, TEM, Nitrogen Sorption, SEM-EDS, XRD, and diffuse reflectance Ultraviolet-Visible (DR-UV-VIS) spectroscopy. The nitrogen desorption results of the 10 wt% TiO2 / SBA-15 nanocomposites just like the parent SBA-15 support, revealed the Type IV isotherms with H1 hysteresis loops which indicated that the support materials did not lose their mesoporosity and uniform pore size arrangement upon incorporation of TiO2 nanocrystals. This finding was supported by the TEM results. The energy band gaps of TiO2 supported on the mesoporous silica (SBA-15) (3.60 eV) were blue shifted relative to the unsupported TiO2 (3.44 eV) and TiO2 supported on the non-mesoporous SiO2 (3.55 eV). These results confirmed the XRD results which indicated smaller TiO2 crystallite sizes for TiO2 crystals supported on the SBA-15 support materials which were 10.60 nm as compared to the unsupported TiO2 and TiO2 supported on the non-mesoporous SiO2 (15.89 nm). The band gap increased as the crystallite sizes decreased...
- Full Text:
- Authors: Akawa, Mpingana Ndilimeke
- Date: 2017
- Subjects: Dye-sensitized solar cells , Nanostructured materials , Mesoporous materials , Silica , Titanium
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235628 , uj:24100
- Description: M.Sc. (Nanoscience) , Abstract: The photoanode is an important part of the DSSCs as it is the medium for dye adsorption, electron transport and electrolyte diffusion. The composition and morphology of the photoanode therefore directly influences the performance of the cell. Optimising the morphology of the photoanode is therefore one of the key factors in improving the performance of the DSSCs. This work entailed the synthesis of titania supported on silica nanocomposites for use as light scattering materials in the photoanode with the motivation of optimising the morphology of the photoanode and further enhance the energy conversion efficiency of the DSSCs. The silica support materials, specifically mesoporous silica, SBA-15 and non-mesoporous SiO2 were synthesized through the soft-template acid catalyzed sol-gel method and base catalyzed sol-gel method respectively. Two SBA-15 nanomaterials were synthesized by varying the hydrolysis and aging times which resulted in materials of different textural and morphological properties. These silica support materials (SiO2, SBA-15 A1 and SBA-15 A2) were used as support materials for the synthesis of TiO2 supported on silica nanocomposites. Also, TiO2 nanoparticles of size 19.32 ±3.70 nm (n = 193) were synthesized for use as active site of the photoanode. The physical, chemical and optical properties of the nanoparticles and nanocomposites were studied using FTIR, TEM, Nitrogen Sorption, SEM-EDS, XRD, and diffuse reflectance Ultraviolet-Visible (DR-UV-VIS) spectroscopy. The nitrogen desorption results of the 10 wt% TiO2 / SBA-15 nanocomposites just like the parent SBA-15 support, revealed the Type IV isotherms with H1 hysteresis loops which indicated that the support materials did not lose their mesoporosity and uniform pore size arrangement upon incorporation of TiO2 nanocrystals. This finding was supported by the TEM results. The energy band gaps of TiO2 supported on the mesoporous silica (SBA-15) (3.60 eV) were blue shifted relative to the unsupported TiO2 (3.44 eV) and TiO2 supported on the non-mesoporous SiO2 (3.55 eV). These results confirmed the XRD results which indicated smaller TiO2 crystallite sizes for TiO2 crystals supported on the SBA-15 support materials which were 10.60 nm as compared to the unsupported TiO2 and TiO2 supported on the non-mesoporous SiO2 (15.89 nm). The band gap increased as the crystallite sizes decreased...
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Synthesis and characterization of nano-engineered chalcogen materials for environmental and biomedical applications
- Authors: Kumar, Neeraj
- Date: 2017
- Subjects: Nanostructured materials , Polymers , Inorganic cyclic compounds , Chalcogens
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/243095 , uj:25092
- Description: Ph.D. (Chemistry) , Abstract: Nano-engineered chalcogen materials have garnered importance among the researchers across all scientific disciplines because of their interesting properties as well the possibility to tailor their electric, optical, thermal and mechanical properties via controlling shape and size. Various chalcogen based nanostructured materials such as Co3O4, MoO3, MoS2, NiS, WS2, WSe2, MoSe2, Bi2Te3, Ag2Te etc have found improved applications in energy conversion and storage devices, electronics, catalysis, sensors, solid lubricants and topological insulators etc. Still, these nanostructured materials have not been much explored for environmental and biomedical aspects although they have immense potential. The expensive and complicated fabrication techniques and perplexity of surface modification are the critical reasons which limit their utility in desired applications. Most of the previously reported synthesis techniques have also no control over issues such as structural composition, variant size and morphologies. However, different shapes and size dependent properties of nano-engineered chalcogen materials are yet to be explored. Thereby, this study addressed the facile strategies to design and develop new materials and structures with controlled morphologies, size, and composition of nano-engineered chalcogen materials via the wet chemical route. The evolved physiochemical properties based on their structural dimensions were also investigated. The effect of various reaction parameters such as the ratio of precursors, precursor concentrations, the role of stabilising/capping agent and new precursors on the composition and morphological evolution of the chalcogen based nanomaterials have been systematically explored. The developed liquid phase synthesis methodologies of nano-engineered chalcogen materials were facile, economical, energy efficient and eco-friendly. The structural, compositional and morphological features of fabricated chalcogen based nanomaterials were studied using various analytical instruments such as SEM/EDX, HRTEM, XRD, TGA, XPS, UV-Vis, FT-IR and Raman. Furthermore, this research also focused on harnessing the full potential of these synthesised nanomaterials in environmental and biomedical applications based on the information of physiochemical properties. Some applications that are covered in the environmental field are adsorption, photocatalysis and nanophosphors, whereas the biomedical field includes mainly cytotoxic behaviour of nanomaterials. The highlights of results obtained from the PhD study are summarised as follows. Part I presents a study of the anions ratio effect of acetate and nitrate ions on the formation of the different morphology of ZnO crystals in presence of NaOH and HMTA. The...
- Full Text:
- Authors: Kumar, Neeraj
- Date: 2017
- Subjects: Nanostructured materials , Polymers , Inorganic cyclic compounds , Chalcogens
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/243095 , uj:25092
- Description: Ph.D. (Chemistry) , Abstract: Nano-engineered chalcogen materials have garnered importance among the researchers across all scientific disciplines because of their interesting properties as well the possibility to tailor their electric, optical, thermal and mechanical properties via controlling shape and size. Various chalcogen based nanostructured materials such as Co3O4, MoO3, MoS2, NiS, WS2, WSe2, MoSe2, Bi2Te3, Ag2Te etc have found improved applications in energy conversion and storage devices, electronics, catalysis, sensors, solid lubricants and topological insulators etc. Still, these nanostructured materials have not been much explored for environmental and biomedical aspects although they have immense potential. The expensive and complicated fabrication techniques and perplexity of surface modification are the critical reasons which limit their utility in desired applications. Most of the previously reported synthesis techniques have also no control over issues such as structural composition, variant size and morphologies. However, different shapes and size dependent properties of nano-engineered chalcogen materials are yet to be explored. Thereby, this study addressed the facile strategies to design and develop new materials and structures with controlled morphologies, size, and composition of nano-engineered chalcogen materials via the wet chemical route. The evolved physiochemical properties based on their structural dimensions were also investigated. The effect of various reaction parameters such as the ratio of precursors, precursor concentrations, the role of stabilising/capping agent and new precursors on the composition and morphological evolution of the chalcogen based nanomaterials have been systematically explored. The developed liquid phase synthesis methodologies of nano-engineered chalcogen materials were facile, economical, energy efficient and eco-friendly. The structural, compositional and morphological features of fabricated chalcogen based nanomaterials were studied using various analytical instruments such as SEM/EDX, HRTEM, XRD, TGA, XPS, UV-Vis, FT-IR and Raman. Furthermore, this research also focused on harnessing the full potential of these synthesised nanomaterials in environmental and biomedical applications based on the information of physiochemical properties. Some applications that are covered in the environmental field are adsorption, photocatalysis and nanophosphors, whereas the biomedical field includes mainly cytotoxic behaviour of nanomaterials. The highlights of results obtained from the PhD study are summarised as follows. Part I presents a study of the anions ratio effect of acetate and nitrate ions on the formation of the different morphology of ZnO crystals in presence of NaOH and HMTA. The...
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Polyethersulfone (PES) membrane embedded with Fe/Ni nanoparticles decorated-carbon nanotubes (CNTs) for degradation of chlorinated organics in water
- Authors: Thatyana, Maxwell
- Date: 2015-06-30
- Subjects: Water - Purification - Chlorination , Water - Purification - Membrane filtration , Polymeric composites , Nanostructured materials , Carbon nanotubes
- Type: Thesis
- Identifier: uj:13655 , http://hdl.handle.net/10210/13839
- Description: MSc. (Applied Chemistry) , Remediation of POPs particularly the chlorinated compounds in water is therefore crucial. This research work describes the modification of polyethersulfone (PES) thin-film membrane composite (TFC) with functionalised carbon nanotubes (f-CNTs) using the phase invasion method. The oxidised CNTs were successfully decorated with Zero-Valent (ZV) Fe/Ni nanoparticles for the adsorption and degradation studies of polychlorinated organic pollutants (in this case the dichlorodiphenyltrichloroethanes (DDTs)). The in situ modification procedure was carried out using different quantities (0.04 wt%, 0.1 wt% and 0.2 wt%) of Fe/Ni-f-CNTs nanohybrids dispersed in a DMAc solution and dipping the polyethersulfone powder into a suspension containing the Fe/Ni-f-CNTs to form a nano-composite membrane. The formed composite membrane characteristics were investigated with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) and X-ray diffraction spectroscopy (XRD). The incorporation of nanohybrid in the PES membrane was found to increase the surface smoothness and the hydrophilicity of the composites. In addition, there was an increase in the adsorption of DDTs with increase in the nano-hybrid loading as indicated by the adsorption studies using the Langmuir isotherm and Freundlich isotherm studies. The data obtained from the batch studies closely fitted with the Langmuir isotherm based on the characteristic parameter RL found to lie within the standard range 0 < RL < 1 .
- Full Text:
- Authors: Thatyana, Maxwell
- Date: 2015-06-30
- Subjects: Water - Purification - Chlorination , Water - Purification - Membrane filtration , Polymeric composites , Nanostructured materials , Carbon nanotubes
- Type: Thesis
- Identifier: uj:13655 , http://hdl.handle.net/10210/13839
- Description: MSc. (Applied Chemistry) , Remediation of POPs particularly the chlorinated compounds in water is therefore crucial. This research work describes the modification of polyethersulfone (PES) thin-film membrane composite (TFC) with functionalised carbon nanotubes (f-CNTs) using the phase invasion method. The oxidised CNTs were successfully decorated with Zero-Valent (ZV) Fe/Ni nanoparticles for the adsorption and degradation studies of polychlorinated organic pollutants (in this case the dichlorodiphenyltrichloroethanes (DDTs)). The in situ modification procedure was carried out using different quantities (0.04 wt%, 0.1 wt% and 0.2 wt%) of Fe/Ni-f-CNTs nanohybrids dispersed in a DMAc solution and dipping the polyethersulfone powder into a suspension containing the Fe/Ni-f-CNTs to form a nano-composite membrane. The formed composite membrane characteristics were investigated with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) and X-ray diffraction spectroscopy (XRD). The incorporation of nanohybrid in the PES membrane was found to increase the surface smoothness and the hydrophilicity of the composites. In addition, there was an increase in the adsorption of DDTs with increase in the nano-hybrid loading as indicated by the adsorption studies using the Langmuir isotherm and Freundlich isotherm studies. The data obtained from the batch studies closely fitted with the Langmuir isotherm based on the characteristic parameter RL found to lie within the standard range 0 < RL < 1 .
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Polyamide thin film composite membranes modified with zinc oxide nanoparticles and acrylic acid for the removal of heavy metals from wastewater
- Authors: Malatjie, Kgolofelo Inna
- Date: 2017
- Subjects: Polyamide membranes , Water - Purification - Membrane filtration , Nanostructured materials , Zinc oxide
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/251107 , uj:26178
- Description: M.Sc. (Nanoscience) , Abstract: This study focused on the synthesis of pH responsive polyamide thin film composite (PA TFC) membranes modified with zinc oxide (ZnO) nanoparticles and polyacrylic acid (AA) for effective removal of Pb(II) heavy metal ions from wastewater. The novelty of the work was based on the combination of both ZnO and AA, through an in-situ interfacial polymerization modification method of m-phenylenediamine (MPDA) and trimesoyl chloride (TMC). The first part of the research work was based on the modification of PA TFC membranes with different concentration of AA (0.00%, 0.25%, 0.50%, 0.75%, 1.00%, and 1.50%). These membranes were characterized with different techniques such as attenuated total reflectance Fourier transform infra-red spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) and thermal gravimetric analysis (TGA). AFM results showed smoother surfaces upon increasing the AA content. Membrane performance of the PA TFC membranes such as permeability, hydrophilicity, swelling, ion exchange and rejection were evaluated with respect to pH. It was observed that low pH conditions favour high permeability whilst high pH conditions favours high rejection. This is due to the AA ionisable –COOH side chains which tend to collapse at lower pH thereby allowing the diffusion of solutes through the membranes and swelling at high pH thereby restricting the passage of solutes through the membranes. In the second part of the work, the PA TFC membranes were modified with both the AA hydrogel and ZnO nanoparticles at different concentrations. The AA concentration used were 1.00% and 1.50% and were constant throughout while the ZnO concentrations were varied (0.50%, 1.00% and 1.50%). The modified membranes were also found to exhibit high pH responsiveness in terms of permeability, hydrophilicity and Pb(II) rejection. Characterisations such as SEM, AFM and TGA were also carried out. AFM showed rougher surfaces upon an increase concentration of ZnO nanoparticles...
- Full Text:
- Authors: Malatjie, Kgolofelo Inna
- Date: 2017
- Subjects: Polyamide membranes , Water - Purification - Membrane filtration , Nanostructured materials , Zinc oxide
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/251107 , uj:26178
- Description: M.Sc. (Nanoscience) , Abstract: This study focused on the synthesis of pH responsive polyamide thin film composite (PA TFC) membranes modified with zinc oxide (ZnO) nanoparticles and polyacrylic acid (AA) for effective removal of Pb(II) heavy metal ions from wastewater. The novelty of the work was based on the combination of both ZnO and AA, through an in-situ interfacial polymerization modification method of m-phenylenediamine (MPDA) and trimesoyl chloride (TMC). The first part of the research work was based on the modification of PA TFC membranes with different concentration of AA (0.00%, 0.25%, 0.50%, 0.75%, 1.00%, and 1.50%). These membranes were characterized with different techniques such as attenuated total reflectance Fourier transform infra-red spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) and thermal gravimetric analysis (TGA). AFM results showed smoother surfaces upon increasing the AA content. Membrane performance of the PA TFC membranes such as permeability, hydrophilicity, swelling, ion exchange and rejection were evaluated with respect to pH. It was observed that low pH conditions favour high permeability whilst high pH conditions favours high rejection. This is due to the AA ionisable –COOH side chains which tend to collapse at lower pH thereby allowing the diffusion of solutes through the membranes and swelling at high pH thereby restricting the passage of solutes through the membranes. In the second part of the work, the PA TFC membranes were modified with both the AA hydrogel and ZnO nanoparticles at different concentrations. The AA concentration used were 1.00% and 1.50% and were constant throughout while the ZnO concentrations were varied (0.50%, 1.00% and 1.50%). The modified membranes were also found to exhibit high pH responsiveness in terms of permeability, hydrophilicity and Pb(II) rejection. Characterisations such as SEM, AFM and TGA were also carried out. AFM showed rougher surfaces upon an increase concentration of ZnO nanoparticles...
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Indium-zinc oxide nanostructure materials based sensors for the detection of volatile organic compounds and carbon monoxide
- Authors: Kortidis, Ioannis
- Date: 2019
- Subjects: Volatile organic compounds , Nanostructured materials , Indium , Zinc oxide , Gas detectors
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/292586 , uj:31798
- Description: Abstract: Detection of poisonous and flammable gases for health and security purpose utilizing semiconductor metal oxides (SMO) based sensors has fascinated ample attention owing to their incomparable advantages, such as a flawless evidence in variation of their sensor resistance when exposed to either reducing or oxidizing gases. Moreover, their rapid response and recovery times as well as their remarkable sensitivity make them appealing. It is well-known that an anticipated gas sensor ought to possess a combination of enhanced sensitivity, excellent selectivity, rapid response-recovery times, long-term stability and low working temperature. These factors are mostly reliant on surface area to volume ratio, higher relative concentration of defects and crystal structure of the SMO sensing layer. Moreover, this work is justified by the demand of gas sensors globally, with the market estimated to reach approximately R38.4-billion by 2020. According to World Health Organization (WHO) and World Bank, about 5.5 million deaths happen annually costing the world economy R70-trillion a year due to air pollution. While in South Africa about 20 000 deaths occur every year, costing the economy nearly R300-million due to air pollution. Recently, WHO has indicated that most of the cities in SA (such as Pretoria, Johannesburg, etc.) exceed the limit of air quality (AQ) with roughly five times the WHO recommendation, while over 90% of the world's population live in areas that exceed WHO limits on air pollution... , Ph.D. (Chemistry)
- Full Text:
- Authors: Kortidis, Ioannis
- Date: 2019
- Subjects: Volatile organic compounds , Nanostructured materials , Indium , Zinc oxide , Gas detectors
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/292586 , uj:31798
- Description: Abstract: Detection of poisonous and flammable gases for health and security purpose utilizing semiconductor metal oxides (SMO) based sensors has fascinated ample attention owing to their incomparable advantages, such as a flawless evidence in variation of their sensor resistance when exposed to either reducing or oxidizing gases. Moreover, their rapid response and recovery times as well as their remarkable sensitivity make them appealing. It is well-known that an anticipated gas sensor ought to possess a combination of enhanced sensitivity, excellent selectivity, rapid response-recovery times, long-term stability and low working temperature. These factors are mostly reliant on surface area to volume ratio, higher relative concentration of defects and crystal structure of the SMO sensing layer. Moreover, this work is justified by the demand of gas sensors globally, with the market estimated to reach approximately R38.4-billion by 2020. According to World Health Organization (WHO) and World Bank, about 5.5 million deaths happen annually costing the world economy R70-trillion a year due to air pollution. While in South Africa about 20 000 deaths occur every year, costing the economy nearly R300-million due to air pollution. Recently, WHO has indicated that most of the cities in SA (such as Pretoria, Johannesburg, etc.) exceed the limit of air quality (AQ) with roughly five times the WHO recommendation, while over 90% of the world's population live in areas that exceed WHO limits on air pollution... , Ph.D. (Chemistry)
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Non-invasive diagnosis of diabete[s] mellitus using a nanostructured gas sensor
- Authors: Saasa, Raseputuka Valentine
- Date: 2016
- Subjects: Diabetes - Diagnosis , Breath tests , Nanostructured materials , Gas detectors , Nanotechnology
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124784 , uj:20959
- Description: Abstract: Breath analysis has attracted lots of interest in clinical and scientific research for its non-invasive diagnosis of various diseases. Over some decades, exhaled breath has become an important diagnostic method which can be used in the evaluation of health conditions. Volatile Organic Compounds (VOCs) such as acetone, toluene, isoprene and others have been regarded as biomarkers for different diseases (Xiao et al. 2014). Acetone which is generated by hepatocytes via decarboxylation of excess acetyl-coenzyme A, is considered a biomarker of type 1 and type 2 diabetes mellitus (Ueta et al. 2009). Furthermore, acetone has been considered as an indicator of poor diabetic control rather than glucose control (Mannolls, 1983). Current monitoring or diagnosis of diabetes mellitus is achieved through the use of glucose finger prick testing of blood several times daily. This is not only painful but can also be unsafe if proper handling is not undertaken and it is also expensive. Many studies have been done on the analysis of breath for detection of acetone using the Gas Chromatography Mass Spectrometry (GC-MS), Selected Ion-Flow Tube-Mass Spectrometry (SIFT-MS), and others. Although these techniques are accurate, sensitive and specific, they are not suitable for a daily diabetic monitoring for their demands in sample preparation, highly sophisticated laboratory equipment and they are expensive. In this study a portable gas sensor (chemio-resistance) device made of Vanadium dioxide (VO2) has been developed and tested for acetone detection in 30 diabetic and 30 non-diabetic patients. The chemio-resistance sensors are very easy to fabricate, has low limit of detection and are easy to use for non-invasive diagnosis of breath. Gas Chromatography-Mass Spectrometry coupled with Solid Phase Microextraction (SPME) offers a reliable determination of acetone concentration in breath as it is sensitive and specific. Thus breath acetone from 30 diabetic and 30 non diabetic were also analysed with the above mentioned instrumentation to verify and calibrate the result observed with the gas sensor device. The traditional method of diagnosing and monitoring diabetes which is currently used in clinics... , M.Sc. (Biochemistry)
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- Authors: Saasa, Raseputuka Valentine
- Date: 2016
- Subjects: Diabetes - Diagnosis , Breath tests , Nanostructured materials , Gas detectors , Nanotechnology
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/124784 , uj:20959
- Description: Abstract: Breath analysis has attracted lots of interest in clinical and scientific research for its non-invasive diagnosis of various diseases. Over some decades, exhaled breath has become an important diagnostic method which can be used in the evaluation of health conditions. Volatile Organic Compounds (VOCs) such as acetone, toluene, isoprene and others have been regarded as biomarkers for different diseases (Xiao et al. 2014). Acetone which is generated by hepatocytes via decarboxylation of excess acetyl-coenzyme A, is considered a biomarker of type 1 and type 2 diabetes mellitus (Ueta et al. 2009). Furthermore, acetone has been considered as an indicator of poor diabetic control rather than glucose control (Mannolls, 1983). Current monitoring or diagnosis of diabetes mellitus is achieved through the use of glucose finger prick testing of blood several times daily. This is not only painful but can also be unsafe if proper handling is not undertaken and it is also expensive. Many studies have been done on the analysis of breath for detection of acetone using the Gas Chromatography Mass Spectrometry (GC-MS), Selected Ion-Flow Tube-Mass Spectrometry (SIFT-MS), and others. Although these techniques are accurate, sensitive and specific, they are not suitable for a daily diabetic monitoring for their demands in sample preparation, highly sophisticated laboratory equipment and they are expensive. In this study a portable gas sensor (chemio-resistance) device made of Vanadium dioxide (VO2) has been developed and tested for acetone detection in 30 diabetic and 30 non-diabetic patients. The chemio-resistance sensors are very easy to fabricate, has low limit of detection and are easy to use for non-invasive diagnosis of breath. Gas Chromatography-Mass Spectrometry coupled with Solid Phase Microextraction (SPME) offers a reliable determination of acetone concentration in breath as it is sensitive and specific. Thus breath acetone from 30 diabetic and 30 non diabetic were also analysed with the above mentioned instrumentation to verify and calibrate the result observed with the gas sensor device. The traditional method of diagnosing and monitoring diabetes which is currently used in clinics... , M.Sc. (Biochemistry)
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Electrochemical co-detection of arsenic, lead and mercury on exfoliated graphite nanocomposite electrodes
- Authors: Mafa, Potlako John
- Date: 2016
- Subjects: Electrochemical analysis , Nanostructured materials , Graphite , Electrodes , Trace elements - Analysis
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84607 , uj:19241
- Description: Abstract: Please refer to full text to view abstract , M.Sc. (Chemistry)
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- Authors: Mafa, Potlako John
- Date: 2016
- Subjects: Electrochemical analysis , Nanostructured materials , Graphite , Electrodes , Trace elements - Analysis
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84607 , uj:19241
- Description: Abstract: Please refer to full text to view abstract , M.Sc. (Chemistry)
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Corrosion inhibition of mild steel in 1 M Hcl using synthesized eco-friendly polymer composites
- Authors: ‘Mofu, Ts’oeunyane George
- Date: 2017
- Subjects: Corrosion resistant materials , Nanostructured materials , Stainless steel - Corrosion , Corrosion and anti-corrosives
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269731 , uj:28658
- Description: M.Tech. (Metallurgy) , Abstract: In this work, two polymer composites namely PBSLP and PBSLH were synthesized and characterized by FTIR, NMR, XRD, SEM, CHNS and TGA. The results revealed that the formed polymer composite were graft polymer composites. The two synthesized polymer composites were investigated as corrosion inhibitors for MS in 1 M HCl. The corrosion inhibition characteristics including, corrosion rate, corrosion inhibition efficiency, and inhibitor adsorption to the metal surface were studied with gravimetric and electrochemical studies. The gravimetric studies revealed that adsorption of the polymer composites to the MS surface were both physisorption and chemisorption although physisorption appeared to be the more dominant process. Moreover, both polymer composites obeyed Langmuir isotherm. Electrochemical studies were also used to characterize that inhibitory mechanism of the said polymer composites. PDP, specifically Tafel plot and VASP with used to determine the corrosion parameters while EIS was employed to determine the charge transfer characteristics during corrosion. The results indicated that PBSLP and PBSLH are both mixed type corrosion inhibitors with cathodic reaction being the most affected reaction. In addition, the charge transfer resistance during corrosion increased with the increase in concentration of inhibitors. SEM was also used to examine the morphology of MS coupons before and after exposure to corrosive, the results revealed that PBSLP and PBSLH reduce corrosion of MS by forming a film on MS surface.
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- Authors: ‘Mofu, Ts’oeunyane George
- Date: 2017
- Subjects: Corrosion resistant materials , Nanostructured materials , Stainless steel - Corrosion , Corrosion and anti-corrosives
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/269731 , uj:28658
- Description: M.Tech. (Metallurgy) , Abstract: In this work, two polymer composites namely PBSLP and PBSLH were synthesized and characterized by FTIR, NMR, XRD, SEM, CHNS and TGA. The results revealed that the formed polymer composite were graft polymer composites. The two synthesized polymer composites were investigated as corrosion inhibitors for MS in 1 M HCl. The corrosion inhibition characteristics including, corrosion rate, corrosion inhibition efficiency, and inhibitor adsorption to the metal surface were studied with gravimetric and electrochemical studies. The gravimetric studies revealed that adsorption of the polymer composites to the MS surface were both physisorption and chemisorption although physisorption appeared to be the more dominant process. Moreover, both polymer composites obeyed Langmuir isotherm. Electrochemical studies were also used to characterize that inhibitory mechanism of the said polymer composites. PDP, specifically Tafel plot and VASP with used to determine the corrosion parameters while EIS was employed to determine the charge transfer characteristics during corrosion. The results indicated that PBSLP and PBSLH are both mixed type corrosion inhibitors with cathodic reaction being the most affected reaction. In addition, the charge transfer resistance during corrosion increased with the increase in concentration of inhibitors. SEM was also used to examine the morphology of MS coupons before and after exposure to corrosive, the results revealed that PBSLP and PBSLH reduce corrosion of MS by forming a film on MS surface.
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Phosphine derivatized multiwalled carbon nanotubes for the removal of nickel and platinum from solutions
- Authors: Muleja, Adolph Anga
- Date: 2012-05-02
- Subjects: Nickel toxicology , Platinum toxicology , Carbon , Nanotubes , Nanostructured materials , Phosphine , Water - Purification - Nickel removal , Water - Purification - Platinum removal
- Type: Thesis
- Identifier: uj:2237 , http://hdl.handle.net/10210/4677
- Description: M.Tech. , Studies on the removal of nickel and platinum are increasing due to the toxicities of these metals. Several methods are currently used to extract these metals however they present limitations. There is hence a need to develop an efficient method for the removal of nickel and platinum from aqueous solution. A study on the use of purified multiwalled carbon nanotubes (purified MWCNTs) and a phosphine derivatized multiwalled carbon nanotubes for the extraction of these metal ions from solution was therefore undertaken. Multiwalled carbon nanotubes (MWCNTs) were produced by nebulised spray pyrolysis, purified by a multi-step technique and functionalized. Phosphine moieties were attached to the bromoarylated- MWCNTs by metallated phosphide route leading to triphenylphoshine linked MWCNTs (Tpp-MWCNTs). As produced, purified and triphenylphosphine linked multiwalled carbon nanotubes were characterized by various techniques, including microscopic and spectroscopic techniques, thermal, elemental and surface analysis. Transmission and scanning electron microscopy used revealed purified MWCNTs had insignificant impurities. X-ray photoelectron spectroscopy (XPS) results showed that triphenylphosphine linked multiwalled carbon nanotubes had 2.6% phosphorus. Zeta potential results demonstrated that purified MWCNTs had positive surface charges at acidic pH. Triphenylphosphine linked multiwalled carbon nanotubes were negatively charged on the surface in acidic media. Batch adsorption experiments were carried out to investigate the removal of nickel and platinum from aqueous solutions. Several parameters which influence the adsorption process were studied, including the effect of pH, the contact time and the effect of initial concentration on adsorption. The adsorption models for the Freundlich and Langmuir isotherms were employed to fit the experimental data. Triphenylphosphine linked MWCNTs removed more nickel (84.68 mg/g) than purified MWCNTs (77.39 mg/g). In contrast, purified MWCNTs removed more platinum (10.5 mg/g) than triphenylphosphine linked MWCNTs (6.01 mg/g). Experimental data for nickel fitted both Freundlich and Langmuir models well whereas only Langmuir model fitted well for platinum. The adsorption of nickel and platinum was indeed found to be pH, time and initial concentration dependent. Metal species (nickel and platinum) in solution had also influenced the uptake of these metals using purified-and Tpp-MWCNTs.
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- Authors: Muleja, Adolph Anga
- Date: 2012-05-02
- Subjects: Nickel toxicology , Platinum toxicology , Carbon , Nanotubes , Nanostructured materials , Phosphine , Water - Purification - Nickel removal , Water - Purification - Platinum removal
- Type: Thesis
- Identifier: uj:2237 , http://hdl.handle.net/10210/4677
- Description: M.Tech. , Studies on the removal of nickel and platinum are increasing due to the toxicities of these metals. Several methods are currently used to extract these metals however they present limitations. There is hence a need to develop an efficient method for the removal of nickel and platinum from aqueous solution. A study on the use of purified multiwalled carbon nanotubes (purified MWCNTs) and a phosphine derivatized multiwalled carbon nanotubes for the extraction of these metal ions from solution was therefore undertaken. Multiwalled carbon nanotubes (MWCNTs) were produced by nebulised spray pyrolysis, purified by a multi-step technique and functionalized. Phosphine moieties were attached to the bromoarylated- MWCNTs by metallated phosphide route leading to triphenylphoshine linked MWCNTs (Tpp-MWCNTs). As produced, purified and triphenylphosphine linked multiwalled carbon nanotubes were characterized by various techniques, including microscopic and spectroscopic techniques, thermal, elemental and surface analysis. Transmission and scanning electron microscopy used revealed purified MWCNTs had insignificant impurities. X-ray photoelectron spectroscopy (XPS) results showed that triphenylphosphine linked multiwalled carbon nanotubes had 2.6% phosphorus. Zeta potential results demonstrated that purified MWCNTs had positive surface charges at acidic pH. Triphenylphosphine linked multiwalled carbon nanotubes were negatively charged on the surface in acidic media. Batch adsorption experiments were carried out to investigate the removal of nickel and platinum from aqueous solutions. Several parameters which influence the adsorption process were studied, including the effect of pH, the contact time and the effect of initial concentration on adsorption. The adsorption models for the Freundlich and Langmuir isotherms were employed to fit the experimental data. Triphenylphosphine linked MWCNTs removed more nickel (84.68 mg/g) than purified MWCNTs (77.39 mg/g). In contrast, purified MWCNTs removed more platinum (10.5 mg/g) than triphenylphosphine linked MWCNTs (6.01 mg/g). Experimental data for nickel fitted both Freundlich and Langmuir models well whereas only Langmuir model fitted well for platinum. The adsorption of nickel and platinum was indeed found to be pH, time and initial concentration dependent. Metal species (nickel and platinum) in solution had also influenced the uptake of these metals using purified-and Tpp-MWCNTs.
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Biosynthesis, characterization and antibacterial activity of silver and gold nanoparticles from the leaf and bark extracts of Zanthoxylum Capense
- Authors: Nephawe, Mbavhalelo Jade
- Date: 2015
- Subjects: Nanotechnology , Nanoparticles , Nanostructured materials , Gold , Silver
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/372050 , http://hdl.handle.net/10210/84769 , uj:19260
- Description: Abstract: The biosynthesis of nanoparticles has many advantages over tedious, expensive and toxic physical and chemical methods of synthesis. Plants are stocked with valuable metabolites that are capable of reducing metal salts to form nanoparticles. In this study, aqueous leaf and bark extracts of Zanthoxylum capense were reacted with AgNO3 and HAuCl4 to determine the plants reducing abilities and hence synthesis of Ag and Au nanoparticles capabilities. The goal was to develop a reliable, eco-friendly and easy process for the synthesis of silver and gold nanoparticles using extracts of medicinal plant Zanthoxylum capense. Characterization of the nanoparticles formed by the aqueous extracts was performed using Ultraviolet visible (UV-vis) spectroscopy, Dynamic light scattering, Fourier transforms infrared spectroscopy (FTIR), Transmission electron microscope (TEM). Nanoparticles were characterised by measuring their relevant physicochemical properties. Among the determined properties are size, shape, zeta potential and surface charge. UV-vis spectrophotometry was used as a confirmatory as well as a characterizing tool. Phytochemical tests revealed that the leaf and bark extracts of the plant contained “alkaloids, sterols, terpenoids, flavonoids, steroids, phlabotannins and reducing sugars” which were linked as potential reducing agents... , M.Sc.
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- Authors: Nephawe, Mbavhalelo Jade
- Date: 2015
- Subjects: Nanotechnology , Nanoparticles , Nanostructured materials , Gold , Silver
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/372050 , http://hdl.handle.net/10210/84769 , uj:19260
- Description: Abstract: The biosynthesis of nanoparticles has many advantages over tedious, expensive and toxic physical and chemical methods of synthesis. Plants are stocked with valuable metabolites that are capable of reducing metal salts to form nanoparticles. In this study, aqueous leaf and bark extracts of Zanthoxylum capense were reacted with AgNO3 and HAuCl4 to determine the plants reducing abilities and hence synthesis of Ag and Au nanoparticles capabilities. The goal was to develop a reliable, eco-friendly and easy process for the synthesis of silver and gold nanoparticles using extracts of medicinal plant Zanthoxylum capense. Characterization of the nanoparticles formed by the aqueous extracts was performed using Ultraviolet visible (UV-vis) spectroscopy, Dynamic light scattering, Fourier transforms infrared spectroscopy (FTIR), Transmission electron microscope (TEM). Nanoparticles were characterised by measuring their relevant physicochemical properties. Among the determined properties are size, shape, zeta potential and surface charge. UV-vis spectrophotometry was used as a confirmatory as well as a characterizing tool. Phytochemical tests revealed that the leaf and bark extracts of the plant contained “alkaloids, sterols, terpenoids, flavonoids, steroids, phlabotannins and reducing sugars” which were linked as potential reducing agents... , M.Sc.
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Extraction and modification of cactus (Opuntia ficus indica) electrospun nanofibers for water purification
- Authors: Onditi, Mariah
- Date: 2017
- Subjects: Water - Purification - Organic compounds removal , Nanostructured materials , Electrospinning , Nanofibers , Opuntia ficus-indica
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/233997 , uj:23903
- Description: Ph.D. (Chemistry) , Abstract: In this thesis, the use of cactus extracts in water purification as the domain of interest, where the scope includes extraction of vital polysaccharides, nanofiber fabrication and application is presented. The cactus pads (Opuntia ficus indica) used in the study were collected from a neighbouring field to the University of Johannesburg, South Africa. Water pollution is increasing and lack of cheap and adaptable point-of-use technologies, have recently exacerbated water shortage problem. Globally, the existing water resources may not sustain the demand for domestic and industrial use, if the available amounts cannot be harvested, treated and recycled properly. Based on this concern, the quest for efficient wastewater treatment technologies, is of a particular interest to reserchers. Critical examination of the isolated polysaccharides revealed that cactus extracts were generally composed of unique lyxose sugars (both in furanose and pyranose forms) along with other hemicellulose sugar residues. Basically, the polysaccharides obtained from cactus were classified as hemicellulose and pectin sugars. Based on these constituents, a hybrid approach was used to study the applicability of cactus extracts in water treatment and filtration. First, direct use of the polysaccharide extracts was assessed. The adsorption of selected metal cations onto the hemicellulose polysaccharide extract was studied as a function of physico-chemical variables including initial metal ion concentration, adsorbent dosage, contact time and pH of the solution. Results obtained in this study, can be divided into four parts /aspects, as highlighted below. Part I-Adsorption Isotherms: the models indicated that the adsorption percentage of Pb2+ and Cd2+ increased with contact time, attaining equilibrium at 150 min for Cd2+ and 120 min for Pb2+. At these optimal times, the adsorption capacity of both ions increased with an increase in...
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- Authors: Onditi, Mariah
- Date: 2017
- Subjects: Water - Purification - Organic compounds removal , Nanostructured materials , Electrospinning , Nanofibers , Opuntia ficus-indica
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/233997 , uj:23903
- Description: Ph.D. (Chemistry) , Abstract: In this thesis, the use of cactus extracts in water purification as the domain of interest, where the scope includes extraction of vital polysaccharides, nanofiber fabrication and application is presented. The cactus pads (Opuntia ficus indica) used in the study were collected from a neighbouring field to the University of Johannesburg, South Africa. Water pollution is increasing and lack of cheap and adaptable point-of-use technologies, have recently exacerbated water shortage problem. Globally, the existing water resources may not sustain the demand for domestic and industrial use, if the available amounts cannot be harvested, treated and recycled properly. Based on this concern, the quest for efficient wastewater treatment technologies, is of a particular interest to reserchers. Critical examination of the isolated polysaccharides revealed that cactus extracts were generally composed of unique lyxose sugars (both in furanose and pyranose forms) along with other hemicellulose sugar residues. Basically, the polysaccharides obtained from cactus were classified as hemicellulose and pectin sugars. Based on these constituents, a hybrid approach was used to study the applicability of cactus extracts in water treatment and filtration. First, direct use of the polysaccharide extracts was assessed. The adsorption of selected metal cations onto the hemicellulose polysaccharide extract was studied as a function of physico-chemical variables including initial metal ion concentration, adsorbent dosage, contact time and pH of the solution. Results obtained in this study, can be divided into four parts /aspects, as highlighted below. Part I-Adsorption Isotherms: the models indicated that the adsorption percentage of Pb2+ and Cd2+ increased with contact time, attaining equilibrium at 150 min for Cd2+ and 120 min for Pb2+. At these optimal times, the adsorption capacity of both ions increased with an increase in...
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