Application of semiconductor metal oxide-CNPs- cellulose acetate polymer nanocomposites in solid-state gas sensors for the detection of tuberculosis VOCs biomarkers
- Authors: Malepe, Lesego
- Date: 2020
- Subjects: Biochemical markers , Volatile organic compounds , Gas detectors , Metal oxide semiconductors , Nanocomposites (Materials) , Tuberculosis - Diagnosis
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/458501 , uj:40727
- Description: Abstract: Active pulmonary tuberculosis (TB) is a death leading disease caused by a bacteria by the name of mycobacterium. TB is a life-threatening disease in most developing countries including sub-Saharan Africa countries (Nigeria, Mozambique, Zambia and South Africa). Culture and microscopy methods are still reliable techniques for pulmonary diagnoses even though every year there are millions of deaths from it, hence there is a need for a cheap, portable and more sensitive new diagnostic tool to assist the system. There is a new approach to diagnosing pulmonary TB through the detection of volatile organic compounds TB biomarkers. Based on technology and research development, currently, analytical instruments used for detection of TB biomarkers are Gas Chromatography-Mass Spectroscopy, proton mass transfer reaction- mass spectroscopy and more, unfortunately, they are expensive, require high maintenance, trained personnel, and are not portable. The failures in using analytical instruments for the detection of TB biomarkers allow the introduction in finding a portable, inexpensive and easy operation sensing device which can detect volatile organic compounds (VOCs) biomarkers. From the previous studies, Semiconductor metal oxides (SMOs), carbon materials and polymers received great attention to the gas sensor research field. Nickel oxide nanoparticles (NiO NPs), carbon nanoparticles soot (CNPs), nickel oxidecarbon nanoparticles-cellulose acetate (NiO-CNPs-CA) composite and titanium dioxide-carbon nanoparticles-cellulose acetate (TiO2-CNPs-CA) composite were synthesized and characterized using scanning electron microscopy (SEM), highresolution transmission electron microscopy (HRTEM), powder X-ray diffraction (PXRD), Fourier transform Infrared spectroscopy (FTIR), Raman spectroscopy and N2 adsorption-desorption isotherms. NiO, TiO2, CA, NiO-CA, TiO2-CA, CNPs-CA, NiOCNPs, TiO2-CNPs, NiO-CNPs-CA, TiO2-CNPs-CA room temperature gas sensors were fabricated and tested using octanal, 3-pentanone, mesitylene and 4-methyl-1- hexene known as pulmonary TB biomarkers at 25 Hz frequency and 0.5V as a voltage supplied to a gas sensing electrode. Sensitivity of the gas sensors were done by testing the prepared gas sensors in both impedance and resistance parameters and various sensors were prepared by increasing the mass ratio of SMO within the ternary composite made up of SMO (NiO and TiO2), CNPs and CA sensing materials. TiO2- CNPs-CA composite (sensor A) is the best sensor to the detection of mesitylene for viii both resistance and impedance parameters with the sensitivity of 1.662 and 1.639 Ω ppm-1 respectively and sensor TiO2-CNPs composite sensor showed to have a maximum sensitivity of 1.99 Ω ppm-1 under impedance parameter. , M.Sc. (Nanoscience)
- Full Text:
- Authors: Malepe, Lesego
- Date: 2020
- Subjects: Biochemical markers , Volatile organic compounds , Gas detectors , Metal oxide semiconductors , Nanocomposites (Materials) , Tuberculosis - Diagnosis
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/458501 , uj:40727
- Description: Abstract: Active pulmonary tuberculosis (TB) is a death leading disease caused by a bacteria by the name of mycobacterium. TB is a life-threatening disease in most developing countries including sub-Saharan Africa countries (Nigeria, Mozambique, Zambia and South Africa). Culture and microscopy methods are still reliable techniques for pulmonary diagnoses even though every year there are millions of deaths from it, hence there is a need for a cheap, portable and more sensitive new diagnostic tool to assist the system. There is a new approach to diagnosing pulmonary TB through the detection of volatile organic compounds TB biomarkers. Based on technology and research development, currently, analytical instruments used for detection of TB biomarkers are Gas Chromatography-Mass Spectroscopy, proton mass transfer reaction- mass spectroscopy and more, unfortunately, they are expensive, require high maintenance, trained personnel, and are not portable. The failures in using analytical instruments for the detection of TB biomarkers allow the introduction in finding a portable, inexpensive and easy operation sensing device which can detect volatile organic compounds (VOCs) biomarkers. From the previous studies, Semiconductor metal oxides (SMOs), carbon materials and polymers received great attention to the gas sensor research field. Nickel oxide nanoparticles (NiO NPs), carbon nanoparticles soot (CNPs), nickel oxidecarbon nanoparticles-cellulose acetate (NiO-CNPs-CA) composite and titanium dioxide-carbon nanoparticles-cellulose acetate (TiO2-CNPs-CA) composite were synthesized and characterized using scanning electron microscopy (SEM), highresolution transmission electron microscopy (HRTEM), powder X-ray diffraction (PXRD), Fourier transform Infrared spectroscopy (FTIR), Raman spectroscopy and N2 adsorption-desorption isotherms. NiO, TiO2, CA, NiO-CA, TiO2-CA, CNPs-CA, NiOCNPs, TiO2-CNPs, NiO-CNPs-CA, TiO2-CNPs-CA room temperature gas sensors were fabricated and tested using octanal, 3-pentanone, mesitylene and 4-methyl-1- hexene known as pulmonary TB biomarkers at 25 Hz frequency and 0.5V as a voltage supplied to a gas sensing electrode. Sensitivity of the gas sensors were done by testing the prepared gas sensors in both impedance and resistance parameters and various sensors were prepared by increasing the mass ratio of SMO within the ternary composite made up of SMO (NiO and TiO2), CNPs and CA sensing materials. TiO2- CNPs-CA composite (sensor A) is the best sensor to the detection of mesitylene for viii both resistance and impedance parameters with the sensitivity of 1.662 and 1.639 Ω ppm-1 respectively and sensor TiO2-CNPs composite sensor showed to have a maximum sensitivity of 1.99 Ω ppm-1 under impedance parameter. , M.Sc. (Nanoscience)
- Full Text:
Development of cellulose nanostructure-based biodegradable nanocomposite foams for packaging application
- Authors: Motloung, Mpho Phillip
- Date: 2020
- Subjects: Biopolymers , Nanocomposites (Materials) , Foamed materials , Packaging - Materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/458584 , uj:40738
- Description: Abstract: Design and development of environmentally benign materials have led to development of polymer foams derived from biodegradable polymers. Driven by the environmental concerns regarding polymers in general, lots of attention has been diverted to the utilization of biopolymer foams as a potential replacement for most currently used polymer foams derived from non-biodegradable polymers. In this work, environmentally benign PLA-based blend foams containing cellulose nanostructures were developed through melt-processing and solvent casting processing techniques. Polylactide (PLA)/poly(-caprolactone) (PCL) blend foams containing both unmodified and modified cellulose nanocrystals (CNs), and cellulose nanofibers (CNFs) were prepared through melt-processing using azodicarbonamide as a chemical blowing agent, while PLA/poly[(butylene succinate)-adipate] (PBSA) blend foams containing CNs at different concentrations were also prepared through casting and particulate leaching technique (CPL). The morphologies of the foams were investigated using scanning electron microscopy (SEM). The storage moduli of the foams were determined using dynamic mechanical analyzer (DMA). Further, the thermal stabilities of the foams were examined using a thermogravimetric analyzer (TGA). Both crystalline and chemical structures were determined using small-angle X-ray scattering (SAXS) technique and attenuated Fourier transform infrared spectroscopy (FTIR), respectively... , M.Sc. (Chemistry)
- Full Text:
- Authors: Motloung, Mpho Phillip
- Date: 2020
- Subjects: Biopolymers , Nanocomposites (Materials) , Foamed materials , Packaging - Materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/458584 , uj:40738
- Description: Abstract: Design and development of environmentally benign materials have led to development of polymer foams derived from biodegradable polymers. Driven by the environmental concerns regarding polymers in general, lots of attention has been diverted to the utilization of biopolymer foams as a potential replacement for most currently used polymer foams derived from non-biodegradable polymers. In this work, environmentally benign PLA-based blend foams containing cellulose nanostructures were developed through melt-processing and solvent casting processing techniques. Polylactide (PLA)/poly(-caprolactone) (PCL) blend foams containing both unmodified and modified cellulose nanocrystals (CNs), and cellulose nanofibers (CNFs) were prepared through melt-processing using azodicarbonamide as a chemical blowing agent, while PLA/poly[(butylene succinate)-adipate] (PBSA) blend foams containing CNs at different concentrations were also prepared through casting and particulate leaching technique (CPL). The morphologies of the foams were investigated using scanning electron microscopy (SEM). The storage moduli of the foams were determined using dynamic mechanical analyzer (DMA). Further, the thermal stabilities of the foams were examined using a thermogravimetric analyzer (TGA). Both crystalline and chemical structures were determined using small-angle X-ray scattering (SAXS) technique and attenuated Fourier transform infrared spectroscopy (FTIR), respectively... , M.Sc. (Chemistry)
- Full Text:
Heterojunctions cerium oxide nanocomposites for photocatalytic synthesis of bio-based chemicals
- Authors: Mavuso, Mlungisi Arnold
- Date: 2020
- Subjects: Photocatalysis , Heterojunctions , Nanostructured materials , Nanocomposites (Materials)
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/474108 , uj:42723
- Description: Abstract: In the last decade, selective photocatalytic processes have been developed for fabrication of value-added chemicals with promising activities and selectivities. However, to achieve highly selective photocatalytic oxidation is still presenting a formidable challenge because of the generation of non-selective •OH radicals. Also, photocatalysis could be associated with two major problems including: (i) low photocatalytic efficiency (i.e. activity and selectivity) and (ii) unsatisfactory visible-light responsive photocatalytic materials. To develop highly efficient visible-light photocatalytic materials, several photocatalysts modification strategies such as bandgap modification, selective growth of crystal facets and surface treatment have been explored. To achieve this feat, morphology-controlled CeO2 nanostructures (i.e. CeO2-NPs, CeO2-NRs and CeO2-NCs) and heterostructured CeO2 interfaces (i.e. CeO2- MO, MO = SnO2, ZnO, TiO2, Nb2O5, MoO3, CuO, Co3O4, NiO, MnO2 & Fe2O3) were successfully synthesized by solution processes and characterized by the XRD, BET, UV/Vis, PL, XPS, EPR, SEM and TEM analytical techniques. According to the data, CeO2-NRs photocatalyst gave the best pinene conversion amount of 33.6% and pinene oxide selectivity of 54.3% as the major product after 5 h reaction time. The CeO2-NRs photocatalyst was recycled 5 times without any significant loss of its photocatalytic activity. Furthermore, CeO2-NRs photocatalyst was versatile for the photooxidation of HMF under visible light irradiation to afford DFF selectivity of 40.3% as the major product and oxalic acid formation (23% selectivity) at 70% HMF conversion. The heterostructured CeO2-based interfaces showed an increase in the photocatalytic efficiency when compared to pure CeO2 NPs in the selective oxidation of Pinus wood-derived α-pinene to aroma oxygenated derivatives. Particularly, the Fe2O3-CeO2 and NiO-CeO2 photocatalysts afforded good pinene conversions of 71.3% and 53.1%, respectively. The corresponding pinene oxide selectivities of 57.3% and 58.2% for Fe2O3-CeO2 and NiO-CeO2 photocatalysts were obtained after 5 h reaction. Furthermore, the heterojunction MoO3-CeO2 nanocatalyst offered the best pinene oxide selectivity of 63.8% at 65.8% pinene conversion after 5 h visible light irradiation at 25 °C. Also, H2O2 and reaction temperature had a positive influence on the photoactivity but negatively affected the product selectivity. selectivity. Lastly, the heterojunction MoO3-CeO2 nanocatalyst exhibited potential for application for various types of biomass-derived chemicals, including HMF, furfural, vanillyl alcohol, isoeugenol and glycerol. , Ph.D. (Chemistry)
- Full Text:
- Authors: Mavuso, Mlungisi Arnold
- Date: 2020
- Subjects: Photocatalysis , Heterojunctions , Nanostructured materials , Nanocomposites (Materials)
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/474108 , uj:42723
- Description: Abstract: In the last decade, selective photocatalytic processes have been developed for fabrication of value-added chemicals with promising activities and selectivities. However, to achieve highly selective photocatalytic oxidation is still presenting a formidable challenge because of the generation of non-selective •OH radicals. Also, photocatalysis could be associated with two major problems including: (i) low photocatalytic efficiency (i.e. activity and selectivity) and (ii) unsatisfactory visible-light responsive photocatalytic materials. To develop highly efficient visible-light photocatalytic materials, several photocatalysts modification strategies such as bandgap modification, selective growth of crystal facets and surface treatment have been explored. To achieve this feat, morphology-controlled CeO2 nanostructures (i.e. CeO2-NPs, CeO2-NRs and CeO2-NCs) and heterostructured CeO2 interfaces (i.e. CeO2- MO, MO = SnO2, ZnO, TiO2, Nb2O5, MoO3, CuO, Co3O4, NiO, MnO2 & Fe2O3) were successfully synthesized by solution processes and characterized by the XRD, BET, UV/Vis, PL, XPS, EPR, SEM and TEM analytical techniques. According to the data, CeO2-NRs photocatalyst gave the best pinene conversion amount of 33.6% and pinene oxide selectivity of 54.3% as the major product after 5 h reaction time. The CeO2-NRs photocatalyst was recycled 5 times without any significant loss of its photocatalytic activity. Furthermore, CeO2-NRs photocatalyst was versatile for the photooxidation of HMF under visible light irradiation to afford DFF selectivity of 40.3% as the major product and oxalic acid formation (23% selectivity) at 70% HMF conversion. The heterostructured CeO2-based interfaces showed an increase in the photocatalytic efficiency when compared to pure CeO2 NPs in the selective oxidation of Pinus wood-derived α-pinene to aroma oxygenated derivatives. Particularly, the Fe2O3-CeO2 and NiO-CeO2 photocatalysts afforded good pinene conversions of 71.3% and 53.1%, respectively. The corresponding pinene oxide selectivities of 57.3% and 58.2% for Fe2O3-CeO2 and NiO-CeO2 photocatalysts were obtained after 5 h reaction. Furthermore, the heterojunction MoO3-CeO2 nanocatalyst offered the best pinene oxide selectivity of 63.8% at 65.8% pinene conversion after 5 h visible light irradiation at 25 °C. Also, H2O2 and reaction temperature had a positive influence on the photoactivity but negatively affected the product selectivity. selectivity. Lastly, the heterojunction MoO3-CeO2 nanocatalyst exhibited potential for application for various types of biomass-derived chemicals, including HMF, furfural, vanillyl alcohol, isoeugenol and glycerol. , Ph.D. (Chemistry)
- Full Text:
Carbonaceous nanomaterials and their conducting polymerbased nanocomposites for the removal of heavy metals from water and the use of metal-loaded adsorbents for gas sensing applications
- Authors: Skosana, Lindiwe
- Date: 2019
- Subjects: Extraction (Chemistry) , Adsorption , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/418824 , uj:35525
- Description: Abstract: The presence of Co2+ and Ni2+ in water is a major concern owing to their non-biodegradable, carcinogenic and mutagenic nature. In recent years, diverse techniques have been applied in their removal from water and upon careful evaluation of some of these techniques, adsorption seemed to be a desirable technique of choice owing to its favourable characteristics as well as its benefits in Co2+ and Ni2+ removal. By virtue of the efficacy of adsorption being governed by an adsorbent, Hollow Carbon Nano Spheres (HCNS) have emerged as attractive adsorbents of choice due to their favourable characteristics in comparison to the adsorbents which have previously been applied in the removal of Co2+and Ni2+ from water... , M.Sc. (Chemistry)
- Full Text:
- Authors: Skosana, Lindiwe
- Date: 2019
- Subjects: Extraction (Chemistry) , Adsorption , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/418824 , uj:35525
- Description: Abstract: The presence of Co2+ and Ni2+ in water is a major concern owing to their non-biodegradable, carcinogenic and mutagenic nature. In recent years, diverse techniques have been applied in their removal from water and upon careful evaluation of some of these techniques, adsorption seemed to be a desirable technique of choice owing to its favourable characteristics as well as its benefits in Co2+ and Ni2+ removal. By virtue of the efficacy of adsorption being governed by an adsorbent, Hollow Carbon Nano Spheres (HCNS) have emerged as attractive adsorbents of choice due to their favourable characteristics in comparison to the adsorbents which have previously been applied in the removal of Co2+and Ni2+ from water... , M.Sc. (Chemistry)
- Full Text:
Early transition metal carbides-multiwalled carbon nanotubes-biopolymer nanocomposites in the application of hydrostatic pressure sensor
- Makhado, Bveledzani Pertunia
- Authors: Makhado, Bveledzani Pertunia
- Date: 2019
- Subjects: Pressure transducers , Hydrostatic pressure , Transition metal carbides , Carbon nanotubes , Nanocomposites (Materials) , Biopolymers , Cellulose acetate
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/417534 , uj:35364
- Description: Abstract: Pressure sensors are very significant and are used in various areas such as automobiles, aerospace, medical industry, energy storage, corrosion protection, electrochromic devices, electrochemical sensor. Most of the pressure sensors in the market are intended to operate either in the air, dry gases and water-based environments. Environmental interference hampered the pressure sensors effectiveness and life cycle. As a consequence, countless measurement and reading mistakes have been reported owing to interferences such as trapped air in a cylinder and elevated humidity, thus decreasing sensitivity and delaying response time. In this study, we determine the resistance sensitivity of a hydrostatic pressure sensor based on cellulose acetate (CA), alpinumisoflavone (BI), multiwalled carbon nanotubes (MWCNTs) and metal carbides (MC) nanocomposites deposited on integrated electrode. We intended to utilize a cost-effective, simple, fast deposition process and fabrication of thermoplastic polymers nanocomposites for pressure sensing device and to study electrical properties of pressure sensing and stability using LCR meter... , M.Sc. (Nanoscience)
- Full Text:
- Authors: Makhado, Bveledzani Pertunia
- Date: 2019
- Subjects: Pressure transducers , Hydrostatic pressure , Transition metal carbides , Carbon nanotubes , Nanocomposites (Materials) , Biopolymers , Cellulose acetate
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/417534 , uj:35364
- Description: Abstract: Pressure sensors are very significant and are used in various areas such as automobiles, aerospace, medical industry, energy storage, corrosion protection, electrochromic devices, electrochemical sensor. Most of the pressure sensors in the market are intended to operate either in the air, dry gases and water-based environments. Environmental interference hampered the pressure sensors effectiveness and life cycle. As a consequence, countless measurement and reading mistakes have been reported owing to interferences such as trapped air in a cylinder and elevated humidity, thus decreasing sensitivity and delaying response time. In this study, we determine the resistance sensitivity of a hydrostatic pressure sensor based on cellulose acetate (CA), alpinumisoflavone (BI), multiwalled carbon nanotubes (MWCNTs) and metal carbides (MC) nanocomposites deposited on integrated electrode. We intended to utilize a cost-effective, simple, fast deposition process and fabrication of thermoplastic polymers nanocomposites for pressure sensing device and to study electrical properties of pressure sensing and stability using LCR meter... , M.Sc. (Nanoscience)
- Full Text:
Effect of organically modified layered double hydroxide and thyme oil loading on the performance of Poly(lactic acid) /Poly[(butylene succinate)-co-adipate] biodegradable polymer blends for cosmetics packaging applications
- Authors: Mhlabeni, Thobile L
- Date: 2019
- Subjects: Nanocomposites (Materials) , Polymeric composites , Polylactic acid , Biodegradable plastics , Lactic acid
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401348 , uj:33537
- Description: Abstract : Poly(lactic acid) (PLA) is a well known biodegradable polymer that can be applied for short term packaging in food and cosmetics. However, PLA is brittle, which significantly limit its industrial packaging applications. Blending PLA and other polymers serve as one of the alternative techniques to improve the toughness of PLA. Blends preparations can be done by melt-compounding using the extrusion technique, which is popular for industrial applications. Blending PLA with equally bio-friendly polymers is preferred to avoid tampering with the degradation rate of PLA. In this study, poly[(butylene succinate) co-adipate] (PBSA) has been investigated as a secondary polymer to improve the flexibility of PLA. Extrusion grades of PLA and PBSA were melt-blended using a twin screw extruder to prepare the PLA/PBSA blends... , M.Tech. (Chemistry)
- Full Text:
- Authors: Mhlabeni, Thobile L
- Date: 2019
- Subjects: Nanocomposites (Materials) , Polymeric composites , Polylactic acid , Biodegradable plastics , Lactic acid
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401348 , uj:33537
- Description: Abstract : Poly(lactic acid) (PLA) is a well known biodegradable polymer that can be applied for short term packaging in food and cosmetics. However, PLA is brittle, which significantly limit its industrial packaging applications. Blending PLA and other polymers serve as one of the alternative techniques to improve the toughness of PLA. Blends preparations can be done by melt-compounding using the extrusion technique, which is popular for industrial applications. Blending PLA with equally bio-friendly polymers is preferred to avoid tampering with the degradation rate of PLA. In this study, poly[(butylene succinate) co-adipate] (PBSA) has been investigated as a secondary polymer to improve the flexibility of PLA. Extrusion grades of PLA and PBSA were melt-blended using a twin screw extruder to prepare the PLA/PBSA blends... , M.Tech. (Chemistry)
- Full Text:
Fabrication and characterization of nanocomposite membrane of polyethersulfone (PES) embedded with hyperbranched polyethyleneimine (HPEI) and bismuth vanadate (BiVO4) nanoparticles for the photocatalytic degradation of triclosan in solution
- Authors: Shaku, Koketjo Madielane
- Date: 2019
- Subjects: Nanocomposites (Materials) , Polyethylene , Polyethylene - Analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401609 , uj:33572
- Description: Abstract : An increase in the production and usage of pharmaceutical and personal care products in various water bodies has attracted significant attention amongst the public and scientists. Classified as emerging pollutants, these pharmaceutical and personal care products ultimately accumulate and contaminate several water bodies through several pathways. Although reported to be found at very low concentrations, exposure to these emerging organic pollutants has adverse health effects to humans. Conventional methods are reported to partially degrade emerging pollutants. Therefore, it is of importance to explore effective and innovative methods for the complete degradation of these pollutants. In this study, a photocatalytic-membrane consisting of bismuth vanadate (BiVO4) nanoparticles, hyperbranched polyethyleneimine (HPEI) and polyethersulfone (PES) were used in the degradation of triclosan. BiVO4 is an n-type semiconductor with excellent properties such as lower band gap and visible light active. However, it has drawbacks such as agglomeration and having lower surface area. HPEI was used as a dispersing agent for the BiVO4 photocatalyst as this polymer has been found to be an excellent template/host for the production of monodispersed and uniform size particles. HPEI can also induce hydrophilic properties on the membrane thus alleviating fouling. BiVO4 was characterised using X-ray Diffraction (XRD) and Raman depicted that spectroscopy. These analyses revealed that there was successful synthesis of the monoclinic phase of BiVO4, as well as a phase transformation between the monoclinic phase and the tetragonal phase upon addition of HPEI within the nanoparticles. The modified membranes showed improved water flux and hydrophilicity (71°- 56°) as compared to the bare PES (75°) upon addition of HPEI and BiVO4. The modified membranes were effective in the photodegradation of triclosan (upto 86%) and this was accompanied by the generation of Cl- ions. , M.Sc. (Nanoscience)
- Full Text:
- Authors: Shaku, Koketjo Madielane
- Date: 2019
- Subjects: Nanocomposites (Materials) , Polyethylene , Polyethylene - Analysis , Nanostructured materials
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/401609 , uj:33572
- Description: Abstract : An increase in the production and usage of pharmaceutical and personal care products in various water bodies has attracted significant attention amongst the public and scientists. Classified as emerging pollutants, these pharmaceutical and personal care products ultimately accumulate and contaminate several water bodies through several pathways. Although reported to be found at very low concentrations, exposure to these emerging organic pollutants has adverse health effects to humans. Conventional methods are reported to partially degrade emerging pollutants. Therefore, it is of importance to explore effective and innovative methods for the complete degradation of these pollutants. In this study, a photocatalytic-membrane consisting of bismuth vanadate (BiVO4) nanoparticles, hyperbranched polyethyleneimine (HPEI) and polyethersulfone (PES) were used in the degradation of triclosan. BiVO4 is an n-type semiconductor with excellent properties such as lower band gap and visible light active. However, it has drawbacks such as agglomeration and having lower surface area. HPEI was used as a dispersing agent for the BiVO4 photocatalyst as this polymer has been found to be an excellent template/host for the production of monodispersed and uniform size particles. HPEI can also induce hydrophilic properties on the membrane thus alleviating fouling. BiVO4 was characterised using X-ray Diffraction (XRD) and Raman depicted that spectroscopy. These analyses revealed that there was successful synthesis of the monoclinic phase of BiVO4, as well as a phase transformation between the monoclinic phase and the tetragonal phase upon addition of HPEI within the nanoparticles. The modified membranes showed improved water flux and hydrophilicity (71°- 56°) as compared to the bare PES (75°) upon addition of HPEI and BiVO4. The modified membranes were effective in the photodegradation of triclosan (upto 86%) and this was accompanied by the generation of Cl- ions. , M.Sc. (Nanoscience)
- Full Text:
Investigation of mechanical properties of polyethylene-based nano-composites
- Authors: Tebeta, Ronny Thapelo
- Date: 2019
- Subjects: Compressors , Carbon nanotubes , Nanocomposites (Materials) , Injection blow molding
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/418308 , uj:35461
- Description: Abstract: Composites and nanocomposites materials are widely used in the newly developing technology for lightweight but strong materials such as in the automotive, aerodynamic, wind turbine and biomedical industries. The advantage of composites or nanocomposites is that they are made of a combination of two or more materials with distinct properties to achieve a new material with different properties from the constituent materials. This work covers the investigation of elastic properties of polymer-based nanocomposites whereby high-density polyethylene (HDPE) is reinforced with single-walled carbon nanotubes (SWCNT) at various weight fractions. SWCNTs nanoparticles are used with polymer HDPE to make composite which has remarkable properties, to enhance the elastic properties of polymer-based nanocomposites. The reason why SWCNTs nanoparticles were used as the strengthening material for HDPE, is because they contain high strength, high melting temperature and are easy to mix with plastics due to their size which is in Nanoscale. On the other hand, polymers are low in strength and lightweight materials which are easy to shape during the manufacturing process and they are inexpensive. Strengthening HDPE with SWCNTs nanoparticles result with a nanocomposite material which is high in strength and low in weight. This composite material holds a great potential to be used in the future for strong but lightweight components application. The objective of the current work was to prepare HDPE/SWCNTs nanocomposites using two different processing methods by reinforcing HDPE with SWCNT nanoparticles at the weight fractions of 0 wt%, 0.2 wt%, 0.4wt%, 0.6 wt%, 0.8wt%, and 1wt%. Then investigate its elastic properties at each weight fraction of SWCNTs and the effect of the processing techniques used on the elastic modulus of the composite. Injection and compression moulding were used to process the tensile test samples of HDPE/SWCNTs nanocomposites. The investigation was conducted used three approaches which include numerical, experimental and analytical. Numerical results were obtained using the finite element method (FEM) incorporated with represented volume element (RVE) to generate the HDPE/SWCNT nanocomposite model with the aid of ANSYS software. The simulations were made using two density-fractions of HDPE and SWCNTs at the same given weight fractions of SWCNTs nanoparticles per HDPE matrix. The modelled results showed that elastic modulus of HDPE/SWCNTs nanocomposite improved by 74 % at the SWCNTs weight fraction of 1 wt% for the density fraction of 1.8 and at the same weight fraction for the density fraction of 2 the improvement was found to be 56 % compared to pure HDPE. This shows that the low-density fraction of SWCNTs fibre and... , M.Ing. (Mechanical Engineering)
- Full Text:
- Authors: Tebeta, Ronny Thapelo
- Date: 2019
- Subjects: Compressors , Carbon nanotubes , Nanocomposites (Materials) , Injection blow molding
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/418308 , uj:35461
- Description: Abstract: Composites and nanocomposites materials are widely used in the newly developing technology for lightweight but strong materials such as in the automotive, aerodynamic, wind turbine and biomedical industries. The advantage of composites or nanocomposites is that they are made of a combination of two or more materials with distinct properties to achieve a new material with different properties from the constituent materials. This work covers the investigation of elastic properties of polymer-based nanocomposites whereby high-density polyethylene (HDPE) is reinforced with single-walled carbon nanotubes (SWCNT) at various weight fractions. SWCNTs nanoparticles are used with polymer HDPE to make composite which has remarkable properties, to enhance the elastic properties of polymer-based nanocomposites. The reason why SWCNTs nanoparticles were used as the strengthening material for HDPE, is because they contain high strength, high melting temperature and are easy to mix with plastics due to their size which is in Nanoscale. On the other hand, polymers are low in strength and lightweight materials which are easy to shape during the manufacturing process and they are inexpensive. Strengthening HDPE with SWCNTs nanoparticles result with a nanocomposite material which is high in strength and low in weight. This composite material holds a great potential to be used in the future for strong but lightweight components application. The objective of the current work was to prepare HDPE/SWCNTs nanocomposites using two different processing methods by reinforcing HDPE with SWCNT nanoparticles at the weight fractions of 0 wt%, 0.2 wt%, 0.4wt%, 0.6 wt%, 0.8wt%, and 1wt%. Then investigate its elastic properties at each weight fraction of SWCNTs and the effect of the processing techniques used on the elastic modulus of the composite. Injection and compression moulding were used to process the tensile test samples of HDPE/SWCNTs nanocomposites. The investigation was conducted used three approaches which include numerical, experimental and analytical. Numerical results were obtained using the finite element method (FEM) incorporated with represented volume element (RVE) to generate the HDPE/SWCNT nanocomposite model with the aid of ANSYS software. The simulations were made using two density-fractions of HDPE and SWCNTs at the same given weight fractions of SWCNTs nanoparticles per HDPE matrix. The modelled results showed that elastic modulus of HDPE/SWCNTs nanocomposite improved by 74 % at the SWCNTs weight fraction of 1 wt% for the density fraction of 1.8 and at the same weight fraction for the density fraction of 2 the improvement was found to be 56 % compared to pure HDPE. This shows that the low-density fraction of SWCNTs fibre and... , M.Ing. (Mechanical Engineering)
- Full Text:
Preparation/synthesis of electrospun polymer/metal oxide nanocomposite fibers and their application in treatment of brines
- Ramutshatsha-Makhwedzha, Denga
- Authors: Ramutshatsha-Makhwedzha, Denga
- Date: 2019
- Subjects: Polymers - Materials , Polymeric composites , Nanocomposites (Materials) , Nanotechnology , Materials science
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/401548 , uj:33565
- Description: Abstract : Many developing countries around the world still lack access to clean fresh water. This refers to water that is free from contaminants as it is highly essential for human livelihood and environment. In countries along the coast, ocean water is the most available water resource; however, it comes at a salt concentration that is very high for human consumption. Most of available water has a salinity of up to 10 000 ppm and seawater consists of dissolved salt concentrations of about 35 000-45 000 ppm. This lead to desalination process being used as an option to treat seawater and this has become one of the most important processes of providing fresh water in developing countries. Therefore, the aim of this study was to investigate the practicability of using nanometer metal oxides and polymer/NMO composite as the potential adsorbents for adsorption desalination of seawater. The quantification of analytes in sample solutions was done using the inductively-coupled plasma atomic emission spectroscopy (ICP-OES). Nanometal oxide composites such as Fe2O3-SiO2, SiO2/Nb2O5/Fe2O3, Fe2O3-SiO2-PAN and zeolite/Fe3O4 adsorbents were used for the adsorptive desalination of saline water. Fe2O3-SiO2, SiO2/Nb2O5/Fe2O3 and zeolite/Fe3O4 adsorbents were prepared using a sol gel method whereas Fe2O3-SiO2-PAN nanocomposite was obtained using in-situ preparation method. The adsorbents were characterized using different techniques such as scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). SEM image of Fe2O3-SiO2 nano composite showed the porous morphological structure. The Fe2O3-SiO2 showed partial crystalline pattern due to silica oxide that has pure amorphous structure, whereas the SiO2/Nb2O5/Fe2O3 has an amorphous structure. TEM structure of α-Fe2O3 has dominant shapes of spherical and some few cubic and hexagonal shapes, the hexagonal shape were also observed on Fe2O3-SiO2 nanocomposite material. SiO2/Nb2O5/Fe2O3 adsorbent resembled a core-like structure. The TEM result of Fe2O3-SiO2-PAN revealed that the crystalline Fe3O4 nanoparticles were encapsulated with PAN polymer that suggests the core-shell structure. EDX-mapping analysis showed the uniform elemental distribution which suggests the successful preparation of the in-situ method... , Ph.D. (Chemistry)
- Full Text:
- Authors: Ramutshatsha-Makhwedzha, Denga
- Date: 2019
- Subjects: Polymers - Materials , Polymeric composites , Nanocomposites (Materials) , Nanotechnology , Materials science
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/401548 , uj:33565
- Description: Abstract : Many developing countries around the world still lack access to clean fresh water. This refers to water that is free from contaminants as it is highly essential for human livelihood and environment. In countries along the coast, ocean water is the most available water resource; however, it comes at a salt concentration that is very high for human consumption. Most of available water has a salinity of up to 10 000 ppm and seawater consists of dissolved salt concentrations of about 35 000-45 000 ppm. This lead to desalination process being used as an option to treat seawater and this has become one of the most important processes of providing fresh water in developing countries. Therefore, the aim of this study was to investigate the practicability of using nanometer metal oxides and polymer/NMO composite as the potential adsorbents for adsorption desalination of seawater. The quantification of analytes in sample solutions was done using the inductively-coupled plasma atomic emission spectroscopy (ICP-OES). Nanometal oxide composites such as Fe2O3-SiO2, SiO2/Nb2O5/Fe2O3, Fe2O3-SiO2-PAN and zeolite/Fe3O4 adsorbents were used for the adsorptive desalination of saline water. Fe2O3-SiO2, SiO2/Nb2O5/Fe2O3 and zeolite/Fe3O4 adsorbents were prepared using a sol gel method whereas Fe2O3-SiO2-PAN nanocomposite was obtained using in-situ preparation method. The adsorbents were characterized using different techniques such as scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET). SEM image of Fe2O3-SiO2 nano composite showed the porous morphological structure. The Fe2O3-SiO2 showed partial crystalline pattern due to silica oxide that has pure amorphous structure, whereas the SiO2/Nb2O5/Fe2O3 has an amorphous structure. TEM structure of α-Fe2O3 has dominant shapes of spherical and some few cubic and hexagonal shapes, the hexagonal shape were also observed on Fe2O3-SiO2 nanocomposite material. SiO2/Nb2O5/Fe2O3 adsorbent resembled a core-like structure. The TEM result of Fe2O3-SiO2-PAN revealed that the crystalline Fe3O4 nanoparticles were encapsulated with PAN polymer that suggests the core-shell structure. EDX-mapping analysis showed the uniform elemental distribution which suggests the successful preparation of the in-situ method... , Ph.D. (Chemistry)
- Full Text:
Synthesis and modifications of polymer-based carbon/metal organic framework composites for hydrogen storage applications
- Authors: Molefe, Lerato
- Date: 2019
- Subjects: Polymeric composites , Carbon nanotubes , Carbon composites , Nanocomposites (Materials)
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/417836 , uj:35402
- Description: Abstract: The South African energy landscape is dominated by carbon dioxide (CO2) emitting coal combustion which is currently plentiful and cheap however because of its finite nature, it will soon diminish. With the current growing population and increasing energy need, research scientists all over the world are continuously working towards shifting to cleaner renewable energy sources of which hydrogen (H2) is a promising candidate. Hydrogen has a high gravimetric energy density than any other fuel and its combustion in pure oxygen only produces water vapour and heat. However, since it is very light and as a result has a low volumetric energy density, its storage is very difficult. Generally, adsorbents materials such as metal-organic frameworks (MOFs) such as Materials Institute Lavoisier (MIL-101(Cr)) and Universitetet i Oslo (UiO-66(Zr)) as well as porous carbons such as zeolite templated carbon (ZTC) have been well investigated for H2 storage due to their unique properties such as extremely high surface areas and ultrahigh porosities. However, their great potential in H2 storage applications is limited by their lack of immediate processability, because they are obtained as fine powders in their as-synthesised form. For these materials to gain practical applications in H2 storage they must be shaped into mechanically stable and easy to handle bodies like monoliths. The process of shaping MOFs and carbon powders often includes the use of various non-porous polymers and inorganic materials as binders and that often results in pore-blocking effects and low H2 uptake... , Ph.D. (Chemistry)
- Full Text:
- Authors: Molefe, Lerato
- Date: 2019
- Subjects: Polymeric composites , Carbon nanotubes , Carbon composites , Nanocomposites (Materials)
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/417836 , uj:35402
- Description: Abstract: The South African energy landscape is dominated by carbon dioxide (CO2) emitting coal combustion which is currently plentiful and cheap however because of its finite nature, it will soon diminish. With the current growing population and increasing energy need, research scientists all over the world are continuously working towards shifting to cleaner renewable energy sources of which hydrogen (H2) is a promising candidate. Hydrogen has a high gravimetric energy density than any other fuel and its combustion in pure oxygen only produces water vapour and heat. However, since it is very light and as a result has a low volumetric energy density, its storage is very difficult. Generally, adsorbents materials such as metal-organic frameworks (MOFs) such as Materials Institute Lavoisier (MIL-101(Cr)) and Universitetet i Oslo (UiO-66(Zr)) as well as porous carbons such as zeolite templated carbon (ZTC) have been well investigated for H2 storage due to their unique properties such as extremely high surface areas and ultrahigh porosities. However, their great potential in H2 storage applications is limited by their lack of immediate processability, because they are obtained as fine powders in their as-synthesised form. For these materials to gain practical applications in H2 storage they must be shaped into mechanically stable and easy to handle bodies like monoliths. The process of shaping MOFs and carbon powders often includes the use of various non-porous polymers and inorganic materials as binders and that often results in pore-blocking effects and low H2 uptake... , Ph.D. (Chemistry)
- Full Text:
Synthesis, characterization and application of rGO-SnO2-Fe2O3-TiO2 AND rGO-Fe2O3-SnO2-TiO2 ternary nano-composite as electrodes in sodium-ion batteries
- Authors: Ramike, Matshidiso Patricia
- Date: 2019
- Subjects: Sodium-sulfur batteries , Anodes , Electric batteries - Electrodes , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/295504 , uj:32180
- Description: Abstract: Rechargeable batteries are an integral part of modern life and technology development as energy sources and energy storage systems. Currently, lithium batteries’ (both rechargeable and non-rechargeable) features and consequently its performance surpasses those of its counterparts by far. For that reason, lithium batteries are leading the battery market. However, their rapid growth and demand is projected to exceed the limited recoverable resources of lithium. Therefore, sourcing equivalent battery types and/or technologies is crucial. Sodium-ion rechargeable batteries are the most credible alternative mainly due to the abundance, even distribution and feasible recovery of this resource. In addition, sodium and lithium have similar physical and chemical properties and thus similar energy storing / supplying mechanisms. However, the larger and heavier sodium-ion has inherently slower diffusion rates and thus experiences a few challenges with the lithium cell configuration such as compatible active electrode material. Therefore, the development of sodium-ion electrode material is the key to the success and commercialization of sodium-ion batteries. The SnO2 and Fe2O3 metal oxides have been reported to exhibit high capacities when used as anode material in sodium-ion batteries although at short life cycles due to the extreme volume expansion they experience during cycling. On the other hand, graphene oxide and TiO2 have been reported to exhibit moderate reversible capacity but for long life cycles due to their insignificant volume change during cycling. Hybrids of the four materials in different combinations have been reported to exhibit high reversible capacities and long-life cycles. For that reason, in this study the rGO-SnO2-Fe2O3-TiO2 and rGO-Fe2O3-SnO2-TiO2 ternary nanocomposites were synthesized, characterized and evaluated as anode material in sodium-ion battery half cells. Graphene oxide was synthesized by chemical exfoliation of graphite and coated with layers of SnO2, Fe2O3, and TiO2 metal oxides in different combinations by means of the solvothermal and/or hydrothermal and/or co-precipitation methods. When the synthesized nanomaterial were analyzed with the FTIR, Raman spectroscopy, SEM, TEM, TGA, BET, UV-Vis spectroscopy, and XRD analytical techniques; their physical, chemical and optical properties were positively matched to their pure compounds. The electrochemical performance of the rGO-SnO2-Fe2O3-TiO2 and rGO-Fe2O3-SnO2-TiO2 ternary nanocomposites was evaluated using sodium-ion battery half cells. The half cells consisted of a counter and reference electrode made from sodium metal, 1 M NaClO4/PC electrolyte solution in addition to the ternary nanocomposites as the active material in the working electrodes. The cells were assembled in a nitrogen filled glove box with oxygen and moisture concentration of ≤0.5 ppm and 62 ppm — 69 ppm respectively. The ternary nanocomposites exhibited uncharacteristically low... , M.Tech. (Chemistry)
- Full Text:
- Authors: Ramike, Matshidiso Patricia
- Date: 2019
- Subjects: Sodium-sulfur batteries , Anodes , Electric batteries - Electrodes , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/295504 , uj:32180
- Description: Abstract: Rechargeable batteries are an integral part of modern life and technology development as energy sources and energy storage systems. Currently, lithium batteries’ (both rechargeable and non-rechargeable) features and consequently its performance surpasses those of its counterparts by far. For that reason, lithium batteries are leading the battery market. However, their rapid growth and demand is projected to exceed the limited recoverable resources of lithium. Therefore, sourcing equivalent battery types and/or technologies is crucial. Sodium-ion rechargeable batteries are the most credible alternative mainly due to the abundance, even distribution and feasible recovery of this resource. In addition, sodium and lithium have similar physical and chemical properties and thus similar energy storing / supplying mechanisms. However, the larger and heavier sodium-ion has inherently slower diffusion rates and thus experiences a few challenges with the lithium cell configuration such as compatible active electrode material. Therefore, the development of sodium-ion electrode material is the key to the success and commercialization of sodium-ion batteries. The SnO2 and Fe2O3 metal oxides have been reported to exhibit high capacities when used as anode material in sodium-ion batteries although at short life cycles due to the extreme volume expansion they experience during cycling. On the other hand, graphene oxide and TiO2 have been reported to exhibit moderate reversible capacity but for long life cycles due to their insignificant volume change during cycling. Hybrids of the four materials in different combinations have been reported to exhibit high reversible capacities and long-life cycles. For that reason, in this study the rGO-SnO2-Fe2O3-TiO2 and rGO-Fe2O3-SnO2-TiO2 ternary nanocomposites were synthesized, characterized and evaluated as anode material in sodium-ion battery half cells. Graphene oxide was synthesized by chemical exfoliation of graphite and coated with layers of SnO2, Fe2O3, and TiO2 metal oxides in different combinations by means of the solvothermal and/or hydrothermal and/or co-precipitation methods. When the synthesized nanomaterial were analyzed with the FTIR, Raman spectroscopy, SEM, TEM, TGA, BET, UV-Vis spectroscopy, and XRD analytical techniques; their physical, chemical and optical properties were positively matched to their pure compounds. The electrochemical performance of the rGO-SnO2-Fe2O3-TiO2 and rGO-Fe2O3-SnO2-TiO2 ternary nanocomposites was evaluated using sodium-ion battery half cells. The half cells consisted of a counter and reference electrode made from sodium metal, 1 M NaClO4/PC electrolyte solution in addition to the ternary nanocomposites as the active material in the working electrodes. The cells were assembled in a nitrogen filled glove box with oxygen and moisture concentration of ≤0.5 ppm and 62 ppm — 69 ppm respectively. The ternary nanocomposites exhibited uncharacteristically low... , M.Tech. (Chemistry)
- Full Text:
The development of a dendrimer-gold nanocomposite electrochemical sensor for the detection of lead (ii) ion in water
- Authors: Mokgwadi, Jalda Kgaogelo
- Date: 2019
- Subjects: Nanocomposites (Materials) , Electrochemical sensors , Drinking water|xLead content , Nanoscience
- Language: English
- Type: Master (Thesis)
- Identifier: http://hdl.handle.net/10210/401397 , uj:33543
- Description: Abstract : In South Africa, industrial development and mining sustain the economy. Unfortunately, the effluents from these industries introduce heavy metal pollutants such as lead (Pb2+) into the environmental water. Pb2+ is widely recognized as one of the highly toxic and non-biodegradable metal that poses serious health problems and even death. This study presents a method of heavy metal analysis by modifying glassy carbon electrode (GCE) with gold nanoparticles (AuNPs) and generation 2 (G2) poly(propyleneimine) dendrimer (PPI) to provide a highly sensitive electrochemical sensor for the determination of Pb2+ ions in water using square wave anodic stripping voltammetry (SWASV). The co-deposition of PPI and AuNPs on the surface of GCE was confirmed by atomic force microscopy (AFM). Voltammetric probing showed that the GCE-PPI/AuNPs platform exhibited reversible electrochemistry and conductivity in [Fe(CN)6]3 −/4 – redox probe. The electroactive surface area of the bare GCE, GCE-PPI, GCE-AuNPs and GCE-PPI/AuNPs were also estimated in order to illustrate that the prepared PPI/AuNPs nanocomposite could improve the surface area and conductivity of the GCE and was found to be 8.17 mm2 for bare GCE, 10.84 mm2 for GCE-PPI, 11.03 mm2 for GCE-AuNPs and 11.13 mm2 for GCE-PPI/AuNPs. The electroactive surface area of GCE-PPI/AuNPs modified electrode increased by approximately 36.23% as compared to bare GCE, which provided an effective evidence for the superior conductivity of PPI/AuNPs as expected. The effect of different electrochemical parameters on the sensitivity of the sensor for the Pb2+ detection was also scrutinized, including supporting electrolyte (HNO3), deposition potential (-800 mV) and deposition time (150s). The sensor was applied in the detection of different standard concentrations of Pb2+, linear range of (1 ppb-100 ppb) with detection limit of 0.96 ppb. The GCE-PPI/AuNPs sensor was then applied to detect Pb2+ in tap water whose results were validated with ICP-OES. , M.Sc. (Nanoscience)
- Full Text:
- Authors: Mokgwadi, Jalda Kgaogelo
- Date: 2019
- Subjects: Nanocomposites (Materials) , Electrochemical sensors , Drinking water|xLead content , Nanoscience
- Language: English
- Type: Master (Thesis)
- Identifier: http://hdl.handle.net/10210/401397 , uj:33543
- Description: Abstract : In South Africa, industrial development and mining sustain the economy. Unfortunately, the effluents from these industries introduce heavy metal pollutants such as lead (Pb2+) into the environmental water. Pb2+ is widely recognized as one of the highly toxic and non-biodegradable metal that poses serious health problems and even death. This study presents a method of heavy metal analysis by modifying glassy carbon electrode (GCE) with gold nanoparticles (AuNPs) and generation 2 (G2) poly(propyleneimine) dendrimer (PPI) to provide a highly sensitive electrochemical sensor for the determination of Pb2+ ions in water using square wave anodic stripping voltammetry (SWASV). The co-deposition of PPI and AuNPs on the surface of GCE was confirmed by atomic force microscopy (AFM). Voltammetric probing showed that the GCE-PPI/AuNPs platform exhibited reversible electrochemistry and conductivity in [Fe(CN)6]3 −/4 – redox probe. The electroactive surface area of the bare GCE, GCE-PPI, GCE-AuNPs and GCE-PPI/AuNPs were also estimated in order to illustrate that the prepared PPI/AuNPs nanocomposite could improve the surface area and conductivity of the GCE and was found to be 8.17 mm2 for bare GCE, 10.84 mm2 for GCE-PPI, 11.03 mm2 for GCE-AuNPs and 11.13 mm2 for GCE-PPI/AuNPs. The electroactive surface area of GCE-PPI/AuNPs modified electrode increased by approximately 36.23% as compared to bare GCE, which provided an effective evidence for the superior conductivity of PPI/AuNPs as expected. The effect of different electrochemical parameters on the sensitivity of the sensor for the Pb2+ detection was also scrutinized, including supporting electrolyte (HNO3), deposition potential (-800 mV) and deposition time (150s). The sensor was applied in the detection of different standard concentrations of Pb2+, linear range of (1 ppb-100 ppb) with detection limit of 0.96 ppb. The GCE-PPI/AuNPs sensor was then applied to detect Pb2+ in tap water whose results were validated with ICP-OES. , M.Sc. (Nanoscience)
- Full Text:
An investigation into the role of nanoclay and its localization on the micro-structural development and properties of polypropylene-based immiscible blends
- Authors: Mofokeng, Tladi Gideon
- Date: 2018
- Subjects: Nanocomposites (Materials) , Polymeric composites , Polymer clay
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/278759 , uj:29920
- Description: Ph.D. (Chemistry) , Abstract: This study deals with the influence of nanoclay localization on the morphological development and properties of melt-mixed PP/LDPE/clay and PP/EVA/clay nanocomposites. The main objective of this work was to develop PP/LDPE and PP/EVA-based hybrid materials with better compatibility, thermal stability, and impact strength, and at the same time with relatively good strength, flexibility, and elastic modulus. Blends with various compositions were prepared through melt extrusion. The morphological and dynamic characterizations show that the PP/EVA blends were immiscible for the investigated blend compositions. The presence of EVA in PP induced a beta (β)-phase formation of PP, thereby increasing the elongation-at-break and impact strength. The PP/LDPE blend morphology comprised a major matrix phase and a minor phase, with sub-inclusions of the major matrix within the minor phase. The PP/LDPE blends exhibited partial miscibility at low contents (< 20 wt%) of either phase; however, the phases were immiscible at higher contents. The PP/LDPE blend composition and morphology influenced the impact strength and elongation-at-break. The 80/20 PP/LDPE and 80/20 PP/EVA blends offered a balance between the mechanical and material properties essential for flexible packaging applications. Thereafter, 4 wt% nanoclay was added to modify the morphologies of the blends. The PP/LDPE/clay nanocomposites investigated in this study contained two different types of compatibilizers [maleic anhydride-graft polyethylene (PE-g-MA) and maleic anhydride-graft-polypropylene (PP-g-MA)], which manipulated the localization of clay in different phases. The morphological characterization results show that the nano/micro-structure of the PP/LDPE (80/20) blend could be controlled by incorporating the nanoclay alone or by adding a mixture of organoclay and maleated compatibilizers, a feature which significantly improved the thermal stability and tensile and rheological properties of the blend composites. The...
- Full Text:
- Authors: Mofokeng, Tladi Gideon
- Date: 2018
- Subjects: Nanocomposites (Materials) , Polymeric composites , Polymer clay
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/278759 , uj:29920
- Description: Ph.D. (Chemistry) , Abstract: This study deals with the influence of nanoclay localization on the morphological development and properties of melt-mixed PP/LDPE/clay and PP/EVA/clay nanocomposites. The main objective of this work was to develop PP/LDPE and PP/EVA-based hybrid materials with better compatibility, thermal stability, and impact strength, and at the same time with relatively good strength, flexibility, and elastic modulus. Blends with various compositions were prepared through melt extrusion. The morphological and dynamic characterizations show that the PP/EVA blends were immiscible for the investigated blend compositions. The presence of EVA in PP induced a beta (β)-phase formation of PP, thereby increasing the elongation-at-break and impact strength. The PP/LDPE blend morphology comprised a major matrix phase and a minor phase, with sub-inclusions of the major matrix within the minor phase. The PP/LDPE blends exhibited partial miscibility at low contents (< 20 wt%) of either phase; however, the phases were immiscible at higher contents. The PP/LDPE blend composition and morphology influenced the impact strength and elongation-at-break. The 80/20 PP/LDPE and 80/20 PP/EVA blends offered a balance between the mechanical and material properties essential for flexible packaging applications. Thereafter, 4 wt% nanoclay was added to modify the morphologies of the blends. The PP/LDPE/clay nanocomposites investigated in this study contained two different types of compatibilizers [maleic anhydride-graft polyethylene (PE-g-MA) and maleic anhydride-graft-polypropylene (PP-g-MA)], which manipulated the localization of clay in different phases. The morphological characterization results show that the nano/micro-structure of the PP/LDPE (80/20) blend could be controlled by incorporating the nanoclay alone or by adding a mixture of organoclay and maleated compatibilizers, a feature which significantly improved the thermal stability and tensile and rheological properties of the blend composites. The...
- Full Text:
Conducting nanocomposites for the removal of heavy metals from wastewater
- Authors: Kera, Nazia Hassan
- Date: 2018
- Subjects: Heavy metals - Absorption and adsorption , Sewage - Purification - Heavy metals removal , Water - Purification , Nanocomposites (Materials) , Water chemistry
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/366683 , http://hdl.handle.net/10210/278783 , uj:29923
- Description: Ph.D. (Chemistry) , Abstract: Hexavalent chromium, Cr(VI), is a toxic heavy metal pollutant that occurs in wastewater produced from mining and industrial activities such as leather tanning, chrome plating, wood preservation and alloy manufacture. Cr(VI) released into the environment is of concern due to its high mobility in water and soil and harmful effects on human health. The treatment of wastewater is necessary to prevent Cr(VI) contamination of water bodies in the environment. Conducting polymers, such as polypyrrole (PPy) and polyaniline (PANI), have the potential to be used as adsorbents for Cr(VI) in wastewater due to their abundant nitrogen-containing functional groups, anion-exchange sites and capacity to reduce Cr(VI) to the significantly less toxic, trivalent chromium, Cr(III). However, conducting polymers have shown low adsorption capacities for Cr(VI) due to agglomeration of particles and are also difficult to separate from treated water. The focus of this study was on the development of conducting polymer composites for the treatment of wastewater containing Cr(VI). In particular, the aim of the research carried out was the modification of conducting polymers to obtain adsorbents with high adsorption capacities for Cr(VI) that are well-suited towards water treatment applications. Three novel conducting polymer composites were prepared in this study, namely, polypyrrole/2,5-diaminobenzenesulfonic acid (PPy/DABSA) composite, polypyrrole-polyaniline/iron oxide (PPy-PANI/Fe3O4) magnetic nanocomposite and polypyrrole-m-phenylenediamine (PPy-mPD) polymer for the desired application of removing Cr(VI) from industrial wastewater. The composites were synthesized easily and effectively by in situ chemical oxidative polymerization and their physicochemical properties characterized using various techniques including attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area analysis. Batch studies were carried out to investigate the effect of parameters such as initial solution pH, adsorbent dose, initial Cr(VI) concentration, temperature and co-existing ions in solution on Cr(VI) removal by the different composites...
- Full Text:
- Authors: Kera, Nazia Hassan
- Date: 2018
- Subjects: Heavy metals - Absorption and adsorption , Sewage - Purification - Heavy metals removal , Water - Purification , Nanocomposites (Materials) , Water chemistry
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/366683 , http://hdl.handle.net/10210/278783 , uj:29923
- Description: Ph.D. (Chemistry) , Abstract: Hexavalent chromium, Cr(VI), is a toxic heavy metal pollutant that occurs in wastewater produced from mining and industrial activities such as leather tanning, chrome plating, wood preservation and alloy manufacture. Cr(VI) released into the environment is of concern due to its high mobility in water and soil and harmful effects on human health. The treatment of wastewater is necessary to prevent Cr(VI) contamination of water bodies in the environment. Conducting polymers, such as polypyrrole (PPy) and polyaniline (PANI), have the potential to be used as adsorbents for Cr(VI) in wastewater due to their abundant nitrogen-containing functional groups, anion-exchange sites and capacity to reduce Cr(VI) to the significantly less toxic, trivalent chromium, Cr(III). However, conducting polymers have shown low adsorption capacities for Cr(VI) due to agglomeration of particles and are also difficult to separate from treated water. The focus of this study was on the development of conducting polymer composites for the treatment of wastewater containing Cr(VI). In particular, the aim of the research carried out was the modification of conducting polymers to obtain adsorbents with high adsorption capacities for Cr(VI) that are well-suited towards water treatment applications. Three novel conducting polymer composites were prepared in this study, namely, polypyrrole/2,5-diaminobenzenesulfonic acid (PPy/DABSA) composite, polypyrrole-polyaniline/iron oxide (PPy-PANI/Fe3O4) magnetic nanocomposite and polypyrrole-m-phenylenediamine (PPy-mPD) polymer for the desired application of removing Cr(VI) from industrial wastewater. The composites were synthesized easily and effectively by in situ chemical oxidative polymerization and their physicochemical properties characterized using various techniques including attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area analysis. Batch studies were carried out to investigate the effect of parameters such as initial solution pH, adsorbent dose, initial Cr(VI) concentration, temperature and co-existing ions in solution on Cr(VI) removal by the different composites...
- Full Text:
Development of a three layer film using EVOH and LDPE blends for packaging material applications
- Authors: Motale, Mamafa Jonas
- Date: 2018
- Subjects: Polyethylene , Reinforced plastics , Ethylene , Nanocomposites (Materials) , Polymerization
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279562 , uj:30024
- Description: M.Sc. (Chemistry) , Abstract: This study evaluates the use of low density polyethylene (LDPE)/ethylene vinyl alcohol (EVOH) blend as a tie-layer in multi-layer film construction for packaging application. Compositions of LDPE and EVOH blends were varied from 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80 and 10/90 in order to identify a suitable blend to be used as a tie-layer. These blend ratios were melt-compounded by a co-rotating twin screw extruder. Characterization techniques such as scanning electron microscopy (SEM), Instron tensile tester, Charpy impact tester, rheometer, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), heat deflection temperature (HDT) and melt flow index (MFI) were used to identify blends with desirable properties. SEM morphologies showed that LDPE and EVOH formed phase separated structures which indicated that the blends are immiscible. In 90/10 and 80/20 LPDE/EVOH blends, EVOH formed droplets within the LDPE matrix. Co-continuous morphologies were seen on 70/30, 60/40 and 50/50 LDPE/EVOH blends while LDPE formed mixture of droplets and rod-like structures in blend ratios containing high contents of EVOH. Tensile measurement showed that modulus of the blends increased with increasing EVOH content. The moduli were designated as region I, II and III and were related to the dispersion of the phases in the blends. Blend of 90/10 LDPE/EVOH had a slight improvement in modulus when compared to neat LDPE. Furthermore, the elongation at break and impact resistance of this blend were higher than those of other blend ratios. Rheological studies were conducted to study the viscosity as a function of shear rate and confirmed that neat LDPE present higher viscosity than neat EVOH. Interestingly, 80/20 LDPE/EVOH blend showed higher viscosity than neat LDPE and...
- Full Text:
- Authors: Motale, Mamafa Jonas
- Date: 2018
- Subjects: Polyethylene , Reinforced plastics , Ethylene , Nanocomposites (Materials) , Polymerization
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279562 , uj:30024
- Description: M.Sc. (Chemistry) , Abstract: This study evaluates the use of low density polyethylene (LDPE)/ethylene vinyl alcohol (EVOH) blend as a tie-layer in multi-layer film construction for packaging application. Compositions of LDPE and EVOH blends were varied from 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80 and 10/90 in order to identify a suitable blend to be used as a tie-layer. These blend ratios were melt-compounded by a co-rotating twin screw extruder. Characterization techniques such as scanning electron microscopy (SEM), Instron tensile tester, Charpy impact tester, rheometer, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), heat deflection temperature (HDT) and melt flow index (MFI) were used to identify blends with desirable properties. SEM morphologies showed that LDPE and EVOH formed phase separated structures which indicated that the blends are immiscible. In 90/10 and 80/20 LPDE/EVOH blends, EVOH formed droplets within the LDPE matrix. Co-continuous morphologies were seen on 70/30, 60/40 and 50/50 LDPE/EVOH blends while LDPE formed mixture of droplets and rod-like structures in blend ratios containing high contents of EVOH. Tensile measurement showed that modulus of the blends increased with increasing EVOH content. The moduli were designated as region I, II and III and were related to the dispersion of the phases in the blends. Blend of 90/10 LDPE/EVOH had a slight improvement in modulus when compared to neat LDPE. Furthermore, the elongation at break and impact resistance of this blend were higher than those of other blend ratios. Rheological studies were conducted to study the viscosity as a function of shear rate and confirmed that neat LDPE present higher viscosity than neat EVOH. Interestingly, 80/20 LDPE/EVOH blend showed higher viscosity than neat LDPE and...
- Full Text:
Efficiency of modified WO3 nanoparticles on the photoreduction of metal ions in water
- Authors: Thwala, Mpendulo Mphumelelo
- Date: 2018
- Subjects: Water - Purification - Photocatalysis , Photocatalysis , Doped semiconductors , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279265 , uj:29988
- Description: M.Sc. (Chemistry) , Abstract: With an increased need for clean water in South Africa, there is a need to find more techniques for water purification. The improved standards required by the World Health Organization (WHO) has led to a quest of technological advancements in finding more effective and cost friendly techniques for water purification. The use of nanoparticles (semiconductor metal oxides) has emerged as a promising approach to purify water, removing pollutants from water to low concentrations that meet the WHO standards. Tungsten trioxide (WO3) is considered as one of the best semiconductor photocatalyst capable of photodegradading organic compounds. Pristine WO3 is, however not capable of photoreducing inorganic substances in water. Therefore, this work presents a modified WO3 to improve the photocatalytic activity in the photoreduction of Cr(VI) and Cu(II) in wastewater. The modification was carried out through doping with magnesium and yttrium metals respectively. Although these aforementioned dopant metals come costly, the synthesis routes and efficiency of the doped WO3 in the reduction of Cr(VI) and Cu(II) is worthwhile. The hydrothermal method was used to synthesize WO3, Mg doped WO3 and Y doped WO3 nanoparticles. In order to understand the structure of the synthesized nanoparticles, the nanoparticles were characterized using X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), Filed emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, zeta potential, Brunauer–Emmett– Teller (BET) surface area, UV-visible spectroscopy (UV-vis), X-Ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The as-synthesized materials were confirmed to be composed of crystalline monoclinic polymorphs as shown by the XRD, FTIR and Raman spectroscopy. The average crystallite size was found to be around 32 nm with an average particle strain of 0.002498. The particle sizes were found to be of 141 nm in average as confirmed by TEM. The difference in d spacing were observed for the doped nanoparticles...
- Full Text:
- Authors: Thwala, Mpendulo Mphumelelo
- Date: 2018
- Subjects: Water - Purification - Photocatalysis , Photocatalysis , Doped semiconductors , Nanocomposites (Materials)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279265 , uj:29988
- Description: M.Sc. (Chemistry) , Abstract: With an increased need for clean water in South Africa, there is a need to find more techniques for water purification. The improved standards required by the World Health Organization (WHO) has led to a quest of technological advancements in finding more effective and cost friendly techniques for water purification. The use of nanoparticles (semiconductor metal oxides) has emerged as a promising approach to purify water, removing pollutants from water to low concentrations that meet the WHO standards. Tungsten trioxide (WO3) is considered as one of the best semiconductor photocatalyst capable of photodegradading organic compounds. Pristine WO3 is, however not capable of photoreducing inorganic substances in water. Therefore, this work presents a modified WO3 to improve the photocatalytic activity in the photoreduction of Cr(VI) and Cu(II) in wastewater. The modification was carried out through doping with magnesium and yttrium metals respectively. Although these aforementioned dopant metals come costly, the synthesis routes and efficiency of the doped WO3 in the reduction of Cr(VI) and Cu(II) is worthwhile. The hydrothermal method was used to synthesize WO3, Mg doped WO3 and Y doped WO3 nanoparticles. In order to understand the structure of the synthesized nanoparticles, the nanoparticles were characterized using X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), Filed emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, zeta potential, Brunauer–Emmett– Teller (BET) surface area, UV-visible spectroscopy (UV-vis), X-Ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). The as-synthesized materials were confirmed to be composed of crystalline monoclinic polymorphs as shown by the XRD, FTIR and Raman spectroscopy. The average crystallite size was found to be around 32 nm with an average particle strain of 0.002498. The particle sizes were found to be of 141 nm in average as confirmed by TEM. The difference in d spacing were observed for the doped nanoparticles...
- Full Text:
Mixed-metal oxide conducting polymer nanocomposites for the removal of fluoride and chromium(VI) from aqueous solution
- Authors: Chigondo, Marko
- Date: 2018
- Subjects: Nanocomposites (Materials) , Water - Purification - Adsorption , Water - Purification - Chromium removal , Water - Purification - Fluoride removal
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/292685 , uj:31810
- Description: Abstract: Water is an indispensable natural resource for sustaining life which is undoubtedly not free in all places. The chemical composition of surface or underground waters is one of the principal aspects upon which the relevancy of water for domestic, industrial or agricultural purposes hinges upon. Inorganic anions are commonly in existence in water; nonetheless, some of these including oxy-anions, are undesirable and continually accountable for the grave environmental and health problems. Such ions like arsenic (As(V)), hexavalent chromium(Cr(VI)), fluoride (F‒) phosphate (PO43‒) and nitrate (NO3‒) when in exceeding maximum limits, constitute some of the most hazardous water pollutants. Fluoride, at low a concentration of 0.8-1.5 mg/L as recommended by World Health Organisation (WHO) can prevent tooth decay and contribute to the development of strong bones, especially in young children. However, at higher concentrations it has catastrophic health effects ranging from dental related problems to debilitating skeletal fluorosis as well as affecting body parts like the muscles, brain, lungs, kidneys, thyroid, reproduction and enzymes. Its high concentration in ground water is primarily owing to the weathering of fluoride rich minerals, high ash volcanic eruptions and many anthropogenic activities. On the other hand, industrial activities such as electroplating, leather tanning, dye production, ferrochrome production, wood preservation, mining and paints manufacture have indirectly led to the discharge of Cr(VI) ions into environmental water. Cr(VI) is one of the most toxic, highly soluble and mobile anions in the environment which causes health problems in the form of dermatitis, damage to the liver, lung and skin cancer, skin irritation and internal haemorrhage. The WHO recommended level of Cr(VI) is 0.1 mg/L in surface waters and 0.05 mg/L in drinking water. Consequently, sustainable technologies have been developed to remove fluoride and Cr(VI) ions from water ranging from chemical precipitation, reverse osmosis, electrochemical methods, adsorption, membrane processes, ion exchange and phytoremediation. Among these techniques, adsorption has shown superiority, attributed to its simplicity in design, low operating costs, efficiency and reversibility. Several adsorbents have been utilised for adsorption successfully. However, some drawbacks such as high cost, low selectivity, narrow pH ranges, low adsorption capacity, slow adsorption and poor mechanical strength have been encountered with some of the adsorbent materials. Nano-metal oxides (NMOs) and conduction polymers have a better potential as adsorbents physical and chemical properties. However they have problems of agglomeration, hence low adsorption capacity and difficult to separate from aqueous media. More studies on modification and... , Ph.D. (Chemistry)
- Full Text:
- Authors: Chigondo, Marko
- Date: 2018
- Subjects: Nanocomposites (Materials) , Water - Purification - Adsorption , Water - Purification - Chromium removal , Water - Purification - Fluoride removal
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/292685 , uj:31810
- Description: Abstract: Water is an indispensable natural resource for sustaining life which is undoubtedly not free in all places. The chemical composition of surface or underground waters is one of the principal aspects upon which the relevancy of water for domestic, industrial or agricultural purposes hinges upon. Inorganic anions are commonly in existence in water; nonetheless, some of these including oxy-anions, are undesirable and continually accountable for the grave environmental and health problems. Such ions like arsenic (As(V)), hexavalent chromium(Cr(VI)), fluoride (F‒) phosphate (PO43‒) and nitrate (NO3‒) when in exceeding maximum limits, constitute some of the most hazardous water pollutants. Fluoride, at low a concentration of 0.8-1.5 mg/L as recommended by World Health Organisation (WHO) can prevent tooth decay and contribute to the development of strong bones, especially in young children. However, at higher concentrations it has catastrophic health effects ranging from dental related problems to debilitating skeletal fluorosis as well as affecting body parts like the muscles, brain, lungs, kidneys, thyroid, reproduction and enzymes. Its high concentration in ground water is primarily owing to the weathering of fluoride rich minerals, high ash volcanic eruptions and many anthropogenic activities. On the other hand, industrial activities such as electroplating, leather tanning, dye production, ferrochrome production, wood preservation, mining and paints manufacture have indirectly led to the discharge of Cr(VI) ions into environmental water. Cr(VI) is one of the most toxic, highly soluble and mobile anions in the environment which causes health problems in the form of dermatitis, damage to the liver, lung and skin cancer, skin irritation and internal haemorrhage. The WHO recommended level of Cr(VI) is 0.1 mg/L in surface waters and 0.05 mg/L in drinking water. Consequently, sustainable technologies have been developed to remove fluoride and Cr(VI) ions from water ranging from chemical precipitation, reverse osmosis, electrochemical methods, adsorption, membrane processes, ion exchange and phytoremediation. Among these techniques, adsorption has shown superiority, attributed to its simplicity in design, low operating costs, efficiency and reversibility. Several adsorbents have been utilised for adsorption successfully. However, some drawbacks such as high cost, low selectivity, narrow pH ranges, low adsorption capacity, slow adsorption and poor mechanical strength have been encountered with some of the adsorbent materials. Nano-metal oxides (NMOs) and conduction polymers have a better potential as adsorbents physical and chemical properties. However they have problems of agglomeration, hence low adsorption capacity and difficult to separate from aqueous media. More studies on modification and... , Ph.D. (Chemistry)
- Full Text:
Processing strategies for nano-level dispersion of clay platelets in polypropylene matrices
- Authors: Morajane, Dimakatso
- Date: 2018
- Subjects: Nanocomposites (Materials) , Suspensions (Chemistry) , Polypropylene , Clay - Diffusion rate
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279630 , uj:30033
- Description: M.Tech. (Chemistry) , Abstract: Nanofillers and polymers are blended in an extruder using single pass or masterbatch (MB) dilution methods in order to address one of the major problems of dispersion with polymer nanocomposites. The mechanical properties of nanocomposites depend on the extent of homogeneous dispersion and distribution of nanoclays. This study used polypropylene (PP) as a model polymer owing to its unique toughness and modulus to investigate the melt processing strategies for preparing nanocomposites using a twin screw extruder (TSE). The TSE used has a screw diameter of 30 mm and L/D of 40 to produce nanocomposites with the following barrel temperatures: 120, 160, 180, 180, 180, 180, 180, 180, and 170 °C, respectively, while the die was set at 185 °C. PP nanocomposites were prepared through two main processes: MB dilution where MB with ~ 31 wt% inorganic nanoclay content was diluted further in PP to achieve 3 wt% inorganic nanoclay content in the nanocomposite; and direct preparation of composites through the single-pass method of compounding all the components that were mixed in an extruder at once. The extrudates were dried overnight at 80 °C to remove moisture from the samples. Dried extrudates were then injection moulded into test specimens for mechanical, rheological, and morphological tests using the Engel E-mac 50 injection moulder. The profile temperatures were set at 36, 220, 230, 235, 240 °C, respectively, and the mould was set at 17 °C. The effects of using different strategies on the dispersion of nanoclay platelets in the PP matrix were studied with transmission electron microscopy (TEM), X-ray diffraction (XRD), and small angle X-ray scattering (SAXS). TEM images show that the samples prepared via the MB...
- Full Text:
- Authors: Morajane, Dimakatso
- Date: 2018
- Subjects: Nanocomposites (Materials) , Suspensions (Chemistry) , Polypropylene , Clay - Diffusion rate
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/279630 , uj:30033
- Description: M.Tech. (Chemistry) , Abstract: Nanofillers and polymers are blended in an extruder using single pass or masterbatch (MB) dilution methods in order to address one of the major problems of dispersion with polymer nanocomposites. The mechanical properties of nanocomposites depend on the extent of homogeneous dispersion and distribution of nanoclays. This study used polypropylene (PP) as a model polymer owing to its unique toughness and modulus to investigate the melt processing strategies for preparing nanocomposites using a twin screw extruder (TSE). The TSE used has a screw diameter of 30 mm and L/D of 40 to produce nanocomposites with the following barrel temperatures: 120, 160, 180, 180, 180, 180, 180, 180, and 170 °C, respectively, while the die was set at 185 °C. PP nanocomposites were prepared through two main processes: MB dilution where MB with ~ 31 wt% inorganic nanoclay content was diluted further in PP to achieve 3 wt% inorganic nanoclay content in the nanocomposite; and direct preparation of composites through the single-pass method of compounding all the components that were mixed in an extruder at once. The extrudates were dried overnight at 80 °C to remove moisture from the samples. Dried extrudates were then injection moulded into test specimens for mechanical, rheological, and morphological tests using the Engel E-mac 50 injection moulder. The profile temperatures were set at 36, 220, 230, 235, 240 °C, respectively, and the mould was set at 17 °C. The effects of using different strategies on the dispersion of nanoclay platelets in the PP matrix were studied with transmission electron microscopy (TEM), X-ray diffraction (XRD), and small angle X-ray scattering (SAXS). TEM images show that the samples prepared via the MB...
- Full Text:
Study of secondary and ternary poly (vinyldenefluoride) nanocomposites : synthesis, characterization and application
- Authors: Bambo, Mokae Fanuel
- Date: 2018
- Subjects: Vinyl chloride polymers , Nanocomposites (Materials) , Scanning electron microscopes , X-ray microanalysis
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/261500 , uj:27573
- Description: Abstract: This work reports on the successful synthesis, characterisation and application of different forms such as sheets, nanofibers and thin films of polymer nanocomposites. The nanocomposites morphology and properties as a result of polymer concentration and organoclay loading are clearly demonstrated. Membrane sheets were successfully prepared using the phase inversion method. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) results showed morphology difference as the polymer concentration is varied. Lower concentration membranes shows a coarser surface since the polymer chains are freely arranged and the concentration of the solution is increased the entanglement becomes restricted and showed a more compact and even membrane surface at higher concentrations. The pristine Poly (vinyldene fluoride) (PVDF) membranes were found to contain more of the alphaphase crystallinity polymorph according to X-ray Diffraction (XRD) and Fourirer Transform Infrared Spectroscopy (FTIR) results. Addition of the organoclay into the polymer matrix resulted in transforming the alpha-phase polymorph into the betaphase crystalline polymorph. The surface morphology was also influenced by the incorporation of the organoclay. X-ray Photoelectron Spectroscopy (XPS) surface analysis also indicated the presence of the incorporated organoclays and copper nanoparticles in the nanocomposites. The Si and Cu peaks are seen emerging in the spectra as a result of their loading. The zeta potential results showed a change as the organoclay was added into the polymer, with the higher loading showing a higher potential as compared to the pristine PVDF at higher pH values as compared to low pH values. The influenced on polymer concentration on the electrospun nanofibers was observed through the change in morphology and diameter of the fiber. Lower concentration showed a wide fiber diameter distribution as the concentration was increased the change in diameter and morphology observed. Higher concentration showing an... , Ph.D. (Chemistry)
- Full Text:
- Authors: Bambo, Mokae Fanuel
- Date: 2018
- Subjects: Vinyl chloride polymers , Nanocomposites (Materials) , Scanning electron microscopes , X-ray microanalysis
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/261500 , uj:27573
- Description: Abstract: This work reports on the successful synthesis, characterisation and application of different forms such as sheets, nanofibers and thin films of polymer nanocomposites. The nanocomposites morphology and properties as a result of polymer concentration and organoclay loading are clearly demonstrated. Membrane sheets were successfully prepared using the phase inversion method. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) results showed morphology difference as the polymer concentration is varied. Lower concentration membranes shows a coarser surface since the polymer chains are freely arranged and the concentration of the solution is increased the entanglement becomes restricted and showed a more compact and even membrane surface at higher concentrations. The pristine Poly (vinyldene fluoride) (PVDF) membranes were found to contain more of the alphaphase crystallinity polymorph according to X-ray Diffraction (XRD) and Fourirer Transform Infrared Spectroscopy (FTIR) results. Addition of the organoclay into the polymer matrix resulted in transforming the alpha-phase polymorph into the betaphase crystalline polymorph. The surface morphology was also influenced by the incorporation of the organoclay. X-ray Photoelectron Spectroscopy (XPS) surface analysis also indicated the presence of the incorporated organoclays and copper nanoparticles in the nanocomposites. The Si and Cu peaks are seen emerging in the spectra as a result of their loading. The zeta potential results showed a change as the organoclay was added into the polymer, with the higher loading showing a higher potential as compared to the pristine PVDF at higher pH values as compared to low pH values. The influenced on polymer concentration on the electrospun nanofibers was observed through the change in morphology and diameter of the fiber. Lower concentration showed a wide fiber diameter distribution as the concentration was increased the change in diameter and morphology observed. Higher concentration showing an... , Ph.D. (Chemistry)
- Full Text:
The in-situ fabrication of high-performance metal-polymernanocomposites, within electro-catalysts, for the detection of dopamine and iodine respectively
- Authors: Brink, Raugmé
- Date: 2018
- Subjects: Nanocomposites (Materials) , Catalysts , Dopamine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/292769 , uj:31821
- Description: M.Sc. (Chemistry) , Abstract: Dopamine (DA) as a well-known neurotransmitters (NT), is a chemical messenger involved in the renal, hormonal, cardiovascular and central nervous system and enables neuronal communication. Dopamine forms part of some crucial metabolic and physiological processes within the body. Various diseases and disorders such as Parkinson’s Disease and Schizophrenia may stem from its imbalance [1, 2]. Certain analytes such as iodide, as an essential micronutrient, may also be indicative of the physiological health of a person. Its imbalance within the physiological system may either cause Goiter or act as a Goitrogen. It has been seen to affect 656 million people worldwide [1, 3]. The development of rapid and sensitive methods for the detection of these electroactive biomolecules and analytes, are important for both clinical and numerous non-clinical applications. The aim of the study was to synthesize metal enriched polymers as electro-catalysts for the efficient and sensitive detection of electroactive analytes. Electro-analytical chemistry has served as an alternative branch for the study of some physiological systems. These electrochemical sensors are attractive due to their high sensitivity, good controllability, rapid response rate and real-time detection [1]. Functional composite materials with unique physical and chemical properties have provided significant benefits for biological detection. Metallic nanoparticles contribute interesting qualities to materials, with respect to their unique electronic and electrocatalytic properties. It is dependent on their size and morphology. The detective potential, sensitivity and selectivity of Ag (0)-2ADPA and Cu(I)-PANI towards dopamine and iodide in an electrochemical based system was investigated during this study.
- Full Text:
- Authors: Brink, Raugmé
- Date: 2018
- Subjects: Nanocomposites (Materials) , Catalysts , Dopamine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/292769 , uj:31821
- Description: M.Sc. (Chemistry) , Abstract: Dopamine (DA) as a well-known neurotransmitters (NT), is a chemical messenger involved in the renal, hormonal, cardiovascular and central nervous system and enables neuronal communication. Dopamine forms part of some crucial metabolic and physiological processes within the body. Various diseases and disorders such as Parkinson’s Disease and Schizophrenia may stem from its imbalance [1, 2]. Certain analytes such as iodide, as an essential micronutrient, may also be indicative of the physiological health of a person. Its imbalance within the physiological system may either cause Goiter or act as a Goitrogen. It has been seen to affect 656 million people worldwide [1, 3]. The development of rapid and sensitive methods for the detection of these electroactive biomolecules and analytes, are important for both clinical and numerous non-clinical applications. The aim of the study was to synthesize metal enriched polymers as electro-catalysts for the efficient and sensitive detection of electroactive analytes. Electro-analytical chemistry has served as an alternative branch for the study of some physiological systems. These electrochemical sensors are attractive due to their high sensitivity, good controllability, rapid response rate and real-time detection [1]. Functional composite materials with unique physical and chemical properties have provided significant benefits for biological detection. Metallic nanoparticles contribute interesting qualities to materials, with respect to their unique electronic and electrocatalytic properties. It is dependent on their size and morphology. The detective potential, sensitivity and selectivity of Ag (0)-2ADPA and Cu(I)-PANI towards dopamine and iodide in an electrochemical based system was investigated during this study.
- Full Text: