The use of carbon nanotubes co-polymerized with calixarenes for the removal of cadmium and organic contaminants from water
- Authors: Makayonke, Nozuko Thelma
- Date: 2012-05-02
- Subjects: Water pollution , Nanotubes , Calixarenes , Organic water pollutants , Cadmium toxicology , Carbon , Nanostructured materials , Water purification , Organic compounds removal , Cadmium removal
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/${Handle} , uj:2231 , http://hdl.handle.net/10210/4671
- Description: M.Sc. , The contamination of water by toxic compounds is one of the most serious environmental problems today. These toxic compounds mostly originate from industrial effluents, agriculture runoff, natural sources (e.g. heavy metals in water from rocks and soil erosion) and human waste. The contamination, which is both “organic” and “inorganic” has an impact on the environment and human health. The demand for water and the pressure to re-use this valuable resource has increased the need for improved techniques and materials to remove pollutants from water. The Nanomaterials Science research group at the University of Johannesburg has focused on developing synthetic polymers that can be employed in water treatment and pollutant monitoring. Recently, cyclodextrins (CD) and carbon nanotubes (CNTs) have been included in polymers for this application. For example, CD-co-hexamethylene-/toluene-diisocyanate polyurethanes and CNT-modified equivalents have been developed and have been successfully applied in removing organic contaminants from water to very low levels.1 Calixarenes are synthetic analogues of cyclodextrins that can be exploited via chemical modification to express a range of properties. In the present study, calixarenes, thiacalixarenes and carbon nanotube-based polymeric materials incorporating these molecules have been synthesised, characterised and tested for removing both organic pollutants (such as p-nitrophenol) and inorganic pollutants (Cd2+, Pb2+) from water. Lead(II) and Cadmium(II) are a threat in South Africa because of their toxicity, and while p-nitrophenol is much less of a problem it represents a useful model organic pollutant. The absorption capacity of the polymers towards heavy metals and organic contaminants was tested by mixing the polymer with synthetic water containing known concentration of the contaminants at about 10 mg/L. Atomic absorption spectrometry (AAS) and ultraviolet-visible spectrometry (UV-vis) were used to determine the levels of heavy metals and organic contaminants, respectively. The target pollutants (Cd2+, 1 see KL Salipira MTech dissertation, University of Johannesburg 2008 Pb2+ and p-nitrophenol) were all successfully removed from water by the various polymers, however the degree of removal and loading capacities of the polymers differed. This information gives some insight into what functional components are needed for making successful adsorbents. It was observed, for example, that ptert- butylcalix[8]arene/hexamethylene diisocyanate (C8A/HMDI) had a higher adsorption capacity towards p-nitrophenol and Pb2+ than towards Cd2+, and also a higher capacity than the corresponding calix[4]arene polymers with smaller calixarene cavities.
- Full Text:
- Authors: Makayonke, Nozuko Thelma
- Date: 2012-05-02
- Subjects: Water pollution , Nanotubes , Calixarenes , Organic water pollutants , Cadmium toxicology , Carbon , Nanostructured materials , Water purification , Organic compounds removal , Cadmium removal
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/${Handle} , uj:2231 , http://hdl.handle.net/10210/4671
- Description: M.Sc. , The contamination of water by toxic compounds is one of the most serious environmental problems today. These toxic compounds mostly originate from industrial effluents, agriculture runoff, natural sources (e.g. heavy metals in water from rocks and soil erosion) and human waste. The contamination, which is both “organic” and “inorganic” has an impact on the environment and human health. The demand for water and the pressure to re-use this valuable resource has increased the need for improved techniques and materials to remove pollutants from water. The Nanomaterials Science research group at the University of Johannesburg has focused on developing synthetic polymers that can be employed in water treatment and pollutant monitoring. Recently, cyclodextrins (CD) and carbon nanotubes (CNTs) have been included in polymers for this application. For example, CD-co-hexamethylene-/toluene-diisocyanate polyurethanes and CNT-modified equivalents have been developed and have been successfully applied in removing organic contaminants from water to very low levels.1 Calixarenes are synthetic analogues of cyclodextrins that can be exploited via chemical modification to express a range of properties. In the present study, calixarenes, thiacalixarenes and carbon nanotube-based polymeric materials incorporating these molecules have been synthesised, characterised and tested for removing both organic pollutants (such as p-nitrophenol) and inorganic pollutants (Cd2+, Pb2+) from water. Lead(II) and Cadmium(II) are a threat in South Africa because of their toxicity, and while p-nitrophenol is much less of a problem it represents a useful model organic pollutant. The absorption capacity of the polymers towards heavy metals and organic contaminants was tested by mixing the polymer with synthetic water containing known concentration of the contaminants at about 10 mg/L. Atomic absorption spectrometry (AAS) and ultraviolet-visible spectrometry (UV-vis) were used to determine the levels of heavy metals and organic contaminants, respectively. The target pollutants (Cd2+, 1 see KL Salipira MTech dissertation, University of Johannesburg 2008 Pb2+ and p-nitrophenol) were all successfully removed from water by the various polymers, however the degree of removal and loading capacities of the polymers differed. This information gives some insight into what functional components are needed for making successful adsorbents. It was observed, for example, that ptert- butylcalix[8]arene/hexamethylene diisocyanate (C8A/HMDI) had a higher adsorption capacity towards p-nitrophenol and Pb2+ than towards Cd2+, and also a higher capacity than the corresponding calix[4]arene polymers with smaller calixarene cavities.
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Self-assembly of single walled carbon nanotube-poly amino benzene sulfonic acid on gold electrode for detection of mercury (II) and chromium (VI) in water
- Authors: Matlou, Gauto G.
- Date: 2016
- Subjects: Water - Purification - Chromium removal , Nanotubes , Chromium , Mercury
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84725 , uj:19257
- Description: Abstract: This work describes the design and integration of single-walled carbon nanotube-poly (amino benzene sulfonic acid) on gold electrode using Self-assembled monolayers (SAMS) technique. The integrated nanostructured films were confirmed using atomic force microscopy and field emission scanning electron microscopy. Further studies using voltammetry and impedance revealed the stability of the diffusion controlled reactions occurring on the integrated films on the electrode surface. The Au-DMAET-(SWCNT-PABS) electrode was found to have a greater electron transfer as compared to the bare Au and Au-DMAET electrode. All the SAMS on the electrode surface gave a pseudo capacitance behaviour on impedance spectroscopy. Au-DMAET-(SWCNT-PABS) electrode was able to detect Hg(II) and Cr(VI) in aqueous media under optimum conditions of 0.1 M HCl at pH 3, deposition time of 90 s and deposition potential of -0.1 V. Under these conditions, the sensor electrode achieved a detection limit of 0.06 μM with linearity between 20 nM and 250 nM was achieved for Hg(II). Cr(VI) stripping peak was found to be best prominent in 0.1 M KOH at pH 13 with deposition time of 30 s and deposition potential of -0.2 V. Under these conditions, the sensor electrode achieved a detection limit of 0.08 μM with linearity between 5 ppb and 50 ppb. For both analytes, the sensor electrode was found to be prone to interferences when tested against common heavy metals at two fold concentrations higher than that of the analytes. The method developed for each analyte together with the sensor electrode was able to detect comparable concentrations of mercury and chromium in two water samples with ICP-OES as a reference method. The t-test results of the two methods revealed random errors as associated to the results... , M.Sc. (Nanoscience)
- Full Text:
- Authors: Matlou, Gauto G.
- Date: 2016
- Subjects: Water - Purification - Chromium removal , Nanotubes , Chromium , Mercury
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84725 , uj:19257
- Description: Abstract: This work describes the design and integration of single-walled carbon nanotube-poly (amino benzene sulfonic acid) on gold electrode using Self-assembled monolayers (SAMS) technique. The integrated nanostructured films were confirmed using atomic force microscopy and field emission scanning electron microscopy. Further studies using voltammetry and impedance revealed the stability of the diffusion controlled reactions occurring on the integrated films on the electrode surface. The Au-DMAET-(SWCNT-PABS) electrode was found to have a greater electron transfer as compared to the bare Au and Au-DMAET electrode. All the SAMS on the electrode surface gave a pseudo capacitance behaviour on impedance spectroscopy. Au-DMAET-(SWCNT-PABS) electrode was able to detect Hg(II) and Cr(VI) in aqueous media under optimum conditions of 0.1 M HCl at pH 3, deposition time of 90 s and deposition potential of -0.1 V. Under these conditions, the sensor electrode achieved a detection limit of 0.06 μM with linearity between 20 nM and 250 nM was achieved for Hg(II). Cr(VI) stripping peak was found to be best prominent in 0.1 M KOH at pH 13 with deposition time of 30 s and deposition potential of -0.2 V. Under these conditions, the sensor electrode achieved a detection limit of 0.08 μM with linearity between 5 ppb and 50 ppb. For both analytes, the sensor electrode was found to be prone to interferences when tested against common heavy metals at two fold concentrations higher than that of the analytes. The method developed for each analyte together with the sensor electrode was able to detect comparable concentrations of mercury and chromium in two water samples with ICP-OES as a reference method. The t-test results of the two methods revealed random errors as associated to the results... , M.Sc. (Nanoscience)
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Application of metal impregnated carbon nanotubes and cyclodextrin polymers, for the destruction of bacteria in water
- Authors: Lukhele, Lungile Patricia
- Date: 2011-03-02T10:07:45Z
- Subjects: Water purification , Cyclodextrins , Polyurethanes , Nanotubes , Polymerization
- Type: Thesis
- Identifier: uj:7053 , http://hdl.handle.net/10210/3592
- Description: M.Sc. , Safe drinking water is an essential resource for human survival, health, dignity and development. However, this vital resource has become scarce mainly due to population growth, economic activity, climate change and pollution. Treatment of polluted water is expensive and does not always ensure delivery of safe drinking water to humans. Reports on the detection of pollutants such as organics, bacteria, inorganics and the occurrence of toxic disinfection byproducts in treated water in distribution systems have necessitated further research in improving water treatment methods. Metal impregnated carbon nanotube incorporated into cyclodextrin polyurethanes were synthesised by first functionalising carbon nanotubes and then impregnating them with metal nanoparticles. The resultant product was confirmed using Transmission electron microscopy (TEM). The metal nanoparticles were found to have a diameter range of 6 to 35 nm. The metal impregnated carbon nanotubes were then polymerised to produce cyclodextrin polyurethanes. The polymers were characterised using various techniques such as Scanning electron microscopy (SEM), Emission dispersive X-ray spectrometry (EDX) and Brunauer-Emmet-Teller analysis. The metal nanoparticles were found to be part of the polymers through EDX and the polymers’ surface areas were measured to be 0.78 and 0.3383 m2/g for silver and copper polymers, respectively. The synthesised polymers were tested for their efficacy at destroying pathogenic bacteria from water. The polymers were found to inactivate bacteria by up to 4 logs from spiked water samples. These metal impregnated polymers when compared to native carbon nanotubes and cyclodextrin polymers had an enhanced antibacterial property. In environmental samples, metal impregnated polymers destroyed up to 3 logs of bacteria. There was complete removal of bacteria from filtered environmental water samples. Factors affecting the polymers’ efficacy were turbidity, nature of sample and the ratio of bacterial cells removed per gram of polymer.
- Full Text:
- Authors: Lukhele, Lungile Patricia
- Date: 2011-03-02T10:07:45Z
- Subjects: Water purification , Cyclodextrins , Polyurethanes , Nanotubes , Polymerization
- Type: Thesis
- Identifier: uj:7053 , http://hdl.handle.net/10210/3592
- Description: M.Sc. , Safe drinking water is an essential resource for human survival, health, dignity and development. However, this vital resource has become scarce mainly due to population growth, economic activity, climate change and pollution. Treatment of polluted water is expensive and does not always ensure delivery of safe drinking water to humans. Reports on the detection of pollutants such as organics, bacteria, inorganics and the occurrence of toxic disinfection byproducts in treated water in distribution systems have necessitated further research in improving water treatment methods. Metal impregnated carbon nanotube incorporated into cyclodextrin polyurethanes were synthesised by first functionalising carbon nanotubes and then impregnating them with metal nanoparticles. The resultant product was confirmed using Transmission electron microscopy (TEM). The metal nanoparticles were found to have a diameter range of 6 to 35 nm. The metal impregnated carbon nanotubes were then polymerised to produce cyclodextrin polyurethanes. The polymers were characterised using various techniques such as Scanning electron microscopy (SEM), Emission dispersive X-ray spectrometry (EDX) and Brunauer-Emmet-Teller analysis. The metal nanoparticles were found to be part of the polymers through EDX and the polymers’ surface areas were measured to be 0.78 and 0.3383 m2/g for silver and copper polymers, respectively. The synthesised polymers were tested for their efficacy at destroying pathogenic bacteria from water. The polymers were found to inactivate bacteria by up to 4 logs from spiked water samples. These metal impregnated polymers when compared to native carbon nanotubes and cyclodextrin polymers had an enhanced antibacterial property. In environmental samples, metal impregnated polymers destroyed up to 3 logs of bacteria. There was complete removal of bacteria from filtered environmental water samples. Factors affecting the polymers’ efficacy were turbidity, nature of sample and the ratio of bacterial cells removed per gram of polymer.
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Polymerisation of cyclodextrins and multiwalled carbon nanotubes for use in water purification
- Authors: Salipira, Ketulo Lackson
- Date: 2008-06-24T13:18:46Z
- Subjects: Water purification , Organic water pollutants , Nanotubes
- Type: Thesis
- Identifier: uj:9836 , http://hdl.handle.net/10210/723
- Description: B.B. Mamba
- Full Text:
- Authors: Salipira, Ketulo Lackson
- Date: 2008-06-24T13:18:46Z
- Subjects: Water purification , Organic water pollutants , Nanotubes
- Type: Thesis
- Identifier: uj:9836 , http://hdl.handle.net/10210/723
- Description: B.B. Mamba
- Full Text:
Toxicity assessment of multiwalled carbon nanotubes and fullerenes to Pseudokirchneriella subcapitata, Daphnia magna and Poecilia reticulata in simulated fresh water systems
- Authors: Nyembe, Dumsile W.
- Date: 2016
- Subjects: Nanotechnology - Toxicity testing , Nanostructured materials , Nanotubes
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/124853 , uj:20966
- Description: Abstract: A huge variety of benefits are expected from the application of carbon based nanomaterials. Currently, the nanoproducts that can be found on the market can be classified as consumer products whereas future applications are presumed to encompass areas such as medicine, water purification and industrial applications. Nanomaterials are used mainly for their unique physicochemical properties which are known to improve products’ characteristics. Contrary to the physicochemical goodness, it is these very unique properties that have since raised health and the environmental concerns for. For the sustainability of this innovation and protection of the environment as well as human health, pro-active effort to understand and alleviate potential risks is vital. Current knowledge on nanoecotoxicology is clouded by uncertainties pertaining their fate and behaviour in the environment. With the increase in nanotechnology, carbon-based nanomaterials’ (CBN) have been earmarked for water purification. Their (CBN) behaviour in the aquatic environment, their biovailability in aquatic systems, interaction with and internalization by living organisms and their sub-lethal effects to aquatic organisms are key-determinates to their toxicity, yet they have only just began to emerge. The overarching aim of this thesis therefore was to address the existing gap in knowledge and further bring understanding of fate and behaviour of multi-walled carbon nanotubes (MWCNT) and fullerenes (C60) and their acute and sub-lethal toxicity to algae (Pseudokirchneriella subcapitata), daphnia (Daphnia magna) and fish (Poecilia reticulata) in simulated fresh water systems of varied salinity. The MWCNT and C60 were successfully synthesized using nebulized spray pyrolysis and chemical vapour deposition, respectively, as evidenced by characteristic peaks (D and G bands) identified using Raman spectroscopy. Acid oxidation of p-MWCNT and p-C60 yielded o-MWCNT and o-C60 respectively... , Ph.D. (Chemistry)
- Full Text:
- Authors: Nyembe, Dumsile W.
- Date: 2016
- Subjects: Nanotechnology - Toxicity testing , Nanostructured materials , Nanotubes
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/124853 , uj:20966
- Description: Abstract: A huge variety of benefits are expected from the application of carbon based nanomaterials. Currently, the nanoproducts that can be found on the market can be classified as consumer products whereas future applications are presumed to encompass areas such as medicine, water purification and industrial applications. Nanomaterials are used mainly for their unique physicochemical properties which are known to improve products’ characteristics. Contrary to the physicochemical goodness, it is these very unique properties that have since raised health and the environmental concerns for. For the sustainability of this innovation and protection of the environment as well as human health, pro-active effort to understand and alleviate potential risks is vital. Current knowledge on nanoecotoxicology is clouded by uncertainties pertaining their fate and behaviour in the environment. With the increase in nanotechnology, carbon-based nanomaterials’ (CBN) have been earmarked for water purification. Their (CBN) behaviour in the aquatic environment, their biovailability in aquatic systems, interaction with and internalization by living organisms and their sub-lethal effects to aquatic organisms are key-determinates to their toxicity, yet they have only just began to emerge. The overarching aim of this thesis therefore was to address the existing gap in knowledge and further bring understanding of fate and behaviour of multi-walled carbon nanotubes (MWCNT) and fullerenes (C60) and their acute and sub-lethal toxicity to algae (Pseudokirchneriella subcapitata), daphnia (Daphnia magna) and fish (Poecilia reticulata) in simulated fresh water systems of varied salinity. The MWCNT and C60 were successfully synthesized using nebulized spray pyrolysis and chemical vapour deposition, respectively, as evidenced by characteristic peaks (D and G bands) identified using Raman spectroscopy. Acid oxidation of p-MWCNT and p-C60 yielded o-MWCNT and o-C60 respectively... , Ph.D. (Chemistry)
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Towards the synthesis of doped carbon nanotube/polysulfone nanofiltration membranes for the removal of organic pollutants from water
- Authors: Yokwana, Kholiswa
- Date: 2014-06-26
- Subjects: Organic water pollutants , Carbon composites , Nanostructured materials , Nanotubes
- Type: Thesis
- Identifier: uj:11603 , http://hdl.handle.net/10210/11315
- Description: M.Tech. (Chemistry) , Please refer to full text to view abstract
- Full Text:
- Authors: Yokwana, Kholiswa
- Date: 2014-06-26
- Subjects: Organic water pollutants , Carbon composites , Nanostructured materials , Nanotubes
- Type: Thesis
- Identifier: uj:11603 , http://hdl.handle.net/10210/11315
- Description: M.Tech. (Chemistry) , Please refer to full text to view abstract
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Synthesis, characterization and properties of phosphorylated modified carbon nanotubes / polystyrene nanocomposites
- Authors: Ama, Monday Onoyivwe
- Date: 2013-07-24
- Subjects: Nanotubes , Nanocomposites (Materials) , Polystyrene , Phosphorylation
- Type: Thesis
- Identifier: uj:7676 , http://hdl.handle.net/10210/8543
- Description: M.Tech. (Chemical Technology) , Please refer to full text to view abstract
- Full Text:
- Authors: Ama, Monday Onoyivwe
- Date: 2013-07-24
- Subjects: Nanotubes , Nanocomposites (Materials) , Polystyrene , Phosphorylation
- Type: Thesis
- Identifier: uj:7676 , http://hdl.handle.net/10210/8543
- Description: M.Tech. (Chemical Technology) , Please refer to full text to view abstract
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Phosphine derivatized multiwalled carbon nanotubes for the removal of nickel and platinum from solutions
- Authors: Muleja, Adolph Anga
- Date: 2012-05-02
- Subjects: Nickel toxicology , Platinum toxicology , Carbon , Nanotubes , Nanostructured materials , Phosphine , Water - Purification - Nickel removal , Water - Purification - Platinum removal
- Type: Thesis
- Identifier: uj:2237 , http://hdl.handle.net/10210/4677
- Description: M.Tech. , Studies on the removal of nickel and platinum are increasing due to the toxicities of these metals. Several methods are currently used to extract these metals however they present limitations. There is hence a need to develop an efficient method for the removal of nickel and platinum from aqueous solution. A study on the use of purified multiwalled carbon nanotubes (purified MWCNTs) and a phosphine derivatized multiwalled carbon nanotubes for the extraction of these metal ions from solution was therefore undertaken. Multiwalled carbon nanotubes (MWCNTs) were produced by nebulised spray pyrolysis, purified by a multi-step technique and functionalized. Phosphine moieties were attached to the bromoarylated- MWCNTs by metallated phosphide route leading to triphenylphoshine linked MWCNTs (Tpp-MWCNTs). As produced, purified and triphenylphosphine linked multiwalled carbon nanotubes were characterized by various techniques, including microscopic and spectroscopic techniques, thermal, elemental and surface analysis. Transmission and scanning electron microscopy used revealed purified MWCNTs had insignificant impurities. X-ray photoelectron spectroscopy (XPS) results showed that triphenylphosphine linked multiwalled carbon nanotubes had 2.6% phosphorus. Zeta potential results demonstrated that purified MWCNTs had positive surface charges at acidic pH. Triphenylphosphine linked multiwalled carbon nanotubes were negatively charged on the surface in acidic media. Batch adsorption experiments were carried out to investigate the removal of nickel and platinum from aqueous solutions. Several parameters which influence the adsorption process were studied, including the effect of pH, the contact time and the effect of initial concentration on adsorption. The adsorption models for the Freundlich and Langmuir isotherms were employed to fit the experimental data. Triphenylphosphine linked MWCNTs removed more nickel (84.68 mg/g) than purified MWCNTs (77.39 mg/g). In contrast, purified MWCNTs removed more platinum (10.5 mg/g) than triphenylphosphine linked MWCNTs (6.01 mg/g). Experimental data for nickel fitted both Freundlich and Langmuir models well whereas only Langmuir model fitted well for platinum. The adsorption of nickel and platinum was indeed found to be pH, time and initial concentration dependent. Metal species (nickel and platinum) in solution had also influenced the uptake of these metals using purified-and Tpp-MWCNTs.
- Full Text:
- Authors: Muleja, Adolph Anga
- Date: 2012-05-02
- Subjects: Nickel toxicology , Platinum toxicology , Carbon , Nanotubes , Nanostructured materials , Phosphine , Water - Purification - Nickel removal , Water - Purification - Platinum removal
- Type: Thesis
- Identifier: uj:2237 , http://hdl.handle.net/10210/4677
- Description: M.Tech. , Studies on the removal of nickel and platinum are increasing due to the toxicities of these metals. Several methods are currently used to extract these metals however they present limitations. There is hence a need to develop an efficient method for the removal of nickel and platinum from aqueous solution. A study on the use of purified multiwalled carbon nanotubes (purified MWCNTs) and a phosphine derivatized multiwalled carbon nanotubes for the extraction of these metal ions from solution was therefore undertaken. Multiwalled carbon nanotubes (MWCNTs) were produced by nebulised spray pyrolysis, purified by a multi-step technique and functionalized. Phosphine moieties were attached to the bromoarylated- MWCNTs by metallated phosphide route leading to triphenylphoshine linked MWCNTs (Tpp-MWCNTs). As produced, purified and triphenylphosphine linked multiwalled carbon nanotubes were characterized by various techniques, including microscopic and spectroscopic techniques, thermal, elemental and surface analysis. Transmission and scanning electron microscopy used revealed purified MWCNTs had insignificant impurities. X-ray photoelectron spectroscopy (XPS) results showed that triphenylphosphine linked multiwalled carbon nanotubes had 2.6% phosphorus. Zeta potential results demonstrated that purified MWCNTs had positive surface charges at acidic pH. Triphenylphosphine linked multiwalled carbon nanotubes were negatively charged on the surface in acidic media. Batch adsorption experiments were carried out to investigate the removal of nickel and platinum from aqueous solutions. Several parameters which influence the adsorption process were studied, including the effect of pH, the contact time and the effect of initial concentration on adsorption. The adsorption models for the Freundlich and Langmuir isotherms were employed to fit the experimental data. Triphenylphosphine linked MWCNTs removed more nickel (84.68 mg/g) than purified MWCNTs (77.39 mg/g). In contrast, purified MWCNTs removed more platinum (10.5 mg/g) than triphenylphosphine linked MWCNTs (6.01 mg/g). Experimental data for nickel fitted both Freundlich and Langmuir models well whereas only Langmuir model fitted well for platinum. The adsorption of nickel and platinum was indeed found to be pH, time and initial concentration dependent. Metal species (nickel and platinum) in solution had also influenced the uptake of these metals using purified-and Tpp-MWCNTs.
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Synthesis, characterisation and application of ethylene diamine functionalised carbon nanoparticles for the removal of cadmium (II) and lead (II) from water
- Authors: Tshwenya, Luthando
- Date: 2017
- Subjects: Water - Purification , Cadmium , Nanostructured materials , Nanotubes , Carbon
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235777 , uj:24118
- Description: M.Tech. (Chemistry) , Abstract: This work explores the synthesis, characterisation and application of carbon nanoparticles derived from glucose (GCNPs) and functionalised with ethylene diamine (EDA), towards the removal of Cd(II) and Pb(II) in water samples. Glucose is a simple sugar that is readily available in nature, since it is organic, it can be easily converted to carbon through dehydration. GCNPs were successfully modified to form EDA-GCNPs and characterised by electron microscopy (TEM and SEM), CHNS elemental analysis, Brunauer–Emmett–Teller (BET), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis.Modification of GCNPs with EDA was confirmed from an increase in C-H stretch. Disappearance of carboxyl in the GCNPs and appearance of an amide linkage in the infrared spectra. Based on the particle size results obtained from TEM studies, it was also confirmed that indeed carbon nanoparticles were formed (as the particle sizes were in the nanorange). The adsorption behavior of the two materials for Cd(II) and Pb(II) was investigated by batch adsorption and the effect of several conditions such as contact time, pH, initial metal concentration and competing ions on cadmium and lead uptake were investigated. The adsorption results show that both adsorbents could effectively remove Cd2+ and Pb2+, with lead adsorption being more favoured as compared to that of cadmium. Equilibrium results best fitted the Langmuir model, and the maximum adsorption capacities for Pb(II) were found to be 15.15 and 28.99 mg g-1 for GCNPs and EDA-GCNPs, respectively, whilst Cd(II) adsorption resulted in lower sorption capacities (GCNPs = 10.31 mg g-1 and EDA-GCNPs=18.71 mg g-1). The adsorption processes were found to favour chemisorption, given that the pseudo-second-order kinetic model and Langmuir isotherms best fitted the adsorption results, implying that the functional groups present on the adsorbent surfaces are behind the uptake of these metal ions. The adsorbents showed applicability in real water samples and multi-elemental systems, with competing ions not affecting adsorption processes, moreover, regeneration studies show that both adsorbents are fully recyclable, indicating possible industrial applicability.
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- Authors: Tshwenya, Luthando
- Date: 2017
- Subjects: Water - Purification , Cadmium , Nanostructured materials , Nanotubes , Carbon
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235777 , uj:24118
- Description: M.Tech. (Chemistry) , Abstract: This work explores the synthesis, characterisation and application of carbon nanoparticles derived from glucose (GCNPs) and functionalised with ethylene diamine (EDA), towards the removal of Cd(II) and Pb(II) in water samples. Glucose is a simple sugar that is readily available in nature, since it is organic, it can be easily converted to carbon through dehydration. GCNPs were successfully modified to form EDA-GCNPs and characterised by electron microscopy (TEM and SEM), CHNS elemental analysis, Brunauer–Emmett–Teller (BET), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis.Modification of GCNPs with EDA was confirmed from an increase in C-H stretch. Disappearance of carboxyl in the GCNPs and appearance of an amide linkage in the infrared spectra. Based on the particle size results obtained from TEM studies, it was also confirmed that indeed carbon nanoparticles were formed (as the particle sizes were in the nanorange). The adsorption behavior of the two materials for Cd(II) and Pb(II) was investigated by batch adsorption and the effect of several conditions such as contact time, pH, initial metal concentration and competing ions on cadmium and lead uptake were investigated. The adsorption results show that both adsorbents could effectively remove Cd2+ and Pb2+, with lead adsorption being more favoured as compared to that of cadmium. Equilibrium results best fitted the Langmuir model, and the maximum adsorption capacities for Pb(II) were found to be 15.15 and 28.99 mg g-1 for GCNPs and EDA-GCNPs, respectively, whilst Cd(II) adsorption resulted in lower sorption capacities (GCNPs = 10.31 mg g-1 and EDA-GCNPs=18.71 mg g-1). The adsorption processes were found to favour chemisorption, given that the pseudo-second-order kinetic model and Langmuir isotherms best fitted the adsorption results, implying that the functional groups present on the adsorbent surfaces are behind the uptake of these metal ions. The adsorbents showed applicability in real water samples and multi-elemental systems, with competing ions not affecting adsorption processes, moreover, regeneration studies show that both adsorbents are fully recyclable, indicating possible industrial applicability.
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The synthesis, characterisation and application of phosphorylated multiwalled carbon nanotubes for the treatment of radioactive waste
- Authors: Mhlanga, Nikiwe
- Date: 2012-05-02
- Subjects: Radioactive wastes , Nanotubes , Carbon nanotubes , Phosphorylation
- Type: Thesis
- Identifier: uj:2234 , http://hdl.handle.net/10210/4674
- Description: M.Sc. , Radionuclides exist in the environment because of natural and human activities that are an essential part of our lives. Nuclear processing, medicinal applications (using isotopes) and electric power production by nuclear stations are few examples of human activities that result in production of radioactive waste (RAW). The nuclear power stations in our world have to store their waste in such a manner that the present and future generations are protected from harmful radiations and this is a challenge. Exposure to RAW can result in severe, diverse and irreversible consequences such as damage of the ecosystem, pollution, cancers, birth mutations, to mention just a few. Solvent extraction (SE) technique is currently used to purify large volumes of secondary liquid waste before they are released to the environment or stored. However, even after the SE purification, highly radioactive liquid waste is given off. This highly radioactive liquid waste is solidified in a glass matrix (vitrification). In an attempt to reduce the disposal of large volumes of secondary RAW generated during the purification technology, this study was initiated to investigate the possibility of using multiwalled carbon nanotubes (MWCNTs) as part of the SE technique. As the main nuclear liquid extraction processes involve tributyl phosphate (TBP), the MWCNTs were linked to TBP, polymerised to give a MWCNTs-TBP polymer that was tested in the nuclear environment. This polymer should possess good chelating properties due to the inclusion of the phosphate and should be a good absorbent as MWCNTs are promising absorbent carbon materials. To test the hypothesis of the study MWCNTs-TBP polymer was tested for uranium extraction. The MWCNTs-TBP polymer gave a zero Kd value which indicates that the adsorption capacity of the polymer to remove radionuclides from waste streams was not successful. The MWCNTs were then tested for iodine-131 extraction whereby they were compared with single walled carbon nanotubes (SWCNTs) and double walled carbon nanotubes (DWCNTs). In this test SWCNTs gave a Kd value of 81694 mL/g which proved that they can be used in nuclear waste applications.
- Full Text:
- Authors: Mhlanga, Nikiwe
- Date: 2012-05-02
- Subjects: Radioactive wastes , Nanotubes , Carbon nanotubes , Phosphorylation
- Type: Thesis
- Identifier: uj:2234 , http://hdl.handle.net/10210/4674
- Description: M.Sc. , Radionuclides exist in the environment because of natural and human activities that are an essential part of our lives. Nuclear processing, medicinal applications (using isotopes) and electric power production by nuclear stations are few examples of human activities that result in production of radioactive waste (RAW). The nuclear power stations in our world have to store their waste in such a manner that the present and future generations are protected from harmful radiations and this is a challenge. Exposure to RAW can result in severe, diverse and irreversible consequences such as damage of the ecosystem, pollution, cancers, birth mutations, to mention just a few. Solvent extraction (SE) technique is currently used to purify large volumes of secondary liquid waste before they are released to the environment or stored. However, even after the SE purification, highly radioactive liquid waste is given off. This highly radioactive liquid waste is solidified in a glass matrix (vitrification). In an attempt to reduce the disposal of large volumes of secondary RAW generated during the purification technology, this study was initiated to investigate the possibility of using multiwalled carbon nanotubes (MWCNTs) as part of the SE technique. As the main nuclear liquid extraction processes involve tributyl phosphate (TBP), the MWCNTs were linked to TBP, polymerised to give a MWCNTs-TBP polymer that was tested in the nuclear environment. This polymer should possess good chelating properties due to the inclusion of the phosphate and should be a good absorbent as MWCNTs are promising absorbent carbon materials. To test the hypothesis of the study MWCNTs-TBP polymer was tested for uranium extraction. The MWCNTs-TBP polymer gave a zero Kd value which indicates that the adsorption capacity of the polymer to remove radionuclides from waste streams was not successful. The MWCNTs were then tested for iodine-131 extraction whereby they were compared with single walled carbon nanotubes (SWCNTs) and double walled carbon nanotubes (DWCNTs). In this test SWCNTs gave a Kd value of 81694 mL/g which proved that they can be used in nuclear waste applications.
- Full Text:
Synthesis and characterization of copper-containing carbon nanotubes (CNTs) and their use in the removal of pollutants in water
- Authors: Nhlabatsi, Zanele Precious
- Date: 2012-06-07
- Subjects: Copper , Carbon , Nanotubes , Water purification , Escherichia coli removal , Mercury removal
- Type: Thesis
- Identifier: uj:8686 , http://hdl.handle.net/10210/5040
- Description: M.Sc. , Improper disposal of industrial effluents that contain heavy metals such as mercury causes a threat to the environment due to the toxic effects of such matal even at low concentrations. It is also known that sewage waste in water contains bacteria that pose a health hazard to human beings, animals and micro-organisms. One major concern is the transmission of diseases through drinking this water; which destabilizes the water supply. Water for human consumption therefore needs to be of high quality. In this study copper-containing multiwalled carbon nanotubes (Cu/MWCNTs) were investigated for their ability to remove and kill mercury (Hg2+) and Escherichia coli (E. coli), a major species found in the coliform bacteria. These Cu/MWCNTs were synthesized “in situ” by using an electric arc-discharge apparatus and separately via one of two multi-step wet chemical techniques namely; an electroless plating and impregnation method respectively. MWCNTs used for the wet techniques were synthesized by a nebulized spray pyrolysis (NSP) process using ferrocene/toluene under argon flow. These MWCNTs were purified and functionalized to introduce functional groups that made provision for the nucleation of the copper metal on the surface of MWCNTs. Infrared spectroscopy confirmed the successful introduction of COOH and O-H groups on the surface of MWCNTs. Raman spectroscopy confirmed a relative increase in the intensity the ratio of the D-band after functionalization. Deposition of the copper nanoparticles by electroless plating method in different volumes of 100 ml, 80 ml and 60 ml produced copper nanoparticles of varying sizes and distribution on the surface of MWCNTs. SEM images revealed densely and homogeneously distributed small sized copper nanoparticles that followed the trend; 100 ml> 80 ml > 60 ml. The volume proved to be a critical factor of the electroless plating bath with an increase or decrease of the volume affecting the concentration of the Cu2+ ions and HCHO, which also affected the pH of the plating solution.
- Full Text:
- Authors: Nhlabatsi, Zanele Precious
- Date: 2012-06-07
- Subjects: Copper , Carbon , Nanotubes , Water purification , Escherichia coli removal , Mercury removal
- Type: Thesis
- Identifier: uj:8686 , http://hdl.handle.net/10210/5040
- Description: M.Sc. , Improper disposal of industrial effluents that contain heavy metals such as mercury causes a threat to the environment due to the toxic effects of such matal even at low concentrations. It is also known that sewage waste in water contains bacteria that pose a health hazard to human beings, animals and micro-organisms. One major concern is the transmission of diseases through drinking this water; which destabilizes the water supply. Water for human consumption therefore needs to be of high quality. In this study copper-containing multiwalled carbon nanotubes (Cu/MWCNTs) were investigated for their ability to remove and kill mercury (Hg2+) and Escherichia coli (E. coli), a major species found in the coliform bacteria. These Cu/MWCNTs were synthesized “in situ” by using an electric arc-discharge apparatus and separately via one of two multi-step wet chemical techniques namely; an electroless plating and impregnation method respectively. MWCNTs used for the wet techniques were synthesized by a nebulized spray pyrolysis (NSP) process using ferrocene/toluene under argon flow. These MWCNTs were purified and functionalized to introduce functional groups that made provision for the nucleation of the copper metal on the surface of MWCNTs. Infrared spectroscopy confirmed the successful introduction of COOH and O-H groups on the surface of MWCNTs. Raman spectroscopy confirmed a relative increase in the intensity the ratio of the D-band after functionalization. Deposition of the copper nanoparticles by electroless plating method in different volumes of 100 ml, 80 ml and 60 ml produced copper nanoparticles of varying sizes and distribution on the surface of MWCNTs. SEM images revealed densely and homogeneously distributed small sized copper nanoparticles that followed the trend; 100 ml> 80 ml > 60 ml. The volume proved to be a critical factor of the electroless plating bath with an increase or decrease of the volume affecting the concentration of the Cu2+ ions and HCHO, which also affected the pH of the plating solution.
- Full Text:
The synthesis of phosphorylated multiwalled carbon nanotubes and their use in the removal of Mercury(ll) and Chromium(Vl) ions from aqueous solution
- Authors: Velempini, Tarisai Phillipa
- Date: 2014-06-30
- Subjects: Carbon , Nanotubes , Nanostructured materials , Mercury , Water - Purification - Chromium removal
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/391557 , uj:11617 , http://hdl.handle.net/10210/11330
- Description: M.Sc. (Chemistry) , Please refer to full text to view abstract
- Full Text:
- Authors: Velempini, Tarisai Phillipa
- Date: 2014-06-30
- Subjects: Carbon , Nanotubes , Nanostructured materials , Mercury , Water - Purification - Chromium removal
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/391557 , uj:11617 , http://hdl.handle.net/10210/11330
- Description: M.Sc. (Chemistry) , Please refer to full text to view abstract
- Full Text:
Alginate beads supporting nanocomposites incorporating cyclodextrin polymers and fe/ni decorated carbon nanotubes for the removal of 2,4,6-trichlorophenol in water
- Authors: Kera, Nazia Hassan
- Date: 2013-12-09
- Subjects: Water - Purification - Organic compounds removal , Nanocomposites (Materials) , Nanotubes , Cyclodextrins , Polymers
- Type: Thesis
- Identifier: uj:7841 , http://hdl.handle.net/10210/8736
- Description: M.Sc. (Chemistry) , The quality of fresh water is deteriorating due to pollution by a wide range of substances as a result of industrial, agricultural, domestic, mining and other anthropogenic activities. Even at trace levels in water, some pollutants are toxic to organisms through acute or chronic effects or through bioaccumulation. Conventional water treatment is often ineffective at removing pollutants to the ultra-low levels required by water quality standards and other technologies employed to remove toxic compounds from water have high capital and operating costs and other disadvantages. There is therefore an ongoing need to develop low-cost technologies that are effective for the removal of toxic pollutants from water. In our laboratories, iron and nickel (Fe/Ni) decorated carbon nanotube (CNT)/cyclodextrin polymers (β-CDs) showed promising results in previous studies carried out for the degradation and removal of toxic organic pollutants in water. However, the powder form of the polymer makes its direct application in water treatment difficult. The leaching of metal nanoparticles and carbon nanotubes from the polymer into the water being treated is also of concern due to their potential toxicity. In this study, alginate beads were investigated as supports for two kinds of nanocomposites, Fe/Ni decorated carbon nanotubes and Fe/Ni decorated carbon nanotube/cyclodextrin polymers. Alginate beads were selected as supports to render the nanocomposites more conducive towards water treatment applications since they are easy to handle and recover from water and are also stable supports that can prevent the leaching of nanomaterials into treated water.
- Full Text:
- Authors: Kera, Nazia Hassan
- Date: 2013-12-09
- Subjects: Water - Purification - Organic compounds removal , Nanocomposites (Materials) , Nanotubes , Cyclodextrins , Polymers
- Type: Thesis
- Identifier: uj:7841 , http://hdl.handle.net/10210/8736
- Description: M.Sc. (Chemistry) , The quality of fresh water is deteriorating due to pollution by a wide range of substances as a result of industrial, agricultural, domestic, mining and other anthropogenic activities. Even at trace levels in water, some pollutants are toxic to organisms through acute or chronic effects or through bioaccumulation. Conventional water treatment is often ineffective at removing pollutants to the ultra-low levels required by water quality standards and other technologies employed to remove toxic compounds from water have high capital and operating costs and other disadvantages. There is therefore an ongoing need to develop low-cost technologies that are effective for the removal of toxic pollutants from water. In our laboratories, iron and nickel (Fe/Ni) decorated carbon nanotube (CNT)/cyclodextrin polymers (β-CDs) showed promising results in previous studies carried out for the degradation and removal of toxic organic pollutants in water. However, the powder form of the polymer makes its direct application in water treatment difficult. The leaching of metal nanoparticles and carbon nanotubes from the polymer into the water being treated is also of concern due to their potential toxicity. In this study, alginate beads were investigated as supports for two kinds of nanocomposites, Fe/Ni decorated carbon nanotubes and Fe/Ni decorated carbon nanotube/cyclodextrin polymers. Alginate beads were selected as supports to render the nanocomposites more conducive towards water treatment applications since they are easy to handle and recover from water and are also stable supports that can prevent the leaching of nanomaterials into treated water.
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Synthesis and properties of carbon nanotubes coated tin dioxide for gas sensing applications
- Authors: Motshekga, Sarah Constance
- Date: 2012-07-31
- Subjects: Carbon , Nanotubes , Nanostructured materials
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/389004 , uj:8885 , http://hdl.handle.net/10210/5356
- Description: M.Tech. , Among the materials being used for gas sensors, metal oxides are the most important materials because of their potential to detect many gases at low concentrations. Nevertheless, sensors made of metal oxide need to be operated at high temperatures (above 200°C) and have a weak sel ectivity. In order to overcome this difficulty, the materials are being investigated for gas sensing applications. Carbon nanotubes (CNTs) are promising materials with unique properties, such as high electrical conductivity, mechanical strength, nanometer–scale sizes, and high aspect ratio. Their adsorption ability and high surface area make them attractive as gas sensing materials, which have been intensively studied. CNTs can be used solely or combined with metals and oxides materials in order to constitute efficient gas sensors. In the present research, multi–walled CNTs (MWCNTs) were coated with tin dioxide (SnO2) and incorporated into two epoxy resins with widely different mechanical properties in order to study the effect of CNTs on the morphology, mechanical, electrical, and sensing properties of the composites. In the MWCNT/polymer composite study, Epon 828 was used as the polymer matrix and D–2000 (which gives rubbery composites) and T–403 (which gives glassy composites) as the hardeners. Composite were prepared with 0.1 wt.% MWCNTs in an epoxy matrix. Pristine MWCNTs (MWCNTs not treated with any acid and therefore used as received) and SnO2–MWCNTs were used for comparison and a two–step curing procedure was used with initial temperature set at 75°C for 3 hours, followed by additional 3 hours at 125°C. The sample s were characterized for morphology, mechanical, thermo–mechanical and electrical properties using scanning electron microscopy (SEM), an Instron tensile tester, dynamic mechanical analysis (DMA) and Cascade Microtech four–point probe, respectively. In both cases, strong covalent bonds were created as a bridge between the CNTs and matrix, but due to differences in viscosity, the nanotubes dispersion was much better in the rubbery epoxy resin than in the glassy epoxy resin. A 77% increase in tensile modulus was observed in the rubbery system using 0.1 wt.% SnO2–MWCNTs compared to the neat rubbery epoxy. As for the glassy epoxy based composite, only a 3% improvement in tensile modulus could be observed. In addition to the mechanical properties, the presence of CNTs has demonstrated a material with high vi electrical conductivity. But for the surface measurements during the gas sensing analysis, the conductivity was very low for the composites to be used for this application as envisioned. MWCNTs coated with SnO2 nanoparticles used in the present study, were synthesized by a microwave synthesis method. The composite samples were characterized by X–ray diffraction (XRD), Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmet–Teller (BET) surface area analysis. These techniques gave evidence for surface and chemical modifications of the synthesized composites. The results showed microwave synthesis to be a very efficient method in producing CNTs that are densely coated and well dispersed with SnO2 nanoparticles in a very short time (total reaction time of 10 minutes). Microwave synthesis is particularly interesting because of the energy used, the higher temperature homogeneity and the shorter reaction times led to nanoparticles with high crystallinity and a narrow particle size distribution. Controlling the morphology by varying synthesis conditions such as temperature, pressure and time is also possible.
- Full Text:
- Authors: Motshekga, Sarah Constance
- Date: 2012-07-31
- Subjects: Carbon , Nanotubes , Nanostructured materials
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/389004 , uj:8885 , http://hdl.handle.net/10210/5356
- Description: M.Tech. , Among the materials being used for gas sensors, metal oxides are the most important materials because of their potential to detect many gases at low concentrations. Nevertheless, sensors made of metal oxide need to be operated at high temperatures (above 200°C) and have a weak sel ectivity. In order to overcome this difficulty, the materials are being investigated for gas sensing applications. Carbon nanotubes (CNTs) are promising materials with unique properties, such as high electrical conductivity, mechanical strength, nanometer–scale sizes, and high aspect ratio. Their adsorption ability and high surface area make them attractive as gas sensing materials, which have been intensively studied. CNTs can be used solely or combined with metals and oxides materials in order to constitute efficient gas sensors. In the present research, multi–walled CNTs (MWCNTs) were coated with tin dioxide (SnO2) and incorporated into two epoxy resins with widely different mechanical properties in order to study the effect of CNTs on the morphology, mechanical, electrical, and sensing properties of the composites. In the MWCNT/polymer composite study, Epon 828 was used as the polymer matrix and D–2000 (which gives rubbery composites) and T–403 (which gives glassy composites) as the hardeners. Composite were prepared with 0.1 wt.% MWCNTs in an epoxy matrix. Pristine MWCNTs (MWCNTs not treated with any acid and therefore used as received) and SnO2–MWCNTs were used for comparison and a two–step curing procedure was used with initial temperature set at 75°C for 3 hours, followed by additional 3 hours at 125°C. The sample s were characterized for morphology, mechanical, thermo–mechanical and electrical properties using scanning electron microscopy (SEM), an Instron tensile tester, dynamic mechanical analysis (DMA) and Cascade Microtech four–point probe, respectively. In both cases, strong covalent bonds were created as a bridge between the CNTs and matrix, but due to differences in viscosity, the nanotubes dispersion was much better in the rubbery epoxy resin than in the glassy epoxy resin. A 77% increase in tensile modulus was observed in the rubbery system using 0.1 wt.% SnO2–MWCNTs compared to the neat rubbery epoxy. As for the glassy epoxy based composite, only a 3% improvement in tensile modulus could be observed. In addition to the mechanical properties, the presence of CNTs has demonstrated a material with high vi electrical conductivity. But for the surface measurements during the gas sensing analysis, the conductivity was very low for the composites to be used for this application as envisioned. MWCNTs coated with SnO2 nanoparticles used in the present study, were synthesized by a microwave synthesis method. The composite samples were characterized by X–ray diffraction (XRD), Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmet–Teller (BET) surface area analysis. These techniques gave evidence for surface and chemical modifications of the synthesized composites. The results showed microwave synthesis to be a very efficient method in producing CNTs that are densely coated and well dispersed with SnO2 nanoparticles in a very short time (total reaction time of 10 minutes). Microwave synthesis is particularly interesting because of the energy used, the higher temperature homogeneity and the shorter reaction times led to nanoparticles with high crystallinity and a narrow particle size distribution. Controlling the morphology by varying synthesis conditions such as temperature, pressure and time is also possible.
- Full Text:
Photocatalytic performance of nitrogen-platinum group metal co-doped Tio2 supported on carbon nanotubes for visible-light degradation of organic pollutants in water
- Authors: Kuvarega, Alex Tawanda
- Date: 2013-07-24
- Subjects: Water purification , Water purification - Organic compounds removal , Organic water pollutants , Titanium dioxide , Photocatalysis , Nanotubes , Carbon
- Type: Thesis
- Identifier: uj:7665 , http://hdl.handle.net/10210/8533
- Description: D.Phil. (Chemistry) , Elimination of toxic organic compounds from wastewater is currently one of the most important subjects in water-pollution control. Among the many organic pollutants are dyes and emerging pollutants such as natural organic matter (NOM). Dyes such as Eosin Yellow (EY), an anionic xanthene fluorescent dye, can originate from many sources such as textile industrial processes, paper pulp industries and agricultural processes. Most dyes are problematic because they are resistant to conventional chemical or biological water-treatment methods and therefore persist in the environment. NOM consists of a highly variable mixture of products found in water and soils. NOM is formed as a result of the decomposition of plant and animal material and is a precursor to the formation of disinfection by-products (DBP) during water disinfection. These organic compounds cause undesirable colour, taste and odour in water. NOM affects the capacity of other treatment processes to effectively remove organic micro-pollutants or inorganic species that may be present in the water. Its removal also uses up chemicals and energy and so it is expensive to treat. Titanium dioxide (TiO2) has emerged as one of the most fascinating materials in the modern era due to its semiconducting and catalytic properties. TiO2 is a large band-gap semiconductor that exists mainly in the anatase (band gap 3.2 eV) and rutile (band gap 3.0 eV) phases. Its response to UV light has led to increased interest in its application in the photocatalysis research field. It has been investigated extensively for its super hydrophilicity and use in environmental remediation and solar fuel production. In spite of extensive efforts to apply TiO2 for environmental remediation, photocatalytic activity in the visible region has remained quite low hence the ultimate goal of this research was to fabricate highly photoactive catalysts composed of non-metal, platinum-group metal (PGM) co-doped TiO2 and carbon nanotubes (CNTs) and to apply them for water purification using solar radiation...
- Full Text:
- Authors: Kuvarega, Alex Tawanda
- Date: 2013-07-24
- Subjects: Water purification , Water purification - Organic compounds removal , Organic water pollutants , Titanium dioxide , Photocatalysis , Nanotubes , Carbon
- Type: Thesis
- Identifier: uj:7665 , http://hdl.handle.net/10210/8533
- Description: D.Phil. (Chemistry) , Elimination of toxic organic compounds from wastewater is currently one of the most important subjects in water-pollution control. Among the many organic pollutants are dyes and emerging pollutants such as natural organic matter (NOM). Dyes such as Eosin Yellow (EY), an anionic xanthene fluorescent dye, can originate from many sources such as textile industrial processes, paper pulp industries and agricultural processes. Most dyes are problematic because they are resistant to conventional chemical or biological water-treatment methods and therefore persist in the environment. NOM consists of a highly variable mixture of products found in water and soils. NOM is formed as a result of the decomposition of plant and animal material and is a precursor to the formation of disinfection by-products (DBP) during water disinfection. These organic compounds cause undesirable colour, taste and odour in water. NOM affects the capacity of other treatment processes to effectively remove organic micro-pollutants or inorganic species that may be present in the water. Its removal also uses up chemicals and energy and so it is expensive to treat. Titanium dioxide (TiO2) has emerged as one of the most fascinating materials in the modern era due to its semiconducting and catalytic properties. TiO2 is a large band-gap semiconductor that exists mainly in the anatase (band gap 3.2 eV) and rutile (band gap 3.0 eV) phases. Its response to UV light has led to increased interest in its application in the photocatalysis research field. It has been investigated extensively for its super hydrophilicity and use in environmental remediation and solar fuel production. In spite of extensive efforts to apply TiO2 for environmental remediation, photocatalytic activity in the visible region has remained quite low hence the ultimate goal of this research was to fabricate highly photoactive catalysts composed of non-metal, platinum-group metal (PGM) co-doped TiO2 and carbon nanotubes (CNTs) and to apply them for water purification using solar radiation...
- Full Text:
Voltammetric and impedance studies of phenols and Its derivatives at carbon nanotubes/Prussian bluefilms platinum modified electrode
- Adekunle, Abolanle S., Arotiba, Omotayo A., Agboola, Bolade O., Maxakato, Nobanathi W., Mamba, Bhekie B.
- Authors: Adekunle, Abolanle S. , Arotiba, Omotayo A. , Agboola, Bolade O. , Maxakato, Nobanathi W. , Mamba, Bhekie B.
- Date: 2012
- Subjects: Phenols , Platinum electrode , Prussian blue nanoparticles , Nanotubes , Nanocomposites (Materials)
- Type: Article
- Identifier: uj:5996 , ISSN 1452-3981 , http://hdl.handle.net/10210/8629
- Description: The electrochemical oxidation of phenol (Ph), 4-chlorophenol (4-ClPh) and 4-nitrophenol (4-NPh) at a platinum electrode modified with and without multi-walled carbon nanotubes/Prussian blue nanocomposite in a pH 7.0 phosphate buffer electrolyte was investigated by cyclic voltammetry (CV) and impedance measurements. The modified electrodes were characterised using techniques such as transmission electron microscopy (TEM), electron X-ray dispersive spectroscopy (XRD), cyclic voltammetry (CVs) and electrochemical impedance spectroscopy (EIS)...
- Full Text:
- Authors: Adekunle, Abolanle S. , Arotiba, Omotayo A. , Agboola, Bolade O. , Maxakato, Nobanathi W. , Mamba, Bhekie B.
- Date: 2012
- Subjects: Phenols , Platinum electrode , Prussian blue nanoparticles , Nanotubes , Nanocomposites (Materials)
- Type: Article
- Identifier: uj:5996 , ISSN 1452-3981 , http://hdl.handle.net/10210/8629
- Description: The electrochemical oxidation of phenol (Ph), 4-chlorophenol (4-ClPh) and 4-nitrophenol (4-NPh) at a platinum electrode modified with and without multi-walled carbon nanotubes/Prussian blue nanocomposite in a pH 7.0 phosphate buffer electrolyte was investigated by cyclic voltammetry (CV) and impedance measurements. The modified electrodes were characterised using techniques such as transmission electron microscopy (TEM), electron X-ray dispersive spectroscopy (XRD), cyclic voltammetry (CVs) and electrochemical impedance spectroscopy (EIS)...
- Full Text:
Carbon nanotubes and nanospheres: synthesis by nebulised spray pyrolysis and use in catalysis
- Authors: Cele, Leskey Mduduzi
- Date: 2009-05-13T08:47:51Z
- Subjects: Carbon , Nanotubes , Nanostructured materials , Pyrolysis , Organic compounds synthesis , Palladium catalysts , Hydrogenation , Ethylene
- Type: Thesis
- Identifier: uj:8370 , http://hdl.handle.net/10210/2536
- Description: Ph.D. , This work presents a detailed study of the synthesis of carbon nanotubes and nanospheres by nebulised spray pyrolysis. This method has been used by other workers mainly for preparation of sub-micron particles and the deposition of thin films on various substrates. The effect of various synthesis parameters including the temperature, choice of the carbon source and the metal precursor as well as the carrier gas flow rate on the selectivity of the reaction and the properties of the carbon nanotubes produced was investigated. A major part of this work was devoted to a study of the effects of the addition of small quantities of oxygencontaining compounds (alcohols, esters and aldehydes) to the reaction mixture. The products were analysed using various methods including TEM, SEM, Laser- Raman spectroscopy and HRTEM. Furthermore, the possible use of carbon nanotubes and carbon nanospheres as supports for palladium in the hydrogenation of ethylene was investigated. Nebulised spray pyrolysis proved to be a suitable technique for the synthesis of well graphitized carbon nanotubes and carbon nanospheres with uniform diameters and it was demonstrated that good control of the carbon nanotube properties could be achieved by controlling the synthesis parameters. Better graphitization of the carbon nanotubes was observed at higher temperatures. Ferrocene, iron pentacarbonyl, nickelocene and cobaltocene were successfully used in carbon nanotube synthesis with the last two producing carbon nanotubes with diameters close to those on single-walled carbon nanotubes. Toluene (with and without acetylene as a supplementary carbon source), benzene, mesitylene, xylene and nhexane were successfully used to produce carbon nanotubes with a high degree of alignment while no success was achieved with ethanol. The poor yields obtained with ethanol appear to be a consequence of chemical changes in the ethanol induced by exposure to ultrasound irradiation. On the other hand, low concentrations of methyl acetate and ethyl acetate appear to enhance the production of carbon nanotubes. It was demonstrated that carbon nanotubes and nanospheres are suitable for use as supports for palladium in the hydrogenation of ethylene. Pd particles of uniform size were obtained and the conversion rates were slightly higher when the carbon nanotubes were pre-treated with a mixture of sulphuric acid and nitric acid.
- Full Text:
- Authors: Cele, Leskey Mduduzi
- Date: 2009-05-13T08:47:51Z
- Subjects: Carbon , Nanotubes , Nanostructured materials , Pyrolysis , Organic compounds synthesis , Palladium catalysts , Hydrogenation , Ethylene
- Type: Thesis
- Identifier: uj:8370 , http://hdl.handle.net/10210/2536
- Description: Ph.D. , This work presents a detailed study of the synthesis of carbon nanotubes and nanospheres by nebulised spray pyrolysis. This method has been used by other workers mainly for preparation of sub-micron particles and the deposition of thin films on various substrates. The effect of various synthesis parameters including the temperature, choice of the carbon source and the metal precursor as well as the carrier gas flow rate on the selectivity of the reaction and the properties of the carbon nanotubes produced was investigated. A major part of this work was devoted to a study of the effects of the addition of small quantities of oxygencontaining compounds (alcohols, esters and aldehydes) to the reaction mixture. The products were analysed using various methods including TEM, SEM, Laser- Raman spectroscopy and HRTEM. Furthermore, the possible use of carbon nanotubes and carbon nanospheres as supports for palladium in the hydrogenation of ethylene was investigated. Nebulised spray pyrolysis proved to be a suitable technique for the synthesis of well graphitized carbon nanotubes and carbon nanospheres with uniform diameters and it was demonstrated that good control of the carbon nanotube properties could be achieved by controlling the synthesis parameters. Better graphitization of the carbon nanotubes was observed at higher temperatures. Ferrocene, iron pentacarbonyl, nickelocene and cobaltocene were successfully used in carbon nanotube synthesis with the last two producing carbon nanotubes with diameters close to those on single-walled carbon nanotubes. Toluene (with and without acetylene as a supplementary carbon source), benzene, mesitylene, xylene and nhexane were successfully used to produce carbon nanotubes with a high degree of alignment while no success was achieved with ethanol. The poor yields obtained with ethanol appear to be a consequence of chemical changes in the ethanol induced by exposure to ultrasound irradiation. On the other hand, low concentrations of methyl acetate and ethyl acetate appear to enhance the production of carbon nanotubes. It was demonstrated that carbon nanotubes and nanospheres are suitable for use as supports for palladium in the hydrogenation of ethylene. Pd particles of uniform size were obtained and the conversion rates were slightly higher when the carbon nanotubes were pre-treated with a mixture of sulphuric acid and nitric acid.
- Full Text:
Synthesis, characterization and properties of novel phosphorylated multiwalled carbon nanotubes/polyvinyl chloride nanocomposites
- Authors: Mkhabela, Vuyiswa J.
- Date: 2011-09-13T09:20:26Z
- Subjects: Nanotubes , Carbon nanotubes , Phosphorylation , Nanocomposites (Materials) , Carbon , Vinyl chloride polymers
- Type: Thesis
- Identifier: uj:7198 , http://hdl.handle.net/10210/3833
- Description: M.Sc. , Carbon nanotubes (CNTs) have been of utmost scientific interest since their discovery in 1991 by a Japanese physicist - Sumio Iijima. This is due to their extraordinary properties which make them one of the most promising options for the design of novel ultrahigh strength polymer nanocomposites. It is believed that the high aspect ratio, mechanical strength, and high electrical and thermal conductivity of these CNTs will enhance the performance of many polymer / CNT nanocomposites and open up new applications. However, poor dispersibility and lack of interfacial adhesion of the CNTs in the polymer matrix have remained a challenge towards fabrication of these nanocomposites. This has been due to the atomically smooth surface of the nanotubes and their intrinsic van der Waals forces which make them chemically inert. This study was aimed at exploring this concept by using novel phosphorylated multiwalled carbon nanotubes (p-MWCNTs) and polyvinyl chloride (PVC) polymer. Phosphorylation of MWCNTs has been successfully achieved in our laboratories, with the p-MWCNTs showing improvement in thermal stability. PVC on the other hand, is the world’s second largest thermoplastic material and has physical properties that are key technical advantages for its use in various and diverse fields such as building and construction, electronics, food packaging and in medical applications. A novel solvent-free method was used to synthesize p-MWCNTs / PVC nanocomposites. MWCNTs were synthesized by nebulized spray pyrolysis, a modification of catalytic vapour deposition and purified by soxhlet extraction using toluene. This method proved to be convenient and economical, producing a high yield of carbon nanotubes. The MWCNTs were phosphorylated with alkylazido phosphonate compounds through a 1,3-dipolar cycloaddition reaction between the phosphonate azides and the C=C bonds of the MWCNTs, with nitrogen loss occurring upon thermolysis. These p-MWCNTs were then melt compounded with PVC to form the p-MWCNTs / PVC nanocomposites. vii The phosphorylation of the MWCNTs and their dispersion in the PVC matrix were characterized by FTIR, SEM, TEM and Raman spectroscopy. Thermal analysis of the nanocomposites by TGA and DSC showed an enhanced thermal stability when comparing the nanocomposites with neat PVC. The modulus of the MWCNTs / PVC nanocomposites increased whilst there was a reduction in their tensile strength, indicating a decrease in polymer toughness.
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- Authors: Mkhabela, Vuyiswa J.
- Date: 2011-09-13T09:20:26Z
- Subjects: Nanotubes , Carbon nanotubes , Phosphorylation , Nanocomposites (Materials) , Carbon , Vinyl chloride polymers
- Type: Thesis
- Identifier: uj:7198 , http://hdl.handle.net/10210/3833
- Description: M.Sc. , Carbon nanotubes (CNTs) have been of utmost scientific interest since their discovery in 1991 by a Japanese physicist - Sumio Iijima. This is due to their extraordinary properties which make them one of the most promising options for the design of novel ultrahigh strength polymer nanocomposites. It is believed that the high aspect ratio, mechanical strength, and high electrical and thermal conductivity of these CNTs will enhance the performance of many polymer / CNT nanocomposites and open up new applications. However, poor dispersibility and lack of interfacial adhesion of the CNTs in the polymer matrix have remained a challenge towards fabrication of these nanocomposites. This has been due to the atomically smooth surface of the nanotubes and their intrinsic van der Waals forces which make them chemically inert. This study was aimed at exploring this concept by using novel phosphorylated multiwalled carbon nanotubes (p-MWCNTs) and polyvinyl chloride (PVC) polymer. Phosphorylation of MWCNTs has been successfully achieved in our laboratories, with the p-MWCNTs showing improvement in thermal stability. PVC on the other hand, is the world’s second largest thermoplastic material and has physical properties that are key technical advantages for its use in various and diverse fields such as building and construction, electronics, food packaging and in medical applications. A novel solvent-free method was used to synthesize p-MWCNTs / PVC nanocomposites. MWCNTs were synthesized by nebulized spray pyrolysis, a modification of catalytic vapour deposition and purified by soxhlet extraction using toluene. This method proved to be convenient and economical, producing a high yield of carbon nanotubes. The MWCNTs were phosphorylated with alkylazido phosphonate compounds through a 1,3-dipolar cycloaddition reaction between the phosphonate azides and the C=C bonds of the MWCNTs, with nitrogen loss occurring upon thermolysis. These p-MWCNTs were then melt compounded with PVC to form the p-MWCNTs / PVC nanocomposites. vii The phosphorylation of the MWCNTs and their dispersion in the PVC matrix were characterized by FTIR, SEM, TEM and Raman spectroscopy. Thermal analysis of the nanocomposites by TGA and DSC showed an enhanced thermal stability when comparing the nanocomposites with neat PVC. The modulus of the MWCNTs / PVC nanocomposites increased whilst there was a reduction in their tensile strength, indicating a decrease in polymer toughness.
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Recovery of base metals from nitric and sulphiric solutions using carbon nanotubes
- Authors: Mgwetyana, Unathi
- Date: 2014-01-27
- Subjects: Nanotubes , Extraction (Chemistry) , Heavy metals - Absorption and adsorption , Water - Purification - Adsorption
- Type: Thesis
- Identifier: uj:7961 , http://hdl.handle.net/10210/8861
- Description: M.Tech. (Extraction Metallurgy) , For many decades, carbon nanotubes (CNTs) have been used as adsorbents for the removal of pollutants from wastewaters because of their unique properties such as inert surface, resistance to acid and base environment, rigidity and strength. Herein is a report of application of functionalised CNTs on the adsorption of metal ions from aqueous solutions and mine leachates. The CNTs were first synthesised in-house, purified, functionalised and characterised with various characterisation techniques: FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy, TEM (Transmission Electron Microscopy), EDS (Energy Dispersive Spectroscopy), Raman Spectroscopy, TGA (Thermal Gravimetric Analysis) and BET (Brunauer-Emmet-Teller). Together, these techniques gave substantiation for structure, surface and chemical modification of the synthesised moieties. After characterisation, the functional groups were attached to the walls of the tubes and this implies successful functionalisation...
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- Authors: Mgwetyana, Unathi
- Date: 2014-01-27
- Subjects: Nanotubes , Extraction (Chemistry) , Heavy metals - Absorption and adsorption , Water - Purification - Adsorption
- Type: Thesis
- Identifier: uj:7961 , http://hdl.handle.net/10210/8861
- Description: M.Tech. (Extraction Metallurgy) , For many decades, carbon nanotubes (CNTs) have been used as adsorbents for the removal of pollutants from wastewaters because of their unique properties such as inert surface, resistance to acid and base environment, rigidity and strength. Herein is a report of application of functionalised CNTs on the adsorption of metal ions from aqueous solutions and mine leachates. The CNTs were first synthesised in-house, purified, functionalised and characterised with various characterisation techniques: FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy, TEM (Transmission Electron Microscopy), EDS (Energy Dispersive Spectroscopy), Raman Spectroscopy, TGA (Thermal Gravimetric Analysis) and BET (Brunauer-Emmet-Teller). Together, these techniques gave substantiation for structure, surface and chemical modification of the synthesised moieties. After characterisation, the functional groups were attached to the walls of the tubes and this implies successful functionalisation...
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The synthesis of modified chlorophyll carbon nanotube photoactive dyad systems
- Authors: Msane, Gugu
- Date: 2012-08-22
- Subjects: Nanotubes , Chlorophyll synthesis , Electron donor-acceptor complexes , Charge exchange , Transmission electron microscopy , Scanning electron microscopy , High resolution electron microscopy
- Type: Thesis
- Identifier: uj:2933 , http://hdl.handle.net/10210/6361
- Description: M.Sc. , Donor-acceptor (D-A) systems consist of a donor covalently or non-covalently linked to an acceptor. The simplest D–A system consists of a donor linked to an acceptor and is called a dyad system. Photoactive dyad systems are molecular devices designed to perform through the separation of charge separation states and the conversion of solar energy to chemical energy in analogy to photosynthesis.1 These dyad systems consist of a donor which is usually a chromophore and an acceptor. The design of these systems is guided to mimic photo-induced electron transfer (PET) and charge separation (CS), which are fundamental processes of photosynthesis. In nature, photosynthetic units are often built from dyads consisting of pigments like chlorophyll (donors), non–covalently linked to quinones, (acceptors). The donor harvests light energy and transfers the energy to the nearby pigment molecules until it eventually reaches a special region of the chlorophyll macrocycle called the reaction centre where this light energy is then converted to electrochemical energy. Photoactive dyad systems act as artificial photosynthetic models as they reproduce photo–induced electron transfer and charge separation of natural photosynthesis. In this project, dyad systems were made by covalently linking zinc pheophorbide, a modified chlorophyll derivative to double–walled carbon nanotubes (DWCNTs). Zinc pheophorbide acts as the donor and DWCNTs as the acceptors. Chlorophyll was modified by cutting the phytol chain and inserting zinc as the central metal to yield zinc pheophorbide. This derivative is stable against irradiation, has a good range of acceptor wavelength and is also a good light harvester. DWCNTs are one dimensional nanowires with two concentric tubes. They readily accept electrons because they have an extended π electron system. These electrons are then transported efficiently under ballistic conditions. DWCNTs were synthesised by catalytic chemical vapour deposition (CCVD) of methane over Mg0.99Co0.075Mo0.025O catalyst. In dyad system 1, amidated zinc pheophorbide molecules were covalently attached to oxidised DWCNTs in the presence of N–ethyl–N’–(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) \ and N–hydroxysuccinnimide (NHS) as a catalysts. Dyad system 2 was synthesized by attaching zinc pheophorbide molecules to amidated DWCNTs using the same catalysts.
- Full Text:
- Authors: Msane, Gugu
- Date: 2012-08-22
- Subjects: Nanotubes , Chlorophyll synthesis , Electron donor-acceptor complexes , Charge exchange , Transmission electron microscopy , Scanning electron microscopy , High resolution electron microscopy
- Type: Thesis
- Identifier: uj:2933 , http://hdl.handle.net/10210/6361
- Description: M.Sc. , Donor-acceptor (D-A) systems consist of a donor covalently or non-covalently linked to an acceptor. The simplest D–A system consists of a donor linked to an acceptor and is called a dyad system. Photoactive dyad systems are molecular devices designed to perform through the separation of charge separation states and the conversion of solar energy to chemical energy in analogy to photosynthesis.1 These dyad systems consist of a donor which is usually a chromophore and an acceptor. The design of these systems is guided to mimic photo-induced electron transfer (PET) and charge separation (CS), which are fundamental processes of photosynthesis. In nature, photosynthetic units are often built from dyads consisting of pigments like chlorophyll (donors), non–covalently linked to quinones, (acceptors). The donor harvests light energy and transfers the energy to the nearby pigment molecules until it eventually reaches a special region of the chlorophyll macrocycle called the reaction centre where this light energy is then converted to electrochemical energy. Photoactive dyad systems act as artificial photosynthetic models as they reproduce photo–induced electron transfer and charge separation of natural photosynthesis. In this project, dyad systems were made by covalently linking zinc pheophorbide, a modified chlorophyll derivative to double–walled carbon nanotubes (DWCNTs). Zinc pheophorbide acts as the donor and DWCNTs as the acceptors. Chlorophyll was modified by cutting the phytol chain and inserting zinc as the central metal to yield zinc pheophorbide. This derivative is stable against irradiation, has a good range of acceptor wavelength and is also a good light harvester. DWCNTs are one dimensional nanowires with two concentric tubes. They readily accept electrons because they have an extended π electron system. These electrons are then transported efficiently under ballistic conditions. DWCNTs were synthesised by catalytic chemical vapour deposition (CCVD) of methane over Mg0.99Co0.075Mo0.025O catalyst. In dyad system 1, amidated zinc pheophorbide molecules were covalently attached to oxidised DWCNTs in the presence of N–ethyl–N’–(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) \ and N–hydroxysuccinnimide (NHS) as a catalysts. Dyad system 2 was synthesized by attaching zinc pheophorbide molecules to amidated DWCNTs using the same catalysts.
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