Bis(pyrazolyl) chromium(III), nickel(II) and palladium(II) complexes as ethylene oligomerization and polymerization catalysts
- Authors: Miti, Nangamso Alicia
- Date: 2010-03-10T06:22:17Z
- Subjects: Chromium compounds , Nickel compounds , Nickel catalysts , Palladium compounds , Palladium catalysts , Polymerization , Ethylene , Chromium catalysts
- Type: Thesis
- Identifier: uj:6656 , http://hdl.handle.net/10210/3062
- Description: M.Sc. , In search of developing new pyrazolyl complexes that can be used for ethylene transformation reactions, bis(pyrazolyl)alky carbonyl and amine complexes were prepared. The reaction between 3,5-dimethylpyrazole with alkyl-carbonyl chloride linkers in the presence of triethylamine as a base produced the ligands, 1,3-bis(3,5- dimethylpyrazol-1-yl)-propan-1-one (L1), 1,2-bis(3,5-dimethylpyrazol-1-yl)-ethane- 1,2-dione (L2), 1,4-bis(3,5-dimethylpyrazol-1-yl)-butane-1,4-dione (L3) and 1,6- bis(3,5-dimethylpyrazol-1-yl)-hexane-1,6-dione (L4) as white to brown crystalline solids in good yields. Ligand L5 was prepared by using bis(2-chloroethyl)-amine hydrochloride and 3,5- dimethylpyrazolevia via a phase-transfer reaction, while L6 was obtained using the bis(2-chloroethyl)-amine hydrochloride and 3,5-diphenypyrazole in the presence of triethylamine as a base. They were isolated in moderate yields, while their ditertiarypyrazole derivative was not obtained at all. All the ligands were characterized by a combination of 1H and 13C{1H}-NMR spectroscopy, infrared spectroscopy, elemental analysis and mass spectrometry. Ligands L1 and L4 were further confirmed by X-ray crystallography. Ligands L1 and L6 were subsequently used to prepare their corresponding Pd, Ni and Cr complexes. L1 was reacted with [PdCl2(NCMe)2] to form a bidentate complex 1,3- bis-(3,5-dimethylpyrazol-1-yl)-propan-1-one palladium dichloride (1a) when the reaction was heated at 80 oC, while a tridentate complex 1,3-bis(3,5-dimethylpyrazol- 1-yl)-propan-1-one palladium chloride (1b) was obtained when the reaction was refluxed. 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-1-one nickel(II) bromide (2) was obtained when NiBr2 was reacted with L1 at room temperature while the reaction between L1 and [CrCl3(THF)3] gave 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-1-one chromium(III) chloride (3). Ligand L6 was reacted with the same metal salts to give bis[2-(3,5-dimethylpyrazol- 1-yl)-ethyl] amine palladium(II) chloride (4), bis[2-(3,5-dimethylpyrazol-1-yl)-ethyl] amine nickel(II) chloride (5) and bis[2-(3,5-dimethylpyrazol-1-yl)-ethyl] amine chromium(III) chloride (6). All the complexes were characterized by the already mentioned characterization techniques and X-ray analysis was performed for 1b and 4. Ethylene transformation reactions were performed with complexes 1a, 2, 3, 5 and 6, and complexes 1a and 4 were not used because of their geometrical structures, which prevented them to be active for such reactions. Using MMAO and EtAlCl2 as cocatalysts complexes 1a and 3 showed no activity, however complexes 2 and 6 were active. Complex 2 was used with MMAO and showed no activity, while with EtAlCl2 oligomers were produced. Gas-chromatography analysis of the products showed that C6-C14+ oligomers were obtained. Temperature variation reactions performed under standard conditions of 20 bar ethylene pressure and 200 equivalents of EtAlCl2 in one hour showed that certain oligomers were not favoured under certain temperatures. Ethylene reactions with complex 6 and EtAlCl2 did not form any product but with MMAO polymer material was obtained. Analysis of the polymer by differential scanning calometry proved that the product was high density polyethylene. Studies of temperature, co-catalyst and pressure variations were performed. As expected for temperature studies the catalyst decomposed at high temperatures (above 40 oC), while for co-catalyst studies 3000 equivalents of MMAO gave the lowest TON. Pressure variations studies showed that an increase in ethylene pressure also increased the TON, but above 30 bar the activity became stable.
- Full Text:
- Authors: Miti, Nangamso Alicia
- Date: 2010-03-10T06:22:17Z
- Subjects: Chromium compounds , Nickel compounds , Nickel catalysts , Palladium compounds , Palladium catalysts , Polymerization , Ethylene , Chromium catalysts
- Type: Thesis
- Identifier: uj:6656 , http://hdl.handle.net/10210/3062
- Description: M.Sc. , In search of developing new pyrazolyl complexes that can be used for ethylene transformation reactions, bis(pyrazolyl)alky carbonyl and amine complexes were prepared. The reaction between 3,5-dimethylpyrazole with alkyl-carbonyl chloride linkers in the presence of triethylamine as a base produced the ligands, 1,3-bis(3,5- dimethylpyrazol-1-yl)-propan-1-one (L1), 1,2-bis(3,5-dimethylpyrazol-1-yl)-ethane- 1,2-dione (L2), 1,4-bis(3,5-dimethylpyrazol-1-yl)-butane-1,4-dione (L3) and 1,6- bis(3,5-dimethylpyrazol-1-yl)-hexane-1,6-dione (L4) as white to brown crystalline solids in good yields. Ligand L5 was prepared by using bis(2-chloroethyl)-amine hydrochloride and 3,5- dimethylpyrazolevia via a phase-transfer reaction, while L6 was obtained using the bis(2-chloroethyl)-amine hydrochloride and 3,5-diphenypyrazole in the presence of triethylamine as a base. They were isolated in moderate yields, while their ditertiarypyrazole derivative was not obtained at all. All the ligands were characterized by a combination of 1H and 13C{1H}-NMR spectroscopy, infrared spectroscopy, elemental analysis and mass spectrometry. Ligands L1 and L4 were further confirmed by X-ray crystallography. Ligands L1 and L6 were subsequently used to prepare their corresponding Pd, Ni and Cr complexes. L1 was reacted with [PdCl2(NCMe)2] to form a bidentate complex 1,3- bis-(3,5-dimethylpyrazol-1-yl)-propan-1-one palladium dichloride (1a) when the reaction was heated at 80 oC, while a tridentate complex 1,3-bis(3,5-dimethylpyrazol- 1-yl)-propan-1-one palladium chloride (1b) was obtained when the reaction was refluxed. 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-1-one nickel(II) bromide (2) was obtained when NiBr2 was reacted with L1 at room temperature while the reaction between L1 and [CrCl3(THF)3] gave 1,3-bis(3,5-dimethylpyrazol-1-yl)-propan-1-one chromium(III) chloride (3). Ligand L6 was reacted with the same metal salts to give bis[2-(3,5-dimethylpyrazol- 1-yl)-ethyl] amine palladium(II) chloride (4), bis[2-(3,5-dimethylpyrazol-1-yl)-ethyl] amine nickel(II) chloride (5) and bis[2-(3,5-dimethylpyrazol-1-yl)-ethyl] amine chromium(III) chloride (6). All the complexes were characterized by the already mentioned characterization techniques and X-ray analysis was performed for 1b and 4. Ethylene transformation reactions were performed with complexes 1a, 2, 3, 5 and 6, and complexes 1a and 4 were not used because of their geometrical structures, which prevented them to be active for such reactions. Using MMAO and EtAlCl2 as cocatalysts complexes 1a and 3 showed no activity, however complexes 2 and 6 were active. Complex 2 was used with MMAO and showed no activity, while with EtAlCl2 oligomers were produced. Gas-chromatography analysis of the products showed that C6-C14+ oligomers were obtained. Temperature variation reactions performed under standard conditions of 20 bar ethylene pressure and 200 equivalents of EtAlCl2 in one hour showed that certain oligomers were not favoured under certain temperatures. Ethylene reactions with complex 6 and EtAlCl2 did not form any product but with MMAO polymer material was obtained. Analysis of the polymer by differential scanning calometry proved that the product was high density polyethylene. Studies of temperature, co-catalyst and pressure variations were performed. As expected for temperature studies the catalyst decomposed at high temperatures (above 40 oC), while for co-catalyst studies 3000 equivalents of MMAO gave the lowest TON. Pressure variations studies showed that an increase in ethylene pressure also increased the TON, but above 30 bar the activity became stable.
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Chromium and iron complexes of nitrogen donor ligands as olefin oligomerization and polymerization catalysts
- Authors: Yankey, Margaret
- Date: 2014-10-13
- Subjects: Polyolefins , Oligomerization , Oligomers , Polymerization
- Type: Thesis
- Identifier: uj:12591 , http://hdl.handle.net/10210/12380
- Description: Ph.D. (Chemistry) , Please refer to full text to view abstract
- Full Text:
- Authors: Yankey, Margaret
- Date: 2014-10-13
- Subjects: Polyolefins , Oligomerization , Oligomers , Polymerization
- Type: Thesis
- Identifier: uj:12591 , http://hdl.handle.net/10210/12380
- Description: Ph.D. (Chemistry) , Please refer to full text to view abstract
- Full Text:
Synthesis, characterization and application of Schiff base cobalt and zinc complexes as catalysts for CO2 and epoxide copolymerization reaction
- Authors: Lephoto, Mapudumo Lydia
- Date: 2013-07-24
- Subjects: Zinc compounds , Cobalt compounds , Transition metal catalysts , Copolymers , Polymerization , Epoxy compounds
- Type: Thesis
- Identifier: uj:7660 , http://hdl.handle.net/10210/8529
- Description: M.Sc. (Chemistry) , Pyrazolyl and imidazolyl-based compounds were used as ligands in the synthesis of cobalt(II) and zinc(II) complexes. These ligands were prepared using literature methods.
- Full Text:
- Authors: Lephoto, Mapudumo Lydia
- Date: 2013-07-24
- Subjects: Zinc compounds , Cobalt compounds , Transition metal catalysts , Copolymers , Polymerization , Epoxy compounds
- Type: Thesis
- Identifier: uj:7660 , http://hdl.handle.net/10210/8529
- Description: M.Sc. (Chemistry) , Pyrazolyl and imidazolyl-based compounds were used as ligands in the synthesis of cobalt(II) and zinc(II) complexes. These ligands were prepared using literature methods.
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Pyrazole and pyrazolyl copper and zinc complexes in ring opening polymerization of ε-caprolactone and D,L-lactide
- Authors: Appavoo, Divambal
- Date: 2012-06-07
- Subjects: Pyrazoles , Copper , Zinc , Polymerization , Caprolactones , Lactides
- Type: Thesis
- Identifier: uj:8668 , http://hdl.handle.net/10210/5023
- Description: M.Sc. , Six pyrazole and pyrazolyl compounds, 3,5-dimethylpyrazole (L1), 3,5-diphenylpyrazole (L2), 3,5-di-tert-butylpyrazole (L3), bis(3,5-dimethylpyrazol-1-yl)methane (L4), bis(3,5-diphenylpyrazol-1-yl)methane (L5) and bis(1,2-bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L6), were reacted with Zn(II) and Cu(II) benzoates to form pyrazole and pyrazolyl metal benzoates. The complexes are [Zn(C6H5COO)2(L1)2] (1), [Zn(3,5-NO2-C6H3COO)2(L1)2] (2), [Zn(4-OH-C6H4COO)2(L1)2] (3), [Zn(2-Cl-C6H4COO)2(L1)2] (4), [Zn(C6H5COO)2(L2)2] (5), [Zn(3,5-NO2-C6H3COO)2(L2)2] (6), [Zn(4-OH-C6H4COO)2(L2)2] (7), [Zn(2-Cl-C6H4COO)2(L2)2] (8), [Zn(3,5-NO2-C6H3COO)2L4] (9), [Zn(4-OH-C6H4COO)2L6] (10), [Zn2(C6H5COO)4L6]n (11), [Zn(3,5-NO2-C6H3COO)2L6] (12), [Zn(2-Cl-C6H4COO)2L6] (13), [Cu(C6H5COO)2(L1)2] (14), [Cu(3,5-NO2-C6H3COO)2(L1)2] (15), [Cu(4-OH-C6H4COO)2(L1)2] (16), [Cu(2-Cl-C6H4COO)2(L1)2] (17), [Cu(C6H5COO)2(C6H5COOH)]2 (18), [Cu(2-Cl-C6H4COO)2(L3)2] (19), [Cu(C6H5COO)2L4] (20), [Cu(2-Cl-C6H4COO)2L4] (21), [Cu(C6H5COO)2DMSO]2 (22), [Cu(C6H5COO)2L6]2 (23), [Cu(2-Cl-C6H4COO)2L6]2n (24), [Cu(4-OH-C6H4COO)2L6]2(25) and [Cu(3,5-NO2-C6H3COO)2L6]n (26). The molecular structures of the Zn(II) and Cu(II) complexes 6, 9, 11, 14, 17-19, 22-26 were determined by X-ray diffraction studies that revealed four types of geometries adopted by these complexes: (i) 4-coordinate tetrahedral (6, 9, 14), (ii) 6-coordinate octahedral (17), (iii) paddle wheel (18, 19, 22, 23, 25) and (iv) polymeric structures (11, 24, 26). Catalysis studies performed with selected complexes (1-4, 9-17, 23-26) revealed that they initiate the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and D,L-lactide at elevated temperatures, and under solvent-free conditions and in toluene respectively. Polycaprolactone (PCL) and poly(D,L-lactide) (PLA) produced were of moderate molecular weights (858-4 757 Da for PCL and 602-3 185 Da for PLA) and polydispersity indices (1.36-2.16 for PCL and 1.42-2.35 for PLA). End group of the iv polymers, determined by MALDI-TOF MS, were benzoates, hydroxyl, methoxy groups and cyclic. From the 13C{1H} NMR spectra of polymers synthesized, the stereochemistry of PLA was predominantly isotactic.
- Full Text:
- Authors: Appavoo, Divambal
- Date: 2012-06-07
- Subjects: Pyrazoles , Copper , Zinc , Polymerization , Caprolactones , Lactides
- Type: Thesis
- Identifier: uj:8668 , http://hdl.handle.net/10210/5023
- Description: M.Sc. , Six pyrazole and pyrazolyl compounds, 3,5-dimethylpyrazole (L1), 3,5-diphenylpyrazole (L2), 3,5-di-tert-butylpyrazole (L3), bis(3,5-dimethylpyrazol-1-yl)methane (L4), bis(3,5-diphenylpyrazol-1-yl)methane (L5) and bis(1,2-bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L6), were reacted with Zn(II) and Cu(II) benzoates to form pyrazole and pyrazolyl metal benzoates. The complexes are [Zn(C6H5COO)2(L1)2] (1), [Zn(3,5-NO2-C6H3COO)2(L1)2] (2), [Zn(4-OH-C6H4COO)2(L1)2] (3), [Zn(2-Cl-C6H4COO)2(L1)2] (4), [Zn(C6H5COO)2(L2)2] (5), [Zn(3,5-NO2-C6H3COO)2(L2)2] (6), [Zn(4-OH-C6H4COO)2(L2)2] (7), [Zn(2-Cl-C6H4COO)2(L2)2] (8), [Zn(3,5-NO2-C6H3COO)2L4] (9), [Zn(4-OH-C6H4COO)2L6] (10), [Zn2(C6H5COO)4L6]n (11), [Zn(3,5-NO2-C6H3COO)2L6] (12), [Zn(2-Cl-C6H4COO)2L6] (13), [Cu(C6H5COO)2(L1)2] (14), [Cu(3,5-NO2-C6H3COO)2(L1)2] (15), [Cu(4-OH-C6H4COO)2(L1)2] (16), [Cu(2-Cl-C6H4COO)2(L1)2] (17), [Cu(C6H5COO)2(C6H5COOH)]2 (18), [Cu(2-Cl-C6H4COO)2(L3)2] (19), [Cu(C6H5COO)2L4] (20), [Cu(2-Cl-C6H4COO)2L4] (21), [Cu(C6H5COO)2DMSO]2 (22), [Cu(C6H5COO)2L6]2 (23), [Cu(2-Cl-C6H4COO)2L6]2n (24), [Cu(4-OH-C6H4COO)2L6]2(25) and [Cu(3,5-NO2-C6H3COO)2L6]n (26). The molecular structures of the Zn(II) and Cu(II) complexes 6, 9, 11, 14, 17-19, 22-26 were determined by X-ray diffraction studies that revealed four types of geometries adopted by these complexes: (i) 4-coordinate tetrahedral (6, 9, 14), (ii) 6-coordinate octahedral (17), (iii) paddle wheel (18, 19, 22, 23, 25) and (iv) polymeric structures (11, 24, 26). Catalysis studies performed with selected complexes (1-4, 9-17, 23-26) revealed that they initiate the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and D,L-lactide at elevated temperatures, and under solvent-free conditions and in toluene respectively. Polycaprolactone (PCL) and poly(D,L-lactide) (PLA) produced were of moderate molecular weights (858-4 757 Da for PCL and 602-3 185 Da for PLA) and polydispersity indices (1.36-2.16 for PCL and 1.42-2.35 for PLA). End group of the iv polymers, determined by MALDI-TOF MS, were benzoates, hydroxyl, methoxy groups and cyclic. From the 13C{1H} NMR spectra of polymers synthesized, the stereochemistry of PLA was predominantly isotactic.
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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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Polymerization of cyclodextrin-ionic liquid complexes for the removal of organic and inorganic contaminants from water
- Mahlambi, Mphilisi Mciniseli
- Authors: Mahlambi, Mphilisi Mciniseli
- Date: 2009-05-07T07:23:12Z
- Subjects: Polymerization , Water purification , Organic compounds removal , Cyclodextrins
- Type: Thesis
- Identifier: uj:8361 , http://hdl.handle.net/10210/2502
- Description: M.Sc. , The prevalence of toxic contaminants in water remains a huge challenge for water supplying companies and municipalities. Both organic and inorganic contaminants (especially heavy metals) pollutants are often present in water distribution networks. Organic and inorganic pollutants often co-occur in drinking water networks. However, at present there is no water treatment intervention that simultaneously removes organic and inorganic pollutants from water. Additionally, current water treatment technologies fail to remove these contaminants to parts per billion (ppb or µg.L-1) levels. Methods that can simultaneously remove organic and inorganic pollutants to desired levels need to be developed. In our laboratories, both functionalised and unfunctionalised cyclodextrin (CD) polymers have demonstrated the ability to effectively remove organic species from water at low (ppb) concentrations. Cyclodextrins (CDs), which are cyclic oligomers consisting of glucopyranosyl units linked together through α-1,4-glycosidic linkages, behave like molecular hosts. They are capable of interacting with a range of guest molecules within their cylindrical hydrophobic cavities thereby forming the so-called inclusion complexes. Their solubility in water, however, precludes their application in the removal of organic pollutants from water. This limitation is easily dealt with by polymerizing the CDs into water insoluble polymers with suitable bifunctional linkers. On the other hand, ionic liquids (ILs) have been reported to “absorb” heavy metal ions from aqueous media. ILs are low melting point molten salts that are composed of organic cations (e.g. imidazolium and pyridinium ions) and mostly inorganic anions like Cl–, Br–, [PF6]– and [BF4]–. In this study, the two systems were combined by an initial attachment of the imidazolium or pyridinium rings to the cyclodextrin moiety. Polymerisation of the resulting cyclodextrin-ionic liquid (CD-IL) complexes with a suitable linker produced the corresponding water insoluble CD-IL polymers. This dual system has shown excellent capabilities for the removal of model pollutants such as p-nitrophenol (PNP) and 2,4,6-trichlorophenol (TCP) and chromium (Cr6+) from aqueous media. However, the CD-IL polymers showed very little affinity for the absorption of cadmium from water. TGA and DSC studies showed that these polymers are stable over a wide range of temperatures (100-400 C).
- Full Text:
- Authors: Mahlambi, Mphilisi Mciniseli
- Date: 2009-05-07T07:23:12Z
- Subjects: Polymerization , Water purification , Organic compounds removal , Cyclodextrins
- Type: Thesis
- Identifier: uj:8361 , http://hdl.handle.net/10210/2502
- Description: M.Sc. , The prevalence of toxic contaminants in water remains a huge challenge for water supplying companies and municipalities. Both organic and inorganic contaminants (especially heavy metals) pollutants are often present in water distribution networks. Organic and inorganic pollutants often co-occur in drinking water networks. However, at present there is no water treatment intervention that simultaneously removes organic and inorganic pollutants from water. Additionally, current water treatment technologies fail to remove these contaminants to parts per billion (ppb or µg.L-1) levels. Methods that can simultaneously remove organic and inorganic pollutants to desired levels need to be developed. In our laboratories, both functionalised and unfunctionalised cyclodextrin (CD) polymers have demonstrated the ability to effectively remove organic species from water at low (ppb) concentrations. Cyclodextrins (CDs), which are cyclic oligomers consisting of glucopyranosyl units linked together through α-1,4-glycosidic linkages, behave like molecular hosts. They are capable of interacting with a range of guest molecules within their cylindrical hydrophobic cavities thereby forming the so-called inclusion complexes. Their solubility in water, however, precludes their application in the removal of organic pollutants from water. This limitation is easily dealt with by polymerizing the CDs into water insoluble polymers with suitable bifunctional linkers. On the other hand, ionic liquids (ILs) have been reported to “absorb” heavy metal ions from aqueous media. ILs are low melting point molten salts that are composed of organic cations (e.g. imidazolium and pyridinium ions) and mostly inorganic anions like Cl–, Br–, [PF6]– and [BF4]–. In this study, the two systems were combined by an initial attachment of the imidazolium or pyridinium rings to the cyclodextrin moiety. Polymerisation of the resulting cyclodextrin-ionic liquid (CD-IL) complexes with a suitable linker produced the corresponding water insoluble CD-IL polymers. This dual system has shown excellent capabilities for the removal of model pollutants such as p-nitrophenol (PNP) and 2,4,6-trichlorophenol (TCP) and chromium (Cr6+) from aqueous media. However, the CD-IL polymers showed very little affinity for the absorption of cadmium from water. TGA and DSC studies showed that these polymers are stable over a wide range of temperatures (100-400 C).
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Fluorescent molecular sensors based on photoresponsive modified β-cyclodextrin and crown ethers for detecting organic molecules and metal ions in water
- Authors: Ncube, Phendukani
- Date: 2013-12-09
- Subjects: Fluorescence spectroscopy , Cyclodextrins - Synthesis , Crown ethers - Synthesis , Polymerization , Biosensors
- Type: Thesis
- Identifier: uj:7865 , http://hdl.handle.net/10210/8758
- Description: D.Phil. (Chemistry) , The problem of maintaining good quality of water for domestic use and for aquatic life remains a challenge. Water sources are often contaminated with pollutants from natural sources such as volcanic eruptions and by human activities such as manufacturing industries, mining, water-purification processes, agricultural activities and a vast number of other activities. Water-purification processes used by municipal authorities are designed to remove most of the pollutants but some trace amounts will always remain and have been detected in drinking water and treated waste water reservoirs. These trace amounts pose a threat to human health and the well-being of aquatic life. The detection of these trace amounts of pollutants is often carried out by laboratory-based techniques that require sophisticated, expensive instruments and often require extensive sample preparation and pre-concentration. Simple, quick and in-field detection methods are necessary especially for remote small communities with limited or no access to laboratories. Optical detection systems offer hope as a solution to this problem. In this work newly developed fluorescence-based molecular sensors for the detection of pollutants in water were developed, characterised and tested for their sensing abilities towards organic and inorganic pollutants. The fluorescent probes for organic pollutants were designed based on the host-guest chemistry of the cyclodextrin molecule. Azo dye-modified β-cyclodextrins were synthesised and linked via ethylene glycol and epichlorohydrin to produce the sensors that were then tested for their sensing response towards chlorophenols and small aliphatic chlorinated alkanes which are often formed during the disinfection of water in the purification process. The sensor molecules were characterised by UV-Vis, FT-IR and 1D and 2D NMR spectroscopy. The amount of cyclodextrin in each sensor molecule was quantified using the anthrone method (67%) as well as by 1H-NMR spectroscopy (72%). To demonstrate the host-guest interaction of the sensor molecules, isothermal titration calorimetry (ITC) was used. ITC measurements showed that modifying β-cyclodextrin and using linkers did not alter its host-guest interaction with guest molecules as demonstrated by the stoichiometry, n, stability (or binding or association) constant (K) and thermodynamic parameters of the interaction. The sensor molecule linked via ethylene glycol showed selectivity towards 4- chlorophenol among the chlorophenols investigated and has the potential to be used in a sensor for the detection of 4-chlorophenol. The sensor molecule linked via epichlorohydrin showed sensitivity towards chloroform, a typical disinfection by-product. These experimental results showed that the sensor molecules could be used for quick on-field detection of chlorinated organic compounds in water. Sensor molecules for inorganic pollutants were based on the complex formation of crown ethers with metal ions. The sensor was formed by modifying a dibenzo-18- crown-6 ether molecule with an azo dye. The sensor was then characterised using UV-Vis spectrophotmetry, FT-IR and NMR spectroscopies as well as mass spectrometry and CHNS elemental analysis. The sensor molecule was then subjected to different metal ions and the fluorescence change of the probe observed. Interestingly, the sensor was highly sensitive and selective to mercury (II) and Cu (II) ions in water. Mercury (II) is one of the most hazardous heavy metals among the heavy-metal ions found in environmental waters and its early detection in water sources is important. The synthesised molecular sensor can therefore be incorporated into a simple hand-held gadget with a light source and be used for on-field detection of mercury (II) ions in remote areas.
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- Authors: Ncube, Phendukani
- Date: 2013-12-09
- Subjects: Fluorescence spectroscopy , Cyclodextrins - Synthesis , Crown ethers - Synthesis , Polymerization , Biosensors
- Type: Thesis
- Identifier: uj:7865 , http://hdl.handle.net/10210/8758
- Description: D.Phil. (Chemistry) , The problem of maintaining good quality of water for domestic use and for aquatic life remains a challenge. Water sources are often contaminated with pollutants from natural sources such as volcanic eruptions and by human activities such as manufacturing industries, mining, water-purification processes, agricultural activities and a vast number of other activities. Water-purification processes used by municipal authorities are designed to remove most of the pollutants but some trace amounts will always remain and have been detected in drinking water and treated waste water reservoirs. These trace amounts pose a threat to human health and the well-being of aquatic life. The detection of these trace amounts of pollutants is often carried out by laboratory-based techniques that require sophisticated, expensive instruments and often require extensive sample preparation and pre-concentration. Simple, quick and in-field detection methods are necessary especially for remote small communities with limited or no access to laboratories. Optical detection systems offer hope as a solution to this problem. In this work newly developed fluorescence-based molecular sensors for the detection of pollutants in water were developed, characterised and tested for their sensing abilities towards organic and inorganic pollutants. The fluorescent probes for organic pollutants were designed based on the host-guest chemistry of the cyclodextrin molecule. Azo dye-modified β-cyclodextrins were synthesised and linked via ethylene glycol and epichlorohydrin to produce the sensors that were then tested for their sensing response towards chlorophenols and small aliphatic chlorinated alkanes which are often formed during the disinfection of water in the purification process. The sensor molecules were characterised by UV-Vis, FT-IR and 1D and 2D NMR spectroscopy. The amount of cyclodextrin in each sensor molecule was quantified using the anthrone method (67%) as well as by 1H-NMR spectroscopy (72%). To demonstrate the host-guest interaction of the sensor molecules, isothermal titration calorimetry (ITC) was used. ITC measurements showed that modifying β-cyclodextrin and using linkers did not alter its host-guest interaction with guest molecules as demonstrated by the stoichiometry, n, stability (or binding or association) constant (K) and thermodynamic parameters of the interaction. The sensor molecule linked via ethylene glycol showed selectivity towards 4- chlorophenol among the chlorophenols investigated and has the potential to be used in a sensor for the detection of 4-chlorophenol. The sensor molecule linked via epichlorohydrin showed sensitivity towards chloroform, a typical disinfection by-product. These experimental results showed that the sensor molecules could be used for quick on-field detection of chlorinated organic compounds in water. Sensor molecules for inorganic pollutants were based on the complex formation of crown ethers with metal ions. The sensor was formed by modifying a dibenzo-18- crown-6 ether molecule with an azo dye. The sensor was then characterised using UV-Vis spectrophotmetry, FT-IR and NMR spectroscopies as well as mass spectrometry and CHNS elemental analysis. The sensor molecule was then subjected to different metal ions and the fluorescence change of the probe observed. Interestingly, the sensor was highly sensitive and selective to mercury (II) and Cu (II) ions in water. Mercury (II) is one of the most hazardous heavy metals among the heavy-metal ions found in environmental waters and its early detection in water sources is important. The synthesised molecular sensor can therefore be incorporated into a simple hand-held gadget with a light source and be used for on-field detection of mercury (II) ions in remote areas.
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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...
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Biphenolate and cyclopentadienyl-derived complexes of zirconium and titanium as catalysts for the polymerisation of alpha olefins
- Authors: Van Zyl, Aletta
- Date: 2012-09-04
- Subjects: Oligomers , Polymerization , Zirconium , Alkenes , Titanium
- Type: Thesis
- Identifier: uj:3459 , http://hdl.handle.net/10210/6852
- Description: M.Sc. , An annual production of approximately 46 million metric tons of polyolefins worldwide, emphasizes the industrial importance of this product and the polymerisation process. Olefins are the basic building block of the petrochemical industry and are therefore readily available and cheap. Reactivity of olefins decreases from ethylene to propylene to 1-octene and makes the study of polymerisation catalysts more complex, seeing that the activity of a catalyst differs from monomer to monomer. In this study zirconocene complexes with bridged cyclopentadienyl ligands have been prepared and investigated as , possible catalysts for the polymerisation of higher aolefins. Fulvenes have been reductively coupled and used as ligands for zirconium complexes. Steric bulk of the substituents on the ligand have been increased and changes in the polymeric products have been studied. The tacticty, endgroups and chain lengths of the polyolefins have been investigated. There is currently a considerable interest in the development of 'non-metallocene' catalysts as alternatives for the polymerisation and oligomerisation of a-olefins. Chelating diamide complexes of Group 4 metals have been the focus of much attention and these compounds have shown moderate to high reactivity. However, only a few examples of the corresponding chelating alkoxides are known. In this study, alkoxide complexes of zirconium and titanium have been prepared with Schiff bases as ligands. These complexes have been evaluated as polymerisation catalysts and the products have been studied. The titanium complexes were more active than the zirconium analogues. The narrow molecular weight distribution of the polyolefins gave evidence that these catalysts are single-sited catalysts.
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- Authors: Van Zyl, Aletta
- Date: 2012-09-04
- Subjects: Oligomers , Polymerization , Zirconium , Alkenes , Titanium
- Type: Thesis
- Identifier: uj:3459 , http://hdl.handle.net/10210/6852
- Description: M.Sc. , An annual production of approximately 46 million metric tons of polyolefins worldwide, emphasizes the industrial importance of this product and the polymerisation process. Olefins are the basic building block of the petrochemical industry and are therefore readily available and cheap. Reactivity of olefins decreases from ethylene to propylene to 1-octene and makes the study of polymerisation catalysts more complex, seeing that the activity of a catalyst differs from monomer to monomer. In this study zirconocene complexes with bridged cyclopentadienyl ligands have been prepared and investigated as , possible catalysts for the polymerisation of higher aolefins. Fulvenes have been reductively coupled and used as ligands for zirconium complexes. Steric bulk of the substituents on the ligand have been increased and changes in the polymeric products have been studied. The tacticty, endgroups and chain lengths of the polyolefins have been investigated. There is currently a considerable interest in the development of 'non-metallocene' catalysts as alternatives for the polymerisation and oligomerisation of a-olefins. Chelating diamide complexes of Group 4 metals have been the focus of much attention and these compounds have shown moderate to high reactivity. However, only a few examples of the corresponding chelating alkoxides are known. In this study, alkoxide complexes of zirconium and titanium have been prepared with Schiff bases as ligands. These complexes have been evaluated as polymerisation catalysts and the products have been studied. The titanium complexes were more active than the zirconium analogues. The narrow molecular weight distribution of the polyolefins gave evidence that these catalysts are single-sited catalysts.
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Bimetallic nanoparticles on carbon nanotubes and nanofibers copolymerized with ß-cyclodextrin for water treatment
- Dlamini, Langelihle Nsikayezwe
- Authors: Dlamini, Langelihle Nsikayezwe
- Date: 2014-09-23
- Subjects: Carbon - Nanotubes , Nanofibers , Nanoparticles , Nanostructured materials , Polymerization
- Type: Thesis
- Identifier: uj:12390 , http://hdl.handle.net/10210/12173
- Description: M.Tech. (Chemistry) , Please refer to full text to view abstract
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- Authors: Dlamini, Langelihle Nsikayezwe
- Date: 2014-09-23
- Subjects: Carbon - Nanotubes , Nanofibers , Nanoparticles , Nanostructured materials , Polymerization
- Type: Thesis
- Identifier: uj:12390 , http://hdl.handle.net/10210/12173
- Description: M.Tech. (Chemistry) , Please refer to full text to view abstract
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Dithiocarbamate functionalized glycomonomers and polymers as ligands for gold(i) complexes and as capping agents for gold nanoparticles : synthesis, characterization and their evaluation as anticancer agents
- Authors: Mamba, Saul Mcelwa
- Date: 2015
- Subjects: Polymers - Biotechnology , Gold nanoparticles , Cancer - Treatment , Glycoconjugates , Polymerization
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/58816 , uj:16494
- Description: Abstract: Please refer to full text to view abstract , Ph.D. (Chemistry)
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- Authors: Mamba, Saul Mcelwa
- Date: 2015
- Subjects: Polymers - Biotechnology , Gold nanoparticles , Cancer - Treatment , Glycoconjugates , Polymerization
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/58816 , uj:16494
- Description: Abstract: Please refer to full text to view abstract , Ph.D. (Chemistry)
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Ethylene vinyl acetate-fly ash composites: preparation, characterisation and application in water treatment
- Authors: Maebana, Molahlegi Orienda
- Date: 2012-08-16
- Subjects: Ethylene - Synthesis , Water purification , Composite materials , Fly ash , Phenols - Synthesis , Thermal desorption , Polymerization
- Type: Thesis
- Identifier: uj:9515 , http://hdl.handle.net/10210/5943
- Description: M.Tech. , In this study, ethylene vinyl acetate-fly ash (EVA-FA) composites were explored for the removal of phenols from water. The composites were prepared from EVA and untreated and acid treated fly ash via the melt-mixing technique using a rheomixer. The fly ash was characterised by X-ray fluorescence (XRF), X-ray diffraction (XRD) scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) surface area measurement. Fly ash is composed mainly of SiO2, Al2O3, CaO and Fe2O3. Modified fly ash gave a better specific surface area of 0.4180 m2/g, while 0.0710 m2/g was obtained for unmodified fly-ash due to the disintegration of the outer layer which resulted in smaller particles, hence a larger surface area. EVA-FA composites were prepared from fly ash loadings of 3 to 20% and further characterised by XRD, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and SEM. XRD showed successful incorporation of fly ash into the EVA matrix through the appearance of fly ash diffraction peaks on the EVA-FA composite diffraction pattern. The incorporation of fly ash into the EVA matrix resulted in an improvement in the thermal stability of EVA, but did not have an effect on the melting temperature of the composites. However, a decrease in crystallisation temperature was observed. SEM micrographs revealed uniform dispersion of fly ash particles in the polymer matrix. Adsorption studies were performed using p-chlorophenol (PCP), 2,4,6-trichlorophenol (TCP) and p-nitrophenol (PNP) as model pollutants. An increase in adsorption efficiency of EVA-FA composites was observed as fly ash loading was increased from 3 to 10%. Between 10 and 20% fly-ash loading the removal efficiencies remained constant. The effect of contact time, pH and initial concentration was investigated. Polymer composites prepared from unmodified fly ash resulted in a higher adsorption capacity of phenols. The maximum uptake of PCP was 0.18 mg/g and that for TCP was 0.19 mg/g over a pH range of pH 3 to 5 and after contact time of 8 h. However, the adsorption capacity of 0.30 mg/g for PNP was achieved at pH 5 after a period of 10 h. Equilibrium adsorption data were evaluated using Langmuir and Freundlich adsorption isotherm models. There was no significant difference in the correlation coefficients (R2) from both models for the adsorption of PCP and TCP. However, the equilibrium adsorption data for PNP were better described by the Langmuir adsorption isotherm model. The kinetics data were analysed by pseudo-first-order and pseudo-second-order kinetic models. The pseudo-second-order kinetics model gave better correlation coefficients (> 0.9) for the adsorption of the phenols and the amount adsorbed at equilibrium was comparable to that calculated from the pseudo-second-order equation. Desorption studies were performed using NaOH solution with varying concentrations (0.1 to 0.3 M) and the studies revealed that PNP was the most difficult to be desorbed. Approximately 75% of PNP was recovered while 82% of PCP and 84% of TCP were recovered.
- Full Text:
- Authors: Maebana, Molahlegi Orienda
- Date: 2012-08-16
- Subjects: Ethylene - Synthesis , Water purification , Composite materials , Fly ash , Phenols - Synthesis , Thermal desorption , Polymerization
- Type: Thesis
- Identifier: uj:9515 , http://hdl.handle.net/10210/5943
- Description: M.Tech. , In this study, ethylene vinyl acetate-fly ash (EVA-FA) composites were explored for the removal of phenols from water. The composites were prepared from EVA and untreated and acid treated fly ash via the melt-mixing technique using a rheomixer. The fly ash was characterised by X-ray fluorescence (XRF), X-ray diffraction (XRD) scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) surface area measurement. Fly ash is composed mainly of SiO2, Al2O3, CaO and Fe2O3. Modified fly ash gave a better specific surface area of 0.4180 m2/g, while 0.0710 m2/g was obtained for unmodified fly-ash due to the disintegration of the outer layer which resulted in smaller particles, hence a larger surface area. EVA-FA composites were prepared from fly ash loadings of 3 to 20% and further characterised by XRD, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and SEM. XRD showed successful incorporation of fly ash into the EVA matrix through the appearance of fly ash diffraction peaks on the EVA-FA composite diffraction pattern. The incorporation of fly ash into the EVA matrix resulted in an improvement in the thermal stability of EVA, but did not have an effect on the melting temperature of the composites. However, a decrease in crystallisation temperature was observed. SEM micrographs revealed uniform dispersion of fly ash particles in the polymer matrix. Adsorption studies were performed using p-chlorophenol (PCP), 2,4,6-trichlorophenol (TCP) and p-nitrophenol (PNP) as model pollutants. An increase in adsorption efficiency of EVA-FA composites was observed as fly ash loading was increased from 3 to 10%. Between 10 and 20% fly-ash loading the removal efficiencies remained constant. The effect of contact time, pH and initial concentration was investigated. Polymer composites prepared from unmodified fly ash resulted in a higher adsorption capacity of phenols. The maximum uptake of PCP was 0.18 mg/g and that for TCP was 0.19 mg/g over a pH range of pH 3 to 5 and after contact time of 8 h. However, the adsorption capacity of 0.30 mg/g for PNP was achieved at pH 5 after a period of 10 h. Equilibrium adsorption data were evaluated using Langmuir and Freundlich adsorption isotherm models. There was no significant difference in the correlation coefficients (R2) from both models for the adsorption of PCP and TCP. However, the equilibrium adsorption data for PNP were better described by the Langmuir adsorption isotherm model. The kinetics data were analysed by pseudo-first-order and pseudo-second-order kinetic models. The pseudo-second-order kinetics model gave better correlation coefficients (> 0.9) for the adsorption of the phenols and the amount adsorbed at equilibrium was comparable to that calculated from the pseudo-second-order equation. Desorption studies were performed using NaOH solution with varying concentrations (0.1 to 0.3 M) and the studies revealed that PNP was the most difficult to be desorbed. Approximately 75% of PNP was recovered while 82% of PCP and 84% of TCP were recovered.
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Effect of monodispersed silica nanoparticles on colloid stability and adhesive properties of polyvinyl acetate-co-butyl acrylate processed through soapless emulsion polymerisation for coatings
- Authors: Zungu, Simphiwe
- Date: 2020
- Subjects: Adhesives , Colloids - Stability , Nanosilicon , Nanoparticles , Polymerization
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/458729 , uj:40756
- Description: Abstract: Adhesives (Paint and Glue) are widely used both in industrial and domestic space. In the market, an adhesive is as good as its colloid stability. In the South African industrial emulsion polymerisation space, colloid stability is achieved using special interfacial components such as surfactants and water-soluble polymers to avoid aggregation resulting in latex with low solid content. However, these materials tend to be relatively expensive compared to nanoparticles. We aim to substitute traditional expensive stabilisers with cheaper nanoparticles to reduce production costs of high-performance composites. Semi-batch emulsion polymerisation was used to synthesise polyvinyl-co-butyl acrylate emulsion since the process is most suitable for the monomers in use and it is an industrially viable process. We separated the project into three different phases to address the question of monomer ratio (phase 1), filler concentration and filler feeding (phase 2), as well as research prototype comparison with market products (phase 3). Rheometry, TEM, and contact angle as well as adhesive testing were regarded as the main characterisation techniques, supported by UV-Vis, TGA, FTIR, and solid content testing. Nanoparticles have also shown good improvement to adhesive properties of other co-polymer systems. Based on the literature that was considered, we believe that the PVAc-co-BA system has not been stabilised using nanoparticles; this application is the novelty of this project. , M.Tech. (Chemistry)
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- Authors: Zungu, Simphiwe
- Date: 2020
- Subjects: Adhesives , Colloids - Stability , Nanosilicon , Nanoparticles , Polymerization
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/458729 , uj:40756
- Description: Abstract: Adhesives (Paint and Glue) are widely used both in industrial and domestic space. In the market, an adhesive is as good as its colloid stability. In the South African industrial emulsion polymerisation space, colloid stability is achieved using special interfacial components such as surfactants and water-soluble polymers to avoid aggregation resulting in latex with low solid content. However, these materials tend to be relatively expensive compared to nanoparticles. We aim to substitute traditional expensive stabilisers with cheaper nanoparticles to reduce production costs of high-performance composites. Semi-batch emulsion polymerisation was used to synthesise polyvinyl-co-butyl acrylate emulsion since the process is most suitable for the monomers in use and it is an industrially viable process. We separated the project into three different phases to address the question of monomer ratio (phase 1), filler concentration and filler feeding (phase 2), as well as research prototype comparison with market products (phase 3). Rheometry, TEM, and contact angle as well as adhesive testing were regarded as the main characterisation techniques, supported by UV-Vis, TGA, FTIR, and solid content testing. Nanoparticles have also shown good improvement to adhesive properties of other co-polymer systems. Based on the literature that was considered, we believe that the PVAc-co-BA system has not been stabilised using nanoparticles; this application is the novelty of this project. , M.Tech. (Chemistry)
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