Design and fabrication of components of dye sensitised solar cells
- Authors: Msane, Gugu
- Date: 2019
- Subjects: Dye-sensitized solar cells
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/117106 , vital:34478
- Description: In recent decades there has been increasing global concern about the sustainability of our use of fossil fuels, which has led to increased interest in carbon–free sustainable renewable sources such as solar energy. Dye sensitized solar cells (DSSCs) are a cheap and clean technology that harnesses solar energy efficiently and convert it to electrical energy. A DSSC consists of a transparent working electrode coated with a dye-sensitized mesoporous film of nanocrystalline particles of semiconductor e.g. TiO2, an electrolyte containing a suitable redox couple and a platinized counter electrode. All the components of the DSSCs play vital roles in controlling the performance of the cell. The synergy of these components of the cells also needs to be investigated to optimise their interaction and create efficient and stable DSSCs. The information gathered from this investigation can give insight on how to improve the efficiencies of DSSCs. In this research study the semiconductor, transparent conducting layer and sensitizer were designed, optimized one at a time and their effect on the overall efficiency of the DSSCs studied. In this way it was easy to observe the effect of the individual components on the efficiency of the DSSCs. The conventional DSSCs usually use TiO2 as a semiconductor. In this research TiO2 was doped with cerium (Ce) to enhance its optical properties by reducing the band gap. A series of Ce-doped TiO2 with Ce content ranging from 0.1 to 1 mol % were successfully synthesized by an acid catalyzed sol-gel method, and their performance as the photoanodes of dye-sensitized solar cells (DSSCs) was investigated. Ce doping resulted in a red shift in the absorption of the TiO2 indicating narrowing of the band gap. The band gap first narrowed with increase in concentration of dopant up until 0.9 % dopant concentration. After this optimum doping concentration the band gap widened again. DFT calculations showed that Ce doping introduces Ce4f impurity states located just below the conduction band resulting in band gap narrowing. Ce content (0.9%) doped TiO2 photoanodes improved the performance of DSSCs with a conversion efficiency of 2.11% compared to 0,21% for the one with a pure TiO2 under 1 sun, AM1.5. Graphitised/TiO2 nanocomposites were also used a semiconductor to slow down recombination of electrons and holes in the cells. Electrophoretic deposition (EPD) was used to deposit graphitised/TiO2 nanocomposites onto an FTO electrode for application as photoelectrode in dye-sensitized solar cells (DSSCs). An enhanced power conversion efficiency (PCE) of 2.25% was observed for the 0.5 wt% graphene oxide/TiO2 (GO/TiO2) based DSSC which was higher than that of the conversion efficiency of pure TiO2 nanoparticles (i.e. 0.52%). Graphene oxide led to high migration of photoinduced electrons to the conduction band of the collection electrode and inhibition of charge carriers recombination resulting in enhanced photoconversion efficiency. A GO content above 0.5 % resulted in a reduced transparency leading to a decrease in the PCE. 0.5 wt % GO/0.9 Ce–TiO2 Ce based DSSC showed a slightly enhanced efficiency of 2.45%. 0.5 rGO/TiO2 based DSSCs had a high efficiency than 0.5 rGO/TiO2 due to improved conductivity of rGO nanosheets and suppressed recombination of charge carriers. To cut down DSSC production costs a silver wire network transparent conducting polyethylene electrodes was fabricated and used as an indium tin oxide (ITO) alternative substrates in DSSCs. The transmittance of the AgNW network was 82 % which is comparable to ITO substrates. Titanium oxide (TiO2) films on the AgWN/PET substrates were obtained using the electrophoresis method. These substrates were sensitised and used to fabricate a dye sensitised solar cell. From the measured current–voltage or I-V characteristic under AM1.5 illumination of the formed DSSC using AgWN substrates, an open circuit voltage (VOC) of 0.377 V, a short circuit current (ISC) of 0.0067 mA and a fill factor (FF) 25.7 % with an efficiency of 0.00862 % were obtained from a cell of 0.075 cm2 working area. The stability of the cell improved when a room temperature ionic liquid electrolyte was used. Gold nanofiber transparent electrodes were also prepared by the electrospinning techniques and used as an alternative to indium tin oxides substrates. Transparent conducting gold nanofiber (AuNF) transparent conducting electrodes were fabricated by using a low–cost electrospinning process and used as photoelectrodes for DSSCs. TiO2 was deposited on these electrodes by using an electrospray method. DSSC using AuNF as transparent electrodes had a power efficiency of 0.52%, compared to devices made with FTO electrodes (1.48%). DSSCs. Versatile dyes with increased spectral response, stability and suppressed recombination of holes and electrons were synthesised and used as a sensitizers for DSSCs. The boron dipyrrin (BODIPY) chromophore was combined with a carboxy coumarin moiety to create donor–acceptor (dyad) system dyes. Regenerative dyad dyes were formed through covalently linking a porphyrin chromophore to a manganese(II) ion through bridging ligands. These chromophores and also porphyrin and BODIPY dyes were used as sensitisers for DSSCs. The regenerative dye based DSSCs showed a photoconversion efficiency of 4.09% which was higher than the efficiency of the parent porphyrin (2.57%). The enhanced efficiency was attributed to the manganese bypridine cluster in the ZnTPP–Mn bpy supramolecule which acted as an electron donor to the photo-oxidized porphyrin continuously regenerating the porphyrin and preventing its decay.
- Full Text:
- Date Issued: 2019
- Authors: Msane, Gugu
- Date: 2019
- Subjects: Dye-sensitized solar cells
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/117106 , vital:34478
- Description: In recent decades there has been increasing global concern about the sustainability of our use of fossil fuels, which has led to increased interest in carbon–free sustainable renewable sources such as solar energy. Dye sensitized solar cells (DSSCs) are a cheap and clean technology that harnesses solar energy efficiently and convert it to electrical energy. A DSSC consists of a transparent working electrode coated with a dye-sensitized mesoporous film of nanocrystalline particles of semiconductor e.g. TiO2, an electrolyte containing a suitable redox couple and a platinized counter electrode. All the components of the DSSCs play vital roles in controlling the performance of the cell. The synergy of these components of the cells also needs to be investigated to optimise their interaction and create efficient and stable DSSCs. The information gathered from this investigation can give insight on how to improve the efficiencies of DSSCs. In this research study the semiconductor, transparent conducting layer and sensitizer were designed, optimized one at a time and their effect on the overall efficiency of the DSSCs studied. In this way it was easy to observe the effect of the individual components on the efficiency of the DSSCs. The conventional DSSCs usually use TiO2 as a semiconductor. In this research TiO2 was doped with cerium (Ce) to enhance its optical properties by reducing the band gap. A series of Ce-doped TiO2 with Ce content ranging from 0.1 to 1 mol % were successfully synthesized by an acid catalyzed sol-gel method, and their performance as the photoanodes of dye-sensitized solar cells (DSSCs) was investigated. Ce doping resulted in a red shift in the absorption of the TiO2 indicating narrowing of the band gap. The band gap first narrowed with increase in concentration of dopant up until 0.9 % dopant concentration. After this optimum doping concentration the band gap widened again. DFT calculations showed that Ce doping introduces Ce4f impurity states located just below the conduction band resulting in band gap narrowing. Ce content (0.9%) doped TiO2 photoanodes improved the performance of DSSCs with a conversion efficiency of 2.11% compared to 0,21% for the one with a pure TiO2 under 1 sun, AM1.5. Graphitised/TiO2 nanocomposites were also used a semiconductor to slow down recombination of electrons and holes in the cells. Electrophoretic deposition (EPD) was used to deposit graphitised/TiO2 nanocomposites onto an FTO electrode for application as photoelectrode in dye-sensitized solar cells (DSSCs). An enhanced power conversion efficiency (PCE) of 2.25% was observed for the 0.5 wt% graphene oxide/TiO2 (GO/TiO2) based DSSC which was higher than that of the conversion efficiency of pure TiO2 nanoparticles (i.e. 0.52%). Graphene oxide led to high migration of photoinduced electrons to the conduction band of the collection electrode and inhibition of charge carriers recombination resulting in enhanced photoconversion efficiency. A GO content above 0.5 % resulted in a reduced transparency leading to a decrease in the PCE. 0.5 wt % GO/0.9 Ce–TiO2 Ce based DSSC showed a slightly enhanced efficiency of 2.45%. 0.5 rGO/TiO2 based DSSCs had a high efficiency than 0.5 rGO/TiO2 due to improved conductivity of rGO nanosheets and suppressed recombination of charge carriers. To cut down DSSC production costs a silver wire network transparent conducting polyethylene electrodes was fabricated and used as an indium tin oxide (ITO) alternative substrates in DSSCs. The transmittance of the AgNW network was 82 % which is comparable to ITO substrates. Titanium oxide (TiO2) films on the AgWN/PET substrates were obtained using the electrophoresis method. These substrates were sensitised and used to fabricate a dye sensitised solar cell. From the measured current–voltage or I-V characteristic under AM1.5 illumination of the formed DSSC using AgWN substrates, an open circuit voltage (VOC) of 0.377 V, a short circuit current (ISC) of 0.0067 mA and a fill factor (FF) 25.7 % with an efficiency of 0.00862 % were obtained from a cell of 0.075 cm2 working area. The stability of the cell improved when a room temperature ionic liquid electrolyte was used. Gold nanofiber transparent electrodes were also prepared by the electrospinning techniques and used as an alternative to indium tin oxides substrates. Transparent conducting gold nanofiber (AuNF) transparent conducting electrodes were fabricated by using a low–cost electrospinning process and used as photoelectrodes for DSSCs. TiO2 was deposited on these electrodes by using an electrospray method. DSSC using AuNF as transparent electrodes had a power efficiency of 0.52%, compared to devices made with FTO electrodes (1.48%). DSSCs. Versatile dyes with increased spectral response, stability and suppressed recombination of holes and electrons were synthesised and used as a sensitizers for DSSCs. The boron dipyrrin (BODIPY) chromophore was combined with a carboxy coumarin moiety to create donor–acceptor (dyad) system dyes. Regenerative dyad dyes were formed through covalently linking a porphyrin chromophore to a manganese(II) ion through bridging ligands. These chromophores and also porphyrin and BODIPY dyes were used as sensitisers for DSSCs. The regenerative dye based DSSCs showed a photoconversion efficiency of 4.09% which was higher than the efficiency of the parent porphyrin (2.57%). The enhanced efficiency was attributed to the manganese bypridine cluster in the ZnTPP–Mn bpy supramolecule which acted as an electron donor to the photo-oxidized porphyrin continuously regenerating the porphyrin and preventing its decay.
- Full Text:
- Date Issued: 2019
Design of metal ion-selective reagents for recovery of precious metals
- Authors: Moleko-Boyce, Pulleng
- Date: 2019
- Subjects: Bioinorganic chemistry , Metal complexes Speciation (Chemistry)
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/42510 , vital:36664
- Description: The study is divided into two sections; namely, (1) the design of rhodium(III) specific chelating ligands (tridentate bis-benzimidazole derivatives), and (2) the development of iridium(IV)-specific quaternary diammonium cations with electron donating and electron withdrawing groups. Bis-benzimidazole chelating ligands used were bis((1H-benzimidazol-2-yl)methyl)amine (NNN1), bis((1H-benzimidazol-2-yl)ethyl)amine (NNN2), bis((1H-benzimidazol-2-yl)methyl)sulfide (NSN1) and bis((1H-benzimidazol-2-yl)ethyl)sulfide (NSN2). Quaternary diammonium cations used were tetramethylbenzyl-1,10-diammonium chloride (QuatDMDAMeBnz), tetrabenzyl-1,10-diammonium chloride (QuatDMDABnz), tetratrifluoromethylbenzyl-1,10-diammonium chloride (QuatDMDACF3Bnz) and tetranitrobenzyl-1,10-diammonium chloride (QuatDMDANO2Bnz). For both studies, polyvinylbenzylchloride (PVBC) nanofibers were used as support material. The PVBC nanofibers which were functionalised with bis-benzimidazole derivatives and quaternary diammonium cations, respectively, were investigated for the selectivity for Rh(III) over Ir(III), Pt(II), Pd(II) and Ni(II), and for separation of Ir(IV) from Rh(III), respectively. The sorbent materials were characterised by FTIR, SEM, BET surface area, TGA, EDS and elemental analysis, and the results showed that the functionalization of the sorbent materials was successful.The efficiency of bis-benzimidazole derivatives and quaternary diammonium cations, respectively, were investigated in a column study under dynamic flow adsorption conditions. The adsorption kinetics and isotherms were investigated under batch conditions and fitted on pseudo-first-order and pseudo-second-order model, and Freundlich and Langmuir isotherm, respectively. It was observed that the bis-benzimidazole derivatives showed uptake of [RhCl3(H2O)3], and the loading capacities were observed in the following order; NSN1 (181.06 mg/g) > NSN2 (148.55 mg/g) > NNN1 (131.88 mg/g) > NNN2 (75.87 mg/g). The bis-benzimidazole derivatives preference for metal ions was further investigated with a multi-element solution containing Rh(III), Ir(III), Pt(II), Pd(II) and Ni(II). The bis-benzimidazole derivatives showed the following order of loading capacity: NSN1 (47.28 mg/g) > NSN2 (23.89 mg/g) > NNN1 (17.47 mg/g) > NNN2 (14.91 mg/g) for Rh(III); NSN2 (10.64 mg/g) > NNN2 (6.84 mg/g) > NSN1 (5.74 mg/g) > NNN1 (5.02 mg/g) for Ir(III); NNN2 (33.96 mg/g) > NSN1 (30.95 mg/g) > NSN2 (19.95 mg/g) > NNN1 (14.92 mg/g) for Pt(II); NNN1 (47.94 mg/g) > NNN2 (28.90 mg/g) > NSN1 (16.22 mg/g) > NSN2 (15.83 mg/g) for Pd(II). Bis-benzimidazole derivatives showed no uptake of nickel(II) under these conditions. It was observed the ligand-selectivity order for Rh(III) was similar in both single-element and multi-element studies. This order showed that the bis-benzimidazoles containing a sulfur atom showed a high preference for rhodium(III) compared to Pt(II) which had a high preference for NNN2 as well as Pd(II) which had a high preference for NNN1. Ir(III) generally had a lower preference for the ligands presumably due to its higher kinetic inertness compared with Rh(III). Column sorption of [IrCl6]2- and [RhCl5(H2O)]2- on nanofibers functionalized with diammonium cations was carried out and the loading capacities of [IrCl6]2- were obtained. [RhCl5(H2O)]2- was not adsorbed by the sorbent materials while [IrCl6]2- was loaded onto the column. The loading capacities of [IrCl6]2- with the quaternary diammonium sorbent materials increased in the order of F-QuatDMDAMeBnz (60.29 mg/g) < F-QuatDMDABnz (67.61 mg/g) < F-QuatDMDACF3Bnz (107.59 mg/g) < F-QuatDMDANO2Bnz (140.47 mg/g). The loading capacity for Ir(IV) with quaternary diammonium cationic nanofibers increased with an increase in the electron-withdrawing nature of the quaternizing group. The charge delocalizing ability of the nitrobenzyl group resulted in the best interaction of the diammonium cation with [IrCl6]2-. Batch equilibrium studies were carried out to assess the efficiency of bis-benzimidazole chelating derivatives as adsorbents using a multi-metal solution (Rh(III), Ir(III), Pt(II), Pd(II) and Ni(II)) in 0.5 M HCl. The efficiency of the quaternary diammonium cations was tested using a binary metal solution (Ir(IV) and Rh(III)) in 6 M HCl. The isothermal batch adsorption studies of a multi-metal solution with bis-benzimidazoles derivatives fitted the Langmuir isotherm model which confirmed monolayer adsorption onto a homogeneous surface. The Langmuir isotherm parameter (qe (mg/g)), using functionalized nanofibers, showed the order of NNN2 (128.21 mg/g) > NSN1 (99.01 mg/g) > NSN2 (91.74 mg/g) > NNN1 (84.03 mg/g) for Pt(II); NNN1 (66.23 mg/g) > NNN2 (5.89 mg/g) > NSN1 (1.40 mg/g) > NSN2 (0.59 mg/g) for Pd(II); NSN2 (10.64 mg/g) > NNN2 (6.84 mg/g) > NSN1 (5.74 mg/g) > NNN1 (5.02 mg/g) for Ir(III); NSN1 (140.85 mg/g) > NSN2 (109.89 mg/g) > NNN1 (104.17 mg/g) > NNN2 (91.74 mg/g) for Rh(III). The pseudo-first-order kinetics model was found to be the best fit to describe the adsorption kinetics of all metal ions onto all the sorbent materials. K1 (min-1) value in pseudo-first-order kinetics showed the same order of adsorption as observed in the Langmuir isotherms. The isothermal batch adsorption studies of [IrCl6]2- and [RhCl5(H2O)]2- with quaternary diammonium cations fitted the Freundlich isotherm model and confirmed to be effective for multiple-layered adsorption onto a heterogeneous surface. The Freundlich isotherm parameter (kf (mg/g)) using functionalized quaternary diammonium cationic nanofibers increased in the order of F-QuatDMDANO2Bnz (794.33 mg/g) > F-QuatDMDACF3Bnz (185.35 mg/g) > F-QuatDMDABnz (156.32 mg/g) > F-QuatDMDAMeBnz (112.46 mg/g) for Ir(IV) uptake. F-QuatDMDANO2Bnz resin showed the highest adsorption than that of F-QuatDMDAMeBnz, F-QuatDMDABnz and F-QuatDMDACF3Bnz and this order is similar to what was observed in column studies. The quaternary diammonium cations were shown to have the highest adsorption capacity for Ir(IV) compared with Rh(III). The adsorption of Rh(III) was also observed to increase in the order of F-QuatDMDANO2Bnz (177.83 mg/g) > F-QuatDMDACF3Bnz (40.37 mg/g) > F-QuatDMDABnz (36.98 mg/g) > F-QuatDMDAMeBnz (12.71 mg/g). The pseudo-second-order kinetic model was found to be the best fit to describe the adsorption kinetics of both metal ions onto all the sorbent materials. K2 (g.mg-1min-1) value in pseudo-second-order kinetics showed the same order of adsorption as observed in the Freundlich isotherms. The adsorption studies showed adsorption takes place via chemisorption process. This thesis presents PGMs and iridium-specific materials that could be applied in solutions of secondary PGMs sources containing rhodium, platinum and palladium with bis-benzimidazoles as well as in feed solutions from ore processing with diammonium cations for iridium recovery.
- Full Text:
- Date Issued: 2019
- Authors: Moleko-Boyce, Pulleng
- Date: 2019
- Subjects: Bioinorganic chemistry , Metal complexes Speciation (Chemistry)
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/42510 , vital:36664
- Description: The study is divided into two sections; namely, (1) the design of rhodium(III) specific chelating ligands (tridentate bis-benzimidazole derivatives), and (2) the development of iridium(IV)-specific quaternary diammonium cations with electron donating and electron withdrawing groups. Bis-benzimidazole chelating ligands used were bis((1H-benzimidazol-2-yl)methyl)amine (NNN1), bis((1H-benzimidazol-2-yl)ethyl)amine (NNN2), bis((1H-benzimidazol-2-yl)methyl)sulfide (NSN1) and bis((1H-benzimidazol-2-yl)ethyl)sulfide (NSN2). Quaternary diammonium cations used were tetramethylbenzyl-1,10-diammonium chloride (QuatDMDAMeBnz), tetrabenzyl-1,10-diammonium chloride (QuatDMDABnz), tetratrifluoromethylbenzyl-1,10-diammonium chloride (QuatDMDACF3Bnz) and tetranitrobenzyl-1,10-diammonium chloride (QuatDMDANO2Bnz). For both studies, polyvinylbenzylchloride (PVBC) nanofibers were used as support material. The PVBC nanofibers which were functionalised with bis-benzimidazole derivatives and quaternary diammonium cations, respectively, were investigated for the selectivity for Rh(III) over Ir(III), Pt(II), Pd(II) and Ni(II), and for separation of Ir(IV) from Rh(III), respectively. The sorbent materials were characterised by FTIR, SEM, BET surface area, TGA, EDS and elemental analysis, and the results showed that the functionalization of the sorbent materials was successful.The efficiency of bis-benzimidazole derivatives and quaternary diammonium cations, respectively, were investigated in a column study under dynamic flow adsorption conditions. The adsorption kinetics and isotherms were investigated under batch conditions and fitted on pseudo-first-order and pseudo-second-order model, and Freundlich and Langmuir isotherm, respectively. It was observed that the bis-benzimidazole derivatives showed uptake of [RhCl3(H2O)3], and the loading capacities were observed in the following order; NSN1 (181.06 mg/g) > NSN2 (148.55 mg/g) > NNN1 (131.88 mg/g) > NNN2 (75.87 mg/g). The bis-benzimidazole derivatives preference for metal ions was further investigated with a multi-element solution containing Rh(III), Ir(III), Pt(II), Pd(II) and Ni(II). The bis-benzimidazole derivatives showed the following order of loading capacity: NSN1 (47.28 mg/g) > NSN2 (23.89 mg/g) > NNN1 (17.47 mg/g) > NNN2 (14.91 mg/g) for Rh(III); NSN2 (10.64 mg/g) > NNN2 (6.84 mg/g) > NSN1 (5.74 mg/g) > NNN1 (5.02 mg/g) for Ir(III); NNN2 (33.96 mg/g) > NSN1 (30.95 mg/g) > NSN2 (19.95 mg/g) > NNN1 (14.92 mg/g) for Pt(II); NNN1 (47.94 mg/g) > NNN2 (28.90 mg/g) > NSN1 (16.22 mg/g) > NSN2 (15.83 mg/g) for Pd(II). Bis-benzimidazole derivatives showed no uptake of nickel(II) under these conditions. It was observed the ligand-selectivity order for Rh(III) was similar in both single-element and multi-element studies. This order showed that the bis-benzimidazoles containing a sulfur atom showed a high preference for rhodium(III) compared to Pt(II) which had a high preference for NNN2 as well as Pd(II) which had a high preference for NNN1. Ir(III) generally had a lower preference for the ligands presumably due to its higher kinetic inertness compared with Rh(III). Column sorption of [IrCl6]2- and [RhCl5(H2O)]2- on nanofibers functionalized with diammonium cations was carried out and the loading capacities of [IrCl6]2- were obtained. [RhCl5(H2O)]2- was not adsorbed by the sorbent materials while [IrCl6]2- was loaded onto the column. The loading capacities of [IrCl6]2- with the quaternary diammonium sorbent materials increased in the order of F-QuatDMDAMeBnz (60.29 mg/g) < F-QuatDMDABnz (67.61 mg/g) < F-QuatDMDACF3Bnz (107.59 mg/g) < F-QuatDMDANO2Bnz (140.47 mg/g). The loading capacity for Ir(IV) with quaternary diammonium cationic nanofibers increased with an increase in the electron-withdrawing nature of the quaternizing group. The charge delocalizing ability of the nitrobenzyl group resulted in the best interaction of the diammonium cation with [IrCl6]2-. Batch equilibrium studies were carried out to assess the efficiency of bis-benzimidazole chelating derivatives as adsorbents using a multi-metal solution (Rh(III), Ir(III), Pt(II), Pd(II) and Ni(II)) in 0.5 M HCl. The efficiency of the quaternary diammonium cations was tested using a binary metal solution (Ir(IV) and Rh(III)) in 6 M HCl. The isothermal batch adsorption studies of a multi-metal solution with bis-benzimidazoles derivatives fitted the Langmuir isotherm model which confirmed monolayer adsorption onto a homogeneous surface. The Langmuir isotherm parameter (qe (mg/g)), using functionalized nanofibers, showed the order of NNN2 (128.21 mg/g) > NSN1 (99.01 mg/g) > NSN2 (91.74 mg/g) > NNN1 (84.03 mg/g) for Pt(II); NNN1 (66.23 mg/g) > NNN2 (5.89 mg/g) > NSN1 (1.40 mg/g) > NSN2 (0.59 mg/g) for Pd(II); NSN2 (10.64 mg/g) > NNN2 (6.84 mg/g) > NSN1 (5.74 mg/g) > NNN1 (5.02 mg/g) for Ir(III); NSN1 (140.85 mg/g) > NSN2 (109.89 mg/g) > NNN1 (104.17 mg/g) > NNN2 (91.74 mg/g) for Rh(III). The pseudo-first-order kinetics model was found to be the best fit to describe the adsorption kinetics of all metal ions onto all the sorbent materials. K1 (min-1) value in pseudo-first-order kinetics showed the same order of adsorption as observed in the Langmuir isotherms. The isothermal batch adsorption studies of [IrCl6]2- and [RhCl5(H2O)]2- with quaternary diammonium cations fitted the Freundlich isotherm model and confirmed to be effective for multiple-layered adsorption onto a heterogeneous surface. The Freundlich isotherm parameter (kf (mg/g)) using functionalized quaternary diammonium cationic nanofibers increased in the order of F-QuatDMDANO2Bnz (794.33 mg/g) > F-QuatDMDACF3Bnz (185.35 mg/g) > F-QuatDMDABnz (156.32 mg/g) > F-QuatDMDAMeBnz (112.46 mg/g) for Ir(IV) uptake. F-QuatDMDANO2Bnz resin showed the highest adsorption than that of F-QuatDMDAMeBnz, F-QuatDMDABnz and F-QuatDMDACF3Bnz and this order is similar to what was observed in column studies. The quaternary diammonium cations were shown to have the highest adsorption capacity for Ir(IV) compared with Rh(III). The adsorption of Rh(III) was also observed to increase in the order of F-QuatDMDANO2Bnz (177.83 mg/g) > F-QuatDMDACF3Bnz (40.37 mg/g) > F-QuatDMDABnz (36.98 mg/g) > F-QuatDMDAMeBnz (12.71 mg/g). The pseudo-second-order kinetic model was found to be the best fit to describe the adsorption kinetics of both metal ions onto all the sorbent materials. K2 (g.mg-1min-1) value in pseudo-second-order kinetics showed the same order of adsorption as observed in the Freundlich isotherms. The adsorption studies showed adsorption takes place via chemisorption process. This thesis presents PGMs and iridium-specific materials that could be applied in solutions of secondary PGMs sources containing rhodium, platinum and palladium with bis-benzimidazoles as well as in feed solutions from ore processing with diammonium cations for iridium recovery.
- Full Text:
- Date Issued: 2019
Design, evaluation and optimization of taste masked clarithromycin powder
- Ntemi, Pascal V, Walker, Roderick B, Khamanga, Sandile M
- Authors: Ntemi, Pascal V , Walker, Roderick B , Khamanga, Sandile M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183503 , vital:44001 , xlink:href="https://doi.org/10.1691/ph.2019.8116"
- Description: Clarithromycin (CLA) is an extremely bitter macrolide antibiotic used to treat paediatric and adult infections. The bitter taste affects patient adherence and may compromise therapy. This research developed a taste masked CLA resinate using Indion® 234, a weak acidic cation exchange resin. The factors affecting formation of the CLA-resin complex were assessed. Design of experiments was used to optimize response while evaluating input variables such as temperature, CLA-resin ratio,stirring time and pH. CLA loading efficiency was determined spectrophotometrically and CLA release using USP Apparatus II. Differential Scanning Calorimetry (DSC), Scanning Electron Microscop (SEM), Fourier Transform Infrared (FT-IR) Spectroscopy and X-ray Diffraction (XRD) were used to confirm complex formation. A spectrophotometric method was used to assess taste evaluation. The optimum CLA-resin ratio, temperature, and stirring time were 1:4, 80 °C, 3 hours, respectively, at pH 8. Characterization techniques revealed that CLA was crystalline and the complex amorphous in nature. FT-IR spectra of resinate revealed the absence of resonance due to the tertiary amine functional group that is responsible for the bitter taste of CLA. CLA was stable in simulated salivary fluid and was released within 3 hours in gastric fluid. All CLAresin batches revealed complete taste masking. Taste analysis highlighted the improvement of taste masking properties of the resinate as the CLA to resin ratio, increased.
- Full Text:
- Date Issued: 2019
- Authors: Ntemi, Pascal V , Walker, Roderick B , Khamanga, Sandile M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183503 , vital:44001 , xlink:href="https://doi.org/10.1691/ph.2019.8116"
- Description: Clarithromycin (CLA) is an extremely bitter macrolide antibiotic used to treat paediatric and adult infections. The bitter taste affects patient adherence and may compromise therapy. This research developed a taste masked CLA resinate using Indion® 234, a weak acidic cation exchange resin. The factors affecting formation of the CLA-resin complex were assessed. Design of experiments was used to optimize response while evaluating input variables such as temperature, CLA-resin ratio,stirring time and pH. CLA loading efficiency was determined spectrophotometrically and CLA release using USP Apparatus II. Differential Scanning Calorimetry (DSC), Scanning Electron Microscop (SEM), Fourier Transform Infrared (FT-IR) Spectroscopy and X-ray Diffraction (XRD) were used to confirm complex formation. A spectrophotometric method was used to assess taste evaluation. The optimum CLA-resin ratio, temperature, and stirring time were 1:4, 80 °C, 3 hours, respectively, at pH 8. Characterization techniques revealed that CLA was crystalline and the complex amorphous in nature. FT-IR spectra of resinate revealed the absence of resonance due to the tertiary amine functional group that is responsible for the bitter taste of CLA. CLA was stable in simulated salivary fluid and was released within 3 hours in gastric fluid. All CLAresin batches revealed complete taste masking. Taste analysis highlighted the improvement of taste masking properties of the resinate as the CLA to resin ratio, increased.
- Full Text:
- Date Issued: 2019
Determinants of a competitive bunkering service: a South African model
- Authors: Mdlalose, Silindile
- Date: 2019
- Subjects: Ships -- Fuel -- South Africa , Oil transfer operations -- South Africa Coastal water transportation -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/41471 , vital:36487
- Description: South Africa is one of the best strategically positioned countries in the world in terms of trade routes from the west to the east. According to the Operation Phakisa research team, about 13 000 vessels visit South African ports annually and nearly 30 000 vessels sail along the South African coast yearly. Yet, less than ten percent of visiting vessels replenish bunkers in the country. This is a lost business opportunity for the South African bunker industry. South Africa has struggled to attract and maintain bunker business for some time. The aim of this study is to establish what the determinants of a competitive bunker industry are. A positivism philosophy is adopted to conduct the study. Using information gathered through a literature review, a conceptualised model for a competitive bunker industry is formulated. The model claims that there is a positive relationship between bunker industry competitiveness and eight independent variables identified in literature. The eight independent variables identified are (i) Bunker Fuel, (ii) Location, (iii) Port Accessibility, (iv) Rules and Regulations, (v) Service, (vi) Infrastructure, (vii) Cost of Service and (viii) Human Capital. A survey is conducted using a questionnaire. The questionnaire was generated specifically to collect primary data. There are 104 usable responses received back from the survey. The response data are used for quantitative data analysis. Quantitative data analysis methods like the EFA, Cronbach’s alpha, one sample t-test and Pearson Moment Correlations’ analysis are employed to test the conceptualised model. Findings show that independent variables (i) Service, (ii) Infrastructure, (iii) Port Accessibility, (iv) Location and (v) Bunker Industry Competitiveness (the independent variable) are contributors to bunker industry competitiveness (dependent variable). The results indicate that to achieve bunker industry competitiveness, the best approach will be to employ a collective approach that will simultaneously consider all of the literature-identified variables. All of the variables will have to be considered and aligned when the strategy for a competitive bunker industry is created.
- Full Text:
- Date Issued: 2019
- Authors: Mdlalose, Silindile
- Date: 2019
- Subjects: Ships -- Fuel -- South Africa , Oil transfer operations -- South Africa Coastal water transportation -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/41471 , vital:36487
- Description: South Africa is one of the best strategically positioned countries in the world in terms of trade routes from the west to the east. According to the Operation Phakisa research team, about 13 000 vessels visit South African ports annually and nearly 30 000 vessels sail along the South African coast yearly. Yet, less than ten percent of visiting vessels replenish bunkers in the country. This is a lost business opportunity for the South African bunker industry. South Africa has struggled to attract and maintain bunker business for some time. The aim of this study is to establish what the determinants of a competitive bunker industry are. A positivism philosophy is adopted to conduct the study. Using information gathered through a literature review, a conceptualised model for a competitive bunker industry is formulated. The model claims that there is a positive relationship between bunker industry competitiveness and eight independent variables identified in literature. The eight independent variables identified are (i) Bunker Fuel, (ii) Location, (iii) Port Accessibility, (iv) Rules and Regulations, (v) Service, (vi) Infrastructure, (vii) Cost of Service and (viii) Human Capital. A survey is conducted using a questionnaire. The questionnaire was generated specifically to collect primary data. There are 104 usable responses received back from the survey. The response data are used for quantitative data analysis. Quantitative data analysis methods like the EFA, Cronbach’s alpha, one sample t-test and Pearson Moment Correlations’ analysis are employed to test the conceptualised model. Findings show that independent variables (i) Service, (ii) Infrastructure, (iii) Port Accessibility, (iv) Location and (v) Bunker Industry Competitiveness (the independent variable) are contributors to bunker industry competitiveness (dependent variable). The results indicate that to achieve bunker industry competitiveness, the best approach will be to employ a collective approach that will simultaneously consider all of the literature-identified variables. All of the variables will have to be considered and aligned when the strategy for a competitive bunker industry is created.
- Full Text:
- Date Issued: 2019
Determinants of consumerisation of information technology and its effect on employee performance
- Authors: Khayundi, Hilda
- Date: 2019
- Subjects: Information technology -- Economic aspect Organizational effectiveness
- Language: English
- Type: Thesis , Masters , MCom (Business Management)
- Identifier: http://hdl.handle.net/10353/16906 , vital:40784
- Description: The ubiquitous nature of personally technological advanced devices and applications has engendered various predictions for the current employee at the workplace. With the introduction and adoption of mobile phones, tablets, laptops and even software, organisations are gradually allowing employees to utilise their personal mobile devices at the office to accomplish their tasks. This has led to the term Consumerisation of Information Technology (CIT) or IT consumerisation. The purpose of this study was to investigate the determinants of consumerisation of IT and its effect on job performance of staff at an institution of higher learning. This study used a theoretical framework - The Unified Theory of Acceptance and Usage of Technology – to find out if indeed consumerisation of IT has an effect on job performance. An online questionnaire was sent to the university’s staff email and a total of 230 responses were recorded. The study used a quantitative research approach. The Statistical Package for Social Sciences (SPSS) software was used for data analysis to test the hypotheses. Tests such as the multiple linear regression, factor analysis, correlations, ANOVA and t-tests were used to test the hypotheses. The findings of the study showed that there is a relationship between the determinants of consumerisation of IT and their effect on job performance at the workplace. These determinants are performance expectancy, social influence and facilitating conditions. Effort expectancy was the only factor that did not have an effect on consumerisation of IT. As such the study suggested that institutions and organisations to take note of the technological development of devices that can help employees improve their productivity. However, this should be treated with caution as there are also negative effects such as technostress and cyberloafing which may be associated with the advent of consumerisation of IT, therefore it should be a gradual process in order to see the benefits.
- Full Text:
- Date Issued: 2019
- Authors: Khayundi, Hilda
- Date: 2019
- Subjects: Information technology -- Economic aspect Organizational effectiveness
- Language: English
- Type: Thesis , Masters , MCom (Business Management)
- Identifier: http://hdl.handle.net/10353/16906 , vital:40784
- Description: The ubiquitous nature of personally technological advanced devices and applications has engendered various predictions for the current employee at the workplace. With the introduction and adoption of mobile phones, tablets, laptops and even software, organisations are gradually allowing employees to utilise their personal mobile devices at the office to accomplish their tasks. This has led to the term Consumerisation of Information Technology (CIT) or IT consumerisation. The purpose of this study was to investigate the determinants of consumerisation of IT and its effect on job performance of staff at an institution of higher learning. This study used a theoretical framework - The Unified Theory of Acceptance and Usage of Technology – to find out if indeed consumerisation of IT has an effect on job performance. An online questionnaire was sent to the university’s staff email and a total of 230 responses were recorded. The study used a quantitative research approach. The Statistical Package for Social Sciences (SPSS) software was used for data analysis to test the hypotheses. Tests such as the multiple linear regression, factor analysis, correlations, ANOVA and t-tests were used to test the hypotheses. The findings of the study showed that there is a relationship between the determinants of consumerisation of IT and their effect on job performance at the workplace. These determinants are performance expectancy, social influence and facilitating conditions. Effort expectancy was the only factor that did not have an effect on consumerisation of IT. As such the study suggested that institutions and organisations to take note of the technological development of devices that can help employees improve their productivity. However, this should be treated with caution as there are also negative effects such as technostress and cyberloafing which may be associated with the advent of consumerisation of IT, therefore it should be a gradual process in order to see the benefits.
- Full Text:
- Date Issued: 2019
Determination of social, environmental and economic benefits for community participation in forestry in Mpumalanga, South Africa
- Long, Leo Searle, Chirwa, Paxie
- Authors: Long, Leo Searle , Chirwa, Paxie
- Date: 2019
- Subjects: Forests and forestry -- South Africa -- Mpumalanga
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34339 , vital:33307
- Description: Rural communities living adjacent to commercial forestry operations are often affected by numerous negative social issues such as poverty, unemployment, poor healthcare, and limited infrastructure, amongst others. In excess of 61% of forestry land managed by the state owned SAFCOL SOC Ltd is under land claim, as part of the Restitution of Land Rights Act (Act 22 of 1994). It is therefore necessary for forest companies to seek active means of engaging and partnering with these communities through a participatory forest management (PFM) approach. This study explored the sustainable (social, environmental and economic), benefits of such an approach as perceived (experienced) by these local rural communities, and specifically land claimants. The study was conducted in communities adjacent to SAFCOL plantations in the Mpumalanga Province of South Africa. Data were collected between May and June 2017 by means of a structured questionnaire. Surveys were conducted on 46 households within the identified communities so as to verify and evaluate perceived benefits in terms of forest products, ecosystem services and amenities/services/infrastructure provided by SAFCOL and the broader forest industry. The results indicated that these communities recognize and obtain numerous social, environmental and economic benefits from the forest including Non-Timber Forest Products (NTFPs) such as firewood; forest provisioning ecosystem services (FPESs) such as improved water quality; and more metaphysical benefits such as access to gravesites and the protection of traditions and customs. These benefits have the ability to improve the social well-being, economic independence, and the quality of environmental services obtained by the associated communities. It was however found that the utilization of these benefits was widely differentiated according to gender and land claimant status. Whilst males and females largely benefitted equally, there was a distinct benefit preference between genders for different NTFPs. For example males showed preference for the collection of building material, bush meat and for livestock husbandry, whilst females showed preference for the collection of firewood, medicinal plants and fruit, amongst others. Similarly, it was found that overall, non-land claimants benefited more than land claimants. Reasons for this are primarily due to the increased distance with which the land claimants live from the forest resource when compared to non-land claimants. The empirical value of the data produced through this study will be invaluable in negotiations with the land claimant communities on land settlement agreements, joint venture proposals, including Participatory Forest Management, and future land tenure. Through such inclusivity and vested interest in the sustainable management of the forests, corporate risk is reduced and community/land claimant relationships are reinforced. Such Participatory Forest Management arrangements are key to ensuring the longevity and resilience to the forest sector post-transfer of claimed land.
- Full Text:
- Date Issued: 2019
- Authors: Long, Leo Searle , Chirwa, Paxie
- Date: 2019
- Subjects: Forests and forestry -- South Africa -- Mpumalanga
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34339 , vital:33307
- Description: Rural communities living adjacent to commercial forestry operations are often affected by numerous negative social issues such as poverty, unemployment, poor healthcare, and limited infrastructure, amongst others. In excess of 61% of forestry land managed by the state owned SAFCOL SOC Ltd is under land claim, as part of the Restitution of Land Rights Act (Act 22 of 1994). It is therefore necessary for forest companies to seek active means of engaging and partnering with these communities through a participatory forest management (PFM) approach. This study explored the sustainable (social, environmental and economic), benefits of such an approach as perceived (experienced) by these local rural communities, and specifically land claimants. The study was conducted in communities adjacent to SAFCOL plantations in the Mpumalanga Province of South Africa. Data were collected between May and June 2017 by means of a structured questionnaire. Surveys were conducted on 46 households within the identified communities so as to verify and evaluate perceived benefits in terms of forest products, ecosystem services and amenities/services/infrastructure provided by SAFCOL and the broader forest industry. The results indicated that these communities recognize and obtain numerous social, environmental and economic benefits from the forest including Non-Timber Forest Products (NTFPs) such as firewood; forest provisioning ecosystem services (FPESs) such as improved water quality; and more metaphysical benefits such as access to gravesites and the protection of traditions and customs. These benefits have the ability to improve the social well-being, economic independence, and the quality of environmental services obtained by the associated communities. It was however found that the utilization of these benefits was widely differentiated according to gender and land claimant status. Whilst males and females largely benefitted equally, there was a distinct benefit preference between genders for different NTFPs. For example males showed preference for the collection of building material, bush meat and for livestock husbandry, whilst females showed preference for the collection of firewood, medicinal plants and fruit, amongst others. Similarly, it was found that overall, non-land claimants benefited more than land claimants. Reasons for this are primarily due to the increased distance with which the land claimants live from the forest resource when compared to non-land claimants. The empirical value of the data produced through this study will be invaluable in negotiations with the land claimant communities on land settlement agreements, joint venture proposals, including Participatory Forest Management, and future land tenure. Through such inclusivity and vested interest in the sustainable management of the forests, corporate risk is reduced and community/land claimant relationships are reinforced. Such Participatory Forest Management arrangements are key to ensuring the longevity and resilience to the forest sector post-transfer of claimed land.
- Full Text:
- Date Issued: 2019
Determining the effects of debt-to-GDP ratio on the economic growth of Greece, Italy and South Africa
- Mowoe, Merioboroghene Oreoluwa
- Authors: Mowoe, Merioboroghene Oreoluwa
- Date: 2019
- Subjects: Debts, Public -- Greece , Debts, Public -- Italy Debts, Public -- South Africa Economic development Greece -- Economic conditions Italy -- Economic conditions South Africa -- Economic conditions
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/41942 , vital:36611
- Description: A major challenge that most countries currently face, is to bring their economies out of indebtedness. In this study, the impact of public debt on the economic growth of Greece, Italy, and South Africa, and any similarities between them, was analysed. Two models were adopted for this purpose, the ARDL model and the VEC model. The ARDL was used to conduct a co-integration relationship between public debts, economic growth, with four controlled variables: inflation, government spending, net export, and investment. The results showed a negative co-integrating relationship for all three countries. In addition, the VEC model was adopted to determine whether there was causation between public debt and economic growth in each of the three countries. It was found that a unidirectional causality between public debt and economic growth exists for all three countries. For Greece, a long-run causality was found moving from economic growth to public debt. For Italy, short-run and long-run causalities were found, moving from economic growth to public debt. For South Africa, both a long-run and a short-run causality were found moving from public debt to economic growth. The economic growth and development policies for reducing the public debt of these countries, are recommended in accordance with the findings of the research results.
- Full Text:
- Date Issued: 2019
- Authors: Mowoe, Merioboroghene Oreoluwa
- Date: 2019
- Subjects: Debts, Public -- Greece , Debts, Public -- Italy Debts, Public -- South Africa Economic development Greece -- Economic conditions Italy -- Economic conditions South Africa -- Economic conditions
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/41942 , vital:36611
- Description: A major challenge that most countries currently face, is to bring their economies out of indebtedness. In this study, the impact of public debt on the economic growth of Greece, Italy, and South Africa, and any similarities between them, was analysed. Two models were adopted for this purpose, the ARDL model and the VEC model. The ARDL was used to conduct a co-integration relationship between public debts, economic growth, with four controlled variables: inflation, government spending, net export, and investment. The results showed a negative co-integrating relationship for all three countries. In addition, the VEC model was adopted to determine whether there was causation between public debt and economic growth in each of the three countries. It was found that a unidirectional causality between public debt and economic growth exists for all three countries. For Greece, a long-run causality was found moving from economic growth to public debt. For Italy, short-run and long-run causalities were found, moving from economic growth to public debt. For South Africa, both a long-run and a short-run causality were found moving from public debt to economic growth. The economic growth and development policies for reducing the public debt of these countries, are recommended in accordance with the findings of the research results.
- Full Text:
- Date Issued: 2019
Determining the hydrological functioning of the palmiet wetlands in the Eastern and Western Cape South Africa
- Authors: Smith, Caitlin
- Date: 2019
- Subjects: Wetlands -- South Africa -- Eastern Cape , Wetland ecology -- South Africa -- Eastern Cape , Wetland management -- South Africa -- Eastern Cape , Prioniaceae -- South Africa -- Eastern Cape , Prionium serratum -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/95956 , vital:31218
- Description: Wetlands provide a range of supporting, regulating and provisioning ecosystem services, including hydrological benefits such as flood attenuation and sustaining base flows. Despite their value, wetlands are one of the most vulnerable ecosystems in South Africa. Palmiet wetlands in the Eastern and Western Cape are particularly threatened. Palmiet (Prionium serratum) is a robust perennial plant that is endemic to wetlands and rivers located in the sandstones and quartzites of the Table Mountain Group (TMG), in the Eastern and Western Cape as well as the Natal Group sandstones in KwaZulu-Natal. Palmiet is described as an ecosystem engineer because of its ability to alter its environment and create large valley-bottom wetlands. The Krom River is an important water source for the city of Port Elizabeth and there has been a decline in palmiet wetlands along the Krom River as a result of alien vegetation invasion, agricultural activity, and gully erosion. Working for Water has been clearing alien vegetation and Working for Wetlands has been installing rehabilitation structures in the Krom River catchment for a number of years. There are, however, serious knowledge gaps in the understanding of palmiet wetland structure and function, particularly in respect of the hydrological functioning of these wetland systems. The aim of this study was to investigate the hydrology (surface and groundwater) behind these wetland systems. The investigation focussed on small-scale dynamics of the palmiet wetland system in order to increase general understanding of the surface water and groundwater processes of these wetland systems. Field work was concentrated on the Kompanjiesdrif and Krugersland palmiet wetlands in the upper K90A Krom River catchment. The investigation involved the installation of piezometers, water quality and stable isotope sampling and analysis, an Electrical Resistivity Tomography survey, and hydrological and mixing cell modelling. The results of the investigation indicate that the hydrological functioning of palmiet wetlands is closely linked with high sub-surface discharges typically associated with TMG aquifers. It is proposed that the palmiet wetlands are sustained by significant amounts of sub-surface water (both groundwater and interflow) moving through preferential flow paths in the alluvial fans and tributaries, which are in turn sustained by groundwater discharge from the surrounding sandstones and quartzites of the Nardouw Sub-group and Peninsula Formation. The palmiet wetlands clearly retain a significant amount of water, leading to the maintenance of prolonged flows, and a larger baseflow. However, it is hypothesised that the occurrence of palmiet as the dominant species in these wetlands is due to the sustained low flows related to catchment geology and high hydrological connectivity between the catchment and the wetland that is enabled by flow paths that allow the free flow of water from the catchment to the wetland. It is further proposed that palmiet is possibly more reliant on a consistent water supply for its existence and survival than it is on acidic nutrient-poor water and soils as stated by other authors.
- Full Text:
- Date Issued: 2019
- Authors: Smith, Caitlin
- Date: 2019
- Subjects: Wetlands -- South Africa -- Eastern Cape , Wetland ecology -- South Africa -- Eastern Cape , Wetland management -- South Africa -- Eastern Cape , Prioniaceae -- South Africa -- Eastern Cape , Prionium serratum -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/95956 , vital:31218
- Description: Wetlands provide a range of supporting, regulating and provisioning ecosystem services, including hydrological benefits such as flood attenuation and sustaining base flows. Despite their value, wetlands are one of the most vulnerable ecosystems in South Africa. Palmiet wetlands in the Eastern and Western Cape are particularly threatened. Palmiet (Prionium serratum) is a robust perennial plant that is endemic to wetlands and rivers located in the sandstones and quartzites of the Table Mountain Group (TMG), in the Eastern and Western Cape as well as the Natal Group sandstones in KwaZulu-Natal. Palmiet is described as an ecosystem engineer because of its ability to alter its environment and create large valley-bottom wetlands. The Krom River is an important water source for the city of Port Elizabeth and there has been a decline in palmiet wetlands along the Krom River as a result of alien vegetation invasion, agricultural activity, and gully erosion. Working for Water has been clearing alien vegetation and Working for Wetlands has been installing rehabilitation structures in the Krom River catchment for a number of years. There are, however, serious knowledge gaps in the understanding of palmiet wetland structure and function, particularly in respect of the hydrological functioning of these wetland systems. The aim of this study was to investigate the hydrology (surface and groundwater) behind these wetland systems. The investigation focussed on small-scale dynamics of the palmiet wetland system in order to increase general understanding of the surface water and groundwater processes of these wetland systems. Field work was concentrated on the Kompanjiesdrif and Krugersland palmiet wetlands in the upper K90A Krom River catchment. The investigation involved the installation of piezometers, water quality and stable isotope sampling and analysis, an Electrical Resistivity Tomography survey, and hydrological and mixing cell modelling. The results of the investigation indicate that the hydrological functioning of palmiet wetlands is closely linked with high sub-surface discharges typically associated with TMG aquifers. It is proposed that the palmiet wetlands are sustained by significant amounts of sub-surface water (both groundwater and interflow) moving through preferential flow paths in the alluvial fans and tributaries, which are in turn sustained by groundwater discharge from the surrounding sandstones and quartzites of the Nardouw Sub-group and Peninsula Formation. The palmiet wetlands clearly retain a significant amount of water, leading to the maintenance of prolonged flows, and a larger baseflow. However, it is hypothesised that the occurrence of palmiet as the dominant species in these wetlands is due to the sustained low flows related to catchment geology and high hydrological connectivity between the catchment and the wetland that is enabled by flow paths that allow the free flow of water from the catchment to the wetland. It is further proposed that palmiet is possibly more reliant on a consistent water supply for its existence and survival than it is on acidic nutrient-poor water and soils as stated by other authors.
- Full Text:
- Date Issued: 2019
Developing Mother Tongues as Academic Languages in Primary Schools in Kenya: Exploring Extent and Indispensability
- Mose, Peter N, Kaschula, Russell H
- Authors: Mose, Peter N , Kaschula, Russell H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/174793 , vital:42510 , https://doi.org/10.1080/15348458.2019.1645605
- Description: The language in education policy in Kenya recommends mother tongue education in primary school learning. The purpose of this study was to explore the development of mother tongues as academic languages at the lower primary section in which the languages are supposed to be used. The exploration was on the functions they play in classroom instruction and if they are dispensable or otherwise. Ekegusii was used as a case study. Data were obtained through classroom observations and administration of semi-structured interviews with lower primary teachers. The findings indicate that mother tongues play important pedagogical functions in grades 1 up to 3, but not exactly as contemplated in the language policy. Secondly, mother tongues are indispensable in classroom teaching in spite of negative attitude towards their use.
- Full Text:
- Date Issued: 2019
- Authors: Mose, Peter N , Kaschula, Russell H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/174793 , vital:42510 , https://doi.org/10.1080/15348458.2019.1645605
- Description: The language in education policy in Kenya recommends mother tongue education in primary school learning. The purpose of this study was to explore the development of mother tongues as academic languages at the lower primary section in which the languages are supposed to be used. The exploration was on the functions they play in classroom instruction and if they are dispensable or otherwise. Ekegusii was used as a case study. Data were obtained through classroom observations and administration of semi-structured interviews with lower primary teachers. The findings indicate that mother tongues play important pedagogical functions in grades 1 up to 3, but not exactly as contemplated in the language policy. Secondly, mother tongues are indispensable in classroom teaching in spite of negative attitude towards their use.
- Full Text:
- Date Issued: 2019
Developing ocean particle tracking tools for cross-disciplinary oceanic research with applications in the Agulhas current region
- Hart-Davis, Michael Geofrey, Backeberg, Björn C
- Authors: Hart-Davis, Michael Geofrey , Backeberg, Björn C
- Date: 2019
- Subjects: Ocean currents , Ocean currents -- Measurement Oceanography Oceanography -- Research -- South Atlantic Ocean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42308 , vital:36644
- Description: Lagrangian ocean analysis is a powerful way to study ocean processes from in-situ observations and numerical model simulations. As numerical modelling capabilities develop and physical mechanisms of the ocean are better understood, the importance of particle trajectory modelling continues to increase. Therefore, developing cross-disciplinary particle trajectory model applications for the Greater Agulhas System is highly relevant due to its potential contribution to scientific studies and operational applications. This thesis presents the results of developing particle trajectory model applications in the Greater Agulhas System towards better understanding the physical mechanisms that drive ocean processes in the region. The model is used in three applications that demonstrate their cross-disciplinary potential. These applications include a search and rescue scenario, the study of ocean dynamics and the study of the fate of juvenile turtles. Introducing spatially and temporally varying stochastic motion to account for the processes not resolved in the ocean surface current products, as well as including more appropriate boundary conditions, were shown to improve the accuracy of virtual drifters in representing the trajectory of a real surface drifter. Next, implementing the spatially and temporally varying stochastic motion in the particle trajectory model and applying it to a search and rescue scenario of a capsized catamaran revealed that including both winds and surface ocean currents in the particle trajectory model allowed for an improved prediction of the capsized vessel’s trajectory. By comparing a pair of real surface drifters with the particle trajectory model and analysing high resolution sea surface temperature (SST) fields it was shown that the formation of an eddy on the Agulhas Plateau combined with the weakening of the core current velocity resulted in enhanced eddycurrent interactions facilitating the separation of the real surface drifter-pair as they passed through this region. Lastly, the particle trajectory model was used to study the importance of including active swimming characteristic when studying the fate of juvenile turtles. It was found that including active swimming resulted in a change in the distribution of juvenile turtles and, therefore, needs to be included to provide a proper understanding of the fate of juvenile turtles in the ocean. With further development and refinement of the particle trajectory model, Lagrangian ocean analysis has the potential to provide valuable information towards improving our understanding of physical and biological ocean processes at a range of spatial and temporal scales with potential operational oceanography applications.
- Full Text:
- Date Issued: 2019
- Authors: Hart-Davis, Michael Geofrey , Backeberg, Björn C
- Date: 2019
- Subjects: Ocean currents , Ocean currents -- Measurement Oceanography Oceanography -- Research -- South Atlantic Ocean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42308 , vital:36644
- Description: Lagrangian ocean analysis is a powerful way to study ocean processes from in-situ observations and numerical model simulations. As numerical modelling capabilities develop and physical mechanisms of the ocean are better understood, the importance of particle trajectory modelling continues to increase. Therefore, developing cross-disciplinary particle trajectory model applications for the Greater Agulhas System is highly relevant due to its potential contribution to scientific studies and operational applications. This thesis presents the results of developing particle trajectory model applications in the Greater Agulhas System towards better understanding the physical mechanisms that drive ocean processes in the region. The model is used in three applications that demonstrate their cross-disciplinary potential. These applications include a search and rescue scenario, the study of ocean dynamics and the study of the fate of juvenile turtles. Introducing spatially and temporally varying stochastic motion to account for the processes not resolved in the ocean surface current products, as well as including more appropriate boundary conditions, were shown to improve the accuracy of virtual drifters in representing the trajectory of a real surface drifter. Next, implementing the spatially and temporally varying stochastic motion in the particle trajectory model and applying it to a search and rescue scenario of a capsized catamaran revealed that including both winds and surface ocean currents in the particle trajectory model allowed for an improved prediction of the capsized vessel’s trajectory. By comparing a pair of real surface drifters with the particle trajectory model and analysing high resolution sea surface temperature (SST) fields it was shown that the formation of an eddy on the Agulhas Plateau combined with the weakening of the core current velocity resulted in enhanced eddycurrent interactions facilitating the separation of the real surface drifter-pair as they passed through this region. Lastly, the particle trajectory model was used to study the importance of including active swimming characteristic when studying the fate of juvenile turtles. It was found that including active swimming resulted in a change in the distribution of juvenile turtles and, therefore, needs to be included to provide a proper understanding of the fate of juvenile turtles in the ocean. With further development and refinement of the particle trajectory model, Lagrangian ocean analysis has the potential to provide valuable information towards improving our understanding of physical and biological ocean processes at a range of spatial and temporal scales with potential operational oceanography applications.
- Full Text:
- Date Issued: 2019
Development and characterisation of miconazole nitrate loaded solid lipid nanoparticles for incorporation into a vaginal mucoadhesive system
- Authors: Gwimo, Wimana Alexis
- Date: 2019
- Subjects: Vaginitis , Vagina -- Diseases Sexually transmitted diseases -- Diagnosis Sexually transmitted diseases -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39632 , vital:35335
- Description: Vulvovaginal candidiasis (VVC) is the second most common cause of vaginitis, affecting 75% of women of sexual maturity. The prescribed first line treatment involves the use of locally-acting imidazole creams. These conventional dosage forms possess limitations, such as leakage, messiness and low residence time at the site of application; all which promote poor patient adherence to pharmacotherapy. Poor adherence is then attributed to increased incidence of VVC reoccurrence and the emergence of Candida strains. It was, therefore, speculated that through the use of novel drug delivery systems (NDDS), the pharmacokinetic and antimicrobial characteristics of a model antifungal drug (miconazole nitrate [MNZ]) could be improved. Primary aim: To develop, optimise and characterise a mucoadhesive hydrogel incorporated with MNZ loaded solid lipid nanoparticles (MNZ-SLNs) for the intended treatment of VVC. This study was conducted in three phases, viz. pre-formulation studies, development, optimisation and characterisation of MNZ-SLNs, and the development and characterisation of MNZ-SLN-loaded thermoresponsive hydrogel. An alternative method for the quantification of MNZ was developed through the use of an octyl stationary phase. The method was deemed suitable for its intended use with a linear equation of y = 811214x + 67958 and a respective limit of quantitation (LoQ) and detection of 0.015 mg/ml and 0.052 mg/ml. Differential scanning calorimetry (DSC) studies suggested that cholesterol showed great promise of facilitating high drug entrapment efficiency (EE). MNZ-SLNs were prepared by means of a novel melt- emulsification sonication and low temperature solidification method and optimised statistically by a 13-run-two-factor central composite rotatable design (CCRD). The predicted optimisation parameters were 4% m/v lipid concentration and 260.94 sonication time. Optimal MNZ-SLN formulations were prepared and characterised by means of photon correlation spectroscopy (PCS), transmission electron microscopy (TEM) and centrifugation. PCS revealed uniform particles with a narrow polydispersity index (PDI) and a mean hydrodynamic diameter (z-avg.) of 73.03 nm and zeta potential (ZP) of 38.43 mV. Percent EE was calculated via an indirect method as 75.24%. Furthermore, the MNZ -SLNs were incorporated into a mucoadhesive thermo-responsive hydrogel with a sol-gel transition temperature of 33.33 ± 2.82 °C. In vitro drug release testing (IVDRT) was undertaken with the aid of a Franz diffusion vertical cell (FDVC) apparatus. A % cumulative drug release of 27.94% and 15.87% was obtained for MNZ- SLNs and MNZ-SLN hydrogels, respectively, after eight hours. The resultant data was fitted into various kinetic models with the aid of DDSolverTM (Microsoft Excel® add-ins, 2016) to evaluate which model attained the highest correlation co-efficient (r2). Both formulations attained high r2 of 0.9941 and 0.9945, respectively, with the Korsmeyer- Peppas mathematical model. A high diffusional exponent (n) of >1 was observed, suggesting a super case II drug release mechanism. Finally, a modified Kirby-Bauer disc diffusion assay was used for ascertaining Candida albicans susceptibility to the developed formulations. Controls in the form of unloaded preparations and a commercially available cream were used. MNZ-SLNs and MNZ-hydrogel demonstrated superior antifungal activity to the commercially available cream. These results indicate that the developed MNZ-SLNloaded hydrogel formulation with localised thermo-responsive effect may be a promising carrier for intravaginal delivery of MNZ in the treatment of VVC.
- Full Text:
- Date Issued: 2019
- Authors: Gwimo, Wimana Alexis
- Date: 2019
- Subjects: Vaginitis , Vagina -- Diseases Sexually transmitted diseases -- Diagnosis Sexually transmitted diseases -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39632 , vital:35335
- Description: Vulvovaginal candidiasis (VVC) is the second most common cause of vaginitis, affecting 75% of women of sexual maturity. The prescribed first line treatment involves the use of locally-acting imidazole creams. These conventional dosage forms possess limitations, such as leakage, messiness and low residence time at the site of application; all which promote poor patient adherence to pharmacotherapy. Poor adherence is then attributed to increased incidence of VVC reoccurrence and the emergence of Candida strains. It was, therefore, speculated that through the use of novel drug delivery systems (NDDS), the pharmacokinetic and antimicrobial characteristics of a model antifungal drug (miconazole nitrate [MNZ]) could be improved. Primary aim: To develop, optimise and characterise a mucoadhesive hydrogel incorporated with MNZ loaded solid lipid nanoparticles (MNZ-SLNs) for the intended treatment of VVC. This study was conducted in three phases, viz. pre-formulation studies, development, optimisation and characterisation of MNZ-SLNs, and the development and characterisation of MNZ-SLN-loaded thermoresponsive hydrogel. An alternative method for the quantification of MNZ was developed through the use of an octyl stationary phase. The method was deemed suitable for its intended use with a linear equation of y = 811214x + 67958 and a respective limit of quantitation (LoQ) and detection of 0.015 mg/ml and 0.052 mg/ml. Differential scanning calorimetry (DSC) studies suggested that cholesterol showed great promise of facilitating high drug entrapment efficiency (EE). MNZ-SLNs were prepared by means of a novel melt- emulsification sonication and low temperature solidification method and optimised statistically by a 13-run-two-factor central composite rotatable design (CCRD). The predicted optimisation parameters were 4% m/v lipid concentration and 260.94 sonication time. Optimal MNZ-SLN formulations were prepared and characterised by means of photon correlation spectroscopy (PCS), transmission electron microscopy (TEM) and centrifugation. PCS revealed uniform particles with a narrow polydispersity index (PDI) and a mean hydrodynamic diameter (z-avg.) of 73.03 nm and zeta potential (ZP) of 38.43 mV. Percent EE was calculated via an indirect method as 75.24%. Furthermore, the MNZ -SLNs were incorporated into a mucoadhesive thermo-responsive hydrogel with a sol-gel transition temperature of 33.33 ± 2.82 °C. In vitro drug release testing (IVDRT) was undertaken with the aid of a Franz diffusion vertical cell (FDVC) apparatus. A % cumulative drug release of 27.94% and 15.87% was obtained for MNZ- SLNs and MNZ-SLN hydrogels, respectively, after eight hours. The resultant data was fitted into various kinetic models with the aid of DDSolverTM (Microsoft Excel® add-ins, 2016) to evaluate which model attained the highest correlation co-efficient (r2). Both formulations attained high r2 of 0.9941 and 0.9945, respectively, with the Korsmeyer- Peppas mathematical model. A high diffusional exponent (n) of >1 was observed, suggesting a super case II drug release mechanism. Finally, a modified Kirby-Bauer disc diffusion assay was used for ascertaining Candida albicans susceptibility to the developed formulations. Controls in the form of unloaded preparations and a commercially available cream were used. MNZ-SLNs and MNZ-hydrogel demonstrated superior antifungal activity to the commercially available cream. These results indicate that the developed MNZ-SLNloaded hydrogel formulation with localised thermo-responsive effect may be a promising carrier for intravaginal delivery of MNZ in the treatment of VVC.
- Full Text:
- Date Issued: 2019
Development and Validation of a Stability-indicating RP-HPLC Method Using Quality by Design for Estimating Captopril
- Veerubhotla, Krishna, Walker, Roderick B
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183525 , vital:44003 , xlink:href="10.4172/pharmaceutical-sciences.1000478"
- Description: The applicability of a quality by design framework for the development of a sensitive, simple and selective, stability-indicating reversed-phase high-performance liquid chromatography analytical method for the analysis of captopril was investigated. Design of experiments using a central composite design approach was used for method development. Twenty experimental runs were performed with acetonitrile content ranging between 28 and 36 % v/v, pH from 2.8 to 3.6 and temperature between 22° and 32°. The experimental data obtained was used to derive a quadratic model for the retention time of captopril. The optimized method produced sharp peaks with good resolution (>2) for captopril and the internal standard with retention times of 3.1 and 6.2 min, respectively. The experimental data revealed that acetonitrile content in the mobile phase and pH are significant factors that affect the retention time and resolution of captopril. Normal probability plots revealed that the residual and predicted data fall approximately on a straight line, indicating that the experimental error for these studies was evenly distributed suggesting that the model could be used to navigate the design space. This approach is useful to expedite method development and optimization activities in analytical laboratories.
- Full Text:
- Date Issued: 2019
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183525 , vital:44003 , xlink:href="10.4172/pharmaceutical-sciences.1000478"
- Description: The applicability of a quality by design framework for the development of a sensitive, simple and selective, stability-indicating reversed-phase high-performance liquid chromatography analytical method for the analysis of captopril was investigated. Design of experiments using a central composite design approach was used for method development. Twenty experimental runs were performed with acetonitrile content ranging between 28 and 36 % v/v, pH from 2.8 to 3.6 and temperature between 22° and 32°. The experimental data obtained was used to derive a quadratic model for the retention time of captopril. The optimized method produced sharp peaks with good resolution (>2) for captopril and the internal standard with retention times of 3.1 and 6.2 min, respectively. The experimental data revealed that acetonitrile content in the mobile phase and pH are significant factors that affect the retention time and resolution of captopril. Normal probability plots revealed that the residual and predicted data fall approximately on a straight line, indicating that the experimental error for these studies was evenly distributed suggesting that the model could be used to navigate the design space. This approach is useful to expedite method development and optimization activities in analytical laboratories.
- Full Text:
- Date Issued: 2019
Development of a framework for a proposed antimicrobial usage reporting tool for public sector hospitals
- Authors: Ramjan, Yumna
- Date: 2019
- Subjects: Anti-infective agents
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10948/43030 , vital:36727
- Description: Background: The inappropriate and unnecessary use of antimicrobials has increased the need to monitor antimicrobial usage so as to identify inappropriate use. In order to support the antimicrobial stewardship (AMS) programme, it is important to quantify the usage of antimicrobials and this can be achieved by promoting the use of AMS utilisation metrics. They are used to measure the progress and efficacy of an AMS programme (Brotherton, 2018).Primary Aim of Research: The primary aim of the research was to develop a framework for a proposed antimicrobial usage reporting tool, which would integrate with various data sources in order to be used by AMS practitioners to optimise antimicrobial usage in the South African public sector hospital setting.Methodology: The study was divided into three phases: a preliminary phase, a developmental phase and a post-developmental phase. The preliminary phase focused on obtaining a comprehensive understanding of the type and nature of the AMS utilisation metrics and subsequently identifying the views on the usage, usefulness and clinical relevance of those AMS utilisation metrics using a quantitative questionnaire, which was conducted among infectious disease specialists, pharmacists, medical prescribers, i.e. prescribers who were not specialists and clinical pathologists employed at tertiary level, public sector hospitals in the Eastern Cape province of South Africa. Consequently, a qualitative semi-structured interview was conducted among healthcare professionals who were involved in the daily implementation of AMS in the workplace. Results obtained from the quantitative component and qualitative component were integrated in order to develop a framework for a proposed antimicrobial usage reporting tool. Results: The Defined Daily Dose (DDD), Prescribed Daily Dose (PDD) and Days of Therapy (DOT) were identified as the most common AMS metrics (Grau et al., 2013). However, the DDD was the only AMS metric currently recommended by the South African National Department of Health (South African National Department of Health, 2017a)and it was the only AMS metric currently being utilised at two of the five research sites in the Eastern Cape province of South Africa. It was identified that data pertaining to antimicrobial usage was available and was being extracted from Rx Solution®. However, the programme did not have the ability of automatically producing the reports, hence, emphasising on the need for an antimicrobial usage reporting tool for South African public sector hospitals. Therefore, the framework for the proposed antimicrobial usage reporting tool would integrate antimicrobial stock management data with the following AMS utilisation metrics: DDD, DOT and PDD, were considered for inclusion in the proposed antimicrobial usage reporting tool. Conclusion: The qualitative findings obtained during the post-developmental phase, therefore, established that although an electronic platform for the purpose of monitoring antimicrobial usage for the South African public sector hospitals was required, there would be many challenges obstructing the implementation of the proposed antimicrobial usage reporting tool.
- Full Text:
- Date Issued: 2019
- Authors: Ramjan, Yumna
- Date: 2019
- Subjects: Anti-infective agents
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10948/43030 , vital:36727
- Description: Background: The inappropriate and unnecessary use of antimicrobials has increased the need to monitor antimicrobial usage so as to identify inappropriate use. In order to support the antimicrobial stewardship (AMS) programme, it is important to quantify the usage of antimicrobials and this can be achieved by promoting the use of AMS utilisation metrics. They are used to measure the progress and efficacy of an AMS programme (Brotherton, 2018).Primary Aim of Research: The primary aim of the research was to develop a framework for a proposed antimicrobial usage reporting tool, which would integrate with various data sources in order to be used by AMS practitioners to optimise antimicrobial usage in the South African public sector hospital setting.Methodology: The study was divided into three phases: a preliminary phase, a developmental phase and a post-developmental phase. The preliminary phase focused on obtaining a comprehensive understanding of the type and nature of the AMS utilisation metrics and subsequently identifying the views on the usage, usefulness and clinical relevance of those AMS utilisation metrics using a quantitative questionnaire, which was conducted among infectious disease specialists, pharmacists, medical prescribers, i.e. prescribers who were not specialists and clinical pathologists employed at tertiary level, public sector hospitals in the Eastern Cape province of South Africa. Consequently, a qualitative semi-structured interview was conducted among healthcare professionals who were involved in the daily implementation of AMS in the workplace. Results obtained from the quantitative component and qualitative component were integrated in order to develop a framework for a proposed antimicrobial usage reporting tool. Results: The Defined Daily Dose (DDD), Prescribed Daily Dose (PDD) and Days of Therapy (DOT) were identified as the most common AMS metrics (Grau et al., 2013). However, the DDD was the only AMS metric currently recommended by the South African National Department of Health (South African National Department of Health, 2017a)and it was the only AMS metric currently being utilised at two of the five research sites in the Eastern Cape province of South Africa. It was identified that data pertaining to antimicrobial usage was available and was being extracted from Rx Solution®. However, the programme did not have the ability of automatically producing the reports, hence, emphasising on the need for an antimicrobial usage reporting tool for South African public sector hospitals. Therefore, the framework for the proposed antimicrobial usage reporting tool would integrate antimicrobial stock management data with the following AMS utilisation metrics: DDD, DOT and PDD, were considered for inclusion in the proposed antimicrobial usage reporting tool. Conclusion: The qualitative findings obtained during the post-developmental phase, therefore, established that although an electronic platform for the purpose of monitoring antimicrobial usage for the South African public sector hospitals was required, there would be many challenges obstructing the implementation of the proposed antimicrobial usage reporting tool.
- Full Text:
- Date Issued: 2019
Development of a manual to train food handlers of the national school nutrition programme
- Authors: Barkhuizen, Kirsten Lyn
- Date: 2019
- Subjects: Food -- Safety measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36559 , vital:33974
- Description: The study was conducted in order to develop a hygiene and food safety manual that can be used to train the food handlers of the National School Nutrition Programme. The co-operation of the Institute for International Medicine, Partnerships with Children, as part of the Health in Action Programme in this study, is appreciated. Food handlers of the National School Nutrition Programme in low socio-economic schools, in the Nelson Mandela Bay, in the Eastern Cape, were the population of the study. With many South Africans experiencing poverty and food insecurity, the National School Nutrition Programme aims to provide a social safety net and address short term hunger in children. However, challenges are faced regarding the implementation thereof, such as a lack of training of food handlers. This results in poor hygiene and food safety knowledge and behaviour. Subsequently, the risk of transmission of foodborne pathogens and the contamination of food rises. Foodborne illnesses are a major cause of morbidity and mortality, specifically in children, due to weak immune systems. Therefore, the study was conducted in order to develop and test a hygiene and food safety manual so that it can be made available to the South African Department of Education to be used by teachers in order to train the food handlers of the National School Nutrition Programme. The manual can then be used to train all newly recruited food handlers, and therefore ensure that school meals are safe to consume by learners.
- Full Text:
- Date Issued: 2019
- Authors: Barkhuizen, Kirsten Lyn
- Date: 2019
- Subjects: Food -- Safety measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36559 , vital:33974
- Description: The study was conducted in order to develop a hygiene and food safety manual that can be used to train the food handlers of the National School Nutrition Programme. The co-operation of the Institute for International Medicine, Partnerships with Children, as part of the Health in Action Programme in this study, is appreciated. Food handlers of the National School Nutrition Programme in low socio-economic schools, in the Nelson Mandela Bay, in the Eastern Cape, were the population of the study. With many South Africans experiencing poverty and food insecurity, the National School Nutrition Programme aims to provide a social safety net and address short term hunger in children. However, challenges are faced regarding the implementation thereof, such as a lack of training of food handlers. This results in poor hygiene and food safety knowledge and behaviour. Subsequently, the risk of transmission of foodborne pathogens and the contamination of food rises. Foodborne illnesses are a major cause of morbidity and mortality, specifically in children, due to weak immune systems. Therefore, the study was conducted in order to develop and test a hygiene and food safety manual so that it can be made available to the South African Department of Education to be used by teachers in order to train the food handlers of the National School Nutrition Programme. The manual can then be used to train all newly recruited food handlers, and therefore ensure that school meals are safe to consume by learners.
- Full Text:
- Date Issued: 2019
Development of a nystatin-loaded micellar system for oral mucoadhesion
- Authors: Sarpong, Nancy Owusu Akyere
- Date: 2019
- Subjects: Medical microbiology , HIV infections -- Treatment Clinical pharmacology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43556 , vital:36918
- Description: Oropharyngeal Candidiasis (OPC) is an opportunistic fungal infection that affects mostly infants and immunocompromised patients. In recent years, the disease has been on the rise due to an increased life span, the HIV pandemic and the increased use of broad spectrum antibiotics. OPC may be treated using a nystatin suspension, which is not as effective as it could be due to the mechanism by which the suspension is applied to the affected tissue. This research aims to improve the effectiveness of nystatin, for the treatment of OPC, by proposing a nystatin loaded micellar system incorporated into a mucoadhesive system for drug delivery. This will ensure that nystatin is gradually released from the film, thus increasing retention time of nystatin at the affected area. In this study, a mixture design was developed, which was used to determine the most appropriate solvent system for nystatin solubilization. Optimisation of the micelle formulation was achieved by using the central composite rational design (CCRD). The two factors that were taken into consideration were the temperature of the hydration medium (water) and the length of time the micellar solution was exposed to the temperature environment of the rotary evaporator. The responses that were investigated were the mean particle size, mean polydispersity index (PDI), mean zeta potential, change in mean particle size and change in mean PDI. The optimal micelle formulation was characterised for size, stability, morphology and drug encapsulation efficiency. The micelles were found to be spherical and stable with an acceptable size range. However, their drug encapsulation efficiency was low. The mucoadhesive film was formulated and characterised for physical characteristics, pliability, percentage swelling index and drug release profile. The film was found to be highly pliable and evenly distributed with a smooth surface; no bumps or bubbles were visible. The film was able to swell to up to 550 %. In vitro studies showed that nystatin was gradually released from the film.
- Full Text:
- Date Issued: 2019
- Authors: Sarpong, Nancy Owusu Akyere
- Date: 2019
- Subjects: Medical microbiology , HIV infections -- Treatment Clinical pharmacology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43556 , vital:36918
- Description: Oropharyngeal Candidiasis (OPC) is an opportunistic fungal infection that affects mostly infants and immunocompromised patients. In recent years, the disease has been on the rise due to an increased life span, the HIV pandemic and the increased use of broad spectrum antibiotics. OPC may be treated using a nystatin suspension, which is not as effective as it could be due to the mechanism by which the suspension is applied to the affected tissue. This research aims to improve the effectiveness of nystatin, for the treatment of OPC, by proposing a nystatin loaded micellar system incorporated into a mucoadhesive system for drug delivery. This will ensure that nystatin is gradually released from the film, thus increasing retention time of nystatin at the affected area. In this study, a mixture design was developed, which was used to determine the most appropriate solvent system for nystatin solubilization. Optimisation of the micelle formulation was achieved by using the central composite rational design (CCRD). The two factors that were taken into consideration were the temperature of the hydration medium (water) and the length of time the micellar solution was exposed to the temperature environment of the rotary evaporator. The responses that were investigated were the mean particle size, mean polydispersity index (PDI), mean zeta potential, change in mean particle size and change in mean PDI. The optimal micelle formulation was characterised for size, stability, morphology and drug encapsulation efficiency. The micelles were found to be spherical and stable with an acceptable size range. However, their drug encapsulation efficiency was low. The mucoadhesive film was formulated and characterised for physical characteristics, pliability, percentage swelling index and drug release profile. The film was found to be highly pliable and evenly distributed with a smooth surface; no bumps or bubbles were visible. The film was able to swell to up to 550 %. In vitro studies showed that nystatin was gradually released from the film.
- Full Text:
- Date Issued: 2019
Development of an Extensible Framework for Easy Implementation of Image Processing Applications on Android Operating System
- Authors: Gunu, Bulelani
- Date: 2019
- Subjects: Operating systems (Computers)
- Language: English
- Type: Thesis , Masters , MSc (Computer Science )
- Identifier: http://hdl.handle.net/10353/17201 , vital:40865
- Description: Image processing is a field that has been in existence for many years and it continues to grow with many other research areas adopting its use. One such research area is the area of mobile devices. Mobile devices have been equipped with image processing software and hardware so as to apply image processing features. While there are many applications of image processing and new applications have been developed, there are still many functionalities that these image processing software perform the same. The development of these software from scratch requires a lot of effort and can be time consuming. This becomes even worse for mobile device application developers, specifically Android developers, who have no knowledge of implementing image processing functionalities. This project offers a software framework which allows Android application developers to focus on their unique requirements while incorporating image processing features into their applications. The framework provides the common image processing functionalities and Android developers do not need to know the internal working of the framework in order to use it. This helps reduce application development time and effort. The framework also offers an extensibility feature which takes into consideration the future growth. This means that third party developers can keep the framework up to date with the technological advancements. The presented framework is shown to be requiring less technical expertise. Also, the way in which the system is design makes it easy to understand. This design can be adopted for other related projects that require extensible frameworks for the Android operating system.
- Full Text:
- Date Issued: 2019
- Authors: Gunu, Bulelani
- Date: 2019
- Subjects: Operating systems (Computers)
- Language: English
- Type: Thesis , Masters , MSc (Computer Science )
- Identifier: http://hdl.handle.net/10353/17201 , vital:40865
- Description: Image processing is a field that has been in existence for many years and it continues to grow with many other research areas adopting its use. One such research area is the area of mobile devices. Mobile devices have been equipped with image processing software and hardware so as to apply image processing features. While there are many applications of image processing and new applications have been developed, there are still many functionalities that these image processing software perform the same. The development of these software from scratch requires a lot of effort and can be time consuming. This becomes even worse for mobile device application developers, specifically Android developers, who have no knowledge of implementing image processing functionalities. This project offers a software framework which allows Android application developers to focus on their unique requirements while incorporating image processing features into their applications. The framework provides the common image processing functionalities and Android developers do not need to know the internal working of the framework in order to use it. This helps reduce application development time and effort. The framework also offers an extensibility feature which takes into consideration the future growth. This means that third party developers can keep the framework up to date with the technological advancements. The presented framework is shown to be requiring less technical expertise. Also, the way in which the system is design makes it easy to understand. This design can be adopted for other related projects that require extensible frameworks for the Android operating system.
- Full Text:
- Date Issued: 2019
Development of high yielding strain of Pleurotus tuber-regium fructification, nutritional and phylogenetic studies
- Bamigboye, Comfort O, Oloke, Julius K, Dames, Joanna F
- Authors: Bamigboye, Comfort O , Oloke, Julius K , Dames, Joanna F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448595 , vital:74745 , https://doi.org/10.1007/s13197-019-03786-7
- Description: Mushrooms are nutritionally rich, healthy and medicinal. Pleurotus tuber-regium (Fr.) is one of the nutritious medicinal mushroom found in the tropics and subtropics, but with history of slow growth and low sclerotia yield. In this study, mutants were created by mycelia exposure to ultraviolet irradiation (at a wavelength of 254 nm and a distance of 45 cm), for 3 h and sub-cultured at 30 min interval. The DNA from the wild and mutant strains were extracted, PCR amplified and sequenced. A phylogenetic tree was constructed to show the degree of similarity and differences between the wild and the mutant strains. Fructification studies were conducted on Rhodes grass straw and sawdust to determine the viability of the mutant strains and any nutritional improvement. The wild strain of P. tuber-regium and mutant produced at 30 min (Pt30) cultivated on sawdust and Rhodes straw, yielded sclerotia with biological efficiency of 8.8 and 47.6% respectively. Proximate analysis of the sclerotium showed that the mutant, Pt30, had improved nutritional compositions compared to the wild strain with a total non-structural carbohydrate concentration of 2.41 g as against 0.93 g. Conclusively in this study, better strains of P. tuber-regium were produced with faster growth rate, higher mycelia ramification rate on lignocellulosic substrate and a higher sclerotia yield than the wild P. tuber-regium. It was also established that mutagenesis is capable of improving P. tuber-regium for a successful commercial venture in sclerotia production.
- Full Text:
- Date Issued: 2019
- Authors: Bamigboye, Comfort O , Oloke, Julius K , Dames, Joanna F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448595 , vital:74745 , https://doi.org/10.1007/s13197-019-03786-7
- Description: Mushrooms are nutritionally rich, healthy and medicinal. Pleurotus tuber-regium (Fr.) is one of the nutritious medicinal mushroom found in the tropics and subtropics, but with history of slow growth and low sclerotia yield. In this study, mutants were created by mycelia exposure to ultraviolet irradiation (at a wavelength of 254 nm and a distance of 45 cm), for 3 h and sub-cultured at 30 min interval. The DNA from the wild and mutant strains were extracted, PCR amplified and sequenced. A phylogenetic tree was constructed to show the degree of similarity and differences between the wild and the mutant strains. Fructification studies were conducted on Rhodes grass straw and sawdust to determine the viability of the mutant strains and any nutritional improvement. The wild strain of P. tuber-regium and mutant produced at 30 min (Pt30) cultivated on sawdust and Rhodes straw, yielded sclerotia with biological efficiency of 8.8 and 47.6% respectively. Proximate analysis of the sclerotium showed that the mutant, Pt30, had improved nutritional compositions compared to the wild strain with a total non-structural carbohydrate concentration of 2.41 g as against 0.93 g. Conclusively in this study, better strains of P. tuber-regium were produced with faster growth rate, higher mycelia ramification rate on lignocellulosic substrate and a higher sclerotia yield than the wild P. tuber-regium. It was also established that mutagenesis is capable of improving P. tuber-regium for a successful commercial venture in sclerotia production.
- Full Text:
- Date Issued: 2019
Development of polypropylene – waste tyre crumbs based tpe's with the aid of vistamaxxtm as a compatibiliser
- Authors: Masele, Siyamtanda
- Date: 2019
- Subjects: Polymers , Polymerization Crumb rubber Rubber
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/42589 , vital:36670
- Description: Polypropylene (PP) is a semi crystalline thermoplastic polymer and one of the most commonly used polyolefins. It is well known for its poor impact resistance; hence, for industries such as the automotive and packaging, reinforced PP is widely used. In general plastic waste disposal is a global crisis raising environmental and human health concerns, with PP being the highest consumed polymer globally; hence a push in the reuse and recycling of PP. Recycled polypropylene has limited uses for industrial applications due to its highly reduced properties owing to the recycling process which inhabits cutting of chains lengths, broadened molecular weight distributions and compromised crystallinity. Several studies have investigated the use of reinforcing fillers and modifiers in order to improve properties of PP. Inorganic materials and minerals such as CaCO3, Mica, Talc and glass fibre are used as fillers to improve mechanical properties (tensile and hardness), but still lacks in improving the impact resistance. Thermoplastic elastomers (TPE) are typically used where elastomer and thermoplastics fail as individual components. This is because they have the benefit of thermoplastic properties at hypo ambient condition and elastomer properties such as good impact and elongation at sub-zero conditions. The study took a route of using PP and waste tyre crumb rubber (CR) material to prepare potentially low-cost waste based TPE’s, which would then inherit both properties of PP and the rubber component. VistamaxxTM 6202 (EPR), a commercial name for ethylene-propylene monomer (EPR), was used as a compatibiliser to improve interaction between PP and CR and to contribute towards the overall improvement of various properties such as mechanical properties. VistamaxxTM has a low glass transition temperature (Tg, = -30 ºC), which is important for low temperature applications such as cold storage; it also has a very high elongation and as a result contributed significantly to the overall properties when used in TPE blends. The study highlighted differences between two TPE compounding formulation pathways; namely master-batch (MB) and design of experiments (DoE). The MB formulations were blends that were prepared by a conventional way of compounding; where a pre-mixed CR/EPR blend, in the ratio of 80(CR):20(EPR), was used to form a master-batch. Results showed that there are some similarities between TPEs prepared in different ways, which suggests that the ultimate properties such as thermal stability are in fact more PP matrix based. Thermal analyses results revealed that when high amount of CR was added to the TPE blends, there was a substantial amount of residue mainly due to inherent carbon black. The degree of crystallinity of the blends decreased with increased amounts of CR irrespective of whether it was the MB or DoE blends. The MB TPE blends demonstrated that hardness is not linked to the amount of the MB nor the crystallinity of blends. Meanwhile, tensile elongation and tensile stress were affected by crystallinity. On the other hand, the impact strength findings showed that the amount of MB in TPE blends reached a threshold at 30%. The DoE based TPE blends demonstrated that the optimum mechanical properties are observed when components of the blends are incorporated individually during compounding. This was observed for impact strength, tensile stress as well as elongation at break. The results showed that the incorporation of EPR should be at least 20% for good impact and elongation properties; however, for tensile and hardness, the PP matrix must be high. The study also showed that, for better mechanical properties it was more suitable to use the blends formulated with DoE, because the master-batch approach limited the improving of the mechanical properties by an addition of up to 30% of both the CR and EPR. The storage modulus as well as the tan delta for both MB and DoE decreased when the elastomeric phases were added on both methods, whereas tan delta Tg values decreased as more of the elastomeric phase was added. Evidence from morphology studies showed that the majority of TPE blends suffer from inadequate distribution and adhesion between PP and elastomer; resulting in poor mechanical properties. Furthermore, a threshold of matrix invasion is observed from 30% and above of CR in the blend, where lack of in capsulated lamps of CR were observed hindering the stress induced crystallization and relaxation of the PP phase. The latter was observed irrespective of the type of blend, which strongly suggests and highlights the limits of blending PP with elastomers. Study demonstrated the ability of VistamaxxTM to be utilized as a binding material for PP and CR and displaying the challenges that might arise when used as a master-batch with crumb rubber.
- Full Text:
- Date Issued: 2019
- Authors: Masele, Siyamtanda
- Date: 2019
- Subjects: Polymers , Polymerization Crumb rubber Rubber
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/42589 , vital:36670
- Description: Polypropylene (PP) is a semi crystalline thermoplastic polymer and one of the most commonly used polyolefins. It is well known for its poor impact resistance; hence, for industries such as the automotive and packaging, reinforced PP is widely used. In general plastic waste disposal is a global crisis raising environmental and human health concerns, with PP being the highest consumed polymer globally; hence a push in the reuse and recycling of PP. Recycled polypropylene has limited uses for industrial applications due to its highly reduced properties owing to the recycling process which inhabits cutting of chains lengths, broadened molecular weight distributions and compromised crystallinity. Several studies have investigated the use of reinforcing fillers and modifiers in order to improve properties of PP. Inorganic materials and minerals such as CaCO3, Mica, Talc and glass fibre are used as fillers to improve mechanical properties (tensile and hardness), but still lacks in improving the impact resistance. Thermoplastic elastomers (TPE) are typically used where elastomer and thermoplastics fail as individual components. This is because they have the benefit of thermoplastic properties at hypo ambient condition and elastomer properties such as good impact and elongation at sub-zero conditions. The study took a route of using PP and waste tyre crumb rubber (CR) material to prepare potentially low-cost waste based TPE’s, which would then inherit both properties of PP and the rubber component. VistamaxxTM 6202 (EPR), a commercial name for ethylene-propylene monomer (EPR), was used as a compatibiliser to improve interaction between PP and CR and to contribute towards the overall improvement of various properties such as mechanical properties. VistamaxxTM has a low glass transition temperature (Tg, = -30 ºC), which is important for low temperature applications such as cold storage; it also has a very high elongation and as a result contributed significantly to the overall properties when used in TPE blends. The study highlighted differences between two TPE compounding formulation pathways; namely master-batch (MB) and design of experiments (DoE). The MB formulations were blends that were prepared by a conventional way of compounding; where a pre-mixed CR/EPR blend, in the ratio of 80(CR):20(EPR), was used to form a master-batch. Results showed that there are some similarities between TPEs prepared in different ways, which suggests that the ultimate properties such as thermal stability are in fact more PP matrix based. Thermal analyses results revealed that when high amount of CR was added to the TPE blends, there was a substantial amount of residue mainly due to inherent carbon black. The degree of crystallinity of the blends decreased with increased amounts of CR irrespective of whether it was the MB or DoE blends. The MB TPE blends demonstrated that hardness is not linked to the amount of the MB nor the crystallinity of blends. Meanwhile, tensile elongation and tensile stress were affected by crystallinity. On the other hand, the impact strength findings showed that the amount of MB in TPE blends reached a threshold at 30%. The DoE based TPE blends demonstrated that the optimum mechanical properties are observed when components of the blends are incorporated individually during compounding. This was observed for impact strength, tensile stress as well as elongation at break. The results showed that the incorporation of EPR should be at least 20% for good impact and elongation properties; however, for tensile and hardness, the PP matrix must be high. The study also showed that, for better mechanical properties it was more suitable to use the blends formulated with DoE, because the master-batch approach limited the improving of the mechanical properties by an addition of up to 30% of both the CR and EPR. The storage modulus as well as the tan delta for both MB and DoE decreased when the elastomeric phases were added on both methods, whereas tan delta Tg values decreased as more of the elastomeric phase was added. Evidence from morphology studies showed that the majority of TPE blends suffer from inadequate distribution and adhesion between PP and elastomer; resulting in poor mechanical properties. Furthermore, a threshold of matrix invasion is observed from 30% and above of CR in the blend, where lack of in capsulated lamps of CR were observed hindering the stress induced crystallization and relaxation of the PP phase. The latter was observed irrespective of the type of blend, which strongly suggests and highlights the limits of blending PP with elastomers. Study demonstrated the ability of VistamaxxTM to be utilized as a binding material for PP and CR and displaying the challenges that might arise when used as a master-batch with crumb rubber.
- Full Text:
- Date Issued: 2019
Development of silver-based polyaniline nanocomposite for electrochemical oxidation and detection of organosulfur compounds
- Authors: Shoba, Siyabonga
- Date: 2019
- Subjects: Polyethylene -- Analysis , Composite materials Nanocomposites (Materials)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43600 , vital:36928
- Description: Human activities such as combustion of fossil fuels through automobiles, factories and electricity generation using coal results in major productions of sulfur dioxide to the atmosphere. The sulfur dioxide gas chemically reacts with other substances (i.e. water and oxygen) in the atmosphere and produces acidic pollutants. These acidic pollutants exist in both wet and dry form and before they are deposited on the earth’s surface, they can travel long distances carried by the wind. They are deposited in a wet form as rain, snow, fog and sleet and in a dry form as gases or particles. This has led to the mandated 10 ppm S in fuel by the environmental protection agency (EPA). Electrochemical desulfurization (ECDS) has been reported as an innovative technique for removing sulfur via redox processes. ECDS technique is a low costs process as no catalysts and oxidant are involved and it is a green technology (environmental benignity), thus making the process more economical than conventional hydrodesulfurization (HDS) technologies. Modification of electrodes for electrochemistry as well as electrodeposition of metal nanoparticles offers interesting electrochemical activities due to their reduced size and high surface area to volume ratio. Electrochemical oxidation of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was analysed in acetonitrile using carbon electrodes modified with silver (Ag)-polyaniline (PAni) based nanocomposites (GCE/PAni/Ag and GCE/Ag). The PAni, PAni/Ag composites were characterized using spectroscopic (FT-IR, XRD, XPS) and microscopic (SEM and TEM) techniques. SEM confirmed that the synthesized PAni and PAni/Ag presented an amorphous granular morphology with the aggregation of small irregular particle sizes. Cyclic voltammetry of BT, DBT and 4,6-DMDBT on the modified glassy carbon (GCE) electrode show chemically irreversible anodic peaks which corresponds to electron transfer of sulfur to form sulfoxide and lastly sulfone containing compounds. The overall conversion yield of DBT and 4,6-DMDBT to respective sulfones increased as water content increases. Products were characterized by means of gas chromatograph coupled to mass spectrometer (GC-MS), 1H and 13C NMR. Similarly, silver-modified Glassy Carbon (GCE) electrode was used for the electrochemical detection of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in the presence of naphthalene (NP) and carbazole (CR). The electrochemical response of BT, DBT and 4,6-DMDBT on the modified electrode was determined using Differential Pulse Voltammetry (DPV) in acetonitrile. The electrochemical behaviour of BT, DBT and 4,6-DMDBT showed that the modified electrode exhibited excellent oxidation electro-catalytic activity. The dynamic range for the organosulfur compounds determination was from 1 to 11 ppm with detection limits (LOD) of 0.60 ppmS, 0.41 ppmS and 0.21 ppmS for BT, DBT and 4,6-DMDBT, respectively. Electrochemical sensor showed excellent selectivity of the compounds in the presence of interfering compounds such as naphthalene, carbazole and thiourea over the studied range of concentrations. The prepared electrode exhibited satisfactory reusability and stability after four successive measurement. It has been demonstrated in this study that modified glassy carbon (GCE) electrode (GCE/PAni/Ag) can be successfully used for the assay of sulfur containing compounds such as BT, DBT and 4, 6-DMDBT in petroleum samples.
- Full Text:
- Date Issued: 2019
- Authors: Shoba, Siyabonga
- Date: 2019
- Subjects: Polyethylene -- Analysis , Composite materials Nanocomposites (Materials)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43600 , vital:36928
- Description: Human activities such as combustion of fossil fuels through automobiles, factories and electricity generation using coal results in major productions of sulfur dioxide to the atmosphere. The sulfur dioxide gas chemically reacts with other substances (i.e. water and oxygen) in the atmosphere and produces acidic pollutants. These acidic pollutants exist in both wet and dry form and before they are deposited on the earth’s surface, they can travel long distances carried by the wind. They are deposited in a wet form as rain, snow, fog and sleet and in a dry form as gases or particles. This has led to the mandated 10 ppm S in fuel by the environmental protection agency (EPA). Electrochemical desulfurization (ECDS) has been reported as an innovative technique for removing sulfur via redox processes. ECDS technique is a low costs process as no catalysts and oxidant are involved and it is a green technology (environmental benignity), thus making the process more economical than conventional hydrodesulfurization (HDS) technologies. Modification of electrodes for electrochemistry as well as electrodeposition of metal nanoparticles offers interesting electrochemical activities due to their reduced size and high surface area to volume ratio. Electrochemical oxidation of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was analysed in acetonitrile using carbon electrodes modified with silver (Ag)-polyaniline (PAni) based nanocomposites (GCE/PAni/Ag and GCE/Ag). The PAni, PAni/Ag composites were characterized using spectroscopic (FT-IR, XRD, XPS) and microscopic (SEM and TEM) techniques. SEM confirmed that the synthesized PAni and PAni/Ag presented an amorphous granular morphology with the aggregation of small irregular particle sizes. Cyclic voltammetry of BT, DBT and 4,6-DMDBT on the modified glassy carbon (GCE) electrode show chemically irreversible anodic peaks which corresponds to electron transfer of sulfur to form sulfoxide and lastly sulfone containing compounds. The overall conversion yield of DBT and 4,6-DMDBT to respective sulfones increased as water content increases. Products were characterized by means of gas chromatograph coupled to mass spectrometer (GC-MS), 1H and 13C NMR. Similarly, silver-modified Glassy Carbon (GCE) electrode was used for the electrochemical detection of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in the presence of naphthalene (NP) and carbazole (CR). The electrochemical response of BT, DBT and 4,6-DMDBT on the modified electrode was determined using Differential Pulse Voltammetry (DPV) in acetonitrile. The electrochemical behaviour of BT, DBT and 4,6-DMDBT showed that the modified electrode exhibited excellent oxidation electro-catalytic activity. The dynamic range for the organosulfur compounds determination was from 1 to 11 ppm with detection limits (LOD) of 0.60 ppmS, 0.41 ppmS and 0.21 ppmS for BT, DBT and 4,6-DMDBT, respectively. Electrochemical sensor showed excellent selectivity of the compounds in the presence of interfering compounds such as naphthalene, carbazole and thiourea over the studied range of concentrations. The prepared electrode exhibited satisfactory reusability and stability after four successive measurement. It has been demonstrated in this study that modified glassy carbon (GCE) electrode (GCE/PAni/Ag) can be successfully used for the assay of sulfur containing compounds such as BT, DBT and 4, 6-DMDBT in petroleum samples.
- Full Text:
- Date Issued: 2019
Development of spunlaced nonwoven filters from PAN, PPS and PI fibres for industrial use
- Authors: Maduna, Lebo
- Date: 2019
- Subjects: Textile fibers -- Mechanical properties , Nonwoven fabrics --Technological innovations Textile fibers, Synthetic -- Mechanical properties
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/32610 , vital:32266
- Description: The aim of this work was to produce filter fabrics suitable for high temperature and other conditions encountered in coal power plants using the spunlacing manufacturing technique. Polyacrylonitrile (PAN), polyphenylene sulfide (PPS) and polyimide (PI) fibres being combined suitable for this purpose, each at three aerial density of (440, 500 and 560 g/m2) and each at three water jet pressures of (60, 80 and 90 bars) were produced. The effect of changing these on the fabric air permeability, tensile strength and filtration properties were investigated and optimized. For this purpose, the Box-Behnken experimental design (BBD) was considered the best and therefore used. The PPS/PI fabrics were found to consistently have the highest air permeability, tensile strength and filtration performance, followed by the PPS fabrics and the PAN fabrics. As could be expected, an increase in area weight and water jet pressure generally resulted in a decrease in air permeability irrespective of the fabric types, this being due to the increased number of fibres and therefore greater fibre surface area and entanglement respectively. For fabric tensile strength, the effects of varying fabric area weight and water jet pressure were not so straight forward. For cross direction (CD) an increase in water jet pressure resulted in an increase tensile strength whereas in the machine direction (MD) there was a decrease when the water jet pressure was increased. The filtration efficiency and dust holding capacity of the fabrics were found to be around 96% and 211g/m2, respectively, with the exception of the PPS (500 g/m2 80 bar) fabrics. Increasing the amount of dust being fed to the fabric during each loading cycle, it caused an increase in pressure drop, as the fabrics became increasingly clogged forming a cake layer.
- Full Text:
- Date Issued: 2019
- Authors: Maduna, Lebo
- Date: 2019
- Subjects: Textile fibers -- Mechanical properties , Nonwoven fabrics --Technological innovations Textile fibers, Synthetic -- Mechanical properties
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/32610 , vital:32266
- Description: The aim of this work was to produce filter fabrics suitable for high temperature and other conditions encountered in coal power plants using the spunlacing manufacturing technique. Polyacrylonitrile (PAN), polyphenylene sulfide (PPS) and polyimide (PI) fibres being combined suitable for this purpose, each at three aerial density of (440, 500 and 560 g/m2) and each at three water jet pressures of (60, 80 and 90 bars) were produced. The effect of changing these on the fabric air permeability, tensile strength and filtration properties were investigated and optimized. For this purpose, the Box-Behnken experimental design (BBD) was considered the best and therefore used. The PPS/PI fabrics were found to consistently have the highest air permeability, tensile strength and filtration performance, followed by the PPS fabrics and the PAN fabrics. As could be expected, an increase in area weight and water jet pressure generally resulted in a decrease in air permeability irrespective of the fabric types, this being due to the increased number of fibres and therefore greater fibre surface area and entanglement respectively. For fabric tensile strength, the effects of varying fabric area weight and water jet pressure were not so straight forward. For cross direction (CD) an increase in water jet pressure resulted in an increase tensile strength whereas in the machine direction (MD) there was a decrease when the water jet pressure was increased. The filtration efficiency and dust holding capacity of the fabrics were found to be around 96% and 211g/m2, respectively, with the exception of the PPS (500 g/m2 80 bar) fabrics. Increasing the amount of dust being fed to the fabric during each loading cycle, it caused an increase in pressure drop, as the fabrics became increasingly clogged forming a cake layer.
- Full Text:
- Date Issued: 2019