Magister Scientiae - MSc (Chemistry)

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Active neutralisation and amelioration of acid mine drainage with fly ash
(University of the Western Cape, 2009) Surender, Damini; Petrik, Leslie; Faculty of Science
Fly ash and AMD samples were characterised by standard analytical methods for selection of the test materials. Active treatment by means of mixing fly ash with AMD in beakers and a large tank at pre-determined ratios have shown that fly ash is capable of neutralising AMD and increasing the pH beyond neutral values, which optimises the removal of heavy metals and ions. The trend was: the more fly ash added the quicker was the reaction time and higher the pH values achieved. Iron was reduced by as much 99 % in beaker scale experiments via Fe(OH)3 precipitation at pH values >4.0. A 99 % decrease in aluminium concentration was observed which was attributed to the precipitation of primarily gibbsite and various other mineral phases at pH values >5.5. As the pH increases, sulphate is adsorbed via Fe(OH)3 and gypsum precipitation at elevated pH. Sulphate attenuation with fly ash was excellent, achieving 98 % attenuation with beaker scale experiments and 1:1 fly ash:AMD ratio. Sulphate attenuation with fly ash was comparable to membrane and ion exchange systems and exceeded the performance of limestone treatment. Except for the larger volumes of fly ash needed to neutralise the AMD, fly ash proved to be a feasible and cost efficient alternative to limestone treatment. Fly ash produced competing results to limestone concerning acidity removal and sulphate attenuation. The comparison highlighted the advantages of utilising fly ash in comparison to limestone and demonstrated its cost effectiveness. The results of this study have shown that fly ash could be successfully applied for the neutralisation of acid mine drainage (AMD) and effectively attenuate the sulphate load in the treated water. The critical parameters to this technology are the variations of chemical composition and mineralogy of fly ash, which could influence the pH, contact time of the neutralisation reaction, and the same is true if the AMD quality varies.
Active neutralisation and amelioration of acid mine drainage with fly ash
(University of the Western Cape, 2009) Surender, Damini; Petrik, Leslie
Due to the constraints being placed on water resources and a drive for major industries to recycle waste water, improved and cheaper water treatment technologies are being investigated. During mining, pyrite (FeS2), a mineral naturally occurring in the earth’s structure, becomes oxidised when exposed to oxygen and water, resulting in the release of hydrogen ions, sulphate ions and metal cations. Coal mining operations, located in one of the largest coalfields in the country, in Mpumalanga province, is a major contributor to the generation of acid mine drainage (AMD) and is estimated to produce 360 Ml/d after closure of the entire Mpumalanga Coalfields. Commonly applied chemically treatment processes for AMD involve the use of limestone to neutralise the AMD, however elevated sulphate concentrations persist in the neutralised water. Membrane and ion exchange technology are more successful in attenuating sulphate in AMD; however, they are often complex and have exorbitant capital and operating costs. Universally, fly ash has been applied for the treatment of AMD primarily in passive treatment systems. Passive treatment technologies require little or no operation and maintenance e.g. constructed wetlands and anoxic limestone drains. However, with specific reference to AMD treatment, passive treatment systems require long retention times and greater space as well as provide uncertain treatment efficiencies. Recent research has demonstrated the potential to apply fly ash in active treatment systems for AMD treatment and amelioration. Active treatment technologies make use of some chemical addition or advanced technology e.g. membrane technologies and ion exchange resins. Whilst active treatment technologies are often more expensive than passive treatment systems, active treatment occurs at a faster rate and treatment efficiencies are more controllable and effective. This study investigated the potential of fly ash to actively neutralise and ameliorate or improve the quality of AMD at beaker and large scale with special attention given to sulphate attenuation. The results of the investigation were compared to data of state-of-the-art treatment technologies, obtained from literature. These included chemical treatment, membrane treatment, ion exchange and biological treatment systems. A comparative study was conducted to ascertain the feasibility of fly ash versus the commonly used limestone treatment technology. Fly ash and AMD samples were characterised by standard analytical methods for selection of the test materials. Active treatment by means of mixing fly ash with AMD in beakers and a large tank at pre-determined ratios have shown that fly ash is capable of neutralising AMD and increasing the pH beyond neutral values, which optimises the removal of heavy metals and ions. The trend was: the more fly ash added the quicker was the reaction time and higher the pH values achieved. Iron was reduced by as much 99 % in beaker scale experiments via Fe(OH)3 precipitation at pH values >4.0. A 99 % decrease in aluminium concentration was observed which was attributed to the precipitation of primarily gibbsite and various other mineral phases at pH values >5.5. As the pH increases, sulphate is adsorbed via Fe(OH)3 and gypsum precipitation at elevated pH. Sulphate attenuation with fly ash was excellent, achieving 98 % attenuation with beaker scale experiments and 1:1 fly ash:AMD ratio. Sulphate attenuation with fly ash was comparable to membrane and ion exchange systems and exceeded the performance of limestone treatment. Except for the larger volumes of fly ash needed to neutralise the AMD, fly ash proved to be a feasible and cost efficient alternative to limestone treatment. Fly ash produced competing results to limestone concerning acidity removal and sulphate attenuation. The comparison highlighted the advantages of utilising fly ash in comparison to limestone and demonstrated its cost effectiveness. The results of this study have shown that fly ash could be successfully applied for the neutralisation of acid mine drainage (AMD) and effectively attenuate the sulphate load in the treated water. The critical parameters to this technology are the variations of chemical composition and mineralogy of fly ash, which could influence the pH, contact time of the neutralisation reaction, and the same is true if the AMD quality varies.
Advanced low temperature metal hydride materials for low temperature proton exchange membrane fuel cell application
(University of the Western Cape, 2010) Ntsendwana, Bulelwa; Lototskyy, Mykhaylo; Williams, M.; Dept. of Chemistry; Faculty of Science
Energy is one of the basic needs of human beings and is extremely crucial for continued development of human life. Our work, leisure and our economic, social and physical welfare all depend on the sufficient, uninterrupted supply of energy. Therefore, it is essential to provide adequate and affordable energy for improving human welfare and raising living standards. Global concern over environmental climate change linked to fossil fuel consumption has increased pressure to generate power from renewable sources [1]. Although substantial advances in renewable energy technologies have been made, significant challenges remain in developing integrated renewable energy systems due primarily to mismatch between load demand and source capabilities [2]. The output from renewable energy sources such as photo-voltaic, wind, tidal, and micro-hydro fluctuate on an hourly, daily, and seasonal basis. As a result, these devices are not well suited for directly powering loads that require a uniform and uninterrupted supply of input energy.
Advanced oxygen reduction reaction catalysts/material for direct methanol fuel cell (dmfc) application
(University of the Western Cape, 2014) Motsoeneng, Rapelang Gloria; Khotseng, L.; Modibedi, R.M.
Fuel cells are widely considered to be efficient and non-polluting power source offering much higher energy density. This study is aimed at developing oxygen reduction reactions (ORR) catalysts with reduced platinum (Pt) loading. In order to achieve this aim, monometallic Pd and Pt nanostructured catalysts were electrodeposited on a substrate (carbon paper) by surface limited redox replacement using electrochemical atomic layer deposition (ECALD) technique. Pd:Pt bimetallic nanocatalysts were also deposited on carbon paper. Pd:Pt ratios were (1:1, 2.1 and 3:1). The prepared mono and bimetallic catalysts were characterized using electrochemical methods for the ORR in acid electrolyte. The electrochemical characterization of these catalysts includes: Cyclic Voltammetry (CV) and linear sweep voltammetry (LSV). The physical characterization includes: scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) for Morphology and elemental composition, respectively. The deposition of copper (Cu) on carbon paper was done by applying a potential of -0.05 V at 60s, 90s and 120s. 8x cycles of Pt or Pd showed better electrochemical activity towards hydrogen oxidation reaction. Multiples of eight were used in this work to deposit Pt: Pd binary catalyst. Cyclic voltammetry showed high electroactive surface area for Pt24Pd24/Carbon-paper while LSV showed high current density and positive onset potential. HRSEM also displayed small particle size compared to other Pt:Pd ratios.
Amperometric biosensor systems prepared on poly (aniline-ferrocenium hexafluorophosphate) composites doped with poly(vinyl sulfonic acid sodium salt)
(University of the Western Cape, 2008) Ndangili, Peter Munyao; Iwuoha, Emmanuel; Baker, Priscilla; Dept. of Chemistry; Faculty of Science
The main hypothesis in this study is the development of a nanocomposite mediated amperometric biosensor for detection of hydrogen peroxide. The aim is to combine the electrochemical properties of both polyaniline and ferrocenium hexafluorophosphate into highly conductive nano composites capable of exhibiting electrochemistry in non acidic media; shuttling electrons between HRP and GCE for biosensor applications.
An investigation of the natural products composition of Porphyra capensis (a red seaweed)
(University of the Western Cape, 2017) Yalo, Masande Nicholas; Mabusela, Wilfred T.
Plants have been widely used in traditional medicine for a number of ailments, among which may be included infectious diseases such as colds, influenza, chicken pox, TB, etc. as well as lifestyle diseases such as diabetes and cancer. Seaweeds have also been shown to contribute to the maintenance of health through their nutritional and medicinal properties and recently, a great deal of interest has developed towards the isolation of bioactive compounds from marine sources due to their numerous health benefits. Furthermore, marine algae are valuable sources of structurally diverse metabolites with scientifically proven therapeutic claims. Chemical constituents of red seaweed, Porphyra capensis was investigated in this present study along with subsequent brine shrimp lethality assay analysis of the crude extracts. The compounds isolated from the plant were from the hexane (6) and butanol (2) extracts. These compounds were all isolated and purified by various chromatographic techniques, namely silica gel chromatography, Sephadex LH-20 gel as well as C18 reversed phase silica gel. The structures of the isolated compounds were analysed and characterised by NMR, GC-MS, ESI MS and FTIR spectroscopy. Eight compounds were isolated and identified as phytol, desmosterol, 9-eicosenoic acid, 5,8,11,14,17-eicosapentanoic acid, palmitic acid, methyl (E)-hexadec-9-enoate, glycerol and compound 1 (novel compound). All the compounds were isolated from Porphyra capensis for the first time. The hexane, butanol and methanol extracts were found to be non-toxic with the brine shrimp test LC50 value at least two times greater than ?g/ml.
The application of high capacity ion exchange absorbent material, synthesized from fly ash and acid mine drainage, for the removal of heavy and trace metals from secondary co-disposed process waters
(University of the Western Cape, 2005) Hendricks, Nicolette Rebecca; Linkov, V; Dept. of Chemistry; Faculty of Science
The objective of this study was to investigate the feasibility of the application of low cost high capacity inorganic ion exchange material, synthesized form collected fly ash and acid mine drainage solid residues, for the decontamination of secondary co-disposal process waters, with emphasis on investigating the processes governing the solid/solution interface.
The application of novel multinuclear catalysts derived from dendrimeric ligands in the polymerization and oligomerization of unsaturated hydrocarbons
(University of the Western Cape, 2007) Malgas, Rehana; Mapolie, S.F.; Dept. of Chemistry; Faculty of Science
G1 and G2 dendrimeric salicylaldimine ligands containing both substituted and unsubstituted aryl rings were synthesized via a Schiff base condensation of the appropriate salicylaldehyde and the peripheral amino groups of the corresponding G1 and G2 polypropyleneimine dendrimers. The new ligands were characterized using FTIR, 1H NMR and 13C NMR spectroscopy, elemental analysis and ESI mass spectrometry. The dendrimeric ligands were converted to multinuclear nickel complexes by reaction with nickelacetate. The metal complexes were characterized by FTIR spectroscopy, elemental analysis and ESI mass spectrometry.Some of the dendritic complexes were evaluated as catalyst precursors in the oligomerization of α-olefins such as ethylene and 1-pentene, using aluminium alkyls such as EtAlCl2 and modified methylaluminoxane (MMAO) as activators. All the dendrimeric catalysts evaluated are active in the oligomerization reactions. From the oligomerization results it was observed that there is a clear dendritic effect, in that both catalyst activity as well as selectivity are impacted by the dendrimer generation. In most cases it was observed that the second generation complexes show higher activity than the corresponding first generation complexes.The dendrimeric complexes were also evaluated as catalyst precursors in the vinyl polymerization of norbornene. In this case methylaluminoxane (MAO) were employed as an activator. Once again it was noted that a dendritic effect is operative, with second generation metallodendrimers having a higher activity than the first generation complexes.
Application of Sutherlandia flutescens in cosmetic skin industry (phytochemical fingerprinting and its activity against skin immune diseases.
(University of the Western Cape, 2019) Msebele, Bongiwe; Baker, Priscilla
Hyperpigmentation disorders such as melasma, freckles and black-pigmented spots on the surface of the skin are often a result of increased over production and accumulation of melanin pigments in the skin. In melanin biogenesis, tyrosinase is the key enzyme that catalysis the synthesis of melanin, thus the most effective and easiest way to reduce melanin synthesis is by inhibiting tyrosinase. There are a large number of reported tyrosinase inhibitors, their identification and isolation from natural sources is highly important because when natural tyrosinase inhibitors are identified in natural sources, their production is relatively low in cost. Tyrosinase inhibitors are highly sought in the cosmetic industry because of their skin – whitening effects. Most common used tyrosinase inhibitors are kojic acid (KA), arbutin, hydroquinone and ascorbic acid. However, these inhibitors have side effects and lack clinical efficiency. These facts led us to focus our research work on the exploration of natural tyrosinase inhibitors. Due to the therapeutic potential of medical plants researchers are not only concerned with validating ethnopharmacological usage of plants, but also with identification, isolation and characterization of bioactive components. Sutherlandia frutescens and Psoralea aphylla are both examples of indigenous fynbos species, which have been applied by indigenous people for the benefit of their medicinal properties.
Biological properties of selected flavonoids of rooibos (Aspalathus linearis)
(University of the Western Cape, 2007) Snijman, Petra Wilhelmina; Green, I.R.; Joubert, E.; Gelderblom, W.C.A.; Dept. of Chemistry; Faculty of Science
Bioactivity-guided fractionation was used to identify the most potent antioxidant and antimutagenic fractions contained in the methanol extract of unfermented rooibos (Aspalathus linearis), as well as the bioactive principles for the most potent antioxidant fractions. The aim of this thesis was to investigate whether the same flavonoids are responsible for both the potent antioxidant and antimutagenic properties of unfermented rooibos.
Boron-doped Diamond Sensors for the Determination of Organic Compounds in Aqueous Media
(University of the Western Cape, 2010) Hess, Euodia; Baker, Priscilla; Iwuoha, Emmanuel; Dept. of Chemistry; Faculty of Science
In electrochemical oxidation treatment of wastewater, the electrode material is an important parameter in optimizing oxidative electrochemical processes, since the mechanism and products of several anodic reactions are known to depend on the anode material. The electrochemical oxidation of benzaldehyde, nitrobenzene and m-cresol on bare boron-doped diamond (BDD) electrode was investigated. Cytochrome c was then electrochemically immobilsed onto the functionalized BDD electrode by cyclic voltammetry. Oxidation and reduction reaction mechanism of each flavonoid was studied. There was one oxidation and reduction peaks for quercitin and catechin respectively, and two oxidation and two reduction peaks for rutin. The cytochrome c modified BDD electrode showed good sensitivity for all three flavonoids and low detection limits i.e. 0.42 to 11.24 M as evaluated at oxidation and reduction peaks, respectively.
Brine treatment using natural adsorbents
(University of the Western Cape, 2011) Mabovu, Bonelwa; Petrik, Leslie F.
Studies involving the use of natural clays such as bentonite, montmorillonite and natural zeolite clinoptilolite in water treatment have been reported. Researchers suggested cost effective processes, such as ion-exchange and adsorption for the removal of heavy metals from waste waters by using naturally occurring and synthetic materials. The current study investigated application of natural adsorbents in brine treatment. Brines are hypersaline waters generated in power stations and mining industries rich in Mg2+, K+, Ca2+,Na+, so,': cr and traces of heavy metals, thus there is a need for these brines to be treated to recover potable water and remove problematic elements. Natural adsorbents have been successfully used in waste water treatment because of their high surface area and high adsorptive properties when they are conditioned with acid or base. The natural adsorbents used in this study were obtained from Ecca Holdings company (Cape bentonite mine) Western Cape in South Africa, comprising bentonite clay and natural zeolite (clinoptilolite) and another clinoptilolite sample was obtained from Turkey. These adsorbents were investigated in their natural and pretreated form for removal of toxic elements in brine water. The pretreatment was aimed at removing Na+, K+, Ca2+, Mg2+ from the clinoptilolite as well as the bentonite and replacing these cations with the H+ cation to activate the materials. The cation exchange capacity (CEC) of natural zeolite from South Africa was found to be 2.14 meq/ g, Turkish Clinoptilolite was 2.98 meq/ g while South African bentonite was 1.73 meq/g. at 25°C using ammonium acetate (pH 8.2) method. Characterization of these natural adsorbents was done prior to pretreatment and after the treatment. ICP-AES analysis was used for determination of toxic elements in brines before and after sorption. The morphology of clays was characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (N2-BET) and Scanning electron microscopy (SEM) for confirmatory purposes and X-ray Fluorescent spectroscopy (XRF) was used for the composition analysis of the natural adsorbent. The results from batch experiments prior to pretreatment of the natural adsorbents showed that these natural adsorbents contained Mg2+, K+, Ca2+, Na+ in their structures as charge balancing cations, thus needed pretreatment to remove the cations. The natural adsorbents were pre-treated with 0.02M HCI. After the pretreatment of natural adsorbents it was possible to enhance the percentage removal of the major cations from brine, and the Na+ and Mg2+ removal achieved (86 % and 85% respectively) from brine was more than C02+ (70% ) the SC was the adsorbent one that gave highest removal of cations in the brines. Trace elements removal was high with Cu2+and Zn2+ being the highest of toxic elements in brine. The optimum contact for the toxic element removal was found to be 30 min for the Turkish clinoptilolite and 1 hr for the South African clinoptilolite and South African bentonite clay. Leaching of Ae+ and Si4+ during adsorption was also investigated and it was found that less than 1 ppm of A13+ and Si4+ were leached into the solution during adsorption experiments indicating that these materials were stable. The investigation of pH showed that natural adsorbents did not perform well at low pH of 4 and 6. The adsorbents were able to work efficiently at the natural pH of 8.52 of the brine solution. These results show that natural adsorbents hold great potential to remove cationic major components and selected heavy metal species from industrial brine wastewater. Heterogeneity of natural adsorbents samples, even when they have the same origin, could be a problem when wastewater treatment systems utilizing natural clinoptilolite and bentonite are planned to be developed. Therefore, it is very important to characterize the reserves fully in order to make them attractive in developing treatment technologies.
Brine treatment using natural adsorbents
(University of the Western Cape, 2011) Mabovu, Bonelwa; Petrik, Leslie F.; Dept. of Chemistry; Faculty of Science
The current study investigated application of natural adsorbents in brine treatment. Brines are hypersaline waters generated in power stations and mining industries rich in Mg2+, K+, Ca2+, Na+, SO4 2- , Cl- and traces of heavy metals, thus there is a need for these brines to be treated to recover potable water and remove problematic elements. Natural adsorbents have been successfully used in waste water treatment because of their high surface area and high adsorptive properties when they are conditioned with acid or base. The investigation of pH showed that natural adsorbents did not perform well at low pH of 4 and 6. The adsorbents were able to work efficiently at the natural pH of 8.52 of the brine solution. These results show that natural adsorbents hold great potential to remove cationic major components and selected heavy metal species from industrial brine waste water. Heterogeneity of natural adsorbents samples, even when they have the same origin, could be a problem when wastewater treatment systems utilizing natural clinoptilolite and bentonite are planned to be developed. Therefore, it is very important to characterize the reserves fully in order to make them attractive in developing treatment technologies.
Carbon dot – polythionine nanocomposite sensor for the remediation of antibiotics in water
(University of the Western Cape, 2022) Fakier, Ashiqa; Franke, Candice
Antibiotics are a necessary part of the world today where their main purpose is to counter bacteria and diseases. Antibiotics are used in many areas which include apiculture, domestic, livestock and medically. Since antibiotics are ingested regularly following excretion, they are present in sewage plants and the environment. Overconsumption of antibiotics (knowing and unknowingly) may lead to bacteria becoming used to those antibiotics and an antibiotic resistance is formed. The consumption of antibiotics becomes troublesome when resistances to certain antibiotics and when side effects are extremely harsh on patients.
Carbon supported aluminium trifluoride nanoparticles functionalized lithium manganese oxide for the development of advanced lithium ion battery system
(University of the Western Cape, 2017) Willenberg, Shane; Ross, Natasha
A novel lithium ion (Li-ion) battery cathode material has been investigated for potential mobile technology energy storage applications. I have successfully synthesized Lithium Manganese oxide (LMO), reduced Graphene Oxide (rGO) and Aluminium trifluoride (AlF3). The cathode coated nanocomposite was compiled of the aforementioned materials to give [AlF3LiMn2O4-rGO]. A single-phase spinel was observed from X-ray diffraction (XRD) studies with a high intensity (111) plane which indicates good electrochemical activity. No alterations to the crystal structure were observed after forming the composite nano-cathode material. Fourier transfer infrared (FTIR) spectroscopy showed the vibrational spectrum of LiMn2O4 with a with asymmetric MnO6 stretching confirming that the spinel was formed.
Carbon-carbon coupling reactions catalysed by palladium nanoparticles supported on the green alga Ulva armoricana
(University of Western Cape, 2018) De Bruin, Franklin Quelain; Antunes, Edith
The synthesis of nanomaterials, especially metallic nanoparticles, has attracted an enormous amount of interest over the past decade. They exhibit unique properties that allow the multiple applications in a variety of fields in science and technology. Their applications are limited by the efficiency and control of their synthesis to produce nanoparticles of certain size and shape. With ever mounting concern for the environment, a great amount of research has recently been extended to synthetic procedures that are carried out with limited or no toxicity to human health and the environment. One method involves the use of biological (or biogenic) materials for nanoparticle synthesis. This method is particularly attractive due to the fact that it is a relatively cheap, simple and environmentally friendly method compared to that of conventional chemical methods of synthesis.
Catalyst Coated Membranes (CCMs) for polymerelectrolyte Membrane (PEM) fuel cells
(University of the Western Cape, 2010) Barron, Olivia; Ji, Shan; Dept. of Chemistry; Faculty of Science
The main objective of this work it to produce membrane electrode assemblies (MEAs) that have improved performance over MEAs produced by the conventional manner, by producing highly efficient, electroactive, uniform catalyst layers with lower quantities of platinum electrocatalyst. The catalyst coated membrane (CCM) method was used to prepare the MEAs for the PEM fuel cell as it has been reported that this method of MEA fabrication can improve the performance of PEM fuel cells. The MEAs performances were evaluated using polarisation studies on a single cell. A comparison of polarisation curves between CCM MEAs and MEAs produced in the conventional manner illustrated that CCM MEAs have improved performance at high current densities (>800 mA/cm2).
Cation-exchanged zeolites-A prepared from South African fly ash feedstock for CO2 adsorption
(University of the Western Cape, 2015) Muvumbu, Jean-Luc Mukaba; Petrik, Leslie F.; Musyoka, Nicholas
In South Africa coal combustion constitutes up to 90 % of the country’s energy need. This coal combustion activity is known to contribute to the amount of about 40 % of the total CO2 atmospheric emissions worldwide that are responsible for global warming effects. In addition burning of coal generates a large quantity of fly ash which creates environmental pollution since only a small portion of it is currently used in some applications. In order, on one hand to mitigate and sequester CO2 and on the other hand to reprocess fly ash and reuse it, this study focuses on developing new technologies with cost-effective and less energy consumption in the domain of CO2 capture and sequestration. CO2 has priority attention for being the largest contributor to global warming. Various techniques have been used for CO2 capture and sequestration, such as aqueous alkylamine absorption or adsorption onto a solid adsorbent such as zeolites. In this study NaA zeolite adsorbent was hydrothermally synthesised from South African fly ash. This fly ash based NaA zeolite was then used as starting material to prepare LiA, CaA, and MgA zeolite catalysts via ion-exchange for comparative CO2 adsorption capacity. A systematic design of the ion-exchange procedure was undertaken at either 30 °C or 60 °C for a contact time of 1 hr, 4 hrs, and 8 hrs with 1, 2 and 3 consecutive exchanges in each case in order to determine the optimum conditions for loading each cation exchanged. The adsorption of CO2 on the ion- exchanged fly ash based zeolite-A catalysts was carried out at 40 °C similar to the temperature of flue gas since the catalysts obtained in this study were also prepared with a view to their applications in flue gas system. The CO2 desorption temperature ranged between 40-700 °C. All materials used in this study, starting from fly ash feedstock, werecharacterized using various techniques to monitor the mineral and structural composition, the morphology, surface area and elemental composition and the adsorption capacity. The techniques included mainly Fourier transform infra-red, X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, Energy dispersive spectroscopy, X-ray fluorescence, Temperature programmed desorption.The results obtained from both Fourier transform infra-red and the X-raydiffraction spectroscopy for samples exchanged at either 30° C or 60 °C showedlower crystallinity in CaA and MgA zeolite samples. This decrease in crystallinitymainly affected the D4R (0-20° 2) and was demonstrated in the study to beinversely proportional to the increase of the atomic radius of cations (Li+ > Mg2+ >Ca2+). In the Fourier transform infra-red, the vibration band at 677 cm-1 attributedto the extra-framework cation, also proportionally increased with the decrease ofthe atomic radius or size of the cations, and was intense in LiA zeolite samples.
Cesium hydrogen sulphate and cesium dihydrogen phosphate based solid composite electrolyte for fuel cell application
(University of the Western Cape, 2004) Naidoo, Sivapregasen; Linkov, Vladimir; Vaivars, Guntars; Dept. of Chemistry; Faculty of Science
A new high temperature solid electrolyte composite was developed, with CsHSO4 and CsH2PO4 as the proton conducting material in composition with PTFE and SiO2 to enhance the solid electrolyte composites mechanical strength and conductivity. Conductivity measurements for CsHSO4 and CsH2PO4 and composites thereof, in temperature ranges 0 to 180 oC and 0 to 250 oC respectively, were carried out. The composites with different concentrations PTFE and silica were tested for stability in a enhanced conductivity. hydrogen atmosphere and different degrees of humidity. The CsHSO4 was seen to exhibit a super protonic phase change at temperatures between 132 – 140 C and CsH2PO4 around 230 C. The presence of the PTFE proved to be a stabilizing factor in the reduction of water re-adsorption once the membrane had been dried during thermal conductivity analysis. According to supporting data in the literature it has been found that composites including silica could be influenced by the hydrophilicity and specific surface area of the silica. In the composite system employed it was shown by impedance analysis the presence of two semi-circles in the Nyquist representation for the enhanced conductivity due the presence of silica.
Characterization and chemical speciation modelling of saline effluents at Sasol Synthetic Fuels Complex-Secunda and Tukuta power station
(University of the Western Cape, 2009) Nyamhingura, Amon; Petrik, Leslie F.; Dept. of Chemistry; Faculty of Science
The study shows conclusively that brine composition and concentration is highly variable at these South African power utilities and processes such as RO, contact with ash and CO2 ingress can have an impact upon the overall brine quality. Aq.QA was found to be a more accurate tool for classifying waters according to dominant ions than Stiff diagrams but Stiff diagrams still have the superior advantage of being a mapping tool to easily identify samples of similar composition as well as quickly identify what has been added or what has been removed from a water stream. Chemical speciation could identify effluent streams where CO2 dissolution had taken place.

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