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Item Open Access Struktuur en sintese van fenoliese metaboliete uit rooibostee (Aspalathus linearis)(University of the Free State, 1992) Rabe, Charlene; Steenkamp, J. A.; Ferreira, D.; Burger, J. F. W.Rooibostee is eie aan Suid-Afrika aangesien slegs die Sederbergstreek in die Kaap die ideale klirnaat vir die kweek daarvan het. Hierdie unieke tee het 'n kenrnerkende rooibruin kleur en 'n delikate, geurige srnaak wat wereldwyd al hoe gewilder word. Groen rooibosplante moet verwerk word (sien 1.2.2.3) om die gewenste organoleptiese eienskappe (kleur, geur en smaak) te ontwikkel. Die kondisies waaronder verwerking plaasvind, bevoordeel die vorming van gewenste of ongewenste verbindings met gevolglike toenemende of afnemende kwaliteit van die produk. Kennis van die chemiese samestelling van rooibos voor verwerking, die geskiktheid daarvan as substraat vir oksidases en die chemiese samestelling na verwerking, kan lig werp op chemiese veranderinge tydens oksidasie. Sodoende sal prosesaanpassings op 'n chemiese grondslag gemaak kan word. In die huidige ondersoek, is klem op die fenoliese inhoud van verwerkte rooibostee gele. Die ondersoek bet tot die isolasie van verskeie bensoe- en kaneelsure, asook flavone, flavonole, flavonolglikosiede, C-glikosidiese flavone, 'n dihidrochalkoon en 'n C-glikosidiese flavanoon gelei. Soos uit die literatuurstudie sal blyk, kan die fisiologiese aktiwiteit van rooibostee waarskynlik aan die teenwoordigheid van sekere geYsoleerde verbindings toegeskryf word (sien 2.2 en hoofstuk 4).Item Open Access Amphiphile-coated magnetic iron oxide nanoparticles for the extraction of contaminants from the aqueous media(University of the Free State, 2023) Mzinjani, Viwe; Azov, V. A; Langner, E. H. G.The availability of clean water to the community/ society is becoming a huge problem for its ecosystem. These toxic contaminants come from surface and subsurface water systems such as dams, rivers, and oceans that are eluted from industrial, domestic, agricultural, and recreational activities. Both organic and inorganic contaminants are found in these water systems in high concentrations, which put aquatic life at tremendous risk and the environment in general. Thus, the need for synthetic materials that can be used to solve this ongoing problem of water contamination is becoming an obvious research goal that needs urgent attention. Nanomaterials such as nanoparticles are currently being investigated as a tool to remove various contaminants in wastewater. Nanoparticles are very small particles with sizes ranging from 1 to 100 nm. Depending on their type, these nanomaterials may demonstrate various unique properties, such as strong catalytic activity, superparamagnetism, quantum confinement, and extremely high surface-to-volume ratios. In this project, the high surface-to-volume property was explored during the adsorption of methylene blue dye in spiked water samples. Magnetic iron oxide nanoparticles were chosen because of their magnetic susceptibility and most availability of iron metal on earth, making them cheaper materials since they can be prepared from cheap iron precursors. Magnetite NPs were prepared using the co-precipitation method, where iron precursors of Fe²⁺ and Fe³⁺ were dissolved in de-ionized water and ammonium hydroxide was used as the precipitating agent under an inert atmosphere. Better adsorption capacities of these nanoparticles can be achieved by functionalizing them with different organic and inorganic molecules. In this study, mono-alkyl phosphate esters of varying alkyl chain lengths were synthesized and used to functionalize the as-synthesized magnetite NPs to render better affinity towards organic dyes (Figure 1). The as-prepared magnetite NPs were characterized using techniques such as TEM, SEM, FTIR, EDS, and PXRD, and the organic functionalization molecules were characterized using NMR (¹H, ¹³C, and ³¹P), FTIR, and mass spectrometry. These characterization techniques confirmed the successful synthesis of the nanoparticles and mono-alkyl phosphate esters of varying alkyl chain lengths. TEM and SEM micrographs showed close to spherical shapes of the prepared nanoparticles with particle diameters ranging from 12 – 16 nm for bare Fe₃O₄ NPs and 17 – 22 nm for functionalized NPs. Comparable particle size was also obtained from the PXRD results using the Scherrer equation (eq. 3.1) where a particle size of 13 nm was obtained. PXRD characteristic peaks confirmed the inverse spinel structure of the Fe₃O₄ NPs. The presence of iron (Fe) and oxygen (O) in the EDS results confirmed the formation of the magnetite nanoparticles and the presence of carbon (C) and phosphorus (P) on the coated nanoparticles confirmed the successful coating of the Fe₃O₄ NPs. FTIR, NMR, and MS results showed comparable results to those found in the literature.Item Open Access Synthesis of aromatic monopyrrolo-tetrathiafulvalene derivatives with variable degree of π‐conjugation(University of the Free State, 2021) Mncwangi, Sibusiso Nicko; Azov, V. A.Tetrathiafulvalene (TTF, 1) and its derivatives have attracted much interest and found widespread applications in molecular, supramolecular and materials chemistry.⁽¹⁾ Monopyrrolo‐tetrathiafulvalenes (MPTTF, 59) possess more extended π–system in comparison to the parent TTF 1, better π–stacking capability and, therefore, they are capable of forming stronger charge‐transfer complexes with molecular acceptors.⁽²⁾Item Open Access Chemical analysis and evaluation of a homemade pest control mixture used by a local farmer from Maloti-A-Phofung municipality of the Afromontane region in the Free State(University of the Free State, 2022) Sebotsa, Maria Mojabeng; Molefe, N. F.; Mosoabisane, M. F. T.The indigenous community of the Afromontane region has developed and adopted strategies for survival to reduce diseases and eliminate ticks and pests on crops at a lower cost. Biopesticides are efficient in eradicating various plant pests, affordable, quickly biodegradable, with multiple mechanisms of action, freely available supplies, and low toxicity to non-target organisms. The phytochemical composition of different plants is thought to be responsible for their various modes of action. Synthetic pesticides are expensive for small-scale farmers in undeveloped regions like the Afromontane region. Investigating agrochemical alternatives will benefit small-scale farmers who cannot access these due to their high cost. This study aims to analyse and evaluate the effectiveness of homemade pest control used by a small-scale farmer in the Afromontane region. The homemade pest control mixture used by local farmers was collected, then sequentially extracted and sonicated using hexane, chloroform, ethyl acetate, methanol and water. The extracts were screened for active compounds by phytochemical analysis and characterized using ultraviolet-visible (UV-Vis) spectroscopy, Fourier-Transform Infrared Spectroscopy (FTIR), and liquid chromatography-tandem mass spectrometry (LC-MS/MS. Biological testing was used to examine for antibacterial and antifungal activities. Saponins, phenolic compounds, and terpenes were found in all of the extracts after phytochemical analysis of the samples. Through using FTIR spectroscopy, the functional groups of the extracts were detected while UV/Vis spectroscopy identified the presence of chromophore at a region of 220-300 nm. LCMS/MS was performed to dereplicate the analyte components with a focus on their collision induced dissociation (CID) spectra. LC-MS/MS and molecular networking enabled annotation of metabolites active in the different extracts of the homemade pesticide. Based on the connectivity of the molecular network, the homemade pest control molecular networking nodes were grouped into five clusters (1–5). Cluster 1 consists of features annotated as flavonoids, cluster 2 corresponds to compounds of the alkaloids and flavonoids, cluster 3 corresponds to amino acids and alkaloids, cluster 4 consists of fatty acids and alkaloids and cluster 5 consists of features annotated as isoflavonoids. The annotated compounds exhibited various characteristics; some were insecticidal, while others showed antimicrobial activities. The antibacterial and antifungal properties of the sequential and ultrasonic extracts were examined using microdilution. Among the tested extracts, chloroform sequentially and sonicated extracts, methanol sequentially and sonicated extracts showed the best antibacterial activity with the MIC values of 0.09-0.195 mg/ml. The antibacterial activity for sequential chloroform extract showed the best activity against all the bacterial strains, with MIC values ranging between 0.098-0.39 mg/ml. Most of the extracts tested were ineffective against the fungal strains for antimitotic activity. Only a sonicated methanol extract showed the best antifungal activity. The sonicated methanol extract showed good activity (0.39-0.78 mg/ml) against Candida albicans, C. vulgaris and Trichophyton mucoides. In the case of water extracts, no activity was observed in the gram-negative bacteria and antifungal activity. The growth of Fusarium culmorum was suppressed by the sequence water extract and sonicated hexane extract. The current study's phytochemical and annotated compounds revealed that homemade pest-control bioactive compounds such as saponins, terpenoids, alkaloids, isoflavonoids and amino acids have antimicrobial properties against a variety of pathogens. Overall, the findings indicate that the mixture contains phytoconstituents that are effective against plant pathogens and capable of killing insect pests.Item Open Access Thermal fractionation and properties of different PE/wax blends(University of the Free State, 2005-12) Hato, Mpitloane Joseph; Luyt, A. S.The influence of paraffin wax type and content on the properties of its blends with HDPE, LOPE and LLDPE was investigated. Differential scanning calorimetry, thermal fractionation and surface free energy results were used to clarify the morphology of the blends. Melt-mixing of HOPE with wax gave rise to completely miscible blends for both 10 and 20 % wax contents. This miscibility must be the result of co-crystallization of the wax with HOPE. This fraction, however, melts at increasingly lower temperatures with increasing amounts of wax in the blend. This is probably the result of the formation of thinner lamellae in the presence of the wax. A wax content of 30 % gave rise to a partially miscible blend. Complete miscibility was observed for all the LLDPE/Wax B blends. This indicates cocrystallization of Wax B with LLDPE, which was also evident from the thermal fractionation curves. LLDPE/Wax A blends were, however, partially miscible for all wax contents. Melt mixing of LOPE with Wax A gave rise to a partially miscible blend for all wax contents investigated, while complete miscibility was observed for the 90/10 w/w LOPE/Wax B blend, but not for the blends containing higher Wax B contents. The main fraction of LLDPE, however, melted at increasingly lower temperatures with increasing amounts of wax in the blend. It is further clear from the thermal fractionation results that the presence of wax changed the crystallization behaviour of LOPE. All these observations were supported by the surface free energy results. Changes in the tensile properties are explained in terms of the miscibility and proposed morphologies of the different blends.Item Open Access Preparation and characterization of EVA-sisal fibre composites(University of the Free State, 2005-01) Malunka, Mamookho Elizabeth; Luyt, A. S.The main focus of this research project was on sisal fibre as organic filler and the effect of its content on the thermal and mechanical properties of EVA. Sisal is a promising reinforcement for use in composites on account of its low cost, low density, high specific strength and modulus, no health risk, easy availability in some countries and renewability. Ethylene vinyl acetate (EVA) copolymer has a broad range of industrial applications. Uncross-linked and cross-linked EVA and EVA-sisal composites were prepared and characterized. In this work we present and discuss the preparation and characterization of EVA-sisal fibre composites. All the results strongly point to grafting between EVA and sisal, even for samples prepared in the absence of DCP. Gel content results indicate increased cross-linking/grafting with increasing DCP and sisal contents. Grafting between EVA and sisal fibre is confirmed by the porosity and FTIR results. The SEM photomicrographs also support strong fibre-matrix adhesion in the EVA-sisal composites. Grafting, and to a lesser extent cross-linking of EVA, had an impact on the thermal and tensile properties of the composites, because cross-linking and grafting substantially influence the structure and morphology of the composites. The incorporation of sisal in the EVA matrix increases the composites' stiffness. The influence of DCP on the stiffness, however, depends on the amount of sisal in the composite. Elongation at break increases in the presence of DCP, but drastically decreases in the presence of sisal. For pure EVA, stress at break decreases with increasing DCP content, probably because of degradation. It also decreases when 10 % sisal is present in the EVA matrix, but increases for higher sisal contents. In the presence of sisal, increasing DCP content also increases stress at break. Cross-linking and grafting also had an impact on the surface free energy of the samples.Item Open Access Preparation and characterization of EVA-wood fibre composites(University of the Free State, 2006-04) Dikobe, Dorine Geneth; Luyt, A. S.Ethylene vinyl acetate copolymer (EVA) and wood fibre (WF) composites, compatibilized with ethylene-glycidyl methacrylate copolymer (EGMA) were investigated. The study is divided into two systems, i.e. EVA-WF (uncompatibilized composites) and EVNEGMA-WF (compatibilized composites). The composites were prepared and their mechanical, morphological and thermal properties were investigated and compared. Their 02 permeability and water absorption behavior were also studied. Results showed that EVA-WF composites have poorer mechanical properties and an unacceptable physical appearance, while EVNEGMA-WF composites showed improved properties. The reason for this is that the interfacial adhesion between EVA and WF is weak because of the difference in surface free energy of EVA and WF. This problem was overcome by the addition of EGMA to the EVA-WP mixture, which resulted in the formation of an EGMA-WF grafted product, and which provides an OH group that forms a hydrogen bond with -C=O on EVA, resulting in EVA/EGMA-WF composites with better properties, proving that EGMA can act as an effective compatibilizer for EVA and WF. The effect of WF particle size and content, as well as the effect of the amount of EGMA used in the composite, were thoroughly investigated. The proposed interaction mechanism for EVA-WF, and the reaction and interaction mechanism for EVA/EGMA-WF composites, supported by IR, are presented.Item Open Access The influence of oxidized paraffin wax on the physical properties of LLDPE/wax and LDPE/wax blends(University of the Free State, 2002-02) Mtshali, Thato Nicholas; Luyt, A. S.; Van Sittert, C. G. C. E.In this work, the characterization, thermal and mechanical properties of mechanically and extrusion mixed LLDPE/wax and LDPE/wax blends were investigated. Mechanically and extrusion mixed samples were melt pressed into sheets on which analyses were done. The samples were first characterized by using FTJR spectroscopy and GPC. From the FTJR results it was found that linking and degradation occurred. The GPC results showed that the molecular weight of the blends increased. Thermal analyses were done using DSC and TGA From the DSC analyses, it was found that at low wax content both wax and polyethylene (in the blend) are apparently miscible in both crystalline and molten states. At higher wax content phase separation was observed. It was also found that an increase in wax content has an effect on (a) lamellar thickness of the blends, (b) the degree of crystallinity of the blends and (c) thermal stability of the blends. The mechanical properties were determined with a tensile tester. An increase in wax content affects the yield points and the ultimate properties of the blends. It was found that elongation at yield and elongation at break decrease with an increase in wax content. Yield stress decreases for LLDPE/wax blends and increases for LDPE/wax blends. Stress at break decreases, except for the mechanically mixed LDPE/wax blends, which show an increase. Young's modulus of the blends increased with an increase in wax content.Item Open Access Thermal and mechanical properties of polymers filled with copper powder(University of the Free State, 2005-02) Molefi, Jonathan Andrew; Luyt, A. S.The aim of this study was to prepare LOPE-Cu and LLOPE-Cu composites containing different amount of copper, and to determine the morphology, surface free energy, thermal and mechanical properties, as well as thermal and electrical conductivities of the samples. The copper powder particle distributions were found to be relatively uniform at both low and high copper contents. There was cluster formation of copper particles at higher Cu contents, as well as the formation of percolation paths of copper in the PE matrices. The surface free energy results show an increase in the total surface free energy and its disperse part, but a decrease in the polar part of the surface free energy for the Cu-PE composites in comparison with pure PE. There was an initial increase, followed by a decrease in melting temperature of LOPE with increasing copper content. When the observed enthalpy was compared with the expected enthalpy, a higher enthalpy was observed in the presence of low copper contents. For LLOPE the melting temperatures did not change appreciably. Comparison of the observed and expected enthalpies also showed that there was very little increase in total crystallinity. The TGA results show that there was a general decrease in thermal stability with increasing copper content in both LOPE and LLOPE. For LOPE the elongation and stress at break slightly decreased with increasing copper content, while the decrease in the case of LLOPE was much more significant. Young's moduli of LLOPE and its composites had slightly higher values than those of LOPE and its composites, because LLOPE is more crystalline and therefore more stiff than LOPE. These values strongly decreased from the values for both pure LOPE and LLDPE to those of their composites containing 2 vol.% copper, after which the moduli slightly increased with increasing copper content. The thermal conductivities of the composites were higher than that of the pure polyethylene matrix for both LOPE and LLOPE. A linear increase in thermal conductivity was observed with an increase in filler content. The electrical conductivity of polyethylene-copper composites increased with increasing copper content in the composite for both LOPE and LLDPE. From these results the percolation concentration was determined as 18.7 vol.% copper for both polymers.Item Open Access Contribution to preparation of polymer conjugates containing ferrocene derivatives(University of the Free State, 2000-11) Nokwequ, Mbulelo Geoffrey; Bariyanga, J.; Neuse, E. W.Cancer is one of the major killer-diseases in the whole world. It is a well known fact that the causes of cancer vary from person to person, they include, inter alia, exposure to carcinogenic substances like smoking, heredity, chronic irritation of body areas like exposure to radiation[l]. The alleviation of this disease is now one of the major challenges in the medical world. To this end, many drugs have been synthesized with the aim of curing this disease. The most widely used is cisplatin and its derivatives and it is more recently that metallocenes have also been employed as anticancer drugs. Recent studies have also shown that anchoring such drugs to biodegradable polymers improves their activity[2]. In this study ferrocene derivatives containing a BOC (tert-butoxycarbonyl) protected polyamine which is susceptible to platination were synthesized with a view of anchoring these to a suitable carrier polymer. Ethylenediamine, propylenediamine, and diethylenetriamine were first protected using BOC. These protected polyamines were characterized using NMR (¹ H nuclear magnetic resonance) spectroscopy, F AB-MS (fast atomic bombardment mass spectroscopy), FTIR (Fourier transform infrared) spectroscopy, and EA (elemental analysis). The protected polyamines were then attached to the ferrocenemonocarboxylic acid using a well known coupling agent DCC (N, N'- dicyclohexylcarbodiimide). These ferrocene derivatives were also analyzed using techniques such as NMR, MS, FTIR, and EA and they were found to have the expected structures. In parallel to this, a carrier polymer exhibiting a carboxylic acid side chain was synthesized from a poly (ethylene oxide) diamine and characterized by NMR, FTIR, GPC (gel permeation chromatography), ES-MS (electrospray mass spectroscopy), and EA . This polymer was later found to be water-soluble and has a long shelf life. This polymer was tested for biodegradability by digesting it with two endopeptidase enzymes, namely papain and proteinase A at 37 °C. Changes in molecular weight distribution of this polymer were then followed. The polymer was found to be slowly biodegradable.Item Open Access The influence of types and amounts of wax on the thermal and mechanical properties of PE/Wax blends(University of the Free State, 2005-11) Mpanza, Highness Sebenzile; Luyt, A. S.The influence of three different waxes on the thermal and mechanical properties of lowdensity (LOPE) and linear low-density (LLDPE) polyethylenes was investigated. The samples were prepared through melt blending in a Brabender mixer. The thermal properties of the samples were determined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Surface free energy analysis was used to confirm the miscibility of wax with polyethylene. The tensile and flow properties of all the samples were determined and compared. The observations are discussed in terms of possible morphological changes when wax is mixed with polyethylene. The polymer-wax miscibilities differed with the type of wax and polyethylene used, and with the amount of wax mixed into the polymer. These miscibilities, and accompanying morphologies, had a strong influence on the flow properties, thermal stabilities and tensile properties of the corresponding blends. Based on my observations, Wax 2 may be regarded as the best processing agent for LOPE. Both Wax 1 and Wax 2 have a similar influence on the tensile properties of LOPE, but Wax 2 increases the melt flow rate more than Wax 1, which was specifically designed as a polyethylene processing agent. As far as thermal stability is concerned, the blends seem to be thermally more stable in the presence of Wax 1 than in that of Wax 2. Although Wax 3 improves the melt flow rate in a similar way than Wax 2, it has a strong negative impact on the tensile properties of LOPE. In the case of LLD PE, either Wax 2 or Wax 3 can be used. Wax 3 has the strongest influence on the melt flow rates of the blends, and it has the least influence on the tensile properties of LLDPE. It does, however, strongly reduce the thermal stability of LLDPE. Wax 2, on the other hand, has only a small influence on the thermal stability of LLDPE, but like Wax 1 it strongly increases the modulus. Again Wax 1, which was specifically designed as a polyethylene processing agent, seems not to be the best wax to use for this purpose.Item Open Access Influence of the presence and amount of metal nanoparticles on the thermal and mechanical properties of iPP/soft paraffin wax phase change materials for thermal energy storage(University of the Free State, 2014-12) Molaba, Mamohanoe Patricia; Luyt, A. S.Nanocomposites based on iPP and an iPP/wax phase change blend with Ag nanoparticles were studied. The aim of this study was to correlate the thermal and electrical conductivity, as well as dynamic mechanical properties, with the morphology of the samples prepared using quenching in ice water and slow cooling from the melt, as well as different nanoparticle contents. Morphological analysis of the iPP/Ag nanocomposites showed that the Ag particles were well dispersed in the polymer, and formed nucleation centres for the crystallization of iPP. In the iPP/wax/Ag nanocomposites they were also well dispersed, but in the wax phase in between the iPP spherulites. The extent of filler agglomeration increased with increasing filler contents in both iPP and the iPP/wax blend. The Ag particles, whether in the iPP or wax phase, had little influence on the crystallinities and melting temperatures of iPP samples, even at higher filler contents. The presence Ag particles in iPP had little influence on the modulus of the iPP, but the presence of both wax and Ag particles significantly improved the modulus of these phase change nanocomposites. The thermal and electrical conductivities of the samples more significantly improved when both wax and Ag were present. With increasing Ag particle contents in both iPP/Ag and iPP/wax/Ag, the thermal conductivities increased, but leveled off at higher filler contents, while the electrical conductivities continuously increased with increasing filler contents. The slowly cooled samples had higher crystallinities than the quenched samples and therefore the slowly cooled samples were more thermally conductive than the quenched samples.Item Open Access The effects of peroxide treatment on composites of linear low density polyethylene and short sisal fibre(University of the Free State, 2003) Mokoena, Moipone Alice; Luyt, A. S.; Krupa, I.; Djokovic, V.In this work sisal fibre (Agave sisalana) was used as reinforcement in LLDPE-sisal fibre reinforced composites. In recent years there has been an increasing interest in finding new applications for sisal fibre as reinforcement in composites. The inherent problem that sisal fibre is hydrophilic in nature and thus absorbs a considerable amount of water, poses a thread towards achieving good interfacial adhesion with hydrophobic thermoplastic materials. Thus it was necessary to consider treatment of the composites. Dicumyl peroxide (DCP) was used for this purpose. The influence of sisal fibre and DCP content on the thermal, mechanical and visco-elastic properties of LLD PE-sisal fibre composites was investigated. Results show a significant decrease in water absorption for the DCP treated samples, changes in the polymer melting behaviour as a result of the presence of sisal as well as cross-linking/grafting in the presence of DCP, and significantly improved stress and strain at break, especially at low sisal contents. The presence of sisal increases the tensile modulus, but DCP treatment does not seem to have much influence on this property. Stress relaxation reduces with increasing sisal content, but again DCP treatment does not seem to have much influence. Although not proved beyond any doubt, there are indications that peroxide treatment, especially at high DCP content, causes grafting between LLDPE and sisal, as well as degradation of LLDPE.Item Open Access Kinetic study of the crystallization of LLDPE and wax in LLDPE/wax phase change blends used for thermal energy storage(University of the Free State, 2014-12) Gumede, Thandi Patricia; Luyt, A. S.; Muller, A. J.The main purpose of this research was to kinetically study the influence of each component in an LLD PE/wax blend on the crystallization behaviour of the other component, and also to evaluate the effectiveness of wax as a phase change material when blended with LLDPE. Phase change materials are used to store and release energy through phase changes, be it melting and solidification processes or solid state phase transitions. Paraffin wax is one of a large number of phase change materials that store and release large amounts of thermal energy through melting and solidification. Since molten wax has a low viscosity, it is important to contain the wax in some medium. A lot of research has gone into the preparation and characterization of immiscible polymer/wax blends, in which the wax crystallizes separately in the amorphous phase of the polymer. These wax crystals can then melt and solidify without affecting the polymer, which should have a significantly higher melting temperature than the wax. It is, however, possible for some of the wax to be trapped in the amorphous part of the polymer, in which case this wax fraction will not be available for thermal energy storage, making the system less effective as a phase-change blend. The crystallization kinetics results described in this thesis showed that the overall crystallization rate of LLDPE decreased with an increase in wax content, due to the dilution effect of the wax. Although the wax crystallized faster when blended with LLDPE, it showed lower melting enthalpies indicating fewer wax crystals, which directly impacts on its effectiveness as a phase-change material for thermal energy storage. The results obtained by successive self-nucleation and annealing (SSA) indicated that LLDPE can be thermally fractionated, whereas the medium-soft paraffin wax was not susceptible to thermal fractionation because of its linear short chain hydrocarbons. It was also shown that the wax acts as a solvent for LLDPE inducing a 'dilution effect' without co-crystallization.Item Open Access Investigation of thermal and physical properties of crosslinked LLDPE/w ax blends in the presence of dibenzoyl peroxide(University of the Free State, 2002-01) Hlangothi, Shanganyane Perseverance; Luyt, A. S.; Krupa, I.In this work, the thermal and mechanical properties of uncross-linked and cross-linked LLDPE/wax blends were investigated. The mechanically mixed samples were melt-pressed into sheets, from which the analyses were done. The thermal analyses were determined using DSC, TGA, and melt flow extrusion plastometer. It was found that wax is apparently miscible with LLDPE in both the crystalline and molten states. It was also found that changes in wax and the cross-linking agent contents result in changes in (i) the degree of crystallinity of the blends, (ii) melting and cooling temperatures of the blends, and (iii) the thermal stability of the blends. The cross-linking of the blends induced by DBP significantly affects the mechanical properties. It was found that the ultimate properties of LLDPE/wax blends deteriorated in the presence of wax. Stress at break increased as a function of DBP content, whereas elongation at break decreased. The yield point properties also resulted in interesting changes as the concentrations of wax and DBP were varied. Elongation at yield increased with increasing wax content and decreased with increasing DBP content. It was further found that higher concentrations of wax improved Young's modulus of blends, while higher cross-linking efficiency showed the opposite.Item Open Access South African fish poisonous plants VI. Isolation and study of Saponins from Neorautanenia edulis C.A. SM.(University of the Free State, 1955) Labuschagne, Willem Adriaan; Groenewoud, P.The object of the present investigation was to extract and isolate the fish-toxic saponin present in the tuber and the aerial portions of Neorautanenia Edulis C.A. Sm. Various methods of extraction were attempted, and the best found to be that with hot 95% ethyl alcohol. Regarding the isolation of the saponin, it was found that the etherate formation with the alcoholic extract, proved to be the most satisfying. Various other methods were also tried, but none of them gave a fish-toxic saponin. Toxicity tests on fish were carried out, and the most toxic compound found to be that from the etherate formation, mentioned above. The toxic compounds were further purified by extraction with ethyl alcohol, extracting the saponin and leaving an insoluble material which was identified as cane sugar. Various methods of hydrolysis were attempted, but the saponin was resinified by the concentrated hydrochloric acid. The purest form of the toxic saponin obtained had a yellow syrupy nature. It was very toxic, to fish, but could not be hydrolised in order to identify it.Item Open Access New methodology for the biomimetic synthesis of Flavan-3,4-diols and derivatives(University of the Free State, 2019-06) Van Jaarsveldt, Jeanette; Bezuidenhoudt, B. C. B.; Van Tonder, J. H.Abstract not availableItem Open Access Rhenium(I) complexes and cancer: synthesis and characterisation of mono- and bi-metallic complexes(University of the Free State, 2019-04) Oosthuizen, Ursula; Visser, Hendrik G.; Schutte-Smith, MarietjieOrganometallic compounds such as Re(I) complexes showed to be toxic to a few cancer cell lines, but lack the property of being selective towards cancer cells for the use as novel chemotherapeutic agents. Toxicity tests are preliminary tests performed on different cell lines such as HeLa, HepG2 or PT45 to determine whether the compounds could be used as potential PDT (photodynamic therapy) agents. PDT is the administration of non-toxic drugs or dyes also known as photosensitizers (PS) to patients. The main aim of this studies were to synthesize two N,Nʹ-bidentate ligands, 1,10- phenanthroline-5,6-dione (phenO2) and 1,10-phenanthroline-5,5-diamine (phen(NH2)2) and this was done successfully with a yield of 52 % and 48 % respectively, as reported in Chapter 3. Re(I) tri- and dicarbonyl complexes with different monodentate ligands: PPh3, PTA and DAPTA were synthesized for the evaluation of their luminescent properties and are reported in Chapter 5. PhenO2 and phen(NH2)2 are used as bridging ligands for the formation of two dinuclear complexes, [NEt4][Re2(CO)6(phen(NH)2)Br2] and [Re2(CO)6(phenO2)Br2]. The N,Nʹ-bidentate ligand, 1,10-phenanthroline, were coordinated to the Ru(III) metal centre which formed the precursor that was used for the synthesis of new bimetallic complexes with a combination of Pt(II) and Re(I) metals. All the compounds were successfully synthesized and characterised by NMR, IR, UV/Vis and elemental analysis as reported in Chapter 3. The crystal structures of fac-[Re(CO)3(phen)(H2O)][NO3]∙1.5H2O (3), fac- [Re(CO)3(phen)(Br)] (4) and 5-amino-6-nitro-1,10-phenanthroline (phen(NH2)(NO2)) are collected and reported in Chapter 4. 3 and 4 crystallized in the P1� space group while phen(NH2)(NO2) crystallized in the Pbca space group. The Re-CO bond distances of 3 are within the range of 1.864(15) Å to 1.914(13) Å and 4 within the range of 1.902(9) Å to 1.934(7) Å. The Re-N bond distances for 3 is 2.178(8) Å and 2.180(8) Å and for 4 the Re-N distances is 2.183(6) Å. The bite angle of 3 is 76.5(3) ° and the bite angle of 4 is 75.8(2) °. The N-H bond distances of phen(NH2)(NO2) are 0.89(3) Å and 0.93(4) Å, while the N-O bond distances are greater than the N-H distances with bond distances reported as 1.244(3) Å and 1.241(3) Å. The angles between the O-N-O and H- N-H substituents are 120.0 °. Luminescent studies was performed on the Re(I) tri- and dicarbonyl complexes for the evaluation of their luminescent properties. The Re(I) tricarbonyl complexes with monodentate phosphine ligands, fac-[Re(CO)3(phen)(PPh3)][NO3], fac-[Re(CO)3(phen)(PTA)][NO3] and fac-[Re(CO)3(phen)(DAPTA)][NO3], showed to absorb electrons from a wavelength of 265 nm to 266 nm. Their molar absorptivity coefficient ranges from 11490 to 31185 M-1 cm-1 while their emission wavelengths is at 610 nm. The Re(I) dicarbonyl complexes with bis-phosphine ligands, cis-trans-[Re(CO)2(phen)(PPh3)2][NO3], cis-trans-[Re(CO)2(phen)(PTA)2][NO3] and cis-trans-[Re(CO)2(phen)(DAPTA)2][NO3] showed luminescent properties at excitation wavelengths of 616 nm, 610 nm and 610 nm respectively. cis-trans- [Re(CO)2(phen)(PTA)2][NO3] has the largest molar absorptivity coefficient (14465 M-1 cm-1) of the three dicarbonyl complexes. cis-[Re(CO)2(phen)(PPh3)(Cl)], cis- [Re(CO)2(phen)(PTA)(Cl)] and cis-[Re(CO)2(phen)(DAPTA)(Cl)], the three dicarbonyl complexes with a monodentate phosphine ligands, have smaller molar absorptivity coefficients than all of the Re(I) compounds. These compounds also have greater emission wavelengths ranging from 620 nm to 630 nm. Three novel bimetallic complexes, [Ru(phen)2(N,Nʹ-phenO2-O,Oʹ)-Re(CO)3Br][PF6]3, [Ru(phen)2(N,Nʹ-phenO2-O,Oʹ)-PtCl2][PF6]3 and [Re(CO)3(N,Nʹ-phenO2-O,Oʹ)-PtCl2]Br with yields of 25 %, 96 % and 98 % respectively, were synthesized to evaluate their cytotoxicity against HeLa and RPE-1 cell lines. [Re(CO)3(N,Nʹ-phenO2-O,Oʹ)-PtCl2]Br is the only complex that showed cytotoxic effects against the HeLa cell line with an IC50 value of 7.31 ± 0.07 μM.Item Open Access Recovery of platinum group elements from waste material(University of the Free State, 2019-06) Ngcephe, Ayanda Maria; Purcell, W.The aim of this study was to recover the platinum group elements (PGE) from recycled or waste material using hydrometallurgical techniques. The waste material that was investigated for the possible isolation of PGE is a spent automotive catalytic converter sample, ERM®-EBS504 which is a certified reference material for Pt, Pd and Rh. Surface analysis on the catalyst sample was performed using the scanning electron microscope coupled with energy dispersive X-ray spectroscopy (SEM-EDS) in order to identify the main components of the sample. However, the identification and quantification of the PGE using this technique was ineffective due to the concentrations of PGE in the catalyst sample which were below the detection limits of the SEM-EDS. Two types of dissolution processes, namely aqua-regia open-beaker dissolution and sodium peroxide (Na2O2) fusion were employed to try and achieve the total dissolution of the automotive catalytic converter sample for the complete and accurate characterisation of PGE using the inductively coupled plasma optical emission spectroscopy (ICP-OES). Aqua-regia dissolution offered partial digestion of the sample and percentage recoveries of 66.9(4) %, 63.9(8) % and 41(1) % were obtained for Pt, Pd and Rh respectively at 80 °C and after a reaction time of 180 minutes. On the other hand, sodium peroxide was able to oxidise all the metals in the catalyst sample to easily soluble oxidation states which allowed for the further dissolution of the sample in aqua-regia. However, challenges in PGE quantification with the ICP-OES were experienced due to unacceptable and unsatisfactory PGE recoveries which were attributed to spectral interferences caused by the excess Na ions introduced from the Na2O2 flux. The introduction of Sc (361.363 nm) as an internal standard compensated effectively for the spectral interference and excellent PGE recoveries were obtained, namely 100(1) % for Pt, 100(3) % for Pd and 103(2) % for Rh. These results were successfully validated in accordance with the criteria of the Internal Standards Organisation (ISO 17025). This method was found suitable and reliable for the quantification of PGE in the automotive catalyst sample at different separation stages. The complete digestion and characterisation of the automotive catalyst sample enabled separation studies of PGE in various aqueous solutions. The separation methods were firstly studied on artificial samples which emulated to a degree of the original composition of the dissolved automotive catalyst sample. Both solvent extraction and selective precipitation methods were investigated for the possible separation and purification of PGE. Trioctylphisphine oxide (TOPO) and 2- mercaptopyridide N-oxide sodium salt (NaPT) were employed as extractants while NH4OH and 8-hydroxyquinoline (oxine) were used as precipitants. Oxine was found to be highly selective towards the Pd in the solution precipitation in acidic solutions, resulting in the isolation of this element as a highly stable compound which was characterised using XRD, FT-IR, NMR and CHNS micro-elemental analysis. The selective precipitation of the non-precious elements in the presence of PGE using NH4OH was found time-consuming and inconclusive results were obtained for the PGE. Solvent extraction of PGE using TOPO was found very suitable for the extraction of PGE from chloride solutions. Various parameters which included HCl concentration, ligand concentration, type of diluent and type of stripping reagent were investigated in order to optimise the extraction and selectivity for PGE. An increase in HCl concentration suppressed the extraction of PGE by TOPO, while the degree of Pt extraction was unaffected by this variation. Maximum extraction of all the PGE was observed at 4 M HCl and at high TOPO concentrations. These results improved remarkably when kerosene and hexane were used as diluents. The presence of the non-precious elements interfered to some extent with the extraction of PGE with TOPO. However, various stripping reagents such as NH4SCN proved to be highly selective in the stripping of Pt from Pd, Rh and the non-precious elements, while 2 M HCl proved to be selective towards Rh. Solvent extraction with NaPT proved to be more selective and effective towards Pd. This allowed for the selective isolation of Pd from the PGE and from the non-precious elements. The Pd-mercaptopyridine complex was isolated and successfully characterised with XRD, FT-IR, NMR and CHNS micro-elemental analysis. These isolation methods were successfully applied to a dissolved and pre- concentrated catalyst sample, and Pt and Pd were successfully recovered with percentage recoveries of 87(4) % and 99(3) % respectively. However, the recovery of Rh using TOPO was unsuccessful, and this was attributed to the formation of the highly stable [RhCl6]3- in the presence of high chloride concentrations. The high chloride content in the solution were as a result of the formation and isolation of NaCl during the dissolution process which complicated the sample matrix, and thus the extraction process of PGE using TOPO. This method was also evaluated on a highly- concentrated rhodium waste solution which had been accumulated in the department, but proved to be ineffective. The recovery of Rh from this waste solution was achieved by the co-precipitation of the non-precious elements using oxine, resulting in Rh recovery of 80(4) % in the filtrate.Item Open Access Hydrometallurgical beneficiation of ilmenite(University of the Free State, 2017-07) Vilakazi, Amanda Qinisile; Purcell, W.; Nete, M.English: The aim of this project was to investigate the dissolution and possible separation of Ti and Fe in ilmenite using eco-friendly and economically viable procedures. Method validation was established with commercial salts such as FeCl3·6H2O and TiCl3 including Ti and Fe metal powders with high purity. The successful procedures were evaluated for the dissolution of ilmenite and subsequent separations of Ti and Fe in the mineral matrix. Dissolution techniques such as open-beaker acid digestion and flux fusion were evaluated. The separation techniques which were investigated include selective precipitation, solvent extraction and ion exchange. Analytical determinations were performed with inductively coupled plasma-optical emission spectroscopy (ICP- OES) while infrared spectroscopic (IR) analyses was used to characterize the Ti and Fe containing compounds. Acid dissolution was investigated with different mineral acids which included aqua regia, HCl, HNO3, H2SO4 and H3PO4. Analytical results showed good average recoveries ranging from 98(1) to 105.2(2) % Ti in TiCl3 and 100(4) to 103(2) % Fe in FeCl3·6H2O after these salts were dissolved in water. The dissolution of the Ti and Fe metal powders was investigated with aqua regia, HCl, HNO3, H2SO4 and H3PO4 and only H2SO4 and H3PO4 successfully dissolves the metal powders and excellent Ti and Fe recoveries of 103.6(5) and 105.2(6) % Ti with 103(2) and 103(2) % Fe were obtained. The dissolution of ilmenite with acid digestion yielded 38.39 % TiO2 and 45.25 % Fe2O3 with H2SO4 and 34.79 % TiO2 and 19.50 % Fe2O3 in H3PO4 with clearly pointed to incomplete sample dissolution. Flux fusion using NH4·HF2, KF, K2S2O7, Na2CO3, LiBO2, Na2B4O7 and phosphate mixture (Na2HPO4/NaH2PO4·H2O) as fluxes was also investigated. Only the borates (LiBO2 and Na2B4O7) and the phosphate flux mixture (Na2HPO4/NaH2PO4·H2O) indicated complete ilmenite dissolution. The quantitative results obtained after the flux fusion method (borates and phosphate), were compared with the non-destructive SEM-EDS semi-quantitative results. Comparative results were obtained for Ti, Mg, Mn and Al with some difference observed in the Fe quantities that were recovered. The separation of Ti and Fe in the ilmenite was further investigated using only the phosphate flux method. Selective precipitation using NaTPB/phenantroline was unsuccessful with both Ti and Fe precipitated in solution. However the use of only NaPT resulted in the complete precipitation of Fe (99.60(1) %) while Ti remained in solution (103(1) %). Separation using solvent extraction indicated that Fe was preferentially isolated with 100 % Fe and 0.00 % Ti and thus achieving a complete separation using NaPT in different organic solvents. Separation of Fe and Ti using the MIBK/NaPT and 1-octanol/NaPT combinations indicated a selective extraction of Fe into the MIBK and 1- octanol with 95.9(3) to 103(3) % Fe and 0.0 to 24(9) % Ti obtained in the organic phase using HCl, H2SO4 and H3PO4, depending on the acid concentrations. Separation factors were calculated to in the range of 1.7 to 8.6 x 107. Solvent extraction using kerosene/TOPO and MIBK/acacH systems indicated a selective extraction of Fe into the organic phase (0.8(1) to 22(6) % Ti and 2(2) to 99.0(8) % Fe in kerosene, 0.7(2) to 7(2) % Ti and 22.5(2) to 100(2) % Fe in MIBK) with separation factors of 1.4 x 102 to 3.3 x 105 in kerosene and 23 x 100 to 1.6 x 105 in MIBK in HCl matrix. The separation of Ti and Fe with strong and weak basic ion exchange resins (Amberlite IRA-900, Amberlite IRA 402, Dowex 1x4 ion exchange resin, weak basic Dowex Marathon WBA and Dowex 66 free base) indicated the successful separations with Ti the strongly retained species during elution with H3PO4 solution. Fe recoveries of 96(1) to 103.46(1) % were obtained for the weak anionic resins using 3.0 and 5.0 M H3PO4 as eluent. The strongly retained Ti was eluted with 5.0 M HCl with recoveries of 99.1(1) to 103(4) %. Recoveries were generally poor with the use of strong anionic exchange resins for both Fe and Ti resins (62(2) to 74(5) % for Fe and 68(4) to 84(3) % for Ti). The separation factor (α) for strong and weak anionic resins were in the range of 1.4 (Fe/Ti) to 6.7 (Fe/Ti) in 3.0 to 10.0 M H3PO4.