The removal of colour from effluent after dyeing of cellulosic fibres is a major problem due to the difficulty in treating such effluents by conventional treatment methods. Cellulosic fibres of a specific shade (colour) are produced by reacting the fibres with a mixture of reactive dyestuffs, salt and auxiliary chemicals. Reactive dye exhaustion to the fibre is about 80% i.e. 20% remains in the effluent; this is hydrolysed dye which cannot be reused for dyeing. The exhausted reactive dye bath together with first rinse represents 6 to 30 L effluent/kg of fabric and most of the colour and salt. The total water consumption for reactive dyeing ranges from 25 to 100 L effluent/kg fabric while the water consumption from total textile finishing ranges from 30 to 150 L effluent/kg fabric. Thus the concentration of the dye and salts are 5 times more concentrated when obtained at source. The use of activated carbon adsorption for the removal of colour from exhausted dyebath for the re-use of water, salt and energy has been studied. Four different commercial reactive dye chemistries and associated auxiliaries were tested and commercial activated carbon was used as an adsorbent. Different temperatures (20°C to 100°C), pH values (acidic, neutral, basic) and salt concentrations (50 g/L to 100 g/L) were evaluated and the high adsorption results were achieved when using high temperature, low pH (acidic) and high salt concentrations. The Freundlich adsorption parameters were obtained for activated carbon adsorption capacity and adsorption bond strength between reactive dyes and activated carbon. The overall removal of the reactive dye shades was 36% to 53% (based on colour in the effluent), salt recovery was about 94% to 97%, the water recovery ranged from 14% to 25% and energy savings of 17% to 32% could be achieved. Column adsorption test were performed at different temperatures and flowrates. The saturated activated carbon was regenerated and repeatedly used by elution with 1.0 M NaOH. The regenerated carbon was found to be effective up to 3 cycles of operations. A column system for treatment of reactive dyes using activated carbon was designed. The outcome of this study showed that treatment of reactive dyebath with activated carbon adsorption technique can allow re-use of water, salt and energy, thus enabling environmental improvements with a savings in salt, energy, water and treatment costs. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.

Thesis (Ph.D.)-University of Natal, Durban, 1987.

Abstract available in pdf file.

In this dissertation, we studied the generation of squeezed states induced by a timedependent interaction and the in uence of temperature on the strength of the squeezing in a condensed matter model. The model studied comprised two quantum harmonic oscillators, with a time-dependent, non-linear coupling between them. The in uence of the thermal bath on the non-equilibrium dynamics of the model was represented in terms of non-Hamiltonian thermostats and a collection of independent harmonic oscillators with Ohmic spectral density. The equations of motion were studied in the Wigner representation, which introduces a phase space description for the model. The representation of the system in quantum phase space allowed us to investigate the di erence between purely classical evolution and the relative importance of quantum corrections with respect to the dynamics. The dynamics was studied by means of computer simulation techniques. The numerical simulation of the non-equilibrium statistical mechanics of both time-dependent and non-linear interactions allowed us to investigate conditions beyond those in recent literature [1, 2]. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Persistent organic pollutants and heavy metals are released into the environment through different anthropogenic processes. They are of concern because they tend to bioaccumulate in the food chain and show adverse health effects ranging from acute to chronic toxicity. These pollutants need therefore to be monitored to conserve the environment. Conventionally, samples are sent to a laboratory for analysis by standard techniques such as chromatography and spectroscopy. Although these conventional techniques display high accuracy and low detection limits, they are expensive, require the use of highly trained personnel and tedious sample preparation. In comparison, electrochemical methods such as biosensors are sensitive, low cost and simple to operate. In this thesis, the determination of selected persistent organic pollutants (polybrominated diphenyl ethers, polybrominated biphenyls and polychlorinated biphenyls) and heavy metals (Cd, Pb and Cu) was achieved by the use of amperometric inhibition biosensor based on horseradish peroxidase (HRP) immobilized on the surface of platinum-polyaniline modified electrode. Polyaniline (PANI) film was electrochemically deposited on the platinum electrode surface. The film was characterized by cyclic voltammetry and spectrometric techniques. The CV results proved that the PANI was electroactive and exhibited a fast reversible electrochemistry. Characteristic Ultraviolet–Visible and Fourier Transform Infrared features of the polymer film were identified. They revealed that PANI film synthesized in this study is the conductive emeraldine salt. Horseradish peroxidase based biosensor was constructed by electrostatic attachment of the enzyme onto Pt-PANI electrode surface. Spectrometric and cyclic voltammetric results indicated that the immobilized HRP retained its bioelectrocatalytic activity towards the reduction of hydrogen peroxide. The Pt/PANI/HRP biosensor showed a linear response over a concentration range of 0.05 to 3.17 mM with a detection limit of 36.8 nM. Apparent Michaelis- Menten constant ( app M K ) was calculated as 1.04 mM. This implied that the HRP biosensor had a high affinity for H2O2. Furthermore, the fabricated biosensor showed high sensitivity, good reproducibility, repeatability and long-term stability. The Pt/PANI/HRP biosensor was applied to the determination of selected persistent organic pollutants and heavy metals. The latter was found to inhibit the HRP enzyme’s activity. The percentage inhibition of the investigated persistent organic pollutants decreases in the following order: 2,2´4,4´,6-pentabrominated diphenyl ether> 2-brominated biphenyl> 2-chlorinated biphenyl> 2,2´,4,5,5´-pentachlorinated biphenyl> 2,4,4´-trichlorinated biphenyl. In the case of heavy metals, the degree of inhibition of heavy metals was highest for Cd2+, followed by Cu2+ and then Pb2+. Kinetic study for the amperometric response to H2O2, recorded in the absence and presence of persistent organic pollutants and heavy metals revealed that for polybrominated diphenyl ethers, the inhibition process corresponded to a competitive type whereas for polybrominated biphenyls, polychlorinated biphenyls and heavy metals, it corresponded to the on-competitive type. The biosensor exhibited high sensitivity towards the determination of the metals and persistent organic pollutants as pollutants in real water samples, namely tap water and landfill leachate samples. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.

The growing significance of vanadium in medicinal inorganic chemistry is due to the diverse biological activities of its metal complexes, as elaborated in Chapter 1. These biological activities stem from the fact that vanadium is an essential trace element as well as its ability to form active pro-drugs under physiological conditions. To improve the bio-availability of these potential metallopharmaceuticals, the use of biologically relevant ligand systems such as heterocyclic ligands were considered. These chelators should provide the stability and the ability to promote absorption through cell-membranes. The techniques as described in Chapter 2 were employed to analyze and characterize the formulated heterocyclic ligands and their metal complexes. The attained research findings are mainly divided into two studies which involve the explorative coordination chemistry of two classes of ligands: 2-pyridylbenzimidazole (see Chapter 3) and 2-phenylsubstituted heterocyclics (see Chapter 4). An additional brief study is described in Chapter 5 which discusses the attempted coordination of a uracil Schiff base ligand. In Chapter 3, the coordination behaviour of Hpybz (2-pyridylbenzimidazole) towards vanadium in various oxidation states (i.e. +III/IV/V) was explored. The six-coordinate complex cis- [VVO2(Hpybz)(pybz)] (1) was isolated as the CH3OH.(H2O)2 hydrate from the reaction of NH4VO3 and Hpybz in aqueous methanol. The crystal structure shows that the vanadium is bonded to two cis-oxido ligands, and to the two bidentate ligands pybz and Hpybz. This combination of ligands confers six-coordination on the metal centre, which is a rare coordination number for a mononuclear dioxido complex of vanadium(V). From the reaction between Hpybz and VCl3 the cationic complex salt cis-[VIII(OH)2(Hpybz)2]Cl (2) was formed. The ligands in cis- [VIII(OH)2(Hpybz)2]Cl exhibits the same coordination behaviour as in 1, but instead of the dioxido moiety present in 1, two hydroxyl co-ligands are coordinated to the metal centre, with both chelator ligands neutral. Conductivity measurements in DMF affirmed that the compound is a 1:1 electrolyte. A novel binuclear mixed-valence oxidovanadium compound, (μ- O)[VVO(pybz)2.VIVO(Hpybz)(acac)] (3), was obtained from the reaction of Hpybz with VO(acac)2. ESR analysis illustrates paramagnetic behaviour typical of a type I dimer. The metal compound, VO(Hpbyz)2SO4 (4).H2O was isolated in a good yield from the reaction of two equivalents of Hpybz with vanadyl sulfate. Chapter 4 reports the isolation of oxidovanadium compounds with 2-phenylsubstituted benz(imidazole/othiazole/oxazole) chelators. The 2:1 molar reaction between NH4VO3 and 2- hydroxyphenylbenzothiazole (Hobs) led to the formation of a polynuclear vanadium(IV) complex, [VO(obs)2]n (1). The atmospheric oxygen-induced oxidation reaction of VCl3 and 2- hydroxyphenyl-1H-benzoxazole (Hobo) afforded a similar oxidovanadium compound, [VO(obo)2]n (2). A characteristic eight-line isotropic signal was observed in the ESR spectrum of 2 in DMF while, due to the poor solubility of 1, a singlet was attained upon analysis of the single crystals. A diamagnetic dioxidovanadium(V) complex, cis-[VO2(obz)py] (3) (Hobz = 2- hydroxyphenyl-1H-benzimidazole) was isolated from the reaction of NH4VO3 and Hobz in a methanolic solution. A broad singlet is found in the 51V NMR spectrum at -520.7 ppm for the d0-vanadium centre. The intra-ligand (π-π*) relaxations [466 nm for 1, 376 nm for 2 and 469 nm for 3] could be observed in the emission spectra which were obtained in anhydrous DMF. In an effort to synthesize a coordination compound of vanadium, the reaction of a heterocyclic ligand, 2-mercaptophenyl-1H-benzimidazole (Hsbz) with vanadyl sulfate resulted in an unexpected reaction product, [C26H20N4S2].[SO4].4H2O (4). In Chapter 5, the metal-induced cyclization of 5-amino-6-[(Z)-(2-hydroxybenzylidene)amino]- 1,3-dimethylpyrimidine-2,4-(1H, 3H)-dione (H3duo) by NH4VO3 resulted in the formation of a cyclized benzimidazole derivative, 8-(2-hydroxyphenyl)-1,3-dimethyl-1H-purine-2,6-(3H, 7H)- dione (1). The IR spectra of H3duo and its cyclized form are nearly identical where only minor shifts in the significant bands are observed. The molecular transformation was more evident when comparing the 1H NMR spectra of H3duo and 1. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2006. / Although the Bengal tiger, Panthera tigris tigris, appears on the IUCN Red Data List for endangered animals, very little information is available in the literature on the components of this animal's marking fluid. Scent marking is the main form of communication in all cat species. In some species, including the Bengal tiger, the liquid used for spraying is not pure urine, but is mixed with scent gland secretions. The objective of this study was to characterise the volatile components in the marking fluid of the Bengal tiger to achieve a better understanding of the semiochemical communication of this animal. The marking fluid of the tiger was characterised through the use of analytical techniques, such as gaschromatography, low resolution gas chromatography - mass spectrometry and retention time comparison. Homologous series of alkanes, alcohols, aldehydes, methyl ketones, carboxylic acids, γ- and δ-lactones, amides and lactams, as well as esters and nitrogen containing compounds, were identified. Of these identified compounds the unbranched alkanes, saturated alcohols, aldehydes, branched methyl ketones, saturated carboxylic acids and γ- and δ- lactones are commonly found in mammalian secretions. Compounds that aren't as common in their secretions are the methyl ketones, branched carboxylic acids, dimethyl esters of dicarboxylic acids and amides. The marking fluid contains a phthalic acid ester. Phthalic acid esters are used in the polymer industry and are nowadays found almost everywhere in nature. It is known that these pollutants have endocrine disrupting properties. The heat, humidity and wet conditions that are characteristic of the Bengal tiger's natural habitat makes it necessary for the tiger to make use of a fixative to prolong the life of the semiochemical message. The compounds and the concentrations in which these compounds are present in the urine and the lipid fraction of the marking fluid of the tiger was determined and compared to assess the fixative role of the lipids. This study has provided evidence that the lipid material has a greater affinity for the volatile organic constituents of the marking fluid and that it can therefore extend the lifetime of a semiochemical message left by the tiger.

Thesis (MSc)--University of Stellenbosch, 2004 / ENGLISH ABSTRACT: A variety of computational techniques are used to calculate structural, thermodynamic and transport properties of two specific Platinum Group Metal (PGM) complex systems. The first system consists of a PGM complex ([PdCl4]2-; [PtCl4]2-; [PtCl6]2- or [RhCl6]3-) with sodium counter-ions in a water solution at 30ºC and at a concentration of 0.106 mol/dm3. The second system under consideration is that of a PGM complex ([PdCl4]2-; [PtCl4]2-; [PtCl6]2- or [RhCl6]3-) with sodium counter-ions in a water solution in the presence of four poly (ethylene oxide) (PEO) chains at 30ºC and at a concentration of 0.013 mol/dm3. A conformational study of the two types of dihedral angles in a PEO chain (-C-O-C-Cand -O-C-C-O-) is performed and the extreme flexibility of the polymer is confirmed. Dihedral angle distributions of the two dihedral angles are calculated and explained in terms of the potential energy surface obtained from the conformational study. The solvation geometries of the PGM complexes are confirmed and the results are contrasted with those in the system where the polymer (PEO) is present. It is concluded that the effect of the polymer on the structure and degree of solvation is negligible. The free energy of solvation values of the PGM complexes are calculated to provide insight into their structural characteristics such as solvation shell volume and geometry. The structural and thermodynamic properties of the PGM complexes in solution are also used to explain the trends observed in the calculated diffusion coefficients. Comments are made on the accuracy of the calculated diffusion coefficients as well as the legitimacy of the mechanistic speculations which results from them. Suggestions regarding possible future improvements to the computational methods are made. / AFRIKAANSE OPSOMMING: Verskeie berekenings tegnieke is aangewend om die strukturele, termodinamiese en verplasings eienskappe van twee spesifieke Platinumgroep Metaal (PGM)-kompleks sisteme te bereken. Die eerste sisteem bestaan uit die PGM-kompleks ([PdCl4]2-; [PtCl4]2-; [PtCl6]2- of [RhCl6]3-) met natrium teenione in water by 30ºC en met ‘n konsentrasie van 0.106 mol/dm3. Die tweede sisteem bestaan uit die PGM-kompleks ([PdCl4]2-; [PtCl4]2-; [PtCl6]2- of [RhCl6]3-) met natrium teen-ione in water in die teenwoordigheid van vier poli-etileenoksied (PEO) kettings by 30ºC en met ‘n konsentrasie van 0.013 mol/dm3. ‘n Studie is gemaak van die konformasies van die twee soorte dihedrale-hoeke in ‘n PEOketting (-C-O-C-C- en -O-C-C-O-) en die insense buigbaarheid van die polimeer is hiermee bevestig. Die dihedrale-hoek-verspreidings van die twee tipes dihedrale hoeke is bereken en word verduidelik in terme van die potensiёle energie kromvlakke soos bereken tydens die konformasie analiese. Die geometrie van die solvasie van die PGM-komplekse is bereken en vergelyk met die sisteme waar die polimeer (PEO) teenwoordig is. Hieruit word afgelei dat die effek van die polimeer op die struktuur en graad van solvasie van die komplekse minimal is. Die vrye energie van solvasie van die PGMkomplekse is bereken met die doel om insig in te win oor die stukturele eienskappe soos byvoorbeeld die volume van die solvasie sfeer en die geometrie daarvan. Die strukturele en termodinamiese eienskappe van die PGM-komplekse in oplossing word ook gebruik om die neigings in die berekende diffusie koёffisiente te verduidelik. Opmerkings word gemaak aangaande die akkuraatheid van die berekende diffusie koeffisiente asook die geldigheid van die meganistiese spekulasies wat daaruit gemaak word. Voorstelle word ook gemaak rakende toekomsige verbeterings aan die reken tegnieke.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / Please refer to full text for abstract

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / A comprehensive, comparative structural study of gold(I), gold(II) and gold(III) compounds with the general formula [Aux(C6F5)y(tht)z] (tht = tetrahydrothiophene) was performed. The series of compounds included the unprecedented dinucleur gold(II) compound, tetrakis(pentafluorophenyl)bis(tetrahydrothiophene)digold(II), which could be prepared in a rational manner. This very unique compound represents the first example of an unbridged dinucleur gold(II) compound in which the gold(II) centres are not stabilised by chelating ligands. Formation of this compound was postulated to have taken place by radical pentafluorophenyl (pfp) ligand migration along with AuII–AuII bond formation. It may therefore be regarded as a rare example of labile behaviour by a generally inert pfp ligand. In addition to this compound, the crystal and molecular structures of the wellknown gold(I) and gold(III) precursor compounds, (pentafluorophenyl)(tetrahydrothiophene) gold(I) and tris(pentafluorophenyl)(tetrahydrothiophene)gold(III) were carried out and are described for the first time. The latter underwent a unique mononuclear ligand rearrangement (metathesis or disproportionation) reaction in solution to yield the novel rearrangement product, bis(pentafluorophenyl)bis(tetrahydrothiophene)gold(III)tetrakis- (pentafluorophenyl)gold(III). In all the complexes, the Au–C and Au–S bond lengths displayed a variation which appears to be dependent on the oxidation state of the central gold atom. Both of these bond types were found to descrease in the order Au(II) > Au(III) > Au(I)...