Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017. / While bioleaching is a proven technology for the efficient recovery of base metals from sulphide minerals, its sustenance is dependent on the continuous availability of ferric ion, Fe3+, in soluble form, in the bioleach liquor. However, the solubility of ferric ion is low at higher pH that it tends to precipitate, resulting in the formation of ferric ion precipitates. The formation of ferric ion precipitates in bio-hydrometallurgy decreases the leaching efficiency by trapping the leached metals in solution through an adsorption mechanism which is not well understood. Although the surface properties of the precipitate could be linked to its metal adsorption properties, there has not been a detailed study that gives any indication or explanation of the adsorption mechanism. Therefore, the aim of this study was to investigate the effect of initial pH on the surface properties of ferric ion precipitate and relate this to the adsorption characteristics of the precipitate for desired metals. Biooxidation experiments catalysed by Leptospirillum ferriphilum were conducted in a CSTR with a working volume of 1L. The biooxidation experiments were conducted at pH values of 1.3, 1.5, 1.7, 1.9 and 2.2 at a constant temperature of 35 0C for 14 days. The recovered precipitates were characterized by X-ray diffraction, elemental analyses, SEM, particle size distribution (PSD) and zeta potential. Zeta potential measurements were conducted to investigate what role initial pH plays in modifying the precipitate surface charge and what role the surface charge of each precipitate plays in the nature of adsorption of copper ions onto the precipitate surface. The amount of copper adsorbed onto the precipitate was quantified by the magnitude of the change in surface charge after adsorption experiments. Quantification results showed that the amount of ferric ions precipitates formed increased from 4.31g to 13.26g with an increase in initial pH (from 1.3 to 2.2). The results also showed that significant precipitation of ferric ion occurred during the exponential phase while insignificant precipitation was observed during the stationary phase.

M.Tech. (Extraction Metallurgy) / For many decades, carbon nanotubes (CNTs) have been used as adsorbents for the removal of pollutants from wastewaters because of their unique properties such as inert surface, resistance to acid and base environment, rigidity and strength. Herein is a report of application of functionalised CNTs on the adsorption of metal ions from aqueous solutions and mine leachates. The CNTs were first synthesised in-house, purified, functionalised and characterised with various characterisation techniques: FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy, TEM (Transmission Electron Microscopy), EDS (Energy Dispersive Spectroscopy), Raman Spectroscopy, TGA (Thermal Gravimetric Analysis) and BET (Brunauer-Emmet-Teller). Together, these techniques gave substantiation for structure, surface and chemical modification of the synthesised moieties. After characterisation, the functional groups were attached to the walls of the tubes and this implies successful functionalisation...

M.Sc. (Chemistry) / Polymer nanocomposites are a new class of composites in which at least one dimension of the particles dispersed in the polymer matrix is in the nanometer range. Recently, different types of zeolite minerals, either natural (Clinoptilolite, chabazite, modernite) or synthetic (A-type, X-type, Y-type) are being employed as particulate fillers into the polymer matrix. Owing to their unique ion exchange phenomenon, zeolites have been widely studied as heavy metal adsorbents, but very few researchers have focused on the sorption of heavy metal ions on zeolite-filled polymer nanocomposites...

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The study was conducted to investigate the effects of: (i) varying the level of supply of the heavy metals iron, manganese, copper and zinc. (ii) varying the ratio between different pairs of metals in the medium. In particular the iron:manganese and zinc:copper ratios were studied. Initially the two fungi Aspergillus niger van Tieghem, (variety and strain) and Penicillium notatum Westling, were used. Penicillium notatum Westling was subsequently discarded, in favour of Penicillium glancum Link, because it did not sporulate freely in liquid culture. The fungi were grown in controlled nutrient solutions, and during the course of tho growth and development, the form and sporulation of the felts was noted. After a period of growth, the felts were removed, dried and weighed. The pH of the liquor was measured. the results were studied to determine the effect of varying levels of supply of the heavy metals, and of the varying heavy metal ratios in the culture solution. In the investigation of the effect of varying the level of supply of individual heavy metals, optimum concentrations were demonstrated for copper and manganese. Increaning the concentration of pairs of heavy metals cimultaneously was found to influence the appearance and degree of symptoms of toxicity. Cultures of Aspergillus and Penicillium were found to be able to tolerate concentrations of copper, in particular, considerably greater than the observed optima, when zinc was present in equal concentration. Citric acid, and subsequently ethylene- diaminetetra-acetic acid, were used as chelating agents, in order to prevent the precipitation of the metals in the culture solution during autoclaving. It was found that the use of chelating agents markedly reduced symptoms of toxicity. There was no conclusive evidence that the iron:manganese ratio in the culture medium was an important factor in the growth and development of cultures of Aspergillus and Penicillium. However there is considerable evidence that in cultures of Penicillium, the zinc:copper ratio in the medium is of some importance in the determination of the dry weight yield trends. This effect was not demonstrated in cultures of Aspergillus.

This study investigated the possible use of algal extracellular polysaccharide as a biosorbent for removal of heavy metals (copper and lead) from aqueous solutions as a means of bioremediation for metal containing effluents. This biopolymer has good biosorbent properties and a potential to provide a cost effective, selective and efficient purification system. A variety of environmental conditions induce the production of extracellular polysaccharides in algae. The production of exopolysaccharides by Dunaliella cultures was induced by nitrogen deficient conditions. A high ratio of carbon to nitrogen source considerably enhanced the polysaccharide release. Purified extracellular polysaccharide samples exhibited a monosaccharide composition consisting of the following sugars: xylose, arabinose, 2-0-methyl mannose, mannose, glucose and galactose. The relative abundance (%) of these sugars were calculated relative to xylose. The major sugar constituent was 2-0-methyl mannose, which was present at approximately 160% relative to xylose. The percentage relative abundance of other sugars was as follows: 18.8; 86.8; 85.3 and 22.3% for arabinose; mannose; glucose and galactose respectively. The identity of the various constituents were confirmed by mass spectrometry. The ability of Dunaliella exopolysaccharides to accumulate metals was investigated. The following parameters were studied because they affect metal uptake: solution pH, biomass concentration, temperature, time and metal concentration. The uptake of both copper and lead were pH dependent. However, metal uptake was not significantly affected by temperature. Kinetic studies showed that Dunaliella extracellular polysaccharides exhibit good bioremediation properties. Metal uptake was rapid. In addition, the exopolysaccharide has good metal binding capacity with an uptake capacity for lead of 80 mg/g from a solution containing initial lead concentration of approximately 40 mg/l. Competition studies revealed that the presence of a second metal in solution inhibits uptake of the other metal compared to uptake in single metal solution of that particular metal. The presence of lead inhibited the uptake of copper from approximately 65% in single metal solution to 10% in binary metal solution. The presence of copper also inhibited lead uptake, though not to the same extent. Higher concentrations of lead could not completely prevent removal of copper from solution and visa versa. The same was true for lead which could not be displaced by a four-fold concentration of copper. Instead, a certain percentage of copper was always removed showing that lead did not compete with copper for these binding sites. In conclusion it appears that, copper and lead bind to different sites on Dunaliella exopolysaccharides and that they exhibit selective or preferential removal of lead.

The removal of lead from aqueous solution and lead-acid battery manufacturing waste-water by the non-viable biomass of the water fern Azolla filiculoides was investigated in both batch and column reactors. The maximum lead uptake by the Azolla biomass at a pH value of approximately 5, was found to be 100 mg lead/g biomass from aqueous solution. Lead removal varied from 30% of the initial lead concentration at pH 1.5 to approximately 95% at pH values of 3.5 and 5.6. Lead removal from aqueous solution decreased to 30% of the initial lead concentration if the lead concentration was initially over 400 mg/l. At initial lead concentrations of less than 400 mg/l, percentage lead removal was found to be over 90% of the initial lead concentration. Lead removal remained at approximately 90% between 10°C and 50°C. Biomass concentration (4-8 mg/l) had little effect on lead removal. The presence of iron (Fe) and lead, copper (Cu) and lead or all three metal ions in solution at varying ratios to each other did not appear to have any significant effect on lead removal. Percentage lead, copper and iron removal from aqueous solution was 80-95, 45-50 and 65-75% respectively for the different multiple-metal solutions studied. No break-through points were observed for lead removal from aqueous solutions in column reactors, with initial lead concentrations of less than 100 mg/l at varying flow rates of 2, 5 and 10 ml/min. This suggested that flow rate, and therefore retention time, had little effect on percentage lead removal from aqueous solution, which was more that 95%, at low initial lead concentrations (less than 100 mg/l). At initial lead concentrations of 200 mg/l or more, an increase in flow rate, which equates to a decrease in column retention time, resulted in break-through points occurring earlier in the column run. Percentage lead removal values, from lead-acid battery efiluent in column systems, of over 95% were achieved. Desorption of approximately 30% and 40% of bound lead was achieved, with 0.5 M HNO₃ in a volume of 50 ml, from two lead-acid battery. Repeated adsorption and desorption of lead by the Azalia biomass over 10 cycles did not result in any decrease in the percentage lead removal from effluent, which strongly suggested that the Azalla biomass could be re-used a number of times without deterioration in its physical integrity, or lead removal capacity. No evidence of deterioration in the Azolla biomass's physical integrity after 10 successive adsorption and desorption procedures was observed using scanning electron microscopy. The Azolla filiculoides biomass was, therefore, found to be able to effectively remove lead from aqueous solution and lead-acid battery effluent repeatedly, with no observed reduction in it's uptake capacity or physical integrity.

A weak absorption in iodine vapour was reported by earlier workers to not obey Beer's Law, and was attributed to the dimer I₄. The ultraviolet spectrum of iodine vapour was reinvestigated in this study on a more quantitative basis. The extinction coefficients have been found to be independent of concentration of iodine (10 ̄⁵ to 10 ̄² M), pressure of an inert gas (up to 1 atm), and temperature (25°C to 220°C, except for the usual temperature broadening). The absorption continuum (maximum 2694±3 A; oscillator strength 4.98 ±. 05 x 10 ̄⁴) must be due to a transition in the free molecule to a repulsive state correlating with either ²P3/2 + ²P3/2 or ²P3/2 + ²P1/2 atoms. The identification of the upper state involved and of the mechanism allowing the transition to occur were not possible with the available evidence. The previous identification of I₄ in solution and of Br₄ in the vapour phase, determined by similar ultraviolet continua, are discussed in relation to the lack of evidence for I₄ in the vapour phase found in this study. / Science, Faculty of / Chemistry, Department of / Graduate

The transmission of neon line radiation through the positive column of a neon dc glow discharge has been measured. Six lengths of the column were used and a graphical comparison of the theoretical and experimental transmissions were made. This permitted a determination of the absorption coefficient of the gas, for the case of Doppler-broadened spectral lines. The relative transition probabilities for transitions with the same lower level were obtained from the values of the absorption coefficients. Radial variation of the density of absorbing atoms and the presence of isotopes in the column were taken into account. The relative intensities of several pairs of spectral lines emitted by neon gas excited by a pulsed electron beam have been measured. The neon was at a low pressure (.1 mm Hg) and excited for a short time (200 nsec) to suppress self-absorption of the emitted radiation. The relative transition probabilities for lines with the same upper level were determined from the intensity measurements. A weighted averaging technique was used to connect the relative transition probabilities of the absorption and emission measurements and a complete set of relative transition probabilities was obtained. The probabilities were placed on an absolute scale using the results of a lifetime measurement recently made by van Andel /17/. / Science, Faculty of / Physics and Astronomy, Department of / Graduate