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LD2668 .T4 1949 R33 / Master of Science

LD2668 .T4 1950 C54 / Master of Science

Thesis submitted for the degree of Master of Science at the University of the Witwatersrand, Johannesburg, South Africa. / WHSLYP2017

Anglo Research is due to commission a novel pilot plant for the manufacturing of titanium metal from ilmenite ore. The process requires the use of hydrofluoric acid, a very toxic chemical, in large volumes. A health and environmental study and legislative requirements of the process were thus required before commencing with the plant design. Metallurgical processes have resulted in some degree of environmental impact, from water, air and soil pollution. A prominent example is acid mine drainage, which pollutes ground water. It is therefore important to ensure that proper steps are taken in minimising or mitigating negative environmental effects when developing new process routes. Hydrofluoric acid (HF) is classified as extremely toxic. This acid is very aggressive physiologically because of the fluoride ion which penetrates the skin and robs the bone tissue of calcium. Because of the hazardous nature of HF, the following legislations were reviewed: o Hazardous Substances Act 15 of 1973 o Occupational Health & Safety Act of 1993 o National Road Traffic Act 93 of 1996: Chapter VIII o National Environmental Management Act 107 of 1998 o Environmental Conservation Act 73 of 1989 HF has been used in many other industrial applications including manufacturing of fluorocarbons and other chemicals, aluminium manufacturing, petroleum alkylation and uranium purification. Steps should be taken to minimise exposure to hydrofluoric acid in areas where there is a likelihood of worker exposure. Control measures include, but are not limited to, elimination/substitution and process modification, isolation, engineering controls, administrative controls, and use of personal protective equipment and hazard communication. HF is corrosive to most metals and materials of construction suitable for HF include fluoropolymers and other metal alloys such as nickel based alloy 400. Every design aspect of the plant must be done in a way that minimises the environmental and worker exposure to HF. Once safety of the plant design has been extensively reviewed, the pilot plant can then be built. The success of this campaign will be based not only on the achievement of process and product specification, but also on whether it was run without any incidents.

No description available.

Selective pressures at the DNA level shape genes into pro les consisting of patterns of rapidly evolving sites and sites withstanding change. These pro les remain detectable even when protein sequences become extensively diverged. It has been hypothesised that these patterns can be used as gene identi ers. A common task in molecular biology is to infer functional, structural or evolutionary relationships by querying a database using an algorithm. However, problems arise when sequence similarity is low. The problem is that the algorithm produces numerous false positives when highly conserved datasets are aligned. To increase the sensitivity of the algorithm, the evolutionary rate based approach was reimplemented and coupled with a conventional BLOSUM substitution matrix to produce a new implementation called BLOSUM-FIRE. The two approaches are combined in a dynamic scoring function, which uses the selective pressure to score aligned residues. Analysis of quality of alignments produced, revealed that the new implementation of the FIRE algorithm performs as well as conventional algorithms. In addition, the Evolutionary rate Database (EvoDB), which is a compilation of evolutionary rate pro les of all the members of the PFAM-A protein domain database has been developed. The EvoDB database can be queried using FIRE to infer protein domain functions. The utility of this algorithm and database was tested by inferring the domain functions of the Hepatitis B X protein. Results show that the BLOSUM-FIRE algorithm was able to accurately identify the domain function of HBx as a trans-activation protein using EvoDB. The biological relevance of these results was not validated and requires further interrogation; however, these proteins share vital roles in viral replication. This study demonstrates the utility of an evolutionary rate based approach and demonstrates that such an approach is robust when coupled with an amino acid substitution matrix yielding results comparable to conventional algorithms. EvoDB is a catalogue of the evolutionary rate pro les and provides the corresponding phylogenetic trees, PFAM-A alignments and annotated accession identi er data. The BLOSUM-FIRE software and user manual including the EvoDB at le database and release notes have been made freely available at www.bioinf.wits.ac.za/software/fire. The BLOSUM-FIRE algorithm and EvoDB database present a tier of information untapped by current databases and tools. / A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in ful lment of the requirements of the degree of Master of Science (Medicine).

A research dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2018. / ABSTRACT Acid mine drainage (AMD) is a serious global problem, particularly focusing on the Witwatersrand Basin, where most abandoned gold mines constituting mine waste containing pyritic rocks exist and leach sulfuric acid into surrounding waters as effluent containing trace elements like Fe, Co, Cu, Ni, Mg, Zn, Ca and U. Using currently available treatment technologies, it would be costly to remediate the approximately 3,000 miles of streams affected by AMD in Johannesburg hence probing a need for further research and new technology development. Therefore, this research explored the possibility of using prawn shells which contain a deacetylated form of chitin with a buffer capacity for use as a polluted mine water adsorbent. The effect of adsorption parameters such as contact time, absorbent dosage, initial pH, initial uranium ion concentration, competing anions and competing cations were investigated. An optimum adsorption of uranium(VI) of 92% was achieved using 1000 mg adsorbent dosage achieved optimum removal efficiency at pH 3, room temperature and 15 mg L-1 after 6 h equilibration time. The kinetics, isotherms followed pseudo second-order and the Freundlich models. The thermodynamic parameters for the adsorption of uranium onto prawn shells showed that the process proceeded in an exothermic nature, that is, adsorption capacity of uranium decreased with an increase in temperature. The desorption studies performed using HNO3 as an eluent gave efficiency of 19 ± 0.01% for 0.5 mg L-1, 37 ± 0.09% for 1 mg L-1 and NaHCO3 desorption capacity of 77.0 ± 0.01% for 0.5 mg L-1, 93.2 ± 0.05% for 1 mg L-1 and 99.7 ± 0.02% for 2 mg L-1, respectively. Consequently, NaHCO3 was found to be a good reagent for the desorption of uranium. The adsorption capacity was observed to be 0.17 mg g-1. At high concentrations the competing species showed an insignificant effect as uranium adsorption reached 97%. In all the experimental conditions, the speciation of uranium was determined using the PHREEQC geochemical modelling code. For instance, negatively charged U-carbonate complexes (e.g. UO2(CO3)22-) were predicted, explaining the potency of NaHCO3 as a desorbent for uranium. In the presence of competing ions, the speciation of uranium did not change significantly and hence the maintenance of elevated xv adsorption. Overall, the results of the study demonstrated that prawn shells are effective for the recovery of UO22+ ions, making them ideal for potential application for the remediation of uranium in liquid waste. Keywords: Uranium; Adsorption; Prawn shells; Acid mine drainage; Modelling / EM2018

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016. / Acid Mine Drainage (AMD) can result in significant and permanent ecological, chemical and physical alterations to the receiving environment. In 2002 a major surface decant of AMD effluent first entered the Tweelopies River upstream of the Krugersdorp Game Reserve, near Johannesburg. Within the game reserve the Tweelopies River intersects the Charles-Fourie Dam. The function of this dam, as a a sink of dissolved AMD contaminants (sulfate and iron), in the contaminated river was investigated in this study between September 2013 and August 2014. A water mass balance approach was used to estimate fluxes of dissolved contaminants. Additionally, compositional changes in sediment chemistry (total Fe, S, Al, Mg, Ca, Cu, Ni, Pb, V, and Zn) were investigated in order to quantify the storage or accumulation of contaminants in the sediment, which would indicate the long-term mitigatory function of the dam. The accumulation of high concentrations of metals and non-metals in the sediment of the dam (including 121.0 g S.kg-1 and 34.7 g Fe.kg-1) indicate that the dam stored both total iron and sulfur (AMD constituents) in the long term. Assuming that there was an average sediment depth of 19.3 cm in the dam, it was estimated that 18 tons of total iron, and 5 tons of total sulfur were present in the sediments of the dam. Additionally, the mass balance indicated that in total the dam acted as a sink for both sulfate and iron (14 853 kg SO42- and 5.5 kg Fe respectively) between September 2013 and February 2014, when the pH of the Tweelopies River was circumneutral (pH 6.1 – 7.6). However, the storage of contaminants in the dam also allowed iron and sulfate to be remobilised from the species and compounds it was stored in in the dam over the 2013-2014 study period. This is the result of changes in the water quality between March and July, when the pH of the river was lower (pH 2.9 – 3.6) and both dissolved iron and sulfate were remobilised (18 219 kg SO42- and 210 kg Fe respectively). In total the dam remobilised sulfate and iron in the 2013-2014 study period (increasing the flux by 0.4% or 3 366 kg and 8.7% or 202 kg Fe respectively). The data collected indicate that pH is the primary driver governing the dam to act as a sink and also remobilise dissolved iron and sulfate from the species and compounds they are stored in in the dam. When the pH is low the dam remobilises AMD constituents and acts as a sink when the pH is circumneutral. Therefore, it is evident that continual neutralisation of the water limits the degree to which the dam remobilises dissolved contaminants from the species and compounds they were stored in and that maintaining a neutral pH in the river should be prioritised by management. Additionally, the concentrations of total Fe, S, Ni, Pb, and Zn in the sediments exceeded the maxima probable effect level for the protection of aquatic life (by 3, 69, 20, 1.6, and 4.9 times respectively). The accumulation of contaminants in the sediment have very likely had a long-term adverse impact upon biodiversity and may present challenges to future rehabilitation efforts. Future management plans should avoid high investment loss to short-term remediation efforts and rather take a long term approach that incorporates these findings. / LG2016

Doctor of Science in Engineering - Engineering / Transalkylation, a process of transfer of alkyl groups from one aromatic compound to another is carried out on acidic catalysts such as zeolites. The porous nature of zeolites is a prohibiting factor for transalkylation involving highly conjugated aromatic compounds. The study looks at the production of humic acids as well as their evaluation as potential acid catalysts for transalkylation. Optimisation of the production of humic acids was carried out through determination of a suitable coal type using air oxidation. Slurry phase oxidation was used to enhance and optimise coal oxidation and the production of humic acids. From the characterisations and test reactions carried out, humic acids do show some catalytic properties; however the study also showed that the strength of the acid sites is not strong enough to induce transalkylation reactions. Investigations of using humic acids as catalysts for other reactions such as oxidative dehydrogenation of ethylbenzene to form styrene, is recommended.