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Purification of lactic acidChow, Sidney Hsin-Huai January 1962 (has links)
No description available.
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The metabolism of linolenic acidRandolph, Patricia Murphy. January 1949 (has links)
LD2668 .T4 1949 R33 / Master of Science
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The investigation of an organic metabolite of Penicillium pinophilumCh'eng, Kwang Ling. January 1950 (has links)
LD2668 .T4 1950 C54 / Master of Science
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Studies on 3-Hydroxyanthranilic acid oxidase.Cox, Malcolm Charles Leslie January 1967 (has links)
Thesis submitted for the degree of Master of Science at the University of the Witwatersrand, Johannesburg, South Africa. / WHSLYP2017
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A review of legislative and safety requirements for running the titanium-production pilot plant at Anglo ResearchYumba, Nomsa 07 May 2009 (has links)
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.
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The effect of ascorbic acid supplementation on the absorption of iron from some vegetable staplesSayers, Merlyn Herbert January 2015 (has links)
No description available.
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Robust sequence alignment using evolutionary rates coupled with an amino acid substitution matrixNdhlovu, Andrew January 2014 (has links)
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).
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Remediation of acid mine drainage using prawn shellsTshikovhi, Fhatuwani Precious January 2018 (has links)
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
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Chemical impacts from acid mine drainage in a dam ecosystem: an epilimnion and sediment analysisOlsen, Kirstin Addison Aleksander January 2016 (has links)
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
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Evaluation of humic acids as potential acid catalysts for transalkylationSkhonde, M P 27 March 2006 (has links)
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.
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