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Odour emissions resulting from reduced sulphur compounds in the kraft pulping industry are frequently found in dilute, high flowrate air streams that are costly to treat using incineration and thermal oxidation. Biofiltration, an air treatment method involving passing air through a packed bed of microorganisms, has emerged as a promising treatment strategy for these dilute waste gas streams. However, biodegradation of dimethyl sulphide (DMS) in biofilters is rather poor and is limiting the application of biofiltration to odour streams rich in DMS. Recently, our group has shown that co-treatment of DMS with methanol can increase DMS removal significantly. In this thesis, the effect of methanol on the microbiology of two biofilters treating DMS was explored. Microbial community analysis revealed that the addition of methanol led to a significant increase of up to an order of magnitude in the abundance of Hyphomicrobium spp. in a biofilter co-treating DMS and methanol compared to a biofilter treating DMS alone with no significant difference in the abundance of Thiobacillus spp. between the two biofilters. Further to the biofiltration experiments, the growth kinetics of Hyphomicrobium spp. and Thiobacillus spp. on DMS and methanol in an enrichment culture created from a biofilter co-treating DMS and methanol were studied. A specific growth rate of 0.099 h-1 and 0.11 h-1 was determined for Hyphomicrobium spp. and Thiobacillus spp., respectively, growing on DMS at pH 7, double the highest maximum specific growth rate for bacterial growth on DMS reported to date in the literature. As the pH decreased from pH 7 to pH 5, the specific growth rate of Hyphomicrobium spp. decreased significantly by 85% in the mixed culture while the specific growth rate of Thiobacillus spp. remained similar through the same pH shift. When methanol was used as a substrate, the specific growth rate of Hyphomicrobium spp. declined much less over the same pH range (up to 30%). These results suggest that addition of methanol to biofilters co-treating DMS and methanol can increase DMS removal rates by increasing the abundance of DMS-degrading Hyphomicrobium spp. at pH levels not conducive to high growth rates on DMS alone.

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The occurrence of hydrogen sulphide in the environment, the reasons for concern about the levels which may be present, particularly on off-shore installations, and methods for determining the gas in air are reviewed. The original aim of this project was to explain the reasons for the variations in the levels of naturally occurring hydrogen sulphide over the estuary of the Don at Aberdeen. The monitoring work required a reliable method: as the published methods were all problematical, much effort was expended in improving the Ethylene Blue method and investigating the range of trapping solutions. The final optimised method has been published (Analyst 1988, 113, 1635). An alternative method for standardising H2S in air gas mixes has also been developed and used on commercial samples. Microbiological studies have shown that sulphate-reducing bacteria were not present in the sediments of the Don estuary in 1988 (but were present in sediments from the Forth estuary) and further, that the Don sediments would not support growth of SRB's, which in part explains why there has been effectively no release of H2S from the estuary in recent years. Attempts have been made to correlate the H2S emission events with changes in river water quality over the last ten years, but no obvious clues have become evident.

M.Tech. (Minerals Engineering) / This report deals with the feasibility study of a novel concept whereby a lead sulphide concentrate and a solid reductant are reacted with a manganese ore at a temperature of approximately lOOO=C. The manganese oxides are reduced to their lower oxides, which, having a higher affinity for sulphur than lead. scavenge the sulphur from the lead sulphide. A manganese sulphide mane is formed. and liquid lead metal is tapped off. The manganese sulphide mane is then leached with sulphuric acid. After a purification step to remove the base metals from solution, the electrolyte proceeds to an electrolytic manganese metal or manganese dioxide facility where the manganese is recovered. The benefits of this process are fourfold: firstly, lead ores may be beneficiated locally; secondly, the separate and often lengthy processes for the recovery of lead and manganese are combined into a simplified process, thereby reducing the capital expense: thirdly, the Leadman process can be applied to any scale of operation: and fourthly, no 502 is produced. Details of the investigation included the following: a literature survey. a laboratory scale study where the operating conditions were narrowed down, a smelting campaign on a rotary kiln, a mineralogical study, a brief leaching study, a leach liquor purification step and a techno-economic assessment. This study has shown the technical and economical feasibility of the Leadman process. The lead and manganese recoveries were both approximately 93%, with good accountability of all the other elements of interest. Depending on the operating conditions, between 80 and 100 per cent of silver, originally in the galena, was recovered with the lead bullion. The purity of the lead metal produced was good with a lead content of approximately 97 per cent, and low levels of contaminants. It was also shown that the manganese matte produced is suitable for use as feed to an existing manganese electrowinning operation. The techno-economic assessment showed a return of R 3 118/t of Pb, compared with R 939/t and R 240/t for the conventional manganese and lead blast processes, respectively.

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Lead, nickel and cobalt dithiocarbamates complexes were synthesized using methanol and water as solvents. All complexes were refluxed at 60 °C, cooled at room temperature, washed with methanol to remove the impurities and dried under the fume hood. A combination of Fourier transformer infrared (FTIR), elemental analysis (EA) and thermogravimetric analysis (TGA) were used to characterize these complexes. There was shifting of bands from low to high frequencies of the dithiocarbamates complexes compared to benzimidazole derivatives. The absence of the N-H band and the presence of new C=S bands confirmed that the complexes can be used in the preparation of metal sulphide nanoparticles. Elemental analysis showed that there was a percentage mismatch for the complexes I, III, IV and V. Complexes II and VI calculated percentages were within the limits with the found percentages except for sulphur which was low. The TGA curves decomposed to form a mixture of metal and metal sulphides for complex I, II, III and IV except for complex VI which gave metal sulphide only. All benzimidazole complexes decomposed at higher temperatures and were considered as stable complexes. Lead sulphide (PbS) is an important group IV-VI metal chalcogenide semiconductor. It has a direct narrow band gap of 0.41 eV at 300K and a large excitonic Bohr radius of 18 nm. Lead sulphide absorption band can be tuned to anywhere between near IR to UV (0.4μm) covering the entire visible spectrum, while achieving the quantum confinement region. The synthesis of lead sulphide nanoparticles was conducted by varying the effect of the reaction conditions such as the type of capping agents and temperature. Lead dithiocarbamate complex derived from benzimidazole, [Pb(S2N2C8H5)2] was thermolysed in hexadecylamine (HDA) and trioctylphosphine oxide (TOPO) at different reaction temperatures (140, 160 and 180 °C) to produce HDA and TOPO capped PbS nanoparticles. The nanoparticles were characterized using X-ray diffraction (XRD) for structural analysis, transmission electron microscopy (TEM) for shape and size, Ultraviolet visible (UV/Vis) and Photoluminescence (PL) spectroscopy for optical properties. An increase in temperature gave a decrease in the sizes of the nanoparticles when using the HDA capped lead benzimidazole dithiocarbamate complex. The observed morphology was cubes. TOPO capped lead benzimidazole dithiocarbamate complex gave no specific trend when temperature was varied. A cross-like layer with quasi spherical particles on top was observed at 160 °C. At 180 °C, the cross-like layer decomposed into rods- like materials with quasi spherical particles on top for TOPO capped PbS nanoparticles. For lead 2-methylbenzimidazole [Pb(S2N2C9H7)2] dithiocarbamate complex, TOPO capped PbS produced agglomerated cubic morphology at low temperature but as the temperature was increased agglomerated cylindrical shapes were observed. HDA capped PbS produced polydispersed nanocubes which were increasing in size when the temperature was increased. Nanoparticles displayed a blue shift in band edges with good photoluminescence behaviour which was red shifted from their respective band edges all temperatures and capping agents. XRD confirmed the crystal structure of cubic phase (galena) of PbS at all temperatures except for HDA capped PbS nanoparticles at 140 °C from lead benzimidazole dithiocarbamate complex which confirmed the crystal structure of face-centred cubic phase of PbS nanoparticles. Nickel sulphide has much more complicated phase diagram than cobalt sulfides and iron sulfides. Their chemical composition has many crystalline phases such as α-NiS, β=NiS, NiS2, Ni3S2, Ni3S4, Ni7S6 and Ni9S8. Ni3S2 phase has shown potential as a low-cost counter electrode material in dye sensitised solar cells, while the α-NiS phase has been applied as a cathode Material in lithium-ion batteries. The synthesis of nickel sulphide nanoparticles was done by varying the effect of the reaction conditions such concentration and temperature. Nickel benzimidazole dithiocarbamate [Ni(S2N2C8H5)2] and nickel 2-methylbenzimidazole [Ni (S2N2C9H7)2] dithiocarbamates complexes were thermolysed in hexadecylamine (HDA) at different reaction temperatures (140, 160 and 180 °C) and precursor concentrations (0.30, 0.35 and 0.40 g) to produce HDA capped NiS nanoparticles. It was observed that increasing both temperature and precursor concentration increased the size of the nanoparticles. Anisotropic particles were observed for both complexes when varying precursor concentration and temperature. Nickel benzimidazole dithiocarbamate complex produced stable shapes (spheres and cubes) of nickel sulphide nanoparticles. Nickel 2-methylbenzimidazole dithiocarbamate complex produced a mixture of spheres, cubes, triangles and rods nickel sulphide nanoparticles at all concentrations. But when varying temperature, it only produced that mixture at 160 °C. The optical measurements supported the presence of smaller particles at all temperatures and concentrations. XRD showed the presence of C7OS8 and pure nickel as impurities. However, the crystal structure of cubic Ni3S4 was observed at low temperatures and an introduction of monoclinic NixS6 at high temperature (180 °C) when varying temperature for both complexes. When varying concentration using nickel benzimidazole dithiocarbamate complex, XRD showed the presence of NiSO4.6H2O impurities at high temperatures. At 160 °C a mixture of hexagonal NiS and cubic Ni3S4 was observed. At low temperatures only nickel as a metal was found as an impurity and the crystal structure of cubic Ni3S4 was observed. When nickel 2-methylbenzimidazole complex was used, C7OS8 and pure nickel were found as impurities but the crystal structure of cubic Ni3S4 was observed. Cobalt sulphide (CoS) belongs to the family of group II-IV compounds with considerable potential for application in electronic devices. They have a complex phase diagram and their chemical composition have many phases such as Co4S3, Co9S8, CoS, Co1-xS, Co3S4, Co2S3 and CoS2. The synthesis of cobalt sulphide nanoparticles was conducted by varying the effect of temperature on size and shape of the nanoparticles. Nickel benzimidazole dithiocarbamate, [Ni(S2N2C8H5)2] and nickel 2-methylbenzimidazole [Ni(S2N2C9H7)2] complexes were thermolysed in hexadecylamine (HDA) at different reaction temperatures (140, 160 and 180 °C) to produce HDA capped CoS nanoparticles. Cobalt benzimidazole dithiocarbamate complex produced close to spherical shapes nanoparticles at all temperatures. The images showed that as temperature was increased, the size of the particles decreased. All the main reflection peaks were indexed to face-centred cubic Co3S4 and there were some impurities of C7OS8 at all temperatures. The optical measurements supported the presence of smaller particles at all temperatures. Cobalt 2-methylbenzimidazole dithiocarbamate complex produced big and undefined morphology. The optical properties were also featureless and XRD only showed impurities of C7OS8. The impurity is thought to be generated from a side reaction between benzimidazole and carbon disulphide to give this persistent organic moiety.

Surface spectroscopic techniques have been applied to facets of the flotation beneficiation and hydrometallurgical extraction of sulfide minerals to enhance the fundamental understanding of these industrially important processes. As a precursor to the determination of surface chemical composition, the sub-surface properties of some sulfide minerals that have not previously been fully characterised were also investigated. The electronic properties of ??-NiS and ??-NiS (millerite), Ni3S2 (heazlewoodite), (Ni,Fe)9S8 (pentlandite), CuFe2S3 (cubanite), CuFeS2 (chalcopyrite), Cu5FeS4 (bornite) and CuS (covellite) were investigated by conventional and synchrotron X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy augmented by ab initio density of state calculations and NEXAFS spectral simulations. Particular aspects studied included the relationship between sulfur coordination number and core electron binding energies, the higher than expected core electron binding energies for the sulfur in the metal-excess nickel sulfides, and the formal oxidation states of the Cu and Fe in Cu-Fe sulfides. It was concluded that the binding energy dependence on coordination number was less than previously believed, that Ni-Ni bonding was the most likely explanation for the unusual properties of the Ni sulfides, and that there was no convincing evidence for Cu(II) in sulfides as had been claimed. Most of the NEXAFS spectra simulated by the FEFF8 and WIEN2k ab initio codes agreed well with experimental spectra, and the calculated densities of states were useful in rationalising the observed properties. XPS, static secondary ion mass spectrometry (SIMS) and NEXAFS spectroscopy were used to investigate thiol flotation collector adsorption on several sulfides in order to determine the way in which the collector chemisorbs to the mineral surface, to differentiate monolayer from multilayer coverage, and to characterise the multilayer species. It was found that static SIMS alone was able to differentiate monolayer from multilayer coverage, and together with angle-resolved NEXAFS spectroscopy, was also able to confirm that 2-mercaptobenzothiazole interacted through both its N and exocyclic S atoms. The altered layers formed on chalcopyrite and heazlewoodite during acid leaching were examined primarily by means of threshold S KLL Auger electron spectroscopy, but no evidence for buried interfacial species was obtained.