This thesis examines the bioleaching of six different Canadian nickel sulphide ores at pH levels above what is generally considered optimum (~ 2). The majority of work discussed in this thesis was conducted with a low-grade metamorphosed ultramafic nickel sulphide ore from Manitoba, Canada (Ore 3), which is not currently exploitable with conventional technologies. The ore contains 21% magnesium and 0.3% nickel. Nickel is the only significant metal value, and is present primarily as pentlandite. A substantial fraction of the magnesium is present as the serpentine mineral lizardite, making processing difficult with conventional pyro- and biohydrometallurgical techniques. The work with this ore has two equally important objectives: to minimize magnesium mobilization and to obtain an acceptable level of nickel extraction. Batch stirred-tank bioleaching experiments were conducted with finely ground ore ( 147 µm) with temperature and pH control. The first phase of experimentation examined the effect of pH (2 to 6) at 30 °C, and the second phase examined all combinations of three pH levels (3, 4 and 5) and five temperatures (5, 15, 22.5, 30, and 45 °C).

<p>Anodic protection has shown to be a viable method for reducing corrosion rates of stainless steels over a wide range of temperatures and is used to protect equipment in H₂SO₄ manufacturing. While effective at controlling corrosion in H2SO4 manufacturing, Impressed Current Anodic Protection (ICAP) systems have shown to have a number of issues. They require a constant source of current to ensure reliable corrosion protection; are relatively complex systems and expensive to install; improper potential control can lead to loss of corrosion protection; and some issues with cathode fouling and erosion have been reported. Galvanic Coupled Anodic Protection (GCAP) systems have not been widely utilized in industry, but offer some solutions to these issues. GCAP systems have been developed using Pt and Au as the cathode materials for use in H2SO4. Previous work on the oscillatory behaviour of austenitic stainless steels indicates that nickel sulphide (NiS) could be used as cathode material in a GCAP system in concentrated H₂SO₄ to protect stainless steel. The objective of this study was to develop a better understanding of the behaviour of NiS when galvanically coupled to Type 430 stainless steel to determine whether it can be used in a GCAP system. NiS and NiS(Ni) electrodes are able to provide the Icrit needed to passivate Type 430 at anode/cathode ratios of 10:1, while NiS(Ni) electrodes were able to provide the Icrit needed to passivate the Type 430 stainless steel at a ratio of 20:1. In addition it was shown that the NiS(Ni) electrode was able to maintain passivity of the Type 430 stainless steel array using an anode/cathode surface area ratio of 100:1. NiS was shown not to be inert in concentrated H₂SO4 and corrosion rate calculated via Tafel extrapolation and shown to be 0.014 mm/yr at room temperature and 0.128 mm/yr at 60 ºC.</p> / Master of Applied Science (MASc)

M. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / In chemical bath deposition (CBD) method, deposition of metal chalcogenide semiconducting thin films occurs due to substrate maintained in contact with a dilute chemical bath containing metal and chalcogenide ions. Semiconducting nickel sulphide (NiS) and iron sulphide (FeS) thin films have been prepared on a glass substrate by varying the deposition parameters such as the concentration of solutions, deposition time, temperature and pH. Multi-layered thin films were deposited on glass substrate and the spin-cast conductive polymer, poly (3.4-ethylenedioxythiopene) polystyrene sulfonate (PEDOT: PSS) was intercalated. The characterization of the films was carried out using UV-Vis spectroscopy, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and X-ray diffraction (XRD). Single layer nickel sulphide was deposited at room temperature, pH 10 and the deposition period of 3 hours, triethanolamine was used as the complexing agent. Iron sulphide was deposited for 6 hours at 70 °C with the pH of 2.5 using EDTA as a complexing agent. Generally the iron and nickel sulphide were prepared from their respective nickel or iron salt and the thiourea or thiosulfate as a source of sulphide ions in solution. SEM and AFM results show that the FeS film is evenly coated and has uniform grain size with the roughness of ~22.4 nm and thickness of ~23.8 nm. The optical absorption analysis of FeS showed the band gap energy of ~2.9 eV which blue shifted from the bulk. The EDX analysis confirms the compositions of iron and sulphur in FeS films. XRD pattern showed amorphous films for both FeS and NiS thin films due to the amorphous nature of the glass substrate. The optical data of NiS film were analysed and exhibited the band gap energy of ~3.5 eV and ~3.3 eV for successive ionic layer adsorption and reaction (SILAR), which is the modified CBD, both blue shifted from the bulk. The films were observed to have thickness value of ~35.7 nm and ~2.3 nm SILAR with the roughness of ~112.5 nm and ~35.4 nm SILAR from AFM results. SEM confirmed the uniformly distributed film presented by AFM analysis. The chemical composition of Ni and S were confirmed by EDX spectra. The PEDOT: PSS was intercalated between the FeS as the first layer and NiS as the top layer which gave the thickness of ~18.7 nm and roughness of ~115.2 nm from AFM analysis. PEDOT: PSS acted as a passive layer that protects and stabilize the FeS layer and NiS as the third active layer which enhanced the optical absorption of the film when using SILAR method for solar application.

The Nebo-Babel Ni-Cu-platinum-group element (PGE) magmatic sulphide deposit, a world-class ore body, is hosted in low-MgO, tube-like (chonolithic) gabbronorite intrusion in the West Musgrave Block, Western Australia. The Nebo-Babel deposit is the first significant discovery of a nickel sulphide deposit associated with the ca. 1078 Ma Giles Complex, which is part of the Warakurna large igneous province (LIP), now making the Musgrave Block a prime target for nickel sulphide exploration. The Musgrave Block is a Mesoproterozoic, east-west trending, orogenic belt in central Australia consisting of amphibolite and granulite facies basement gneisses with predominantly igneous protoliths. The basement lithologies have been intruded by mafic-ultramafic and felsic rocks; multiply deformed and metamorphosed between 1600 Ma and 500 Ma. The Giles Complex, which is part of the Warakurna LIP, was emplaced at ca. 1078 Ma and consists of a suite of layered mafic-ultramafic intrusions, mafic and felsic dykes and temporally associated volcanic rocks and granites. The Giles Complex intrusions are interpreted to have crystallised at crustal depths between 15km and 30km and are generally undeformed and unmetamorphosed.