The effects of some associated minerals on thiosulfate gold leaching were studied through thermodynamic analysis and leaching experiments on composite ore samples containing various minerals and a reference silicate gold ore. In the leaching test on the reference gold ore, about 93% of gold was extracted within 3.0 hours. The presence of various amount of pyrite, pyrrhotite, chalcopyrite, arsenopyrite, chalcocite, bornite, and some lead species, has significant detrimental effects. Under reduced oxygen conditions, the thiosulfate consumptions could be significantly reduced. High gold extractions (i.e. >= 90%) were observed in the leaching tests with reduced dissolved oxygen (i.e., 0.7% oxygen in the supplied gas) in the absence or in the presence of sulfide minerals such as pyrite, pyrrhotite, arsenopyrite and chalcopyrite. High copper concentration and a pre-aeration step was also found to largely increase the gold extractions under such conditions. Thiosulfate-copper-ethylenediamine system was found effective in the leaching of gold. The leaching kinetics was significantly slower than that of the conventional thiosulfate-copper-ammonia leaching. The consumption of thiosulfate, however, was largely reduced. This leaching system worked effectively on the reference gold ore within a wider pH range (e.g., 6-11), with or without ammonia. The presence of ammonia in a low concentration improved the leaching rate but also increase the consumption of thiosulfate. Comparable gold extractions were observed in the leaching of the composite ores containing various sulfide minerals, such as pyrite, pyrrhotite, chalcocite, galena and chalcopyrite. The leaching of gold in the presence of iron sulfides was also improved by applying chemical additives, such as, carbonate, calcium, galena, phosphate, and additional hydroxide anion. It is proposed that these additives either passivated the harmful surface of sulfide minerals or masked some detrimental aqueous species. Finally, some improved leaching methods concluded in this study were applied on a few industrial ore samples in order to demonstrate the effectiveness of these methods. It was found that by comprehensively applying these improved thiosulfate leaching strategies, satisfactory gold extractions and thiosulfate consumption results were archived on these ores. / Thesis (Ph.D, Mining Engineering) -- Queen's University, 2008-09-18 11:48:38.672

Cu(In,Ga)Se2 (CIGS) thin film solar cells contain a thin layer of CdS. To avoid toxic heavy-metal-containing waste in the module production the development of a cadmium-free buffer layer is desirable. This thesis considers alternative Cd-free buffer materials deposited by Atomic Layer Deposition (ALD). Conditions of the CIGS surface necessary for ALD growth are investigated and the heterojunction interface is characterized by band alignment studies of ZnO/CIGS and In2S3/CIGS interfaces. The thesis also includes investigations on the surface modification of the CIGS absorber by sulfurization. According to ALD theory the growth process is limited by surface saturated reactions. The ALD growth on CIGS substrates shows nucleation failure and generally suffers from surface contaminations of the CIGS layer. The grade of growth disturbance varies for different ALD precursors. The presence of surface contaminants is related to the substrate age and sodium content. Improved growth behavior is demonstrated by different pretreatment procedures. The alignment of the energy bands in the buffer/absorber interface is an important parameter for minimization of the losses in a solar cell. The valence band and conduction band offsets was determined by in situ X-ray and UV photoelectron spectroscopy during layer by layer formation of buffer material. The conduction band offset (ΔEc) should be small but positive for optimal solar cell electrical performance according to theory. The conduction band offset was determined for the ALD ZnO/CIGS interface (ΔEc = -0.2 eV) and the ALD In2S3/CIGS interface (ΔEc = -0.25 eV). A high temperature process for bandgap grading and a low temperature process for surface passivation by post deposition sulfurization in H2S were investigated. It is concluded that the high temperature sulfurization of CuIn(1-x)GaxSe2 leads to phase separation when x>0. The low temperature process did not result in enhanced device performance.

The oxidative dissolution of chalcopyrite in ferric media often produces incomplete copper recoveries. The incomplete recoveries have been attributed to inhibition caused by the formation of a metal deficient sulphide and the deposition of elemental sulphur and jarosite. Although these phases have been qualitatively identified on the surface of chalcopyrite, none have been quantitatively identified. The aim of the project was to quantitatively analyse the surface before and after oxidative dissolution, with X-ray photoelectron spectroscopy (XPS), and to use the phases identified as the basis for mechanisms of dissolution and inhibition. / XPS analysis was performed on chalcopyrite massive fractured under anaerobic atmosphere and chalcopyrite massive and concentrate oxidised in 0.1 M ferric sulphate (pH 1.9) and 0.2 M ferric chloride (pH 1.6) at 50, 65 and 80ºC. Quantitative XPS analysis of the chalcopyrite surfaces required the development of programs that accounted for the observed XPS spectra. The output of these programs was used to construct profiles of the chalcopyrite surfaces and the deposited phases. These surface profiles were correlated with copper recoveries determined for chalcopyrite concentrate dissolution under the same conditions. / The surface of chalcopyrite before oxidative dissolution reconstructs to form a `pyritic' disulphide phase. This phase is oxidised in ferric media to form thiosulphate via the incorporation of oxygen atoms from the hydration sphere. The thiosulphate reacts in the oxidising conditions of low pH to form elemental sulphur, sulphite and sulphate. The sulphate complexes with ferric to produce hydronium jarosite. This reaction occurs at the surface during the initial stages of dissolution and in the bulk solution during the latter stages. This precipitation of hydronium jarosite during the latter stages of dissolution corresponds to inhibition of the dissolution reaction. It is therefore concluded hydronium jarosite is responsible for inhibiting the oxidative dissolution of chalcopyrite in ferric media. / The identification of hydronium jarosite as the inhibiting phase is consistent with the industrial practice of removing `excess' iron from the ferric solution before oxidative dissolution. However, additional iron and sulphate are generated at the chalcopyrite surface during oxidative dissolution. These high iron and sulphate concentrations combine with the low pH and high temperatures favoured for the oxidative dissolution of chalcopyrite to produce ideal conditions for jarosite precipitation. Therefore, pH must be lowered further to prevent jarosite precipitation and enhance copper recoveries from chalcopyrite in ferric media.

The Masumbi Au-Cu deposit in the Ndori Greenstone Belt of western Kenya is hosted in dacitic volcanics of the Nyanzian Group (2710 ± 340 Ma) and dioritic to granodioritic felsic intrusives (2504 ± 48 Ma). The deposit is characterised by gold and copper mineralisation that is associated with quartz-sulphide veins and veinlets. The copper mineralisation typically occurs as chalcopyrite. Gold is closely associated with pyrite in mineralogy and its pathfinder elements silver, bismuth, tellurium and selenium in geochemistry. The gold occurs in two forms that may indicate two generations of precipitation: the equant and the elongate forms. Based on Au/Ag ratios, the equant gold grains can be classified as native gold as their gold content is greater than 90 wt%. The elongate gold grains can be classified as electrums as their silver content is greater than 38 wt%. While there is a strong Au-Ag association within individual gold grains supporting an orogenic model for the gold mineralisation, mineralisation at the Masumbi Prospect appears atypical of Archaean orogenic gold deposits because of the abundance of copper (up to 0.43%). The enrichment of silver, copper, bismuth and tellurium in ore assemblages is common in porphyry, VMS and epithermal systems, but their presence at Masumbi does not preclude the formation as an orogenic deposit. Assay results from three Masumbi diamond drill-holes show an apparent correlation between gold and copper. However, petrography and electron probe microanalyses results from this study indicate that chalcopyrite is an earlier phase than pyrite as it occasionally occurs as inclusions in pyrite. This petrogenetic relationship between pyrite and chalcopyrite suggests that there is no temporal relationship between gold and copper mineralisation. Statistical analysis of the assays shows no linear correlation between gold and copper thereby supporting the above findings. The gold and copper mineralisation have been interpreted as forming as two separate events with copper forming first followed by gold. These events are both related to the intrusion of the felsic rocks that are associated with the Aruan metamorphic event that has been responsible for the bulk of the gold mineralisation on the Tanzanian Craton. The common alteration assemblage in the Masumbi rocks comprises chlorite and epidote. This alteration assemblage is typical of regional greenschist metamorphic facies grading into amphibolite metamorphic facies in the Nyanzian Group of Kenya. However, these alteration minerals could possibly be products of propylitic alteration in the rock groundmass. Other alteration mineral assemblages, possibly of hydrothermal origin, comprise muscovite, sericite, quartz, carbonate, associated with the sulphides pyrite and chalcopyrite. Although the occurrence of gold appears to be controlled by the presence of pyrite, it is also associated with silicification. Exploration methods have been proposed to target undiscovered gold deposits in the Ndori Greenstone Belt that are similar to the Masumbi deposit. These methods could probably be applied to vein-type gold deposits in other granite-greenstone terranes in the Lake Victoria Goldfields.

No description available.

Copper is an essential metal in today’s economy, due to its superior electrical and thermal conductivities, alloying properties, and chemical uses. Most copper is produced viamining and refining, and most copper is found in the earth’s crust as chalcopyrite, CuFeS2. Typically, chalcopyrite is concentrated and fed to a high temperature pyrometallurgical process which produces >99.99% purity copper cathodes. Recently, Freeport-McMoRan Inc. has implemented a hydrometallurgical autoclave-leaching process that takes chalcopyrite concentrate and produces copper cathodes. It is imperative that these pyrometallurgical and hydrometallurgical processes be modeled and compared so that the extraction industry can best decide which technology to apply in the future. This work presents transient, reduced-order models for the comparison of the two processes using exergy balances. Exergy is typically thought of as the maximum work extractable from a system as it spontaneously reacts to the state of the surrounding environment; for extractive processes, it is also helpful to think of exergy as the minimum work required to effect a concentration, e.g. of copper. Exergy balances are thus similar to first law balances, but they comment on the location and magnitude of usefulenergy flows, instead of energy flows in general. For the baseline case, this work found that the pyrometallurgical process up to 99.5% copper anode stored 54% of the fed exergy in product, lost 20% of the fed exergy, and destroyed the remaining 26%. In contrast, the hydrometallurgical process up to 30 grams-per-liter copper pregnant-leach-solution stored 5% of the fed exergy in product, lost 9% of the fed exergy, and destroyed the remaining 86%. The effects of process variations are also looked at. It is recommended that this work be incorporated in whole-plant exergy balances to more precisely examine the tradeoffs between the pyrometallurgical and hydrometallurgical routes of copper extraction from chalcopyrite concentrates.

Chalkopyrit (CuFeS2) stellt den wichtigsten Rohstoff für die Kupfergewinnung dar. Um effiziente hydrometallurgische Gewinnungsverfahren für sulfidische Kupfererze zu entwickeln, sind mechanistische Studien der Redoxchemie von Chalkopyrit erforderlich. Der hierfür als Referenzmaterial erforderliche Chalkopyrit konnte synthetisiert und unter Anwendung der Pulver-Röntgendiffraktometrie und 57Fe-Mößbauer-Spektroskopie analysiert werden. Phasenreiner Chalkopyrit kann unter Verwendung eines Schwefelunterschusses hergestellt werden und ist bis 480 °C thermisch stabil. Mittels elektrochemischer Messungen wurde ein Einblick in die Oxidationsprozesse des Minerals in wässriger, chloridischer Lösung gegeben. Das Lösen der Cu-S- und Fe-S-Bindungen des Minerals ist anhand einer Variation des pH-Wertes der Laugungslösung beeinflussbar. Cu(II)-Ionen sind gegenüber Fe(III)-Ionen das wirksamere Oxidationsmittel bei dem anodischen Lösen des Minerals.

<p> The "B" horizon at Tilt Cove occurs in subaqueous mafic volcanics near the base of the Silurian Cape St. John Group. It is 3 metres below a well-banded oxide iron formation ("A" horizon). </p> <p> Mineralization in the "B" horizon is analogous to that of the East Mine in that it is volcanogenic and has resulted in extensive chloritization of the footwall rocks, and in the deposition of banded sulphides or the replacement of the existing mafic volcanics by sulphides. There are differences in the geochemistry mineral textures and mineral types. The East Mine host volcanics are alkali depleted basaltic komatiites to magnesium theleiites. The horizon host volcanics are spillitized magnesium tholeiites. Samples of ore from the East Mine show well-developed colloform and framboidal textures. Pyrite, magnetite, hematite and chalcopyrite are the dominant minerals with minor sphalerite and accessory covellite. Samples from the horizon show relict colloform textures and framboids with less internal structure due to overgrowths. Atoll textures indicating extensive replacement are common. Pyrite is the dominant sulphide followed by sphalerite, chalcopyrite, accessory covellite and gold. The chalcopyrite occurs both as replacement of pyrite and exsolution in sphalerite. The most significant difference between samples from the East Mine and "B" horizon is the greater abundance of gold in the "B" horizon and its correlation with sphalerite. </p> / Thesis / Bachelor of Science (BSc)

Freshwater shortages causes challenges in mineral processing in Chile, especially in arid regions. As a result, froth flotation; a mineral process, is shifting usage of freshwater to seawater. This has consequences in the consumption of flotation reagents and decreasing the flotation efficiency. Biotechnological developments allow conceptualising the use of bacterial cells and their metabolites as bioreagents in flotation; classified as bioflotation. In this thesis, 5 halophilic bacteria, namely, Halomonas boliviensis, Marinobacter spp., Halobacillus litoralis Hol-1, Marinococcus halophilus KOR-3 and Halomonas eurihalina P6-1 have been screened for the potential use as pyrite biodepressants at micro- and batch-scale flotation. The effect of bioconditioning minerals with these bacteria was studied using zeta potential, fluorescence microscopy and contact angle. Experiments measuring zeta potential show the isoelectric point (IEP) of pyrite, chalcopyrite and molybdenite became more acidic post-bioconditioning. Fluorescence microscopy with Nile red; a hydrophobic stain, allowed for a method to visualize bacterial cells or collector potassium isopropyl xanthate (KIPX) on mineral particles of pyrite, chalcopyrite and molybdenite. Additionally contact angle experiments show that strains Halobacillus litoralis Hol-1, Marinococcus halophilus KOR-3 and Halomonas eurihalina P6-1 had an influence on the contact angle of pyrite and chalcopyrite, inducing changes in their hydrophobicity. Microflotation experiments showed a decreased recovery of pyrite in presence of all strains, but notably, Halobacillus litoralis Hol-1 and Marinococcus halophilus KOR-3, also showed an increased recovery of chalcopyrite, making them ideal candidates as pyrite biodepressants. Halomonas eurihalina P6-1 showed low recoveries of both minerals, but a higher selectivity depressing more pyrite than chalcopyrite. Usage of autoclaved biomass from the three aforementioned strains in batch-flotation experiments resulted in the recovery of chalcopyrite improving, with a small decrease in the recovery of pyrite, overall showing a positive potential but not improving the system. Halophilic bacteria such as the ones used in this study show an influence on the floatability of pyrite, which could be commercially exploited to substitute lime as a pyrite depressant. Furthermore, the work in this thesis focused on studying the effects of cells in artificial seawater, both at micro and batch-scales which brings the laboratory experiments a step closer to industrially relevant conditions.

Au cours des dernières années, la demande croissante en cuivre, zinc et nickel a conduit à une augmentation de la récupération de minéraux précieux à partir de minerai complexes. Parmi ces minéraux, la chalcopyrite, la sphalérite et la pentlandite sont des minéraux sulfurés souvent trouvés en association avec d'autres tels que la pyrite et la pyrrhotite. La séparation et la concentration de ces minéraux sont généralement réalisées par flottation, un procédé qui sépare les particules hydrophobes des particules hydrophiles et permet de récupérer les premières dans une mousse en tête de cuve. Le degré d'hydrophobicité d'un minéral dépend de sa nature inhérente et des altérations de surface induites par les collecteurs et les déprimants ajoutés à la suspension de particules, avec d'autres agents tensio-actifs. Néanmoins, les collecteurs utilisés dans la flottation des sulfures sont connus pour être nocifs. Par conséquent, il y a un intérêt pour le développement de nouveaux collecteurs plus respectueux de l'environnement. Dans le travail actuel, mené dans le cadre de nos efforts pour développer des collecteurs alternatifs, efficaces et économiquement compétitifs, nous avons utilisé la technique de présentation de peptides par des phages (phage display) couplée aux technologies de séquençage à haute capacité pour l'identification des peptides présentant une forte affinité pour la chalcopyrite. Pour ce faire, nous avons utilisé une bibliothèque de heptapeptides linéaires, et les candidats potentiels ont été soumis à une validation par le biais de tests d'adsorption. Ces tests comprenaient une comparaison des capacités d'adsorption des séquences produites de différentes manières et sous différentes formes : des phages, des peptides synthétiques et des protéines de fusion avec d'autres éléments d'intérêt. Les résultats de ces tests ont confirmé la capacité d'adsorption des séquences sélectionnées sur la chalcopyrite. De plus, nous avons démontré que les peptides synthétiques désalés constituent une option viable pour des tests d'adsorption. En outre, nous avons créé deux types de bio-collecteurs en ajoutant à nos séquences affinitaires des queues hydrophobes,composées de leucine (L), de différentes longueurs : soit 3 L ou 5 L. Ces queues hydrophobes ont été intégrées dans deux séquences validées pour construire des collecteurs à base de peptides. Ces nouveaux collecteurs ont été évalués pour leur adsorption sur la chalcopyrite et le quartz. Ensuite, des tests de micro-flottations ont été réalisées à l'aide d'un tube d'Hallimond. Les résultats ont révélé que ces peptides étaient efficaces et sélectifs pour faire flotter la chalcopyrite par rapport au quartz, démontrant le potentiel des queues hydrophobes et de l'utilisation de collecteurs à base de peptides dans la flottation des minerais sulfurés. Finalement, nous avons exploré la faisabilité de l'utilisation de diverses protéines recombinantes pour produire les peptides. Nous avons utilisé trois gènes rapporteurs de tailles variables : 1) la protéine fluorescent verte (EGFP), avec et sans l'ajout des liens, 2) PhiLOV3 dans diverses configurations, et 3) la thioredoxine fusionnée avec des répétitions du peptide. Une expression réussie des peptides fusionnés aux gènes rapporteurs a été obtenue en quantités signifficatives et sous une forme soluble lors de l'utilisation de l'EGFP. / In recent years, the growing demand for copper, zinc and nickel has led to an increase in the recovery of valuable minerals from complex ores. Among these minerals, chalcopyrite, sphalerite, and pentlandite are sulphides minerals often found in association with other such as pyrite and pyrrhotite. The separation and concentration of these minerals are typically achieved by froth flotation, a process that separates hydrophobic from hydrophilic particles and enables the hydrophobic particles to be recovered in a foam at the top of the tank. The degree of hydrophobicity exhibited by a mineral depends on its inherent nature and surface alterations induced by collectors and depressants added to the particle suspension, along with other surfactants. However, collectors used in sulphide flotation have been known to be harmful to the environment. Hence, there is an interest in the development of novel collectors that are more environmentally friendly. In the current work, conducted as part of our efforts to develop efficient and economically competitivee alternative collectors, we employed the phage display technique coupled with high-throughput sequencing technologies to identify peptides with high affinity for chalcopyrite. To achieve this, we employed a library of linear peptides, and potential candidates were subject to validation through adsorption tests. These tests involved comparing the adsorption capacities of sequences produced in different ways: phages, synthetic peptides, and fusion proteins with other elements of interest. The results of these tests confirmed the adsorption capacity of the selected sequences on chalcopyrite. Moreover, we demonstrated that desalted synthetic peptides serve as a viable option for adsorption tests. Furthermore, we have created two types of bio-collectors by adding hydrophobic tails, composed of leucine (L), of different lengths to our affinity sequences: either 3 L or 5 L. These hydrophobic tails were added were integrated into two validated sequences to construct peptidebase collectors. These newly devised collectors were assessed for adsorption on chalcopyrite and quartz. Subsequently, micro-flotation test were conducted using a Hallimond tube. The results revealed that these peptides were efficient and selective in floating chalcopyrite with respect to quartz, showing the potential of the hydrophobic tails, and the use of peptide-base collectors in the flotation of sulphide ores. Lastly, we explored the feasibility of utilizing various recombinant proteins to produce the peptides. We employed three different reporter genes of varying sizes: 1) Enhanced green fluorescence protein (EGFP), both with and without linkers, 2) PhiLOV3 in diverse configurations, and 3) Thioredoxine fused with repetitions of the peptide. Successful expression of peptides fused to reporter genes was achieved in significant quantities and a soluble form when utilizing EGFP.