Tesi: "Sulphide minerals"

1

DiFeo, Anthony. "Heterocoagulation of sulphide minerals". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0032/NQ64547.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Richardson, Stephen. "Sulphide ore minerals : surface chemical properties". Thesis, Aston University, 1988. http://publications.aston.ac.uk/8068/.

Testo completo

Abstract (sommario):

The surfaces of iron-containing sulphide minerals were oxidised by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The characterisation of surface oxidation is relevant to the alteration of ores in nature and their behaviour during flotation and leaching, of importance to the metallurgical industry. The sulphides investigated included pyrite (FeS2), hexagonal pyrrhotine (Fe9S10), monoclinic pyrrhotine (Fe7Se), violarite (FeNi2S4), pentlandite ((FeiNi)9Se), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). The surfaces were oxidised by various methods including acid (sulphuric), alkali (ammonium hydroxide), hydrogen peroxide, steam, electrochemical and air/oxygen (in a low-temperature (150ºC) furnace), The surfaces were examined using surface sensitive chemical spectroscopic methods including x-ray photoelectron spectroscopy (ms), Auger electron spectroscopy (LES) and conversion electron Mössbauer spectroscopy (CEKS). Physical characterisation of the surfaces was undertaken using scanning electron microscopy (SM), spectral reflectance measurements and optical microscopy. Bulk characterisation of the sulphide minerals was undertaken using x-ray diffraction and electron microprobe techniques. Observed phases suggested to form in most of the sulphide surfaces include Fe204, Fe1-x0, Fe202, Fe00H, Fe(OH)3, with iron II & III oxy-sulphates. The iron sulphides show variable extents of oxidation, indicating pyrite to be the most stable. Violarite shows stability to oxidation, suggested to result from both its stable spinel crystal structure, and from the rapid formation of sulphur at the surface protecting the sub-surface from further oxidation. The phenomenon of sub-surface enrichment (in metals), forming secondary sulphides, is exhibited by pentlandite and chalcopyrite, forming violarite and copper sulphides respectively. The consequences of this enrichment with regard to processing and leaching are discussed. Arsenopyrite, often a hindrance in ore processing, exhibits the formation of arsenic compounds at the surface, the dissolution of which is discussed in view of the possible environmental hazard caused by the local pollution of water systems. The results obtained allow a characterisation of the sulphides in terms of their relative stability to oxidation, and an order of stability of the sulphide surfaces is proposed. Models were constructed to explain the chemical compositions of the surfaces, and the inter-relationships between the phases determined at the surface and in the sub-surface. These were compared to the thermo-chemically predicted phases shown in Eh/pH and partial pressure diagrams! The results are discussed, both in terms of the mineralogy and geochemistry of natural ores, and the implications for extraction and processing of these ore minerals.

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Catherine, J. H. "The anodic dissolution of copper from complex sulphide minerals". Thesis, University of Exeter, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381574.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

4

Gudyanga, Francis Pedzana. "Electrohydrometallurgical reduction of cassiterite (SnO2) associated with sulphide minerals". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47090.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Swarts, Arnoldus Carel. "The Influence of magnetic fields on the flotation of sulphide minerals". Diss., Pretoria : [s.n.], 2001. http://upetd.up.ac.za/thesis/available/etd-02192007-094826.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Goh, Siew Wei Chemistry Faculty of Science UNSW. "Application of surface science to sulfide mineral processing". Awarded by:University of New South Wales. School of Chemistry, 2006. http://handle.unsw.edu.au/1959.4/32912.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Sharma, Prashant K. "Surface studies relevant to microbial adhesion and bioflotation of sulphide minerals /". Luleå, 2001. http://epubl.luth.se/1402-1544/2001/37/index.html.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

8

Al-Harahsheh, Mohammad. "A fundamental investigation into the microwave assisted leaching of sulphide minerals". Thesis, University of Nottingham, 2005. http://eprints.nottingham.ac.uk/11075/.

Testo completo

Abstract (sommario):

Microwave assisted leaching has been investigated in an attempt to improve both the yield of extracted metal and reduce processing time. This is especially pertinent in view of the increased demands for metal and more environmentally friendly processes. This work reports a fundamental study on the influence of microwave energy on the dissolution of sulphide minerals. Chalcopyrite and sphalerite were chosen as model materials due to their economic importance and the diversity of their heating behaviour in a microwave field (chalcopyrite being an excellent microwave heater and sphalerite being an extremely poor microwave receptor). Chalcopyrite leaching has been carried out in ferric sulphate and ferric chloride under both microwave and conventional conditions. Conventionally, it was found that chalcopyrite dissolution in ferric sulphate seems to be limited by surface reaction control. More importantly, it has been shown that specific fracture planes on chalcopyrite particle surfaces experience selective leaching, which was revealed by SEM and ToF-SIMS surface analysis. The preferential attack on particular planes is speculated to be linked to different chemistry of some cleavage planes within the chalcopyrite crystal. In the ferric chloride system, however, it was found that cupric chloride, a reaction product of chalcopyrite with ferric sulphate, may play an important role in the dissolution process. Leaching of both chalcopyrite and sphalerite in ferric sulphate under microwave conditions has shown enhanced recoveries of metal values compared to that produced conventionally. It has been demonstrated that the enhanced copper recovery from chalcopyrite during microwave treatment is as a result of the selective heating of the mineral particles over the solution which was found to be highly lossy. In addition, it is suggested that high loss leaching solutions will develop a superheated layer close to the periphery of the reaction vessel (due to the small penetration depth) which creates localised heating compared to the bulk solution temperature. The enhanced recovery of zinc from sphalerite seems to occur as a result of only the presence of the superheated layer. If leaching takes place within this layer, an apparent rate increase will be noted with respect to the measured bulk temperature. The hypotheses of selective heating (for chalcopyrite) and the effect of penetration depth (for chalcopyrite and sphalerite) were supported by the negligible difference between the activation energy values under microwave and conventional conditions for both chalcopyrite and sphalerite. Furthermore, the measurements of dielectric properties of the leaching solutions have shown that such solutions are highly lossy and characterised by a penetration depth of an order of about 3 mm. Finally, numerical electromagnetic simulations showed that chalcopyrite particles could be heated selectively when micro-waved within highly lossy leaching solutions due to their high conductivity. It is concluded that the dielectric properties of both the solid and liquid phases, the dimensions of the reactor and the position of solid particles within the reactor determine the leaching outcome. More importantly, it is likely that the enhanced recoveries observed are not likely to be as a result of a so called "non-thermal microwave effect" but rather as a result of thermal effects.

Gli stili APA, Harvard, Vancouver, ISO e altri

9

Hunter, C. J. "An electrochemical investigation of the froth flotation of iron bearing sulphide minerals". Thesis, Brunel University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.351913.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Taguta, Jestos. "The thermochemical behaviour of thiol collectors and collector mixtures with sulphide minerals". Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20124.

Testo completo

Abstract (sommario):

Thiol collectors continue to dominate the base metal sulphide (BMS) and platinum group mineral (PGM) flotation industry. The behaviour of thiol collectors and collector mixtures with sulphide mineral surfaces has been extensively studied using different techniques such as XPS, ToF-SIMS, UV-VIS, etc. However, most of these techniques require a collector dosage above monolayer coverage, take place under equilibrium conditions and may not simulate flotation conditions. Moreover, most of the studies focus on isolated minerals yet exploitable ores exist as an association of sulphide minerals. The use of thiol collector mixtures in the base metal sulphides (BMS) and platinum group mineral (PGM) flotation industries has been reported to offer several performance benefits by many researchers. However, the mechanism whereby these collector mixtures adsorb onto a specific mineral surface is still not clearly understood. This study used isothermal titration microcalorimetry to monitor sub-monolayer reactions by continuously measuring the heats of adsorption as the reactions between thiol collector (and collector mixtures) and sulphide minerals (and mixed minerals) proceed in real time. The enthalpy of adsorption does not only characterise the intensity of adsorption between a collector and mineral surface but also gives insight into the reaction mechanism, whether physisorption (less negative than -40 kJ/mol) or chemisorption (more negative than -40 kJ/mol). Microflotation was also used to determine the hydrophobicity imparted onto the mineral particles as a result of the mineral-collector interactions. Sulphide minerals investigated were chalcopyrite, pyrite, pyrrhotite and galena. Thiol collectors investigated were xanthates of varying chain length (SEX, SIBX, PNBX and PAX) as well as dithiocarbamates (diethyl-DTC and n-butyl DTC) and diethyl-DTP. The current study seeks to gain knowledge of which collector interacts best with which mineral and an understanding of the mechanism behind the reactions. This study also seeks to investigate the performance and adsorption mechanisms when single minerals are interacted with thiol collectors singly and also in a mixture. A better understanding of how to design collector mixtures is to be gained. Furthermore this study seeks to understand the effect of mineral-mineral interactions on thiol collector adsorption and on the floatability of the pure minerals.

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Chimonyo, Wonder. "An investigation into the relationship between electrochemical properties and flotation of sulphide minerals". Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20730.

Testo completo

Abstract (sommario):

There is a growing importance in the mineral processing industry to find ways which are economic and effective in improving the recovery of minerals in the flotation process. The focus of this study was on the recovery by flotation of minerals found in the Merensky reef, which is one of the major reefs in the Bushveld complex. In that reef, base metal sulphide (BMS) minerals are commonly associated with PGMs and this has an effect on the way in which these minerals are concentrated by flotation (Vermaak et al. 2004; Wiese et al. 2005b; Miller et al. 2005; Schouwstra et al. 2000).A major problem in this process has been reported to be losses of valuable minerals (PGMs) associated with the loss of BMS (Wiese et al. 2005b), during flotation. The present investigation has focused on studying the relationship between the flotation of sulphide minerals using xanthates as collectors and the electrochemical properties of the flotation system. It is well known that electrochemical mechanisms in flotation systems have a major influence on flotation since the reactions occurring at the mineral/solution interface are of critical importance in the process (Woods, 1971).The aim of this study was to investigate the extent to which there was a relationship between the electrochemical reactions occurring in this ore which could indicate the effectiveness of the flotation process. The electrochemical reactions were studied by determining the redox potential changes occurring when various changes were made. These were the length of the alkyl chain length of the xanthate collector, changing the pH or using various chemical reagents to change the potential of the system. It was found from the rest potential measurements, that collectors of different chain length have different extents of interaction with mineral surface. A greater interaction, which is indicated by a greater change in the mixed potential after addition of the collector, is considered to be indicative of a greater adsorption of the collector at the mineral surface. It was hypothesized that this stronger adsorption by collectors of longer alkyl chain length would result in improved flotation performance. However, this was not observed to be the case and that was consistent with previous results on the relationship between the recovery of sulphide minerals in the Merensky ore and xanthates of different chain lengths. Thus it was shown that there was no correlation between the interactions between collectors of different alkyl chain lengths as determined through electrochemical studies and the flotation performance of valuable minerals under the tests conditions used.

Gli stili APA, Harvard, Vancouver, ISO e altri

12

Rossouw, Deon. "A technical risk evaluation of the Kantienpan volcanic hosted massive sulphide (VHMS) deposit and its financial viability". Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-08132008-094204/.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Sui, Chihyu Caroline. "Metal ion transfer between sulphide minerals and effect on xanthate interaction with pyrite". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40263.

Testo completo

Abstract (sommario):

Metal ion production by minerals alone and in pairs was studied by solution analysis, extraction with ethylene diamine tetraacetate (EDTA) and laser ion mass spectroscopy (LIMS) for combinations of pyrite, pyrrhotite, galena, and sphalerite. The effect of grinding, pH, and the presence of xanthate was studied. Metal ion transfer between sulphide minerals was determined.
Metal ion production with minerals in pairs was different from that for single minerals. The amount of metal ion in solution followed a galvanic interaction model, increasing for the anodic mineral and decreasing for the cathodic mineral. However, from the EDTA extraction technique, the concentration of metal ions on the mineral surface increased for both minerals. The mechanism of additional metal ion production on the cathodic mineral is unclear, but may be related to reaction between the mineral and OH ions formed on the surface as a result of galvanic interaction.
Metal ions transferred between two minerals in contact. In the case of pairing with pyrite, the larger proportion of Fe remained on pyrite, while 50% or more of Zn (from sphalerite) and Pb (from galena) transferred to pyrite.
The effect of Pb ions on pyrite in the presence of xanthate, and diethylene triamine (DETA) was investigated by cyclic voltammetry, ex situ spectroelectrochemical analysis and zeta potential measurements.
Once pyrite was contaminated by Pb ions, uptake of xanthate was promoted at pHs 9.2 and 10.5 with lime as pH modifier. The source of Pb--from solution or from contact with galena--was not a factor, and the effect was evident at Pb concentrations as low as 1 ppm. With soda ash as pH modifier, the effect of Pb was suppressed, perhaps due to formation of lead carbonate. The only xanthate product detected was dixanthogen, unless an initial potential less than $-$800 mV/SCE was imposed (when Pb$ sp{2+}$ is reduced to Pb$ sp0)$ and lead xanthate formed.
Xanthate adsorption on Pb-contaminated pyrite was suppressed by DETA, but relatively large concentrations were required. DETA decreased the potential at the mineral/solution interface, which retarded oxidation of xanthate to dixanthogen.
A mechanism of Pb "activation" of pyrite was proposed: adsorption of Pb(OH)$ sp+$ on pyrite provided sites for xanthate adsorption forming Pb(OH)X, on which xanthate ions were attached by hydrophobic interaction and oxidised to dixanthogen.

Gli stili APA, Harvard, Vancouver, ISO e altri

14

Todd, Emma Claire. "Surface oxidation of sulphide minerals : nanomineralogy and electronic structure from x-ray spectroscopy". Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274619.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Khalid, Muhammad. "Gold cyanidation : gold associated with silver minerals embedded within base-metal sulphide matrices". Doctoral thesis, Université Laval, 2017. http://hdl.handle.net/20.500.11794/27893.

Testo completo

Abstract (sommario):

Les problématiques dans le traitement des minerais aurifères deviennent de plus en plus significatives avec la déplétion des gisements à haute teneur autour du monde. L’or est trouvé principalement sous forme métallique dans la nature et est fréquemment associé avec des minéraux d’argent ou des sulfures métalliques. Dans la présente thèse, le rôle des minéraux d’argent sur la cyanuration de l’or au sein de sulfures métalliques est étudié en détail relativement aux interactions galvaniques et aux phénomènes de passivation de surface. Puisque les contacts galvaniques permanents naturellement présents à l’intérieur des grains des minéraux sont difficiles à répliquer en utilisant des montages standards d’électrodes à disques rotatifs ou de la pulpe de minerais riches en sulfures, une stratégie utilisant un réacteur à lit fixe (PBR) a été adoptée afin d’isoler et de quantifier les contributions des interactions galvaniques et des réactions de passivation sur les taux de lixiviation de l’or et de l’argent au sein de sulfures métalliques. Des mélanges d’or, de minéraux d’argent et d’autres sulfures métalliques ont été placés dans le réacteur à lit fixe afin de créer des contacts galvaniques inter-particules permanents parmi les constituants. La pyrite, la sphalérite et la stibnite ont été choisis comme sulfures métalliques modèles. De l’argent métallique (Ag), de l’acanthite Ag₂S) et de la pyrargyrite (Ag₃SbS₃) sont pour leur part les minéraux d’argent qui ont été étudiés. Les interactions galvaniques entre l’or, l’argent et la pyrite ainsi que la sphalérite ont résulté en un comportement complexe de la lixiviation de l’or et de l’argent sous l’impact direct des contacts galvaniques ainsi que sous l’impact des effets de passivation. Les minéraux d’argent ont pour leur part démontré un effet amoindrissant pour la lixiviation de l’or dans de la chalcopyrite et de la stibnite. Des stratégies ont été investiguées pour améliorer la cinétique de lixiviation de l’or en présence de minéraux d’argent et de sulfures métalliques. Des solutions de cyanure contant des sels de plomb ont augmenté la récupération de l’or et ont permis une neutralisation des effets négatifs issus de la présence des sulfures métalliques, particulièrement dans le cas de la chalcopyrite. De plus, l’addition de plomb a augmenté les cinétiques de lixiviation de l’or de manière significative pour l’or et l’argent associé à de la pyrite, de la chalcopyrite et de la sphalérite. Un prétraitement à l’aide d’une solution alcaline d’acétate de plomb a été étudié pour les mêmes couples de minéraux et il a été démontré que cette stratégie augmente la récupération de l’or dans le cas de la pyrite, de la chalcopyrite et de la sphalérite. D’autre part, la stibinite a démontré un effet net de réduction de la dissolution de l’or avec des minéraux d’argent. Des films recouvrant la surface des particules d’or dans le cas de la cyanuration de l’or en présence des sulfures métalliques ont aussi été observés dans le cas de la chalcopyrite et de la stibnite.
Numerous non-idealities in gold processing are becoming increasingly significant with the depletion of free-milling oxide ores around the globe. Gold is mostly found in nature in metallic form and is associated with silver minerals and bae-metal sulphides. In the present thesis work, the role of silver minerals on gold cyanidation with base-metal sulphides was elucidated in detail on the relative importance of galvanic interactions and passivation phenomena. As the permanent galvanic contacts, inherently present within the ore grains, are hard to achieve between gold rotating disk electrode and slurried base-metal sulphide-rich ores, a packed-bed reactor (PBR) strategy was thus adopted to single out and quantify the virtual contributions of galvanic interaction and passivation effect on the gold and silver leaching rates during gold cyanidation with silver minerals and base-metal sulphides. The mixtures of gold, silver-minerals and sulphides were filled in the PBR to ensure the permanent particle-particle micro-electrical contacts among all ore constituents. Pyrite, chalcopyrite, sphalerite and stibnite were the sulphidic minerals investigated in the present gold-silver cyanidation study. Metallic silver (Ag), acanthite (Ag₂S) and pyrargyrite (Ag₃SbS₃), were the silver-minerals taken into account. Galvanic interactions were found to alleviate the leaching of gold and silver to various extents, for gold and silver minerals associated with pyrite and sphalerite, both under galvanic and passivation impact from the sulphide minerals. Silver minerals were found retarding to the gold leaching for chalcopyrite and stibnite minerals. Strategies were investigated to enhance the gold leaching kinetics in the presence of silver minerals and base-metal sulphides. Lead containing cyanide solution enhanced gold recovery and was found to neutralize significantly the negative effect of sulphidic minerals, particularly for chalcopyrite. Moreover, lead addition enhanced gold leaching kinetics significantly for gold and silver minerals associated with pyrite, chalcopyrite and sphalerite. Pre-treatment with alkaline lead acetate tested on sulphide associated mixtures of gold and silver minerals affirmed enhanced gold recovery in case of pyrite, chalcopyrite and sphalerite minerals. Stibnite found severely retarding towards gold dissolution with silver minerals. Surface obstructing films were observed on gold particles for gold cyanidation with silver minerals and base-metal sulphides in case of chalcopyrite and stibnite.

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Belissont, Rémi. "Germanium and related elements in sulphide minerals : crystal chemistry, incorporation and isotope fractionation". Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0049/document.

Testo completo

Abstract (sommario):

Le germanium est un métalloïde « stratégique » dans l’industrie high-tech, notamment pour la transition énergétique et le secteur des communications. Étant distinctement sidérophile, lithophile, chalcophile et organophile, le Ge possède un fort potentiel comme traceur géochimique. Ces travaux de thèse visent à améliorer la compréhension de la géochimie du cycle du Ge et des facteurs qui contrôlent son incorporation dans les minéraux et les gisements métalliques. Les cibles de cette étude concernent le gisement filonien à Zn de Saint-Salvy (Massif Central, France), le gisement filonien à Cu de Barrigão (Ceinture pyriteuse ibérique, Portugal), et le gisement à Zn–Cu de Kipushi (R.D. Congo). Les porteurs de Ge les plus importants sont respectivement la sphalérite (jusqu’à 2580 ppm), la chalcopyrite (jusqu’à 5750 ppm) et la réniérite (5,0–9,1 %). Les résultats montrent qu’il existe une relation de premier ordre entre la concentration en Ge dans la sphalérite et le type de gisement. La spectroscopie XANES par rayonnement synchrotron met en évidence la présence de Ge4+ en site tétraédrique dans les sulfures analysés. Les corrélations élémentaires observées dans la sphalérite et la chalcopyrite suggèrent une incorporation du Ge par co-substitutions, e.g., 3Zn2+ ↔ Ge4+ + 2(Cu,Ag)+ et 3Fe3+ ↔ 2Ge4+ + Cu+, ou via la création de lacunes cristallographiques, e.g., 2Zn2+ ↔ Ge4+ + ?. La corrélation positive δ74Ge–[Ge]ZnS des sphalérites de Saint-Salvy indiquerait que coefficient de partage (KdGe) augmenterai avec T. Les compositions isotopiques δ74Ge des sulfures étudiés varient de –5,72‰ à +3,67‰. Les compositions légères mesurées dans les gisements de Saint-Salvy et Barrigão semblent liées à des variations de température des fluides (basse à moyennes T) lors de l’incorporation de Ge en système ouvert, alors que la tendance marquée vers les compositions isotopiques lourdes à Kipushi indiquerait un fractionnement de Rayleigh
Germanium is a critical metalloid in many high-tech industries, especially for the energy transition and the communication sector. Being distinctly siderophile, lithophile, chalcophile and organophile, Ge can be a particularly useful geochemical tracer. This thesis aims at understanding the Ge geochemistry and the factors controlling its concentration in Ge-bearing minerals and ore deposits. Three contrasted Ge-bearing deposits were studied, the Saint-Salvy Zn vein-type deposit, French Massif Central, the Barrigão Cu vein-type deposit, Iberian pyrite belt, Portugal, and the Kipushi Zn–Cu carbonate-hosted deposit, Central African copper-belt, D.R. Congo. The most important Ge-bearing minerals are sphalerite (up to 2580 ppm Ge), chalcopyrite (up to 5750 ppm Ge), and renierite (5.0–9.1 wt.% Ge). The results show a first order relation between the Ge content and the deposition temperature. Synchrotron-based XANES spectroscopy showed that Ge4+ occur in tetrahedral sites in the studied sulphides. Element correlations suggest that Ge is chiefly incorporated in sphalerite and chalcopyrite through coupled substitutions, e.g., 3Zn2+ ↔ Ge4+ + 2(Cu,Ag)+ and 3Fe3+ ↔ 2Ge4+ + Cu+, respectively, or via the creation of lattice vacancies, e.g., 2Zn2+ ↔ Ge4+ + ?. The positive δ74Ge–Ge content correlation observed in sphalerite from Saint-Salvy could indicate that Ge partition coefficient (KdGe) increases with temperature. Ge isotopes in sulphides yield δ74Ge values spanning from –5.72‰ to +3.67‰. The light δ74Ge compositions of Saint-Salvy and Barrigão ores appear to be related to variations in low to moderate fluid temperatures during Ge uptake in open system (e.g., fluid cooling), while the trend towards heavy δ74Ge compositions observed at Kipushi likely translates a Rayleigh fractionation effect during ore formation in closed system, associated with significant fluid modification

Gli stili APA, Harvard, Vancouver, ISO e altri

17

Vilinská, Annamária. "Microbial adhesion and surface modifications of sulphide minerals relevant to flotation and flocculation /". Luleå : Division of Extractive Metallurgy, Luleå University of Technology, 2009. http://pure.ltu.se/ws/fbspretrieve/3328441.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

18

Witne, John Yagbinan. "The effects of oxygen and carbon dioxide enriched air on the bacterial oxidation of sulphide concentrates". Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302672.

Testo completo

Abstract (sommario):

Biohydrometallurgical techniques are quite established for the treatment of certain sulphide minerals and others have been demonstrated at laboratory or pilot plant scale level, where iron and sulphuroxidising bacteria are utilised for the leaching of low grade sulphide ores and the pretreatment of gold ores and concentrates. The majority of the microorganisms which are used for bacterial leaching are autotrophic aerobes, therefore carbon dioxide and oxygen are essential nutrients for their growth and survival, adequate supplies must be ensured in order for the oxidation process to be successful through an effective gas mass transfer process from air or other sources to the gas/liquid/solids interface in the pulp which can then be readily available to the microorganisms. Gas mass transfer limitation is one of the major problems faced by the industry therefore, most commercial biooxidation plants currently operate at low pulp densities at around 20 - 25% to minimise gas mass transfer limitations. Three cultures, a mesophile (DSM 583), a moderate thermophile (Y1FI) and a extreme thermophile iSulfolobus BC65) were used to bioleach the Ok Tedi copper concentrate under optimum Ch and CO2 enriched air (30% Ch and 10% CO2) based on volume ratios. The positive effect of using oxygen and carbon dioxide enriched air to bioleach the copper mineral was clearly demonstrated where an increase in Cu leaching rate by a factor of2.8, 2.1 and 1.9 for DSM 583, YTFI and Sulfolobus respectively were observed compared with the shake flask tests. The lag phase observed with the other test conditions such as in shake flask or with air, was eliminated when leached under optimum gas enrichment and 1t;80%of the Cu was extracted in the first 120 to 150 hours of leaching for all three cultures. The average dissolved oxygen concentrations observed in the pulp for these tests were 11.8, 8.0 and 7.2 mgll for DSM 583, YTFI and Sulfolobus respectively, indicating that O2 was not limiting in these tests. The Fe released during the bioleaching of copper was non stoichiometric for a predominantly chalcopyrite concentrate and the low redox potential values (max 638mV) suggested galvanic interaction during the leaching of copper where chalcopyrite was leached preferentially due to the presence of pyrite. Bioleaching of copper under optimum gas enrichment at different pulp densities showed near total copper extraction occurred for pulp densities of 3, 10 and 20% (w/v). At high pulp densities, more so at 40% than 30% (w/v), the leaching rate decreased rapidly for tests with YTFI and Sulfolobus. Monitoring of dissolved Ch shows that O2 demand increased with increasing pulp density and the average dissolved O2 concentration observed for DSM 583, YTFl and Sulfolobus at 40% solids concentration were 3.0, 2.6 and 2.4 mgll respectively, suggesting that oxygen and carbon dioxide are not limiting. The decrease in leaching rate observed at high pulp densities (30 & 40%) under optimum gas enrichment was accompanied by low metal dissolution and low redox potential values which was attributed to shear stress due to attrition of cells by high solids concentration, toxicity of metal ions especially Ag, Fe and Cu, and the formation of precipitates and jarosites as confirmed from XRD analysis of leach residues hence impeding the leaching process rather than as a result of O2 and C~ limiting conditions. The addition of flowing air increased the overall iron release rate for the Porgera gold-bearing pyrite concentrate by a factor of AJ 2.8, 1.8 and 1.5 for DSM 583, YTFl and Sulfolobus respectively compared with the shake flask tests, and the lag time was observed to decrease by about 80% for all cultures, suggesting O2 and CO2 limiting conditions in the shake flask. The average dissolved ~ concentration observed for the pulp with the different cultures were 8.7, 5.8 and 5.0 mgll for DSM 583, YTFI and Sulfolobus respectively indicating oxygen was not limiting in these tests. Biooxidation of pyrite concentrate under optimum gas enrichment at various pulp density shows DSM 583 performing well exhibiting the highest oxidation rate for all pulp densities, followed by YTFt and Sulfolobus, except at 3% pulp density where the rates are similar for all cultures. At high pulp density, above 30%, the oxidation rate decreased rapidly for YTFt and Sulfolobus, with DSM 583 showing a moderate decrease. Monitoring of dissolved oxygen showed that oxygen demand increased with increasing pulp density and at one point the dissolved oxygen concentration for the test with YTFI at 40% and Sulfolobus at 30 and 40% solids concentration decreased below t.O mgll, suggesting oxygen and carbon dioxide limiting conditions. The decrease in leaching rate at high pulp densities above 30% under optimum gas enrichment was accompanied by low Fe dissolution and low redox potential which was attributed to shear stress due to attrition of cells by high solids concentration, toxicity of metal ions especially Ag, and Fe. and the formation of precipitate andjarosites hence impeding the leaching process. Oxygen and CO2 limiting conditions due to high pulp density and viscosity were only observed for YTFt and Sulfolobus cultures. The cyanide leaching of the pretreated pyrite concentrate shows that the extent of gold and silver recovery increased with the degree of pyrite oxidation and Au and Ag recoveries in excess of 80% were achieved compared with that of only 18.1% and 35.94'10 for gold and silver respectively, from the original. untreated concentrate by direct cyanidation.

Gli stili APA, Harvard, Vancouver, ISO e altri

19

Sitoka, Stefanus. "Exploration status for oxide and sulphide zinc ores at Skorpion Zinc Mine, Namibia". Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1018204.

Testo completo

Abstract (sommario):

The thesis is inspired by recent interests in oxide zinc ores caused by new developments in the technology of hydrometallurgy. The improved techniques turned the non-sulphide zinc ores in to attractive exploration targets due to a number of advantages such as low metal recovery costs and favorable environmental aspects such as the obvious absence of sulfur (Large, 2001). Historically extraction of zinc metal from oxide ores was not possible until recently. The metallurgical complexity resulted in a lack of interest and hence some economic oxide zinc ores might have been missed by conventional exploration techniques. The study presents a review of exploration status at Skorpion mine based on different exploration techniques and their application to sulphide and oxide zinc ore exploration. The challenge facing the mineral exploration industry today is the inability to detect mineral deposits under cover. Therefore a key to successful exploration program lies in the selection of the right exploration technique. Important parameters that should be highlighted in the exploration methodology are the geological situation of an area, equipment applicability and effectiveness, survey limitation, equipment mobilization and the safety aspects involved. The aim of this thesis is to provide a general guideline for sulphide and non-sulphide zinc ore exploration on the Skorpion area and other similar geological environments. Geochemical surveys appears to be more complimentary in exploration of non-sulphide zinc exploration. Although geochemical techniques are preferred, it is equally important to choose the right soil horizon. Furthermore, sample media may mean the difference between success and failure in geochemical exploration of non-sulphide zinc mineralization, due to high mobility of zinc in the surficial environment. On cost comparison, surface geochemical surveys programs are more cost effective except for litho-geochemical sampling which are commonly carried out through subsurface drilling. Geophysical techniques have limited application in exploration of non-sulphide zinc mineralization due to a lack of major physical properties (e.g., magnetic and electrical properties) in non-sulphides unlike their sulphide counterparts. However geophysical methods are commendable in delineating massive and disseminated sulphides mainly if they are associated with major Fe minerals (pyrrhotite or magnetite). In addition, geophysical techniques may be effective in mapping of subsurface primary and secondary structures such as basin faults which might have acted as pathways for metal-rich fluids. Terms non-sulphide and oxide zinc mineralization are used interchangeably throughout the thesis. Recommendations on regional and local target generation are presented in the thesis to give some basic guide lines on target generation strategies. The most important conclusion reached in this study is that, success in exploration for non-sulphide or sulphide zinc mineralization might be enhanced through the integrated exploration methodology.

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Ayling, K. J. "Chloride leaching of complex sulphide minerals and recovery of copper using the C.E.E.R. cell". Thesis, Open University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253768.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Marsland, Simon David. "Non-oxidative dissolution of iron sulphide minerals : of relevance to inorganic chemical souring of oil reservoirs". Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326670.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Corkhill, Claire L. "The mineralogical and biogeochemical transformations associated with As-bearing sulphide minerals in acid mine drainage system". Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494293.

Testo completo

Abstract (sommario):

Arsenopyrite (FeAsS) and enargite (CU3ASS4) are the most common As-bearing sulphide minerals in acid mine drainage environments. Orpiment (AS2S3) and realgar (AsS) are also found. In the environment, these minerals are unstable under oxidising conditions, and significant concentrations of As can be released into groundwater upon weathering. Acidophilic bacteria such as Leptospirillum ferrooxidans have been shown to enhance the dissolution of sulphide minerals in these environments, and could therefore accelerate the release of arsenic.

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Warner, Terence Edwin. "An electrochemical study of the oxidative dissolution of synthetic nickel-iron sulphide minerals in aqueous media". Thesis, University of Leeds, 1988. http://etheses.whiterose.ac.uk/1075/.

Testo completo

Abstract (sommario):

Pentlandite (Fe4.5Ni4.5S8) and violarite (FeNi2S4) were synthesized by dry in vacuo techniques. The products were analysed by reflected light microscopy, powder X-ray diffraction and electron microprobe analysis. The synthetic pentlandite was found to have an average stoichiometry of Fe4.35Ni4.65S8. A partial phase segregation of pentlandite into heazlewoodite and pyrrhotite was observed. The synthetic violarite grains showed a zonal separation into a Fe1.2Ni1.8S4 core, and a Fe0.5Ni2.5S4 rim. Trace amounts of pyrite and millerite were also detected. From a critical review of the thermodynamic data in the literature, several Eh-pH diagrams were constructed for the Fe-Ni-S aqueous system. These were compared with mineralogical evidence obtained from naturally occuring mineral assemblages. A study of the oxidative dissolution of pentlandite by electrochemical techniques was made to clarify the mechanism by which pentlandite is leached in acid FeCl3 solution. The techniques used included: potentiometry, linear sweep cyclic voltammetry, intermittent galvanostatic polarization, chronopotentiometry and chronoamperometry. The products were analysed using scanning electron microscopy, powder X-ray diffraction, electron microprobe analysis, atomic absorption spectroscopy and gravimetric analysis. The fitting of experimental results to a simple electron transfer model via the Sand equation was tested and found to be inappropriate. A mechanism for the oxidative dissolution of pentlandite is postulated. In acid solution, pentlandite decomposes spontaneously, liberating aqueous metal ions and H2S. Under potentiostatic conditions akin to FeC13 leaching, pentlandite is oxidized directly to elemental sulphur, without the formation of any intermediate phases. The lack of formation of violarite indicates that the system is substantially perturbed from equilibrium due to slow solid state diffusion of metal atoms within the sulphur sublattice. The formation of metastable amorphous sulphur as the alternative product is further evidence of this perturbation. The physical properties of the sulphur product layer cause an impediment to mass transport between the bulk aqueous solution and the mineral surface. However, the oxidation involves an intrinsically slow 'electron transfer for the So, Fe2+, Ni2+ / Fe4.5Ni4.5S8 couple which, within the potential range relevant to FeCl3 leaching, is rate determining for an appreciable part of the reaction. The implication for extractive hydrometallurgy is discussed. The use of a convolution transform of voltammetric currents with a (πt)-1/2 function as applied to simple electron transfer is described. In addition, the derivation of a functional form for the treatment of chronoamperometric data is given. These models were applied in the determination of the heterogeneous electrochemical parameters and diffusion coefficients for the FeC13/FeC12 couple in 1M HC1 solution on platinum at 293K, using computer controlled chronoampermetric techniques. The results show quasi-reversible behaviour (at 293K), which implies that electron transfer for this couple would not be rate determining in the leaching of pentlandite.

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Čiutelytė, Rūta. "Biogas yield and quality improvement and purification with natural minerals". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20131004_191808-62516.

Testo completo

Abstract (sommario):

Research goal and objective. To investigate the possibilities of the use of mineral raw materials of local origin for the purification of biogas produced from sewage sludge, by-products and waste and to assess the environmental benefits of the use of biogas in the transport sector. The properties of by-products and waste generated in Lithuania as well as the possibilities of their use in the production of biogas from sewage sludge have been assessed. The potential and properties of local mineral raw materials suitable for the purification of biogas have been assessed. The process of the removal of hydrogen sulphide and carbon dioxide from biogas using natural sorbents has been investigated. It was found that large dolomite resources available in Lithuania allow using this natural raw material for biogas purification because sorbent solutions and suspensions of dolomite powder effectively remove hydrogen sulphide and absorb carbon dioxide from biogas sufficiently quickly. A principal biogas purification technology was developed on the basis of the performed assessment of the process kinetic calculations. Engine perfomance tests were carried out using a mixture of biogas and mineral diesel fuel and exhaust gas emissions were assessed.
Darbo tikslas – ištirti gamtinių sorbentų (vietinės kilmės mineralinių žaliavų) panaudojimo biodujų, pagamintų iš nuotekų dumblo, šalutinių produktų ir atliekų, valymui galimybes bei įvertinti biodujų panaudojimo transporto sektoriuje aplinkosauginę naudą. Įvertintos Lietuvoje susidarančių šalutinių produktų ir atliekų savybės bei panaudojimo biodujų gamyboje iš nuotekų dumblo galimybės. Įvertintos vietinės kilmės mineralinių žaliavų, tinkančių biodujų valymui, potencialas ir savybės. Ištirtas biodujų valymo nuo sieros vandenilio ir anglies dioksido procesas, naudojant gamtinius sorbentus. Nustatyta, kad Lietuvoje eantys dideli dolomito ištekliai leidžia panaudoti šią natūralią žaliavą biodujų valymui, nes absorbciniai tirpalai iš dolomito miltelių efektyviai pašalina sieros vandenilį ir pakankamai gerai sugeria anglies dioksidą. Remiantis atliktu proceso kinetinių skaičiavimų įvertinimu buvo parengta principinė biodujų valymo technologija. Atlikti stendiniai variklio bandymai naudojant biodujų ir mineralinio dyzelino mišinį bei įvertintos deginių emisijos.

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Whiteley, Robert School of Mines UNSW. "Electrical and seismic responses of shallow, volcanogenic, massive sulphide ore deposits". Awarded by:University of New South Wales. School of Mines, 1986. http://handle.unsw.edu.au/1959.4/28078.

Testo completo

Abstract (sommario):

SP, resistivity/IP and seismic refraction responses of the Woodlawn Orebody and Mt.Bulga Deposit are examined and compared. Both exhibit similar responses produced mainly by uneconomic and disseminated sulphide mineralization and host rock features, demonstrating that the magnitude and character of electrical and seismic responses are not reliable indicators of size and economic sulphide content of volcanogenic sulphide ores. SP, soil geochemistry and electrogeochemistry are found to be the most effective exploration methods followed by resistivity/IP and seismic refraction. The large SP responses over both ore zones are simulated using new methods which allowed the width and depth of oxidation to be computed. Conventional and compensation array resistivity responses best define the deposits. Computer simulation shows that dipole- dipole and Unipole arrays are most useful. First order IP responses are large and similar, but the ore zones are not easily distinguished from polarizable host rocks. Second order responses, at Woodlawn, better define these lithologies and cross-plots of EM coupling removed first order parameters prove useful. The supergene and gossan zones are defined as sources of electrical anomalies and correlate with interpreted SP sources. Seismic velocities of fresh Woodlawn ore samples indicate only small contrasts with host rocks. Refraction travel-time data are highly complex but host rocks are clearly distinguished by their seismic velocities. Both deposits appear as low velocity zones at the general bedrock level which are shallower and narrower than the electrical sources associated with the ore zones. Extensive model simulation shows that the Reciprocal interpretation method is most useful when compared to other time- term methods for refraction interpretation but has some limitations. Computer simulation shows the significance of non- critical refractions, diffractions and laterally hidden zones which define the lateral resolution of the refraction method. The results of this study and the interpretative techniques developed will assist the exploration for similar and deeper massive volcanogenic orebodies in comparable geological environments.

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Hulley, Vierah. "Reactions between country rock xenoliths and the magma of Uitkomst Complex, with implications for the origin of the sulphide mineralisation". Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-05282008-101011.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Ghavami-Riabi, Reza. "Geochemical exploration for base metal sulphide deposits in an arid environment (eastern Namaqua Metamorphic Province), South Africa". Thesis, Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-06192007-100552.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Koegelenberg, Corne. "Experimental evidence for sulphide magma percolation and evolution : relevant to the chromite bearing reefs of the Bushveld Complex". Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20043.

Testo completo

Abstract (sommario):

Thesis (MSc)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Pt mineralization within the Bushveld Complex is strikingly focused on the chromitite reefs, despite these horizons being associated with low volumes of base metal sulphide relative to Pt grade. Partitioning of Pt (Dsil/sulp) from silicate magma into immiscible sulphide liquid appears unable to explain Pt concentrations in chromitite horizons, due to the mismatch that exists between very large R factor required and the relevant silicate rock volume. Consequently, in this experimental study we attempt to gain better insight into possible Pt grade enhancement processes that may occur with the Bushveld Complex (BC) sulphide magma. We investigate the wetting properties of sulphide melt relevant to chromite and silicate minerals, as this is a key parameter controlling sulphide liquid percolation through the cumulate pile. Additionally, we have investigated how fractionation of the sulphide liquid from mono-sulphide-solid-solution (Mss) crystals formed within the overlying melanorite might affect sulphide composition and Pt grades within the evolved sulphide melt. Two sets of experiments were conducted: Firstly, at 1 atm to investigate the phase relations between 900OC and 1150OC, within Pt-bearing sulphide magma relevant to the BC; Secondly, at 4 kbar, between 900OC to 1050OC, which investigated the downwards percolation of sulphide magma through several layers of silicate (melanorite) and chromitite. In addition, 1atm experiments were conducted within a chromite dominated chromite-sulphide mixture to test if interaction with chromite affects the sulphide system by ether adding or removing Fe2+. Primary observations are as follows: We found sulphide liquid to be extremely mobile, the median dihedral angles between sulphide melt and the minerals of chromitite and silicate layers are 11O and 33O respectively. This is far below the percolation threshold of 60O for natural geological systems. In silicate layers sulphide liquid forms vertical melt networks promoting percolation. In contrast, the extremely effective wetting of sulphide liquid in chromitites restricts sulphide percolation. Inter-granular capillary forces increase melt retention, thus chromitites serve as a reservoir for sulphide melt. Sulphide liquid preferentially leaches Fe2+ from chromite, increasing the Fe concentration of the sulphide liquid. The reacted chromite rims are enriched in spinel end-member. This addition of Fe2+ to the sulphide magma prompts crystallization Fe-rich Mss, decreasing the S-content of sulphide melt. This lowers Pt solubility and leads to the formation of Pt alloys within the chromitite layer. Eventually, Cu-rich sulphide melt escapes through the bottom of the chromitite layer. These observations appear directly applicable to the mineralized chromitite reefs of the Bushveld complex. We propose that sulphide magma, potentially injected from the mantle with new silicate magma injections, percolated through the silicate cumulate overlying the chromitite and crystallized a significant volume of Fe-Mss. Chromitite layers functioned as traps for percolating, evolved, Cu-, Ni- and Pt-rich sulphide liquids. This is supported by the common phenomenon that chromitites contain higher percentages of Ni, Cu and Pt relative to hanging wall silicate layers. When in contact with chromite, sulphide melt is forced to crystallize Mss as it leaches Fe2+ from the chromite, thereby further lowering the S-content of the melt. This results in precipitation, as Pt alloys, of a large proportion of the Pt dissolved in the sulphide melt. In combination, these processes explain why chromitite reefs in the Bushveld Complex have Pt/S ratios are up to an order of magnitude higher that adjacent melanorite layers.
AFRIKAANSE OPSOMMING: Pt mineralisasie in die Bosveld Kompleks is kenmerkend gefokus op die chromatiet riwwe, alhoewel die riwwe geassosieer is met lae volumes basismetaal sulfiedes relatief tot Pt graad. Verdeling van Pt (Dsil/sulp) vanaf silikaat magma in onmengbare sulfiedvloeistof is klaarblyklik onvoldoende om Pt konsentrasies in chromatiet lae te verduidelik, a.g.v. die wanverhouding wat bestaan tussen ‘n baie groot R-faktor wat benodig word en die relatiewe silikaat rots volumes. Gevolglik, in die eksperimentele studie probeer ons beter insig kry oor moontlike Pt graad verhogingsprosesse wat plaasvind in die BK sulfied magma. Ons ondersoek die benattingseienskappe van sulfied vloeistof relevant tot chromiet- en silikaat minerale, omdat dit die sleutel maatstaf is vir die beheer van sulfied vloeistof deursypeling deur die kumulaat opeenhoping. Addisioneel het ons ook ondersoek hoe die fraksionering van sulfied vloeistof vanaf MSS kristalle, gevorm binne die hangende melanoriet muur, moontlik die sulfied samestelling en Pt graad binne ontwikkelde sulfied smelt kan beïnvloed. Twee stelle van eksperimente is gedoen: Eerstens, by 1 atm om ondersoek in te stel oor fase verwantskappe tussen 900OC en 1150OC, binne ‘n Pt-verrykte sulfied magma samestelling relevant tot die BK; Tweedens, by 4 kbar, tussen 900OC tot 1050OC, wat die afwaartse deursypeling van sulfied magma deur veelvuldige lae van silikaat minerale en chromatiet. Addisionele 1 atm eksperimente is gedoen binne ‘n chromiet gedomineerde chromiet-sulfied mengsel, om te toets of interaksie met chromiet die sulfied sisteem affekteer deur Fe2+ te verwyder of by te dra. Primêre observasies is soos volg: Ons het bevind sulfiedsmelt is uiters mobiel, die mediaan dihedrale hoek tussen sulfiedsmelt en minerale van chromiet en silikaat lae is 11O en 33O onderskydelik. Dit is ver onder die deursypelings drumpel van 60O vir natuurlike geologiese stelsels. In silikaatlae vorm die sulfiedsmelt vertikale netwerke wat deursypeling bevorder. Inteendeel, uiters effektiewe benatting van sulfiedsmelt binne chromatiete vertraag sulfied deusypeling. Tussen kristal kapilêre kragte verhoog smelt retensie, dus dien chromatiete as ‘n opgaarmedium vir sulfiedsmelt. S oorversadigte sulfied vloeistof loogsif Fe2+ vanuit chromiet en veroorsaak ‘n verhoging in Fe-konsentraie. Die gereageerde chromiet buiterante is daarvolgens verryk in Cr-spinêl eind-ledemaat. Die addisionele byvoeging van Fe2+ aan sulfied magma veroorsaak die kristalisasie van Fe-ryke Mss en verlaag dus die S-konsentrasie van die sulfied smelt. Dit verlaag Pt oplosbaarheid en lei tot die formasie van Py allooie binne-in chromatiete. Ten einde, ontsnap Cu-ryke sulfied smelt deur die onderkant van die chromatiet lae. Die observasies is direk van toepassing op die gemineraliseerde chromatiet riwwe van die Bosveld Kompleks. Ons stel voor dat sulfied magma, potensiaal ingespuit vanuit die mantel saam nuwe inspuitings van silikaat magma, deur die hangende silikaat kumulaat bo chromatiet lae deurgesypel het en ‘n betekenisvolle volume Fe-Mss gekristalliseer het. Chromatiet lae het gefunksioneer as lokvalle vir afwaartsbewegende, ontwikkelde, Cu-, Ni-, en Pt-ryke sulfied vloeistowwe. Dit word ondersteun deur die algemene verskynsel dat chromatiete hoër persentasies van Ni, Cu en Pt relatief teenoor die hangende muur silikaat lae het. Wanneer sulfied smelt in kontak is met chromiet, word dit geforseer om Mss te kristalliseer soos Fe2+ geloogsif word, waarvolgens die smelt se S konsentrasie verder verlaag word. Dit veroorsaak die presipitasie, as Pt allooie, van groot proporsies opgeloste Pt vanuit sulfied smelt. Deur die prosesse te kombineer, kan dit moontlik verduidelik word hoekom chromatiet riwwe in die Bosveld Kompleks Pt/S verhoudings veel hoër is as aanrakende melanoriet lae.

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Bonel, Kevin Anthony. "The mode of occurrence, recovery characteristics and petrogenesis of platinum-group and base metal sulphide minerals in the UG2 chromitite at Northam Platinum Mine, South Africa". Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297790.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Rapp, Andrei. "Undersökning av lakningspotential och kristallareafördelning av opaka mineral i bergarter från Ekobacken, Värmdö kommun". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-384007.

Testo completo

Abstract (sommario):

Ekobacken, Värmdö kommun, har problem med surt yt- och grundvatten med höga metallhalter. Uppmärksamheten har riktats mot berggrunden som krossats och lagrats i deponihögar. Bildningen av sur lak styrs av flertalet geokemiska egenskaper, bland annat vilka sulfidmineral som förekommer och deras kristallstruktur. Prover från Ekobacken har undersökts utifrån sulfidhalt, kristallarea för opaka mineral och surgörande potential för att kunna utröna om ett samband finns mellan kristallareafördelning och lakningsegenskaper. Proverna har mikroskopiskt undersökts i reflekterande ljus för att skilja ur vilka opaka faser som förekommer samt har tunnslip fotograferats för att bildanalysera de opaka faserna utifrån area och form. Ett statiskt laktest utfördes på proverna för att kvantifiera dess lakningsegenskaper. Resultatet visar att bergarterna bestod i stor del av kvarts, fältspat och biotit i olika fördelningar. Opaka faser som förekom var pyrit, grafit, kopparkis och magnetit. Bergarterna visade sig generellt ha hög sulfidhalt från ABA resultatet, där ett prov hade en halt på 0,61 vikt%, medan andra prov hade relativt hög bufferförmåga och därför ingen surgörande potential. Proverna som undersöktes visade sig vara likartade varandra i förhållande till kristallareafördelning av opaka faser och form. I den här studien gick ingen direkt korrelation mellan provens kristallareafördelning för opaka faser och lakningspotential att utröna
Ekobacken, Värmdö municipality, have a problem with acidic surface- and groundwater with high metal content. The attention has been directed towards the bedrock which have been crushed and stored in landfills. The production of acid drainage is controlled by multiple geochemical properties inter alia which sulphide minerals are present and the structure of crystals. Samples from Ekobacken has been collected and analysed for sulphide content, crystal-area of sulphide minerals and acidic potential to investigate if there is a correlation between crystal-area distribution and leachability. The samples were examined under reflective light microscopy to determine the different opaque phases present and the thin sections were photographed for a photo analysis regarding crystal area and shape. A static leachability test was performed to be able to quantify the samples potential to produce acidic drainage. The results show that the samples contained mostly quartz, feldspars and biotite. Opaque phases present were pyrite, graphite, chalcopyrite and magnetite. ABA results showed high sulphide content, where one sample reached 0,61 wt. % sulphide content. Other samples contained relative high ability to buffer acidic reaction and thus showed no potential to produce acidic drainage. The samples were homogenous to each other with regard of crystal-area distribution of opaque phases and aspect-ratio of individual crystals and in this study no direct correlation between the sample’s crystal-area distribution of opaque phases and potential to produce acidic drainage was apparent.

Gli stili APA, Harvard, Vancouver, ISO e altri

31

Seat, Zoran. "Geology, petrology, mineral and whole-rock chemistry, stable and radiogenic isotope systematics and Ni-Cu-PGE mineralisation of the Nebo-Babel intrusion, West Musgrave, Western Australia". University of Western Australia. School of Earth and Geographical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0202.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Nanthakumar, Balakrishnan. "Use of silica sol in selective sulphide mineral flotation". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32969.

Testo completo

Abstract (sommario):

Micro- and batch flotation tests were conducted to explore the use of silica sol to control metal ions to reduce accidental activation and misplacement of minerals. As a comparison other 'metal control reagents', ethylenediaminetetraacetic acid (EDTA) and polyphosphate were also tested. X-ray photoelectron spectroscopy (XPS) was used to probe the silica sol-mineral interaction mechanism.
Micro flotation was performed on single mineral samples over a pH range 7 to 11. It was found that silica sol depressed all Cu minerals, Cu and Pb activated pyrite and Pb activated sphalerite but did not depress Cu activated sphalerite. XPS analysis revealed that silica sol adsorbed on all Cu minerals and Cu and Pb activated pyrite. Silica sol partially removed Pb from Pb activated sphalerite and had no apparent interaction with Cu activated sphalerite. The depressant action, therefore, appeared to be primarily adsorption of silica sol to form hydrophilic sites.
In the batch tests, generally, silica sol, polyphosphate and EDTA increased the rate of flotation in the Cu stage and in the Zn stage. This is attributed to removal of hydrophilic metal hydroxy species, i.e., surface 'cleaning'. Polyphosphate, and to a lesser extent EDTA, improved selectivity in the Zn stage for Les Mines Selbaie and Mine Louvicourt and arguably for Hudson Bay Mining and Smelting. This selectivity was not identified in the trials at Brunswick Mine directly on Zn stage flotation feed. The varying effect of polyphosphate on selectivity is attributed to the level of 'excess Cu' used in Zn activation: the higher the excess, the greater the effect of polyphosphate. In conclusion, silica sol has some metal ion control capability but seems less attractive in this role than say polyphosphate.

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Javadi, Alireza. "Sulphide mineral flotation : a new insight into oxidation mechanisms". Licentiate thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25773.

Testo completo

Abstract (sommario):

Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, by sulphide minerals during grinding was investigated. It was found that pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite ((Zn,Fe)S), and galena (PbS), which are the most abundant sulphide minerals on Earth, generated H2O2 in pulp liquid during wet grinding in the presence or devoid of dissolved oxygen in water and also when the freshly ground solids are placed in water immediately after dry grinding. Pyrite generated more H2O2 than other sulphide minerals and the order of H2O2 production by the minerals found to be pyrite > chalcopyrite > sphalerite > galena. The pH of water influenced the extent of hydrogen peroxide formation where higher amounts of H2O2 are produced at highly acidic pH. The amount of H2O2 formed also increased with increasing sulphide mineral loading and grinding time due to increased surface area and its interaction with water. The sulphide surfaces are highly catalytically active due to surface defect sites and unsaturation because of broken bonds and capable of breaking down the water molecule leading to hydroxyl free radicals. Type of grinding medium on formation of hydrogen peroxide by pyrite revealed that the mild steel produced more H2O2 than stainless steel grinding medium, where Fe2+ and/or Fe3+ ions played a key role in producing higher amounts of H2O2.Furthermore, the effect of mixed sulphide minerals, i.e., pyrite–chalcopyrite, pyrite–galena, chalcopyrite–galena and sphalerite–pyrite, sphalerite–chalcopyrite and sphalerite–galena on the formation of H2O2 showed increasing H2O2 formation with increasing pyrite fraction in chalcopyrite–pyrite composition. In pyrite–sphalerite, chalcopyrite–sphalerite or galena–sphalerite mixed compositions, the increase in pyrite or chalcopyrite proportion, the concentration of H2O2 increased but with increase in galena proportion, the concentration of H2O2 decreased. Increasing pyrite proportion in pyrite–galena mixture, the concentration of H2O2 increased and also in the mixture of chalcopyrite–galena, the concentration of H2O2 increased with increasing chalcopyrite fraction. The results of H2O2 formation in pulp liquid of sulphide minerals and mixed minerals at different experimental conditions have been explained by Eh–pH diagrams of these minerals and the existence of free metal ions that are equally responsible for H2O2 formation besides surfaces catalytic activity. The results also corroborate the amount of H2O2 production with the rest potential of the sulphide minerals; higher is the rest potential more is the formation of H2O2. Most likely H2O2 is answerable for the oxidation of sulphide minerals and dissolution of non-ferrous metal sulphides in the presence of ferrous sulphide besides the galvanic interactions. This study highlights the necessity of revisiting into the electrochemical and/or galvanic interactions between the grinding medium and sulphide minerals, and interaction mechanisms between pyrite and other sulphide minerals in terms of their flotation behaviour in the context of inevitable H2O2 existence in the pulp liquid.
Godkänd; 2013; 20130412 (alijav); Tillkännagivande licentiatseminarium 2013-05-06 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Alireza Javadi Ämne: Mineralteknik/Mineral Processing Uppsats: Sulphide Mineral Flotation: A New Insight Into Oxidation Mechanisms Examinator: Professor K. Hanumantha Rao, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Professor Jan D. Miller, University of Utah, Department of Metallurgical Engineering, Mines and Earth Sciences-Dean, USA Tid: Tisdag den 4 juni 2013 kl 10.00 Plats: F531, Luleå tekniska universitet

Gli stili APA, Harvard, Vancouver, ISO e altri

34

Yang, Ying Ping. "Electromagnetic characteristics of synthetic rocks, and sulphide and oxide mineral assemblages". Thesis, The University of Sydney, 1995. https://hdl.handle.net/2123/26849.

Testo completo

Abstract (sommario):

An understanding of the electromagnetic characteristics of sulphide-bearing and magnetite-bearing rock and ore samples is important in the interpretation of electromagnetic (EM) exploration data. In this research study of electromagnetic conductivity characteristics, a theoretical measurement basis was developed, synthetic analogue materials were studied and the theory and analogue results were related to rock samples of varied mineralogy, texture and mineral concentration. The theory developed for cylindrical core sample EM measurements agreed with experiments performed on standard conductive samples using a multi-frequency coilbridge system in the 10 kHz to 4 MHz range. Skin effect was an important limitation to EM measurements on conductive (o > 1000 S/m) core samples but can be effectively monitored by spectral measurements. Measurements on 104 synthetic cores, of five types, revealed the relationship between apparent EM conductivity and the structure and arrangement of the conducting materials. These analogue cores contained a range of conductors, including copper wires, graphite powder, aluminium particles and magnetite/ilmenite grains, set in a matrix of insulating plaster or wax, representing models of layered, stringer, disseminated, network, massive and magnetite-rich mineralisation. A mechanism attributed to magnetic loss produced unrealistically high EM apparent conductivities for magnetite—bearing samples, especially at low frequencies (f < 100 kHz). For a conductive magnetite sample (6 > 1 S/m), the effect of magnetic loss can be eliminated at high frequencies (f > 400 kHz) and the ohmic conductivity of the magnetite sample can then be estimated. A total of 254 sulphide—bearing and magnetite-rich samples from 15 different geological environments constituted the natural materials used in this research. The sulphides, including chalcopyrite, pyrite, galena, sphalerite and pyrrhotite, and magnetite occurred in varying proportions and diverse fabrics in these samples. Complementary measurements of galvanic conductivity, density and magnetic susceptibility and thin section mineralogy results provided essential auxiliary information for the analysis of the EM data. The electrical conductivity of a rock is controlled by its mineralogy, mineral habit, mode of connectivity of conducting minerals and rock fabric. Texture may have an overwhelming effect on the EM and galvanic conductivities of rock samples. The conductivities of the massive sulphides studied ranged from thousands of S/m to a few tens of thousands of S/m for pyrrhotite, hundreds of S/m to thousands of S/m for chalcopyrite and galena, and a few S/m to hundreds of S/m for pyrite. Sulphide-free magnetite-bearing rocks generally are, at best, only moderate conductors (l S/m to 10 S/m) and then only with a large proportion of magnetite. Coarse grainsize in massive magnetite significantly enhances conductivity (up to hundreds of S/m). There is a clear contrast in the conductivity behaviour of networks and discrete aggregations of conducting minerals. When pyrrhotite is present, it usually dominates the conductivity response. Chalcopyrite also makes an effective contribution, whereas pyrite and magnetite often do not. Conductivity modelling of concentration variations can be achieved using appropriate empirical relations for different cases. For dispersed conducting euhedral cubic minerals such as pyrite or magnetite, Maxwell's mixing law can be applied. When a conducting material, such as pyrite or magnetite, changes from a dispersed phase to conductive channels with increasing concentration, percolation theory can be applied The observed critical concentrations, where the conducting minerals start to change from dispersed phases to continuous phases electrically, are 20 percent to 50 percent for pyrite, 40 percent to 80 percent for magnetite. For pyrrhotite or Chalcopyrite, present as continuous conducting minerals, it appears that a power law can be applied and the power exponent may vary between 1.5 and 5.5, depending on the conducting network structure. For a laboratory core sample with dispersed conducting particles, the calculated and observed diminution of measured EM conductivity with an increase in diameter of the sample suggests that EM exploration methods may not work well in conductivity prospecting for a disseminated target. For a heterogeneous mineralised rock sample, applications of laboratory—determined EM conductivity to field situations generally need to take account of the structure or texture of the conducting minerals. The research results of this thesis are intended as a contribution to the understanding of laboratory electromagnetic conductivity measurements. The results have important applications to the designs and evaluations of field-based EM systems in the exploration for metallic lustre sulphide and oxide economic mineral deposits in a variety of geological settings.

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Quezada, Reyes Víctor Alejandro. "Pretreatment to the leaching of copper sulphides minerals in oxidizing media". Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/670663.

Testo completo

Abstract (sommario):

La producción chilena de cobre procede de la hidrometalurgia y la concentración; el concentrado de cobre es tratado tradicionalmente mediante pirometalurgia. De acuerdo a Cochilco, el cobre producido en el año 2019, vía hidrometalurgia, fue un 27.3% del cobre chileno producido. Sin embargo, se prevé que esta aporte baje a un 11.6% para el año 2029, debido al agotamiento de los óxidos de cobre y la aparición de los sulfuros, principalmente calcopirita, siendo este mineral refractario a condiciones convencionales de lixiviación. Una opción para mejorar la eficiencia de lixiviación es el pretratamiento, especialmente el efecto del tiempo de curado. Esta variable mejora la cinética de disolución, principalmente en minerales sulfurados de cobre, sin embargo, existe escasa investigación al respecto. Estudios sobre el pretratamiento evalúan el efecto en la eficiencia de lixiviación pero no antes. Además, las reacciones que gobiernan estos fenómenos no han sido identificadas. Así, el objetivo de esta tesis es la evaluación del efecto del curado ácido en la extracción de cobre desde minerales sulfurados en condiciones oxidantes y en la presencia de cloruro. Muestras puras de calcopirita, calcosina y un mineral industrial de mina han sido utilizadas. Se desarrollaron pruebas evaluando el efecto del tiempo de curado y la concentración de KNO3, NaCl y H2SO4 y analizadas por ANOVA (calcopirita). Los productos formados en el pretratamiento (aglomerados) se caracterizaron utilizando diversas técnicas, tales como: Difracción de rayos X, Microscopio electrónico de barrido y Microscopia de luz reflejada. Además, el efecto del pretratamiento ha sido evaluado en la eficiencia de lixiviación a varias temperaturas, los residuos de lixiviación también han sido caracterizados. En el pretratamiento, el mineral de calcopirita y de mina, bajo las condiciones utilizadas en este estudio (15 kg/t of H2SO4, 25 kg/t of NaCl y 15 días de tiempo de curado), los siguientes productos fueron identificados: CuSO4, NaFe3(SO4)2(OH)6, Cu2Cl(OH) y S. Sobre la calcosina, bajo las condiciones utilizadas en este estudio, con 30 kg/t of H2SO4, 40 kg/t of NaCl y 7 días de tiempo de curado, los productos identificados fueron: Cu1.75S, Cu(OH)Cl, Na2SO4 and CuSO4. Finalmente, el pretratamiento mejora la eficiencia de lixiviación, entre 4 y 6%, alcanzando una extracción de cobre de 94% desde la calcopirita a 90 °C, fortaleciendo la hidrometalurgia como alternativa de tratamiento para minerales sulfurados de cobre.
Copper production in Chile is developed by hydrometallurgical and concentration; copper concentrates are traditionally treated by the pyrometallurgical route. According to Cochilco, copper produced in 2019 by hydrometallurgical process represent a 27.3% of Chilean total copper production. However, this contribution is estimated to decrease to 11.6% by 2029, due to the depletion of copper oxides and the appearance of copper sulphides, mainly chalcopyrite, being this mineral refractory to conventional leaching conditions. An alternative to improve leaching efficiency is pretreatment prior to leaching, especially the effect of curing time. This variable can increases the kinetics of copper extraction, especially in sulphides ores, however, there is limited research about it. Studies on pretreatment evaluate the effect on leaching efficiency but not previous leaching. Furthermore, the reactions that govern this phenomenon have not been clearly identified. Therefore, the objective of this thesis is the evaluation of the effect of acid curing on the copper extraction from sulphides minerals in oxidizing media and in presence of chloride. A pure sample of chalcopyrite, chalcocite and a mine ore were used. Tests evaluating the effect of curing time, KNO3, NaCl and H2SO4 concentration have been carried out. The chalcopyrite sample effect was evaluated by ANOVA. The product generated in the pretreatment (agglomerates) has been characterized using different characterization techniques, such as: X-Ray diffraction, Scanning Electron Microscopy and Reflection Optical Microscopy. Furthermore, the effect of pretreatment has been evaluated on the leaching efficiency at different temperatures, leaching residues have also been characterized. In the pretreatment of the chalcopyrite sample and mine ore, under the conditions of 15 kg/t of H2SO4, 25 kg/t of NaCl and 15 days of curing time, the following products were identified: CuSO4, NaFe3(SO4)2(OH)6, Cu2Cl(OH) and S0. Regarding the chalcocite sample, under the conditions of with 30 kg/t of H2SO4, 40 kg/t of NaCl and 7 days of curing time, the following products were identified: Cu1.75S, Cu(OH)Cl, Na2SO4 and CuSO4. Finally, copper sulphides ore pretreatment improved leaching efficiency, between 4 and 6%, reaching a copper dissolution of 94% from chalcopyrite at 90 °C, strengthening the hydrometallurgy as an alternative treatment for copper sulphides ores.

Gli stili APA, Harvard, Vancouver, ISO e altri

36

Alarcon, Leon Edgardo. "Pyrite weathering and lithium (Li?) transport under unsaturated flow conditions in model and mine-tailing systems". University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0011.

Testo completo

Abstract (sommario):

[Truncated abstract] As mineral deposits continue to be mined, the non economic gangue materials such as sulphides (e.g. pyrite) that are extracted as part of the ore body or overburden are deposited within the waste rock and/or milled tailings. As a result of natural weathering processes, these reactive materials represent a potential hazard to surrounding environments. A major consequence, resulting from mine-waste impoundments containing sulphidic materials, relates to the offsite movement of low pH leachates containing elevated concentrations of metal ions posing a contamination threat. The processes and mechanisms acting in the formation of acid mine drainage (AMD) are highly variable and, to a high extent, controlled by climatic conditions as the main driver of water flow and wetness of the system which in turn determines the availability of oxygen as well as water for pyrite weathering. In particular, this thesis is based on the hypothesis that in semiarid and arid climates the acid production may be water … The experiments were repeated at different water contents ranging from 0.24 to 0.33 cm3 cm-3. Breakthrough curves (BTC) of Li+, K+, Ca2+, Mg2+, Na+ and pH were measured and described with models of different complexities. This included the use of a simple linear and non-linear isotherms for Li+ alone, a binary Li+ - K+ ion exchange, and a complete multicomponent chemical equilibrium description of ion transport. The latter, by including dissolution of primary minerals which released base cations such as Mg2+, Ca2+ and K+ explained some of the elution patterns of base cations for which the Li+ - K+ exchange was the dominant process. Furthermore, under unsaturated water flow conditions, retardation of Li+ increased with decreasing water content. Thus solute mobility in mafic rock tailings appears to decrease under strongly unsaturated water flow conditions.

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Vigânico, Eunice Maria. "Protótipo em escala piloto para produção de sulfato ferroso a partir de concentrado de pirita da mineração de carvão". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/117757.

Testo completo

Abstract (sommario):

O presente trabalho teve como objetivo desenvolver um protótipo para a produção hidrometalúrgica de sulfato ferroso heptahidratado (FeSO4.7H2O – melanterita). A matéria prima foi um concentrado de pirita obtido a partir de rejeitos do beneficiamento de carvão mineral. Construiu-se, em escala piloto, uma planta de lixiviação com 300 kg de um concentrado com 73,2% de pirita. Nesta unidade, realizou-se uma etapa de lixiviação com água, em circuito fechado, sob condições aeróbias, com o intuito de se obter um extrato aquoso rico em íons férrico e sulfato. A seguir, procederam-se mudanças no sistema de forma a estabelecer uma condição anaeróbia ao meio, transformando os íons férricos em ferrosos. O lixiviado, rico em Fe2+, foi precipitado na forma de sulfato ferroso heptahidratado pela adição de etanol. Esse precipitado foi submetido a uma etapa de recristalização, obtendo-se cristais de melanterita de maior pureza. Ambos os produtos foram caracterizado por análise química elementar e difração de raios X. Os cristais de melanterita recristalizados apresentaram alta pureza, com qualidade para uso químico e farmacêutico. Assim, desenvolveu-se uma nova rota para produção de sulfato ferroso tendo como matéria-prima um concentrado de pirita da mineração de carvão (usualmente o sulfato ferroso é produzido como coproduto da produção de ilmenita e aço). A tecnologia apresenta uma elevada conversão do ferro lixiviado em melanterita e os insumos necessários são pirita, água e álcool etílico. A proposta abre uma nova possibilidade de uso dos rejeitos de carvão e a possibilidade de comercialização de outro produto na cadeia produtiva de carvão mineral.
The aim of this work was to develop a prototype for hydrometallurgical production of ferrous sulfate heptahydrate crystals (FeSO4.7H2O – melanterite). The raw material was a pyrite concentrate obtained from a coal tailing. The leaching system was assembled in pilot scale with 300 kg of a concentrate with 73.2% pyrite. Initially, it was carried out a leaching step in aerobic conditions with the purpose to obtain an aqueous solution rich in ferric ions and sulfate. Next, modifications were proceeded to establish an anaerobic condition in the reactor, converting the ferric to ferrous ions. Ethanol was added to the leaching solution to provide the precipitation of the Fe2+ and sulfate as ferrous sulfate heptahydrate. The ferrous sulfate precipitate was recrystallized, allowing producing melanterite crystals of higher purity. The crystals were characterized in terms of chemical and mineralogical composition. The process allowed producing crystals with a high purity attending chemical and pharmaceutical purposes. Thus, it was developed a process to produce ferrous sulfate from coal wastes (usually, ferrous sulfate crystals are produced as a co product from titanium dioxide and steel production). The technology presents a high conversion factor of soluble Fe2+ to melanterite and the necessary incomes are pyrite, water, and ethylic alcohol. The hydrometallurgical technique applied in this study allowed production of a commercial grade product from coal mining waste material.

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Adegoke, Idowu Abiodun. "Experimental studies on hydrothermal mineral replacement of bornite by copper sulphides". Thesis, Adegoke, Idowu Abiodun (2021) Experimental studies on hydrothermal mineral replacement of bornite by copper sulphides. PhD thesis, Murdoch University, 2021. https://researchrepository.murdoch.edu.au/id/eprint/60897/.

Testo completo

Abstract (sommario):

Pseudomorphic mineral replacement reactions occur in numerous geological processes (e.g. metamorphism, metasomatism, ore deposition, and chemical weathering) and anthropogenic processes (e.g., reservoir acidification, CO2 sequestration, acid mine drainage, materials syntheses, and minerals processing). Therefore, the understanding of the mechanism and kinetics of these reactions is important not only to geosciences but also to industrial applications. These reactions involve the replacement of a primary mineral by a product mineral in the presence of a fluid phase, with the product mineral preserving the external dimension of the primary mineral. In the early years, solid-state diffusion (SSD) was proposed as the main mechanism for such reactions, while over the past 20 years the importance of coupled dissolution-reprecipitation (CDR) mechanism has been recognized, especially at low temperatures when SSD is assumed to be a very slow process. However, it has recently been recognized that in some mineral replacement reactions the rate of solid-state diffusion can be comparable to the rate of dissolution-reprecipitation, and hence complex mineral textures can be produced from a synergy between SSD and fluid-mediated CDR processes. The interplay between SSD and CDR mechanisms has profound implications in our interpretations of petrological and geological observations, yet it has not been adequately studied so far. Also, the role of the bulk hydrothermal fluids in the formation of lamellae textures by solid-state diffusion process in parent phases that are free of fluid inclusions is still not well elucidated. These and other issues were addressed in this present study. Thus, to better understand the interaction between SSD and CDR reactions, the replacement of bornite (Cu5FeS4) by copper sulphides was used as a model system. In the present thesis, a series of experimental studies have been conducted into the mineral replacement reactions of bornite by copper sulphides to obtain an insight into the kinetics and mechanisms of the replacement reactions, as well as the formation and evolution of porosity during the replacement reactions. The outcomes of these sets of experiments are summarised below: In Chapter 2, the hydrothermal dissolution and replacement of bornite by copper sulphides was studied experimentally in pH 1 solutions at three temperatures (160, 180 and 200 °C) under anoxic conditions, and the effects of background additives (Na2SO3, CuSO4, CuCl2 and CuCl) on the replacement pathway were established. The results revealed that the reaction firstly involved the decomposition of bornite to form chalcopyrite (CuFeS2) lamellae and digenite-I (Cu9S5) via fluid-induced solid-state diffusion (FI-SSD) of Fe3+ from bornite structure. As the reaction progresses, chalcopyrite was later replaced by the second generation of digenite (digenite-II). Subsequently, both digenite-I and -II were replaced by covellite (CuS) and/or chalcocite (Cu2S) via the CDR reaction mechanism, depending on the experimental conditions. In addition, nantokite (CuCl) and atacamite (Cu2Cl[OH]3) formed due to the reaction between the dissolved copper with Cl-rich hydrothermal fluids. The observed replacement reactions at the rim and along fractures, the preservation of the external shape of the original bornite grain, and the presence of porosity in the product phase are characteristic features of the CDR mechanism. The first critical finding from this set of experiments is the fluid-induced exsolution of chalcopyrite lamellae and digenite from bornite. This is because the exsolution rate and lamellae size were sensitive to the composition of the fluids, and no exsolution was observed in the heating experiment in the absence of fluid. This FI-SSD mechanism is made possible by the near-identical topology of the crystal structure of bornite, chalcopyrite and digenite. Secondly, the replacement of bornite is multi-step but proceeds via different pathways under the various conditions studied. The interplay between the FI-SSD and CDR mechanisms resulted in complex reactions which cannot be easily predicted empirically. In Chapter 3, a combined kinetic, textural and mineralogical study of the replacement of bornite by copper sulphides under oxic conditions is presented, in order to obtain insights into the competing reactions between FI-SSD and CDR reactions under oxic conditions. The mechanism and kinetic behaviour of the reactions were described by exploring the effects of key variables including pH (1-6), temperature (160, 180 and 200 °C) and time on the reaction kinetics, and on the evolution of mineralogy and sample textures. Like the anoxic experiments, the resulting textures under oxic conditions also revealed the interplay between the FI-SSD and CDR mechanisms during the replacement of bornite. However, the most important distinctive difference from the anoxic conditions is that the ICP-OES results suggests both Cu and Fe removal into the solution at pH 1, and predominantly Cu-removal at pH 2, 3 and 5 during the FI-SSD under oxic conditons as against predominantly Fe-removal under anoxic condtions. The kinetic behaviour shows a complex dependence on various physical and chemical parameters including temperature, pH and contact time. For example, the result revealed that the reaction rate increases with temperature at pH 1 to 3, and decreases with temperature at pH 4 to 6. This change in reaction trend is linked to a change in the rate-limiting step of the reaction. For the effect of pH, the rate decreases with increasing pH from 1 to 6 at 180 and 200 °C, while the results show a complex effect of pH at 160 °C. There are several important findings from Chapter 3: (1) the dissolution and the replacement of bornite under oxic conditions not only changed with pH but also with temperature, (2) bornite is relatively kinetically stable at higher pH 4-6, while pervasive fast replacement/dissolution of bornite was observed at lower pH (1-3), and (3) the exsolution rate and lamellae distribution is dependent on pH, indicating a FI-SSD mechanism. In Chapter 4, the formation and evolution of porosity during the replacement of bornite by copper sulphides under anoxic and oxic conditions were monitored using combined (ultra) small-angle neutron scattering (USANS/SANS) measurements and microscopic textural examinations. The USANS/SANS measurements were carried out under both dry conditions and after filling the open pores with contrast matching D2O-H2O fluid, which made it possible to differentiate open pores from closed pores. The reactions created pores in the product phases, and all samples contained pores with very broad size distributions from nano to micrometre. Nearly all small pores (<20 nm) were closed while larger pores were mostly open. The textures resulted from the FI-SSD process are largely non-porous, while the products from CDR reactions presents high porosity. Porosity generation in the product phase(s) is due to molar volume and relative solubility differences between the parent and the replacing phase. Porosity dropped at the initial stage of the reaction, but increased again with the progressive replacement, reaching a maximum at complete replacement, and then porosity slowly dropped again, showing porosity creation during the replacement and evolution after the replacement reaction. Therefore, this study provides another experimental evidence demonstrating the transient and dynamic nature of porosity during mineral replacement reactions. Porosity coarsening also occurred during and after replacement reactions, likely driven by surface energy minimization via Ostwald ripening. Overall, this experimental study provides new insights into the physical chemistry of bornite replacement in nature. The documented mineralogical and textural differences could be used as one of the paleoproxies of the chemistry (including pH) and temperature of the fluids responsible for the alteration of copper minerals and remobilization of metals in ore deposits. Particularly, this study shows that mineral replacement can proceed via the synergy between SSD and CDR mechanisms; this happens at geologically low temperatures (≤200˚C) in the chalcogenide systems under both anoxic and oxic conditions, and may be used to interpret observations in other mineral systems such as the silicate systems at amphibolite or eclogitic metamorphic grades. This study also provides insights about porosity formation and evolution in copper-iron sulphides interacting with hydrothermal fluids, and how different reaction mechanisms contributes to porosity evolution, suggesting that mineral porosity can evolve and may be annealed out over geological timescale.

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Hildyard, Rebecca Christine. "The Textures and Microstructures of the Calcium Sulphate Minerals Anhydrite Gypsum and Bassanite". Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526946.

Testo completo

Abstract (sommario):

Evaporitic rocks containing minerals such as anhydrite, gypsum and bassanite, are of central importance in a number of geological scenarios. They play an important role in localizing deformation, acting as detachment horizons in many foreland fold and thrust belts, implying that their strength is generally lower than other rocks. Characterizing the microstructure of evaporites is therefore important for interpreting the larger scale deformation history of these rocks. Dehydration reactions of high grade metamorphic rocks, e.g. serpentinite, in subduction zones, are thought to be one mechanism that can trigger seismicity. Similar dehydration reactions of hydrous gypsum to bassanite or anhydrite can be used as analogues for these deeper scenarios. This thesis studies the microstructures of naturally deformed, coarse grained and fine grained anhydrite rocks from the Triassic Evaporites of the northern Apennines, using electron backscatter diffraction (EBSD). The technique was used to measure crystallographic preferred orientation (CPO) and misorientations both within grains and between grains. CPO and grain distortions within the coarse grained anhydrite rocks are found to be consistent with activity on the known (100)[001] easy slip system. It is found that there is little evidence of recovery although some dynamic recrystallization by grain boundary bulging is observed. CPO, grains distortions and misorientation distributions within the fine grained anhydrite rocks indicate activity of the (100)[010] and (001)[100] slip systems. Dynamic recrystallization by grain migration and sub-grain migration is inferred and evidence is found of a possible grain boundary sliding mechanism at the finest grain sizes. A suite of experimentally deformed and dehydrated Volterra gypsum samples are also analysed using EBSD. CPO in post-experiment bassanite is found to mimic the original gypsum c-axis orientation. Bassanite grain size is shown to relate to the degree of reaction overstep. In some samples two distinct morphologies of bassanite grains are found; large (0.5-2 mm), euhedral crystals and small «50 urn), acicular crystals, representing two different bassanite polymorphs.

Gli stili APA, Harvard, Vancouver, ISO e altri

40

Shackleton, Natalie Jean. "Surface characterisation and flotation behaviour of the platinum and palladium arsenide, telluride and sulphide mineral species". Doctoral thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5403.

Testo completo

Abstract (sommario):

Includes bibliographical references (leaves 170-181).
The Platreef is located in the northern limb of the Bushveld Complex of South Africa. This reef consists of a complex assemblage of rock types, with pyroxenites, serpentinites and calcsilicates being the most abundant. The predominant PGMs are the tellurides, arsenides, alloys and sulphides. The Pt and Pd tellurides contribute between 20-45% of the PGMs present in the Platreef ore followed by the alloys (26%), arsenides (21%) and sulphides (19%). Flotation is used in the processing of the Platreef ore to separate the siliceous gangue from the platinum group minerals (PGM) and base metal sulphides. The PGE arsenide and telluride minerals are considered to be slow floating when compared to other PGMs as there is evidence of them reporting to the tailings.This thesis aimed to investigate the flotation behaviour of these minerals and presents results which characterise the surface properties of synthetic cooperite (PtS), vysotskite (PdS), sperrylite (PtAS2), palladoarsenide (Pd2As), moncheite (PtPd(BiTe)2 and PtTe2) and merenskyite (PdPt(BiTe)2 and PdTe2) and attempts to relate the flotation behaviour of the various minerals to these characteristics.

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Bromfield, Lucinda. "Factors affecting the attachment of Metallosphaera hakonensis during the colonisation of low grade mineral sulphide heaps". Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10217.

Testo completo

Abstract (sommario):

This thesis pertains to the extraction of copper via heap bioleaching, focussing specifically on the bioleaching of the mineral sulphide, chalcopyrite (CuFeS2). Industrial heap bioleaching offers an attractive alternative to conventional extraction methods, such as smelting, for processing low grade ores. There remain a number of operational challenges associated with bioleaching heaps, such as the lag time before efficient extraction is achieved and ineffective heap inoculation, as well as the difficulty in controlling the conditions within the heap.

Gli stili APA, Harvard, Vancouver, ISO e altri

42

Wengorsch, Tobias. "Experimental Alteration in Composite Mineral Systems: Mg-silicates, Fe-Ni-sulphides and Fe-Ti-oxides". Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/78546.

Testo completo

Abstract (sommario):

This study provides new insight into fluid-mediated replacement reactions for three different mineral systems. Hydrothermal experiments were conducted at 150 °C and 240 °C. It was found that serpentinisation reaction kinetics and crystal morphology are dependent on fluid and solid composition. Furthermore, primary Ni-sulphides were transformed into high Ni-tenor assemblages and it was found that the generation of fracture networks within ilmenite is strongly affected by the presence of hematite.

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Kotsiopoulos, Athanasios. "Development of an unsteady state model for the tank bioleaching of sulphide mineral concentrates in flow reactor systems". Doctoral thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10849.

Testo completo

Abstract (sommario):

Includes bibliographical references.
In this thesis, it is hypothesized that in bioleaching flow reactor systems, high reaction rate regions exist that can be maintained by application of biological stress trajectories. Reactor models are developed for the purpose of optimising plant operation, understood here as maximising the production rate. Complicating this attempt are a) the non-linear dynamics associated with the kinetics and b) the primary reaction's being multiphase. Mathematical models are developed to establish which particle parameters are necessary to describe reactor performance using the method of segregation. The models are distinguished by the combination of either particle residence time or age and/or particle size distributions. The models evaluated at steady state are validated against pilot plant data obtained from the Fairview Mine in South Africa and were found to be in good agreement with the data. As the model was developed using a segregation approach and thus incorporates age distributions in the model formulation, the model could be extended to unsteady state operation.

Gli stili APA, Harvard, Vancouver, ISO e altri

44

Mamuse, Antony. "Spatial statistical estimation of undiscovered mineral endowment: case of komatiite-associated nickel sulphide resources, Kalgoorlie Terrane, Western Australia". Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/449.

Testo completo

Abstract (sommario):

The Kalgoorlie Terrane of the Yilgarn Craton, Western Australia, containing about 60% (~11 Mt) of the world’s known komatiite-hosted nickel sulphide resources, is the world’s best studied and economically most important province for this mineral deposit type. Although increasingly mature in terms of nickel exploration, the Kalgoorlie Terrane is believed to contain significant additional undiscovered nickel endowment. Using the data-rich Kalgoorlie Terrane, this thesis develops a benchmark methodology that combines geological knowledge with spatial analysis and mathematical-statistical methods to estimate undiscovered nickel resources.In the proposed methodology, nickel sulphide deposits are considered realisations of stochastic mineralisation processes and are analysed within the following framework. Komatiites in the Kalgoorlie Terrane constitute the full sample space or the permissive tract. Disjoint, naturally bound individual komatiite bodies that make up the sample space are used as the spatial analysis units. Some komatiite bodies within the sample space contain nickel sulphide deposits (mineralised) and others do not (unmineralised). In this study, the most explored mineralised komatiite bodies constitute local control areas against which nickel resources in the less explored komatiite bodies can be assessed. The concept of local control areas is analogous to the concept of global control areas which are well explored parts of permissive areas for particular deposit types worldwide.Spatial point pattern analyses showed that the spatial distribution of mineralised komatiite bodies within the sample space is clustered. In contrast, nickel sulphide deposits in individual komatiite bodies are either randomly distributed or dispersed, and not clustered. This absence of deposit clustering within individual komatiite bodies indicates that the intensity of the deposit pattern of each komatiite body may be adequately expressed as deposit density (number of deposits per km[superscript]2). In global quantitative resource assessments, regression analysis of the well established power law relationship between deposit density and size of global control areas provides a robust method for estimating the number of deposits.In this study a power law relationship reminiscent of that in global models was found between the sizes of control areas and deposit density. In addition, this study establishes another power law relationship between nickel endowment density (nickel metal per km[superscript]2) and the sizes of control areas. Deposit and endowment density regression models based on the two power laws suggested that, respectively, 59 to 210 (mean 114) nickel sulphide deposits and 3.0 to 10.0 Mt (mean 5.5 Mt) nickel metal remained undiscovered in demonstrably mineralised komatiite bodies within the Kalgoorlie Terrane. More emphasis is placed on endowment density which may be more intrinsic to the Kalgoorlie Terrane than deposit density because deposit counts are confounded by definitional ambiguities emanating from orebody complexities. Thus the spatial pattern of mineral deposits may not coincide with the spatial pattern of mineral endowment as demonstrated by spatial centrographic analyses in this study.To estimate the amount of undiscovered nickel metal in the entire Kalgoorlie Terrane and not just in the demonstrably mineralised komatiite bodies, Zipf’s law was applied. According to Zipf’s law, the size of the largest deposit is twice the size of the second, thrice the size of the third, four times the fourth, and so on. Based on the currently known size of Mt. Keith deposit, the largest nickel sulphide deposit in the Kalgoorlie Terrane, Zipf’s law indicates that the terrane is nearly mature in terms of nickel exploration and contains only about 3.0 Mt nickel metal in undiscovered resources. The collective implication of the regression and Zipf’s law estimates is that in the Kalgoorlie Terrane, no significant nickel resources are likely to be contained in the known komatiites that are presently not demonstrably mineralised. However if, as widely speculated, the actual size of Mt. Keith deposit is about twice the currently known size, Zipf’s law predicts 10.0 Mt nickel metal in undiscovered nickel endowment for the Kalgoorlie Terrane. The additional 7.0 Mt undiscovered nickel metal endowment is attributed to opening up of a new exploration search space through deeper resource delineation, within an otherwise nearly mature terrane.

Gli stili APA, Harvard, Vancouver, ISO e altri

45

Stalder, Marcel. "Petrology and mineral chemistry of sulphide ores and associated metalliferous rocks of the Gamsberg Zn-Pb deposit, South Africa : implications for ore genesis and mineral exploration". Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16072.

Testo completo

Abstract (sommario):

Thesis (PhD)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: The Gamsberg Zn-Pb deposit is a metamorphosed and multiply deformed sediment-hosted base metal deposit in the central Namaqua Province of South Africa. The deposit is hosted by the Bushmanland Group, a late Palaeoproterozoic (2000-1600 Ma) supracrustal succession of quartzite, metapelitic schist and interbedded metavolcanic rocks. Mineralisation occurs within the central part of the Gams Formation, a heterogeneous sequence of metamorphosed metalliferous sediments and fine-grained organic-rich shales. The ore horizon is subdivided into a lower unit of metapelite-hosted ore, an intermediate layer of phosphorite-hosted ore, and an upper unit of banded garnet-apatite ore. The ore body is enveloped by unmineralised silicate-, carbonate- and oxide-facies metalliferous rocks, which originally represented mixtures of Fe-Mn-rich hydrothermal precipitates, authigenic carbonate, and variable concentrations of detrital material. Based on mineralogical and geochemical characteristics, the metalliferous host rocks are subdivided into iron formations, coticules, Fe-Mn silicates, impure marbles and barite/Ba-rich quartzite. Minerals of the Gams Formation mostly represent solid solution between the Fe and Mn end-members of garnet, pyroxene, pyroxenoid, amphibole, olivine, spinel and ilmenite. Calcium-rich rock types are a typical feature and characterized by the occurrence of manganoan calcite, clinopyroxene, andradite-rich garnet and titanite. A successive increase in the (Mn+Ca):Fe value of rocks and minerals is evident with increasing distance from the ore horizon. Amphibole is restricted to Fe-rich ore-bearing assemblages, whereas orthopyroxene, clinopyroxene, Fe-rich pyroxenoid and olivine are present in intermediate assemblages, and Mn-rich rhodonite and pyroxmangite in the most manganiferous assemblages. These variations are mimicked by an increase in the Mn:Fe value of coexisting garnet and ilmenite group minerals with increasing distance from ore. LA-ICP-MS analyses have been used to constrain the REE patterns of garnet and apatite. In the ore-body, these minerals display a positive Eu anomaly, which is interpreted to reflect a distinct hydrothermal signature. In contrast, garnet and apatite in unmineralised metalliferous rocks display nil or a negative Eu anomaly. Primary features of the Gams Formation, such as REE patterns, the banded nature of garnet-apatite ore, the presence of diagenetic apatite nodules, and the distribution of the redox-sensitive elements Ba and Mn have been used to constrain palaeo-environmental conditions. The results indicate that metapelitehosted ore has been deposited in a stratified ocean that was characterised by anoxic bottom waters and precipitation of Fe and Zn sulphides into organic matter-rich shales. These rocks were superceded by phosphorite-hosted ore, garnet-apatite ore and metalliferous host rocks that developed in a suboxic to oxic environment. The large size of the deposit, the internal lamination of the ores and the predominance of sphalerite and barite are consistent with a vent-distal setting and precipitation of the ore-forming constituents from dense and reduced hydrothermal fluids, which originated due to reactivation of dormant growth faults. Collectively, the geological evidence indicates that Gamsberg is bridging the gap betweenthe SEDEX and BHT classifications. The relationships demonstrate that differences between these two classes of sediment-hosted Zn-Pb deposits are predominantly related to environmental conditions within localised third order basins and not to fundamental differences in ore-forming processes.
AFRIKAANSE OPSOMMING: Die Gamsberg Zn-Pb afsetting is ‘n meerfasig vervormde en gemetamorfiseerde sedimentgesetelde onedel metaal afsetting in die sentrale Namakwa Provinsie van Suid Afrika. Die afsetting word geherberg deur die Boesmanland Groep, ‘n laat Paleoproterosoïse (2000 – 1600 Ma) bokors-opeenvolging van kwartsiet, metapelitiese skis en tussengelaagde metavulkaniese gesteente. Mineralisasie word gevind in the sentrale deel van die Gams Formasie. Die Gams Formasie is ‘n heterogene opeenvolging van gemetamorfiseerde metaalhoudende sediment en fynkorrelrige organiese skalie. Die erts horison word onderverdeel in ‘n onderste laag van metapeliet-gesetelde erts, n sentrale laag van fosforiet-gesetelde erts, en ‘n boonste laag van gebande granaat-apatiet erts. Die erts-liggaam word omhuls deur ongemineraliseerde silikaat-, karbonaat- en oksied-fasies metal-ryke rotse. Hierdie gesteentes word geinterpreteer as oorspronklike mengsels van Fe-Mn-ryke hidrotermale partikels, outigeniese karbonaat, en verskeie hoeveelhede detritale materiaal. Gebaseer op mineralogiese en geochemiese kenmerke word hierdie rotse onderverdeel in ysterformasies, „coticules“, Fe-Mn silikate, onsuiwer marmer en barite/Ba-ryke kwartsiet. Minerale van die Gams Formasie form meestal soliede oplossingsreekse tussen die Fe en Mn endlede van granaat, pirokseen, piroksenoid, amfibool, olivien, spinel en ilmeniet. Kalsium-ryke rots tipes is ‘n tipiese kenmerk van die Gams Formasie en word gekenmerk deur mangaan-ryke kalsiet, klinopirokseen, andradiet-ryke granaat en sfeen. Daar word ‘n stapsgewyse vergroting van die (Mn+Ca):Fe verhouding in gesteentes en minerale gevind met toeneemende afstand van die erts horison. Amfibool is beperk tot Fe-ryke ertsdraende gesteentes, ortopirokseen, klinopirokseen, Fe-ryke piroksenoid en olivien tot intermediêre gesteentes, en Mn-ryke rodoniet en piroksmangiet tot Mn-ryke gesteentes. Hierdie variasies gaan gepaard met vergroting van die Mn:Fe verhouding in granaat en ilmeniet-groep minerale met toeneemende afstand van die erts. LA-ICP-MS analises was gebruik om die skaars-aarde element patrone van granaat en apatiet te bepaal. In die erts-liggaam wys hierdie minerale ‘n positiewe Eu anomalie, wat geinterpreteerd word as ‘n hidrotermale kenmerk. In ongemineraliseerde gasheer gesteentes wys granaat en apatiet geen of ‘n negatiewe Eu anomalie. Primêre kenmerke van die Gams Formasie, soos skaars-aarde patrone, the gebande voorkoms van granaat-apatiet erts, die teenwoordigheid van diagenetiese apatiet knolle, en die verspreiding van die redox-sensitiewe elemente Ba en Mn, was gebruik om afleidings oor die paleo-omgewing te maak. Die resultate het gewys dat metapeliet-gesetelde erts afgeset was onder anoksiese bodem water deur presipitasie van Fe en Zn sulfiedes in organiese skalie. Hierdie erts gaan oor in fosforiet-gesetelde erts, granaat-apatiet erts en metaal-ryke gasheer gesteente wat in ‘n suboksiese tot oksiese omgewing ontstaan het. Die grootte van die afsetting, die interne gelaagdheid van die erts, asook die teenwoordigheid van sfaleriet en bariet dui op ‘n distale omgewing relatief tot die hidrotermale bron en presipitasie van die ertsuit digte en gereduseerde hidrotermale vloeistowwe, wat ontstaan het deur die heraktiveering van rustende groeiverskuiwings. Gesaamentlik bewys die geologiese kenmerke van Gamsberg dat gemetamorfiseerde SEDEX en Broken Hill-tipe mineralisasie binne die perke van ‘n enkele afsetting kan voorkom. Die geologiese verhoudings dui aan dat verskille tussen hierdie twee tipes van sedimentgesetelde afsettings meestal veroorsaak word deur omgewings-toestande binne in gelokaliseerde derde orde komme en nie deur fundamentele verskille in ertsvormende prosesse nie.

Gli stili APA, Harvard, Vancouver, ISO e altri

46

Greben, Harma. "The biological sulphate removal process". Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52490.

Testo completo

Abstract (sommario):

Thesis (MSc)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: South Africa is one of the world's major coal producers, resulting in the second highest foreign exchange earner for South Africa. However, the mining industry contributes negatively to (ground) water pollution, due to the formation of acid mine drainage (AMD). AMD originates from the bacterial oxidation (Thiobacillus ferrooxidans) of pyrite (FeS) and contains high levels of sulphate and metals. Sulphate rich waters can be treated applying the biological sulphate removal technology. This study concentrated on biologically removing sulphate from synthetic feed- and mine water, using the single-stage completely-mixed reactor system. The advantage of using this reactor system is that except for removing sulphate from about 2000 to less than 200 mg/t', it can also partly biologically remove the formed sulphides. It was established that both ethanol and sugar can be used, as the carbon and energy source, however ethanol is more cost effective than sugar. Ethanol dosage and Hydraulic Retention Time (HRT) studies were undertaken to investigate at what concentration, the highest sulphate and sulphide removal rates were achieved. It was found that the highest sulphate reduction rates were obtained when using 1mf ethanol/f feed and that the removal rates were dependent on the HRT: the lower the HRT, the higher the sulphate reduction rate. The highest sulphide oxidation rate was achieved at the HRT of 6 h. It was, furthermore shown that the single stage completely-mixed reactor system could successfully be used to remove sulphate from Schoongezicht mine effluent, not only removing the sulphate, but also most of the metals, thereby increasing the mine effluent pH from 2.5 to 7. The conclusion of this study was that a completely-mixed reactor system, as described in this thesis, can successfully be applied to treating acid mine drainage using ethanol (1 m.e etanol/f feed water) as the carbon and energy source at a hydraulic retention time as low as 4 hours. This technology has great potential for pilot- and full-scale treatment of sulphate rich effluents such as acid mine drainage.
AFRIKAANSE OPSOMMING: Suid Afrika is een van die vemaamste steenkool produseerders in die wereld, terwyl die uitvoer van steenkool die land se tweede hoogste verdiener is van buitelandse valuta. Ongelukkig dra hierdie industrie ook by tot die besoedeling van (grond) water, veral vanwee die vorrning van suur myn afloop. Bakteriese oksidasie (deur Thiobacillus ferrooxidansy van piried (FeS) is hoofsaaklik verandwoordelik vir die vorrning van suur myn afloop bevattende hoe konsentrasies van sulfaat en metale. . Die toepassing van biologiese sulfaatverwyderingsprosesse vir die behandeling van sulfaatryke waters is vroeer gedemonstreer. Die doel van hierdie studie was om 'n enkel-stadium reaktor met volledige vermenging te evalueer en te optimiseer om toegepas te word vir die biologiese verwydering van sulfaat vanuit sinteties bereide, sowel as mynwater. Hierdie reaktor is in staat om sulfaat te verwyder vanaf vlakke van ~ 2000 tot minder as 200 mg/P. 'n Verdere voordeel gepaard met die gebruik van hierdie reaktor is dat die sulfied wat gevorm word tydens sulfaatreduksie, gedeeltelik verwyder word deur die oksidasie daarvan na So. Die resultate wat behaal is in hierdie studie het aangedui dat beide etanol en suiker gebruik kan word as die koolstof en energiebron, terwyl etanol meer koste-effektief aangewend kon word. In teenstelling was metanol nie 'n geskikte koolstofbron vir sulfaatverwydering nie. Eksperimente is daarvolgens uitgevoer om toestande van optimum etanoldosering en hidroliese retensietyd (HRT) vir maksimum sulfaat- en sulfiedverwydering te bepaaJ. Die hoogste reduksie tempo's was verkry met 'n toediening van 1 mP etanol/f invloei, en die effektiwiteit van verwydering was afhanklik van HRT. Hoe laer die HRT, hoe hoer die tempo van sulfaatverwydering. Die beste sulfaatverwyderingstempo was behaal teen 'n HRT van 6 uur. Die resultate het verder aangetoon dat die enkel-stadium reaktor met volledige vermenging in staat was om sulfaat effektief te verwyder, en die pH te verhoog vanaf na 2.5 tot 7, in mynuitvloeisels van 'n plaaslike steenkoolmyn. Die gevolgtrekking uit hierdie werk is dat 'n volledig-gemengde reaktorstelsel, soos beskryf in die huidige studie, geskik is vir die suksesvolle behandeling van suur mynafloopwater met die gebruik van etanol (l mflP toevoerwater) as koolstof- en energiebron by 'n hidrouliese retensietyd tot so laag as 4 uur. Die tegnologie het groot toepassingspotensiaal vir volskaalse behandeling van sulfaatryke afloopwaters soos by. suur mynafloop.

Gli stili APA, Harvard, Vancouver, ISO e altri

47

Johansson, Simon. "Ore mineralogy and silver distribution at the Rävliden N volcanogenic massive sulphide deposit, Skellefte district, Sweden". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-66264.

Testo completo

Abstract (sommario):

The Rävliden North deposit (Rävliden N) is a volcanogenic massive sulphide (VMS) deposit in the western part of the Skellefte district, northern Sweden. The district is one of Sweden’s major metallogenic provinces with a significant amount of VMS deposits. The Rävliden N deposit, discovered in 2011, contains copper, zinc, lead, silver and subordinate gold and occurs close to the largest VMS deposit in the district, the Kristineberg deposit, which has been mined for more than 70 years. The purpose of this master thesis is to study the composition, mineralogy and paragenetic relationships in different types of sulphide mineralization from the Rävliden N deposit. Emphasis is placed on characterizing the distribution and paragenetic relationships of silver-bearing minerals. The methods include core logging, sampling and mineralogical studies through light optical microscopy (LOM), scanning electron microscopy (SEM) and quantitative evaluation of mineralogy by scanning electron microscopy (QEMSCAN). Lastly, electron microprobe analysis (EMPA) was used to determine the chemical composition of silver-bearing minerals and sulphides. Mineralization types studied include 1: the main massive to semi-massive sulphide mineralization, 2: stratigraphically underlying stringer mineralization and 3: local, vein- and/or fault-hosted silver-rich mineralization in the stratigraphic hanging wall. The massive to semi-massive sulphide mineralization is dominated by sphalerite with lesser galena and pyrrhotite. In contrast, the stringer mineralization is dominated by chalcopyrite and pyrrhotite. The major minerals show evidence of a coeval formation and textural as well as structural evidence suggest that ductile deformation has affected the mineralization types. Notable evidence includes ball-ore textures, accumulation of minerals in pressure shadows and brittle fracturing of competent arsenopyrite and pyrite porphyroblasts and infilling by more incompetent sulphide minerals. The silver-bearing minerals identified are commonly spatially associated with galena and the major species is freibergite ((Ag,Cu,Fe)12(Sb,As)4S13), which also occur as inclusions in chalcopyrite mainly in the stringer mineralization. The stringer mineralization also contains notable amounts of hessite (Ag2Te). Notably, galena, pyrrhotite, freibergite and other sulphosalt minerals are commonly accumulated in pressure shadows near host rock fragments in the massive to semi-massive sulphide mineralization. The only gold-bearing mineral identified in this study is electrum (Au, Ag) in the stringer mineralization. The hanging wall mineralization locally comprises faulted and/or sheared massive sulphide mineralization which is compositionally similar to the main massive to semi-massive sulphide mineralization, besides a significantly higher content of freibergite. However, parts of the hanging wall mineralization are entirely dominated by sulphides and sulphosalts of silver, such as pyrargyrite (Ag3SbS3), pyrostilpnite (Ag3SbS3), argentopyrite (AgFe2S4), sternbergite (AgFe2S3) and stephanite (Ag5SbS4). These occur in structurally late settings, which along with consideration of their temperature stabilities suggest a late origin. Since the silver-bearing minerals in the massive to semi-massive sulphide mineralization and the two varieties of hanging wall mineralization contains the same metals, the mineralization in the hanging wall may have formed by late-stage remobilization of ore components from the underlying Rävliden N deposit. This negates the need for multiple mineralization events to explain the local silver-enriched zones in the hanging wall. The paragenetically late mineralization types contains high content of Ag-bearing minerals in relation to base metal sulphides. This suggests that remobilisation processes were important for locally upgrading the Ag-content.

Gli stili APA, Harvard, Vancouver, ISO e altri

48

Armstrong, John P. "Variations in silicate and sulphide mineral chemistry between free-milling metallic and refractory invisible gold ores, Con Mine, Yellowknife, Northwest Territories". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ28472.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

49

Roman, Henry James. "The degradation of lignocellulose in a biologically-generated sulphidic environment". Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1004057.

Testo completo

Abstract (sommario):

South Africa is renowned for its mining industry. The period over which the polluted waters from the existing and abandoned mines will require treatment has driven research into the development of passive treatment systems. These waters are characterised by a low pH, high concentrations of heavy metals, high levels of sulphate salts and low concentrations of organic material. The biological treatment of these waters has been a subject of increasing focus as an alternative to physicochemical treatment. The utilisation of lignocellulose as a carbon source has been restricted by the amount of reducing equivalents available within the lignocellulose matrix. After a few months of near 100% sulphate reduction, it was found that although there was a large fraction of lignin and cellulose remaining, sulphate reduction was reduced to less than 20%. The present study demonstrated that lignocellulose can be utilised as a carbon source for sulphate reduction. It was established that lignocellulose degradation was enhanced under biosulphidogenic conditions and that lignin could be degraded by a sulphate reducing microbial consortium. It was established using lignin model compounds synthesized in our laboratory, that the bonds within the lignin polymer can be cleaved within the sulphidic environment. The presence of cellulolytic enzymes, using CMCase as a marker enzyme, was detected within the sulphate reducing microbial consortium. Based on the results obtained a descriptive model was formulated for the degradation of lignocellulose under biosulphidogenic conditions. It was determined that the initial reduction in sulphate observed using lignocellulose as a carbon source was due to the easily extractable components. The degradation of which resulted in the production of sulphide, which aided in the degradation of lignin, allowing greater access to cellulose. Once the easily extractable material is exhausted, the cycle is halted, unless the sulphide production can be maintained. This is the focus of an ongoing project, testing the hypothesis that an easy to assimilate carbon source added after exhaustion of the easily extractable material, can maintain the sulphide production.

Gli stili APA, Harvard, Vancouver, ISO e altri

50

Boshoff, Genevieve Ann. "Development of integrated biological processing for the biodesalination of sulphate- and metal-rich wastewaters". Thesis, Rhodes University, 1999. http://hdl.handle.net/10962/d1003958.

Testo completo

Abstract (sommario):

The substantial pollution threat to the South African environment from acid mine drainage (AMD) effluents has been well documented. Due to the juvenile nature of acidity in these flows, any remediation strategies implemented will need to function effectively and at low cost for long periods of time. The widespread use of sulphate reducing biological systems for the treatment of such effluents, and in particular large volume flows, has been limited. The supply of inexpensive electron donor and carbon sources, as well as appropriate reactor designs capable of handling large volume flows, have been identified as among the principal factors limiting development of this technology. The broad aim of the research programme reported here was to undertake an evaluation of the feasibility of an algal-bacterial integrated ponding system for the treatment of AMD, and the waste stabilisation pond (WSP) as an appropriate reactor design for this application. The study attempted to demonstrate the feasibility of individual unit operations in a proposed process train using complex organic carbon serving as the electron donor source for the sulphate reducing bacteria (SRB). Studies were undertaken as laboratory and pilot-scale investigations. Tannery effluent was shown to be a functional carbon source for biological sulphate reduction, with effective removal of sulphate and organics being recorded. In turn, the use of biological sulphate reduction for the treatment of tannery effluent was demonstrated. Algal biomass was shown in laboratory studies to function as an effective carbon source for biological sulphate reduction. It is known that micro-algae produce large quantities of photosynthate which is released to the growth medium under conditions of physiological stress. The potential for the use of photosynthate production in high rate algal ponding systems and its manipulation and use as a sustainable carbon source for sulphate reduction was investigated. Growth of a mixed culture of Dunaliella under conditions of light, temperature and salinity stress demonstrated production of large quantities of organic carbon. However, growth was inhibited at high temperatures. An elevation of salinity levels led to a decrease in growth of Dunaliella, but to increased organic carbon production. Spirulina spp., on the other hand, grew well at higher temperatures but showed the highest organic carbon production, and release to the medium, under low light conditions. These results led to a proposed process for the integration of algal ponding into an integrated system for the treatment of AMD. The algal biomass may be fed into the anaerobic digester as a carbon source, or it may be passed into a High Rate Algal Pond (HRAP) where it is stressed to enhance the organic carbon content. This can then be fed into the anaerobic digester as a carbon source. The impact of high levels of sulphide in the water feeding to the algal growth compartment was investigated. Spirulina spp. isolated from a tannery waste stabilisation pond was shown to be a sulphidophilic strain of cyanobacterium, capable of being adapted to high concentrations of sulphide. Dunaliella salina on the other hand was less tolerant. These results demonstrated the practical use of algal biomass providing an oxygen-rich cap for odour control on the surface of the facultative pond as well for the secondary treatment of sulphide-rich overflow to the High Rate Algal Pond. The ability of micro-algae to elevate the pH of their surrounding environment was evaluated as a functional precipitant and neutralisation reagent for acidic metal containing wastewater. Spirulina spp. was shown to perform effectively. D. salina was less functional in this environment. Anacystis spp. was effective in elevating the pH of a defined medium as well as a zinc-rich effluent. These results indicated the practicality of a neutralising function for algal ponds in the treatment of AMD. Metal removal in the system was found to be a combined function of sulphide precipitation, removal by binding to micro-algal biomass and extracellular polymeric substances. The feasibility of waste stabilisation ponding technology use for the treatment of large volume AMD effluents was provisionally demonstrated. It was shown that complex carbon sources would be used as efficient electron donors for sulphate reduction. The integration of algal ponding into the system provides for the generation of a sustainable carbon source, odour control with the recycling of oxygen-rich water onto the top of the facultative pond, secondary treatment of the anaerobic digester overflow, and the neutralisation of the incoming acidic effluents and removal of heavy metals. Integration of the individual unit operations, the feasibility of which has been provisionally demonstrated in this study, into a continuous process train is being investigated in follow-upstudies.

Gli stili APA, Harvard, Vancouver, ISO e altri

Tesi sul tema "Sulphide minerals"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili