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1
Altass, Hatem. "HCl nanoscience at copper and copper/gold alloy surfaces." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/50823/.
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The reaction of HCl with clean, Cu(100) and (111), and Au/ Cu(100) surfaces was investigated using x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) under ultra high vacuum (UHV) conditions. Exposure of the Cu(100) and (111) samples to HCl at room temperature leads to the formation of a saturated copper chloride monolayer. In the case of Cu(100), the saturated coverage was half monolayer corresponding to a c(2x2)-Cl reconstruction (half monolayer is 7.25x1014 cm-2) while for Cu(111) it was one third monolayer consistent with the reconstruction of (√3x√3)R30o (one third monolayer 5.9x1014 cm-2). The interaction of HCl with preoxidised Cu(100) and (111) showed different behaviour from those of clean copper surface depending on the way of interaction of oxygen with copper surface. Interaction of HCl with peroxidised Cu(111) at saturation oxygen coverage leads to the adsorption of chlorine on top of the copper surface with one third coverage. In contrast, presence of oxygen on Cu(100) surface at saturation coverage or less leads to adsorb chlorine but with an excess in chlorine concentration (more than the expected c(2x2) coverage). Oxidized Cu(100) and (111) surface at elevated temperature leads to the formation multi oxide layer. The two oxide surfaces („‟44‟‟ and „‟29‟‟) observed at the Cu(111) depend on the temperature of the substrate at the time of oxidation. The (√2x2√2)R45o structure was observed on the Cu(100) surface on heating which is the same structure formed at saturation coverage at room temperature. Interaction of HCl with Cu(100) and (111) surfaces covered by multilayers of oxide lead to adsorption of chlorine on top of the copper surface with a coverage more than more than the saturation coverage. Interaction of HCl with Au/Cu(100) showed two different behaviour depending on the gold coverage. Au/Cu(100) alloy formed at half monolayer of gold coverage, forming c(2x2) structure. Exposure of the Au/Cu(100) alloy at half monolayer of gold coverage to HCl leads to the formation of c(2x2)-Cl structure with saturation coverage of half monolayer in similar manner of interaction of HCl with the clean cu(100) surface. Interaction of HCl with Au/Cu(100) surface at gold coverage more than half monolayer leads to a dealloying of the gold from the copper surface and forming the Au(111) surface. Cu-Cl formed underneath the Au(111) surface with excess of chlorine concentration.
2
Zheng, Jialong. "An electrochemical study of the copper-gold-cyanide system with reference to the processing of copper-gold ores." Thesis, Zheng, Jialong (2000) An electrochemical study of the copper-gold-cyanide system with reference to the processing of copper-gold ores. PhD thesis, Murdoch University, 2000. https://researchrepository.murdoch.edu.au/id/eprint/52721/.
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Gold and copper often occur together in ores, an occurrence which creates processing difficulties since cyanide leach solutions are not selective for gold. Copper contamination can result in serious problems throughout the conventional carbon-inpulp process, often making the operation uneconomic.
This thesis describes electrochemical studies of two ways of dealing with copper contamination. One concerns the selective electrodeposition of gold from coppercontaining cyanide solutions; the second concerns the possibility of selectively leaching gold from copper-containing ores using an aerated ammoniacal cyanide solution.
In the electrowinning study, a rotating disc electrode technique was combined with a method of chemical analysis to investigate the codeposition behaviour of copper and gold. In these experiments, the variables were gold concentration, agitation, free cyanide concentration, pH and temperature. The experimental results obtained have provided an improved understanding of the electrolytic codeposition of copper with gold in cyanide solutions. The major factors influencing copper codeposition with gold are the free cyanide concentration, the operating temperature and the pH of the electrowinning solution. By controlling these variables in the electrowinning operation, it is possible to minimise the copper deposition.
Pulsed potential control was employed as an alternative to constant potential electrodeposition as a means of reducing copper codeposition in the gold electrowinning process. It was demonstrated in this work that by simply varying the parameters of the applied pulsed potential waveform, all other operating conditions being the same as for the constant potential case, copper contamination was greatly reduced. This improvement is due to the high instantaneous gold deposition rate during the cathodic potential pulse period and the copper redissolution during the anodic potential pulse period.
A rotating electrochemical quartz crystal microbalance (REQCM) technique was developed in this research work. It was demonstrated that this REQCM technique is capable of measuring the partial current of a metal deposition in the potential region where the hydrogen evolution reaction is involved.. Thus, obtaining information outside the electrochemical window of a solid electrode become possible. The REQCM was used to study the mechanism of copper and gold deposition from cyanide solution.
One of the findings from this work is that when using the chronopotentiometric method to study metal dissolution or cementation reactions, the effect of the inert substrate must be taken into account. It was found that the substrate has no influence on the rate if the reaction is diffusion controlled; however, it markedly affects the rate of chemically controlled reactions. The magnitude of the effect is related to the catalytic activity of the substrate.
The REQCM technique was also used to study the mechanism of selective leaching of gold from copper contaminated ores using ammoniacal cyanide. Experimental results show that in copper containing cyanide solutions, the copper-cyanide complex species takes part in the gold dissolution reaction. The addition of ammonia to solutions containing copper and cyanide greatly diminishes the rate of gold dissolution. However, when the cyanide to copper ratio is close to 2:1, the rate of gold dissolution increases on addition of ammonia. This may be due to the formation of some goldammonia complex or the involvement of the formation of Cu(II)- cyanide-ammonia complex which can act as an oxidant in the gold leaching process.
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Clark, Graeme Lawrence. "Studies of copper and gold vapour lasers." Thesis, University of St Andrews, 1988. http://hdl.handle.net/10023/13803.
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The work described in this thesis covers various aspects of pulsed copper and gold vapour lasers. The work is divided into four main parts : a computer model of the kinetics of the copper vapour laser discharge; construction and characterization of a copper vapour laser and a gold vapour laser system (to be used for photodynamic cancer treatment); analysis of the thermal processes occurring in the various forms of thermal insulation used in these lasers; and studies of the use of metal walls to confine a discharge plasma. The results of this work were combined in the design of the first copper vapour laser to use metal rather than an electrically insulating ceramic material for confinement of the discharge plasma. Laser action in copper vapour has been achieved in a number of metal-walled designs, with continuous lengths of metal ranging from 30 mm, in a segmented design, to 400 mm, where the discharge plasma was confined by two molybdenum tubes of this length. A theoretical explanation of the behaviour of plasmas in metal-walled discharge vessels is described.
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Breuer, Paul 1968. "Gold leaching in thiosulfate solutions containing copper(II) and ammonia." Monash University, Dept. of Chemical Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/7762.
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Kydd, Richard Berwick Chemical Sciences & Engineering Faculty of Engineering UNSW. "Synthesis and characterisation of gold and copper oxidation catalysts." Awarded by:University of New South Wales. Chemical Sciences & Engineering, 2009. http://handle.unsw.edu.au/1959.4/44549.
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In this work, Gold and Copper oxidation catalysts supported on a range of metal oxides were synthesised via 2 previously uninvestigated preparation methods. In the first chapter, Gold nanoparticle catalysts were deposited onto TiO2, CeO2 and ZrO2 nanoparticles via the non-aqueous Modified Photodeposition procedure. This method was found to produce smaller Gold particle sizes following intrinsic excitation of the support than the conventional aqueous phase method, with surface physisorbed water apparently acting as the sacrificial reductant. The as prepared catalysts were drastically more active than those prepared by the conventional method and under standardised tests were directly comparable to those prepared by the Deposition Precipitation Method. The second part of the work, explored the preparation of metal oxide supported Copper catalysts via the Flame Spray Pyrolysis process. CO Oxidation tests established the following order of activity for 4wt% Cu loaded on the various supports: Cu-CeO2 > Cu-TiO2 > Cu-ZrO2 > Cu-Al2O3 > Cu-SiO2. CO-TPD studies found that more active materials tended to adsorbed more CO and reacted higher proportions of this with lattice oxygen to form CO2 at lower temperatures. The addition of Cu to each metal oxide surface was found to induce lengthening of the average Metal-Oxygen bond length, with higher electron density on surface O. This phenomenum is proposed as being responsible for the widely reported ???synergistic effect??? reported for similar Cu catalysts. Cu-CeO2 (0-12wt%) catalysts were tested in the Preferential CO Oxidation (COPROX) reaction. Increasing Cu content, varied the Cu morphology from monomers, through to dimers and ultimately CuO crystallites. DFT simulations of the Cu dimer structure revealed higher levels of bonding ionicity in this morphology, relative to the monomeric structure. This coincided with higher levels of activity, reinforcing the earlier finding that highly ionic bonds are conducive to higher levels of activity. High levels of activity and selectivity were maintained until approximately 423 K. Surface redox properties of the 4wt% Cu-CeO2 catalyst were assessed using temperature-programmed reduction (CO, H2) and desorption (CO) experiments, as well as in situ and phase-resolved infrared spectroscopy to study the transition to nonselective conditions. For the first time, it was demonstrated that CO and H2 react at identical surface sites, with CO2 formation proceeding simultaneously via three distinct Cux+-CO carbonyl species. Under non-selective conditions, a gradual red-shift and loss of intensity in the carbonyl peak was observed, indicating reduction of Cu+ to Cu0 and the onset of an alternate non-selective redox-type oxidation mechanism. These results for Cu-CeO2 suggest that improved low temperature catalytic activity will only be achieved at the expense of reduced high temperature selectivity and vice versa. The final section of work explored the use of Cu-based catalysts for the low temperature oxidation of Acetaldehyde (ACA). Based on this work, it is concluded that the ACA oxidation activity of these materials is determined by two main factors: the basicity of the metal oxide support (and its subsequent ability to convert ACA to carboxylates) and the availability of surface oxygen during acetate decomposition. It is proposed that a high concentration of reducible sites (either by Cu addition or naturally occurring on CeO2) accelerates the activation and provision of oxygen and also potentially provides sites for the stabilization of methoxy intermediates resulting from the acetate decomposition.
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Dawson, Susan Elizabeth 1963. "The Occurrence of gold at the Bajo de le Alumbrera Porphyry copper-gold deposit, Northwestern Argentina." Thesis, The University of Arizona, 1994. http://hdl.handle.net/10150/558233.
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Mohammadzadeh, Saeideh. "Electronic Transport Properties of Copper and Gold at Atomic Scale." Doctoral thesis, Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-63427.
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The factors governing electronic transport properties of copper and gold atomic-size contacts are theoretically examined in the present work. A two-terminal conductor using crystalline electrodes is adopted. The non-equilibrium Green’s function combined with the density functional tight-binding method is employed via gDFTB simulation tool to calculate the transport at both equilibrium and non-equilibrium conditions. The crystalline orientation, length, and arrangement of electrodes have very weak influence on the electronic characteristics of the considered atomic wires. The wire width is found to be the most effective geometric aspect determining the number of conduction channels. The obtained conductance oscillation and linear current-voltage curves are interpreted. To analyze the conduction mechanism in detail, the transmission channels and their decomposition to the atomic orbitals are calculated in copper and gold single point contacts. The presented results offer a possible explanation for the relation between conduction and geometric structure. Furthermore, the results are in good agreement with available experimental and theoretical studiesIn der vorliegenden Arbeit werden die wesentlichen Faktoren, die die elektronischen Transporteigenschaften von Kontaktstrukturen atomarer Größe aus Kupfer bzw. Gold bestimmen, theoretisch untersucht. Untersuchungsgegenstand ist eine leitfähige Struktur zwischen zwei kristallinen Elektroden. Um Transportberechungen sowohl unter Gleichgewichts- als auch unter Nicht-Gleichgewichts-Bedingungen durchführen zu können, wird die Simulations-Software gDFTB, die auf dem Nicht-Gleichgewichts-Green-funktionenformalismus in Kombination mit der Dichtefunktional-Tight-Binding-Methode beruht, eingesetzt. Die elektronischen Eigenschaften der betrachteten atomaren Drähte werden nur sehr schwach von ihrer kristallinen Orientierung, ihrer Länge und der Elektrodenanordnung beeinflusst. Als effektivster geometrischer Faktor wurde der Leiterquerschnitt gefunden, weil dieser die Anzahl der Leitungskanäle bestimmt. Darüber hinaus werden die erhaltenen Leitfähigkeitsoszillationen und die linearen Strom-Spannungs-Kennlinien erklärt. Für eine detaillierte Analyse des Leitungsmechanismus werden bei den Ein-Atom-Kontakten aus Kupfer und Gold die Übertragungskanäle und ihre Aufspaltung in Atomorbitale betrachtet. Die präsentierten Ergebnisse bieten eine mögliche Erklärung für den Zusammenhang zwischen Leitfähigkeit und geometrischer Struktur. Die Resultate zeigen eine akzeptable Übereinstimmung mit den verfügbaren experimentellen und theoretischen Studien
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Ruggiero, Carmine. "Adsorption on copper and gold high index single crystal surfaces." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360756.
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Li, Maoshuai. "Development of gold and copper catalysts for sustainable chemical processing." Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3129.
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Supported Au and Cu catalysts have been developed for clean/sustainable production of value fine chemicals (including alcohols, ketone, amines and imines) from selective reduction (of benzaldehyde, nitrobenzene and furfural) and coupled (dehydrogenation-hydrogenation) reaction in the continuous gas phase operation. Critical catalyst physicochemical properties are characterised by applying a range of techniques and correlated to the catalytic response. The role of support, Au particle size and electronic character in determining catalytic activity and selectivity in the hydrogenation of benzaldehyde and nitrobenzene over oxide supported nano-scale (2-8 nm) Au has been established. Hydrogenation (turnover frequency) TOF increases with decreasing Au size (from 8 to 4 nm) with measurably lower TOF over Au < 3 nm. Repulsion of –C=O and –NO2 functionalities with respect to Auδ+ and strong binding to surface oxygen vacancies have been found to lower hydrogenation rates. Promotional effect of water via catalytic dissociation has been found to enhance the selective benzaldehyde hydrogenation rate. Two catalytic routes for imine (N-benzylideneimine) synthesis in continuous gas phase operation have been established. Reductive coupling of benzaldehyde with nitrobenzene (using external hydrogen) over supported Au generated up to 99% selectivity to the target imine. Coupling of benzyl alcohol dehydrogenation with nitrobenzene hydrogenation (in the absence of external hydrogen supply) over Au/TiO2 + Cu/SiO2 mixture produced imine with full hydrogen utilisation. Incorporation of Au/TiO2 to Cu/SiO2 created a synergy between Cu and Au and enhanced catalyst stability. A tandem dehydrogenation/amination/reduction process has been developed for high throughout production of benzylamine in continuous gas phase operation over Cu/SiO2 and Au/TiO2. A synergy between Cu/SiO2 and Au/TiO2 serves to promote benzylamine formation with 81% yield achieved through an optimization of process parameters. Coupling of 2-butanol dehydrogenation with nitrobenzene hydrogenation over Cu/SiO2 in the absence of an external H2 supply delivered exclusive production of both 2-butanone and aniline at full conversion. Hydrogen utilisation efficiency was appreciably greater (by a factor of up to 50) in the coupled system relative to conventional stand-alone hydrogenation using pressurised hydrogen. Selective conversion of biomass-derived furfural to furfuryl alcohol over supported Au catalysts has been established. A series of approaches (e.g. promotional effect of water via catalytic dissociation, increased spillover hydrogen with addition of oxide support and coupling strategy) directed at increasing the surface availability of reactive hydrogen were adopted to enhance furfuryl alcohol production and hydrogen utilisation. Continuous production of γ-butyrolactone has been established in both stand-alone hydrogenation of succinic acid (using external H2) and reaction coupling with formic acid decomposition (as a source of H2) over Cu/SiO2. Pd/SiO2 and Ni/SiO2 promoted propanoic acid formation at higher reaction rates. The results presented in this thesis establish feasible catalytic routes to high value alcohols, imines and amines where critical process optimisation is demonstrated in terms of catalyst composition/surface structure and reaction conditions.
10
Davis, Harrison Olivia. "Copper, Silver, and Gold Clusters: A Synthetic and Structural Investigation." Kent State University Honors College / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1557352298361181.
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Gendall, Ian Richard. "The porphyry copper system and the precious metal-gold potential." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1005604.
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It has been established that porphyry copper/copper-gold deposits have formed from I Ma to 2 Ga ago. Generally, they are related to the Mesozoic-Cenozoic interval with few reported occurrences from the Palaeozoic or Precambrian. A reason cited is the erosion of these deposits which are often related to convergent plate margins and orogenic belts. Observations of the alteration and mineralisation within and around porphyry copper/copper-gold systems have been included in numerous idealised models. These alteration and mineralisation patterns are dependent on the phases of intrusion, the tectonic setting and rock type, depth of emplacement and relationship to coeval volcanics, physiochemical conditions operative within and surrounding the intrusive and many other mechanical and geochemical conditions. Island arc and cratonic arc/margin deposits are generally considered to be richer in gold than their molybdenum-rich, intra-cratonic counterparts. Metal zonation may occur around these copper/copper-gold deposits, e.g. copper in the core moving out to silver, lead, zinc and gold. This zonation is not always present and gold may occur in the core, intermediate or distal zones. Examples of gold-rich porphyry deposits from British Columbia, Chile and the SW Pacific Island regions suggest gold is closely associated with the potassic-rich zones. Generally these gold-rich zones have greater than 2% magnetite and a high oxygen fugacity is considered to be an important control for gold deposition. High Cl contents within the magma are necessary for gold mobility within the host intrusive centres. Beyond this zone HS₂ becomes an important transporting ligand. Exploration for porphyry copper-gold deposits includes an integrated geological, geophysical and geochemical approach. Petrographic work through to Landsat imagery may be used to determine the chemical conditions of the system, ore association, favourable structural zones and alteration patterns, in order to focus exploration activities.
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Boreux, Arnaud. "Development of new dual catalysis systems with gold and copper." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX053/document.
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Depuis plusieurs décennies, la catalyse par les métaux de transition est devenue un outil incontournable pour la synthèse organique. Chaque année, des milliers de publications décrivent le développement de nouvelles réactions effectuées en présence de complexes organométalliques. Le premier chapitre de ce manuscrit présente une comparaison générale de la réactivité des métaux du groupe 11 (Cu, Ag, Au), avec une attention particulière sur leur capacité à réaliser des réactions d’activation électrophile (Au) ou des transferts de nucléophiles (Cu). Des exemples représentatifs sont donnés pour illustrer ces concepts. Dans la seconde partie, la synthèse d’allènes et d’énones trifluorométhylés par catalyse à l’or(I) est détaillée. Une méthode générale de préparation d’allènes-CF3 a été développée par un transfert d’hydrure-1,5 induit par un complexe d’or(I). Les limites de la méthode ainsi que certaines applications des produits sont décrites. Dans la même idée, un réarrangement-[3,3] d’acétates propargylique catalysé par l’or(I) a été appliqué à la synthèse d’énones-CF3. L’incorporation de cette méthode dans un processus monotope avec une réaction de Diels-Alder est également présentée. La troisième partie est centrée sur les réactions de borofonctionnalisation d’allènes catalysées par le cuivre(I). Les récents développements de ce domaine sont passés en revue, et notre contribution à ce sujet est détaillée. Enfin, un travail préliminaire sur l’élaboration d’un processus monotope impliquant une catalyse coopérative cuivre(I)/or(I) est présentéDuring the last decades, transition metal catalysis has become an essential tool in organic synthesis. Each year, thousands of publications report the development of new reactions mediated by metal complexes. This manuscript depicts our contribution to this field. The first chapter presents a general comparison of the reactivity of coinage metals (Cu, Ag, Au) complexes in catalysis, with a special focus on their ability to perform electrophilic activation (Au) or nucleophilic transfer (Cu) reactions. Representative examples are given to illustrate these concepts. In the second part of the manuscript, the synthesis of trifluoromethylated allenes and enones by gold(I) catalysis is reported. A general method for the preparation of CF3-allenes has been developed based on a gold(I)-mediated 1,5-hydride shift. The scope and limitations of the method, as well as some subsequent transformations of the products are described. Using similar substrates, a gold(I)-catalyzed [3,3]-acetate rearrangement was applied to the preparation of CF3-enones. The employment of this method into a one-pot procedure involving a subsequent Diels-Alder reaction is also reported. The third part focuses on the copper(I)-catalyzed borofunctionalization of allenes. The recent reports from the literature are reviewed, and our contributions to this area of research are described through the study of a new copper(I)-catalyzed allene boroacylation method. Finally, preliminary results on the elaboration of a copper(I)/gold(I) catalytic one-pot process are presented
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李丹 and Dan Li. "Synthesis, structure and photophysical and photochemical properties ofpolynuclear copper (1), silver (1) and gold (1) complexes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31233120.
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Li, Dan. "Synthesis, structure and photophysical and photochemical properties of polynuclear copper (1), silver (1) and gold (1) complexes /." [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13385367.
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Choi, Tae-Seop. "Copper, silver, and gold etching with H₂ and CH₄ based plasmas." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53043.
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This thesis describes investigations on Cu, Ag, and Au subtractive etching by H₂ and CH₄ plasmas below room temperature. Both blanket film of Cu, Ag, and Au etching and patterning studies were performed for the applications of these metals as interconnects in electronic devices and photonic devices to replace current Damascene process. The nm scale Cu patterning in H₂ plasma was demonstrated by etching Ta/Cu/Ta stacks. Also, Ag and Au etching was feasible in H₂ plasma unlike other transition metals such as Ti, Ta, Ni, Cr, Al, and Pt indicating the etching chemistry based on the similar electronic structures of group 11 metals plays important role. In addition, employing CH₄ plasma allowed the use of photoresist mask and patterned Cu, Ag, and Au with high selectivity. The overall etch mechanism is the combination of chemical reactions and physical (photon and ion) bombardment in H₂ and CH₄ plasma. However, the Cu etching mechanism is more dependent on the chemistry while Ag and Au patterning were dominated by physical bombardment. Finally, the direction for future work including further mechanistic study and process optimization is suggested.
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Bejgarn, Therese. "New styles of intrusive related copper-gold deposits in northern Sweden /." Luleå, 2009. http://pure.ltu.se/ws/fbspretrieve/3373051.
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Chan, Chui-ling. "Synthesis and luminescence studies of homo- and heteronuclear complexes of gold and copper /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20567698.
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Zibin, Hai. "Modification of Titania with Gold-Copper Bimetallic Nanoparticles and Preparation of Copper-Based Photocatalysts : Application in Water Treatment." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00926757.
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Photocatalysis is recently extensively studied because it implies a variety of potential industrial applications ranging from the hydrogen generation of water splitting to the treatment of waste water. Among all the semiconductors, TiO2 has attracted the most attention. But the rate of the electron-hole recombinations is very important and TiO2 is active only under UV light. Various methods are developed to enhance the photoactivity of TiO2. Other semiconductors like copper oxides and copper sulfides also attracted attention due to their lower band-gaps which allow applications in solar photocatalysis. In this work, different kinds of photocatalysts were developed and studied: surface modified TiO2 with metal nanoparticles and copper sulfides and oxides. The nanostructures were characterized by different techniques: HRTEM, SEM, XRD, XPS, HAADF-SEM, and TRMC. Their photocatalytic activity was studied for degradation of model pollutants: phenol, rhodamine B and methyl orange. Different chemical and radiolytic methods have been investigated to modify the surface of TiO2 by mono- and bimetallic (Au, Cu and Au-Cu) nanoparticles in the aim to improve its photocatalytic activity. The best results in term of photocatalytic activity have been obtained with reduction of THPC (tetrakis (hydroxymethyl) phosphonium chloride) and with radiolytic reduction after deposition with urea. Titania surface modification with Au, Cu and bimetallic Au-Cu NPs enables the increase of the photocatalytic activity under UV light. We have found that very small amounts of metal (0.5% wt.) can activate titania for photocatalytic applications, thus the costs of photocatalyst preparation are relatively low. Radiolytic syntheses of non-TiO2 photocatalysts including Cu2O and CuS nanostructures with different morphologies have been developed. The photocatalytic activity of the synthesized photocatalysts has been studied. Truncated octahedral Cu2O exhibit an excellent photocatalytic activity under visible illumination. CuS nanotubes (NTs) exhibit both a high ability to adsorb dyes and a photocatalytic activity under visible light.
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Lee, Wai-kit. "Syntheses, photophysics and photochemistry of polynuclear d10 complexes of copper(I) and gold(I) /." Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17665589.
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Carles, Patricia 1975. "Constraints on the genesis of the Archaean Troilus gold-copper deposit, Quebec." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31204.
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The Troilus gold-copper deposit lies within the northeastern part of the Archaean Frotet-Evans greenstone belt, in the Opatica sub-province of the Superior Province, northern Quebec, and contains total reserves of 51 Mt at 1.08 g/t gold, 0.11% copper, and 1.4 g/t silver. The largest orebody, Zone 87, has been mined by open pit methods since 1993.Rocks of the Troilus domain include a coarse- to medium-grained metadiorite, a finer-grained amphibolite, a rock with a brecciated texture and felsic dykes, which crosscut the metadioritic pluton, the amphibolite and the breccia. The amphibolite, breccia, and felsic dykes all locally host ore.
Previous researchers have proposed a porphyry-type model for the genesis of the Troilus deposit. However, evidence that the breccia unit is not hydrothermal but a product of magma mixing, that the felsic dykes predate mineralization, and that mineralization and associated alteration occurred as two discrete events separated by a major episode of regional metamorphism (amphibolite facies), requires that alternative genetic models for the deposit be considered, such as orogenic gold model. (Abstract shortened by UMI.)
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Xu, Yi-Jun. "Selective oxidation of hydrocarbons using supported gold, silver, copper and bimetallic catalysts." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/54322/.
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Supported gold catalysts can provide tuneable activity for liquid phase selective oxidation of alkenes, in particular cyclohexene and cis-cyclooctene, using molecular oxygen from air under mild conditions. Selective oxidation can be readily kick-started using a nano-crystalline gold catalyst supported on carbon along with a small amount of TBHP as initiator. Extremely high selectivity, ca. 98%, for partial oxidation products with significant conversion has been obtained using a bismuth-modified gold catalyst for selective oxidation of cyclohexene. In the case of cis-cyclooctene oxidation, high selectivity to partial oxidation products has also been achieved at a high rate of reaction, without the use of solvent, which is a major tenet of green chemistry. Gold catalysts are also active for the selective oxidation of cyclohexane to cyclohexanol and cyclohexanone. The gas-phase epoxidation of propene to propene epoxide (PO) has been studied using only molecular oxygen as oxidant over a series of supported Ag, Cu, Au and bimetallic (Au-Cu, Cu-Ag and Au-Ag) catalysts. It has been found that the support has an important effect on the catalyst performance. A Au-Cu catalyst exhibited very high selectivity to PO, ca. 96%, at a propene conversion, ca. 0.14%, at relatively low temperature, 200 C. The intrinsic instability of PO leads to the observation of high selectivity to PO only at low temperature.
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Coventry, David N. "Tertiary-phosphine gold(I) and copper(I) complexes : precursors for metal deposition." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/12017.
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Tertiary-phosphine stabilised gold and copper complexes have been prepared with the intention to deposit elemental metal from solution. These complexes were intended to be delivered as a component of an ink on to a suitable substrate by an ink-jet printing process. Testing the compatibility of these complexes with ink-jet technology has been undertaken by Avecia and Seiko-Epson (this project's industrial sponsors). Four methyl(tertiary-phosphine)gold(I) complexes with a general molecular formula, [R3PAuCH3] (R = Ph, Ph-p-F, Ph-p-OMe and Me) were prepared by reacting (tertiary-phosphine)gold(I) chloride with methyllithium. Toluene-d8 and decalin solutions of these complexes were heated to 100°C and the rate of decomposition of each complex to gold(O), tertiary-phosphine and ethane was measured spectroscopically by NMR and GC respectively. Relatively the gold(I) complexes were found to decompose in the following order: Ph-p-F > Ph > Me >> Ph-p-OMe A series of tertiary-phosphine stabilised copper(I) aryloxide complexes, with the general molecular formula [{(RO)Cu(PR'3)m}n], were synthesised with the intent to duplicate the results obtained for the gold(I) complexes with a copper system. All the copper(I) complexes prepared were found to be too thermally stable to be suitable for the aim of the project. During the course of this project it was noted that the steric and electronic factors involved in producing the thermodynamic product from the reaction mixture were of major importance in the design of such complexes. Increase in overall steric bulk was, as expected, found to lead to copper(I) ions with lower coordination numbers while an increase in the electron affinity of the ligands was found to produce complexes with copper ions with higher coordination numbers.
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Isildar, Arda. "Biological versus chemical leaching of electronic waste for copper and gold recovery." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1125/document.
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Le bien-être de notre société dépend directement de plusieurs métaux tels que les métaux communs, les métaux précieux et, de plus en plus, les terres rares (TR). L’utilisation de ces métaux s’est développée dans de nombreuses applications, notamment pour les équipements électriques et électroniques (EEE), et leur approvisionnement interrompu est un enjeu majeur. Les appareils électroniques modernes contiennent jusqu’à 60 métaux différents. Il y a un intérêt grandissant pour les sources secondaires de ces métaux, en particulier les déchets d’équipements électriques et électroniques (DEEE), afin de compenser des potentiels manques d’approvisionnement. Cette thèse de doctorat montre les avantages et les inconvénients des approches biologiques et chimiques, ainsi que des avancées et perspectives dans le développement de procédés viables for la récupération des métaux des DEEE. Un nouveau procédé for la récupération des métaux des DEEE est décrit et une évaluation économique est fournie. Les cartes de circuits imprimés (CCI) des ordinateurs de bureau, des ordinateurs portables, des téléphones mobiles et des serveurs de télécommunications ont été étudiées. Les CCI jetées contenaient des concentration en métaux dans la gamme (% du poids) cuivre (Cu) 17,6 - 39,0 / fer (Fe) 0,7 - 7,5 / aluminium (Al) 1,0 - 5,5 / nickel (Ni) 0,2 - 1,1 / zinc (Zn) 0,3 - 1,2 , ainsi que de l’or (Au) (en ppm) 21 - 320. Une analyse multicritère (AMC) utilisant la méthodologie du processus d’analyse hiérarchique (PAH) a été appliquée pour la sélection de la technologie de récupération des métaux la plus adaptée. Une preuve du concept d’extraction par une double étape de biolixiviation est fournie, dans laquelle 98,4% et 44,0% de cuivre et d’or, respectivement, ont été extrait. Cette procédure d’extraction à deux étapes a aussi été appliquée pour la lixiviation chimique des métaux des CCI. La lixiviation du Cu a été effectuée dans un mélange acide d’H2SO4 et d’H2O2, alors que l’Au a été extrait par du S2O32− dans un milieu NH4+, catalysé par CuSO4. Avec les conditions opératoires optimales, 99,2% et 92,2% de Cu et d’Au, respectivement, ont été extrait de ces matériaux. La récupération sélective du Cu du lixiviat de biolixiviation a été étudiée en utilisant la précipitation sulfurée et l’extraction électrolytique (electrowinning). Le Cu a été récupéré de manière sélective en 50 min sur la cathode à une densité de courant de 50 mA, avec une efficacité de 97,8% et une purité de 65,0%. L’analyse technico-économique et l’évaluation de la viabilité environnementale de la nouvelle technologie à un stade précoce de développement ont été étudiéesThe well-being of the society depends on a number of metals, including base metals, precious metals and increasingly rare earth elements (REE). The usage of these metals increased in numerous applications, including electrical and electronic equipment (EEE), and their interrupted supply is at stake. There is an increasing interest in the secondary sources of these metals, particularly waste electrical and electronic equipment (WEEE) in order to compensate their potential supply deficit. This PhD thesis demonstrates the advantages and bottlenecks of biological and chemical approaches, as well as the advances and perspectives in the development of sustainable processes for metal recovery from WEEE. Furthermore, a novel process for the recovery of metals from WEEE is described, and a techno-economic assessment is given. Discarded printed circuit boards (PCB) from personal computers (PC), laptops, mobile phones and telecom servers were studied. Following an extensive literature review, a novel characterization and total metal assay method is introduced and applied to waste board materials. Discarded PCB contained metals in the range of (%, by weight): copper (Cu) 17.6 - 39.0, iron (Fe) 0.7 - 7.5, aluminum (Al) 1.0 - 5.5, nickel (Ni) 0.2 - 1.1, zinc (Zn) 0.3 - 1.2, as well as gold (Au) (in ppm) 21 - 320. In addition, multi-criteria analysis (MCA) using the analytical hierarchical process (AHP) methodology is applied for selection of the best-suited technology. A proof-of-concept for a two-step bioleaching extraction was given, in which 98.4% and 44.0% of the Cu and Au, respectively, were extracted. The two-step extraction concept was applied to the chemical leaching of metals from PCB. Cu leaching was carried in an acidic oxidative mixture of H2SO4 and H2O2, whereas Au leaching for carried out by S_2 O_3^(2-) in a NH_4^+ medium, catalyzed by CuSO4. Under the optimized parameters, 99.2% and 96.6% of Cu and Au, respectively, were extracted from the board material. Selective recovery of Cu from the bioleaching leachate using sulfidic precipitation and electrowinning was studied. Cu was selectively recovered on the cathode electrode at a 50 mA current density in 50 minutes, with a 97.8% efficiency and 65.0% purity. The techno-economic analysis and environmental sustainability assessment of the new technology at an early stage of development was investigated
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Lee, Jaeheon. "Gold cementation on copper in thiosulfate solution: Kinetic, electrochemical, and morphological studies." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280482.
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Cyanidation has been used for more than a century for precious metal recovery and it is still in use today. Cyanide is a very toxic chemical and if not used appropriately will cause environmental problems. There is considerable attention devoted to the development of non-cyanide lixiviants for the process of gold and silver ores. Thiosulfate solution is one of the proposed alternatives to cyanide and gold cementation by copper has been suggested as a promising method for gold recovery from leaching solution. Copper powder and rotating disc electrode were used for the kinetic study. The rate of gold cementation on copper disc is proportional to the initial gold concentration and disc rotating speed. The cementation reaction exhibited two distinct kinetic regions, an initial slow rate followed by an enhanced rate. The activation energy of the reaction was 5.9 kJ/mol at low copper concentration and the reaction is mass transport controlled. With 30 ppm initial copper concentration, there was noticeable decrease in the reaction rate in high temperature range. EDS, XRD, and XPS analysis revealed that the deposits are a Au-Cu alloy instead of pure gold. The alloy composition ranged from Au₃Cu to AuCu₃ depending on the initial Cu/Au mole ratio in solution and applied potential. Electrochemical studies were performed using rotating disc electrode and electrochemical quartz crystal nanobalance. Evans' diagrams were constructed under various experimental conditions. Corrosion current increased with increasing gold concentration, disc rotating speed, as well as thiosulfate concentration. These results confirmed those obtained in the kinetic study. Corrosion potential measurements indicated that passivation onset time was changed by gold concentration, copper concentration and disc rotating speed. Gold(I)-thiosulfate reduction was found to occur at approximately -250 mV vs. SHE using EQCN. Copper adions on the gold surface contributed to the underpotential deposition of copper and the underpotential deposition is the mechanism of alloy formation in cementation system. (Abstract shortened by UMI.)
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Lonca, Geoffroy. "Development of new reactions of organic synthesis catalyzed by gold and copper." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX057/document.
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Cette thèse décrit le développement de nouvelles méthodes de catalyse à l’or et au cuivre pour la synthèse de composés hétérocycliques et de produits trifluorométhylés.Dans un premier temps, une synthèse d’allènes trifluorométhylés par catalyse à l’or a été développée, dont l’étape clé est un transfert d’hydrure 1,5. Cette méthode donne accès de manière efficace et sélective à une large gamme d’allène perfluoroalkylés dont le potentiel synthétique a également été démontré.Le pouvoir catalytique de l’or a alors été utilisé dans une synthèse de 2H-1,3-oxazines reposant sur une cyclisation de type 6-endo d’azido alcynes. Cette méthode donne accès dans des conditions très douces à une gamme sans précédent d’oxazines polysubstituées avec d’excellents rendements.Dans un dernier temps, une méthode d’hydrofonctionnalisation radicalaire d’alcènols catalysée au cuivre. La stratégie impliquée repose sur une abstraction d’hydrogène 1,5, dans laquelle un groupement benzyloxy joue le rôle de donneur d’hydrogèneThis manuscript presents the development of gold- and copper-catalyzed methods for the synthesis of heterocyclic compounds and trifluoromethylated products.Firstly, a gold-catalyzed synthesis of trifluoromethyl allenes was developed, relying on a 1,5 hydride shift. This method allows to access, in a very efficient and selective way, a large range of perfluoroalkylated allenes, of which the synthetic potential was also demonstrated.Afterwards, the catalytic power of gold was then used in a synthesis of 2H-1,3-oxazines, relying on a 6-endo type cyclization of azide-yne substrates. This methods allows to access, in very mild condition, an unprecedently large range of polysubstituted oxazines in excellent yields.Finally, a method for the copper-catalyzed radical hydrofunctionalization of alkenols was developed. The strategy involved relies on a 1,5 hydrogen abstraction, in which a benzyloxy moiety plays the role of the hydrogen donor
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Robinson, Donald A. III. "Synthesis and Characterization of Metal Nanoclusters Stabilized by Dithiolates." Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/chemistry_theses/44.
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Rapidly expanding research in nanotechnology has led to exciting progress in a versatile array of applications from medical diagnostics to photocatalytic fuel cells. Such success is due to the ability of researchers to manipulate the desired properties of nanomaterials by controlling their size, shape, and composition. Among the most thriving areas of nanoparticle research has been the synthesis and characterization of stable metallic nanoclusters capped by thiolate ligands. Our group has extended this research to study copper, silver, and gold clusters with remarkable stability and energetics, which was achieved by using dithiolates as the ligand stabilizers. In addition to the enhanced stability offered by the chelate effect, the use of dithiolate ligands instead of monothiolates is proposed to provide an alternate interfacial bond structure that is shown to strongly influence energetic properties of nanoclusters, with strong evidence of metal-ligand charge transfer. Energetic properties were characterized by spectroscopic and electrochemical methods.
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Wilson, Nicholas Thomas. "The structure and dynamics of noble metal clusters." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368419.
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Murrell-Mottram empirical atomistic many-body and Gupta n-body potentials have been used to study various aspects of the cluster chemistry of copper, silver, gold and nickel. Simulated annealing techniques have been used to search for the global minima of the four metals with up to 55 atoms. Icosahedral, decahedral, octahedral, hexagonal closed packed and hexagonal prismatic structures were found. The gold clusters show some rearrangements and distortions from ideal geometries. Polyhedral cluster calculations up to 1 500 atoms predict that icosahedra and truncated octahedra are particularly stable. Calculations on the structures of copper-gold alloy clusters show that gold atoms prefer to occupy the surface of the cluster. A simple approximation to model the passivation of gold clusters by thiol ligands predicts that for 55 atoms the passivated cuboctahedron is more stable than the icosahedron, the reverse of the order for the bare clusters. Molecular dynamics simulations of gold adatoms on the gold (111) surface and of the impact of a 55 atom gold cluster with the gold (111) surface have been performed.
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Atluri, Vasudeva Prasad 1959. "Recovery of gold and silver from ammoniacal thiosulfate solutions containing copper by resin ion exchange method." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276566.
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This research was undertaken to study the suitable physico-chemical conditions for the selective recovery of gold and silver from simulated thiosulfate leach liquors containing copper, gold or silver, ammonia and thiosulfate using three anion exchange resins. In particular, the effect of chemical variables such as thiosulfate, cupric ion and ammonia concentrations and the solution potential of the system on the batch loading of silver and gold onto the resins have been investigated in detail. Pourbaix diagrams have been constructed to understand the stability of this complex system under various Eh and pH conditions. The experimental results indicate that IRA-400 resin has the highest capacity for both silver and gold compared to IRA-68 and IRA-94. All the three resins investigated are not selective to silver and gold over copper. The elution studies using ammonium thiosulfate solutions have revealed that selective elution of silver from copper is not possible, while some selectivity can be achieved between gold and copper. (Abstract shortened with permission of author.)
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Chan, Chi-keung. "Structure, photophysical and theoretical studies of polynuclear CU(I), AG(I) and AU(I) metal complexes /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18037422.
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Cheung, Kai-leung. "Syntheses and luminescence studies of di- and polynuclear gold(1) and copper(1) complexes, design strategies towards metalloreceptors and mixed-metal complexes /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23736136.
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Ab, Rahim Mohd Hasbi. "Heterogeneous gold, palladium and copper based catalysts for liquid phase oxidation of methane." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/55125/.
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The oxidation of lower alkanes especially methane to methanol under mild reaction conditions is one of the most challenging task for industry and academia. At present, indirect utilisation via synthesis gas is the only commercially viable process for methanol production. Therefore, this study intends to investigate the direct oxidation of methane to methanol using a novel low temperature approach. Recently, gold based supported catalysts have been found to be highly effective oxidation catalysts where a number of important discoveries have been made such as in hydrogen peroxide synthesis and selective oxidation of alcohols to aldehydes. Due to these recent advances, further work into the oxidation of carbon-hydrogen bonds especially methane by gold and gold-palladium alloyed nanoparticles was the central topic of this study. As a proof of concept for the following studies, oxidation of primary C-H bonds in toluene and toluene derivatives were carried out in a high pressure stirred autoclave with molecular oxygen as oxidant. It was evident that Au-Pd supported catalyst is capable in oxidising primary C-H bonds on toluene and toluene derivatives at lower temperature with high catalytic activity based on turnover number (TON) compared to available heterogeneous catalysts reported in literature. However, these catalysts are ineffective in the oxidation of methane with oxygen under mild conditions with water as solvent and temperature below 90 °C. In view of this, hydrogen peroxide has been used as oxidant and it was shown that Au-Pd supported nanoparticles are active for the oxidation of methane giving high selectivity to methanol especially in the reactions carried out with hydrogen peroxide generated using an in-situ approach. Methane oxidation reactions were carried out in aqueous medium. The main products were methanol, methyl hydroperoxide and only carbon dioxide as overoxidation product. Investigations of reaction conditions such as concentration of oxidant, reaction time, reaction temperature and pressure of methane were investigated. It was found that the activity and selectivity of the catalyst was highly dependant on these variables. Oxygenate productivity was found to increase by increasing the H2O 2 or H2/O2 concentration and methane pressure. Longer reaction times were detrimental to the methanol selectivity where overoxidation reaction occurred. Interestingly, the Au-Pd catalytic system was able to oxidise methane to methanol at temperatures as low as 2 °C. The applicability of the developed catalytic system was tested on ethane oxidation reaction and it successfully produced ethanol as the major product. The oxygenate productivity was higher as compared to methane due to the solubility factor and the difference in the strength of carbon-hydrogen bonds. The catalyst preparation method and pretreatment were shown to be very important in the formation of active catalysts. The Au-Pd alloy having Au core-palladium shell structure with PdO dominance on the surface and bigger particle size was preferred than analogue catalyst consists of Au and Pd in metallic state with smaller particle size. In addition to that, the choice of support is crucial and this study discovered TiO: as a preferred support where it could assist in stabilising the active hydroperoxy species. The Au:Pd ratio was also found to be an important variable, and equal weight ratio between Au and Pd was shown to be the optimised ratio for methane oxidation either using addition of H2O2 or in-situ H2O2 approach. The synergistic effect of Au and Pd was confirmed by superior catalytic activity compared to monometallic catalysts. Reaction mechanism was proposed and it was based on catalytic evaluation data, stability of the products and oxidation with radical scavengers. The proposed mechanism was in line with the theoretical modelling studies on similar catalytic systems. Optimisation of Au based supported catalyst with copper as co-metal supported on TiO2 was shown to improve the oxygenate productivity and methanol selectivity as well as enhanced the H2O 2 utilisation. In particular, trimetallic 5wt%AuPdl.0wt%Cu/TiO 2 synthesised via impregnation method and calcined in static air gave more than double turn over frequency (TOF = 1.404) with methanol selectivity around 83% as compared to bimetallic 5wt%Au-Pd/TiO2 catalyst (TOF = 0.692, methanol selectivity = 49%). It was suggested in this study that copper is responsible in enhancing the formation of intermediate methyl hydroperoxide species and in some extent to block the non-selective sites for hydrogen peroxide decomposition and hydrogenation by disrupting the surface structure of Au-Pd alloy whilst at the same time maintaining the active sites (Au-Pd alloy) responsible for selective formation of methanol. The oxidation state of copper was shown to be the main factor in controlling the catalytic activity and selectivity. Copper in a combination of multiple oxidation states was preferred than single oxidation state.
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陳翠玲 and Chui-ling Chan. "Synthesis and luminescence studies of homo- and heteronuclear complexes of gold and copper." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31238178.
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Oseghale, Charles Ijogbemeye. "Gold copper based catalysts in the development of direct formic acid fuel cells." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/20827/.
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There is a growing awareness of the need for fundamental and applied research in energy storage and conversion due to the global climate issue with energy sources, environmental and human health challenges. In this work, development of a new synthesis route for catalysts, physicochemical and electrochemical research is reported for direct formic acid fuel cells. The synthesis method is based on the sodium borohydride reduction of (Pd2+, Cu2+, Au3+) precursor, stabilised by polyvinylpyrrolidone for the preparation of a highly stable catalysts with, well-controlled particle size distribution. The surface and bulk properties of the catalysts were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and electrochemically by cyclic voltammetry and chronoamperometry. The results obtained for Pd-C showed that a uniform XRD estimated the size distribution in a narrow particle size range with an average size of 1.4 ± 0.11 nm. Electrochemical studies for formic acid electrooxidation reveals that Pd-CH3BO3 + NH4F(21wt.%) presents superior catalytic activity (over 44 %) than that of the Pd-CPVP(43.5wt.%) synthesis route. For an equivalent electrode paste, Pd-CPVP(43.5wt.%) exhibited a greater electrochemical surface area (ECSA) than Pd-CPVP(43.5wt.%) but achieved a lower utilisation of palladium. The electrooxidation of the catalyst shows three times higher activity for formic acid oxidation than commercial gold nanoparticles dispersed on the carbon support. The enhanced catalytic performance is attributed to the electronic synergistic effect of copper and the specific gold structure promoting oxidation of adsorbed intermediate species. Overall, these findings have significant implications for practical direct formic acid fuel cells (DFAFCs) technology by the controlled Au-shell Cu-core anode catalysts application. Overall, palladium catalysts demonstrated better electrocatalytic activities for formic oxidation than Au and gold copper catalysts. This work is part of the initial stages of the effort to develop a low-cost gold-catalyst for DFAFCs technology.
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Attard, G. A. "The structure and reactivity of copper, silver and gold overlayers on W(100)." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382046.
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Simons, Andrew Murray. "A fundamental study of copper and cyanide recovery from gold tailings by sulfidisation." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/1799.
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Cyanide soluble copper in gold ores causes numerous problems for gold producers using cyanidation. This includes increased costs from high cyanide consumption and a requirement to destroy cyanide in the tailings before discharge into a tailings storage facility. This thesis details the results of fundamental studies of sulfidisation processes, such as SART (sulfidisation, acidification, recycle, and thickening), to recycle cyanide and in turn recover copper from gold cyanidation tailings.
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Tanda, Bennson Chemuta. "Glycine as a lixiviant for the leaching of low grade copper-gold ores." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/56525.
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The continuous depletion of high grade gold ores has shifted research focus towards the processing of low grade, complex ores containing impurities such as copper which is detrimental to the traditional cyanidation process.
Alkaline glycine solution selectively leached copper and gold over impurity elements such as Fe, Ca, Mg and Si from copper – gold ores. Copper was recovered from solution by solvent extraction and gold could be recovered by carbon adsorption while glycine is recycled.
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Benari, Max. "The corrosion of silver, copper, palladium and gold in dimethyl sulphoxide and water." Thesis, Benari, Max (1989) The corrosion of silver, copper, palladium and gold in dimethyl sulphoxide and water. PhD thesis, Murdoch University, 1989. https://researchrepository.murdoch.edu.au/id/eprint/51619/.
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The mechanisms of the corrosion reactions of Ag, Cu, Pd and An with CuII and FeIII in calcium chloride in DMSO and calcium bromide in DMSO have been studied. These results have been contrasted with studies carried out in comparable aqueous media. To determine the mechanisms, it was necessary to study the corrosion reactions, as well as the anodic and cathodic half reactions.
For the study of the anodic half reactions in calcium chloride in DMSO the metals dissolve in their low valent state, i.e. AgI, CuI PdII and AuI. It was also found that the anodic dissolution was favoured by the reduced nobility of the metals in DMSO calcium halide solution compared with aqueous calcium halide solution. The effect for gold was pronounced. The anodic reaction occurred at potentials 0.7 V less positive in calcium chloride in DMSO than in aqueous calcium chloride. The anodic study for silver showed that silver chloride film formation is suppressed in DMSO solution compared with aqueous solution. For a silver rotating disc, current densities were up to an order of magnitude greater in calcium chloride in DMSO than in comparable aqueous solution. For the anodic dissolution of copper in calcium chloride in DMSO, CuCl film formation was also suppressed, compared with aqueous calcium chloride solution. For the anodic reaction of palladium in calcium chloride in DMSO, oxide films were found to inhibit dissolution at low overpotentials.
Anodic sweep data for Ag, Cu, Pd, Au and Pt in calcium bromide in DMSO were found to be similar to those in calcium chloride in DMSO. The main distinguishing feature is that calcium chloride in DMSO is more resistant, by 0.25 V, to solvent oxidation than calcium bromide in DMSO.
The electrochemical properties of the cathodic half reactions Cu II + e Cu1 and FeIII + e Fe II were studied in calcium chloride in DMSO, calcium bromide in DMSO and lithium perchlorate in DMSO. Formal potentials, diffusion coefficients and heterogeneous rate constants were measured and contrasted with results from comparable aqueous solutions. Formal reduction potentials were less positive in DMSO than in water. Diffusion coefficients and heterogeneous rate constants were an order of magnitude less in DMSO than in water. Cyclic voltammetric studies in DMSO showed that the rate of reduction of FeIII in calcium chloride and lithium perchlorate is controlled by electron transfer. In calcium chloride in DMSO, the rate of CuII reduction is controlled by a slow prechemical step involving loss of chloride ion from the CuII complex ion.
The corrosion reactions of Ag, Cu, Pd and Au were studied using a rotating disc electrode. Data on the effect of rotation rate on corrosion potentials were combined with information on the kinetic behaviour of the two half reactions, to determine the rate controlling steps. The rate of silver corrosion by Cu II and FeIII in calcium chloride in DMSO is solution diffusion controlled. The same applies for silver corrosion by Cu11 in calcium bromide in DMSO. The corrosion rate in DMSO media is two orders of magnitude faster than in comparable aqueous solution. In aqueous halide solution the rate was found to be under mixed solid state and solution diffusion control. The mixed control is due to the changing concentration profiles of silver ion in the silver chloride film and the oxidant in the solution diffusion layer. The corrosion of copper and palladium by CuII in calcium bromide in DMSO is essentially cathodic diffusion controlled. When calcium chloride is used the reaction mechanisms are complicated by film formation. Gold is corroded by CuII in both calcium chloride in DMSO and calcium bromide in DMSO. In calcium chloride in DMSO the rate is slow and is electrochemically controlled. In calcium bromide in DMSO the rate is considerably faster and is solution diffusion controlled. For practical purposes. leaching of Ag, Cu, Pd and Au should be with CuII in calcium bromide in DMSO. The reactions are solution diffusion controlled and the metals will dissolve rapidly.
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李維傑 and Wai-kit Lee. "Syntheses, photophysics and photochemistry of polynuclear d10 complexes of copper(I) and gold(I)." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31234264.
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Calder, Andrew Frank. "The effects of temperature and ion dose on cascade collapse in gold and copper." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304961.
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Carew, Alexander Jon. "Fundamental studies into the catalytic properties of metal-oxide supported gold and copper nanoparticles." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367710.
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Roman, John W. (John William). "An investigation of low temperature transient liquid phase bonding of silver, gold, and copper." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13483.
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Cui, Zhihao. "Experimental and DFT Computational Study of the Electroreduction of Acetaldehyde on Copper and Gold." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618311775442498.
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Allison, Antonia E. "The Geology of the Bajo El Durazno Porphyry Copper-Gold Prospect, Catamarca Province, Argentina." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/249234.
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The Bajo El Durazno prospect is a small, gold-rich porphyry copper-type prospect located in Catamarca Province, northwest Argentina. It is one of a cluster of at least fourteen porphyry copper-type occurrences and numerous younger polymetallic epithermal veins, all of which are genetically related to the waning stages of magmatism that produced the Farallon Negro volcanic complex, an isolated Upper Miocene shoshonitic andesitic volcanic center. Porphyry copper-type hydrothermal activity at the Bajo El Durazno prospect is associated with a small east-northeasterly elongated andesite porphyry stock. The stock was emplaced at 8.7 m.y. into comagmatic and petrologically similar andesitic volcanic breccias that form the highly dissected basal remnants of the main eruptive center of the volcanic complex. Intramineral, crudely radial andesite porphyry dikes accompanied the development of concentric zones of hydrothermal alteration centered on the stock. These alteration zones of potassium-silicate alteration in the stock and adjacent wallrocks surrounded by an essentially coeval, weakly developed propylitic alteration zone. The propylitic alteration assemblage, which occurs as both pervasive replacement and as veinlets, consists mainly of chlorite, epidote, calcite, and magnetite, with lesser clays and zeolites. The potassium-silicate alteration zone is character iced by the replacement of primary minerals by secondary biotite, magnetite, anhydrite, quartz, sericite, and calcite. Roughly coeval and coextensive with the earliest stages of potassium-silicate and propylitic alteration was a brief period of magnetite alteration consisting mainly of well-banded magnetite ± quartz ± biotite veins. This volume also includes the development of irregular magnetite-rich masses in the stock of probable late-magmatic origin. Major copper-gold mineralization with minor silver and molybdenum developed during later stages of potassium-silicate alteration after the magnetite alteration event, although highest grade mineralization is commonly localized in areas of most intense magnetite alteration. The bulk of the mineralization occurs as veins within the stock and its wallrocks near their mutual contact; these veins contain quartz, calcite, magnetite, pyrite, chalcopyrite, and lesser sericite, chlorite, orthoclase, biotite, siderite, molybdenite, bornite, sphalerite, galena, tetrahedrite-tennantite, and native gold. Some of the gold and silver occur in solid solution in sulfide minerals, and supergene enrichment of copper is not economically significant. Copper and gold grades are generally less than 0.4% and 1 ppm, respectively. The three early alteration assemblages were later overprinted by patchy areas of phyllic alteration consisting mainly of the assemblage sericite, quartz, pyrite, and anhydrite/gypsum in an irregular northeasterly elongated halo. Phyllic alteration is developed to its greatest extent in an irregular annular zone straddling the boundary between the potassium- silicate and propylitic alteration zones and is generally coincident with the most highly fractured rocks in the prospect. Irregular patches of weak to intense silicification are superimposed on all other alteration types, and a number of distinctive, poorly mineralized, phyllically altered and silicified fracture zones are distributed in a somewhat radial pattern around the stock. Low grade disseminated(?) gold mineralization is found over one square kilometer in phyllically and propylitically altered rocks surrounding the central mineralized zone. A fluid inclusion study has revealed the presence of two hypersaline liquid-rich fluid inclusion types having salinities of 73.0-87.0 and 50.0-79.5 weight percent NaC1 + KCl equivalent, respectively, a single low salinity liquid-rich inclusion type (6.6-8.0 weight percent NaCl equivalent), and abundant vapor-rich inclusions. Hematite, anhydrite, and a variety of unidentified opaque and nonopaque minerals occur in many inclusions. Magnetite, potassium-silicate, and phyllic-silicic alteration in silicified zones formed at temperatures between 310° C and 500° C and were the product of the less saline of the two hypersaline fluids; this fluid episodically boiled. Copper-gold mineralization in potassium-silicate rocks probably peaked at about 395° C. Fluid salinities and temperatures gradually decreased with time, and during later stages of alteration they also decreased with greater distance from the hot center of the system, perhaps as a result of dilution. Although proof is lacking, the two high salinity fluids and the low salinity vapor may be magmatic in origin, and the low salinity fluid may represent a late-stage influx of meteoric water that encroached on the waning magmatic hydrothermal system. A depth of formation of 1.6 kilometers is estimated for the presently exposed portion of the Bajo El Durazno prospect based on the fluid inclusion data.
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Tauetsile, Peo Joanah. "Adsorption of Gold and Copper from Alkaline Glycine-based Leach Solutions using Activated Carbon." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/78006.
Full textAbstract:
This study evaluated and optimised the activated carbon adsorption (ACA) process for the recovery of metals from alkaline glycine leachates. The use of activated carbon for metals adsorption remains industry’s preferred choice for the recovery of precious metals, from dilute solutions. The adsorption behaviour of metal glycine complexes on activated carbon, which was studied through the use of isotherms and kinetics, confirmed that ACA can efficiently recover gold over copper from dilute glycine solutions.
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Wainwright, Alan John. "Volcanostratigraphic framework and magmatic evolution of the Oyu Tolgoi porphyry Cu-Au district, South Mongolia." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2760.
Full textAbstract:
The super-giant Oyu Tolgoi porphyry copper-gold deposits in the South Gobi
desert, Mongolia, consist of multiple discrete porphyry centers aligned within a north-northeast trending, >6.5 km long, arc-transverse mineralized corridor. The porphyries are linked to a tectono-magmatic event at ~372 Ma within a Devonian to Carboniferous volcanic arc, and U-Pb (zircon) geochronology records magmatic activity from ~390 Ma to ~320 Ma. The Oyu Tolgoi district underwent at least three discrete periods of syn- to post-mineral shortening and there is evidence for at least three unconformities within the Paleozoic sequence. Although the deposits were formed in an active orogenic
environment characterized by rapid uplift, their preservation is a reflection of climactic effects as well insulation from erosion by rapid burial under mass-wasted and pyroclastic material in the volcaniclastic apron of late-mineral dacitic volcanoes.
The porphyry copper-gold deposits are spatially and temporally related to
medium- to high-K calc-alkaline quartz monzodiorite (~372 Ma) and granodiorite (~366
Ma) intrusive phases that comprise the Late Devonian Oyu Tolgoi Igneous Complex
(OTIC). Adakite-like wholerock compositions as well as zircon grains with high
CeN/CeN*, EuN/EuN* and Yb/Gd in the sample populations from syn- and late-mineral
porphyry intrusions are different from younger intrusions that are not related to porphyry Cu-Au deposit formation. Moreover, mixed zircon populations within OTIC intrusions indicate that efficient assimilation of material from different host rocks by a convecting magma chamber occurred.
Mafic to intermediate volcanic units evolved from tholeiitic to calc-alkaline compositions, which is interpreted to be a reflection of marine arc maturation and
thickening. Felsic rock suites are dominantly high-K calc-alkaline, regardless of age.
Nd-isotopic geochemistry from all suites is consistent with magma derivation from
depleted mantle in an intra-oceanic volcanic arc and lead isotopic compositions indicate
that the sulfides in the porphyry Cu-Au deposits are genetically linked to the Late
Devonian magmas.
Magma mixing, adakite-like magmatism and rapid uplift and erosion in a juvenile
marine arc setting differentiate the ore-stage geologic environment at Oyu Tolgoi from other settings in active and fossil volcanic arcs.
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Haglund, Fredrik, and Svensson Johan. "The volatility race in Commodities : The optimal hedge ratio in Copper, Gold, Oil and Cotton." Thesis, Jönköping University, JIBS, Business Administration, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-88.
Full textAbstract:
Introduction: Companies that are dependent on different commodities as input or output are exposed to price risk in these commodities. The price changes can be expressed as volatility and higher volatility results in higher risk. Hedging the commodity contracts with futures can offset this risk. One of the most important questions in this field is to what extent the risk exposure should be hedged with futures contract, i.e. the optimal hedge ratio.
Purpose: The study aims to conduct an analysis of the variance in different commodities contracts and provide evidence of the optimal hedge ratio in the respective commodities.
Method: We used a quantitative study with daily spot and futures price changes of Copper, Gold, Cotton and Oil. We investigated the 6-month hedging behaviour where timeseries were created for the period January-June each year during 2001-2004. We used a simple linear regression of the futures and spot price changes and a minimum variance model in order to calculate the optimal hedge ratio.
Conclusion: Companies that are dependent on Copper, Gold, Cotton and Oil can significantly reduce the risk by engaging in futures contracts. The optimal hedge ratio for Copper is (96%), Gold (52%), Cotton (96%) and Oil (88%). By applying the optimal hedge ratio, a company may reduce their risk exposure up to 90% compared to an unhedged position.
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Stanley, Nicolette. "Effect of various biogeochemical processes on mercury methylation in copper-zinc and gold mine tailings." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27043.
Full textAbstract:
Mercury is a well known environmental pollutant. Anthropogenic sources include coal combustion, waste incineration and metal processing. In base metal mines, Hg is often left in the mining wastes (i.e., mine tailings). Once disposed of in open-air impoundments, these Hg-containing tailings can undergo various biogeochemical transformations, including Hg methylation. It is the methylated form of mercury (MeHg) that poses a threat to the environment, because it bio-accumulates at each level of the food chain. The present study was undertaken to assess the biogeochemical factors affecting Hg methylation in Cu-Zn and Au mine tailings. The study focused on the role of sulfate-reducing bacteria (SRB) because they are suspected to be associated with Hg methylation. Temperature, sulfate and organic carbon availability, along with SRB activity were tested as potential factors affecting Hg methylation in column experiments containing old Au tailings and fresh Cu-Zn tailings. The results first showed that SRB activity did not enhance Hg methylation in Cu-Zn tailings and Au tailings, indicating that iron reducing bacteria, and not SRB, along with abiotic methylation reactions played an important role. Cold temperatures did not slow down SRB activity and MeHg production, but the accidental freezing and thawing of the Cu-Zn tailings promoted the production of soluble MeHg. The mechanism responsible for this unexpected Hg methylation is however unknown. Elevated organic carbon and sulfate concentrations did enhance SRB activity, but not MeHg formation in the tailings, because increased sulfide production hindered Hg methylation. Tailings mineralogy played a significant role in the production of methyl mercury, Au tailings contained more soluble and solid-bound MeHg than Cu-Zn tailings. These results add to the increasing amount of information on Hg cycling in the environment, and indicate that SRB might not be the dominant Hg methylators in mining environments.
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Nchabeleng, Ramphagane Frank. "Gold recovery from waste mobile phones PCBs using ammonia thiosulphate leaching and copper cementation process." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2855.
Full textAbstract:
Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018.The rate of waste electrical and electronic equipment (WEEE) is growing at an alarming rate, especially in countries where markets are saturated with huge quantities of new electronic goods. Printed circuit boards (PCBs) are a substantial portion of the value contained in waste from WEEE although they are only 6% of the total weight. It is reported that WEEE is currently the fastest growing waste stream in South Africa as the general population’s access to electronic goods in the last decade has increased, especially access to mobile phones. PCBs are found in any piece of electrical or electronic equipment and consist of various metals including precious metals such as gold (Au), silver (Ag) and palladium (Pd). It is reported that gold has the highest economic incentive at 15,200 $ per ton of PCBs. The rapid introduction of new and advanced technology into mobile phones has caused mobile phones to have a relatively short life span, 1 to 2 years to be exact. Mobile phones printed circuit boards (MPPCBs) have more Au content compared to computer circuit boards. They contain 350 g/ton Au whereas computer (PC) PCBs contains 250 g/ton. This research project will recover gold from waste mobile phones PCBs pregnant ammonia thiosulphate leach solution using copper cementation. The cementation process is preferred to all the other technologies of metals extraction from solution due to ultrahigh purity metals that can be obtained and to the less consumption of materials and energy. Electronic parts on the PCBs were manually removed using pliers and screwdrivers. PCBs were then cut to smaller pieces of about 2 x 2 m. The pieces were crushed and milled respectively. Some of the particles were recycled back to the crusher to get finer particles. The particles were separated to particles of sizes between 0 and 1350 μm using a shaker. The comminuted fractions of the PCBs were then used in the leaching step. Batch cementation experiments were performed by bubbling N2 in glass reaction vessel with a working volume of 0.5 L. The reactor was connected to a circulating water bath for temperature control. The recovery percentage of gold at various temperatures, agitation speeds and different amounts of copper powder used, was determined while pH was monitored. The temperature was varied at 30 °C, 40 °C, and 50 °C and the agitation speeds at 300 RPM and 900 RPM. Copper powder was added at 0.5 g/L, 1 g/L, and 1.5 g/L. Gold concentrations were measured by atomic adsorption spectrophotometer (AAS). Scanning electron microscope (SEM) and Energy-dispersive x-ray spectrometry (EDS) analyses of the copper powder after cementation (precipitates) were used to determine the surface morphology and to evaluate the quantitative aspect of the precipitate. It was found that the recovery of gold from ammonia thiosulphate leach solution was greatly affected by agitation speed. At an agitation speed of 900 rpm, 40 °C and 0.5 g of Copper powder, 96% of the gold was recovered from the leach solution. The cementation rate increased as temperature was elevated from 30 to 40 °C, but slightly decreased as the temperature reached 50 °C. The change in experimental conditions affected the gold concentration on the precipitate recovered. This study will provide a possible solution to the WEEE problem and more specifically mobile cell phones, in South Africa.
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Green, Bradley. "A study of the Wilkins and Green and Gold Copper-gold prospects, Olary Block, South Australia with emphasis on petrology, geochemistry and ore mineralogy /." Title page, contents and abstracts only, 1996. http://web4.library.adelaide.edu.au/theses/09SB/09sbg811.pdf.
Full textAbstract:
Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1998.Australian National Grid Reference (SI 54-2) 1:250 000. Four folded maps in pocket pasted onto back cover. Includes bibliographical references (leaves 62-68).
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Carr, Frank. "Government decision-making and environmental degradation: a study relating to mining activities in Papua New Guinea." Thesis, Carr, Frank (2007) Government decision-making and environmental degradation: a study relating to mining activities in Papua New Guinea. Masters by Research thesis, Murdoch University, 2007. https://researchrepository.murdoch.edu.au/id/eprint/502/.
Full textAbstract:
Papua New Guinea (PNG) is a country possessing abundant resources of gold, oil, copper, timber, and fish stocks. It is hampered in its development and management of these resources, however, by serious problems of governance and corruption. These problems are evident throughout the economy and also in the management of the environment. The level of environmental damage caused by the mining industry in PNG is now such that it will require extensive rehabilitation, if the areas affected can, indeed, ever be fully rehabilitated. The mining companies which precipitated this damage were licensed and encouraged by the PNG Government in the initiation and exercise of the mining operations. The resulting environmental impact has affected the lives of thousands of New Guineans to their detriment. The degradation caused remains
unredressed.
Compounding the problem, there is a growing reliance by Papua New Guinea on mineral exploitation for foreign direct investment, government revenues, and foreign exchange. Gold exports accounted for the biggest share of export revenues in 2002 representing 37.5% of the total. In light of this growing dependency on mining activities, there is a correspondingly urgent requirement to address the deficiencies in the administrative, monitoring, and policing aspects of the protection of its environment.
Despite the public evidence of the damage to the environment and the ensuing affect on the people of Papua New Guinea by mining activities; and despite universal condemnation of these activities and the companies responsible; the companies continue to conduct these activities without official hindrance and with little apparent concern for the long-term ramifications of their actions.
This thesis will examine the degradation resulting from the mining activities of companies in Papua New Guinea over the last three decades - particularly those of Placer Dome's Porgera gold mine, BHP's Ok Tedi gold and copper mine (the waste from both of which is dumped into the Ok Tedi and Strickland rivers which are tributaries of the Fly River and form part of the Fly River system) and Lihir Gold Limited's gold mine on Lihir Island. It will examine the extent to which the Government of Papua New Guinea may have wittingly (in the sense of a prescience as to the possible or probable likelihood of deleterious impact) or unwittingly contributed to that degradation as a result of its actions or omissions.
Studies of available literature suggest that there has been little attention paid to the subject of culpability on the part of successive PNG governments in matters of environmental damage. This research will contribute to reducing this gap in the literature by focusing on possible motives of the PNG government and its actors which precipitated those decisions and which resulted in environmental degradation. The discussion will examine the likely motivation of the PNG government in its deliberations and decisions and the extent to which corruption and incompetence may have played a role.