Thesis (PhDApSc(MineralsandMaterials))--University of South Australia, 2002.

Thesis (Ph.D.)--Murdoch University, 2009. / Thesis submitted to the Faculty of Minerals and Energy. Includes bibliographical references (leaves 280-289)

Thesis (M.S.)--West Virginia University, 2010. / Title from document title page. Document formatted into pages; contains vii, 47 p. : ill. Includes abstract. Includes bibliographical references (p. 46-47).

Th. doct-ing.--Nancy, I.N.P.L., 1978.

M.Tech. (Extraction Metallurgy) / Please refer to full text to view abstract

Chalcopyrite (CuFeS2) is the most abundant of the copper sulfides and also one of the most refractory for leaching. Several processing routes have been proposed to overcome drawbacks associated with environmental problems related to copper extraction from this mineral. Atmospheric leaching in acidic ferric sulfate is regarded as being particularly attractive over other hydrometallurgical systems. However, the challenge has been to overcome the problem of slow extraction rates due to passivity encountered at high solution potentials in this system. This highlights the need to investigate better operating conditions to optimize copper extraction and prevent the problem of passivation, and to develop suitable modeling tools to assess and diagnose leaching performance. In this work, a dissolution rate expression for chalcopyrite leaching in acidic ferric sulfate media is proposed accounting for effects in the active and passive regions under potentials from 415 to 550 mV (Ag/AgCl). A model of chemical speciation in the bulk solution elucidates the idea of passivation caused by precipitation of ferric species and their consequent adsorption onto the chalcopyrite surface. Electrochemical studies on massive samples of chalcopyrite involving characterization and modeling of the anodic and cathodic half-cell reactions of chalcopyrite leaching together with mixed potential considerations lead to the development of the mathematical expression for dissolution rate. The mathematical model was calibrated with electrochemical parameters and results are in good agreement with real leaching data from batch tests for solution potential regions where passivity is not observed. On the other hand, the passive region was modeled by means of adjusting parameters related to adsorption energies of the passivating species. Results of the model for this region deviate from real data as potential becomes higher probably due to diffusion resistance through a layer composed of ferric complexes. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

In this work, the growth and characterisation of the chalcopyrite semiconductor CuGaS2 is presented. The purpose of this study is to gain a better understanding of the defect chemistry of this class of materials through a systematic study relating the structural and optical properties to the composition of thin films grown by metalorganic vapour phase epitaxy. Details associated with the optimisation of the growth process are presented in a format relating the changes in the composition and morphology to variations in the growth process. The structural properties of thin films grown on GaAs(001) substrates are described. A dominance of polycrystalline growth is found to occur for Cu-rich material, whereas near-stoichiometric to Ga-rich material is typified by epitaxial growth. Secondary phases are identified by X-ray diffractometry and Raman spectroscopy for severely non-stoichiometric material. In some cases, the formation of the cubic zincblende and CuPt polytype of CuGaS2 are identified by transmission electron microscopy. It will be shown that changes in the Cu/Ga ratio of the solid strongly influence the photoluminescence response of the layers. Weak excitonic luminescence is observed for both slightly Ga-rich and Cu-rich material. Near stoichiometric layers exhibit luminescence centered at ~2.4 eV. Cu-rich layers are dominated by a line occurring at ~2.1 eV, whereas a different line at ~2.25 eV dominates for Ga-rich layers. A clear picture emerges of the radiative mechanisms dominating for Cu-rich and Ga-rich layers.

Leaching of chalcopyrite by Thiobacillus ferrooxidans under standard microbiological leaching conditions resulted in simultaneous solubilization of copper, iron and sulfur. The sulfide portion was oxidized preferentially over iron in solution suggesting a direct attack mechanism by the bacteria on the mineral particles. Copper extractions were low, 29-44%, with maximum specific copper extraction rates of the order of 0.001-0.006 h⁻¹ and cell yields per unit of copper released 4-43mg TOC/mg Cu. Leaching under redox-controlled conditions required a minimum pulp density, ca. 200 g/1, to result in elemental sulfur production. Some unknown factor, resulting from biological leaching activity under standard conditions and transferred with the liquid phase of the inoculum, was needed for the leach to occur under redox-controlled conditions. Copper extractions of 44-100% were achieved. Maximum specific copper extraction rates were of the order of 0.002-0.007 h⁻¹ with cell yield per unit of copper released of the order of 0.12-3.32mg TOC/g Cu for batch cultures. Ferrous iron in solution appeared to be the energy source for cell growth under redox-controlled conditions. The cells' sulfide oxidizing capacity seemed to be inhibited at the metabolic regulation level and not at the enzyme synthesis level. Cells growing under the standard conditions underwent a lag phase, upon transfer to the redox-controlled medium. During this lag phase low metal solubilization rates and low S⁰ production occurred, but when cell growth started, the leaching rates increased and the mineral dissolved rapidly. Electron diffraction X-ray analyses were carried out to investigate the role of silver in the controlled-redox leaching. No silver was observed to be on the surface of the chalcopyrite particles before or after the initial activation stage of the controlled-redox process. Silver deposits were observed after many hours of leaching. A mathematical model to describe the kinetics of microbial leaching, using a shrinking particle concept as its basis, was developed. When tested against data from the literature for leaching of Zinc from ZnS concentrate it was able to predict particle size as a function of leach time. It also gave reasonable predictions of particle size as a function of leach time for standard leaching of chalcopyrite but failed to predict accurate values for particle size as a function of leach time for the controlled-redox process. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

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