M.Sc. / The leaching of chalcopyrite (CuFeS2) concentrate in a ferrous iron promoted aerobic/anaerobic controlled low potential sulphate system was investigated by using the duel metabolic (aerobic ferrous iron oxidation and anaerobic ferric iron reduction) capabilities of Ferroplasma JTC 3. The experimental work conducted in this study was divided in three sections. The first section focussed on the identification and phylogenetic classification of Ferroplasma JTC 3, first identified amongst a mixed microbial population in a 55 oC pyrite concentrate-fed bioreactor operated at Johannesburg Technology Centre (BHP Billiton, JTC). Based on the 16S rDNA sequence and the phylogenetic analysis, Ferroplasma JTC 3 represents a new species member under the genus of Ferroplasma. The optimal growth temperature of Ferroplasma JTC 3 was determined at approximately 53 oC (moderate thermophile). The second section of this study focussed on the isolation, basic metabolism and growth conditions of Ferroplasma JTC 3, specifically directed towards the chalcopyrite leaching related experimental work. An important aspect of this study was to compare low potential chalcopyrite leaching (potential below 400 mV vs. Ag/AgCl) against high potential chalcopyrite bioleaching (potential above 600 mV vs. Ag/AgCl) in terms of the rate of copper extraction. Microbial growth and the rate of ferrous iron oxidation are essential in order to maintain a high potential during an extended leach period, which was typically the case in the high potential chalcopyrite leaching experiments performed during this study. Ferroplasma JTC 3 required yeast extract as sole carbon source (chemo-heterotrophic) for growth via aerobic ferrous iron oxidation. Taking into account no carbon dioxide enrichment via aeration, chemo-autotrophic growth by means of ferrous iron oxidation was poor with carbon dioxide as sole carbon source. The anaerobic metabolism of Ferroplasma JTC 3 was utilized in assisting with solution potential control during the low potential chalcopyrite leaching work. The anaerobic metabolism enabled the reduction of ferric iron (decrease redox potential) in the presence of elemental sulphur and yeast extract. Elemental sulphur was shown to be a requirement for Ferroplasma JTC 3 assisted ferric iron reduction, which was not influenced by different ferrous/ferric iron based redox potentials. The third section covers the main focus of this study, which was the low potential leaching of chalcopyrite in combination with the metabolic capabilities of Ferroplasma JTC 3. The major challenge of low potential chalcopyrite leaching in an acidic environment is maintaining the solution potential below the critical upper limit (400 mV vs. Ag/AgCl) of the low potential window for prolonged periods of time. The reason is the slow chemical oxidation of ferrous iron in the presence of oxygen, which increases the leach solution potential above the critical upper limit before complete copper dissolution is obtained. The aim of this study was to maintain a low solution potential environment in a bioreactor via a programmable electronic gas control system, capable of creating an aerobic environment until the solution potential would reach the upper low potential limit (400 mV vs. Ag/AgCl) due to ferrous iron oxidation (chemically or via Ferroplasma JTC 3) and then switch to an anaerobic environment. During the anaerobic environment, the aim was to decrease the solution potential to a lower potential set point via chalcopyrite oxidation by ferric iron (ferric iron reduction) and by employing the ferric iron reduction metabolism of Ferroplasma JTC 3. With the particular aerobic/anaerobic solution potential control system, in conjunction with the metabolic capabilities of Ferroplasma JTC 3, the solution potential could be controlled within the critical low potential region, but no chalcopyrite leaching could be obtained during the anaerobic phase. The lack of chalcopyrite leaching during the anaerobic phase was due to inability of ferric iron to act as oxidant of chalcopyrite after the mineral was pre-leached in the preceding aerobic phase. The “oxidative acid leach” mechanism was identified as the dominant leach reaction that prevailed during the aerobic low potential stage in each of the aerobic/anaerobic control experiments conducted, in which oxygen acts as oxidant of chalcopyrite (electron acceptor) in the presence of protons (H+) (acidic environment), instead of ferric iron in an acid environment. The “boundary potential”, which is the maximum solution where no electron flow occurred to the ferrous/ferric couple from “pre-leached” chalcopyrite, was identified in the region of 450 mV (Ag/AgCl). Under the experimental conditions within this study, the leaching of chalcopyrite within the aerobic phase of the aerobic/anaerobic control experiments was superior to the Ferroplasma JTC 3 mediated high potential leaching, but complete copper dissolution could not be obtained with the combined aerobic and anaerobic system. Ferric iron precipitation as a function of pH was proposed as a tool for solution potential control, instead of controlling the potential by limiting oxygen to the leach system. In controlling the solution potential via pH, almost complete copper dissolution from chalcopyrite was obtained, while maintaining the solution potential below the critical upper limit of the low potential region.

We had demonstrated that, by controlling and changing the temperature, reaction time and washing agents, the morphology and powder size of CuInSe2 can be altered considerably. CuInSe2 was synthesized by a solvothermal route as described by Y. Qian et al. By synthesizing nanorods, we can control the distance which the electrons are transported in hybrid solar cell with conjugated polymers. With the tuning of the band gap by controlling the nanorod length, we can increase the opportunity of orbits overlap between the CuInSe2 material and the PBO polymer matrix.. The synthetic temperature 1800C and reaction time 48 hrs are the best condition in our experiment. By using D.I water and ethanol as washing agents, we can find different morphology of spherical and nanowire. However, we fabricate hybrid solar cell by using these CuInSe2 powders in PBO conjugated polymers. By preparing hybrid solution in different concentration and controlling spin coating rate, we fabricate solar cells device successfully. From the I-V characteristics, we can get noticeable characteristics of diode. Then, we calculate the fill factor (F.F.) with the open-circuit voltage¡]Voc¡^and short-circuit current¡]Isc¡^

Reproduction de : Thèse de doctorat : Chimie inorganique : Reims : 2005. / Titre provenant de l'écran titre. Bibliogr. f. 213-228.

No description available.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "August 2005." Includes bibliographical references (leaves 81-82). Online version available on the World Wide Web.

Th. doct.-ing.--Nancy, I.N.P.L., 1979.

Acidiphilium cryptum is a heterotrophic acidophile commonly found in acidic environments and industrial bioleaching operations. Attachment to mineral surfaces may serve to maintain this organism in aqueous environments where it is subject to removal by hydrodynamic forces. Using indirect and direct methods we have looked at the binding of A.cryptum to chalcopyrite (CuFeS₂) and other mineral ores to determine whether specific adhesins mediate binding. A modified ELISA binding assay (the Ore ELISA) was developed to measure direct adherence. Finely ground chalcopyrite was bound irreversibly to the walls of an ELISA plate, the organisms were added and after incubation and washing, the number of attached bacteria were assessed by reacting with anti-A.cryptum antibody followed by goat anti-rabbit IgG conjugated to alkaline phosphatase. This assay was found to be sensitive, rapid and reproducible. The Ore ELISA allowed direct binding measurement in the presence of various inhibitors and provided a rapid screening method for adherence-defective mutants. Adherence was shown to be saturable and increased slightly as pH decreased. A moderate increase in binding affinity was recorded in the presence of monovalent and divalent cations and EDTA. Various bactericidal agents and pentose and hexose sugars had no effect on chalcopyrite attachment. Reducing agents had little effect on cell adherence. A strong increase in adherence was observed in the presence of surface active agents. Bovine serum albumin and gelatin were both found to markedly reduce mineral surface binding. Competition for attachment sites between A.cryptum and the autotrophic acidophile, Thiobacillus ferrooxidans, showed that each organism binds to unique sites on the chalcopyrite surface. A.cryptum mutant strains displaying reduced adherence to chalcopyrite were shown to lack a 31.6 kDa outer membrane protein. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

M.Sc. / CuInSe2/CdS/ZnO heterojunction solar cells are currently one of the most promising technologies for the production of economically viable energy in the form of electricity. The key component of this thin film solar cell device is the chalcopyrite absorber film. CuInSe2 and its related alloys such as Cu(In,Ga)Se2 have been deposited by a number of techniques, including methods which have been demonstrated to be scalable to mass production volumes. In this study attention was focused on (i) developing a relatively simple deposition technology for the production of chalcopyrite absorber films, (ii) detailed characterization of the semiconductor thin films in terms of the experimental parameters and (iii) fabrication of completed CuInSe2/CdS/ZnO solar cell devices. Metallic precursors comprising of copper and indium were deposited with electron-beam evaporation. The number of elemental layers in the precursor stack as well as the substrate temperature was optimized in order to produce metallic alloys with optimum structural properties. These precursors were subsequently reacted in vacuum to elemental Se vapour or to H2Se/Ar at atmospheric pressure in a separate diffusion reactor. In order to investigate the growth kinetics of the respective processes, the precursors were reacted to the Se in the temperature range between 350°C and 450°C. The structural features (morphology, presence of crystalline phases and bulk compositional properties) of the respective films were compared and correlated against the growth parameters. From this systematic study, optimum growth parameters were determined for the production of completed solar cell devices. / Professor V. Alberts

No description available.

No description available.