Thesis (PhDApSc)--University of South Australia, 2003.

Submitted by DEBORA MARIA ALVES VIEGAS null (de-viegas@hotmail.com) on 2016-05-19T20:21:13Z No. of bitstreams: 1 Dissertação - Debora Viegas 2016.pdf: 4214783 bytes, checksum: 5434f9b5c2bdcbea1bd5b8d7bbaa7527 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-05-23T18:52:19Z (GMT) No. of bitstreams: 1 viegas_dma_me_araiq.pdf: 4214783 bytes, checksum: 5434f9b5c2bdcbea1bd5b8d7bbaa7527 (MD5) / Made available in DSpace on 2016-05-23T18:52:19Z (GMT). No. of bitstreams: 1 viegas_dma_me_araiq.pdf: 4214783 bytes, checksum: 5434f9b5c2bdcbea1bd5b8d7bbaa7527 (MD5) Previous issue date: 2016-05-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O desenvolvimento tecnológico dos setores industriais associados à mineração e metalurgia vem crescendo nas últimas décadas devido à busca incessante por melhorias na qualidade de vida. Se por um lado a demanda por metais é crescente, por outro, a indústria de mineração está diante da problemática em relação ao esgotamento das reservas. Isso impõe a necessidade de se extrair metais a partir de minérios de baixos teores e também de rejeitos industriais. Para tanto são necessários processos que exijam baixos custos de investimento e de operação para que a extração se torne viável economicamente, e a biolixiviação é a tecnologia que aparece como a principal alternativa diante dos processos convencionais. O cobre tem sido um dos metais mais importantes por mais de cinco mil anos, devido a suas propriedades e formação de ligas metálicas. O cobre é um dos metais de maior interesse econômico. Cerca de 70% deste metal é encontrado na natureza na forma de calcopirita (CuFeS2). É o mineral mais abundante entre todos os tipos de minérios de sulfeto de cobre. A biolixiviação de cobre a partir de calcopirita é considerada mais econômica e ambientalmente sustentável que o processo convencional pirometalúrgico, especialmente quando os minérios de sulfeto de cobre estão presentes em baixo teor. No entanto, a taxa de oxidação lenta bacteriana continua a ser um grande problema para ser resolvido na biolixiviação. Sendo assim, estratégias para melhorar a atividade bacteriana na superfície do sulfeto mineral têm sido amplamente exploradas por muitos autores. Recentemente a adição de substâncias de origem biológica como os aminoácidos também tem sido um fator testado em ensaios com o objetivo de melhorar o desempenho do processo, como a L-cisteína, um aminoácido importante sulfuroso que despertou grande interesse devido a sua capacidade de acelerar o processo de biolixiviação. O principal microrganismo envolvido neste processo é a Acidithiobacillus ferrooxidans, bactéria mesófila capaz de obter energia a partir da oxidação de íons ferrosos e de compostos de enxofre reduzidos. Além dessa, a Leptospirillum ferrooxidans, também mesófila e capaz de obter energia apenas a partir de oxidação de íons ferrosos. Neste contexto, o presente trabalho teve como objetivo avaliar estas diferentes espécies bacterianas isoladas e em consórcio quanto a capacidade de solubilizarem cobre a partir da calcopirita e avaliar a melhora da eficiência do processo com a adição de cisteína no meio. Foi realizado um ensaio prévio de oxidação de íons ferrosos na presença de cisteína para determinar a concentração inibitória do aminoácido para o crescimento das linhagens. Posteriormente realizou-se o ensaio de biolixiviação em frascos agitados a 150 rpm, 30 oC, na presença de 2,5% (m/m) de calcopirita em meio T&K, 5% (v/v) do inóculo e 10-3 mmol.L-1 de cisteína. Avaliando a influência dos consórcios e das espécies isoladas no processo, determinou-se que os frascos que continham a bactéria At. ferrooxidans – LR adaptada apresentaram as maiores porcentagens de recuperação (23,2%), após 35 dias de ensaio. Os sistemas abióticos apresentaram uma recuperação ínfima de cobre, chegando a apenas 6%, em um potencial médio de 350 mV (Ag/AgCl). A adição de cisteína promoveu aumentos na recuperação de cobre, comparado à mesma condição na ausência de cisteína. Foram detectadas diferenças na extração de cobre nas diferentes condições inoculadas estabelecendo-se a seguinte ordem decrescente: At. ferrooxidans – LR + cisteína (25,3%) > At. ferrooxidans – LR > mutante + cisteína > L. ferrooxidans + cisteína > mutante > L. ferrooxidans (18,0%). Por fim uma análise estatística foi realizada para determinar a correlação entre os parâmetros estudados, pH, Eh e [Fe2+]/[Fe3+] e a solubilização de cobre para cada microrganismo. Os resultados indicaram uma alta correlação (>75%) em 85% dos casos, onde para a bactéria At. ferrooxidans a maior correlação encontrada foi ao parâmetro [Fe3+]/[Fe2+] e diferentemente para a bactéria L. ferrooxidans que a maior correlação foi a que relacionou a solubilização com o pH. / Technological development of mining and metallurgical industries has increased in recent decades due to constant search for improving life quality. Mining industries are now facing an issue related to the depletion of reserves since the demand for metals is growing progressively year after year. Therefore, he need of extracting metals from low grade ores and industrial wastes become an important key to this sector. For this purpose, processes that require low investment and low operating costs for metal extraction are preferentially used for being economically feasible compared to conventional processes. Bioleaching is one of the main alternative technologies for extracting metals, such as copper one of the most important metals for over five thousand years, due to its properties and formation of metal alloys. Copper is one of the largest economic interest metals. About 70% of this metal is found in nature as chalcopyrite (CuFeS2). This is the most abundant mineral among all types of copper sulfide ores. Copper bioleaching from chalcopyrite is considered more economically and environmentally sustainable than conventional pyrometallurgical processes. The main microorganisms involved in this process are the well-known Acidithiobacillus ferrooxidans, mesophilic bacteria capable of using ferrous ions and reduced sulfur compounds as energy source through oxidative reactions Leptospirillum ferrooxidans also mesophilic and able to oxidize ferrous ions as energy source. The addition of carbohydrates, proteins and other substances of biological origin has also been a factor tested in assays aiming to improve the performance of the process. In this context, this study aimed to evaluate the ability to solubilize copper from chalcopyrite mediated by both At. ferrooxidans and L. ferrooxidans separately and combined, as a consortium. Besides, to evaluate the efficiency of the process adding cysteine in the growth medium. A previous study of oxidation of ferrous ions in the presence of cysteine was performed to determine the inhibitory concentrations for the growth of the strains. In general, bioleaching tests were performed in shake flasks at 150 rpm, 30 °C, in the presence of 2.5% (w/v) of chalcopyrite in T&K medium, 5% (v/v) inoculum and 10-3 mmol.L-1 of cysteine. Evaluating the influence of the consortia and species isolated in the process, it was determined that the vials containing the At. ferrooxidans - LR adapted showed the highest recovery percentages (23.2%) after 35 days. Abiotic systems showed a negligible recovery of copper, reaching only 6% in an average potential of 350 mV (Ag / AgCl). The addition of cysteine promotes an increase in copper recovery compared to the same condition in the absence of cysteine. Differences were detected in the copper extraction in different conditions inoculated by establishing the following descending order: At. ferrooxidans - LR + cysteine (25.3%) > At. ferrooxidans - LR (23.5%) > mutant + cysteine (23.0%)> L. ferrooxidans + cysteine (20.3%)> mutant (20.0%)> L. ferrooxidans (18.0%). Finally a statistical analysis was performed to determine the correlation between the parameters studied, pH, Eh and [Fe3+]/[Fe2+] and copper solubilization for each microorganism. The results showed a high correlation (>75%) in 85% of cases, where for bacteria At. ferrooxidans the highest correlation was found to the parameter [Fe3+]/[Fe2+] and differently for the bacteria L. ferrooxidans the highest correlation it was related to the solubilization pH.

M.Sc. / I-III-VI2 compound semiconductors are important photovoltaic (PV) materials with optical and electrical properties that can be tuned for optimum device performance. Recent studies indicated that the efficiencies (1) > 18%) of CuInSe2/CdS/ZnO thin film devices are in good agreement with that of standard silicon cells. In this study, CuInSe 2 absorber films with excellent material properties were produced by relatively simple and reproducible two-stage growth techniques. In these approaches, metallic precursors (Cu/InSe, InSe/Cu, Cu/InSe/Cu and InSe/Cu/InSe) were deposited by thermal evaporation from specially designed graphite heaters at temperatures around 200°C. In the second stage of the process, the alloys were exposed to elemental Se vapour or H2Se/Ar gas. A systematic study was conducted in order to determine optimum growth parameters for the different deposition processes. Optimum material properties (homogeneous and dense films with a high degree of compositional uniformity) were obtained when InSe/Cu/InSe precursors were selenized in elemental Se vapour or H2Se/Ar gas. Comparative studies also indicated that the reaction kinetics is enhanced when H2Se/Ar is used as chalcogen source. Fully selenized films were obtained at temperatures as low as 450°C in a H2Se/Ar atmosphere, compared to temperatures of 600°C in the case of Se vapour. The optical and electrical properties of the absorber layers were accurately controlled by small variations in the bulk composition of the films. A standard CdS/ZnO window layer technology was also developed in our laboratories and preliminary solar cell devices were fabricated and evaluated.

Ph.D. / One of the solutions to the high cost of solar modules is the development of thin film solar cell technologies, which enable material saving, few processing steps, good stability in outdoor testing, high conversion efficiency and flexibility for large area coatings. Polycrystalline CuInSe2 (CIS) thin films and related quaternary and pentenary compounds such as Cu(In,Ga)Se2 (CIGS) and Cu(In,Ga)(Se,S)2 (CIGSS) are the most promising thin film candidates to fulfil the requirements of economically viable solar modules. Presently CIS, CIGS and CIGSS thin film solar cells are prepared mostly by two – stage deposition processes, where Cu-In-Ga alloys are deposited, followed by selenization and/or sulfurization using H2Se/Ar and/or H2S/Ar gases, Se and/or S vapours. Key problems related to this approach are (1) the widely reported compositional change and loss of material during the annealing and selenization stages, and (2) the formation of a graded film structure with most of the Ga residing at the back of the film, due to the difference in the reaction rates between the binary selenides. The present study aims to develop CIGS quaternary and CIGSS pentenary thin film absorbers which are substantially homogeneous and single phase. In order to achieve this aim different deposition processes were developed. This included thermal evaporation of pulverized compound materials from a single crucible with and without subsequent reaction of the precursors in Se vapour or H2Se/Ar atmosphere. Alternatively, controlled partial selenization/sulfurization of the Cu-In-Ga magnetron sputtered precursor films under controlled conditions of reaction time, temperature and gas phase concentration were applied to produce CIGSS films. The latter approach allowed homogeneous incorporation of Ga and S species into CIS compound material, and with that a corresponding increase of band gap of the material in the active region of the solar cell. CIGS quaternary and CIGSS pentenary based solar cells were completed by depositing a CdS buffer layer of around 50 nm thickness, high resistivity ZnO and low resistivity Al – doped ZnO with thicknesses of about 50 nm and 0.5 μm respectively. I-V measurements on fabricated solar cells, under standard A.M. 1.5 conditions, demonstrated good solar cell device quality with efficiencies of about 10 % and 15% respectively.

No description available.

The flotation of chalcopyrite and sphalerite has been accomplished without the use of collectors. Of the six chalcopyrite ores tested in the present work, some floated well using only a frother, while others required the addition of sodium sulfide, presumably to remove the hydrophilic surface oxidation products. On the other hand, the flotation of sphalerite ores was found to require both sodium sulfide treatment and copper-activation. The ratio of these two reagents was most critical, the optimum Cu²⁺/S²⁻ atomic ratio being approximately 0.17 over a wide range of reagent dosages. Potential measurements taken during both batch and micro-flotation experiments demonstrated that the collectorless flotation of chalcopyrite was possible only in oxidizing conditions, which confirms an earlier finding by Heyes and Trahar (1977). In relation to this phenomenon, three possible mechanisms have been discussed: i) elemental sulfur formed under oxidizing conditions is responsible for the collectorless flotation, ii) polysulfide ions formed during the incipient surface oxidation process render the mineral hydrophobic, and iii) HS⁻ ions, which may render the mineral hydrophilic upon adsorption, are removed from the system under oxidizing conditions. The first mechanism may operate primarily in acidic solutions, while the second mechanism operates in alkaline solutions where elemental sulfur is thermodynamically unstable. The third mechanism is based on the assumption that a clean, unoxidized surface is inherently hydrophobic. Spectroscopic evidence has been presented to support these proposed mechanisms. / Master of Science

No description available.

Theoretical considerations for the use of chalcopyrite ternary I-III-VI₂ compounds in heterojunction photovoltaic conversion devices are presented, followed by an in-depth study of the structural, optical, and electrical characteristics of multi-source evaporated CuGaSe₂ thin films as determined by processing. Film composition was identified as the primary variable for affecting the microstructure and optical-electrical behavior of the films. Film composition was in turn dependent upon elemental flux rates and substrate related effects. Films deposited on glass and bare alumina substrates were richer in selenium than films deposited on molybdenum coated substrates. Cu-poor, near stoichiometeric, and Cu-rich compositions were obtained by varying the Cu/Ga flux ratio. Cu-poor films deposited on bare ceramic substrates were characterized by secondary impurity phase content and a tendency for cubic CuGaSe₂ formation. The cubic nature of optically thin films deposited on glass was substantiated by a lack of crystal field splitting of the valence band as observed by optical absorption measurements. Cubic-tetragonal phase behavior was monitored on optically opaque samples by observation of intensity-independent (112)/(111) x-ray diffraction peak shifts. Cu-poor films on glass were also characterized by surfaces pitting at substrate temperatures in excess of 450°C which may be related to the high surface energy of gallium. Cu-poor films deposited on molybdenum coated alumina substrates exhibited less impurity phase formation and were largely single-phase tetragonal CuGaSe₂. Cu-rich films on all substrates contained CuₓSe impurities and tetragonal CuGaSe₂.

The present study is targeted on the optimization of the flotation conditions for the improvement of the industrial flotation practice. Part I is focused on the improvement of the flotation of Mountain Pass mine ore for the beneficiation of rare earth elements. The objective is to improve the rare earth recovery of Mountain Pass ore by developing a novel flotation reagents' scheme, meanwhile reducing the flotation temperature to a cost-efficient level and simplifying the flowsheet. Surface chemistry study by contact angle, zeta potential and microflotation tests indicate that a mixed collector consisting of oleic acid (OA) and sodium octanohydroxamate hydrate (OHA) is beneficial for rare earth flotation. More importantly, salicylhydroxamic acid (SHA) is also a promising collector due to the high selectivity. Lab-scale flotation tests using SHA as collector show that 80-90% REE recovery and <20% gangue recovery are achieved at 40°C~60°C, which yield a rougher concentrate of 30%~40% REO. A novel flotation scheme has been developed towards Mountain Pass rare earth mine. The new scheme is of both high selectivity and high recovery, meanwhile the dosage of reagent required is much less, and the flotation temperature is also significantly reduced. Interactive adsorption models are built up through FT-IR and AFM study. The interaction of collector with bastnaesite surface is illustrated. Hydroxamic acid collectors (OHA and SHA) adsorb on bastnaesite surface by forming stable chelating complex. The selectivity of collectors towards bastnaesite flotation is summarized as SHA>OHA>OA. Part II is focused on the improvement of the flotation of Resolution Copper's Superior mine ore at an elevated temperature for the beneficiation of chalcopyrite. Because the Resolution Copper ore is mined from a deep, hot, underground mine, the temperature of ROM (run of mine ore) is much higher than that of the ore usually processed in a typical open-pit copper mine. The ore temperature will still be high during flotation. It is therefore critical to carry out a systemic study on the flotation of Resolution Copper ore at elevated temperatures and clarify the impact on flotation. An overall beneficial effect is observed in high temperature flotation through a lab-scale flotation study. Further action of temperature control is not necessary. The contact angle results indicate that surface hydrophobicity is enhanced at elevated temperature, of which the surface morphology change (shown by AFM images) of xanthate adsorption species (dixanthogen) is the key factor.

No description available.