Dissertations / Theses: 'Bacterial leaching'

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Ndlovu, Sehliselo. "Bacterial leaching of pyrite single crystals." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401694.

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Deveci, Haci. "Bacterial leaching of complex zinc/lead sulphides using mesophilic and thermophilic bacteria." Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341175.

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Seifelnassr, A. A. S. "Bacterial aided percolation leaching of copper sulphide ores." Thesis, Bucks New University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234445.

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Garcia, Íris Gabriela [UNESP]. "Consórcios microbianos associados a ambientes de minas: obtenção, avaliação fisiológica e molecular." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/88026.

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Na natureza, os sulfetos minerais constituem a principal fonte para extração industrial de metais, como o cobre, o chumbo, o zinco e o níquel. A calcopirita (CuFeS2) é um sulfeto de cobre importante, sendo o mineral de cobre mais abundante na natureza. Dentre os processos utilizados para a extração de metais está a biolixiviação, que consiste no processamento de minérios utilizando-se micro-organismos, e é reconhecida hoje como uma metodologia interessante sob os pontos de vista econômico e ambiental. Neste contexto, este trabalho foi desenvolvido com o objetivo de se obter consórcios oxidantes de ferro e de enxofre capazes de promover a solubilização da calcopirita. Para obtenção dos consórcios, quinze amostras minerais fornecidas pela Companhia Vale S.A. foram enriquecidas em meios de cultivo específicos. Foram obtidos 4 consórcios oxidantes de ferro e 4 oxidantes de enxofre, denominados Dep SOS-4, S3A, SO3, D1. A análise dessas amostras minerais por difração de raios X evidenciou a presença predominante de quartzo (SiO2) nas amostras Dep SOS-4 e S3A e nas amostras D1 e SO3 também foi observado covelita (CuS), pirrotita (FeS), calcopirita (CuFeS2) e enxofre (S0). Os consórcios oxidantes de ferro foram adaptados ao crescimento em calcopirita e submetidos a ensaios de biolixiviação em calcopirita. Agrupamentos dos consórcios também foram realizados, porém sem adaptação prévia à calcopirita. Nos ensaios de biolixiviação, os valores de Eh se elevaram continuamente nos frascos inoculados, estabilizando ao redor de 550 mV, indicando o aumento da relação Fe3+/Fe2+, o que afeta diretamente a solubilização dos metais pela ação oxidante do Fe3+. Mesmo considerando que a calcopirita é um dos sulfetos mais refratários ao ataque oxidante, bacteriano ou químico, a extração de cobre nos ensaios...
In nature, sulphide minerals are the main sources for extraction of some metals for industrial uses, such as copper, lead, zinc and nickel. One of the most important and explored copper sulphide is chalcopyrite, being the most abundant copper mineral in nature. Metals can be extracted using microorganisms, leading the bioleaching to an economic and environmentally sustainable process. In this research, it was developed different iron and sulfur oxidizer consortium to promote chalcopyrite (CuFeS2) solubilization. All consortium were obtained from previous enrichment in a specific culture of 15 ore samples provided by Companhia Vale S.A. Four iron oxidizer and four sulfur oxidizer consortium were prepared, and named Dep SOS-4, S3A, SO3 and D1. X ray diffraction of the Dep SOS-4 and S3A samples showed mainly quartz content (SiO2), whereas the SO3 and D1 samples showed covellite (CuS), pyrrothite (FeS), chalcopyrite (CuFeS2) and sulfur (S0) presence too. The iron oxidizer consortium were adapted to grow with chalcopyrite and then used in shake flasks experiments with chalcopyrite. A mix of consortiums was performed, but without a previous adaptation to the chalcopyrite. The Eh values increased during the bioleaching of the inoculated flasks, stabilizing around 550 mV, which affects metal solubilization due to an increase in the Fe+3/Fe+2 ratio. The iron oxidizer consortium resulted in a better dissolution of the chalcopyrite when compare with the control, sulfur oxidizer consortium and pure strain At. thiooxidans - FG01. However, it was not observed any significant difference between the consortium and At. ferrooxidans - LR in the chalcopyrite dissolution. In the respirometric tests with chalcopyrite as substrate were observed lower consumption of oxygen to the iron oxidizer consortium (Dep SOS -4, S3A, SO3 and D1) in relation to... (Complete abstract click electronic access below)

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Garcia, Íris Gabriela. "Consórcios microbianos associados a ambientes de minas : obtenção, avaliação fisiológica e molecular /." Araraquara, 2013. http://hdl.handle.net/11449/88026.

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Orientador: Denise Bevilaqua
Banca: Ana Teresa Lombardi
Banca: Monica Cristina Teixeira
Resumo: Na natureza, os sulfetos minerais constituem a principal fonte para extração industrial de metais, como o cobre, o chumbo, o zinco e o níquel. A calcopirita (CuFeS2) é um sulfeto de cobre importante, sendo o mineral de cobre mais abundante na natureza. Dentre os processos utilizados para a extração de metais está a biolixiviação, que consiste no processamento de minérios utilizando-se micro-organismos, e é reconhecida hoje como uma metodologia interessante sob os pontos de vista econômico e ambiental. Neste contexto, este trabalho foi desenvolvido com o objetivo de se obter consórcios oxidantes de ferro e de enxofre capazes de promover a solubilização da calcopirita. Para obtenção dos consórcios, quinze amostras minerais fornecidas pela Companhia Vale S.A. foram enriquecidas em meios de cultivo específicos. Foram obtidos 4 consórcios oxidantes de ferro e 4 oxidantes de enxofre, denominados Dep SOS-4, S3A, SO3, D1. A análise dessas amostras minerais por difração de raios X evidenciou a presença predominante de quartzo (SiO2) nas amostras Dep SOS-4 e S3A e nas amostras D1 e SO3 também foi observado covelita (CuS), pirrotita (FeS), calcopirita (CuFeS2) e enxofre (S0). Os consórcios oxidantes de ferro foram adaptados ao crescimento em calcopirita e submetidos a ensaios de biolixiviação em calcopirita. Agrupamentos dos consórcios também foram realizados, porém sem adaptação prévia à calcopirita. Nos ensaios de biolixiviação, os valores de Eh se elevaram continuamente nos frascos inoculados, estabilizando ao redor de 550 mV, indicando o aumento da relação Fe3+/Fe2+, o que afeta diretamente a solubilização dos metais pela ação oxidante do Fe3+. Mesmo considerando que a calcopirita é um dos sulfetos mais refratários ao ataque oxidante, bacteriano ou químico, a extração de cobre nos ensaios... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In nature, sulphide minerals are the main sources for extraction of some metals for industrial uses, such as copper, lead, zinc and nickel. One of the most important and explored copper sulphide is chalcopyrite, being the most abundant copper mineral in nature. Metals can be extracted using microorganisms, leading the bioleaching to an economic and environmentally sustainable process. In this research, it was developed different iron and sulfur oxidizer consortium to promote chalcopyrite (CuFeS2) solubilization. All consortium were obtained from previous enrichment in a specific culture of 15 ore samples provided by Companhia Vale S.A. Four iron oxidizer and four sulfur oxidizer consortium were prepared, and named Dep SOS-4, S3A, SO3 and D1. X ray diffraction of the Dep SOS-4 and S3A samples showed mainly quartz content (SiO2), whereas the SO3 and D1 samples showed covellite (CuS), pyrrothite (FeS), chalcopyrite (CuFeS2) and sulfur (S0) presence too. The iron oxidizer consortium were adapted to grow with chalcopyrite and then used in shake flasks experiments with chalcopyrite. A mix of consortiums was performed, but without a previous adaptation to the chalcopyrite. The Eh values increased during the bioleaching of the inoculated flasks, stabilizing around 550 mV, which affects metal solubilization due to an increase in the Fe+3/Fe+2 ratio. The iron oxidizer consortium resulted in a better dissolution of the chalcopyrite when compare with the control, sulfur oxidizer consortium and pure strain At. thiooxidans - FG01. However, it was not observed any significant difference between the consortium and At. ferrooxidans - LR in the chalcopyrite dissolution. In the respirometric tests with chalcopyrite as substrate were observed lower consumption of oxygen to the iron oxidizer consortium (Dep SOS -4, S3A, SO3 and D1) in relation to... (Complete abstract click electronic access below)
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6

Coram, Nicolette Joanne. "Molecular characterization of iron-oxidizing Leptospirillum strains from around the world." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52944.

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Dissertation (PhD) -- University of Stellenbosch, 2002.
ENGLISH ABSTRACT: More than sixteen isolates of iron-oxidizing bacteria belonging to the genus Leptospirillum were included in this study, with the finding that they were clearly divisible into two major groups. Group I leptospirilla had mol% G+C ratios within the range 49-52%, three copies of rrn genes and based on 16S rRNA sequence data, clustered together with the Leptospirillum ferrooxidans type strain (DSM2705or LI5). Group II leptospirilla had mol% G+C ratios of 55-58%, two copies of rrn genes and based on 16S rRNA sequence form a separate cluster. Genome DNA-DNA hybridization experiments indicated that three similarity subgroups were present amongst the leptospirilla tested with two DNA-DNA hybridization similarity subgroups being found within group I. The two groups could also be distinguished based on the sizes of their 16S-23SrRNA gene spacer regions. We propose that the group II leptospirilla should be recognized as a new species with the name Leptospirillum ferriphilum sp. nov. Members of the two species can be rapidly distinguished from each other by amplification of their 16S rRNA genes and carrying out restriction enzyme digests of the products. Several but not all isolates of the group II leptospirilla, but none from group I (L. ferrooxidans) were capable of growth at 45°C. Plasmid DNA was isolated from strain ATCC49879 (L. ferrooxidans). Restriction endonuclease mapping of what appeared to be about 60 kb of plasmid DNA, established that two plasmids of approximately 30.0 kb and 27.0 kb were present. These were named p49879.1 and p49879.2 respectively. Attempts to isolate the plasmids separately were not successful. Partial sequencing of the two plasmids was carried out and sequence analysis of p49879.1 and p49879.2 indicated that the plasmids shared regions of homology. Total plasmid DNA was DIG-labelled and used as a probe in Southern hybridization experiments with genomic DNA from all sixteen original leptospirilla isolates as the target DNA. All leptospirilla belonging to Group I gave a positive signal, little or no homology to Group II leptospirilla was obtained. The region of homology present in all L. ferrooxidans strains was localized to an area on plasmid p49879.2 showing high amino acid identity to a transposase/putative transposase of Methanosarcina acetivorans and plasmid CPl from Deinococcus radiodurans Rl respectively. Whether these regions of homology indicate that complete, functional transposons are present in all L. ferrooxidans isolates still remains to be determined. Preliminary sequence analysis of both plasmids resulted in the identification of regions with amino acid sequence identity to the TnpA and TnpR of the Tn2l-like transposon family, and the mobilization regions of IncQ-like plasmids (particularly that of pTFl from At. ferrooxidans). Another potentially interesting ORF was identified in p49879.2 with high amino acid sequence identity to an ArsR-like protein that belongs to a second atypical family of ArsR transcriptional regulators. Whether this protein is functional in the regulation of arsenic resistance genes has not yet been determined, nor have other arsenic resistance genes been identified. Future work includes further sequence analysis of these plasmids to better understand their contribution to the isolates in which they are found.
AFRIKAANSE OPSOMMING: Meer as sestien isolate van die yster-oksiderende bakterieë, wat aan die genus Leptospirillum behoort, is in die studie ingesluit en die resultate het getoon dat dié groep verder in twee hoof groepe verdeel kan word. Groep I het "n mol% G+C van tussen 49% en 52% gehad, sowel as drie kopieë van die ribosomale gene (rrn). Hiermeesaam het die 16SrRNA volgorde data getoon dat hierdie isolate groepeer saam met Leptospirillum ferrooxidans (DSM2705T en LI5). Groep II leptospirilla het "n mol% G+C van tussen 55% en 58% gehad sowel as twee kopieë van die rrn gene en saam met die 16SrRNA volgorde data het hierdie isolate "n aparte groep gevorm. Genoom DNA-DNA hibridisasie eksperimente het gewys dat daar drie subgroepe onder die Leptospirillum wat getoets was is, met twee naverwante groepe wat onder Groep I val. Daar kan ook tussen die twee hoof groepe onderskei word op grond van die grootte van hul 16S- 23SrRNA intergeniese gebiede. Ons stel dus hier voor dat die Groep II leptospirilla as "n nuwe spesie beskou word naamlik, Leptospirillum ferriphilum sp, nov. Die twee spesies kan maklik onderskei word deur die PKR amplifikasie produk van die 16SrRNA te verteer met restriksie ensieme. Vele, maar nie al van die Groep II isolate kan by 45°C groei nie, terwyl geen van die Groep I leptospirilla (L.ferrooxidans) kan nie. Plasmied DNA was geisoleer uit Leptospirillum ferrooxidans ATCC49879. Aanvanklike analise het gedui op die teenwoordigheid van een 60.0 kb plasmied. Verdere restriksie ensiem kartering het wel getoon dat hierdie, in teen deel, twee plasmiede van ongeveer 30.0 kb en 27.0 kb in grootte is: p49879.1 en p49879.2. Pogings om die twee plasmiede apart te isoleer was onsuksesvol. Totale plasmied DNA is gemerk met die Random primed DNA labelling kit (Roche diagnostics) en gebruik as peiler in Southern klad eksperimente met genoom DNA, van al sestien isolate, as teiken. Alle leptospirilla wat aan Groep I behoort het "n positiewe sein gegee terwyl geen sein teen Groep II DNA opgemerk was nie. Die area wat, tussen die plasmiede en Groep I homologie getoon het, is gelokaliseer tot "n area op plasmied p49879.2 wat hoë amino suur identiteit toon aan "n transposase geen van Methanosarcina acetivorans, en "n voorgestelde transposase geen op plasmied CPI van Deinococcus radiodurans Rl. Dit moet nog vasgestel word of hierdie area van homologie dui op die teenwoordigheid van "n volledige, funksionele transposon in alle L. ferrooxidans isolate. Gedeeltelike DNA volgorde bepalings van beide plasmiede het gelei tot die identifikasie van areas met hoë amino suur volgorde identiteit aan die TnpA en TnpR gene van die Tn21-tipe transposon familie, sowel as aan die mobilisasie gene van IncQsoortige plasmiede (veral die van pTFI uit Acidithiobacillus ferrooxidans). "n Oop lees raam van belang, wat op plasmied p49879.2 geidentifiseer was, het hoë amino suur volgorde identiteit aan "n ArsR-tipe geen getoon wat aan "n tweede atiepiese familie van ArsR transkripsionele reguleerders behoort. Op die stadium is dit nog onbekend of hierdie protein funksioneel is in die regulering van arseen weerstandbiedenheidsgene.

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Tasa, Andrus. "Biological leaching of shales : black shale and oil shale /." Tartu : Tartu University Press, 1998. http://bibpurl.oclc.org/web/24619.

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Togamana, Culwick. "The evaluation of the stability of metalliferrous tailings by chemical and microbiological leaching." Thesis, University of Exeter, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388592.

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Chapman, J. T. "The batch and continuous bacterial leaching kinetics of a refractory gold-bearing pyrite concentrate." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/17706.

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Bibliography: pages 125-136.
The recent focus on bacterial leaching as a preoxidation step in the treatment of refractory gold bearing sulphide ores and concentrates, has created the need for kinetic models to adequately describe bacterial leaching reactor performance. This work is a kinetic study of the bacterial leaching of a refractory gold bearing, pyrite concentrate. The study includes the presentation of two mechanistically based, the shrinking particle and propagating pore (Hansford and Drossou, 1986), batch reactor kinetic models. These models are derived for single stage continuous reactor description. In addition, the empirical logistic growth model (Pinches et al., 1987) is presented for both batch and continuous reactor description. The models are correlated with the experimental data. Three narrow size fractions of the pyrite concentrate were subjected to batch and continuous bacterial oxidation, using a Thiobacillus ferrooxidans culture. Time profile data of the pyrite oxidation were obtained for the batch reactor study. Similarly, retention time profile data of pyrite oxidation was obtained for the single stage continuous reactor. The .gold extraction as a function of sulphide oxidation as well as fraction arsenic leached, was established.

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Francisco, Junior Wilmo Ernesto [UNESP]. "Estudo da oxidação de covelita (CuS) e molibdenita (MoS2) sintéticas por Acidithiobacillus ferrooxidans." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/88034.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A lixiviação bacteriana, ou biolixiviação é um processo biotecnológico que se fundamenta na utilização de microorganismos capazes de solubilizar metais pela oxidação de sulfetos metálicos, sendo nos dias atuais, uma das mais importantes alternativas para a extração de metais, sobretudo do ponto de vista ambiental e econômico. Uma das principais espécies utilizada neste processo é o Acidithiobacillus ferrooxidans, uma bactéria aeróbia, mesofílica e acidofílica, que obtém energia pela oxidação de substratos inorgânicos, basicamente o íon ferroso e compostos reduzidos de enxofre. Todavia, a interação dessa espécie com os sulfetos metálicos é um assunto ainda pouco entendido e de muita controvérsia na literatura. Com intuito de melhor entender estas diferenças, o presente trabalho estudou a oxidação da molibdenita (MoS2) e da covelita (CuS) pelo A. ferrooxidans linhagem LR em algumas condições fisiológicas, destacando-se a fonte energética de crescimento (íon ferroso e S0) e a remoção das substâncias exopoliméricas (EPS) para células crescidas em íon ferroso. A cinética de oxidação destes sulfetos também foi avaliada. Tais estudos foram realizados pela técnica de respirometria celular, que permite avaliar rapidamente a oxidação do substrato a partir de medidas de oxigênio consumido pela bactéria. Em todas as condições testadas a covelita apresentou significativa diferença de oxidação pelo A. ferroxidans LR em comparação com a molibdenita. A análise da cinética de oxidação dos sulfetos demonstrou que a molibdenita apresenta uma cinética que segue Michaelis-Menten, o mesmo não acontecendo para a covelita, provavelmente devido a forma com que estes sulfetos reagem ao ataque químico-bacteriano, fato determinado pelas estruturas eletrônicas dos sulfetos minerais.
Bacterial leaching or bioleaching is a biotechnological process that applies microorganisms able to solubilize metals by metallic sulfides oxidation. This process is nowadays one of the most important alternatives for recovering metals, mainly by environmental and economic aspects. One of the most important bacteria employed in this process is Acidithiobacillus ferrooxidans. It is a gram-negative, acidophilic, aerobic and chemoautotrophic bacteria that obtain energy by the oxidation of inorganic substrates like ferrous ion and reduced sulfur compounds, including metal sulfides. Nevertheless, the interaction of this specie with metallic sulfides remains unclear. With the aim to understand these interactions, the present work has studied the covellite (CuS) and molydenite (MoS2) oxidation by A. ferrooxidans strain LR under different physiological conditions such as the source energy for growth (S0 and ferrous ion) and the removal of extracellular polymeric substances (EPS). These studies were performed by respirometric technique tha t allow evaluating very quickly the substrate oxidation by oxygen uptake measures. For all essays realized it was observed that the efficiency of covellite oxidation by A. ferrooxidans LR is much better than molybdenite. On the kinetic oxidation analyses, molybdenite revealed to be according to Michaelis-Menten substrate saturate kinetic. On the other hand, covellite was not in agreement with Michalis-Menten kinetic. This finding is probably associated with the pathway which these minerals sulfide react to chemistry-bacterial attack, what is influenced by electronic structures of mineral sulfides. Regarding essays performed with cells of A. ferrooxidans strain LR grown with different substrates (ferrous ion and sulfur) and to essays which EPS of bacterial cells were removed, the results obtained did not show differences in covellite oxidation.

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Sampson, Mark Ian. "Influence of the cell properties of acidophilic bacteria during attachment to mineral sulfides and consumption during the oxidation of ferrous iron." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297789.

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Ewart, D. Keith. "Studies on a moderately thermophilic mixed culture of bacteria and its application to the biooxidation of gold-bearing minerals." Thesis, King's College London (University of London), 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389882.

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Norman, Philippa Fernandes. "An Investigation into the bacterial leaching of a gold-bearing pyrite/arsenopyrite ore." Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/21903.

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Bibliography : pages 157-173.
The main aim of this study was to develop an economically viable bacterial leaching process for a gold-containing pyrite/arsenopyrite ore. The effect of various parameters on, and the mechanism of, bacterial leaching were investigated. Initially milled run-of-mine ore was examined. Batch tests and a continuous bacterial leach were carried out. Bacterial leaching was successful and 91-93% gold dissolution was attained in four days. The process was not economically feasible when compared to the standard flotation-roasting process.

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Santos, Ana Laura Araújo [UNESP]. "Efeito do potencial de óxido-redução na biolixiviação da calcopirita." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/110371.

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As fontes naturais de minérios sulfetados vêm se esgotando rapidamente devido à demanda por metais nas indústrias de bens de produção e de consumo. O cobre é um dos metais de maior interesse econômico. Cerca de 70% deste metal é encontrado na natureza na forma de calcopirita (CuFeS2), contudo é o mineral que possui maiores limitações em sua extração. Dentre os processos de extração têm-se a biolixiviação, que utiliza micro-organismos capazes de promoverem a solubilização de metais pela oxidação de sulfetos metálicos, apresentando vantagens em relação às técnicas já utilizadas, principalmente de cunho econômico e ambiental. Neste contexto, o presente trabalho foi desenvolvido com o objetivo de avaliar a influência do potencial de óxido-redução na solubilização de cobre a partir da calcopirita. Para isso, foram realizados ensaios de oxidação de íons ferrosos na presença e ausência do mineral. A bactéria utilizada nos ensaios foi a Acidithiobacillus ferrooxidans - LR, espécie acidófila mais estudada e mais encontrada em ambientes de mina. A amostra de calcopirita, proveniente da localidade de La Chorrera, na Colômbia, foi analisada por difração de raios-X (DRX) e evidenciou a presença dominante de calcopirita. Os ensaios de oxidação foram realizados em frascos, agitados a 150 rpm, a 30ºC sob diferentes concentrações de íons ferrosos (100, 200 e 300 mmol L-1) em meio T&K. Aos sistemas foram adicionados 2,5% (m/v) de calcopirita e 5% (v/v) do inóculo fresco de A. ferrooxidans. Nas condições abióticas, em todas as concentrações de Fe2+, o potencial redox atingiu, em média, 420 mV (Ag|AgCl|KCl(sat)), e foram os sistemas que apresentaram as maiores porcentagens de recuperação de cobre, sendo elas 73%, 90% e 78%, respectivamente, após 100 dias de ensaio. Contudo, os sistemas que continham bactéria apresentaram uma recuperação ínfima de cobre, chegando a apenas 17%, em um potencial médio...
Natural sources of sulfide ores come depleting rapidly due to the demand for metal goods industries in production and consumption. Copper is a metal of greater economic interest. About 70% of this metal is found in nature in the form of chalcopyrite (CuFeS2), however it is the mineral that present a major limitations in its extraction. One of the extraction processes is bioleaching, which uses microorganisms capable of promoting the solubilization of metals by metal sulfides oxidation and presents advantages over the common techniques used, mainly for economic and environmental nature. In this context, the present work was carrying out to evaluate the influence of the redox potential in the solubilization of copper from chalcopyrite. For this, ferrous ions oxidation tests were conducted in the presence and absence of the mineral. The bacterium used in the tests was Acidithiobacillus ferrooxidans - LR, the acidophilic species most studied and most commonly found in mine environments. A sample of chalcopyrite from La Chorrera, Colombia, was analyzed by X-ray diffraction (XRD) and showed the dominant presence of chalcopyrite. Ferrous ions oxidation tests were carried out in shaken flasks at 150 rpm, at 30 ºC using different concentrations of ferrous ions (100, 200, and 300 mmol L-1) in T&K medium. The systems were supplied with 2,5% (w/v) of chalcopyrite and 5% (v/v) of A. ferrooxidans fresh inoculum. At the abiotic conditions, the redox potential achieved 420 mV (Ag|AgCl|KCl(sat)) in all ferrous ions concentrations. Besides, these systems showed the highest copper recovery concentrations, such 73%, 90% and 78%, respectively, after 100 days of testing. However, the bacterial systems showed a low copper recovery, about 17% in a redox potential of 610 mV (Ag|AgCl|KCl(sat)). The solid residues were evaluated by XRD and showed, at abiotic conditions the formation of elemental sulfur, jarositas and a significant decrease in chalcopyrite’s...

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Santos, Ana Laura Araújo. "Efeito do potencial de óxido-redução na biolixiviação da calcopirita /." Araraquara, 2014. http://hdl.handle.net/11449/110371.

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Orientador: Denise Bevilaqua
Banca: Assis Vicente Benedetti
Banca: Paulo Teixeira Lacava
Resumo: As fontes naturais de minérios sulfetados vêm se esgotando rapidamente devido à demanda por metais nas indústrias de bens de produção e de consumo. O cobre é um dos metais de maior interesse econômico. Cerca de 70% deste metal é encontrado na natureza na forma de calcopirita (CuFeS2), contudo é o mineral que possui maiores limitações em sua extração. Dentre os processos de extração têm-se a biolixiviação, que utiliza micro-organismos capazes de promoverem a solubilização de metais pela oxidação de sulfetos metálicos, apresentando vantagens em relação às técnicas já utilizadas, principalmente de cunho econômico e ambiental. Neste contexto, o presente trabalho foi desenvolvido com o objetivo de avaliar a influência do potencial de óxido-redução na solubilização de cobre a partir da calcopirita. Para isso, foram realizados ensaios de oxidação de íons ferrosos na presença e ausência do mineral. A bactéria utilizada nos ensaios foi a Acidithiobacillus ferrooxidans - LR, espécie acidófila mais estudada e mais encontrada em ambientes de mina. A amostra de calcopirita, proveniente da localidade de La Chorrera, na Colômbia, foi analisada por difração de raios-X (DRX) e evidenciou a presença dominante de calcopirita. Os ensaios de oxidação foram realizados em frascos, agitados a 150 rpm, a 30ºC sob diferentes concentrações de íons ferrosos (100, 200 e 300 mmol L-1) em meio T&K. Aos sistemas foram adicionados 2,5% (m/v) de calcopirita e 5% (v/v) do inóculo fresco de A. ferrooxidans. Nas condições abióticas, em todas as concentrações de Fe2+, o potencial redox atingiu, em média, 420 mV (Ag|AgCl|KCl(sat)), e foram os sistemas que apresentaram as maiores porcentagens de recuperação de cobre, sendo elas 73%, 90% e 78%, respectivamente, após 100 dias de ensaio. Contudo, os sistemas que continham bactéria apresentaram uma recuperação ínfima de cobre, chegando a apenas 17%, em um potencial médio...
Abstract: Natural sources of sulfide ores come depleting rapidly due to the demand for metal goods industries in production and consumption. Copper is a metal of greater economic interest. About 70% of this metal is found in nature in the form of chalcopyrite (CuFeS2), however it is the mineral that present a major limitations in its extraction. One of the extraction processes is bioleaching, which uses microorganisms capable of promoting the solubilization of metals by metal sulfides oxidation and presents advantages over the common techniques used, mainly for economic and environmental nature. In this context, the present work was carrying out to evaluate the influence of the redox potential in the solubilization of copper from chalcopyrite. For this, ferrous ions oxidation tests were conducted in the presence and absence of the mineral. The bacterium used in the tests was Acidithiobacillus ferrooxidans - LR, the acidophilic species most studied and most commonly found in mine environments. A sample of chalcopyrite from La Chorrera, Colombia, was analyzed by X-ray diffraction (XRD) and showed the dominant presence of chalcopyrite. Ferrous ions oxidation tests were carried out in shaken flasks at 150 rpm, at 30 ºC using different concentrations of ferrous ions (100, 200, and 300 mmol L-1) in T&K medium. The systems were supplied with 2,5% (w/v) of chalcopyrite and 5% (v/v) of A. ferrooxidans fresh inoculum. At the abiotic conditions, the redox potential achieved 420 mV (Ag|AgCl|KCl(sat)) in all ferrous ions concentrations. Besides, these systems showed the highest copper recovery concentrations, such 73%, 90% and 78%, respectively, after 100 days of testing. However, the bacterial systems showed a low copper recovery, about 17% in a redox potential of 610 mV (Ag|AgCl|KCl(sat)). The solid residues were evaluated by XRD and showed, at abiotic conditions the formation of elemental sulfur, jarositas and a significant decrease in chalcopyrite's...
Mestre

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Mikkelsen, Deirdre. "The development and use of molecular phylogenetic and microscopy methods to study thermophilic bioleaching cultures /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18580.pdf.

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Francisco, Junior Wilmo Ernesto. "Estudo da oxidação de covelita (CuS) e molibdenita (MoS2) sintéticas por Acidithiobacillus ferrooxidans /." Araraquara : [s.n.], 2006. http://hdl.handle.net/11449/88034.

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Resumo: A lixiviação bacteriana, ou biolixiviação é um processo biotecnológico que se fundamenta na utilização de microorganismos capazes de solubilizar metais pela oxidação de sulfetos metálicos, sendo nos dias atuais, uma das mais importantes alternativas para a extração de metais, sobretudo do ponto de vista ambiental e econômico. Uma das principais espécies utilizada neste processo é o Acidithiobacillus ferrooxidans, uma bactéria aeróbia, mesofílica e acidofílica, que obtém energia pela oxidação de substratos inorgânicos, basicamente o íon ferroso e compostos reduzidos de enxofre. Todavia, a interação dessa espécie com os sulfetos metálicos é um assunto ainda pouco entendido e de muita controvérsia na literatura. Com intuito de melhor entender estas diferenças, o presente trabalho estudou a oxidação da molibdenita (MoS2) e da covelita (CuS) pelo A. ferrooxidans linhagem LR em algumas condições fisiológicas, destacando-se a fonte energética de crescimento (íon ferroso e S0) e a remoção das substâncias exopoliméricas (EPS) para células crescidas em íon ferroso. A cinética de oxidação destes sulfetos também foi avaliada. Tais estudos foram realizados pela técnica de respirometria celular, que permite avaliar rapidamente a oxidação do substrato a partir de medidas de oxigênio consumido pela bactéria. Em todas as condições testadas a covelita apresentou significativa diferença de oxidação pelo A. ferroxidans LR em comparação com a molibdenita. A análise da cinética de oxidação dos sulfetos demonstrou que a molibdenita apresenta uma cinética que segue Michaelis-Menten, o mesmo não acontecendo para a covelita, provavelmente devido a forma com que estes sulfetos reagem ao ataque químico-bacteriano, fato determinado pelas estruturas eletrônicas dos sulfetos minerais.
Abstract: Bacterial leaching or bioleaching is a biotechnological process that applies microorganisms able to solubilize metals by metallic sulfides oxidation. This process is nowadays one of the most important alternatives for recovering metals, mainly by environmental and economic aspects. One of the most important bacteria employed in this process is Acidithiobacillus ferrooxidans. It is a gram-negative, acidophilic, aerobic and chemoautotrophic bacteria that obtain energy by the oxidation of inorganic substrates like ferrous ion and reduced sulfur compounds, including metal sulfides. Nevertheless, the interaction of this specie with metallic sulfides remains unclear. With the aim to understand these interactions, the present work has studied the covellite (CuS) and molydenite (MoS2) oxidation by A. ferrooxidans strain LR under different physiological conditions such as the source energy for growth (S0 and ferrous ion) and the removal of extracellular polymeric substances (EPS). These studies were performed by respirometric technique tha t allow evaluating very quickly the substrate oxidation by oxygen uptake measures. For all essays realized it was observed that the efficiency of covellite oxidation by A. ferrooxidans LR is much better than molybdenite. On the kinetic oxidation analyses, molybdenite revealed to be according to Michaelis-Menten substrate saturate kinetic. On the other hand, covellite was not in agreement with Michalis-Menten kinetic. This finding is probably associated with the pathway which these minerals sulfide react to chemistry-bacterial attack, what is influenced by electronic structures of mineral sulfides. Regarding essays performed with cells of A. ferrooxidans strain LR grown with different substrates (ferrous ion and sulfur) and to essays which EPS of bacterial cells were removed, the results obtained did not show differences in covellite oxidation.
Orientador: Oswaldo Garcia Júnior
Coorientador: Denise Bevilaqua
Banca: Assis Vicente Benedetti
Banca: Fernanda de Castro Reis
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Chukwuchendo, Emmanuel Chukwunonso. "Bio-oxidation of ferrous iron at low temperature conditions in a packed bed column bioreactors." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2545.

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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.
The oxidation of microbial ferrous iron is an important sub-process in the bioleaching process. Several studies focussing on microbial ferrous iron oxidation have been investigated and reported in various studies. These studies were carried out using stirred tank bioreactors and shake flasks at optimum conditions. However, these studies could not describe the context of heap bioleach system. Packed column system may describe heap bioleaching, and most studies on microbial ferrous iron oxidation were performed under flooded conditions, which do not represent solution flow dynamics in a heap situation. Biooxidation of ferrous iron oxidation kinetics of Acidiobacillus ferrooxidans was studied in a packed-bed bioreactor to investigate the kinetics in a system that mimics the solution flow dynamic of a heap bioleach operation at low-temperature conditions. This was done in a batch mode operation, with glass marble (15 mm) as reactor packing. The pH of the bioreactor was maintained at pH 1.35 ± 0.05 and aeration at 500 ml/min. Unstructured models known as Monod and Hansford were used to describe the experimental data in determining the kinetics of bio-oxidation.

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Jiang, Shuang. "Bacterial leaching from dairy shed effluent applied to a fine sandy loam under flood and spray irrigations." Lincoln University, 2008. http://hdl.handle.net/10182/668.

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Land application of wastes has become increasingly popular, to promote nutrient recycling and environmental protection, with soil functioning as a partial barrier between wastes and groundwater. Dairy shed effluent (DSE), may contain a wide variety of pathogenic micro-organisms, including bacteria (e.g. Salmonella paratyphyi, Escherichia coli. and Campylobacter), protozoa and viruses. Groundwater pathogen contamination resulting from land-applied DSE is drawing more attention with the intensified development of the dairy farm industry in New Zealand. The purpose of this research was to investigate the fate and transport of bacterial indicator-faecal coliform (FC) from land-applied DSE under different irrigation practices via field lysimeter studies, using two water irrigation methods (flood and sprinkler) with contrasting application rates, through the 2005-2006 irrigation season. It was aimed at better understanding, quantifying and modelling of the processes that govern the removal of microbes in intact soil columns, bridging the gap between previous theoretical research and general farm practices, specifically for Templeton soil. This study involved different approaches (leaching experiments, infiltrometer measurements and a dye infiltration study) to understand the processes of transient water flow and bacterial transport; and to extrapolate the relationships between bacterial transport and soil properties (like soil structure, texture), and soil physical status (soil water potential ψ and volumetric water content θ). Factors controlling FC transport are discussed. A contaminant transport model, HYDRUS-1D, was applied to simulate microbial transport through soil on the basis of measured datasets. This study was carried out at Lincoln University’s Centre for Soil and Environmental Quality (CSEQ) lysimeter site. Six lysimeters were employed in two trials. Each trial involved application of DSE, followed by a water irrigation sequence applied in a flux-controlled method. The soil columns were taken from the site of the new Lincoln University Dairy Farm, Lincoln, Canterbury. The soil type is Templeton fine sandy loam (Udic-Ustochrept, coarse loamy, mixed, mesic). Vertical profiles (at four depths) of θ and ψ were measured during leaching experiments. The leaching experiments directly measured concentrations of chemical tracer (Br⁻ or Cl⁻) and FC in drainage. Results showed that bacteria could readily penetrate through 700 mm deep soil columns, when facilitated by water flow. In the first (summer) trial, FC in leachate as high as 1.4×10⁶ cfu 100 mL⁻¹ (similar to the DSE concentration), was detected in one lysimeter that had a higher clay content in the topsoil, immediately after DSE application, and before any water irrigation. This indicates that DSE flowed through preferential flow paths without significant treatment or reduction in concentrations. The highest post-irrigation concentration was 3.4×10³ cfu 100 mL⁻¹ under flood irrigation. Flood irrigation resulted in more bacteria and Br⁻ leaching than spray irrigation. In both trials (summer and autumn) results showed significant differences between irrigation treatments in lysimeters sharing similar drainage class (moderate or moderately rapid). Leaching bacterial concentration was positively correlated with both θ and ψ, and sometimes drainage rate. Greater bacterial leaching was found in the one lysimeter with rapid whole-column effective hydraulic conductivity, Keff, for both flood and spray treatments. Occasionally, the effect of Keff on water movement and bacterial transport overrode the effect of irrigation. The ‘seasonal condition’ of the soil (including variation in initial water content) also influenced bacterial leaching, with less risk of leaching in autumn than in summer. A tension infiltrometer experiment measured hydraulic conductivity of the lysimeters at zero and 40 mm suction. The results showed in most cases a significant correlation between the proportion of bacteria leached and the flow contribution of the macropores. The higher the Ksat, the greater the amount of drainage and bacterial leaching obtained. This research also found that this technique may exclude the activity of some continuous macropores (e.g., cracks) due to the difference of initial wetness which could substantially change the conductivity and result in more serious bacterial leaching in this Templeton soil. A dye infiltration study showed there was great variability in water flow patterns, and most of the flow reaching deeper than 50 cm resulted from macropores, mainly visible cracks. The transient water flow and transport of tracer (Br⁻) and FC were modelled using the HYDRUS-1D software package. The uniform flow van Genuchten model, and the dual-porosity model were used for water flow and the mobile-immobile (MIM) model was used for tracer and FC transport. The hydraulic and solute parameters were optimized during simulation, on the basis of measured datasets from the leaching experiments. There was evidence supporting the presence of macropores, based on the water flow in the post-DSE application stage. The optimised saturated water content (θs) decreased during the post-application process, which could be explained in terms of macropore flow enhanced by irrigation. Moreover, bacterial simulation showed discrepancies in all cases of uniform flow simulations at the very initial stage, indicating that non-equilibrium processes were dominant during those short periods, and suggesting that there were strong dynamic processes involving structure change and subsequently flow paths. It is recommended that management strategies to reduce FC contamination following application of DSE in these soils must aim to decrease preferential flow by adjusting irrigation schemes. Attention needs to be given to a) decreasing irrigation rates at the beginning of each irrigation; b) increasing the number of irrigations, by reducing at the same time the amount of water applied and the irrigation rate at each irrigation; c) applying spray irrigation rather than flood irrigation.

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Harahuc, Lesia. "Control of iron and sulfur oxidation activities of Thiobacillus ferrooxidans and bacterial leaching of metals from sulfide ores." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0027/NQ51648.pdf.

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Mabusela, Bongolwethu Professor. "The effect of initial pH on surface properties of ferric ion precipitates formed during microbial oxidation of ferrous ion by Leptospirillum ferriphilum in a CSTR." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2553.

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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.
While bioleaching is a proven technology for the efficient recovery of base metals from sulphide minerals, its sustenance is dependent on the continuous availability of ferric ion, Fe3+, in soluble form, in the bioleach liquor. However, the solubility of ferric ion is low at higher pH that it tends to precipitate, resulting in the formation of ferric ion precipitates. The formation of ferric ion precipitates in bio-hydrometallurgy decreases the leaching efficiency by trapping the leached metals in solution through an adsorption mechanism which is not well understood. Although the surface properties of the precipitate could be linked to its metal adsorption properties, there has not been a detailed study that gives any indication or explanation of the adsorption mechanism. Therefore, the aim of this study was to investigate the effect of initial pH on the surface properties of ferric ion precipitate and relate this to the adsorption characteristics of the precipitate for desired metals. Biooxidation experiments catalysed by Leptospirillum ferriphilum were conducted in a CSTR with a working volume of 1L. The biooxidation experiments were conducted at pH values of 1.3, 1.5, 1.7, 1.9 and 2.2 at a constant temperature of 35 0C for 14 days. The recovered precipitates were characterized by X-ray diffraction, elemental analyses, SEM, particle size distribution (PSD) and zeta potential. Zeta potential measurements were conducted to investigate what role initial pH plays in modifying the precipitate surface charge and what role the surface charge of each precipitate plays in the nature of adsorption of copper ions onto the precipitate surface. The amount of copper adsorbed onto the precipitate was quantified by the magnitude of the change in surface charge after adsorption experiments. Quantification results showed that the amount of ferric ions precipitates formed increased from 4.31g to 13.26g with an increase in initial pH (from 1.3 to 2.2). The results also showed that significant precipitation of ferric ion occurred during the exponential phase while insignificant precipitation was observed during the stationary phase.

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Chan, Lau Chi. "Bioleaching of heavy metals from anaerobically digested sewage sludge using isolated indigenous iron- and sulphur-oxidizing bacteria." HKBU Institutional Repository, 2001. http://repository.hkbu.edu.hk/etd_ra/279.

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Shashikala, A. R. "Role Of Interfacial Phenomena In Bioprocessing Of Minerals Using Bacillus Polymyxa." Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/246.

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In recent years there has been growing interest in bio-mineral processing due to its low operating costs and its application in processing lean-grade ores. Bioprocessing is a good alternative to conventional hydrometallurgy process in mineral processing. In recent times microorganisms have been used as surface modifiers in processes such as froth flotation and flocculation. The surface properties of microbes and minerals such as zeta potential and surface hydrophobicity play a major role in determining adhesion of microorganisms to minerals and hence, the efficiency of flocculation and flotation. These properties also depend on solution conditions such as pH and ionic strength. Adhesion of microorganisms to mineral surfaces can alter the surface properties of the minerals. Such surface modification imparting hydrophobicity or hydrophilicity is used in flocculation and flotation of fine particles. In this research work the effect of ionic strength and pH in deteraiining the surface properties and hence adhesion of the bacterium Bacillus polymyxa to minerals such as hematite, quartz and coal has been studied in detail. The effect of the ionic strength and pH on the electrokinetics of the minerals and bacteria and its subsequent effect on adhesion and flocculation were investigated in detail. Contact angle measurements along with the zeta potential results were used to calculate the interaction energies between the mineral and the microorganism to establish a mechanism for the interaction. The following major conclusions can be drawn from this study. Results indicate that increase in the ionic strength significantly changes the zeta potential of hematite and bacteria without varying the isoelectric point. Increase in the ionic strength caused very little change in the zeta potential of quartz and coal. The adhesion of bacterial cells on to the minerals was found to be dependent on pH, ionic strength and conditioning time. Adhesion of bacterial cells was found to be more on hematite and coal when compared to quartz. The adsorption isotherms of Bacillus polymyxa cells with respect to all the three minerals were found to obey Langmuir isotherm. Flocculation studies demonstrated that the settling rate of hematite and coal was enhanced in presence of bacterial cells and electrolyte. However quartz settled much slower under the same conditions indicating that the quartz particles are being dispersed. Thus, selective flocculation of hematite and coal is possible which can be used in separating them from quartz effectively. The different components of total interaction energy arising from Lifshitz-van der Waal forces, acid/base forces and electrostatic forces were calculated using the van Oss approach. Calculation of the components of the acid base free energy showed that coal and hematite were hydrophobic compared to quartz and the bacterium. From total interaction energy calculation based on the extended DLVO theory, hematite and coal were found to have a net negative interaction energy in acidic pH values and hence attractive forces are predominant. Quartz was found to have a net repulsive energy at all the pH values at low ionic strengths but increase in ionic strength the interaction energy become attractive. The AGLW values of quartz was found to be attractive which is probably responsible for bacterial adhesion onto quartz.

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Shashikala, A. R. "Role Of Interfacial Phenomena In Bioprocessing Of Minerals Using Bacillus Polymyxa." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/246.

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In recent years there has been growing interest in bio-mineral processing due to its low operating costs and its application in processing lean-grade ores. Bioprocessing is a good alternative to conventional hydrometallurgy process in mineral processing. In recent times microorganisms have been used as surface modifiers in processes such as froth flotation and flocculation. The surface properties of microbes and minerals such as zeta potential and surface hydrophobicity play a major role in determining adhesion of microorganisms to minerals and hence, the efficiency of flocculation and flotation. These properties also depend on solution conditions such as pH and ionic strength. Adhesion of microorganisms to mineral surfaces can alter the surface properties of the minerals. Such surface modification imparting hydrophobicity or hydrophilicity is used in flocculation and flotation of fine particles. In this research work the effect of ionic strength and pH in deteraiining the surface properties and hence adhesion of the bacterium Bacillus polymyxa to minerals such as hematite, quartz and coal has been studied in detail. The effect of the ionic strength and pH on the electrokinetics of the minerals and bacteria and its subsequent effect on adhesion and flocculation were investigated in detail. Contact angle measurements along with the zeta potential results were used to calculate the interaction energies between the mineral and the microorganism to establish a mechanism for the interaction. The following major conclusions can be drawn from this study. Results indicate that increase in the ionic strength significantly changes the zeta potential of hematite and bacteria without varying the isoelectric point. Increase in the ionic strength caused very little change in the zeta potential of quartz and coal. The adhesion of bacterial cells on to the minerals was found to be dependent on pH, ionic strength and conditioning time. Adhesion of bacterial cells was found to be more on hematite and coal when compared to quartz. The adsorption isotherms of Bacillus polymyxa cells with respect to all the three minerals were found to obey Langmuir isotherm. Flocculation studies demonstrated that the settling rate of hematite and coal was enhanced in presence of bacterial cells and electrolyte. However quartz settled much slower under the same conditions indicating that the quartz particles are being dispersed. Thus, selective flocculation of hematite and coal is possible which can be used in separating them from quartz effectively. The different components of total interaction energy arising from Lifshitz-van der Waal forces, acid/base forces and electrostatic forces were calculated using the van Oss approach. Calculation of the components of the acid base free energy showed that coal and hematite were hydrophobic compared to quartz and the bacterium. From total interaction energy calculation based on the extended DLVO theory, hematite and coal were found to have a net negative interaction energy in acidic pH values and hence attractive forces are predominant. Quartz was found to have a net repulsive energy at all the pH values at low ionic strengths but increase in ionic strength the interaction energy become attractive. The AGLW values of quartz was found to be attractive which is probably responsible for bacterial adhesion onto quartz.

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Gu, Xiangyang. "Improving heavy metal bioleaching efficiency through microbiological control of inhibitory substances in anaerobically digested sludge." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/504.

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Chandraprabha, M. N. "Studies On Bio-Oxidation A Refractory Gold Containing Sulphidic Concentrate With Respect To Optimization And Modeling." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/188.

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Although bacterial leaching of sulphidic minerals is a well-known phenomenon, it is only in the last ten years that full-scale bacterial leaching plants have been commissioned for gold processing. In order for bacterial leaching to compete successfully with other pretreatment processes for refractory ores, particularly with established technologies such as roasting and pressure leaching, it needs to be efficient. This requires the optimization of the parameters affecting the leaching reaction and the growth of bacteria. The entire biotreatment process is agitation leaching, carried out in stirred reactors or Pachuca type reactors. The bacterial oxidation is a complex reaction involving gaseous, liquid and solid phases. The interactions are highly complex, and analysis is complicated by the presence of solids in the leaching medium. Inspite of the amount of research that has been performed, kinetic and process models are underdeveloped. Since kinetic data varies widely with the type and source of concentrate, experimental data should be generated before doing the full-scale reactor design. In sizing reactors for a commercial scale process, it would be useful to have a mathematical model that one could use to predict the amount and rate of release of metal, as a function of the various operating parameters of the system. G.R.Halli arsenical gold sulphide concentrate obtained from Hutti Gold Mines Ltd., Karnataka, was chosen for our study, because of its high refractoriness. An indegenous strain of Thiobacillus ferrooxidans was used for biooxidation. The experiments were conducted in a well-agitated stirred tank reactor under controlled conditions. Sparged air was supplemented with carbon-dioxide for optimized growth. In this work, more than 90% gold and 95% silver could be recovered from the sulphidic gold concentrate when bioleaching was used ahead of cyanidation, compared to 40% and 50% by direct cyanidation. A generalized model, which accounts for both direct bacterial attack and indirect chemical leaching, has been proposed for the biooxidation of refractory gold concentrates. The bacterial balance, therefore, accounts for its growth both on solid substrate and in solution, and for the attachment to and detachment from the surface. The overall process is considered to consist of several sub-processes, each of which can be described in terms of a mechanism and related rate expressions. These sub-processes were studied seperately under kinetically controlled conditions. The key parameters appearing in the rate equations were evaluated using the experimental data. Since the refractory concentrate contains pyrite and arsenopyrite as the major leachable entities, leaching studies have been done on pure pyrite and arsenopyrite as test minerals and the key parameters in the rate equations are evaluated using this data. The model so developed is tested with the leaching kinetics of the concentrate. The growth of bacteria is dependent on the availability of the substrate, ferrous iron, and the dependence is modelled by the widely accepted Monod equation. The effect of carbon dioxide supplementation on the bacterial activity was studied and the optimal concentration for growth was found to be l%(v/v). Studies on indirect chemical leaching showed that the rate is sensitive to surface area of concentrate. Indirect rate constant of arsenopyrite was found to be greater than that of pyrite, since pyrite is more nobler than arsenopyrite. Conditions of direct leaching alone was obtained at high pulp density and using substrate adapted bacteria. The rate constant of arsenopyrite was found to be greater than that of pyrite. The parameters obtained were tested with the overall batch leaching data of the concentrate and favourable comparision was obtained. Thus, it has been possible to isolate the various simultaneous sub-processes occurring during the leaching and propose useful models to describe these processes in some detail. The model has been extended successfully to predict the continuous leaching behaviour using the parameters obtained from the batch data. Studies on the effect of residence time and pulp density on steady state behaviour showed that there is a critical residence time and pulp density below which washout conditions occur. The critical residence time at 10% pulp density was found to be 11 hrs. Operation at pulp densities lower than 5% and residence times lower than 72 hrs is not favourable for efficient leaching. Studies on the effect of initial ferric iron concentration showed that there exists an optimum concentration of ferric iron at which the time required to reach steady state is minimum.

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27

Chandraprabha, M. N. "Studies On Bio-Oxidation A Refractory Gold Containing Sulphidic Concentrate With Respect To Optimization And Modeling." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/188.

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Although bacterial leaching of sulphidic minerals is a well-known phenomenon, it is only in the last ten years that full-scale bacterial leaching plants have been commissioned for gold processing. In order for bacterial leaching to compete successfully with other pretreatment processes for refractory ores, particularly with established technologies such as roasting and pressure leaching, it needs to be efficient. This requires the optimization of the parameters affecting the leaching reaction and the growth of bacteria. The entire biotreatment process is agitation leaching, carried out in stirred reactors or Pachuca type reactors. The bacterial oxidation is a complex reaction involving gaseous, liquid and solid phases. The interactions are highly complex, and analysis is complicated by the presence of solids in the leaching medium. Inspite of the amount of research that has been performed, kinetic and process models are underdeveloped. Since kinetic data varies widely with the type and source of concentrate, experimental data should be generated before doing the full-scale reactor design. In sizing reactors for a commercial scale process, it would be useful to have a mathematical model that one could use to predict the amount and rate of release of metal, as a function of the various operating parameters of the system. G.R.Halli arsenical gold sulphide concentrate obtained from Hutti Gold Mines Ltd., Karnataka, was chosen for our study, because of its high refractoriness. An indegenous strain of Thiobacillus ferrooxidans was used for biooxidation. The experiments were conducted in a well-agitated stirred tank reactor under controlled conditions. Sparged air was supplemented with carbon-dioxide for optimized growth. In this work, more than 90% gold and 95% silver could be recovered from the sulphidic gold concentrate when bioleaching was used ahead of cyanidation, compared to 40% and 50% by direct cyanidation. A generalized model, which accounts for both direct bacterial attack and indirect chemical leaching, has been proposed for the biooxidation of refractory gold concentrates. The bacterial balance, therefore, accounts for its growth both on solid substrate and in solution, and for the attachment to and detachment from the surface. The overall process is considered to consist of several sub-processes, each of which can be described in terms of a mechanism and related rate expressions. These sub-processes were studied seperately under kinetically controlled conditions. The key parameters appearing in the rate equations were evaluated using the experimental data. Since the refractory concentrate contains pyrite and arsenopyrite as the major leachable entities, leaching studies have been done on pure pyrite and arsenopyrite as test minerals and the key parameters in the rate equations are evaluated using this data. The model so developed is tested with the leaching kinetics of the concentrate. The growth of bacteria is dependent on the availability of the substrate, ferrous iron, and the dependence is modelled by the widely accepted Monod equation. The effect of carbon dioxide supplementation on the bacterial activity was studied and the optimal concentration for growth was found to be l%(v/v). Studies on indirect chemical leaching showed that the rate is sensitive to surface area of concentrate. Indirect rate constant of arsenopyrite was found to be greater than that of pyrite, since pyrite is more nobler than arsenopyrite. Conditions of direct leaching alone was obtained at high pulp density and using substrate adapted bacteria. The rate constant of arsenopyrite was found to be greater than that of pyrite. The parameters obtained were tested with the overall batch leaching data of the concentrate and favourable comparision was obtained. Thus, it has been possible to isolate the various simultaneous sub-processes occurring during the leaching and propose useful models to describe these processes in some detail. The model has been extended successfully to predict the continuous leaching behaviour using the parameters obtained from the batch data. Studies on the effect of residence time and pulp density on steady state behaviour showed that there is a critical residence time and pulp density below which washout conditions occur. The critical residence time at 10% pulp density was found to be 11 hrs. Operation at pulp densities lower than 5% and residence times lower than 72 hrs is not favourable for efficient leaching. Studies on the effect of initial ferric iron concentration showed that there exists an optimum concentration of ferric iron at which the time required to reach steady state is minimum.

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Kotze, Andries Albertus. "Analysis of arsenic resistance in the biomining bacterium, Acidithiobacillus caldus." Thesis, Stellenbosch : University of Stellenbosch, 2007. http://hdl.handle.net/10019.1/17374.

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Thesis (MSc)--University of Stellenbosch, 2006.
ENGLISH ABSTRACT: In this study the chromosomal arsenic resistance (ars) genes shown to be present in all Acidithiobacillus. caldus isolates were cloned and sequenced from At. caldus #6. Ten open reading frames (ORFs) were identified on a clone conferring arsenic resistance, with three homologs to arsenic genes, arsC (arsenate reductase), arsR (regulator) and arsB (arsenite export). This ars operon is divergent, with the arsRC and arsB genes transcribed in opposite directions. Analysis of the putative amino acid sequences of these arsRC and arsB genes revealed that they are the most closely related to the ars genes of Acidithiobacillus ferrooxidans. These ars genes were functional when transformed into an Escherichia coli ars deletion mutant ACSH50Iq, and conferred increased levels of resistance to arsenate and arsenite. ArsC was required for resistance to arsenate, but not for resistance to arsenite. None of the other ORFs enhanced arsenic resistance in E. coli. A transposon located arsenic resistance system (TnAtcArs) has been described for highly arsenic resistant strains of the moderately thermophilic, sulfur-oxidizing, biomining bacterium At .caldus #6. In the latter study it was shown that TnAtcArs confers higher levels of resistance to arsenate and arsenite than the chromosomal operon. TnAtcArs was conjugated into a weakly ars resistant At. caldus strain (C-SH12) and resulted in greatly increased arsenite resistance. RT-PCR analysis revealed that arsR and arsC are co-transcribed. Despite ORF1 (cadmium inducible-like protein) and ORF5 (putative integrase for prophage CP-933R) not being involved in resistance to arsenic, ORF1 was co-transcribed with arsRC and ORF5 with arsB. Using arsR-lacZ and arsB-lacZ fusions it was shown that the chromosomal ArsR-like regulator of At. caldus acts as a repressor of the arsR and arsB promoter expression. Induction of gene expression took place when either arsenate or arsenite was added. The chromosomal located ArsR was also able to repress TnAtcArs, but the transposon-located ArsR was unable to regulate the chromosomal system.
AFRIKAANSE OPSOMMING: In hierdie studie is die chromosomale arseen weerstandbiedendheidsgene (ars gene), teenwoordig in alle Acidithiobacillus caldus isolate, gekloon en die DNA volgorde daarvan vanaf At. caldus #6 bepaal. Tien oopleesrame (ORFs) is geïdentifiseer op ‘n kloon wat arseen weerstandbiedend is, met drie homoloog aan ars gene, nl. arsC (arsenaat reduktase), arsR (reguleerder) en arsB (membraan-geleë pomp wat arseniet uitpomp). Die ars operon is gerangskik met die arsRC en arsB gene wat in teenoorgestelde rigtings getranskribeer word. Analise van die afgeleide aminosuurvolgorde van dié ars gene het getoon hulle is naverwant aan die ars gene van Acidithiobacillus ferrooxidans. Die ars gene was funksioneel na transformasie na ‘n E. coli ars mutant (ACSH50Iq), en het ‘n hoër vlak van weerstand teen arsenaat en arseniet gebied. ArsC was nodig vir weerstand teen arsenaat, maar nie vir weerstand teen arseniet nie. Geen van die ander ORFs het arseen weerstandbiedendheid in E. coli bevorder nie. Voorheen is ‘n ars operon, geleë op ‘n transposon (TnAtcArs), in ‘n hoogs arseen-weerstandbiedende stam van die middelmatige termofiliese, swawel-oksiderende, bio-ontgunning (“biomining”) bakterie Acidithiobacillus caldus #6 beskryf. In laasgenoemde studie is gevind dat TnAtcArs hoër vlakke van weerstand bied teen arsenaat en arseniet as die chromosomale operon. TnAtcArs is na ‘n lae arseen-weerstandbiedende At. caldus stam (C-SH12) gekonjugeer. Die resultaat was ‘n groot verhoging in arseen weerstandbiedendheid. RT-PCR analise het onthul dat arsR en arsC saam getranskribeer word. Benewens die feit dat ORF1 (kadmium induseerbare protein) en ORF5 (afgeleide integrase vir profaag CP-933R) nie betrokke is in weerstand teen arseniet and arsenaat nie, is ORF1 saam met arsRC getranskribeer en ORF5 saam met arsB. Deur gebruik te maak van die fusie-gene arsR-lacZ en arsB-lacZ is bewys dat die chromosomale ArsR reguleerder van At. caldus as ‘n inhibeerder van die arsR en arsB promoter uitdrukking funksioneer. Indusering van geen uitdrukking vind plaas wanneer arseniet of arsenaat bygevoeg word. Die chromosomaal-geleë ArsR is ook in staat om TnAtcArs te inhibeer, terwyl die transposon geleë ArsR nie daartoe in staat is om die chromosomale ars sisteem te reguleer nie.

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29

Goldschmidt, Gunther Karl. "Cloning, Sequencing and Partial Characterization of the Accessory Gene Region of Plasmid pTC-F14 isolated from the Biomining Bacterium Acidithiobacillus caldus f." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/1588.

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Thesis (MSc (Microbiology))--University of Stellenbosch, 2005.
Plasmid pTC-F14 is a 14.2kb promiscuous, broad-host range IncQ-like mobilizable plasmid isolated from Acidithiobacillus caldus f. At. caldus is a member of a consortium of bacteria (along with Acidithiobacillus ferrooxidans and Leptospirilum ferrooxidans) that is used industrially for decomposing metal sulphide ores and concentrates at temperatures of 40ºC or below which is now a well-established industrial process to recover metals from certain copper, uranium and gold-bearing minerals or mineral concentrates. These biomining microbes are usually obligately acidophilic, autotrophic, usually aerobic iron- or sulphur-oxidizing chemolithotrophic bacteria. Their remarkable physiology allows them to inhabit an ecological niche that is largely inorganic and differs from those environments populated by the more commonly studied non-acidophilic heterotrophic bacteria. At. caldus, is a moderately thermophilic (45 to 50ºC), highly acidophilic (pH1.5 to 2.5) sulphur-oxidizing bacterium, and its role as one of the major players in the industrial decomposition of metal sulphide ores has become evident in recent years. At. caldus f from which pTC-F14 was isolated was found to be one of two dominant organisms in a bacterial consortium undergoing pilot-scale testing for the commercial extraction of nickel from ores.

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30

Türe, Didem Beyhan Mehmet. "Kirlenmiş sedimentlerin biyoliç yöntemi ile iyileştirilmesi /." Isparta : SDÜ Fen Bilimleri Enstitüsü, 2008. http://tez.sdu.edu.tr/Tezler/TF01219.pdf.

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31

Nicolau, Paula Bacelar V. C. "Novel iron-oxidising acidophilic heterotrophic bacteria from mineral leaching environments." Thesis, Bangor University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321390.

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32

Blandón, Nury Alexandra Muñoz [UNESP]. "Recuperação de níquel e outros metais a partir de diferentes fontes (rejeitos minerais de processo industrial e pentlandita '(Ni,Fe)IND. 9' 'S IND. 8' ) mediante lixiviação ácida e bacteriana." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/100745.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Uma possibilidade para a recuperação de metais a partir de minerais com baixos teores ou de rejeitos industriais é a utilização da lixiviação com micro-organismos. A biolixiviação é o processo de oxidação bacteriana de sulfetos metálicos contendo metais de valor (por exemplo, níquel, cobre ou zinco), os quais são liberados para a solução, seguida da recuperação por técnicas metalúrgicas convencionais. Estudos de biolixiviação de concentrados de sulfetos minerais em tanques agitados e, sobretudo em pilhas, têm sido desenvolvidos em escala piloto e comercial. Entretanto, poucos trabalhos têm sido realizados sobre o aproveitamento de rejeitos minerais de processos convencionais, tais como flotação ou fusão em forno “flash”, por rotas biotecnológicas. O objetivo deste trabalho foi recuperar níquel e cobre de rejeitos industriais, provenientes de processo de flotação e de fusão, utilizando bactérias, especialmente da espécie Acidithiobacillus ferrooxidans ou pelo uso de soluções ácidas, em escala de laboratório. Também foram realizados experimentos de biolixiviação de um sulfeto de níquel (pentlandita) para avaliar o processo de solubilização do metal. Conjuntamente, outros experimentos foram realizados com a finalidade de se obter novas linhagens isoladas a partir destes rejeitos minerais. Suas diferenças fisiológicas foram avaliadas. A partir dos experimentos com os rejeitos encontrou-se que com a escória foi possível obter 13% de níquel e 8 % de cobre em solução após 14 dias de lixiviação biológica. Com soluções ácidas, em pH 0,5 e 1,0, as recuperações foram de 56% de níquel e 24% de cobre em pH 0,5 enquanto que em pH 1,0 as concentrações foram de 21% e 12% de niquele e cobre, respectivamente. Para a recuperação de níquel e cobre deste rejeito sugere-se a lixiviação ácida e não bacteriana. Com a lama as porcentagens...
Bacterial leaching is a feasible to recover metals from minerals with low grade or from mine wastes using microorganisms. The bioleaching process is the bacterial oxidation of valuables metals bearing sulphide minerals (e.g. nickel, copper or zinc), which are released to the solution, followed by conventional recovered by metallurgical techniques. Studies on bioleaching of sulphide minerals concentrates in stirred tanks and, particularly, in heaps, have been developed on pilot and commercial scales. However, few studies have been undertaken on using of mineral wastes from conventional processes such as flotation or flashing smelting through biotechnological routes. This work aims at recovering nickel and copper from industrial wastes such as flotation tailings and slag using bacteria, especially Acidithiobacillus ferrooxidans species, or using acid solutions at laboratory scale. Experiments were also accomplished for nickel sulfide bioleaching to evaluate the metal dissolution process, for comparison purpose. Other experiments were also carried out to obtain new strains isolated from mineral waste to study the physiological differences between them. After 14 days of bioleaching of slag it was possible to extract 13% of nickel and 8% of copper in solution while with acid solutions the extractions were 56% of nickel and 24% of copper at pH 0.5 and 21% and 12% at pH 1.0, respectively. For the metals solubilization from the slag it is suggested the acid leaching instead of bioleaching. With the flotation tailings the recoveries of nickel and copper were 23% e 16% at pH 0.5 or 1.0 while after 14 days with bioleaching the concentrations in solution were 46 % and 17% for nickel and copper. These results show that the flotation tailings can be treated with biological leaching for a higher recovery of metals. The studies of nickel sulfide bioleaching with different bacterial species reached only... (Complete abstract click electronic access below)

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33

Yahya, Abidah. "Physiological and phylogenetic studies of some novel acidophilic mineral-oxidising bacteria." Thesis, Bangor University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322564.

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34

Blandón, Nury Alexandra Muñoz. "Recuperação de níquel e outros metais a partir de diferentes fontes (rejeitos minerais de processo industrial e pentlandita '(Ni,Fe)IND. 9' 'S IND. 8' ) mediante lixiviação ácida e bacteriana /." Araraquara : [s.n.], 2010. http://hdl.handle.net/11449/100745.

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Resumo: Uma possibilidade para a recuperação de metais a partir de minerais com baixos teores ou de rejeitos industriais é a utilização da lixiviação com micro-organismos. A biolixiviação é o processo de oxidação bacteriana de sulfetos metálicos contendo metais de valor (por exemplo, níquel, cobre ou zinco), os quais são liberados para a solução, seguida da recuperação por técnicas metalúrgicas convencionais. Estudos de biolixiviação de concentrados de sulfetos minerais em tanques agitados e, sobretudo em pilhas, têm sido desenvolvidos em escala piloto e comercial. Entretanto, poucos trabalhos têm sido realizados sobre o aproveitamento de rejeitos minerais de processos convencionais, tais como flotação ou fusão em forno "flash", por rotas biotecnológicas. O objetivo deste trabalho foi recuperar níquel e cobre de rejeitos industriais, provenientes de processo de flotação e de fusão, utilizando bactérias, especialmente da espécie Acidithiobacillus ferrooxidans ou pelo uso de soluções ácidas, em escala de laboratório. Também foram realizados experimentos de biolixiviação de um sulfeto de níquel (pentlandita) para avaliar o processo de solubilização do metal. Conjuntamente, outros experimentos foram realizados com a finalidade de se obter novas linhagens isoladas a partir destes rejeitos minerais. Suas diferenças fisiológicas foram avaliadas. A partir dos experimentos com os rejeitos encontrou-se que com a escória foi possível obter 13% de níquel e 8 % de cobre em solução após 14 dias de lixiviação biológica. Com soluções ácidas, em pH 0,5 e 1,0, as recuperações foram de 56% de níquel e 24% de cobre em pH 0,5 enquanto que em pH 1,0 as concentrações foram de 21% e 12% de niquele e cobre, respectivamente. Para a recuperação de níquel e cobre deste rejeito sugere-se a lixiviação ácida e não bacteriana. Com a lama as porcentagens... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Bacterial leaching is a feasible to recover metals from minerals with low grade or from mine wastes using microorganisms. The bioleaching process is the bacterial oxidation of valuables metals bearing sulphide minerals (e.g. nickel, copper or zinc), which are released to the solution, followed by conventional recovered by metallurgical techniques. Studies on bioleaching of sulphide minerals concentrates in stirred tanks and, particularly, in heaps, have been developed on pilot and commercial scales. However, few studies have been undertaken on using of mineral wastes from conventional processes such as flotation or flashing smelting through biotechnological routes. This work aims at recovering nickel and copper from industrial wastes such as flotation tailings and slag using bacteria, especially Acidithiobacillus ferrooxidans species, or using acid solutions at laboratory scale. Experiments were also accomplished for nickel sulfide bioleaching to evaluate the metal dissolution process, for comparison purpose. Other experiments were also carried out to obtain new strains isolated from mineral waste to study the physiological differences between them. After 14 days of bioleaching of slag it was possible to extract 13% of nickel and 8% of copper in solution while with acid solutions the extractions were 56% of nickel and 24% of copper at pH 0.5 and 21% and 12% at pH 1.0, respectively. For the metals solubilization from the slag it is suggested the acid leaching instead of bioleaching. With the flotation tailings the recoveries of nickel and copper were 23% e 16% at pH 0.5 or 1.0 while after 14 days with bioleaching the concentrations in solution were 46 % and 17% for nickel and copper. These results show that the flotation tailings can be treated with biological leaching for a higher recovery of metals. The studies of nickel sulfide bioleaching with different bacterial species reached only... (Complete abstract click electronic access below)
Orientador: Oswaldo Garcia Júnior
Coorientador: Denise Bevilaqua
Banca: Maria Lucia Gosales da Costa Araújo
Banca: Ana Teresa Lombardi
Banca: Wilson Cervi da Costa
Banca: Luis Gonzaga Santos Sobral
Doutor

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35

Janosch, Claudia [Verfasser], Wolfgang [Akademischer Betreuer] Sand, and Bettina [Akademischer Betreuer] Siebers. "Sulfur oxidation in moderately thermophilic leaching bacteria / Claudia Janosch. Gutachter: Bettina Siebers. Betreuer: Wolfgang Sand." Duisburg, 2013. http://d-nb.info/1042934614/34.

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36

Khalfet, Ridha. "Étude d'une colonne à bulles à solide suspendu destinée à la biolixiviation de matières premières minérales : application à la biolixiviation de minerai de pyrite." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL127N.

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On étudie la faisabilité du procédé de biolixiviation de minerais sulfurés métalliques dans une colonne à bulles à solide suspendu, à priori moins énergivore que le réacteur mécaniquement agité utilisé habituellement dans l'industrie minéralurgique. Afin de donner les bases du dimensionnement du réacteur, des études hydrodynamique, de transfert de matière gaz-liquide et de transfert de chaleur à un tube de transfert ont été réalisées sur une colonne pour deux types de particules (billes de verre et particules de pyrite). La rétention de gaz est plus petite en milieu triphasique qu'en système biphasique et elle n'est pas affectée par la vitesse du liquide ni par la concentration en solide dans la colonne. Même aux plus grandes vitesses utilisées, la concentration en billes de verre n'est pas homogène dans le réacteur. Pour la pyrite, aux vitesses de gaz élevées, le profil de concentration en solide est moins marqué, alors qu'aux faibles vitesses, les particules se concentrent en bas de colonne. L’écoulement de la phase liquide peut être modélisé par deux réacteurs agités en série. Pour le transfert de chaleur sonde/lit, on constate une différence de comportement entre les deux types de particules. Dans le cas des billes de verre, les valeurs de h sont plus faibles qu'en colonne à bulles ; dans le cas de la pyrite, le coefficient de transfert de chaleur est plus important qu'en système eau-air. L’étude du transfert de matière gaz-liquide a montré que les valeurs du coefficient volumique de transfert de matière gaz-liquide en milieu triphasique sont plus faibles qu'en gaz-liquide. Enfin, quelques essais en maquette chaude ont montré que la réaction de biolixiviation avait bien lieu dans la colonne à bulles à solide suspendu, même à des concentrations en solide assez élevées. Au maximum de la croissance des micro-organismes, la réaction de biolixiviation est limitée par le transfert de matière gaz-liquide

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37

Andersson, Stefan. "Influence of liming substances and temperature on microbial activity and leaching of soil organic matter in coniferous forest ecosystems /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5850-1.pdf.

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38

Haddadin, Jamal. "Études microbiologiques et cinétiques de la lixiviation bactérienne en réacteurs : effet de différents paramètres physico-chimiques, développement d'un procédé en réacteurs air-lift et lit-fluidisé et application à l'extraction de l'antimoine." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL063N.

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La lixiviation bactérienne est l'application biotechnologique la plus importante dans l'industrie métallurgique, celle-ci est utilisée pour la récupération des métaux par lessivage, utilisant les capacités que possèdent certains micro-organismes à solubiliser les métaux. Ce travail est divisé en quatre sections: premièrement, nous avons identifié la composition microbiologique de la culture mixte en notre possession. Cette culture mixte est composée de trois populations bactériennes. Deuxièmement, nous avons étudié l'influence de certains paramètres physico-chimiques tels que le pH, la température, la concentration en CO2, le taux de solides et l'ajout de Fe3+ au milieu réactionnel sur la cinétique de la biolixiviation, en culture discontinue. Ces études ont notamment conduit à la détermination d'un pH (1. 75), d'une température (32-37°C) et d'une concentration en CO2 (0,03 et 2% v/v) optimaux pour ce procédé. Troisièmement, nous avons comparé différents systèmes réactionnels (air-lift, lit fluidisé et mécaniquement agité) pour aider au choix d'une future technologie alternative. Notre dernière contribution a porté sur l'étude de la capacité de la culture mixte à oxyder des déchets industriels contenant de l'antimoine, en culture discontinue. Nous avons étudié le rôle important de l'interaction galvanique entre la pyrite et les résidus antimoniés sur la récupération de l'antimoine

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39

Florian, Bianca [Verfasser], Wolfgang [Akademischer Betreuer] Sand, and Hans-Curt [Akademischer Betreuer] Flemming. "Investigation of initial attachment and biofilm formation of mesophilic leaching bacteria in pure and mixed cultures and their efficiency of pyrite dissolution / Bianca Michaela Florian. Gutachter: Hans-Curt Flemming. Betreuer: Wolfgang Sand." Duisburg, 2012. http://d-nb.info/1023643790/34.

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Farias, Christyan Paiva. "Fungos promotores do crescimento vegetal e da fitorremediação de metais pesados em combinação com biochar." Universidade Federal de Uberlândia, 2018. http://dx.doi.org/10.14393/ufu.di.2018.713.

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A busca por medidas sustentáveis para melhorar e suprir a demanda por alimentos que o crescimento populacional exige, aliado a escassez de terras produtivas, além do acúmulo excessivo de metais no ambiente devido a atividades como mineração e aplicação de fertilizantes no solo, foram as duas problemáticas que motivaram o presente estudo. O uso de fungos promotores do crescimento vegetal: Beauveria bassiana, Metarhizium anisopliae, Pochonia chlamydosporia, Purpureocillium lilacinum e Trichoderma asperella, pode tanto vir a influenciar o aumento da produtividade como potencializar a fitorremediação de metais pesados no solo. Esses fatos são explicados pela capacidade do consórcio fúngico de sintetizar e induzir as plantas a produzir fitohormônios direcionados para o melhor desenvolvimento das raízes do hospedeiro. O maior desenvolvimento de raízes pode estimular a fitoextração de metais do solo e conferir tolerância das plantas à contaminação. Na intenção de avaliar a influência dos fungos no desenvolvimento das plantas, foram realizados tratamentos das sementes de soja e milho e aplicação na parte aérea da cultura da cana-de-açúcar. Já para analisar a influência desses organismos no processo de fitorremediação de Cu, Zn e Mn em colunas de solos cultivados com Jacaranda mimosifolia D. Don, os fungos foram inoculados no solo e na parte aérea das plantas. Todos os tratamentos tiveram 6 repetições e suas médias foram submetidas à análise de variância e teste de média ao nível de 5% de probabilidade. O consórcio fúngico condicionou o crescimento de raízes de soja e milho, aumentou a colonização micorrízica arbuscular em soja e cana-de-açúcar. No jacarandá, os fungos melhoraram o desenvolvimento de raízes e parte aérea, maior acúmulo de Mn e Zn na planta, melhor translocação de Mn e Zn das raízes para a parte aérea, além de diminuir o estresse fisiológico. Além disso, a aplicação conjunta de fungos e biochar nas mudas proporciona proteção à sua atividade fotossintética e reduz o risco ambiental de contaminação por metais por diminuir o total de Cu, Mn e Zn lixiviado. O biochar foi adquirido por meio da pirólise lenta do resíduo do beneficiamento da madeira de eucalipto e aplicado superficialmente no solo. Com isso, esse estudo mostrou que os fungos utilizados apresentam potencial para colaborar com o aumento da produtividade de culturas comerciais e colaborar com a melhoria na remediação de solos contaminados com íons metálicos.
The search for sustainable measures to improve and meet the demand for food that population growth requires, combined with the scarcity of productive land, in addition to the excessive accumulation of metals in the environment due to activities such as mining and application of soil fertilizers, were the two problems that motivated the present study. The use of fungi plant growth promoters: Beauveria bassiana, Metarhizium anisopliae, Pochonia chlamydosporia, Purpureocillium lilacinum and Trichoderma asperella can both influence on increasing productivity as the phytoremediation of heavy metals in the soil. These facts are explained by the capacity of the fungal Consortium to synthesize and induce plants to produce phytohormone targeted for the better development of the roots of the host. The further development of roots can stimulate phytoextraction of metals from the soil and give plants tolerance to contamination. In order to evaluate the influence of fungi on the development of plants, were done seed treatments of soybeans and corn and application in aerial part of the culture of sugar cane. To analyze the influence of these organisms in the process of phytoremediation of Cu, Zn and Mn in soil columns cultivated with Jacaranda mimosifolia D. Don, fungi were inoculated in soil and aerial part of plants. All treatments had 6 reptitions and their averages were subjected to analysis of variance and average test at 5% probability. The fungal consortium has conditioned the growth of roots of soybeans and corn, mycorrhizal colonization increased in soybeans and sugar cane. In jacarandá, fungi have improved the development of roots and shoots, greater accumulation of Mn and Zn in plant, best of Mn and Zn translocation from roots to shoots, in addition to decrease physiological stress. In addition, the joint application of fungus and biochar in seedlings provides protection to photosynthetic activity and reduces the risk of environmental contamination by metals by decreasing the amount of Cu, Mn and Zn leached. The biochar was acquired through the slow pyrolysis of the eucalyptus wood processing residue and applied superficially to the soil. With that, this study showed that fungi used present potential to contribute to the increased productivity of commercial crops and contribute to the improvement in the remediation of soils contaminated with metal ions.
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41

Marais, Caroline. "Formation de concrétions calcomagnésiennes par polarisation cathodique associée à la biocalcification et à l’utilisation de matériaux recyclés pour la protection côtière." Electronic Thesis or Diss., La Rochelle, 2023. http://www.theses.fr/2023LAROS020.

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L’objectif de cette étude vise à développer une solution à faible impact environnemental pour la consolidation des zones côtières partiellement immergées. Cette solution, la formation d’un agglomérat calcomagnésien par électrolyse de l’eau de mer, s’appuie d’une part sur l’économie des ressources locales par valorisation des déchets inertes du BTP (granulats recyclés (GR)) ; et d’autre part sur le processus de biominéralisation impliquant l’hydratation du CO2 par l’enzyme anhydrase carbonique (AC) présente chez les bactéries marines prélevées dans le Port de La Rochelle. Trois axes majeurs ont été étudiés pour optimiser la précipitation d’un liant composé de CaCO3 et de Mg(OH)2 (le dépôt calcomagnésien) au sein de l’agglomérat : l’effet de la dissolution des GR dans l’eau de mer, l’application d’une polarisation cathodique via à un écoulement d’eau de mer et l’étude de la bio-précipitation de CaCO3 par piégeage du CO2 (rôle de l’AC) par les souches marines L’écoulement d’eau de mer a permis de former un agglomérat de 200 cm3 en 60 jours, à -500µA/cm², soit une cinétique de croissance de 3 cm3/jr. Une augmentation de 10% de la compacité a été constatée dans le cas d’une grille enfouie (dans les GR) en immersion et en émersion. L’écoulement et la présence des granulats recyclés favorisent la précipitation du CaCO3 sous forme de calcite pour tendre vers un rapport Mg(OH)2/CaCO3 inférieur ou égale à 1, en polarisation continu ou cyclique. La libération excessive des ions calcium et sulfate en solution liée à la dissolution de la matrice cimentaire contenue au sein des GR, peut expliquer l’augmentation de CaCO3. Toutes les souches ont bio-précipité du CaCO3 dans leur milieu optimal et en présence d’eau de mer naturelle. Leur production a drastiquement chuté avec une teneur à 3% en CO2 (CO2 atmosphérique =0,4%) ainsi qu’en présence de lixiviat de granulats recyclés. À 3% en CO2, le pH du milieu augmente en présence des souches, pouvant témoigner d’une activité de l’AC
The objective of this study is to develop a low environmental impact solution for the consolidation of partially submerged coastal areas. This solution, the formation of a limestone concretion based on seawater electolysis, relies on two main aspects: firstly, the efficient use of local resources through the valorization of inert construction waste (recycled aggregates (RA)); and secondly, the biomineralization process involving the hydration of CO2 by the enzyme carbonic anhydrase (CA) found in marine bacteria sampled from the Port of La Rochelle. Three major axes were studied to optimize the precipitation of a binder within the limeston concretion composed of CaCO3 and Mg(OH)2 (the calcareous deposit): the effect of RA dissolution in seawater, the application of cathodic polarization via seawater flow, and the study of CaCO3 bio-precipitation by CO2 capture (the role of CA) by marine strains. Seawater flow allowed the formation of a 200 cm3 agglomerate in 60 days at -500µA/cm², resulting in a growth rate of 3 cm3/day. A 10% increase in compactness was observed when the grid was buried (within the RA) either submerged or emerged. Seawater flow and the presence of RA favored the precipitation of CaCO3, particularly in the form of calcite, leading to an Mg(OH)2/CaCO3 ratio less than or equal to 1, whether under continuous or cyclic polarization. The excessive release of calcium and sulfate ions into solution due to the dissolution of the cementitious matrix within the RA could explain the increase in CaCO3. All strains bio-precipitated CaCO3 in their optimal medium and in the presence of natural seawater. Their production drastically decreased at 3% CO2 (atmospheric CO2 = 0.4%) and in the presence of leachate from recycled aggregates. At 3% CO2, the pH of the medium increased in the presence of the strains, which could indicate the activity of CA

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Simate, Geoffrey Simate. "Bacterial leaching of nickel literites using chemolithotrophic microorganisms." Thesis, 2009. http://hdl.handle.net/10539/7098.

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Biohydrometallurgy, an interdisciplinary field involving geomicrobiology, microbial ecology, microbial biochemistry, and hydrometallurgy, is a promising novel technology for recovering valuable minerals from traditionally difficult-to-process ores. In this study, the possibility to treat nickel laterites biohydrometallurgically using chemolithotrophic microorganisms was investigated. Nickel laterite contains metal values but is not capable of participating in the primary chemolithotrophic bacterial oxidation because it contains neither ferrous iron nor substantial amount of reduced sulphur. Its metal value can, however, be recovered by allowing the primary oxidation of pyrite, or similar iron/sulphur minerals to provide sulphuric acid solutions, which solubilise the metal content. In order to have an insight on the use of chemolithotrophic bacteria in this process, it was important to first understand the role and effects of sulphuric acid. Its effect was compared to citric acid and ferric sulphate. Results showed that sulphuric acid performed better, in terms of nickel recovery, than citric acid or ferric sulphate of the same initial concentration. However, citric acid performed better at the same initial pH. A synergic effect was observed in a mixture of sulphuric and citric acids. In the bacterial leaching test works, sulphur substrate exhibited better effects in terms of acidification and nickel recovery than pyrite substrate. Using a statistically-based optimization strategy called response surface methodology, the theoretical optimum conditions for maximum nickel recovery (79.8%) within the range of conditions studied was found to be initial pH of 2.0, 63μm particle size and 2.6% pulp density. This work has shown that by the addition of a sulphur containing material, nickel laterites can be leached by chemolithotrophic microorganisms via the sulphuric acid produced.

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Bolorunduro, Samuel Adewale. "Kinetics of leaching of chalcocite in acid ferric sulfate media : chemical and bacterial leaching." Thesis, 1999. http://hdl.handle.net/2429/9400.

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The lack of a clear understanding of the rate of chalcocite (Cu₂S) and covellite (CuS) leaching in the presence and absence of bacteria has been a limitation on the optimization of hydrometallurgical processes for the recovery of copper from these minerals. In order to enhance the performance of heaps and other leaching processes for these minerals, there is a need to examine the conditions required to improve the rate of leaching. Such an investigation will produce a particle scale model (for the intrinsic rate of leaching), which can be combined with a heap scale model to form a comprehensive heap leaching model, or with a leaching macro-model to form a tank leaching model. The robustness of such a model will be its ability to determine the effects of changing parameters on the rate limiting steps. Chalcocite oxidation was investigated by leaching high grade natural minerals in acidic ferric/ferrous sulfate solutions. The temperature was varied between 35° and 75° C. The ferric concentration varied between 0.015 and 0.232 mol/L, and the ferrous concentration varied between 0.001 and 0.233 mol/L. The redox potential of the solution (at 25°C) was varied between 450 and 651 mV (vs. Ag/AgCl) to determine the effect of this parameter on the leaching kinetics. The two well known, significant stages of leaching were observed and characterized by mineralogical studies. The first stage leach was characterized by 50% copper extraction and the conversion of chalcocite, ultimately to second stage covellite (CuS). Some non-stoichiometric copper sulfides were formed prior to the formation of the second stage covellite. The first stage leaching reaction was rapid at all temperatures. The redox potential had no effect on the rate of this reaction. The second stage leach was characterized by the conversion of the second stage covellite (which was the by-product of the first stage) to copper, elemental sulfur and sulfate. At higher temperatures, sulfur formation was predominant and the reaction was fast. At lower temperatures, sulfur formation was predominant up to about 70% copper extraction. Subsequently, sulfate formation occurred. The effect of the solution redox potential on the kinetics of second stage leaching was significant. During bacterial leaching, it was observed that the principal role of the ferrous oxidizing bacteria (Thiobacillus ferrooxidans) was to maintain the required high redox potential at the surface of the minerals. A mathematical model was formulated to explain the ferric leaching kinetics of chalcocite. The first stage kinetics can be explained in terms of a mixed diffusion/chemical reaction model, in which the rate of reaction is simultaneously limited by the diffusion of ferric ions to the mineral surface and by the chemical reaction. Though the partially oxidized particles disintegrate before the commencement of the second stage leach, each of the particles leaches as a discrete grain and the second stage kinetics are controlled by the chemical reaction, which is one-half order dependent on the ferric concentration. The leaching process can be described by an electrochemical mechanism in which the rate-limiting step of the first stage is electron transfer in the cathodic reaction, and the rate-limiting step of the second stage is electron transfer in the anodic reaction.

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Tlotleng, Nonhlanhla. "Evaluation of atomic force microscopy techniques for imaging and studying surface characteristics of bacterial systems involved in bioleaching." Thesis, 2009. http://hdl.handle.net/10210/2457.

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M.Tech
Atomic force microscopy (AFM) has been an integral tool in bacterial studies for resolving surface structures. Novel applications of this instrument in research require the development of sample preparation techniques and improvement of existing ones. Careful selection of the scanning parameters is particularly crucial when exploring the full potential of the AFM. The objective of this study was to design sample preparation methods for AFM imaging bioleaching bacteria and optimise the scanning parameters (deflection setpoint, feedback loop and the scan rate) for contact mode (CM) imaging in air. The method should be simple, fast and cost effective. The strategy used in this study of (i) evaluation of support substrates for bacterial attachment, (ii) investigation of the effect of pH and centrifugation on cell samples during imaging. Centrifuged and noncentrifuged cell samples suspended in either deionised water (pH 7) or acidified water (pH 1.5) were tested for imaging. Mica and glass cover slips were used as potential substrates for attachment. Cells were attached to substrates for imaging by simple adsorption (‘air-drying’ method). To optimise the scanning parameters, the effect of different values of the scan rate, deflection setpoint and the feedback gains on the quality of AFM imaging was investigated. Optimisation of these parameters was found to be instrumental when imaging weakly adsorbed samples prepared by simple adsorption and ‘soft’ samples such as bacterial cells. The results obtained from these experiments were used during preparation of iron- oxidising leaching bacteria for AFM imaging. The surface morphology of iron-grown bacterial samples was investigated with contact mode AFM in air. Reproducible results obtained in each scan shown by the stability of morphological characteristics of bacterial samples indicate that (i) mica can be used successfully as a substrate for attaching cells, (ii) centrifuged bacterial samples can be easily imaged (iii) scanning with scan rate values of <0.5Hz, deflection setpoint of between 0.2-0.5V and feedback values of < 5.000V improve the image quality and can prevent deformation of the bacterial cells by the tip. Non-centrifuged samples could not be imaged, indicating that bacterial cells need to be separated from growth residues as a prerequisite for successful AFM imaging.

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Lizama, Hector M. "Bacterial leaching study of a complex Cu-Zn sulfide ore." 1989. http://hdl.handle.net/1993/16910.

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"The low potential bioleaching of chalcopyrite with ferroplasma JTC3." Thesis, 2009. http://hdl.handle.net/10210/2441.

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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.

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Fosso-Kankeu, Elvis. "Ni²⁺ extraction from low grade leachate of tailing dumps materials using cloned indigenous bacterial species." Thesis, 2012. http://hdl.handle.net/10210/8033.

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Ramcharan, Karishma. "Microbial biotransformation of kimberlite ores." Thesis, 2008. http://hdl.handle.net/10413/541.

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Microbial leaching plays a significant role in the natural weathering of silicate containing ores such as diamond-bearing kimberlite. Harnessing microbial leaching processes to pre-treat mined kimberlite ores has been proposed as a means of improving diamond recovery efficiencies. The biomineralization of kimberlite is rarely studied. Therefore, this study investigated the feasibility of exploiting both chemolithotrophic and heterotrophic leaching processes to accelerate the weathering of kimberlite. Preliminary investigations using mixed chemolithotrophic leaching cultures were performed on four finely ground kimberlite samples (<100μm) sourced from different mines in South Africa and Canada. Mixed chemolithotrophic cultures were grown in shake flasks containing kimberlite and inorganic basal media supplemented either with iron (Fe2+, 15g/l) or elemental sulfur (10g/l) as energy sources. Weathering due to dissolution was monitored by Inductive Coupled Plasma (ICP) analyses of Si, Fe, K, Mg and Ca in the leach solutions at known pH. Structural alterations of kimberlite after specified treatment times were analyzed by X-ray Powder Diffraction (XRD). The results of the preliminary investigation showed that weathering can be accelerated in the presence of microbial leaching agents but the degree of susceptibility and mineralogical transformation varied between different kimberlite types with different mineralogical characteristics. In general, the results showed that the kimberlite sample from Victor Mine was most prone to weathering while the sample from Gahcho Kue was the most resistant. It was therefore deduced that kimberlite with swelling clays as their major mineral component weathered relatively more easily when compared to kimberlite that consisted of serpentine and phlogopite as their major minerals. Gypsum precipitates were also distinguished indicating that a partial alteration in the kimberlite mineralogical structure occurred. Both energy sources positively influenced the dissolution process, with sulfur producing superior results. This was attributed to the generation of sulfuric acid which promotes cation dissolution and mineral weathering. Success in the preliminary investigations led to further experimental testing performed to determine the effect of particle size and varying energy source concentrations on the biotransformation of kimberlite. It was observed that although weathering rates of the larger kimberlite particles (>2mm<5mm) were lower than that of the finer particles, slight changes in their mineralogical structures represented by the XRD analyses were seen. Optimisation studies of energy source concentration concluded that although the highest concentration of elemental sulfur (20% w/w) and ferrous iron (35% w/w) produced the most pronounced changes for each energy source tested, the leaching efficiency at these concentrations were not drastically greater than the leaching efficiency of the lower concentrations, as expected. Following the success of batch culture shake flasks weathering tests, the effect of continuous chemolithotrophic cultures on the biotransformation of larger kimberlite particles (>5mm<6.7mm) was investigated. A continuous plug-flow bioleach column was used to model the behaviour of chemolithotrophic consortia in a dump- or heap leaching system. Two sequential columns were setup, in which the first consisted of kimberlite mixed with sulfur and the second purely kimberlite. Inorganic growth medium was pumped to the first column at a fixed dilution rate of 0.25h-1 and the leachate from the first column dripped into the second. After an 8 week investigation period, the ICP and XRD data showed that weathering did occur. However, the pH results showed that the leaching process is governed by the amount of acid produced by the growth-rate independent chemolithotrophic consortia. Data from pH analyses also showed that the leaching bacteria reached ‘steady state’ conditions from day 45 onwards. The pH also remained higher in the second column than in the first column highlighting the alkaline nature of the kimberlite ores and its ability to act as a buffering agent and resist weathering. This important factor, as well as further optimisation studies in process operating conditions and efficiency, needs to be considered when establishing heap-leaching technology for these kimberlite ores. In the preliminary heterotrophic investigation, Aspergillus niger was used to produce organic metabolites to enhance kimberlite mineralization. The results demonstrated that the organic acid metabolites generated caused partial solubilization of the kimberlite minerals. However, it was deduced that for more significant changes to be observed higher amounts of organic acids need to be produced and maintained. The results obtained in this study also showed that the type of kimberlite presents a different susceptibility to the dissolution process and the presence of the fungal cells may improve the leaching efficiency. The results in this study provided an optimistic base for the use of microbial leaching processes in accelerating the weathering of kimberlite. These findings may also serve to supply data to formulate recommendations for further and future column microbial leach tests as well as validation and simulation purposes.
Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2008.

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Selvi, S. Chirpa. "Electrobioleaching Of Sphalerite Flotation Concentrate." Thesis, 1997. https://etd.iisc.ac.in/handle/2005/1799.

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Selvi, S. Chirpa. "Electrobioleaching Of Sphalerite Flotation Concentrate." Thesis, 1997. http://etd.iisc.ernet.in/handle/2005/1799.

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