Spelling suggestions: "subject:"bacterial leaching."" "subject:"dacterial leaching.""
11 |
Consórcios microbianos associados a ambientes de minas : obtenção, avaliação fisiológica e molecular /Garcia, Íris Gabriela. January 2013 (has links)
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) / Mestre
|
12 |
Ni²⁺ extraction from low grade leachate of tailing dumps materials using cloned indigenous bacterial speciesFosso-Kankeu, Elvis 02 November 2012 (has links)
D.Tech. (Extraction Metallurgy) / Please refer to full text to view abstract
|
13 |
Molecular characterization of iron-oxidizing Leptospirillum strains from around the worldCoram, Nicolette Joanne 12 1900 (has links)
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.
|
14 |
Bioleaching of heavy metals from anaerobically digested sewage sludge using isolated indigenous iron- and sulphur-oxidizing bacteriaChan, Lau Chi 01 January 2001 (has links)
No description available.
|
15 |
Microbial biotransformation of kimberlite ores.Ramcharan, Karishma. January 2008 (has links)
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.
|
16 |
Efeito do potencial de óxido-redução na biolixiviação da calcopiritaSantos, Ana Laura Araújo [UNESP] 19 February 2014 (has links) (PDF)
Made available in DSpace on 2014-11-10T11:09:40Z (GMT). No. of bitstreams: 0
Previous issue date: 2014-02-19Bitstream added on 2014-11-10T11:58:48Z : No. of bitstreams: 1
000773278_20180219.pdf: 476686 bytes, checksum: 6e5775b02410b85dbee6fa185b69ccfc (MD5) Bitstreams deleted on 2018-02-23T13:06:32Z: 000773278_20180219.pdf,. Added 1 bitstream(s) on 2018-02-23T13:07:23Z : No. of bitstreams: 1
000773278.pdf: 3882989 bytes, checksum: 75667e8c9a8c2a3a7f503d07d51be90f (MD5) / 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...
|
17 |
Estudo da oxidação de covelita (CuS) e molibdenita (MoS2) sintéticas por Acidithiobacillus ferrooxidansFrancisco Junior, Wilmo Ernesto [UNESP] 27 January 2006 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:23:06Z (GMT). No. of bitstreams: 0
Previous issue date: 2006-01-27Bitstream added on 2014-06-13T19:08:56Z : No. of bitstreams: 1
franciscojr_we_me_araiq.pdf: 572574 bytes, checksum: 2c57de58f563457427fe3f4ad3a05e17 (MD5) / 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.
|
18 |
Bio-oxidation of ferrous iron at low temperature conditions in a packed bed column bioreactorsChukwuchendo, Emmanuel Chukwunonso January 2016 (has links)
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.
|
19 |
The effect of initial pH on surface properties of ferric ion precipitates formed during microbial oxidation of ferrous ion by Leptospirillum ferriphilum in a CSTRMabusela, Bongolwethu Professor January 2017 (has links)
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.
|
20 |
Efeito do potencial de óxido-redução na biolixiviação da calcopirita /Santos, Ana Laura Araújo. January 2014 (has links)
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
|
Page generated in 0.1242 seconds