EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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6 resultados
Resultados da Pesquisa
Item Copper extraction from coarsely ground printed circuit boards using moderate thermophilic bacteria in a rotating-drum reactor.(2015) Rodrigues, Michael Leonardo Marques; Leão, Versiane Albis; Gomes, Otavio; Lambert, Fanny; Bastin, David; Gaydardzhiev, StoyanThe current work reports on a new approach for copper bioleaching from Printed Circuit Board (PCB) by moderate thermophiles in a rotating-drum reactor. Initially leaching of PCB was carried out in shake flasks to assess the effects of particle size (_208 lm + 147 lm), ferrous iron concentration (1.25–10.0 g/L) and pH (1.5–2.5) on copper leaching using mesophile and moderate thermophile microorganisms. Only at a relatively low solid content (10.0 g/L) complete copper extraction was achieved from the particle size investigated. Conversely, high copper extractions were possible from coarse-ground PCB (20 mm-long) working with increased solids concentration (up to 25.0 g/L). Because there was as the faster leaching kinetics at 50 _C Sulfobacillus thermosulfidooxidans was selected for experiments in a rotating-drum reactor with the coarser-sized PCB sheets. Under optimal conditions, copper extraction reached 85%, in 8 days and microscopic observations by SEM–EDS of the on nonleached and leached material suggested that metal dissolution from the internal layers was restricted by the fact that metal surface was not entirely available and accessible for the solution in the case of the 20 mm-size sheets.Item Bioleaching and chemical leaching as an integrated process in the zinc industry.(2007) Souza, Adelson Dias de; Pina, Pablo dos Santos; Leão, Versiane AlbisThis work sought to integrate bioleaching and chemical leaching as a cost-effective process to treat zinc sulphides. The continuous bioleaching of a sphalerite concentrate, assaying 51.4% Zn, 1.9% Pb, 31.8% S and 9.0% Fe with mesophile iron and sulphur-oxidizing bacteria followed by chemical leaching of the bioleaching residue were assessed. In the bioleaching step, the first reactor was used to produce Fe(III) concentrations as high as 20 g/L. This solution was fed to the subsequent bioleaching reactors to oxidize sphalerite. It was possible to achieve 30% zinc extraction for 70 h residence time. In chemical leaching experiments, carried out with the residue of the bioleaching step, the effects Fetotal and acidity on zinc extraction were studied. It was noticed that Fe(III) concentrations over 12 g/L did not affect zinc recoveries. Furthermore, the higher the acidity, the larger the zinc recovery, for experiments carried out up to 181 g/L sulphuric acid. The results have demonstrated that it is possible to devise a new process capable of achieving 96% zinc extraction, similarly to the conventional roasting–leaching–electrolysis process.Item Bioleaching of a complex nickel–iron concentrate by mesophile bacteria.(2006) Santos, Luciano Rodrigo Gomes; Barbosa, Alexandre Ferraz; Souza, Adelson Dias de; Leão, Versiane AlbisThis work investigates the bioleaching of a complex nickel–iron concentrate (pentlandite, pyrrhotite, and minor amounts of chalcopyrite) using acidophile iron-oxidizing bacteria. It aims to improve the understanding of the mechanism of bacterial action on nickel sulphide bioleaching. The effects of the external addition of Fe(II) and the mineralogical assembly on the extraction of nickel are evaluated. A high nickel extraction (around 70%) can be achieved in batch experiments. Moreover, the external addition of iron has not shown any effect on the extraction of the metal, emphasizing the importance of pyrrhotite dissolution in the first step of bioleaching. It was also examined the morphological features of the sulphides as well as the leach residues and reactions products formed during bioleaching. It was noticed that elemental sulphur was produced on pyrrhotite surfaces, which dissolves ahead of pentlandite. A discussion on how galvanic interactions affect the reactivity of sulphide mineral and the formation of bioleaching products is also presented.Item Assessing metal recovery from low-grade copper ores containing fluoride.(2011) Sicupira, Lazaro Chaves; Veloso, Tácia Costa; Gonzaga, Flávia Donária Reis; Leão, Versiane AlbisLow-grade ores are becoming increasingly important to metal production due to increasing metal prices and depletion of high-grade, low-impurity sources. Bioleaching can be an option to recover the metallic content present in these tailings. In this work, the bioleaching potential of a low-grade copper ore, containing chalcocite, bornite and chalcopyrite, was demonstrated with a Sulfobacillus thermosulfidooxidans strain, at 50 °C. Batch experiments were performed in shake flasks as well as a bioreactor (BioFlo 110), and the effects of pH, metal concentration and air flow rate on copper extraction were determined. The presence of fluoride in the gangue minerals resulted in up to 270 mg/L total fluoride in solution, which affected bioleaching. Fluoride toxicity was overcome with aluminium additions and resulted in high copper extraction (up to 100%) at pH 1.9. Speciation calculations were performed with on the aluminium-fluoride systems and indicated AlF2+ as the main complex in the system, whereas HF concentration was reduced to values below 10−4 mol/L, which seems to be the threshold for bacterial growth inhibition.Item High-temperature bioleaching of nickel sulfides : thermodynamic and kinetic implications.(2010) Cruz, Flávio Luciano dos Santos; Oliveira, Víctor de Andrade Alvarenga; Guimarães, Damaris; Souza, Adelson Dias de; Leão, Versiane AlbisThe effect of temperature on nickel sulfide bioleaching was studied in the presence of mesophile (Acidithiobacillus ferrooxidans) and moderate thermophile (Sulfobacillus thermosulfidooxidans) strains and the results were discussed in terms of sulfide dissolution thermodynamics (Eh–pH diagrams) and kinetics (cyclic voltammetry). It was observed that in the pH range 1.8–2.0 the highest nickel dissolution was achieved which reached 50% for mesophiles and over 80% for moderate thermophiles. External ferrous iron addition had no effect on the metal dissolution at 34 °C, but adversely affected nickel leaching at higher temperatures. The best outcomes were accomplished with low FeSO4 additions (2.5 g/L) at 50 °C. Pyrrhotite dissolution avoided the need for external iron addition, providing Fe2+ concentrations as high as 7 g/L during bioleaching, which supports bacterial growth. Eh–pH diagrams for pentlandite and pyrrhotite show a negligible effect of temperature on the stability field of each sulfide whilst cyclic voltammetry indicated that temperature has the strongest influence on pyrrhotite oxidation. The latter along with a rapid increase in solution potential (Eh) explains the higher and faster extraction observed with S. thermosulfidooxidans.Item The effect of ferrous and ferric iron on sphalerite bioleaching with Acidithiobacillus sp.(2005) Pina, Pablo dos Santos; Leão, Versiane Albis; Silva, Carlos Antônio da; Daman, Dominique; Frenay, JeanBioleaching has gained increased interest as an alternative for processing zinc sulfide ores without the generation of SO2. The bioleaching of sphalerite with mesophile microorganisms at 1% pulp density has been studied. Batch experiments were carried out at 34 °C and 200 rpm. The effects of pH, concentration of Fe(II), as well as the presence of Fe(III) in the zinc extraction were assessed. Fast zinc dissolution can be achieved working with Acidithiobacillus sp. The best pH for bioleaching is in the 1.75–2.00 range and the presence of Fe(III) has a strong influence in zinc extraction, increasing the rate of dissolution and does not adversely affect the growth of the Acidithiobacillus population.