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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Resultados da Pesquisa
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 Remoção de metais pesados em resíduos sólidos : o caso das baterias de celular.(2005) Souza, Ronie Magno P.; Leão, Versiane Albis; Pina, Pablo dos SantosNo presente trabalho, estudou-se a recuperação de níquel, cádmio e cobalto presentes em baterias recarregáveis, através de técnicas hidrometalúrgicas. Experimentos de lixiviação, realizados à temperatura de 25ºC e com relação sólido/líquido de 1/10, mostraram que podem ser obtidos rendimentos de lixiviação acima de 90% para os metais desejados em 2h de ensaio e trabalhando-se com uma solução contendo ácido sulfúrico e ácido nítrico, nas respectivas concentrações de 2mol/L e 0,5mol/L. Em seguida, foi estudada a separação seletiva dos metais por extração por solventes. Nessa etapa, realizada a 25ºC e com uma relação fase aquosa/fase orgânica de 1/1, estudou-se a influência do pH sobre a seletividade dos extratantes D2EHPA e CYANEX 272 na extração de cada metal em questão. Verificou-se que em pH 2,5, trabalhando-se com o extratante D2EHPA, consegue-se extrair 90% de cádmio, 10% de cobalto e não há extração de níquel. Para o extratante CYANEX 272, em pH 5,5, conseguem-se extrações acima de 95% do cádmio e do cobalto e, aproximadamente, 5% de extração de níquel. Portanto um esquema de separação envolveria o extratante D2EHPA para separar cádmio do níquel e do cobalto e, em seguida, o extratante CYANEX 272 seria usado para separar níquel e cobalto. Excelentes resultados foram obtidos mostrando a viabilidade do processo e da metodologia empregada.Item Tecnologia limpa para redução de impacto ambiental do cianeto na mineração de ouro.(2007) Riani, Josiane Costa; Pina, Pablo dos Santos; Leão, Versiane AlbisEsse trabalho discute a aplicação de resinas de troca iônica com matriz poliacrílica para a adsorção de cianocomplexos metálicos. Ensaios em batelada mostraram que as resinas possuem elevada afinidade para os cianocomplexos de ferro e de zinco em relação aos de cobre. Já a eluição, estudada em coluna, indicou que soluções de tiocianato de sódio a 1mol/L são capazes de eluir os ciancomplexos dos três metais. Já soluções de nitrato de sódio, na mesma concentração, não são efetivas para a eluição do cianeto de zinco. Um processo de eluição seletiva é proposto onde os cianocomplexos de cobre e de ferro são eluídos com solução íons NO3 -. Em seguida, o zinco é eluído com NaSCN. Ambos eluentes foram capazes de concentrar os cianocomplexos de solução, o que tem efeito benéfico nas etapas subseqüentes de regeneração do cianeto.Item Effect of iron in zinc silicate concentrate on leaching with sulphuric acid.(2009) Souza, Adelson Dias de; Pina, Pablo dos Santos; Santos, Fabiano Mariel Fernandes dos; Silva, Carlos Antônio da; Leão, Versiane AlbisIt is shown that the iron content in zinc silicate concentrates with either high (8–11%) or low (3%) iron does not significantly affect the kinetics or overall recovery of zinc extraction in sulphuric acid. Most of the iron was present as hematite and franklinite with little iron contained in willemite. A small reduction in zinc recovery from 98.5% to 97.5% was observed for silicate ores containing 12% iron. The activation energy determined from high-iron concentrate leaching, 78±12 kJ/mol, is statistically similar to that from low-iron concentrate, 67±10 kJ/mol, suggesting the same rate-controlling step. The leaching of high high-iron concentrates enables a higher mass recovery during flotation. A flowsheet is proposed comprising a magnetic separation step to produce a magnetic and a non-magnetic product so that iron dissolution from the magnetic concentrate acts as a source of soluble iron for impurities removal.Item Kinetics of ferrous iron oxidation by Sulfobacillus thermosulfidooxidans.(2010) Pina, Pablo dos Santos; Oliveira, Víctor de Andrade Alvarenga; Cruz, Flávio Luciano dos Santos; Leão, Versiane AlbisThe biological oxidation of ferrous iron is an important sub-process in the bioleaching of metal sulfides and other bioprocesses such as the removal of H2S from gases, the desulfurization of coal and the treatment of acid mine drainage (AMD). As a consequence, many Fe(II) oxidation kinetics studies have mostly been carried out with mesophilic microorganisms, but only a few with moderately thermophilic microorganisms. In this work, the ferrous iron oxidation kinetics in the presence of Sulfobacillus thermosulfidooxidans (DSMZ 9293) was studied. The experiments were carried out in batch mode (2L STR) and the effect of the initial ferrous iron concentration (2–20 g L−1) on both the substrate consumption and bacterial growth rate was assessed. The Monod equation was applied to describe the growth kinetics of this microorganism and values of max and Ks of 0.242 h−1 and 0.396 g L−1, respectively, were achieved. Due to the higher temperature oxidation, potential benefits on leaching kinetics are forecasted.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.Item A kinetic study of the sulphuric acid leaching of a zinc silicate calcine.(2007) Souza, Adelson Dias de; Pina, Pablo dos Santos; Lima, Ermani Vinicius de Oliveira; Silva, Carlos Antônio da; Leão, Versiane AlbisRecent developments of acid leaching and solvent extraction of zinc silicate ores have produced renewed commercial interest. However, the leaching kinetics of these concentrates has received little attention. This work, therefore, addresses the leaching of a zinc silicate concentrate in sulphuric acid. The effects of particle size (0.038–0.075mm), temperature (30–50°C) and initial acid concentration (0.2–1.0mol/L) were studied. The results show that decreasing the particle size while increasing the temperature and acid concentration increase the leaching rate. As leaching occurs, there is a progressive dissolution of willemite whil e the quartz and iron-containing phases remain inert. Among the kinetic models of the porous solids tested, the grain model with porous diffusion control successfully described the zinc leaching kinetics. The model enabled the determination of an activation energy of 51.9 ± 2.8kJ/mol and a reaction order of 0.64 ± 0.12 with respect to sulphuric acid, which are likely to be a consequence of the parallel nature of diffusion and chemical reaction in porous solids.Item The leaching kinetics of a zinc sulphide concentrate in acid ferric sulphate.(2007) Souza, Adelson Dias de; Pina, Pablo dos Santos; Leão, Versiane Albis; Silva, Carlos Antônio da; Siqueira, Priscila de FreitasThis work examines the dissolution kinetics of an iron–rich zinc sulphide concentrate in acid ferric sulphate medium. The effects of temperature, ferric ion and sulphuric acid concentrations, agitation speed and particle size on the leaching kinetics were investigated. The leaching process could be separated into two stages. Initially, the dissolution kinetics was controlled by the chemical reaction at the surface of the zinc sulphide particles followed by a second step where the reaction was controlled by diffusion of the reagents or products through the elemental sulphur (ash) layer. The activation energy of the chemical controlled step was 27.5 kJ/mol and the value determined for the diffusion controlled step was 19.6 kJ/mol. The reaction order with respect to ferric ion and sulphuric acid concentrations were approximately 0.50 and 1.00, respectively. Analysis of the unreacted and reacted sulphide particles by SEM-EDS showed a progressive increase of the thickness of the elemental sulphur layer on the solid surface. The development of this sulphur layer is further evidence of the change on the rate-controlling step as the reaction progress.Item The kinetics of zinc silicate leaching in sodium hydroxide.(2010) Santos, Fabiano Mariel Fernandes dos; Pina, Pablo dos Santos; Porcaro, Rodrigo Rangel; Oliveira, Víctor de Andrade Alvarenga; Silva, Carlos Antônio da; Leão, Versiane AlbisThe alkaline leaching kinetics of a zinc silicate ore assaying 34.1% Zn, 11.1% Fe and 22.9% SiO2 is studied in sodium hydroxide solutions. Speciation diagrams indicate zinc dissolution as [Zn(OH)4]2− and SEM analysis showed a progressive reduction in particle size during leaching which supports the shrinking particle model. The process is chemically controlled with an activation energy of 67.8±9.0 kJ/mol and reaction order with respect to NaOH determined as 1.44±0.46.