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 Reduction roasting and bioleaching of a limonite ore.(2021) Oliveira, Víctor de Andrade Alvarenga; Rodrigues, Michael Leonardo Marques; Leão, Versiane AlbisTwo of the main challenges presented by the implementation of nickel laterites atmospheric acid leaching are: (i) high acid consumption and (ii) high final iron concentrations in the PLS. In the current work, a novel process was devised by applying pyrometallurgical and bio-hydrometallurgical operations. The experimental set-up comprised the reduction of a nickel limonitic ore with hydrogen gas in a rotary kiln, at 900 ◦C, until all the goethite was converted to metallic iron. Subsequently, the reduced sample was bioleached by mesophilic microorganisms grown on Fe2+ (Acidithiobacillus ferrooxidans) at 5% solids, 32 ◦C, and pH < 3. The results showed that an increase in the Eh values, promoted by the bacteria, resulted in the leaching Fe, Ni and Co, therefore a dissolution of 92% of the nickel and 35% of the cobalt was observed in experiments carried out with 35 Kg H2SO4/(ton of the reduced ore). The iron concentration in the liquor generated under these experimental conditions was below 5 mg/L owing to the fact that Fe3+ precipitated as jarosite. The experimental conditions applied also resulted in low acid consumption and the final total iron concentration was also reduced in the leach liquor (< 200 mg/L), which were considerably lower than the values reported for the HPAL process.Item Multivariate study of a novel hydrometallurgical route employing chloride/hypochlorite for leaching silver from printed circuit boards.(2020) Pereira, Matheus Mello; Costa, Fabio Oliveira; Gomes, Rodrigo Ferreira; Rodrigues, Michael Leonardo Marques; Silva, Gilmare Antônia da; Leão, Versiane AlbisThe rapidly expanding use of electronic products has led to the generation of very large quantities of waste electrical and electronic equipment (WEEE). This waste essentially consists of polymeric, ceramic, and metallic materials, with the metal fraction including noble and base metals, which may be toxic. It is therefore important to recycle printed circuit boards (PCBs) for both economic and environmental reasons, especially since this solid waste contains noble metals (gold and silver). Given this background, the aim of the present work was to develop a hydrometallurgical route for leaching ofthe silver presentin computer PCBs, using a combination of sodium chloride and calcium hypochlorite as the lixiviants. Optimization was performed of the following independent variables: (i) pulp density, (ii) calcium hypochlorite concentration, (iii) sodium chloride concentration, and (iv) leaching time. Multivariate experimental designs were employed, consisting of a 24 full factorial design and response surface methodology with a spherical central composite design (CCD). The operational conditions were varied according to the mathematical equation obtained from the CCD, in order to find their best values which resulted in the maximum Ag extraction. The optimal conditions for the leaching of silver were a pulp density of 48 g L−1, calcium hypochlorite concentration of 165 g L−1, sodium chloride concentration of 65 g L−1, and extraction time of 200 min, resulting in 95.29 ± 0.72% extraction of silver. Silver was dissolved by forming complexes with chloride, being AgCl3− 4 (aq) the predominant specie. In summary, the hydrometallurgical route employed in this work enabled satisfactory and environmentally favorable extraction of silver.Item Recovering gold from mine tailings : a selection of reactors for bio-oxidation at high pulp densities.(2020) Rodrigues, Michael Leonardo Marques; Giardini, Romeu Marra Neto; Pereira, Igor J. U. V.; Leão, Versiane AlbisBiomining is one of the few cost-effective technologies that can be applied to low-grade ores and also mining tailings. In the current work, the bio-oxidation of a gold sulphide flotation tailing at high pulp densities was investigated and information for the high cyanide consumption commonly reported in bio-oxidative processes are discussed in order to promote less use of this chemical reagent during cyanidation. RESULTS: Different reactors were compared alongside the performance of strains of At. ferrooxidans and S. thermosulfidooxidans. Shaking flasks tests performed using 5% solids (w/v) revealed that the mesophiles presented a faster adaptation to the solids and resulted in better tailings oxidation as compared to the moderate thermophile. Rolling bottles (pilot scale rotating-drum) experiments, carried out afterwards, enabled the adaptation of the At. ferrooxidans strain to 20% solids (w/v). This adapted strain was thus utilized in a 10 litrestirred tank reactor (pilot scale stirred tank) experiment at the same pulp density. The concentration of the ferrous iron used in the bio-oxidation step had a detrimental effect on the cyanide consumption during cyanidation of the bio-oxidised material. The cyanide consumption varied from 6.9kg/t to 13.7kg/t as the initial Fe2+ concentration increased from 0.0g/L to 10.0g/L Fe2+, respectively in the shaking flasks. CONCLUSION: Higher pulp densities (20% solids (w/v)) resulted in a lower cyanide consumption, which was around 7.0kg/t in the experiments carried out in both rolling bottle and stirred tank reactor when 5.0g/L Fe2+ was used during bio-oxidation. This cyanide consumption was associated to a gold extraction around 95%.Item Column bioleaching of fluoride-containing secondary copper sulfide ores : experiments with Sulfobacillus thermosulfidooxidans.(2019) Rodrigues, Michael Leonardo Marques; Santos, Guilherme H. A.; Leôncio, Hamilton Cristiano; Leão, Versiane AlbisBioleaching is a mature technology, which is widely employed commercially in the leaching of primary sources of metals (ores, concentrates, and mine residues). The current work discussed the effects of aluminum sulfate additions to the growth medium, PLS recirculation and bleeding on the column bioleaching of secondary copper sulfide ores with a significant content of fluoride-containing minerals. Fluoride is toxic to bacteria at the pH of bioleaching but its toxicity may be overcome in the presence of soluble aluminum and ferric iron. Therefore, experiments were carried out in 10 × 100 cm height aerated columns, loaded with 10 kg of crushed and agglomerated copper ore and inoculated with Sulfobacillus thermosulfidooxidans. Initially, fluoride concentrations of up to 2.5 g/L in the pregnant leach solution were observed due to the fast dissolution of fluoride-bearing minerals. Aluminum was added to the leaching solution to reduce the Al/F ratio so that the concentration of HF (the main toxic species) was decreased, but while the total fluoride concentration was higher than that of aluminum, the bacterial population as low. Therefore, the current work emphasizes that it is possible to set up conditions to enable bioleaching even at high fluoride concentrations. Following this approach, copper extractions above 90% were achieved for a H2SO4 consumption ranging from 128.8 to 206.1 Kg/ton.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 Caracterização de talco purificado de resíduos de pedra sabão.(2014) Garcia, Neylor Henrique; Rodrigues, Michael Leonardo Marques; Lima, Margarida Márcia Fernandes; Lima, Rosa Malena FernandesNesse trabalho estão apresentados os resultados dos ensaios de caracterização de talco purificado de resíduos de pedra sabão, oriundos de Santa Rita de Ouro Preto, após lixiviação de concentrados de flotação com ditionito de sódio (Na2S2O4) e ácido clorídrico (HCl). A caracterização tecnológica desses materiais constou de análise granulométrica, efetuada por espalhamento de raios laser (Cilas 1064), difração de raios X (método do pó total), análises químicas, efetuadas por espectroscopia ótica de emissão-plasma de acoplamento indutivo além da determinação de alvura ISO. Para os concentrados de flotação lixiviados com ditionito de sódio e ácido clorídrico foram obtidas alvuras de 73,7 e 79,6%, respectivamente, representado aumento de 3 e 9% em relação a alvura do concentrado da flotação. Verificou-se que cerca de 80% das partículas das amostras de talco lixiviadas encontravam-se abaixo de 10 μm. Os minerais identificados nos difratogramas de raios X foram talco e clinocloro. O maior aumento da alvura do produto lixiviado com HCl, está relacionado com a diminuição dos teores de Fe2O3, Ni, Zn em relação à alimentação (concentrado da flotação).Item Purificação de resíduos de oficina de artesanato em pedra-sabão por flotação e alvejamento químico.(2011) Rodrigues, Michael Leonardo Marques; Lima, Rosa Malena FernandesNa região de Ouro Preto-MG, existem diversas oficinas de artesanato em pedra-sabão. Nessas oficinas, o processo de fabricação de panelas e objetos de adorno, produz uma grande quantidade de resíduos, que, normalmente, são depositados nas proximidades das oficinas, sem nenhuma forma de controle. Esse trabalho teve por objetivo recuperar o talco contido na fração granulométrica abaixo de 74μm desses resíduos através de purificação por flotação e alvejamento químico com HCl. Entre as variáveis estudadas na flotação, apenas a porcentagem de sólidos e a dosagem de espumante se mostraram significativas com relação às variáveis-respostas: recuperação mássica e alvura. Nesse processo, produziu-se um concentrado com alvura (ISO) de 68,56% e com composição química que está de acordo com as especificações de tinta (espalhador) e papel (carga). Após alvejamento químico do concentrado de flotação, foram obtidos alvura (ISO) de 84,0% e teores químicos que estão dentro das especificações da indústria de plásticos (carga e reforço) e plásticos antiaderentes.Item Cleaner production of soapstone in the Ouro Preto region of Brazil : a case study.(2012) Rodrigues, Michael Leonardo Marques; Lima, Rosa Malena FernandesSoapstone is a metamorphic rock that is used for ornamental and construction purposes. Rock recovery during the exploitation process is low. Quarries in the state of Minas Gerais in Brazil sell small and lowquality blocks to artisans, who produce pans and souvenirs. This activity constitutes the main economic activity in several places within the Ouro Preto region, such as Santa Rita. Soapstone artisan workshops produce a large quantity of powder (approximately 10e15% rock recovery), which is discarded carelessly, often causing environmental problems. The objective of this study was to characterise and purify soapstone powder from the workshop of an artisan who works exclusively with rocks from Bandeiras-Santa Rita de Ouro Preto in order to identify potential applications for the residues and purified products. First, the mineralogical composition was determined by X-ray diffractometry, the size distribution was determined by sieving and the chemical composition of the residue was determined by inductively coupled plasmaeoptical emission spectroscopy (ICP-OES). Next, purification tests were performed by magnetic separation for fraction sizes larger than 74 mm. Fraction sizes smaller than 74 mm were purified by flotation and leaching with hydrochloric acid. This research shows that it is possible to recover almost all residues of both small and large size distributions for use as insecticide filler. In addition, it is possible to recover 100% and 96% of fraction sizes larger and smaller than 74 mm, respectively, for use in the paper industry (wallpaper and packaging). For more valuable applications, it is necessary to leach the purified material from flotation using hydrochloric acid. In addition to decreasing the environmental impact of soapstone powder discharge, it is possible for soapstone artisans to sell this powder for a profit, whether it is purified or not.Item Caracterização tecnológica de resíduos de oficinas de artesanato de pedra sabão da região de Ouro Preto.(Programa de Pós-Graduação em Engenharia Mineral. Departamento de Engenharia de Minas, Escola de Minas, Universidade Federal de Ouro Preto., 2010) Rodrigues, Michael Leonardo Marques; Lima, Rosa Malena FernandesNa região de Santa Rita de Ouro Preto, distrito da cidade de Ouro Preto-MG, existem diversas oficinas de artesanato em pedra-sabão que através da utilização de tornos de madeira fabricam panelas e diversos objetos de adorno. O processo de fabricação desses objetos resulta na produção de uma grande quantidade de finos que, normalmente, são depositados próximo às oficinas sem nenhuma forma de controle. Este projeto se propôs em efetuar a caracterização tecnológica destes resíduos, bem como ensaios de purificação visando o aproveitamento econômico dos mesmos. A determinação da distribuição granulométrica dos resíduos foram efetuadas por peneiramento a úmido e análise em granulômetro a laser, para a fração granulométrica abaixo de 37 μm. Verificou-se que o d80 das amostras ensaiadas variou entre 550 a 1575μm. Na caracterização mineralógica dos finos utilizou-se a difração de raios X pelo método do pó total. As principais fases cristalinas identificadas foram: talco, tremolita, nimita, ilmenita, dolomita, magnetita, magnesita e quartzo na amostra proveniente de Cachoeira do Brumado. Já as amostras da região de Santa Rita de Ouro Preto, além do talco e da nimita, também foram detectados os minerais caolinita e clorita-serpentina. As análises químicas por ICP-OES detectaram a presença de elevados teores de impurezas tais como Fe2O3 e Al2O3 nas amostras analisadas impossibilitam o uso dos resíduos de pedra sabão, sem prévia purificação, para destinações industriais mais nobres. Com base nas análises dos dados, pode-se deduzir a presença de: calcopirita, rodocrosita e arsenopirita. O resíduo de pedra-sabão (amostra global) e fração granulométrica abaixo de 74μm possuem especificações químicas para serem usados na fabricação de inseticidas, têxteis, fertilizantes e rações (veículo). O potencial zeta do talco puro apresentou o PZC em um pH de 2,3. Com relação aos métodos de purificação, utilizaram-se as técnicas de separação magnética de alta intensidade, mesa vibratória, flotação e alvejamento químico. Utilizaram-se ferramentas estatísticas do software MINITAB a fim de se analisar variáveis que possam apresentar influências significativas nesses processos. Dentre esses, os processos de flotação utilizando querosene (coletor), metassilicato de sódio (depressor) e MIBC (espumante) e alvejamento com HCl apresentaram os melhores valores de alvura, gerando concentrados de 71,81% (ISO) e 86,5% (ISO) respectivamente e adequando também estes produtos às especificações para tintas (espalhador), papel (carga), de plásticos (carga e reforço) e plásticos antiaderentes.