EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
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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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Item Lixiviação ácida de elementos terras raras presentes em resíduos de equipamentos elétricos e eletrônicos : uma breve revisão.(2022) Gomes, Rodrigo F.; Pereira, Matheus Mello; Leão, Versiane AlbisThe accelerated expansion of the use of electronic products has generated large amounts of Waste Electrical and Electronic Equipment (WEEE), which makes the use of management strategies based on Circular Economy (CE) essential. In this sense, the recycling of these residues is of great interest due to the presence of metals with high added value, such as Rare Earth Elements (REE). Given the above, this review aims to elucidate issues related to the management and processing of WEEE and to evaluate the main parameters that influence the leaching step of REE present in these wastes. From the critical analysis of the bibliographic survey, it was noted that fluorescent lamps, cathode-ray tubes, NbFeB magnets and NiMH batteries are widely studied, with the objective of recovering REE. However, considerable variations were observed with regard to the content of metals present in each of these residues. In short, it is important that the recovery of these metals is studied, not only due to economic aspects, but also aiming at environmentally sustainable recycling.Item Incorporation of quartzite fines in the production of red ceramics.(2021) Silva, Mariana Caroline Andrade; Leão, Versiane Albis; Reis, Érica LinharesThe ornamental stone sector produces a substantial amount of solid waste and effluents that are discarded in a disorderly manner, a fact that has prompted the need for research aimed at reuse. Considering the concepts of sustainable development and conscious mining, this study proposed the incorporation of quartzite residues in the production of ceramics (using soil as raw material) and aimed to reduce production prices, minimize environmental impacts, and obtain a higher quality of ceramic products (with less water absorption and greater resistance). Ceramic bricks were made in accordance with the following variables: replacement percentage (10% and 15%), compaction pressure (28 and 35 MPa), drying temperature (65 C for 72 h and 110 C for 24 h), and firing temperature (950 and 1100 C). Technological tests evaluated the drying and firing linear shrinkage, firing specific weight, water absorption, and resistance to uniaxial compression. After determining the optimal conditions, a flexural tear test and microstructural characterization were also performed. The optimal conditions for making ceramic bricks were a replacement percentage of 15%, compaction pressure of 35 MPa, drying temperature of 65 C (72 h), and firing temperature of 1100 C. These results were favorable because of the partial thermal decomposition of the mineral phases with the recrystallization of mullite and cristobalite. The incorporation of the residue resulted in better quality ceramic products, placing them within the limits established for technological applications, whereas none of the compositions made entirely of clay met the technical specifications.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 Producing electrical energy in microbial fuel cells based on sulphate reduction : a review.(2020) Rodrigues, Isabel Cristina Braga; Leão, Versiane AlbisCombination of the treatment of effluents with high organic loads and the production of electricity is the driving forces stimulating the development of microbial fuel cells (MFC). The increase in electricity production in MFCs requires not only the optimization of the operational parameters but also the inhibition of the metabolic pathways, which compete with electricity production, such as methanogenesis. The presence of both sulphate and sulphide ions in conventional anaerobic reactors hampers the growth of methanogenic archaea and justifies the use of sulphate and therefore sulphate-reducing bacteria (SRB) in the anodic half-cell of MFC. Most importantly, the literature on the subject reveals that SRB are able to directly transfer electrons to solid electrodes, enabling the production of electrical energy. This technology is versatile because it associates the removal of both sulphate and the chemical oxygen demand (COD) with the production of electricity. Therefore, the current work revises the main aspects related to the inoculation of MFC with SRB focusing on (i) the microbial interactions in the anodic chamber, (ii) the electron transfer pathways to the solid anode, and also (iii) the sulphate and COD removal yields along with the electricity production efficiencies.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 Effect of magnesium species on cationic flotation of quartz from hematite.(2020) Lelis, Deisiane Ferreira; Lima, Rosa Malena Fernandes; Rocha, Geriane Macedo; Leão, Versiane AlbisIn the Quadrilátero Ferrífero Region, located in the state of Minas Gerais – Brazil, the utilization of recycled water from the tailing dams in the reverse cationic flotation of siliceous iron ores is common practice. In such process, ore concentrates assigning dolomite (2.5% to 10%) besides quartz in the mineral gangue, do not reach the desired specification for the production of blast furnace pellets (≤2% SiO2) given the loss of selectivity occurring in the separation of quartz from the Fe-bearing minerals, which can be related to a rise in the ions Ca and Mg in an aqueous medium resulting from the dissolution of dolomite. With a view to improving the reverse cationic flotation route for this type of ore, fundamental studies (microflotation trials, zeta potential, adsorption/Fourier-transform infrared spectroscopy) into the effect of the Ca and Mg ions in the cationic flotation with the use of pure quartz and hematite mineral samples were carried out. The results attained with the Ca ions were presented in previous studies by the authors. The current investigation presents the results achieved with the Mg ions, added in water as MgCl2. In the microflotation trials carried out at pH 10.5, amine dosage for maximum recovery of quartz (2.5 ppm) and hematite (50 ppm) was applied. A strong depression of hematite by starch was confirmed, which did not occur with quartz. In the case of the Mg ions, a stronger depression effect was observed, if compared to starch, for the two minerals, starting from a dosage of 10 ppm of MgCl2. After the conditioning of both minerals with 10 ppm of MgCl2, followed by conditioning with 10 ppm of starch, the recoveries attained were negligible (3.5% to 4.4%). Based on thermodynamic data, zeta potential measurements, and infrared spectroscopy, it was concluded that the strong depression effect caused by the Mg ions on both minerals owes to the adsorption of the Mg2+ and MgOH+ species and also the precipitation of Mg(OH)2, where the starch is chemically adsorbed, preventing further amine adsorption. Only quartz recovery was reestablished after the complexation of the Mg ions in the water by ethylenediaminetetraacetic acid having close molar concentrations to the molar concentration of the Mg ions followed by starch conditioning. The results presented indicate the need for a reduction in the concentration of Mg in the water used, before flotation is conducted.Item Kinetics of copper and cadmium cementation by zinc powder.(2019) Oliveira, Víctor de Andrade Alvarenga; Penna, José Márcio Soares; Magalhães, Lucas Sanches; Leão, Versiane Albis; Santos, Claudio Gouvea dosThe cementation of copper and cadmium by zinc powder was investigated in order to assess the influence of different parameters in the process. The results showed that the process follows a first order reaction with two stages in both systems. In the system Cu/Zn, the second stage is faster than the first while in the system Cd/Zn the second stage is slower than the first. In the system Cu/Zn, the variation on the surface area of copper cement followed a power law and a straight line was obtained by plotting –ln([Cu2+]/[Cu2+] 0 ) against t3/2, the activation energy was calculated as 16.3kJ. In the system Zn/Cd the surface area available for reaction decreased as a result of the cement agglomeration. On the experiments carried out with ions Cu2+ and Cd2+ in solution, purer copper cement was obtained when the experiments were carried out in the presence of less than stoichiometric amount of zinc powder and longer reaction times.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 Precipitation of a layered double hydroxide comprising Mg2+ and Al3+ to remove sulphate ions from aqueous solutions.(2018) Guimarães, Damaris; Rocha, Natasha Cristina Machado da; Morais, Rafaela Aparecida Pedro de; Resende, Andréia De-Lazarri Bicalho Peixoto; Lima, Rosa Malena Fernandes; Costa, Geraldo Magela da; Leão, Versiane AlbisThis work presents an alternative route to remove sulphate ions from aqueous solutions, which is simple and fast, and its efficiency of sulphate removal is slightly influenced by temperature (26 °C–70 °C) and pH (4–12). The lowest residual sulphate concentration was about 60 mg L−1, which was observed in continuous experiments using wastewater (26 °C, pH 6 and initial sulphate concentration of 630 mg L−1). All these outcomes together have not been observed in the current most used processes of sulphate precipitation, i.e. gypsum and ettringite precipitation. Sulphate removal experiments were carried out in the batch and continuous systems using synthetic solutions. In these conditions, about 75% of sulphate ions were removed for an initial ion concentration of 1800 mg L−1. A continuous test was also performed using a wastewater sample in addition to a synthetic solution. The system reached steady-state conditions after four residence times (40 min) in the experiment with synthetic solutions, whereas three residence times (30 min) were necessary for the tests with the wastewater (initial sulphate concentration of 630 mg L−1). In the latter case, the sulphate removal efficiency was approximately 90%. The characterisation of the experimentally precipitated solids was carried out by DRX, FTIR, SEMEDS, elemental analysis and thermal analysis. These techniques showed that, except in pH 4, the sulphate removal process occurred due to the precipitation of a layered double hydroxide, comprising Mg2+ and Al3+ as its metallic ions and nitrate (due to the salts used for precipitation) and sulphate anions occupying its interlayer space.