Navegando por Autor "Brocchi, Eduardo de Albuquerque"
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Item Assessing the influence of NaCl on the reduction of a siliceous laterite nickel ore under Caron process conditions.(2019) Oliveira, Víctor de Andrade Alvarenga; Santos, Claudio Gouvea dos; Brocchi, Eduardo de AlbuquerqueThe reduction by hydrogen and the thermal decomposition of a siliceous nickel laterite ore in the presence of NaCl were studied using thermogravimetric analysis (TGA). Reduction tests on H2 atmosphere in rotary kiln were performed in the presence of NaCl and the product of the reaction was leached in ammoniacal solution. The presence of only 1 pct of NaCl in the furnace increased the nickel extraction values from ≈ 3 to ≈ 90 pct when the experiment was carried out at 850 °C. According to the results of X-ray diffractometry and TGA, the presence of NaCl in the system and the reducing atmosphere of H2 promote the segregation of nickel according to the following steps: (1) Nickel oxide reduction by hydrogen: NiO + H2(g) → Ni + H2O(g). (2) Formation of HCl: Al2SiO5 + 2NaCl + SiO2 + H2O → 2HCl(g) + 2NaAlSiO4. (3) Chlorination of metallic nickel by HCl: Ni + 2HCl(g) → NiCl2 + H2(g). (4) Reduction of nickel chloride by hydrogen: NiCl2 + H2(g) → Ni + 2HCl(g).Item On the cobalt content upgrade in nickeliferous laterites using iron (III) sulfate : a study based on thermodynamics simulations.(2022) Souza, Rodrigo Fernandes Magalhães de; Tavares, Mariana Aguiar de Azevedo; Cruz, Luiz Eduardo Carnevale; Oliveira, Víctor de Andrade Alvarenga; Santos, Iranildes Daniel dos; Moura, Francisco José; Brocchi, Eduardo de AlbuquerqueNickel (Ni) and cobalt (Co) are relevant technological metals for the future of the lithium-ion battery (LIB) industry. Based on the current and projected demand for these, an increased interest in developing processing routes to exploit lateritic occurrences has been observed, as these are reported as critical raw materials for future mineral–metallurgical industry. However, the content of Ni and Co in such ores is minimal and requires impracticable mineral-processing operations for concentration before metal extraction. It was identified that information regarding the sulfation roasting of this material is scarce on what concerns the iron sulfates interaction as a function of the temperature. Based on that context, the present work has its purposes associated with the proposition of an alternative chemical pretreatment to upgrade the content of metals of technological interest in lateritic ores through a simple roast–leach process. Thus, the chemical interactions between the mineral sample and iron (III) sulfate (Fe2 (SO4 )3 ) through thermodynamic simulations and experimental procedures were explored. The latter included specific water leaching practices for the selective concentration of metals. The equilibrium calculations indicate that Fe2 (SO4 )3 and FeSO4 tend to decompose at lower temperatures, and considering the higher stability of other metal sulfates, it could be an interesting reagent in this type of process. Regarding the experimental results, the characterization of materials indicates a recovery of Co as high as 73.4 wt.% after sulfation roasting at 500 ◦C followed by water leaching, with the full content of Iron (Fe) being reported in the insoluble phase. Based on these findings, the present development could be an interesting alternative to consider within operations for the chemical upgrade of cobalt in such types of mineralogical occurrences.Item Synergistic effect between CeO2 nanowires and gold NPs over the activity and selectivity in the oxidation of thioanisole.(2021) Rosado, Taíssa F.; Teixeira, Moisés Paulo; Moraes, Leonardo César de; Silva, Leonardo A. da; Silva, Augusto V. Pontes; Taylor, Jason Guy; Freitas, Isabel Cristina de; Oliveira, Daniela Coelho de; Gardener, Jules; Solorzano, Guilhermo; Alves, Tiago Vinicius; Venancio, Mateus Fernandes; Silva, Maria Isabel Pais da; Brocchi, Eduardo de Albuquerque; Fajardo, Humberto Vieira; Silva, Anderson Gabriel Marques daGold nanoparticles incorporated on ceria nanowires have been employed as efficient nanocatalysts for the se lective oxidation of thioanisole. The control of both physical and chemical parameters as well as metal–support interactions are important factors that determine their performances. Considering their one-dimensional morphology with large surface area, thin diameters, high concentration of oxygen vacancies, and small Au NPs uniformly on the entire CeO2 surface with a high fraction of oxidized gold species, these characteristics make them favorable nanocatalysts for oxidation transformations. The CeO2-Au nanowires displayed improved per formances towards the oxidation of thioanisole when compared to the pure CeO2 nanowires and commercial CeO2-Au catalysts. The CeO2-Au nanowires catalyzed the selective synthesis of methyl phenyl sulfoxide with up to 100 % of selectivity and high conversion. The impact of solvent and temperature during the catalytic reaction was also experimentally and theoretically investigated by DFT calculations, indicating a key role in the observed activities.