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 Fundamental aspects related to batch and fixed-bed sulfate sorption by the macroporous type 1 strong base ion exchange resin Purolite A500.(2014) Guimarães, Damaris; Leão, Versiane AlbisAcid mine drainage is a natural process occurring when sulfide minerals such as pyrite are exposed to water and oxygen. The bacterially catalyzed oxidation of pyrite is particularly common in coal mining operations and usually results in a low-pH water polluted with toxic metals and sulfate. Although high sulfate concentrations can be reduced by gypsum precipitation, removing lower concentrations (below 1200 mg/L) remains a challenge. Therefore, this work sought to investigate the application of ion Exchange resins for sulfate sorption. The macroporous type 1 strong base IX resin Purolite A500 was selected for bath and fixed-bed sorption experiments using synthetic sulfate solutions. Equilibrium experiments showed that sulfate loading on the resin can be described by the Langmuir isotherm with a maximum uptake of 59 mg mL-resin 1. The enthalpy of sorption was determined as þ2.83 kJ mol^-1, implying an endothermic physisorption process that occurred with decreasing entropy (-15.5 J mol^-1.K^-1). Fixed-bed experiments were performed at different bed depths, flow rates, and initial sulfate concentrations. The Miura and Hashimoto model predicted a maximum bed loading of 25 e 30 g L-bed-1 and indicated that both film diffusion (3.2 x 10^-3 cm s-1 to 22.6 x 10^-3 cm s^-1) and surface diffusion (1.46 x 10^-7 cm2 s^-1 to 5.64 x 10^-7 cm2 s^-1) resistances control the sorption process. It was shown that IX resins are an alternative for the removal of sulfate from mine waters; they ensure very low residual concentrations, particularly in effluents where the sulfate concentration is below the gypsum solubility threshold.Item Treatment of high-manganese mine water with limestone and sodium carbonate.(2012) Silva, Adarlêne Moreira; Cunha, Emmanoelle Cintra da; Gonzaga, Flávia Donária Reis; Leão, Versiane AlbisManganese is one of the most difficult elements to remove from mine waters, due to its high solubility in both acid and neutral conditions; thus it can be found in quite high concentrations, depending on the rock’s mineralogy. Metal carbonate precipitation can be an effective way for its removal, as manganese carbonate has been detected in net alkaline mine waters. However, limestone is effective in removing manganese only if the metal content is low. This research sought to study manganese precipitation from high-manganese (140 mL) content mine waters applying sodium carbonate and limestone mixtures. It was observed that besides the total carbonate concentration, pH plays a key role on manganese carbonate formation. Provided the pH solution is above 8.5, 99.9% manganese removal can be achieved with carbonate ions. Although not required for manganese precipitation, limestone acts as a solid substrate for the nucleation of fine manganese carbonate grains. Infrared spectroscopy showed manganese carbonate precipitation on the limestone surface. Magnesium was also removed from the mine water but magnesium carbonate formation was not observed.Item Mine water treatment with limestone for sulfate removal.(2012) Silva, Adarlêne Moreira; Lima, Rosa Malena Fernandes; Leão, Versiane AlbisLimestone can be an option for sulfate sorption, particularly from neutral mine drainages because calcium ions on the solid surface can bind sulfate ions. This work investigated sulfate removal from mine waters through sorption on limestone. Continuous stirred-tank experiments reduced the sulfate concentration from 588.0 mg/L to 87.0 mg/L at a 210-min residence time. Batch equilibrium tests showed that sulfate loading on limestone can be described by the Langmuir isotherm, with a maximum loading of 23.7 mg/g. Fixed-bed experiments were utilized to produce breakthrough curves at different bed depths. The Bed Depth Service Time (BDST) model was applied, and it indicated sulfate loadings of up to 20.0 g (SO4)2− /Lbed as the flow rate increased from 1 to 10 mL/min. Thomas, Yoon–Nelson and dose–response models, predicted a maximum particle loading of 19 mg/g. Infrared spectrometry indicated the presence of sulfate ions on the limestone surface. Sulfate sorption on limestone seems to be an alternative to treating mine waters with sulfate concentrations below the 1200–2000 mg/L range, where lime precipitation is not effective. In addition, this approach does not require alkaline pH values, as in the ettringite process.