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 Adsorption of gaseous elemental mercury on soils : influence of chemical and/or mineralogical characteristics.(2019) Montoya, Juan Andres; Lena, Jorge Carvalho de; Windmoeller, Claudia CarvalhinhoGaseous elemental Hg is stable enough to be transported over long distances. Some of the most important sources of Hg in the atmosphere are artisanal gold mining activities and forest fires. Both of these sources are particularly prevalent in the Amazonia region. Information regarding the capacity of soils for retaining Hg transported by the atmosphere is very important for understanding the metal cycle in the environment. The aim of this work was to study gaseous elemental Hg adsorption in soils with different physical and chemical characteristics. For this purpose, soils from different regions in Brazil and Colombia influenced or possibly influenced by gold mining activities and forest fires were studied. Hg adsorption tests were conducted by exposing soil samples to a gaseous elemental Hg atmosphere for 144 h. The total Hg concentration (THg) and Hg oxidation states were monitored using a direct Hg analyzer. Sample characterization analyses were performed. THg values obtained before the adsorption tests were 43–413 and 144–590 µg kg−1 for grain size fractions below 2 and 0.063 mm, respectively. The predominant species found was Hg2+, with abundance levels from 68% to 99%. The results show a wide range of enhanced Hg retention capacities among the samples, ranging from 13 to 2236 times the initial concentration, and the speciation results demonstrate a decrease in the oxidized species range, from 21% to 78%. The statistical analysis indicated the importance of Mn-bearing minerals for the processes of adsorption/oxidation of gaseous elemental Hg in soils. These results contribute to the elucidation of the processes that occur with Hg at the soil/atmosphere interface and may help to explain the high concentrations of Hg found in Amazonian soils where no gold mining activities are practiced.Item Caracterização tecnológica de uma zeólita exaurida, para remoção de íons Mn2+.(2017) Gonzaga, Flávia Donária Reis; Leão, Versiane Albis; Cunha, Emmanoelle Cintra daAs zeólitas apresentam importante propriedades fisico-químicas que aliadas a sua disponibilidade e seu baixo custo viabilizam sua aplicação em vários processos industriais. Atualmente tem-se dado enfoque para utilização de zeólitas na adsorção de metais no tratamento de água e de efluentes industriais. Assim, o presente trabalho teve como objetivo a caracterização tecnológica de uma zeólita, visando atestar a viabilidade de sua utilização na remoção de íons Mn2+(aq) em diferentes condições experimentais. O material utilizado neste trabalho era uma zeólita sintética exaurida utilizada como catalisador no craqueamento de petróleo. Inicialmente, realizou-se a ativação da zeólita com solução de NaOH, 1 mol.L-1. Em seguida, foi feita a caracterização da mesma e sua aplicação nos ensaios de adsorção com solução sintética de Mn2+ a 50 mg.L-1, realizados em batelada. Foram investigados valores de pH entre 4 e 8, e temperatura entre 25°C e 70°C. Observou-se que a zeólita foi identificada, por difração de raios-X, como Faujasita. O pH ótimo de adsorção sem risco de remoção por precipitação foi de 6,5 e a melhor temperatura, 25°C. O tempo de equilíbrio da adsorção do Mn2+(aq) por adsorção foi de 4 horas. Nessas condições, obteve-se um carregamento de 10,8 mg Mn2+-g zeólita. Os resultados mostraram o potencial de aplicação deste material para processos de remoção de íons manganês presentes em soluções aquosas.Item Batch removal of manganese from acid mine drainage using bone char.(2014) Sicupira, Dalila Chaves; Silva, T. Tolentino; Leão, Versiane Albis; Mansur, Marcelo BorgesThe present study investigated batch kinetics and the batch equilibrium of manganese removal from acid mine drainage (AMD) using bone char as an adsorbent. Equilibrium tests revealed that the Langmuir-based maximum manganese uptake capacity was 22 mg g-1 for AMD effluents and 20 mg g-1 for laboratory solutions at a pH ranging from 5.5 to 5.7. The pseudo-second order model best described the manganese kinetics within bone char. Manganese removal was mainly influenced by the operating variables of the solid/liquid ratio and the pH of the aqueous phase. In fact, metal uptake was favored at nearly neutral pH values. The effect of particle size and temperature proved to be insignificant for the investigated operating range. This work also evaluated the mechanism for manganese removal using bone char. Results showed that intraparticle diffusion is the main rate-limiting step; however, additional contributions from boundary layer diffusion may well affect this removal when particles of smaller sizes are used. The final concentration of fluoride and other metals present in the AMD effluent was in agreement with the concentration limit set forth by Brazilian legislation. The present study demonstrated that bone char is a suitable material to be used for the removal of manganese from AMD effluents.