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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2 resultados
Resultados da Pesquisa
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.Item Batch and fixed-bed assessment of sulphate removal by the weak base ion exchange resin Amberlyst A21.(2014) Guimarães, Damaris; Leão, Versiane AlbisThis paper investigated sulphate removal from aqueous solutions by Amberlyst A21, a polystyrene weakbase ion exchange resin. Both the pH and initial sulphate concentration were observed to stronglyaffect sorption yields, which were largest in acidic environments. Working under optimum opera-tional conditions, sulphate sorption by Amberlyst A21 was relatively fast and reached equilibrium after45 min of contact between the solid and liquid phases. Sorption kinetics could be described by eitherthe pseudo-first order (k1= 3.05 × 10−5s−1) or pseudo-second order model (k2= 1.67 × 10−4s−1), andboth the Freundlich and Langmuir models successfully fitted the equilibrium data. Sulphate uptake byAmberlyst A21 was a physisorption process ( H = −25.06 kJ mol−1) that occurred with entropy reduction(deltaS = −0.042 kJ mol−1K−1). Elution experiments showed that sulphate is easily desorbed (∼100%) fromthe resin by sodium hydroxide solutions at pH 10 or pH 12. Fixed-bed experiments assessed the effects ofthe initial sulphate concentration, bed height and flow rate on the breakthrough curves and the efficiencyof the Amberlyst A21 in the treatment of a real effluent. In all studied conditions, the maximum sulphateloading resin varied between 8 and 40 mg (SO42−) mL (resin)−1.