ABSTRACT
RESUMO O presente trabalho teve por objetivo verificar uma possível rota de reciclagem para as éter-aminas, utilizadas para aumentar a eficiência do processo de flotação catiônica reversa do minério de ferro. Estudou-se um método de separação físico-química utilizando TANFLOC como floculante. As águas de rejeito contêm, em sua maior parte, amina e sílica, e o objetivo desse método era separar a sílica do rejeito. A separação físico-química, porém, não foi eficaz, visto que o processo não foi capaz de flocular somente a sílica, floculando também parte da éter-amina. Foi avaliado também o processo de adsorção e, para tanto, utilizaram-se como materiais adsorventes a serragem Angelim e bagaço de cana-de-açúcar, ambos in natura. Esses materiais foram capazes de remover aproximadamente 95 e 90% de éter-amina, com capacidades adsortivas de 4,2 e 2,7 mg.g-1, respectivamente, utilizando massa de 1,5 g e estabelecendo tempo de equilíbrio de 30 minutos. Verificou-se que a eficiência de remoção é maior em pH próximo a 10. Pelos estudos termodinâmicos foi possível concluir, para a serragem, que o processo é termodinamicamente favorável e exotérmico. Para o bagaço de cana não foi possível analisar o comportamento termodinâmico. Além disso, o processo de dessorção permitiu recuperar em torno de 80% de éter-amina, além da possibilidade de regeneração e reutilização dos materiais adsorventes, o que mostra a viabilidade de reciclar a éter-amina pelo mecanismo de adsorção.
ABSTRACT The present work has the objective of investigating the possible recycling route for ether-amines, used for improving the efficiency of the process of iron ore's reverse flotation. A physical-chemical separation method has been studied using TANFLOC as flocculant. The wastewater contains, mainly, amine and silica, and the objective of this method was to separate the silica from the waste by flocculation. However, this method was not effective, as flocculation was not able to flocculate only silica, but also part of the ether-amine. Furthermore, the process of adsorption was assessed, and for this it was used as materials adsorbents Angelim's sawdust and sugar cane bagasse, both in natura, with which it was possible to remove approximately 95 and 90% of ether-amines, with adsorptive capacity of 4,2 and 2,7 mg.g-1, respectively, by using a mass of 1.5 g and a settling time of 30 minutes. It was verified that the removal efficiency is greater at a pH around 10. Thermodynamic studies were carried out and they were able to state, for sawdust, that this process is thermodynamically favorable and exothermic. In the case of sugar cane bagasse, it was not possible to analyze its thermodynamic behavior. In addition, the use of desorption revealed the possibility of regaining around 80% of the ether-amines. This proved that it is possible to recycle ether-amines by the adsorption mechanism.
ABSTRACT
Because of its precision and accuracy, Pb-Fire assay is the most employed method for gold analysis in geological materials. At the second stage of the method, namely cupellation, lead is oxidized to PbO which is absorbed by the cupel, leading to metallic gold as a tiny bend at the bottom of the recipient. After cupellation, cupel becomes highly contaminated with lead, making its disposal a serious risk of environmental contamination. In the present work, a leaching process for removing lead from cupel waste is proposed, which allowed for removing 96% of PbO by weight. After a precipitation step, 92.0% of lead was recovered from leachates in the form of PbSO4. Lead in the solid wastes left by the extraction was above the limit established by Brazilian legislation and these were classified as non-hazardous. Finally, secondary effluents generated after the precipitation step presented lead content more than twenty times lower than that of leachates from cupel waste. Tons of cupel waste are annually generated from gold analysis by Pb-Fire assay. Thus, the proposed method can contribute to prevent the discharge of high amounts of lead into the environment. Also, recovery of lead can help to partially meet the industrial demand for lead compounds.
