Time filter

Source Type

Rio de Janeiro, Brazil

Castilhos Z.C.,Center for Mineral Technology
One Century of the Discovery of Arsenicosis in Latin America (1914-2014): As 2014 - Proceedings of the 5th International Congress on Arsenic in the Environment | Year: 2014

The objective of this study was to estimate the potential risk on the health of residents of Paracatu (adults and children) due exposure to arsenic present in soil, water, air and food. For the assessed receptors, the risk due to the present contamination scenario was higher than the limit considered acceptable. The main pathways were ingestion of water while swimming and inhalation of particulates. It is important to highlight that human health risk assessment is a very conservative modeling, trying to protect the human health including critical subpopulations. Epidemiological study carried out at Paracatu city will bring new elements to the uncertainties in the human health risk assessment. © 2014 Taylor & Francis Group.

Merma A.G.,Pontifical Catholic University of Rio de Janeiro | Torem M.L.,Pontifical Catholic University of Rio de Janeiro | Moran J.J.V.,Pontifical Catholic University of Rio de Janeiro | Monte M.B.M.,Center for Mineral Technology
Minerals Engineering | Year: 2013

Mineral bioflotation encompasses the principles and methods used in mineral flotation using microorganisms as flotation reagents. This work deals with the fundamental aspects of apatite and quartz flotation using Rhodococcus opacus bacteria as a bioreagent. Each mineral sample was conditioning with the bacterial suspension in a rotary shaker under specific conditions as particle size, biomass concentration, pH solution and conditioning time, for all the studies done during the research. The zeta potential results showed a change in zeta potential measurements of the minerals after the bacterial interaction. This change was more significant in the zeta potential curves of apatite than those for quartz. The results also suggest that the bacterial adhesion onto the mineral surfaces was predominantly specific. The greatest apatite flotability achieved 90% at pH around 5, in the presence of 150 mg L-1 of bacteria after 5 min of flotation. On the other hand, quartz achieved a flotability of 14% under identical experimental conditions. The fundamental flotation studies revealed the prospect that R. opacus presents as a biocollector and biofrother and indicate its promising application in phosphate flotation industry. © 2012 Elsevier Ltd. All rights reserved.

Veneu D.M.,Center for Mineral Technology | Torem M.L.,Pontifical Catholic University of Rio de Janeiro | Pino G.A.H.,Pontifical Catholic University of Rio de Janeiro
Minerals Engineering | Year: 2013

The first line of biosorption technology research aims to enhance pathways for the use of novel biosorbents, and thus, reduce the utilization of noneco-friendly process based in chemical products, and to provide economic and sustainable alternatives to conventional process. This subject presents a multidisciplinary approach and requires the fundamentals of water chemistry, biochemistry and surface chemistry to name a few. Biological processes have been attracting attention in heavy metals removal by bacterial strains, due to lower operating costs and their potential applications for ionic metal species removal from aqueous solutions even in high concentrations. The ability of Streptomyces lunalinharesii to sorb copper and zinc from aqueous solutions was investigated through batch experiments at 25 °C. Various sorption parameters such as contact time, initial metal concentration, pH and biomass concentration and the sorption capacity were studied. The degree of copper and zinc removal achieved values around 81% and 60% at pH 5.0 and 6.0, respectively. Moreover, the metals uptake remained constant for contact time above 30 min. The experimental data at equilibrium were fitted to Langmuir and Freundlich adsorption isotherm models and the model parameters were evaluated. The kinetic study showed that the pseudo-second-order rate equation better described the biosorption process. The FTIR analysis revealed that hydroxyl, carboxyl and amine groups were major binding groups. © 2012 Elsevier Ltd. All rights reserved.

Neumann R.,Center for Mineral Technology | Avelar A.N.,Vale S.A. | Da Costa G.M.,Federal University of Ouro Preto
Minerals Engineering | Year: 2014

Although bauxites usually have a quite simple mineralogy - gibbsite (+boehmite), quartz, kaolinite, hematite, goethite, anatase (+rutile) and minor or less common phases, fine particle size, low crystallinity and variable compositions of the iron minerals might render phase quantification difficult, as well as impairing bauxite processing. A reliable and complete characterisation is therefore necessary in order to predict processing performance and ensure compliance to plant specifications. X-ray diffraction is the most important single tool for bauxite characterisation, and the constrained refinement of the Al-for-Fe substitution in goethite during one-step phase quantification by fundamental parameters Rietveld method has been successfully used. The same method was developed to analyse the coupled Al-for-Fe and OH --for-O2- substitutions in hematite. The method was tested against Mössbauer spectroscopy iron distribution on bauxite samples with a large compositional range, and on bauxite Certified Reference Materials from the main Brazilian mines, with improved results and widened range of conclusions that can be drawn related to bauxite processing. © 2013 Elsevier Ltd. All rights reserved.

Veneu D.M.,Center for Mineral Technology | Pino G.A.H.,Pontifical Catholic University of Rio de Janeiro | Torem M.L.,Pontifical Catholic University of Rio de Janeiro | Saint'Pierre T.D.,Pontifical Catholic University of Rio de Janeiro
Minerals Engineering | Year: 2012

The aim of this work was to study the fundamental aspects of a combined biosorption/bioflotation system applied to cadmium removal from aqueous solutions using a Streptomyces lunalinharesii strain. The main sorption conditions, such as solution pH, biomass concentration and the initial concentration of cadmium were evaluated on the metal uptake performance. The characterization of the biosorbent was carried out through zeta potential measurements, FTIR spectra and SEM images. From the sorption studies, it was observed that the metal removal was significant, around 55% in a single stage, and took place at pH around 5.0; biosorption studies showed that the Langmuir model fitted properly well. Moreover, the maximum cadmium uptake was about 24.8 mg g -1. The kinetic works showed that the pseudo-second-order model appropriately fitted the experimental data. The integrated process of biosorption-bioflotation achieved a cadmium removal value around 61%. © 2011 Elsevier Ltd. All rights reserved.

Discover hidden collaborations