Navegando por Autor "Cordeiro, Juni Silveira"

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Microwave aquametry according to ASTM D4643-17 for moisture determination in iron ore tailings.
(2022) Cordeiro, Juni Silveira; Eloi, Danilo Manata; Araújo, Sirlan; Brito, Hermando; Luz, José Aurélio Medeiros da
The gradual increase in the exploitation of iron ore leads to a need for the disposal of tailings from its processing. One of the key features of a granular system stacked is its moisture content. This work aimed at evaluating the use of microwave oven to determine the moisture content (following the ASTM D4643-17 standard) of iron ore dewatered tailings, for fast assessment of the geotechnical condition of every stacked layer on disposal areas. The preconized method has showed good agreement with the conventional oven method (standard assay), resulting in linear equation with coefficient of determination of 0.9953. However, the recommended method has shown less accuracy in the range of low moisture values (below 5 %), which does not represent a critical disadvantage from the point of view of geotechnical safety. The economic impact of the method advocated here will be great, since the movement of large volumes of tailings in limited areas leads to customary downtime, often resulting from waiting for confirmatory analytical results to practice within the safety limits.
Understanding the environmental impact of a mine dam rupture in Brazil : prospects for remediation.
(2019) Santos, O. S. H.; Avellar, F. C.; Alves, M.; Trindade, R. C.; Menezes, M. B.; Ferreira, M. C.; França, G. S.; Cordeiro, Juni Silveira; Sobreira, Frederico Garcia; Yoshida, Maria Irene; Moura, P. M.; Scotti, M. R.
The rupture of the Fundão mine dam in Mariana municipality, Minas Gerais State, Brazil, spilled the tailings across the Doce River basin. These tailings, composed of residues discarded from the beneficiation of iron ore, are rich in SiO2 and Al2O3, as well as some ether amine compounds and NaOH. The aim of this study was to assess the distribution of these sediments, as well as their effect on the riparian zones reached, as compared with preserved sites. Sediment deposition in the river resulted in a morphological change from a meandering profile to a braided aspect. The nutrient and mineral content (P, K, Ca, Mg, Cu, Fe, Mn, Zn, and NO3−) and soil organic matter of the sediments were depleted, whereas NH4+, Na, and pH increased. A random presence of ether amines in the sediments was confirmed by quantitative and chromatographic analyses, with concentrations ranging from 0 to 57.8 mg kg−1; Na reached values as high as 150 mg kg−1. The impact of the dam tailings on biota was assessed by estimating total microbial biomass (phospholipid fatty acids), which were depleted in sediments relative to soils from preserved sites. Overall plant mortality, as well as a low resilience capacity, were also observed. Ether amines and Na present in the sediments had a strong toxic effect in the environment. Identification of these substances as the main impact factors will help guide future remediation efforts.