Navegando por Autor "Vianna, Marilda M. G. Ramos"
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Artigo Clay-based catalyst synthesized for chemical oxidation of phenanthrene contaminated soil using hydrogen peroxide and persulfate(Elsevier, 2020-04) Chiavone Filho, Osvaldo; Magalhães, Vivian Maria de Arruda; Mendes, Gabriela Paupitz; Costa Filho, José Daladiê Barreto da; Cohen, Renato; Partiti, Carmem S. M.; Vianna, Marilda M. G. RamosHydrocarbon contaminated sites are a critical issue. Soil is a complex substrate and its heterogeneity makes soil remediation a difficult task. Studies involving in situ chemical oxidation focusing on soil remediation are scarce in literature. Heterogeneous catalysts for oxidation process can be supported in clays. In this work, different claybased catalysts were synthesized. Concentrations of sodium hydroxide (NaOH), ferrous sulfate (FeSO4), and ferric sulfate (Fe3(SO4)2) were varied in accordance with a 23 experimental design. Modified clay catalysts (MCC) were applied in oxidation assays of phenanthrene (PHE) contaminated soil to evaluate the activation of two oxidants: sodium persulfate (SP) and hydrogen peroxide (HP). The experimental design response was the PHE removal. Most of the catalysts proved to be efficient in activating both oxidants and achieved around 80 % of PHE removal. Control assays showed that around 20 % of PHE can be naturally transferred from soil to the liquid phase. PHE removal did not occur during oxidation with raw clay (RC). The highest PHE removal was obtained using MCC 16 with HP, reaching 83 %. XRF analysis of MCC 16 indicated an increase of 160 % in iron content and the Mössbauer spectroscopy showed higher values of relative Fe3+ doublet area for MCC 16 than for RC. BET surface area measurements and scanning electron microscopy analysis suggested the impregnation of iron minerals on the MCC 16 surface. The catalyst proposed in this study can be applied in both in situ or ex situ remediation circumstances, reducing the environmental effects of organic contaminantsArtigo Treatability studies of naphthalene in soil, water and air with persulfate activated by iron(II)(Elsevier, 2020-04) Chiavone Filho, Osvaldo; Mendes, Gabriela Paupitz; Magalhães, Vivian M. A.; Soares, Lélia C. R.; Aranha, Rayanne Macêdo; Nascimento, Cláudio Augusto Oller do; Vianna, Marilda M. G. RamosChemical oxidation was applied to an artificially contaminated soil with naphthalene (NAP). Evaluation of NAP distribution and mass reduction in soil, water and air phases was carried out through mass balance. Evaluation of NAP distribution and mass reduction in soil, water and air phases was carried out through mass balance. The importance of the air phase analysis was emphasized by demonstrating how NAP behaves in a sealed system over a 4 hr reaction period. Design of Experiments method was applied to the following variables: sodium persulfate concentration [SP], ferrous sulfate concentration [FeSO4], and pH. The system operated with a prefixed solid to liquid ratio of 1:2. The following conditions resulted in optimum NAP removal [SP] 1⁄4 18.37 g/L, [FeSO4] 1⁄4 4.25 g/L and pH 1⁄4 3.00. At the end of the 4 hr reaction, 62% of NAP was degraded. In the soil phase, the chemical oxidation reduced the NAP concentration thus achieving levels which comply with Brazilian and USA environmental legislations. Besides the NAP partitioning view, the monitoring of each phase allowed the variabilities assessment over the process, refining the knowledge of mass reduction. Based on NAP distribution in the system, this study demonstrates the importance of evaluating the presence of semi-volatile and volatile organic compounds in the air phase during remediation, so that there is greater control of the system as to the distribution and presence of the contaminant in the environment. The results highlight the importance of treating the contaminant in all its phases at the contaminated site