Paulo Rogério da Costa Couceiro

Óxidos de ferro de solos formados sobre gnaisse do Complexo Bação, Quadrilátero Ferrífero, Minas Gerais

The objective of this work was to characterize iron oxides from B-horizons of three soil profiles developing on gneiss of the Bacao Complex geodomain in the Quadrilatero Ferrifero, Minas Gerais, Brazil. Samples were collected from the uppest, middle and lowest segments along the slope. The earth fine fractions (mean diameter, f = 2 mm) were separated for all samples. The chemical composition of the major elements was determined with the X-ray fluorescence technique; the mineralogical analysis was performed with powder X-ray diffractomer and Mossbauer spectroscopy. All samples have similar mineralogical composition, with a general occurrence corresponding to the sequence quartz >> gibbsite > kaolinite > goethite. From the 4.2 K-Mossbauer results, the coexistence of goethite (major) and hematite is confirmed. The isomorphic aluminum contents, as they were deduced from the hyperfine fields, lead to the following chemical formulas for goethites: aFe0.79Al0.21OOH (upslope), aFe0.75Al0.25OOH (midslope) and aFe0.78Al0.22OOH (downslope). The iron oxides transformation dynamics in B horizons along the slope is a useful indicator of the paleo-climatic oscillations in this area: aluminous goethite is an indicator of humid paleo-environments, whereas aluminous-poorer goethite reveals drier pedogenic conditions.

Mecanismos químicos e mineralógicos de transformação da magnesioferrita de solo derivado de tufito, da região do Alto Paranaíba, MG

Magnetic soils forming on tuffite of the region of Alto Paranaiba, Minas Gerais, Brazil, usually contain iron-rich spinels exceptionally rich in magnesium and titanium. In this work, samples of the magnetically separated portion from the sand fraction of a Brunizem (Chernossolo) and from its mother-rock material were analyzed with synchrotron X-ray diffraction and 57Fe-Mossbauer spectroscopy. Magnesioferite (MgFe2O4) and maghemite (its pure non-stoichiometric spinel structure, Fe8/3 ⊕ 1/3 O4, where ⊕ = cation vacancy, corresponds to γFe2O3) were the magnetic iron oxides so identified. Basing on these data, a consistent chemical-mineralogical model is proposed for the main transformation steps involving these iron oxides in the pedosystem, starting on magnesioferrite to finally render hematite (αFe2O3), passing through maghemite as an intermediate specie.

Activated Coal-Based Composites of Oily Sludge and Iron Oxides for the Removal of Contaminants in Aqueous Solution

In this work were produced and characterized activated coal-based composite of oily sludge residues and synthetic iron oxide at different temperatures contaminants removal of contaminants in aqueous solution. The composites showed different compositions of coal, metallic iron and iron oxides (hematite, magnetite/maghemite and wustite) with fairly magnetic behavior. The estimated surface area of these materials by the indirect method of adsorption of methylene blue showed a decrease from the activated coal (273 m 2 g -1 ) for the composite prepared at 800 C (191 m g). The results adsorption of methylene blue, Cd 2+ and Pb 2+ by adsorbent materials in general, fitted to the Langmuir isotherm. Also, the data showed good correlation with the isotherms of Freundlich and Sips. The maximum amount absorbed for methylene blue (141.5 mg g -1 ) with activated coal, for the Cd 2+ (503.4 mg g -1 ) with composite at 600 C and for the Pb (464.4 mg g) with composite at 800 C, were probably due to the materials constitution, since the magnetic materials have a higher adsorption capacities for the Cd 2+ and Pb 2+ , while non-magnetic material (as a activated coal) showed a higher adsorption for methylene blue.