Juliana Cristina Tristão

Iron: a versatile element to produce materials for environmental applications

Iron is a versatile element forming several phases with different oxidation states and structures, such as Feo, FeO, Fe3O4, γ-Fe2O3, α-Fe2O3 and FeOOH. All these phases have unique physicochemical properties which can be used for different applications. In this work, it is described the use of different iron compounds, synthetic and also from natural and waste sources, in environmental and technological applications. Two main research areas are described. The first one is related to strategies to increase the reactivity of Fe phases, mainly by the formation of Feo/iron oxide composites and by the introduction of new metals in the iron oxide structure to promote new surface reactions. The second area is the use of the magnetic properties of some iron phases to produce versatile magnetic materials with focus in adsorption, catalysis and emulsions.

Use of tar pitch as a binding and reductant of BFD waste to produce reactive materials for environmental applications

In this work, a new approach is presented for the modification of the hazardous steel industry waste BFD (Blast Furnace Dust) into a versatile material for application in environmental remediation processes. Tar pitch, another waste, was used to agglomerate the very fine (submicrometric) dust particles to produce a compact and robust pelletized material that under simple thermal treatment produces notably reactive reduced Fe phases. SEM, TG/DTA, Mössbauer, XRD, Raman, BET and elemental analyses indicated that the tar/BFD composite (1:1wt ratio) pellets treated at 400, 600 and 800°C lead to tar decomposition to form a carbon binding coat concomitant with the reduction of the Fe oxides to produce primarily Fe3O4 (magnetite), FeO (wüstite) and Fe(0). Preliminary reactivity studies indicated that these treated composites, especially at 800°C, are active for the reduction of Cr(VI)aq and for the elimination of textile dye via reduction and the Fenton reaction.

Selective Oxidation of Amorphous Carbon by CO2 to Produce Fe@C Nanoparticles from Bulky Fe/C Matrices

In this work, a bulky Fe0/carbon matrix obtained by a low cost and simple reduction/carbonization of Fe3+ salt with sucrose was treated with CO2 to selectively oxidize the amorphous carbon to release the graphite like carbon coated magnetic Fe0 particles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, X-ray diffraction (XRD), BET, thermogravimetric analysis (TG) (in CO2) and particle size analyses showed that the treatment with CO2 of the Fe/carbon bulky composite led to the selective oxidation of the more amorphous carbon with the formation of 125-132 nm Fe@C nanoparticles with surface areas of 217 m2 g−1.

Tuning the surface properties of biochar by thermal treatment

In this work, the effect of controlled thermal treatment to tune biochar surface properties such as area/porosity, functionalities and reactivity was investigated. TG-MS, CHN, Raman, IR, BET, Zeta and SEM analyses suggested that thermal treatment led to the decomposition of an organic complex/amorphous phase to produce micropores based on graphene nanostructures and a strong increase on surface area from 3m2g-1 for biochar to 30, 408 and 590m2g-1, at 400, 600 and 800°C, respectively. The treatment also led to a gradual decrease on oxygen content from 27 to 14wt% at 800°C due to decomposition of surface functionalities changing surface properties such as zeta potential, adsorption of anionic and cationic species and an increase on the activity for sulfide oxidation which is discussed in terms of increase in surface area and the presence of surface redox quinone groups.

Magnetic Carbon Nanofiber Networks as Support for Ionic Liquid Based Catalyst

In this work, the ionic liquid (IL) 1-hexyl-3-methyl-imidazolium bromide (HMIm.Br) containing Pd suspended nanoparticles was supported on a nanostructured magnetically recoverable carbon nanofiber network. The magnetic material was prepared by a simple reaction of ethanol directly with a nanostructured hematite. SEM, XRD, Mössbauer, Raman, TG/DTA, BET surface area and magnetization analyses suggested that the network is based on carbon nanofibers with carbon coated magnetic Fe nanoparticles. These magnetic networks offer a high exposed carbon fiber area, which has a good interaction with the IL to form a thin layer. Preliminary studies with a Pd dispersed in supported IL as catalyst for the hydrogenation of 1,5-cyclooctadiene showed a membrane effect, which leads to an important increase on the selective hydrogenation of 1,5-cyclooctadiene to cyclooctene.Graphical Abstract

Professor de ensino superior: o entendimento a partir de narrativas de pós-graduandos em química

The quality of higher education has raised growing interest among researchers and experts in education. In the present work we have emphasized the correlation between the growing specialization offered by graduate programs in Chemistry and the improvement in the quality of university teachers, trying to understand how the graduate students themselves imagine the teaching activity. For that, graduate students in Chemistry from the Federal University of Minas Gerais were invited to construct narratives about a fictitious situation in which they imagined themselves as teachers. The analysis of the reports was made by grouping the facts described under three categories: the preparation for approval in the admission exam, the classes taught, and the activities developed during the first four months of work. Results have shown that students pay less attention to the teaching activity and tend to value research and the activities that foster it. This shows that future professionals, even taking up the post of teachers, are more predisposed to act as researchers than to exercise the teaching activity. Such indication seems to be related to the demands made during the selection process for higher education teachers and to the current work situation in most universities, which evaluate qualitatively the intellectual production in the form of articles, whereas classes are evaluated in a more quantitative manner.