RESUMO Neste trabalho, o resíduo fuligem de candeia foi utilizada para obter carvão ativado. A ativação foi investigada utilizando três reagentes (NaOH, H3PO4 e CO2). Os resultados de análise térmica e microscopia eletrônica de varredura mostram que os carvões ativados possuem maior estabilidade térmica e partículas mais regulares e menores quando comparados ao precursor. Medidas de área superficial mostraram que os carvões ativados com NaOH e CO2apresentaram resultados iguais a 804 e 435 m2g-1, respectivamente, e maior capacidade para adsorver o azul de metileno (222 e 118 mgg-1, respectivamente). Os valores de capacidade de adsorção são cerca de 10,6 e 5,6 vezes maiores para os carvões ativados em comparação à capacidade de adsorção da fuligem. Os resultados demonstram o grande potencial de se obter carvão ativado a partir de fuligem residual.

ABSTRACT In this study, candeia soot waste was used for the production of activated carbons. Activation was investigated using three reagents (NaOH, H3PO4 and CO2). The results of thermal analysis and scanning electron microscopy show that the activated carbons present higher thermal stability and more regular and smaller particles when compared with the precursor. Surface area measurements showed that NaOH and CO2 activated carbons present higher specific surface areas (804 and 435 m2g-1, respectively) and higher abilities to adsorb methylene blue (222 and 118 mgg-1, respectively). The adsorption capacity values of the activated carbons are nearly10.6 and 5.6 times higher than the value found for the candeia soot residue. The results demonstrate the great potential of obtaining activated carbons from residual soot.

In this study, electric arc furnace dust (EAFD) was thermally modified at different temperatures under H2 flow or charcoal in order to obtain reduced iron phases (Fe3O4, FeO and Fe0). The formation of these phases was confirmed by powder X-ray diffraction. The tests performed for reducing Cr (VI) using resultant materials obtained after thermal treatment of the EAFD showed excellent results, with PAE600H (EAFD reduced at 600 ºC under H2 flow) decreasing around 100% of the Cr (VI) in only 10 minutes of reaction. These results indicate the possibility of adding value to the residue, obtaining materials that offer great potential for environmental applications.

Titanium dioxide is an efficient photocatalist, being possible to improve its efficiency with better charge separation which occurs when it is coupled with other semiconductors. Nanometric particles of ZnO were used to impregnate TiO2 P25 in order to optimize its photocatalytic properties. ZnO/TiO2 composites were obtained at different proportions and were characterized by X-ray diffraction (XRD), micro-Raman and diffuse reflectance spectroscopies, measurement of surface area (BET) and scanning electron microscopy (SEM). Raman spectroscopy data revealed a change on the TiO2 surface due the presence of ZnO which was observed by an enlargement of TiO2 peaks and a change on the relation rate between anatase and rutile phases of the composites. The photodegradation of azo-dye Drimaren red revealed better efficiency for ZnO/TiO2 3% nanocomposite and for ZnO pure.

In this work two perovskites were prepared: LaMn1-xFe xO3, and LaMn0.1-x Fe0.90Mo xO3. XRD and Mössbauer spectroscopy suggest the formation of pure phase perovskite with the incorporation of Fe and Mo in the structure. The catalytic activity of these materials was studied in two reactions with H2O2: the decomposition to O2, and the oxidation of the model organic contaminant methylene blue. The perovskite composition strongly affects the catalytic activity, while Fe decreases the H2O2 decomposition Mo strongly improves dye oxidation.