Avaliação da hematita como agente ativante na obtenção de carvão ativado e ferro metálico

Abstract

This work involves the use of agro-industrial residue, sugarcane bagasse soot (FBCA), and hematite to obtain activated carbon (CA) and metallic iron (Fe0

). The precursors were subjected to heat treatment under different experimental conditions, such as: temperature (600, 800 and 900 °C), time (30, 60 and 120 min) and soot:hematite ratio (1:3 and 1:5 m/m). The results obtained will be present in two scientific articles. The first article shows in particular the results of characterization and application of the CA obtained. The highest BET surface area values were for materials obtained at a temperature of 900 °C and with time equal to or greater than 1 h, obtaining values of up to 1570 m2 g -1 . The images obtained by SEM for the CA show that after activation there was a reduction in the size of the particles, but the morphology was maintained, showing an elongated shape with the presence of cavities. The results obtained by EDS allowed identify the presence of residual Fe present in the CA after activation and purification. The TG results show an increase in thermal stability and ash content variation between 3.5 and 11.9%. Few surface functional groups were identify, and pHpcz values between 6.5 and 6.0. Adsorption studies were also carried out for CA using methylene blue and reactive black dyes. The adsorption isotherms for the methylene blue dye showed that the adsorption capacities of the carbons increased with the activation temperature and time of activation. From the adsorption isotherms of the reactive black dye, it can be observed that when applying the activation temperature of 900 °C, with a reaction time of 120 min, as well as the highest amount of activating agent FBAC:Fe2O3 ratio (1:5 ), the adsorption capacities increased from 130 to 374 and 378 mg g-1

. The second article presents the results of characterization and application of magnetic samples, rich in iron. The results of the characterizations performed by TG, elemental analysis (CHN), X-ray diffraction (XRD), Mössbauer spectroscopy, SEM and EDS, show the presence of metallic iron, FeO and Fe3O4 in the samples obtained at temperatures equal to and above 800 °C, with Fe0

being the predominant phase in the samples obtained at 900 °C. The materials had a low carbon content (<6%), with a morphology similar to clusters and “wire tangles”. Among the ferrous materials, the one obtained at 900 °C with an activation time of 1 h and a mass ratio of 1:3 (FBCA:Fe2O3), identified as Fe1:3/900-1h, was applied to reduce hexavalent chromium and nitrobenzene. The application of the sample to reduce contaminants showed a reduction capacity of 480.5 mg of Cr(VI) per gram of material and conversion of 90% of nitrobenzene to aniline in just 6 min of reaction. The results obtained showed that hematite has a high capacity to act as an activating agent for charcoal, obtaining two products in a single process, high surface area CA and a sample rich in metallic iron.