Fuligem do bagaço de cana-de-açúcar: ativação da fração carbonácea por meio de processo inovador e teste de adsorção

Abstract

In this work, Sugarcane Bagasse Soot (SCBS), which is a residue, was used as starting material to obtain Activated Carbon (AC) by an innovative process using Fe2O3. The activation was performed by mixing Fe2O3 with SCBS in different ratios (3:1 - 1:3 w/w) and heated to 900 °C for 1 hour in an inert atmosphere (N2). After this procedure, Fe was magnetically separated from the activated carbons in order to give two products that can be used in environmental applications (AC and Fe). The ACs were washed with HCl solution to remove the remaining iron. This material was labeled ACLV. The ACs and Fe-containing samples were labeled according to the proportion of SCBS and Fe2O3 (AC3:1, AC2:1, AC1:1, AC1:2, AC1:3, ACLV3:1.... ACLV1:3, Fe3:1 ... Fe1:3) that were used in the activation process. Carbon samples and Fe-containing samples were tested for adsorption and reductive degradation reactions, respectively, using Methylene Blue dye (MB). The characterization of the activated carbons were performed by Raman spectroscopy, XRD, SEM, EDS, TG, BET, CHN and Fe-containing samples were also characterized by XRD. Results from TG, CHN and XRD analysis showed that after washing the ACs with HCl solution the iron that was not removed from the magnetic separation step were completely leached by the acid. The BET surface area obtained for ACLVs samples showed that the specific area increased with the increasing of hematite content used for activation. Thereby, CALV1:3 presents a surface area of 2331 m2g-1, which is about five times higher than the SCBS surface area (438 m2g-1). Results from Raman spectroscopy showed that AC and ACLV samples have both organized (graphitic) and disorganized carbons. Diffractograms obtained for the Fecontaining samples showed that they are composed mainly by metallic iron, which were formed during the carbothermic reduction of hematite by the carbonaceous structure. MB adsorption tests showed that the adsorption capacity increased with the increase of Fe2O3 levels, reaching up to 1380 mg g-1 for ACLV1:3. This value is about seven times greater than that one obtained for SCBS. The qm values obtained from the Langmuir model were close to the experimental values and the RL values (Langmuir) and 1/n (Freundlich) indicate favorable adsorption of the MB dye. Mathematical treatment for adsorption kinetics showed that the activated carbons follow the models: pseudo-second order (Elovich equation) and Intraparticle Diffusion (IPD). Results from Fecontaining samples for the reductive degradation reactions showed that all materials have high efficiency in discoloring the dye herein studied.