Carbon nanostructures based-adsorbent obtained from iron ore tailings

Abstract

In the present work, for the first time in literature, raw iron ore tailings (IOTs) were used as catalysts for the synthesis of carbon nanomaterials (CNMs) by the chemical vapor deposition method (CVD) in a fixed-bed reactor. The reaction parameters were optimized using ethanol as the carbon source, and from the best condition, the synthesis was also carried out using acetone. The characterization of materials showed that both carbon precursors were able to produce several types of carbon structures: nanometric (MWCNT, CNF) and non-nanometric (fibers, amorphous carbon). The TEM images, Raman spectroscopy and TGA revealed that the ethanol led to the growth of more organized structures and less amorphous material. The CNMs from both carbon sources were used without any purification or functionalization treatment, as adsorbents for the rhodamine B (cationic) and indigo-carmine (anionic) dyes. The CNMs were able to adsorb only the cationic dye. The adsorption was investigated by the main kinetic models and by adsorption isotherms. Regarding the kinetic study, the pseudo-second-order model was the best fit to the experimental data, and the intraparticle diffusion model presented multilinearity for both adsorbents. Concerning the type of isotherm, the data was better adjusted by the Langmuir model, indicating that the dye adsorption on the CNMs occurred at specific sites.