Desenvolvimento de adsorvente carbonáceo a partir de resíduo de baru para adsorção do Sudan IV em hexano

Abstract

The present study addresses the preparation of activated carbon from baru (Dipteryx alata) residues using slow pyrolysis in a conventional furnace, followed by chemical activation with H₃PO₄, aiming to investigate its adsorptive capacity for removing Sudan IV dye in hexane solvent. The activated carbon produced (CABar) was characterized using analytical techniques, such as Elemental Analysis (CHNO), Scanning Electron Microscopy (SEM), N₂ Adsorption-Desorption Isotherms, Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), and Raman Spectroscopy. After characterization, the adsorptive capacity of CABar was tested for the removal of Sudan IV dye from n-hexane using the batch method. Nonlinear pseudo-first-order and pseudo-second-order kinetic models were employed to study adsorption kinetics. The mass yield (%) of the pyrolysis product was 40%. CABar had a specific surface area of 1250 m²/g and a structure composed of micropores and mesopores. FTIR analysis revealed the presence of chemical groups in the activated carbon, including hydroxyls, carbonyls, aromatics, and phosphates. Raman and XRD analyses confirm the amorphous graphitic structure of the material. SEM revealed the presence of cavities and pores of different sizes and shapes throughout CABar. Adsorption kinetics were rapid within the first 5 minutes of contact, reaching equilibrium conditions within 20 minutes. The pseudo-second-order model best represents the adsorption kinetics, indicating the occurrence of chemisorption. Nonlinear equilibrium models such as Langmuir, Freundlich, and Sips were used to fit the experimental data and study the equilibrium conditions. The Sips model best represents the equilibrium condition between adsorbate and adsorbent, achieving a maximum adsorption capacity (Qmax) of 344.114 mg·g⁻¹. Additionally, desorption studies revealed that the adsorbent maintained efficiency after being reused for up to four adsorption cycles.