Adsorção de azul de metileno por meio de resíduos da Ilex paraguariensis St. Hill.

Abstract

Currently, the textile sector is a significant source of pollution, including the generation of effluents containing synthetic dyes such as methylene blue, which are released into water bodies and affect the local biota. Yerba mate, commonly used in the form of chimarrão and tereré, especially in southern Brazil, has characteristics that allow its use as a biosorbent, increasing its economic value. This work aims to study the adsorption of methylene blue dye using the biosorbent derived from Ilex paraguariensis St. Hill. (yerba mate). To obtain the biosorbent, the material was subjected to thermal treatment and transformed into charcoal. After the treatment, analyses were conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy, in addition to kinetic and isotherm studies. Raman spectroscopy revealed that the charcoal is an imperfect graphitic material, SEM showed its degree of porosity, and XRD indicated broad bands, suggesting that the material is disordered/amorphous. The kinetic study demonstrated that the charcoal has an optimal adsorption time of 120 minutes and a maximum removal efficiency of 93%. Additionally, the model that best fitted the data was the pseudo-second-order model. Regarding the isotherm, the data were best fitted by the Freundlich model. The value presented for the separation factor indicates that the adsorption process evaluated in this work is favorable. Therefore, the use of Ilex paraguariensis St. Hill. (yerba mate) proved to be efficient and can be a viable alternative for treating effluents contaminated with dyes.