Title
Cellulose nanofiber from yerba mate sticks: survey of morphological, chemical and thermal properties
Authors
RUAN EZEQUIEL GEMMER, CLEIDE BORSOI, BETINA HANSEN, EDSON LUIZ FRANCISQUETTI, HEITOR LUIZ ORNAGHI JR., ADEMIR JOSÉ ZATTERA and ANDRÉ LUIS CATTO

Received July 11, 2023
Published Volume 57 Issue 7-8 July-August
Keywords cellulose nanofiber, yerba mate, residues

Abstract
This study aims to evaluate different process conditions for obtaining cellulose nanofibers (CNFs) from yerba mate residues. This includes chemical (bleaching and/or TEMPO-oxidation), physical (steam explosion), and mechanical treatments (ultrafine grinding). All treatments demonstrated to be efficient in obtaining CNFs, as observed from a morphological analysis by transmission electronic microscopy (TEM). A reduction of hemicelluloses and an increase in cellulose content was observed from the Fourier-transform infrared spectroscopy (FTIR) results, after all the treatments. The yerba mate sample that underwent physical/chemical/mechanical treatments showed a higher thermal degradation temperature peak at 333 °C, with a degradation of 50% of the initial mass. The activation energy (Ea) increased from 33% to 64%, when the CNFs were obtained using the derivative Friedman method for all the samples, and this method presented a greater proximity to the experimental results. These results demonstrate that CNFs can be obtained from yerba mate residues, to valorize this lignocellulosic biomass.