CELLULOSE NANOFIBER FROM YERBA MATE STICKS: SURVEY OF MORPHOLOGICAL, CHEMICAL AND THERMAL PROPERTIES

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.