Síntese e caracterização de nanocelulose a partir da folha de abacaxi (ananás comosus (L) merril) c.v. vitória

Abstract

The pineapple leaves are usually burned at the end of the fruit harvest, and, therefore, are not explored and applied commercially. In this context, this work aimed to characterize the pineapple leaf (FFA) of the Vitória variety, which is studied for the first time for the extraction and characterization of cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF). Firstly, moisture (8%), ash (6.2%), extractive (12%), lignin (20.28%), holocellulose (54.75%) and α-cellulose (46.85) contents were evaluated, confirming the possibility of obtaining a high cellulose yield from this waste. Purification of cellulose was carried out by applying sodium chlorite (NaClO2) and glacial acetic acid (CH3COOH). After the cellulose extraction, the CNCs were isolated, where they were obtained through acid hydrolysis, with 60% H2SO4 (w / w). For the isolation of CNFs, the mechanical method was used by applying a Super Mass Colloider defibrillator mill. After the two processes, the resulting materials were frozen and lyophilized to be characterized. Then, the milled samples, cellulose, CNCs and CNFs were characterized by the techniques of X-ray fluorescence (FRX), Laser diffraction (DLS), X-ray diffraction (DRX), infrared spectroscopy with Fourier transform (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM). By FRX, it was demonstrated that the major element in the leaves is potassium (55.28%), followed by calcium (31.15%), silicon (2.89%), and manganese (2.71%). In the XRD analyzes, a change was observed in each sample analyzed, where the fresh sample and the cellulose presented characteristics of semicrystalline materials with type I cellulose structures. cycles there was a drop in crystallinity and for CNCs there was an increase in crystallinity, showing efficiency of the method used. The FTIR spectra showed characteristic bands of cellulose, being similar for all samples. Through the TGA analyzes it was possible to observe the stages of thermal degradation was evidenced by SEM that the fresh sample has a lamellar shape with smooth surface, and, after cellulose extraction, this shape was preserved, with a change from smooth to rough surface. Thus, the leaves of the pineapple were shown to have a high potential to produce cellulose and its derivatives from an underutilized waste, adding value and allowing the possibility of new applications.