Isolation of Nanocellulose from Pomelo Fruit Fibers by Chemical Treatments

Abstract

This study aims to isolate cellulose nanofibers from locally abundant pomelo fruit. Only the inner, soft peels were selected for investigation. The peels were subjected to alkali treatment (NaOH) with different concentrations and soaking times. Acid hydrolysis was also carried out to obtain an aqueous suspension of nanocellulose. The treated cellulose fibers were characterized by various methods. The effect of alkali treatment was initially confirmed by Fourier Transformed Infrared (FTIR) Spectra which displayed disappearance of several peaks belonging to non-cellulosic materials. The sharpening of the absorption at around 914 cm-1 is attributed the β-glycosidic linkages between the sugar units in cellulose. Alkali treatment also helped eliminate the non-cellulosic constituents via reduction in the 1240 and 1750 cm-1 peak. Thermogravimetric (TG) analysis revealed an improved onset of degradation likely caused by an increase in crystallinity evidenced by X-ray diffractometry (XRD) through the presence of two well-defined reflections characteristic of cellulose. The morphological and structural characterization by Scanning electron microscopy (SEM) still revealed a compact structure even after alkali treatment. However, acid hydrolysis was successful in individualizing cellulose nanofibers as observed by transmission electron microscopy (TEM). The diameter of these nanofibers was in the 10 - 20 nm range with various lengths.