Effect of the chemical treatment sequence on pineapple peel fiber: chemical composition and thermal degradation behavior

Abstract

Millions of tons of fruit waste are generated globally every year from agricultural residues, which makes it essential to find alternative uses to increase their aggregate value and reduce their environmental impact. The present study aimed to explore pineapple peel as an alternative source of cellulose by evaluating its chemical composition and physical properties, which are essential for applications. A sequence of chlorine-free treatments was applied to purify the cellulose by removing noncellulosic components in the fresh pineapple peels. The cellulosic pulp was characterized regarding its chemical composition and characterized by Nuclear Magnetic Resonance (13C NMR), X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis to determine crystallinity, structural properties, morphology, and thermal characteristics, respectively. The results revealed that the pineapple peel amorphous segments containing hemicelluloses and lignin were extensively removed with increasing chemical treatment steps, leading to increased purity, crystallinity index, and thermal stability of the extracted cellulose pulps. The maximum thermal degradation (150 °C) and crystallinity index (80.9%) were determined for the cellulosic material obtained from the second bleaching (2B) step. The cellulose content increased from 24% in the starting material (fresh pineapple peel) to 80.9% in the bleached cellulose (2B). These results indicate that the extracted cellulose from pineapple peel has characteristic for applications such as the production of cellulose nanocrystals due to the high crystallinity. Graphical abstract: [Figure not available: see fulltext.].