Enhancing recycled-paper quality using cellulose nanocrystals from pineapple leaf waste

Abstract Pineapple leaves, often found as waste in North Tapanuli District, Sipahutar District, contain high levels of cellulose, making them a potential source for extracting cellulose nanocrystals (CNC). This study employs the acid hydrolysis method, followed by ultrasonication, to produce CNC, a process known for its simplicity and effectiveness in removing amorphous cellulose. The Fourier transform infrared spectroscopy (FTIR) analysis at a wavenumber of 1,358 cm −1 , associated with S=O vibrations, indicates esterification during hydrolysis. Transmission electron microscopy (TEM) reveals that the extracted CNCs exhibit a rod-like structure with a diameter of 5.18 ± 1.61 nm. X-ray diffraction (XRD) results show a crystallinity index of 78 % and a crystal size of 2.35 nm. The CNCs were incorporated into used newspaper pulp at varying concentrations (0, 1.5, 3, 5, and 8 |wt%). The findings demonstrate that CNC addition enhances the mechanical properties of the paper, including grammage, tensile strength, tear index, and crack index, primarily due to hydrogen bonding interactions between CNCs and pulp fibers. The optimal improvement was observed with a 5 | wt% CNC addition, significantly increasing tensile strength, tear index, and crack index of the recycled paper.