Light-colored cellulose nanofibrils produced from raw sisal fibers without costly bleaching

Although nanocelluloses can be isolated from unbleached lignocellulosic fibers, the presence of residual lignin may result in nanocellulose products with dark colors, which limit their application in many fields. In this study, maleic acid pretreatment is utilized prior to the ball milling of raw sisal fibers to produce white or light-colored cellulose nanofibrils (CNFs). Pretreatment of the unbleached sisal fibers can facilitate the fibrillation of CNFs through the depolymerization of cellulose and the dissolution of non-cellulosic cell wall components and noncrystalline cellulose. After 2 h of maleic acid hydrolysis at 90 degrees C, the obtained light-colored CNFs shows a glucan content of 91.03 % and an average width of 12.35 nm. Self-standing films produced from the CNFs exhibit a high tensile strength of 92.73 MPa and an elastic modulus of 3.13 GPa. This study presents an innovative approach for using raw lignocellulosic fibers to produce light-colored CNFs without requiring a costly bleaching process.