Cellulose nanocrystals from lignocellulosic feedstock: a review of production technology and surface chemistry modification

Fossil fuel substitutes are being developed to combat the ecological impact and rapid exhaustion of petroleum-based products. Being the most abundant polymer on Earth, cellulose-based products are renewable and sustainable. Cellulose nanocrystals (CNCs) are derived from cellulosic-based materials, have good physicochemical properties, and can be used to produce numerous products. CNC synthesis and their applications have been extensively studied; however, they remain limited to laboratory-scale as several challenges hinder its commercial-scale production. Herein, the suitability of nanocrystalline isolation methods, including chemical, enzymatic, ionic liquids, and deep eutectic solvents, for mass production is evaluated. Poor re-dispersion of CNCs is a major challenge that hinders its utilization in many applications. Hence, surface chemistry modification of CNCs have also been reviewed. It has been concluded that the CNC isolation method and surface modification technique significantly impacts its cost, morphology, and physicochemical properties. This review paper presents the challenges often faced in the conversion of bench-scale studies into commercial production of nanocrystalline cellulose. Hence, this paper gives all the necessary information on the important aspects of raw material selection, nanocellulose isolation process selection, and suitable surface modification method together in a single review article. Readers will be able to identify the possible research gaps for future research studies.