Pectin-containing holocellulose nanofibrils: Enhanced water redispersibility due to strong electrosteric repulsion

Due to their unique properties, holocellulose nanofibrils (HCNFs) are drawing more and more attention. Residual pectin and lignin may have significant impacts on the redispersion of HCNFs, but relevant studies are lacking. Herein, HCNFs with different residues were prepared from kenaf fibers using careful chemical pretreatments followed by mechanical disintegration. The chemical structure, crystalline phases, morphological features, redispersion properties and intermolecular interactions of different HCNFs were carefully characterized for clarifying the effects of residual pectin and lignin on the redispersion of HCNFs. Residual pectin significantly increased the water redispersibility of HCNFs with an aspect ratio of 241, whereas residual lignin decreased the water redispersibility of HCNFs with an aspect ratio of 48. After 30 days of storage, redispersed pectin-containing HCNFs (P-HCNFs) presented dispersion stability close to never-dried P-HCNFs. The possible mechanism for high redispersibility of P-HCNFs is the formation of synergistic electrostatic and steric repulsion forces between cellulose fibrils, triggered by carboxyl groups in residual pectin and large aspect ratio HCNFs. This study proposes a redispersion strategy for HCNFs isolated from kenaf fibers.