Production of nanofibrillated cellulose with superior water redispersibility from lime residues via a chemical-free process

Water removal during drying of nanofibrillated cellulose (NFC) generally results in the formation of hydrogen bonds between fibers, leading to irreversible fiber agglomeration and hence their poor water redispersibility. The feasibility of using lime residues after juice extraction to produce dried NFC possessing superior redispersibility was here investigated. After autoclaving at 110-130 degrees C for 2 h, high-shear homogenization at 3800 x g for 15 min and high-pressure homogenization at 40 MPa for 5 passes, NFC having the diameters of 5-28 nm and crystallinity index of 44-46% could be obtained. After hot air drying at 60 degrees C, dried NFC could be well dispersed in water, with viscoelastic property similar to that of the originally prepared NFC suspension. Pectin associated with cellulose nanofibrils helped prevent fiber aggregation during drying and hence facilitating nanofiber redispersion in water. This observed trend was opposite to that belonging to fiber undergone chemical treatments to remove non-cellulosic constituents.