Characteristics of Nanocellulose Crystals from Balsa and Kapok Fibers at Different Ammonium Persulfate Concentrations

Balsa and kapok fibers are by-products of community plantations. Both fibers have not been optimally utilized in Indonesia. The high holocellulose content and low lignin content of these fibers indicate the potential to be used as a nanocellulose raw material with a simple extraction. The objective of this study was to extract cellulose nanocrystals (CNCs) from balsa and kapok fibers through a direct extraction without pre-treatment. CNCs from balsa and kapok fibers were prepared by a one-step procedure with ammonium persulfate solution (APS) at concentrations of 1, 1.5, and 2 mol/L. The CNCs were characterized by determining their morphology, functional groups, crystallinity, and thermal stability using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis, respectively. The results showed that the diameter of the CNCs was in the range of 1.25–11.87 nm depending on the APS concentration and the fiber type. APS dissolved the lignin and hemicellulose, which led to an increase in the CNCs crystallinity with an increasing APS concentration. The decrease in the thermal stability of the CNCs was thought to be due to the increase in the surface area of the particles and the presence of carboxyl groups in the CNCs. This research revealed that balsa and kapok fibers could be used as raw materials to produce nanocellulose in one-step using ammonium persulfate.