Cellulose nanofibrils (CNF) were prepared from kenaf core (KC) using acidified-chlorite bleaching method and followed by disintegration using a high speed blender. The effects of disintegration time and acid treatment on the defibrillation of holocellulose were studied. Hemicellulose was found to facilitate defibrillation, as CNF without any acid treatment was fully defibrillated after 30 min. The adsorption kinetics of CNF toward cationic dye cannot be accurately determined due to its quick adsorption performance, in which the equilibrium is achieved immediately after 1 min of contact time. The effects of acid treatment on holocellulose, pH, adsorbent dosage, temperature and dye concentration were studied and optimized. Adsorption data were fitted to both Langmuir and Freundlich models where the Langmuir model was found to be the better model to describe the adsorption process. The maximum adsorption capacity was found to be 122.2 mg g⁻¹ at pH 9, 20 °C for the non-acid treated CNF. The CNF can be regenerated by desorption at low pH where as much as 70% of the dye adsorbed can be desorbed after 6 cycles of adsorption–desorption.