A simple approach was developed to isolate cellulose nanocrystals (CNCs) with carboxylic groups from microcrystalline cellulose (MCC). The effect of reaction time on the morphology, microstructure, and thermal stability of isolated CNCs was investigated. The rod-like CNCs with size of 200−250 nm in length and about 15−20 nm in width were obtained by one-step citric/hydrochloric acid (C 6 H 8 O 7 /HCl) hydrolysis of MCC. The CNCs extracted at 4 h showed the highest carboxylic group content which led to a high absolute zeta potential value up to 46.63 mV. Moreover, these CNCs may be used as cationic dye adsorbent (methylene blue) and efficient flocculants with excellent coagulation−flocculation capability to kaolin suspension with a turbidity removal of 99.5%.

Green nanocomposites containing biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and cellulose nanocrystals/silver (CNC-Ag) nanohybrids were synthesized and their properties were investigated. It was found that homogeneously dispersed CNC-Ag could act as bifunctional reinforcements to improve the thermal, mechanical and antibacterial properties of PHBV. Compared to pristine PHBV, the tensile strength and the maximum decomposition temperature (T max ) of the nanocomposite with 10 wt% CNC-Ag were enhanced by 140% and 24.2 C, respectively. The nanocomposites displayed reduced water uptake and water vapor permeability along with lower migration level in both non-polar and polar simulants compared to the neat biopolymer, which can be related to the increased crystallinity and improved interfacial adhesion. Moreover, the nanocomposites showed strong antibacterial activity against both Gram-negative E. coli and Gram-positive S. aureus. The results of the study indicate that the high performance nanocomposites show great potential applications in the fields of food, beverage packaging and disposable overwrap films.