Structural characterization of the nanocellulose obtained by high intensity ultrasound from several cellulose sources.

In this study, nanocelluloses (NC) were produced under identical processing conditions by high-intensity ultrasonication (HIUS) in aqueous medium, without chemical pretreatment, from bacterial cellulose (BC), viscose rayon residue (VR), curauá fiber (C), and sugarcane bagasse (SCB). The effects of treatment on particle size, morphology, chemical composition, crystallinity, thermal stability, yield, and energy consumption were evaluated. NC obtained from C and SCB retained residual hemicellulose and lignin. All NC exhibited higher crystallinity index values after HIUS treatment compared with the respective raw materials. NC from BC and VR presented the smallest particle sizes, 190 and 90 nm, respectively, while NC from C and SCB exhibited the highest aspect ratios (55.9 and 63, respectively), despite showing lower onset degradation temperatures (229 °C and 239 °C, respectively). Yield was 11% for NC from VR, C, and SCB, and could not be determined for BC. Among the conditions evaluated, HIUS treatment (750 W, 20 kHz, 45 min) of BC at 1.3% w/w produced NC with an average size of 219 nm, an onset degradation temperature of 273 °C, and an energy consumption of 140 MWh t-1. These findings indicate that HIUS is a viable, chemical-free route for producing NC from diverse cellulosic and lignocellulosic sources, although energy consumption remains a key parameter for further optimization toward industrial scalability. These results were obtained under a low-solid-content regime, and further work is needed to assess the effects of higher fiber loadings on process efficiency and scalability.