Preparation of Nanocellulose with High-Pressure Homogenization from Pretreated Biomass with Cooking with Active Oxygen and Solid Alkali

Nanocellulose (NCC) from pretreated wood and bamboo wastes was isolated by high pressure homogenization (HPH) in homogeneous media. The pretreatments included cooking with active oxygen and solid alkali (CAOSA) and bleaching with hydrogen peroxide (H₂O₂). Cellulose of high recovery was successfully obtained from wood and bamboo wastes with CAOSA pretreatment. The results showed that the crystallinity indices of BR-NCC and WP-NCC increased to 74% and 83%, with a CAOSA and bleaching treatment process, respectively. NCC was homogenized at 100 MPa for 30 min, mainly in the diameter of 10 to 40 nm. The zeta potential of NCC suspensions from the two raw materials was lower than −30 mV after being placed for 7 days, which demonstrates that the suspension has good stability. Thermogravimetric analysis (TGA) indicates that the thermal stability of NCC is lower than that of raw fiber. These results prove that CAOSA assisted HPH pretreatment is an efficient and environmentally friendly means for the separation of NCC, clearly demonstrating the potential of reducing environmental pollution by the use of small amounts of nontoxic chemicals during pretreatment, especially during the bleaching process. This study first proposed the CAOSA pretreatment assisted HPH process to prepare NCC from raw biomass material. The assembled NCC was spherical and of high crystallinity.