Preparation of high yield lignin-containing cellulose nanofibrils from alkaline peroxide mechanical pulp by deep eutectic solvents pretreatment.

The presence of lignin endows lignin-containing cellulose nanofibrils (LCNFs) with special properties. Nevertheless, the conventional methods for cellulose nanofibrils (CNFs) fabrication are confronted with challenges of environmental and economic considerations. In presence work, an environmentally sustainable process of deep eutectic solvents (DES) pretreatment followed by ultrasonic treatment was explored for fabrication of LCNFs from alkaline peroxide mechanical pulp (APMP). In addition, the effects of pulp refining on the properties of the LCNFs were discussed. The results shows that the LCNFs of 68.23 % yield can be obtained as pretreating APMP with DES compose of choline chloride/lactic acid (ChCl/LA) at 100 °C for 8 h followed by ultrasonic treatment for 30 min. The prepared LCNFs have a width of 6.90 nm and 8.65 % lignin content. The pulp refining before DES treatment affects the properties of the LCNFs. When the pulp is refined by PFI mill for 2500 revolutions before DES pretreatment, compared to the LCNFs obtained without refining, the LCNFs obtained from the refined pulp has a similar yield (64.37 %) and smaller width at milder DES treatment conditions (100 °C and 4 h), which indicates that the process of combination of the pulp refining and DES pretreatment improves the LCNFs fabrication efficiency.