Choline chloride based deep eutectic solvents for the lignocellulose nanofibril production from Mongolian oak (Quercus mongolica)

Lignocellulose nanofibrils (LCNFs) were produced from the biomass of Mongolian oak for the first time using deep eutectic solvent pretreatment and mechanical defibrillation. Three Choline chloride (CC)-based DESs were selected and the effect of various DES pretreatment conditions on the chemical composition of wood sample was studied first. CC/lactic acid (CC/LA) pretreatment caused high lignin and hemicellulose removal whereas CC/urea (CC/U) and CC/glycerin (CC/GLY) pretreatment increased the fiber's susceptibility to defibrillation. With the significant influence of temperature, its effect on the subsequent mechanical defibrillation was also studied. For all three DESs, pretreatment condition of 1:2 mol ratio, 6 h time, and 140 degrees C was found optimal for LCNF preparation. LCNFs with diameter < 10 nm, cellulose I crystal structure and similar to 60% crystallinity were obtained. LCNFs from CC/U and CC/GLY pretreatments exhibited high tensile strength (similar to 73 MPa), elastic modulus (similar to 1500 MPa) and high thermal stability (T-max similar to 361 degrees C). Additionally, CC/LA pretreatment offered a high amount of regenerated lignin which was also characterized.

Automated summary

In this study, Lignocellulose nanofibrils (LCNFs) were successfully produced from Mongolian oak biomass for the first time using deep eutectic solvent pretreatment and mechanical defibrillation. The desirability of the CC/LA pretreatment for high lignin and hemicellulose removal, as well as the enhanced fiber's susceptibility to defibrillation with CC/U and CC/GLY pretreatments, was demonstrated. The optimal conditions for LCNF preparation were found to be a 1:2 mol ratio, 6 hours time, and 140 degrees C, resulting in nanofibrils with high tensile strength, elastic modulus, and thermal stability.