Abstract: In order to promote the high-value utilization of lemon processing by-products, an high-efficiency method for the preparation of lemon seed cellulose nanofibrils (LSCNF) was developed by mechanical ball milling with different concentrations (0–50%) of the ionic liquid 1-butyl-3-methylimidazole chloride ([BMIM]Cl) as a wet milling medium in this study. The morphology and structure of LSCNF were characterized by atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetry (TG). The results showed that the length of LSCNF was reduced, while the diameter was increased with the increase of [BMIM]Cl concentration. The LSCNF prepared with 50% [BMIM]Cl showed the smallest length but a large diameter (40–60 nm). The XRD and FTIR results showed that all obtained LSCNFs formed cellulose Iβ crystals, and the addition of [BMIM]Cl had a certain protective effect on the crystallinity of LSCNF. The TG results showed that the residual amount of LSCNF after ionic liquid-assisted ball milling was similar to lemon seed cellulose (LSC) at 500 ℃, and both of them were higher than that of LSCNF prepared by ball milling. The rheological results showed that LSCNF suspensions showed a non-Newtonian behavior, and the relative viscosity of LSCNF with longer length was higher at a constant shear rate. In summary, ionic liquid-assisted ball milling is a green and efficient method to prepare lemon seed cellulose nanofibrils with controllable morphology and structure depending on the concentration of ionic liquids.

Key words: lemon seed; ionic liquid; ball milling; cellulose nanofibrils; structure