Abstract: The cellulose nanocrystals (CNCs) were prepared by ammonium persulfate oxidation of hybrid poplar residue obtained after the extraction of hemicellulose. The starting material was treated by 1.5 mol/L ammonium persulfate solution at 70℃ for 16 h, and the ratio of the solid to the liquid was 1:100(g:mL). The resulting CNCs were white powder and the yield(calculated by the mass of cellulose in the starting material) was 57%, the oxidation degree of CNCs was 0.156 and the surface charge was -42.15 mV. The CNCs were mainly characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and nuclear magnetic resonance. The results showed that ammonium persulfate could remove the lignin and residual hemicellulose in the starting material and selectively oxidize the hydroxyl groups at the position of cellulose C6 to carboxyl groups. The cellulose nanocrystals kept the structural characteristics of the raw cellulose. The crystal structure of the CNCs, which had a crystallinity index of 77%, was dominated by I_β, and 88.4% of them had a width of 10-24 nm.

Key words: ammonium persulfate, hybrid poplar residues, cellulose nanocrystals, characterizations