Cellulose nanowhiskers separated from a bio-residue from wood bioethanol production

The aim of this study was to explore the utilization of industrial bio-residues as a source of raw material for the industrial production of cellulose nanowhiskers. The used residue, obtained from a bioethanol pilot plant, was first purified using chemical extraction and bleaching, and then separated to nanowhiskers by mechanical treatments such as ultrasonication, high-pressure homogenization as well as chemical acid hydrolysis. The chemical compositions and characteristics of the bio-residue were studied before and after purification using a TAPPI standard, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The morphology of the isolated nanowhiskers was characterized using atomic force microscope (AFM). The chemical composition of the used bio-residue was found to be 49.5 wt% cellulose, 42.1 wt% lignin and 8.4 wt% extractives. The crystallinity of the bio-residue was 14.5% and it increased to more than 73% after the purification process. The nanowhiskers isolated using ultrasonication or high-pressure homogenization had better thermal stability than nanowhiskers isolated with acid hydrolysis. The AFM study showed that a simple ultrasonication and homogenization processes resulted in nanosize whiskers with diameters in the 10–20 nm range.