Extraction and characterization of cellulose nanocrystals from distilled grain waste

Cellulose nanocrystals (CNCs) with surface dialdehyde groups were prepared from purified cellulose extracted from distilled grain waste – an underutilized biorefinery byproduct – using sodium periodate (NaIO4) oxidation and sulfuric acid (H2SO4) hydrolysis. This work establishes distilled grain waste as a sustainable alternative to conventional cellulose sources for functional nanocellulose production. CNCs from Chinese liquor and beer waste were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis. XRD revealed a decrease in crystallinity index (CrI) after oxidation and hydrolysis, with CrI values of 57% and 61%, respectively, while maintaining the cellulose I structure. FTIR confirmed the removal of noncellulosic compounds and partial oxidation. TEM showed rod-shaped CNCs with average dimensions of 140 ± 63 nm in length and 12 ± 3 nm in width. Thermal analysis indicated early dehydration and high char formation, with a maximum thermal stability (Tmax) of 218°C. The process achieved high aldehyde functionality (2.13 mmol/g) without energy-intensive mechanical pretreatment, demonstrating feasibility for scalable biorefinery integration.