Valorization of agro-waste like corncob into a value-added commodity such as cellulose nanocrystals (CNCs) could be instrumental in addressing issues related to waste management, thereby paving the way toward a circular economy. In this study, cellulose nanocrystals were prepared from corncobs via acid hydrolysis using a mixture of sulfuric acid and Oxalic acid dihydrate in a mass ratio of 1:5. The synthesized CNCs were functionalized using hexadecyl trimethyl ammonium bromide (HDTMA-Br) to enhance their usability in a variety of applications. The functionalized and unfunctionalized CNCs were characterized using characterization techniques such as Scanning Electron Microscopy (SEM), Fourier Transform Infra-red (FTIR) spectroscopy, X-ray Diffraction (XRD), and Thermogravimetric analysis (TGA), to check the surface morphology, surface chemistry, crystallinity, and thermal stability, respectively. SEM images revealed that the synthesized CNCs have fibrous structure and individual particles can be easily seen, indicating that there was sufficient hydrolysis. Also, the SEM images showed that the functionalized CNCs possessed a highly porous surface compared to that of the non-functionalized CNCs. According to the XRD pattern, a strong peak that appeared at 22.4<sup>o</sup> was considered for the determination of the crystallinity of raw cellulose and that of the CNCs. About 55.25% yield of cellulose nanocrystal (CNC) was obtained, and the crystallinity of the raw cellulose and the extracted CNCs was 64.5% and 78.9%, respectively. In addition, the XRD analysis also showed increased peak intensity after the functionalization of the CNCs, indicating enhanced crystallinity of the CNCs. Furthermore, the appearance of a peak around 30.3° indicates the attachment of HDTMA-Br to the surface of the CNCs. FTIR spectra revealed the attachment of additional functional groups, methyl, and methylene groups, onto the surface of the CNCs after the functionalization. TGA analysis indicated that functionalized CNCs were more thermally stable compared to non-functionalized CNCs.The on-set degradation temperatures of the fCNCs and CNCs were 375°C and 343<sup>o</sup>C, respectively. As observed from the characterization results, the cellulose nanocrystals were successfully extracted from waste corncobs and functionalized with HDTMA-Br. The surface properties of the modified CNCs were considerably enhanced, thereby increasing their potential use in a wide range of applications.

Synthesis, functionalization, and characterization of cellulose nanocrystals (CNCs) obtained from South African waste corncobs

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