Comparative extraction and characterisation of cellulose nanostructures from sawdust and maize stalk biomass
Edwin Makhado, Wilson M. Seleka, Louisah M. Mahlaule-Glory, Kgaugelo Selowa, Mahmoud H. Abu Elella, Orebotse Joseph Botlhoko, T.K. Satekge, Mpitloane J. Hato
Abstract
The conversion of agricultural waste into high-value nanoparticles presents a sustainable approach to waste management and the production of bio-based goods. This work effectively collected cellulose nanofibers and cellulose nanocrystals from agricultural leftovers using chemical methods. The resulting nanocelluloses were characterised through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) to ascertain their chemical structure, crystallinity, morphology, and thermal stability. XRD revealed a crystalline cellulose I structure for cellulose nanofibers and a crystalline cellulose Iβ structure for nanocrystals. The former exhibited a crystallinity index of 74.3 %, surpassing the cellulose nanocrystals index of 66.8 %. Cellulose nanocrystals exhibited reduced thermal stability compared to cellulose nanofibers throughout the analysed TGA range. The zeta potential (ζ) values were found to be -18.2 ± 085 mV for cellulose nanofibers and - 12.80 ± 1.91 mV for cellulose nanocrystals. The kinetic activation energy for cellulose nanofibers exceeds that of cellulose nanocrystals, as determined by the Broido and Coats-Redfern models. The research illustrates the viability of agricultural waste as a plentiful, renewable feedstock for the production of cellulose nanomaterials, which possess properties appropriate for use in biocomposites, films, hydrogels, and advanced functional materials, thereby aiding the advancement of sustainable circular bioeconomies.