Sugarcane trash-derived nanocrystalline cellulose: a sustainable approach with mild chemical pretreatment and comprehensive characterisation.

Cellulose-rich sugarcane trash (SCT) biomass, an important agricultural residue generated in large quantities every year, was used as a potential feedstock for cellulose extraction in micro and nano form. Initially, the cellulose microfibers were isolated from the SCT by a two-step chemical treatment process (alkali pretreatment with sodium hydroxide followed by hydrogen peroxide bleaching) at different operating parameters. The microfibers were then converted into the nanoscale by acid hydrolysis. The quantification of the raw and chemically treated SCT was carried out by the Van Soest method to learn their chemical composition. Different characterisation techniques such as Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD), Field Emission-Scanning Electron Microscopy (FE-SEM), and Transmission Electron Microscopy (TEM) were used for the analysis of surface functional groups, thermal stability, crystallinity index, surface morphology, and the internal structure of the raw as well as chemically treated SCT biomass respectively. The quantification results show the optimum process conditions for the alkali pretreatment as 5% (w/v) alkali (NaOH) concentration, 60 °C, and 12 h process time and for bleaching as 20% H₂O₂ concentration, 80 °C, and 8 h process time. This produces material having 86.15% cellulose content. This indicates the effective removal of hemicellulose and lignin. For the acid hydrolysis reaction for converting cellulose microfibers into nanocrystalline cellulose, the concentration of H₂SO₄ required was 40 wt.%, which is comparatively lower than that reported in the literature (~ 65 wt.%). The characterisation results highlight the progressive enrichment in the cellulosic groups, thermal stability, and crystallinity of the material with respect to the processing stages. There was a progressive enhancement in the crystallinity index of the sample observed with respect to the chemical treatment, with a maximum of up to 84.83% for the hydrolysed material. The XRD and TEM analysis confirms the presence of nanocrystalline cellulose (NCC) in the final hydrolysed sample. [ABSTRACT FROM AUTHOR]