Comparative Study of Cellulose Extraction from Wheat Straw: Structural, Morphological, and Thermal Characterisation

The growing demand for sustainable and biodegradable materials has increased interest in utilising agricultural residues as renewable sources of cellulose. Wheat straw is an abundant lignocellulosic by-product with significant potential for value-added applications. However, the efficiency of different cellulose extraction methods and their effects on cellulose properties remain insufficiently compared. This study evaluated three chemical extraction methods, i.e., acidified sodium chlorite (ASC), alkaline hydrogen peroxide (AHP), and peracetic acid (PAA), for isolating cellulose from wheat straw. The extracted cellulose was characterised in terms of extraction yield, chemical structure, crystallinity, surface morphology, and thermal stability using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). PAA produced the highest cellulose yield (40.91%), followed by AHP (39.33%) and ASC (23.41%). FTIR spectra confirmed the effective removal of lignin and hemicellulose by all three methods while preserving the cellulose structure. XRD analysis showed increased crystallinity after extraction, with PAA exhibiting the highest crystallinity index (74.58%), followed by AHP (72.97%) and ASC (72.09%). SEM observations revealed that PAA generated a more porous and disrupted fibre morphology, whereas ASC better preserved the fibre structure. Thermal analysis indicated that ASC-extracted cellulose exhibited the greatest thermal stability, while PAA and AHP provided higher cellulose recovery and greater fibre opening. Overall, the results demonstrate that the choice of extraction method significantly influences the physicochemical properties of wheat straw cellulose. PAA is the most suitable method when high cellulose yield and crystallinity are desired, whereas ASC is preferable for applications requiring enhanced thermal stability. The extracted cellulose shows considerable potential as a sustainable reinforcement material for biocomposites, biodegradable food packaging, particle boards, and other bio-based products.