Abstract
<title>Abstract</title> <p>The valorisation of agricultural residues into value-added engineering materials has attracted increasing interest as a means of reducing waste while developing renewable alternatives to conventional reinforcement materials. Soybean hull is an agro-industrial by-product containing substantial proportions of cellulose and hemicellulose and has previously been investigated as a source of cellulosic materials for reinforcement applications. This study investigated the synthesis and characterisation of reinforcement materials derived from soybean hull through chemical treatment and controlled thermal processing. Soybean hull samples were subjected to sulfuric acid treatment and subsequently pyrolysed at 600, 700, and 800°C, with untreated samples processed under corresponding temperatures serving as controls. The resulting materials were characterised using scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), and quantitative chemical analysis to evaluate changes in morphology, elemental and oxide composition, crystalline phases, and lignocellulosic constituents. The results showed that both chemical treatment and pyrolysis temperature influenced the physical and chemical characteristics of the resulting materials. SEM examination revealed progressive morphological transformation with increasing treatment temperature, including changes in surface texture, pore development, and particle structure. XRF analysis showed variations in the concentrations of major elemental and oxide constituents following treatment and pyrolysis, with the 800°C acid-treated sample exhibiting the highest measured silica and iron oxide contents among the investigated samples. XRD analysis identified quartz (SiO₂), graphite, and calcite as crystalline phases in the processed materials, while quantitative chemical analysis demonstrated substantial changes in the lignocellulosic constituents with increasing thermal treatment. In particular, hemicellulose exhibited greater susceptibility to thermal degradation than the more thermally resistant cellulose fraction. The combined results indicate that sulfuric acid treatment followed by controlled pyrolysis substantially altered the structural and chemical characteristics of the soybean hull. Among the investigated processing conditions, the acid-treated material produced at 800°C exhibited the most pronounced modification in morphology and mineral composition. Although composite fabrication and mechanical testing were beyond the scope of the present investigation, the resulting characteristics indicate that the processed soybean hull material warrants further investigation as a potential renewable reinforcement or filler for composite materials. The study demonstrates a route for converting soybean hull agro-waste into a characterised value-added material and provides a basis for subsequent investigations of its performance in polymer and other composite matrices.</p>