Sustainable protein-assisted sol–gel synthesis of α-Al₂O₃ from raw goat milk whey as a bio-based chelating agent

The valorization of agro-industrial by-products offers a sustainable alternative to conventional synthetic additives in sol–gel processes. This study reports a protein-assisted sol–gel route for the synthesis of α-Al₂O₃ using raw goat milk whey (RGMW) as a bio-based chelating agent. The precursor gel, prepared from aluminum nitrate and citric acid with RGMW incorporation, was calcined between 900 and 1100 °C. Thermal analysis indicated the decomposition of the organic matrix and the onset of α-phase crystallisation above 1000 °C. X-ray diffraction with Rietveld refinement confirmed the formation of single-phase α-Al₂O₃ at 1100 °C with a nanoscale crystallite size. FT-IR analysis supported this transformation through characteristic Al–O vibrational bands. X-ray fluorescence revealed a high Al₂O₃ content (96.27 ± 0.69 wt%) with minor residual oxides attributed to the mineral composition of the whey, decreasing with increasing calcination temperature. Scanning electron microscopy showed agglomerated particles with irregular polyhedral morphology typical of sol–gel-derived materials. These results demonstrate that RGMW is an effective bio-based chelating agent and enables the synthesis of α-Al₂O₃ at relatively lower temperatures compared to conventional methods, highlighting its potential as a green route for advanced ceramic processing.