Phase Identification and Characterization of Sustainable Oxide Precursors Derived from Waste Materials by X-ray Diffraction

The growing accumulation of solid waste has intensified interest in sustainable resource recovery and circular material utilization in materials science. Consequently, waste streams are increasingly regarded as alternative sources of technologically important oxides for glass and ceramic fabrication. This study focuses on the identification and structural characterization of oxide precursors derived from diverse waste materials, with emphasis on phase verification and suitability for advanced glass systems. Aluminum, calcium, silicon, and zinc oxide precursors were synthesized from waste aluminum beverage cans, chicken eggshells, waste container glass, coconut shells, and spent zinc–carbon batteries using simple hydrometallurgical, alkali-based, and thermal extraction routes. X-ray diffraction (XRD) patterns recorded over 2θ = 10–80° using Cu–Kα radiation (λ = 1.5406 Å) confirmed phase formation in all extracted oxide systems. The ZnO sample exhibited intense reflections at 2θ ≈ 31.7°, 34.4°, and 36.2°, indexed to the (100), (002), and (101) planes of hexagonal wurtzite ZnO (ICDD PDF 00-036-1451). Analysis of the full width at half maximum (FWHM) of the dominant (101) peak indicated an average crystallite size in the nanometer range. Silica recovered from waste container glass displayed a broad amorphous hump centered at 2θ ≈ 22°, confirming the absence of long-range order. In contrast, coconut-shell-derived silica showed crystalline quartz reflections at 2θ ≈ 20.8°, 26.6°, 36.5°, and 50.1°, corresponding to α-SiO₂, together with minor aluminosilicate phases. The eggshell-derived calcium system exhibited peaks at 2θ ≈ 29.4° (CaCO₃), 34.1° (Ca(OH)₂), and 37.3° (CaO), while the aluminum-based precursor showed boehmite reflections at 2θ ≈ 14.5°, 28.5°, and 38.3°. Overall, the waste-derived oxides occur as reactive or multiphase systems but remain structurally compatible with glass and ceramic processing.