<![CDATA[This study presents a sustainable approach for synthesizing calcium peroxide (CaO₂) nanoparticles from biogenic eggshell waste as a potential adsorbent for wastewater treatment. Increasing water pollution caused by industrial and domestic activities has driven the demand for low-cost and environmentally friendly adsorbents. In this study, eggshells from various poultry sources were calcined at 900°C to produce CaO, followed by hydration and chemical precipitation using H₂O₂ to synthesize CaO₂. The resulting materials were dried at different temperatures (60–100°C) to evaluate the effect of thermal treatment on structural properties and adsorption performance. X-ray diffraction (XRD) analysis confirmed the formation of CaO₂ with nanoscale crystallite sizes ranging from 15.3 to 28.85 nm. Brunauer–Emmett–Teller (BET) analysis showed specific surface areas between 10.18 and 19.67 m²/g. Adsorption experiments using acetic acid revealed that performance was significantly influenced by precursor type and drying temperature. The highest adsorption capacity (347.54 mg/g) and removal efficiency (34.75%) were achieved using CaO₂ derived from free-range chicken eggshells at 80°C. This enhanced performance is attributed to the natural biogenic structure, mineral composition, and pore distribution. Overall, eggshell waste is a promising, sustainable, and cost-effective precursor for producing high-performance CaO₂ nanoparticles for wastewater treatment]]>
