Eggshell waste derived CaO as a tribocatalyst for removal of Rhodamine B dye under ambient light and sunlight

Calcium oxide (CaO) was synthesized from waste chicken eggshells through calcination at 900 °C and examined to determine catalytic efficiency in degrading Rhodamine B (RhB) dye. Although CaO exhibits photocatalytic properties, to enhance its catalytic performance, a tribocatalytic and solar-tribocatalytic approach was utilized for RhB dye degradation. The material was characterized using X-ray diffraction, Raman spectroscopy, Photoluminescence, Diffuse reflectance spectrum, X-ray photoelectron spectroscopy and Scanning electron microscopy with energy-dispersive X-ray spectroscopy to analyze its structural and morphological properties. The degradation percentages achieved within 240 min were 33% ± 1.4% for photocatalysis, 75% ± 2.0% for tribocatalysis, and 91% ± 1.6% for solar-tribocatalysis, respectively. Furthermore, the effects of key experimental factors, including solution pH, presence of light source and surface area of polytetrafluoroethylene (PTFE), were investigated under tribocatalytic conditions. Scavenger analysis identified superoxide radicals (O₂^.-) as the primary agents responsible for degrading the chromophoric structure of RhB.