| Abstract Scope |
Rising airborne pollutants and CO₂ emissions demand sustainable material-based remediation. This study reports the synthesis of the first nano multi-ion-doped hydroxyapatite (HAp) from waste eggshells and coral stones, supporting circular economy goals. Doping with Ag⁺, Srē⁺, Znē⁺, and F⁻ enhanced surface reactivity, thermal stability, and adsorption through lattice distortions and active sites. XRD confirmed high crystallinity (JCPDS 00-009-0432), while FTIR validated phosphate and hydroxyl groups. TEM showed irregular nanosized particles (20–600 nm), with rod-like morphologies for Sr/Zn doping. HRTEM and SAED confirmed polycrystalline features, and EDS mapping revealed uniform dopant distribution. BET analysis demonstrated mesoporosity, with surface areas of 0.471–0.557 mē/g, pore volumes of 0.00053–0.00059 cc/g, and average pore sizes of 4.23–4.64 nm, enabling selective CO₂ diffusion and adsorption. Unlike TiO₂ photocatalysts, the material functions effectively in both light and dark, making it suitable for indoor systems, reactors, and exhaust treatment, highlighting its promise in air purification and CO₂ capture. |