Removal of Pb(II) Ions from Aqueous Media via Precipitation Using Eggshell-Derived CaO

The rapid growth of the global population has increased the consumption of chicken eggs, leading to the generation of significant quantities of eggshell waste. The sustainable valorization of this biowaste represents an important environmental and resource management challenge. In this study, CaO was synthesized from waste chicken eggshells via calcination at 800 °C and evaluated as a green precipitating agent for the removal of toxic Pb(II) from aqueous solutions. The effects of key precipitation parameters, including initial pH, stirring speed, contact time, and CaO dosage, were systematically investigated. The results showed that the removal efficiency increased with increasing pH, mixing intensity, contact time, and CaO dosage, reaching a maximum Pb(II) removal of 90% under investigated conditions of initial pH 9, stirring speed of 500 rpm, contact time of 15 min, and CaO dosage of 500 mg. In the presence of the competing ion Fe(III), the removal efficiency further increased to 99.99%, indicating a potential synergistic effect in the precipitation process. FT-IR analysis confirmed the successful formation of CaO and revealed significant spectral changes after Pb(II) precipitation, including shifts and disappearance of characteristic absorption bands, indicating the formation of insoluble hydroxide and carbonate phases. These findings demonstrate that eggshell-derived CaO is an effective and environmentally sustainable material for Pb(II) removal from aqueous media and represents a promising approach for the valorization of eggshell waste.