Exploring the potential antibacterial mechanism of the goose eggshell-derived CaO nanoparticles for deactivation of pharmaceutical wastages and bacteria

Environmental contamination caused by pharmaceutical residues and textile dye effluents poses significant challenges due to their chemical stability, toxicity, and resistance to conventional treatment methods. This study investigates the green synthesis of calcium oxide (CaO) NPS derived from goose eggshells via thermal decomposition at 900 °C, and evaluates their efficacy in photocatalytic degradation and antibacterial applications. Comprehensive characterization using XRD, FTIR, FESEM, UV–Vis studies confirmed the successful formation of phase-pure, highly crystalline CaO NPS with an average particle size of 47.9 nm and a direct optical bandgap of 3.41 eV. The photocatalytic performance of the synthesized CaO Nanoparticles (NPs) was assessed through the degradation of Safranin dye (a model cationic dye) and the pharmaceutical compound Paracetamol under natural sunlight. The NPS achieved degradation efficiencies of 97.43 % for Safranin and 91.25 % for Paracetamol, following pseudo-first-order kinetics. The degradation rate constant for Safranin (2.896 × 10⁻² min⁻¹) was higher than that for Paracetamol (1.551 × 10⁻² min⁻¹), likely due to more favourable adsorption and stronger electrostatic interactions between the cationic dye molecules and the negatively charged CaO surface. In addition to their photocatalytic properties, the CaO NPS demonstrated significant antibacterial activity, particularly against Gram-positive Staphylococcus aureus, with a maximum zone of inhibition of 19.4 mm. The enhanced antibacterial performance is attributed to the nanoscale size, high surface reactivity, and the alkaline nature of CaO, which collectively disrupt bacterial membrane integrity. Overall, this work underscores the potential of bio-waste-derived CaO NPS as an environmentally sustainable, cost-effective, and multifunctional material for the dual purpose of wastewater remediation and microbial control.