Mint-assisted green synthesis of cerium oxide-based hydroxyapatite–alginate nanocomposite for cefazolin degradation

Abstract

Cefazolin, a widely used first-generation cephalosporin, is frequently found in hospital wastewater (10–1000 μg/L), raising environmental concerns. However, sustainable and reusable photocatalytic systems based on green-synthesized CeO₂ nanoparticles and ternary composites for its removal remain underexplored. This study developed a green synthesis approach for cerium oxide nanoparticles (CeO₂ NPs) using Mint (Mentha spicata) and Mentha pulegium extracts to efficiently remove cefazolin from contaminated water. The specific phytochemicals responsible for Ce³⁺ reduction—including rosmarinic acid and luteolin in Mint, and pulegone-associated flavonoids in Mentha pulegium—were identified and their mechanistic role in nanoparticle formation is discussed. To enhance degradation efficiency, ultraviolet (UV) radiation was combined with a CeO₂ nanoparticle/hydroxyapatite/calcium alginate nanocomposite, creating a powerful and reusable photocatalytic system. The synthesized nanomaterials were extensively characterized by FESEM, TEM, FTIR, XRD, EDX, and ICP-OES. The average crystallite size was 16.2 nm (Scherrer equation) and particle sizes ranged from 30 to 80 nm. Scavenger experiments confirmed ·OH radicals as the dominant reactive oxygen species. Pseudo-first-order degradation kinetics were observed (k = 0.089 min⁻¹ for Mint-CeO₂), and Langmuir isotherm modeling yielded a maximum adsorption capacity of 48.3 mg/g. The optimal removal efficiency of 96% was achieved under the following conditions: 30-min incubation, 0.8 g CeO₂ NPs, 0.6 g Mentha pulegium NPs, pH 7.5, and a 20 ppm cefazolin concentration. These results highlight the remarkable potential of UV-activated CeO₂-based nanocomposites as a highly efficient, sustainable, and eco-friendly strategy for eliminating antibiotic contaminants from water sources.