Cerium Oxide Nanoparticles: Synthesis, Characterization, Cytotoxicity, and Comparative Evaluation of Photocatalytic Degradation of Atrazine and Simazine

Abstract Cerium oxide (CeO₂) nanoparticles were synthesised and evaluated as photocatalysts for the removal of the herbicides atrazine (ATR) and simazine (SIM) under UV/H₂O₂. Phase-pure, nanoscale CeO₂ was obtained. Under near-neutral conditions, the CeO₂/H₂O₂ system achieved high removals, with an optimal oxidant window at ~ 10 mM delivering ≈ 96–97% degradation for both analytes. Performance depended on catalyst dose, increasing to maxima of ~ 0.08–0.10 g before levelling due to optical shielding and aggregation. Kinetic fits showed good linearity for both first and second-order models; SIM consistently degraded faster (1.915 × 10⁻ 4 min⁻ 1 ) than ATR (1.199 × 10⁻ 4 min⁻ 1 ). Importantly, in-vitro cytotoxicity assays indicated that the degradation products were less harmful than the parent compounds. Both herbicides exhibited reduced cytotoxicity after degradation, yet simazine degradation resulted in higher cytotoxicity (13.07%) than atrazine’s (10.41%). Overall, this study establishes CeO₂ as an effective, accessible photocatalyst for triazine removal and maps practical operating ranges (pH, oxidant, and dose) to inform process design for advanced oxidation treatment of herbicide-impacted waters.