Photocatalytic Degradation of Recalcitrant Organics in Oil Sands Process Water Using Facile Synthesized ZnO and BaO@ZnO Nanoparticles: Impact of Oxide Coupling on Degradation Kinetics and Toxicity Reduction

With increasing interest in the effective treatment of oil sands process water (OSPW), advanced oxidation processes (AOPs), particularly semiconductor-based photocatalysis, are gaining attention as promising, cost-effective, and efficient remediation techniques. In this study, zinc oxide (ZnO) and barium oxide-modified ZnO (BaO@ZnO) nanomaterials were synthesized via chemical precipitation, and the Ba-to-Zn molar ratio was optimized to enhance photocatalytic activity. This study investigates the solar-activated photocatalytic degradation of recalcitrant organic compounds in oil sands process water (OSPW) using zinc oxide (ZnO) and composite BaO@ZnO nanoparticles synthesized via chemical precipitation. The optimal composite ratio (2% mol Ba/Zn) was identified to enhance photocatalytic performance without altering ZnO’s crystal structure, significantly reducing electron–hole recombination. Under simulated solar radiation, 2%BaO@ZnO achieved ∼97% degradation of classical naphthenic acids (O2–NAs), outperforming pristine ZnO (∼90%) and demonstrating superior degradation of aromatic fluorophores. Electron paramagnetic resonance and scavenger studies confirmed that •OH, h+, and 1O2 were the primary reactive species. Acute toxicity, bioaccumulation potential, and genotoxicity of OSPW were substantially reduced post-treatment. These results highlight BaO@ZnO as a highly efficient, stable, and solar-responsive photocatalyst for sustainable remediation and reuse of OSPW.