Harnessing sunlight for effective passive photocatalytic treatment of oil sands process water using a sustainable floating composite catalyst

The study explores a sustainable passive photocatalytic treatment method for oil sands process water (OSPW) using a pumice-ZnO composite catalyst. The composite material was fabricated via a reproducible, low-chemical-input coating technique and designed to float, harnessing solar energy without mechanical mixing. Structural and chemical characterization of the fabricated composite indicated that the ZnO nanoparticles were strongly bound to the surface of pumice stone particles. Its application under both simulated and real sunlight demonstrated high degradation efficiencies for naphthenic acids (NAs) and fluorophore organic compounds. A 91.5% degradation of classical NAs was achieved under simulated solar irradiation (2.484 MJ/m²), while natural sunlight exposure (average 2.461 MJ/m²) resulted in ~72% degradation of classical NAs. The catalyst showed excellent reusability and stability over repeated cycles, with minimal leaching. Toxicity and bioavailability assessments confirmed significant reductions in acute toxicity and bioavailable organics in treated samples. These findings demonstrate the promise of this floating photocatalyst for scalable, solar-powered treatment of OSPW, offering an energy-efficient and environmentally friendly remediation approach. • A sustainable composite photocatalyst was innovatively fabricated with pumice and ZnO nanoparticles. • Pumice-ZnO composite effectively harnessed natural solar radiation for photocatalytic degradation of organics in OSPW. • The passive photocatalytic treatment of OSPW under sunlight significantly reduced toxicity and bioavailability.