Solar photocatalytic treatment of model and real oil sands process water naphthenic acids by bismuth tungstate: Effect of catalyst morphology and cations on the degradation kinetics and pathways.

Abstract Bitumen extraction from oil sands produced large quantities of oil sands process water (OSPW), which contains highly recalcitrant naphthenic acids (NAs). In this study, three different morphologies of bismuth tungstate (Bi2WO6) photocatalysts were prepared by hydrothermal method. The prepared catalyst was characterized to obtain its structural, textural and chemical properties and tested for the degradation of model NAs and real OSPW under simulated solar irradiation. Nanoplate, flower-like and swirl-like Bi2WO6 were prepared with the flower-like structure exhibited highest specific surface area and total pore volume. Highest photocatalytic activity for the degradation of NAs was also demonstrated by the flower-like Bi2WO6, achieving complete degradation of cyclohexanoic acid (CHA) at fluence-based rate constant of 0.0929 cm2/J. O2•− and holesare identified as the major reactive species generated during the photocatalytic process. The effect of metallic ions on the degradation rates of S-containing and N-containing NAs differs and heteroatom was the main reactive site. The by-products of heteroatomic NAs were identified and degradation pathways were reported for the first time. The concentration changes of each byproduct were further estimated by mass balance. This research will provide valuable information for the treatment of NAs by engineered passive solar-based approaches.