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A novel photocatalyst, Bi 2 WO 6 /NiO/Ag, with hierarchical flower-like Z-scheme heterojunction, which exhibited excellent stability and photocatalytic activity over a wide light spectrum, was firstly synthesized and used in the remediation of real oil sands process water (OSPW) and achieved complete removal of aromatics, classical naphthenic acids (NAs), and heteroatomic NAs after 6 h of photocatalytic treatment. The acute toxicity of OSPW was completely eliminated after only 2 h of treatment. h+ and ∙OH were found to be the major oxidative species in the photocatalytic system. The enhanced photocatalytic efficiency is the result of the unique Z-scheme electron transfer among electron mediators Ag, NiO, and Bi 2 WO 6 , which was supported by the in-situ irradiated XPS. The study benefits the design of engineered passive treatment approach for OSPW remediation through solar light-driven catalyst. [Display omitted] • 3D flower-like Z scheme photocatalyst Bi 2 WO 6 /NiO/Ag was synthesized. • Bi 2 WO 6 /NiO/Ag effectively treated OSPW with 90% degradation of O 2 -NAs within 3 hrs. • Aromatics with three fused rings were more prone to degradation than single and two-ring aromatics. • NAs with different carbon number and DBE showed different degradation behaviors. • Z-scheme structure enhanced the photocatalytic activity and was verified by in-situ irradiated XPS. [ABSTRACT FROM AUTHOR]

Naphthenic acids (NAs) are reported to be the main species responsible for the oil sands process-affected water (OSPW) toxicity. In this study, the degradation of cyclohexanoic acid (CHA) as a model compound for NAs by an ethylenediamine- N , N ’-disuccinic acid (EDDS)-modified Fenton process was investigated at pH 8. Optimum dose for Fe-EDDS (EDDS:Fe = 2:1) was 0.45 mM, and 2.94 mM for hydrogen peroxide (H 2 O 2 ). The time profiles of the main species in the process were studied, including CHA, H 2 O 2 , Fe(II), total Fe, and Fe-EDDS (in the main form of Fe III EDDS). The second-order rate constant between EDDS and hydroxyl radical ( OH) at pH 8 was obtained as 2.48 ± 0.43 × 10 9 M −1 s −1 . OH was proved to be the main species responsible for the CHA degradation, while superoxide radical (O 2 − ) played a minor role. The consecutive addition of H 2 O 2 and Fe-EDDS led to a higher removal of CHA compared to that achieved by adding the reagents at a time. The half-wave potential of Fe III/II EDDS was measured at pH 7–9. The EDDS-modified Fenton process is a promising alternative to degrade NAs. [ABSTRACT FROM AUTHOR]