Photocatalytic degradation of perfluorooctanoic acid using a ferrite bismuth nanocomposite under UVC irradiation: degradation pathway, toxicity assessment, statistical analysis and optimization

• BiFeO₃/CNT photocatalyst was synthesized to evaluate its efficiency for the removal of perfluorooctanoic acid (PFOA). • PFOA pose significant environmental challenges owing to their persistence and toxicity. • BiFeO₃/CNT composite demonstrated synergistic adsorption capacity and photocatalytic activity, achieving rapid and nearly complete degradation of PFOA (up to 99%). • ECOSAR predictions indicated that the primary degradation by-products of PFOA (P1 and P2) exhibited lower acute and chronic toxicity compared to the parent compound, whereas some secondary by-products (P6) may have higher toxicity, emphasizing the need for environmental monitoring. • BiFeO₃/CNT photocatalyst is highly effective for degradation of PFOA from contaminated water, contributing to improved environmental health. Per- and polyfluoroalkyl substances (PFAS) are a class of highly stable fluorinated compounds widely used since the 1940s due to their exceptional thermal and chemical resistance. These compounds pose significant environmental challenges owing to their persistence and toxicity, as well as resistance to conventional water treatment methods. In this study, the BiFeO 3 /CNT photocatalyst was synthesized in laboratory and employed to evaluate its efficiency for the removal of perfluorooctanoic acid (PFOA), a representative PFAS, from aqueous environments. Batch experiments were conducted under UVC irradiation (254 nm, 18 W) with varying catalyst dosages, reaction times, and pH values to investigate the effect of these parameters on PFOA degradation. The BiFeO₃/CNT composite demonstrated synergistic adsorption capacity and photocatalytic activity, enabling rapid and complete degradation of PFOA. Under experimental conditions of 500 ppb PFOA concentration, 3.5 g/L BiFeO₃/CNT dosage, and pH 2.0, over 99% of PFOA was degraded within 18 hours under UVC irradiation. The degradation mechanism involved photocatalytic hole oxidation and cleavage of strong C–F bonds, producing six degradation by-products with varying chain lengths. ECOSAR simulations indicated that the acute and chronic toxicity of PFOA degradation by-products formed in the BiFeO₃/CNT/UVC system was relatively reduced. Overall, the findings demonstrate that the BiFeO₃/CNT photocatalyst is highly effective for the degradation of PFOA from contaminated water, contributing to improved environmental health.