Microwave-synthesised BiOI photocatalysts and their performance for the degradation of PFOA in different water matrices

The persistent and bioaccumulative nature of perfluorooctanoic acid (PFOA) poses a major environmental challenge, demanding efficient and sustainable remediation strategies. In this study, bismuth oxyiodide (BiOI) nanoparticles were synthesised via a rapid microwave-assisted method using different concentrations of cetyltrimethylammonium iodide (CTAI) as the iodine precursor (1–15 mM). Increasing CTAI concentration improved the crystallinity and narrowed the bandgap (<2.0 eV), enhancing visible-light absorption and surface charge. A Box-Behnken experimental design was applied to optimize the key operational parameters for PFOA removal. The photocatalytic degradation of PFOA was then evaluated under UV and visible irradiation using PFOA solutions prepared in three different water matrices: distilled water (DW), river water (RW), and textile wastewater (WW). The BiOI@8 mM CTAI and BiOI@15 mM CTAI samples exhibited high removal efficiencies through combined adsorption and photocatalysis. Under irradiation, PFOA degradation followed three main routes, decarboxylation, chain shortening, and defluorination, and several transformation products were identified. Despite a transient increase in toxicity due to short-chain intermediates, extended irradiation resulted in marked detoxification, especially for BiOI@15 mM CTAI under visible light. Overall, BiOI nanoparticles demonstrated high stability, visible-light activity, and dual adsorptive-photocatalytic performance, enabling the effective degradation and detoxification of PFOA even in complex water matrices. These results highlight the potential of microwave-synthesised BiOI as a promising photocatalyst for the remediation of persistent fluorinated pollutants under low-energy, environmentally friendly conditions.