Oral Presentation Royal Australian Chemical Institute National Congress 2026

Visible-light degradation of PFAS: Forever Chemicals are not forever anymore! (136888)

Mahmoud Adel Hamza 1 , Yideng Shen 1 , Alex Keltie 1 , Cameron Shearer 1
  1. Adelaide University, Adelaide, SOUTHE AUSTRALIA, Australia

Per- and poly-fluoroalkyl substances (PFAS, forever chemicals) constitute a class of persistent organic pollutants that severely affect human health and the environment owing to their resistance to degradation by traditional water treatment methods. Semiconductor-assisted photocatalysis has the potential to be a green method to achieve complete mineralization of PFAS. Metal sulfide photocatalysts, including zinc indium sulfide (ZnIn2S4), have shown promising activity toward the sunlight-driven photodegradation of various water pollutants.1 However, only a few studies have investigated them for the photodegradation of more persistent chemicals such as per- and poly-fluoroalkyl substances (PFAS).2,3 Herein, we fabricate ZnIn2S4 microspheres/nanosheets using solvothermal synthesis and investigate their photocatalytic activity toward the photoreductive degradation of perfluorooctanesulfonic acid (PFOS). Other visible light active photocatalysts such as cadmium indium sulfide (CdIn2S4), cadmium sulfide (CdS), and graphitic carbon nitride (g-C3N4) were prepared and characterized. The PFOS photodegradation under 365 nm irradiation was compared between ZnIn2S4, CdIn2S4, CdS, and g-C3N4, along with TiO2. PFOS removal was monitored by a combination of fluorine-19 nuclear magnetic resonance (19F-NMR) and liquid-chromatography mass spectrometry (LC-MS). To confirm cleavage of the C–F bond, the evolution of F- ions was monitored with a fluoride ion selective electrode and confirmed by 19F-NMR. The metal sulfides including ZnIn2S4 displayed significant production of fluoride (F–) ions (35 ± 13 ppm) and no PFAS by-products in the post-reaction solutions (from LC-MS), confirming PFOS mineralization (69 ± 26%). Radical scavenger experiments are used to investigate the mechanism and reactive species involved in PFOS degradation. It was determined that photoexcited electrons drive the reduction of PFOS. Importantly, ZnIn2S4 could degrade PFOS under visible light irradiation (455 nm). Finally, ZnIn2S4 was used for the photodegradation of a field-derived mixed PFAS sample and high mineralization of the complex sample is achieved.

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