CdIn₂S₄ Micro-Pyramids for Reductive Photocatalytic Degradation of Perfluorooctanesulfonic Acid

Per- and poly-fluoroalkyl substances (PFAS) 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. Cadmium indium sulfide (CdIn₂S₄) is an exciting photocatalytic material because of its high visible light harvesting capacity and high reduction potential. However, CdIn₂S₄ has not been investigated for PFAS degradation. Herein, CdIn₂S₄ micro-pyramids are fabricated via solvothermal synthesis, and their photocatalytic activity toward the photodegradation of perfluorooctanesulfonic acid (PFOS) is investigated. The reaction conditions, such as the light source and the light power are optimized. The findings show the capability of CdIn₂S₄ to achieve almost complete degradation and defluorination of PFOS (removal% = 99 ± 7% and defluorination% = 97 ± 22%) under optimized conditions. From radical quenching experiments, it is found that the mechanism of degradation is via photoelectron reduction. CdIn₂S₄ shows an outstanding performance toward the degradation of the PFAS sample derived from a contaminated facility in South Australia. This work opens the door for investigating other CdIn₂S₄-based photocatalysts and other metal sulfide-based photocatalysts for the degradation of PFAS.