In Situ Growth of Polyindole within Montmorillonite Interlayer and Subsequent Efficient Destruction of Perfluorooctanoic Acid

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of emerging contaminants frequently detected in the environment and pose serious threats to human health. Previous studies have shown that techniques using hydrated electrons can effectively degrade these compounds. However, such reactions typically necessitate alkaline and anaerobic conditions or involve the use of surfactants. Herein, we introduced a novel approach that utilized indole as the monomer molecule for in situ polymerization within the clay interlayer to generate polyindole. In the system, polyindole could both serve as the precursor to provide hydrated electrons and, with its own organic polymer structure, create a hydrophobic phase to effectively adsorb perfluorooctanoic acid (PFOA). Without the need for surfactants, the "adsorption-concentration-reaction" strategy for PFOA could be realized. At the same time, as the degradation of PFOA by the generated hydrated electrons occurred mainly within the clay layers, the confinement effect could be harnessed to reduce the mass transfer of O₂ and H⁺ from the solution to the layers. It thereby weakened the quenching of hydrated electrons and enhanced their utilization efficiency. Therefore, this study represents a novel attempt to use in situ polymerization for constructing a polyindole-based nanocomposite, offering a sophisticated solution for degradation of PFASs.