Supramolecular assemblies of a newly developed indole derivative for selective adsorption and photo-destruction of perfluoroalkyl substances

Per-/polyfluoroalkyl substances (PFASs) contamination has caused worldwide health concerns, and increased demand for effective elimination strategies. Herein, we developed a new indole derivative decorated with a hexadecane chain and a tertiary amine center (named di-indole hexadecyl ammonium, DIHA), which can form stable nanospheres (100-200 nm) in water via supramolecular assembly. As the DIHA nanospheres can induce electrostatic, hydrophobic and van der Waals interactions (all are long-ranged) that operative cooperatively, in addition to the nano-sized particles with large surface area, the DIHA nanocomposite exhibited extremely fast adsorption rates (in seconds), high adsorption capacities (0.764-0.857 g g-1) and selective adsorption for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), outperformed the previous reported high-end PFASs adsorbents. Simultaneously, the DIHA nanospheres can produce hydrated electron (eaq-) when subjected to UV irradiation, with the virtue of constraining the photo-generated eaq- and the adsorbed PFOA/PFOS molecules entirely inside the nanocomposite. As such, the UV/DIHA system exhibits extremely high degradation/defluorination efficiency for PFOA/PFOS, even under ambient conditions, especially with the advantages of low chemical dosage requirement (μM level) and robust performance against environmental variables. Therefore, it is a new attempt of using supramolecular approach to construct an indole-based nanocomposite, which can elegantly combine adsorption and degradation functions. The novel DIHA nanoemulsion system would shed light on the treatment of PFAS-contaminated wastewater.