Abstract

The use of nanomaterials has become a rapidly growing approach for advanced water treatment technologies, but the continued emergence of highly oxidation-resistant micropollutants, such as per- and polyfluoroalkyl substances (PFAS), calls for transformative strategies that move beyond recent oxidation-based remediation practices. Alternative reduction-based approaches utilizing aqueous electrons (eaq?, Eo = ?2.9 V)--one of the most reactive nucleophilic species--are emerging as a promising solution for efficient PFAS breakdown. Herein, we leverage nanoconfinement engineering to enable a new water treatment approach--plasmon-mediated advanced reduction processes (PARPs)--for efficient, chemical-free PFAS destruction at room temperature. We first present novel nanoreactor designs that engineer the 'nanoconfinement effect', i.e. unique aggregation-induced interparticle interactions that are inaccessible by typical unconfined, bulk-phase nanomaterials. We demonstrate that the precisely controlled nanoconfinement of plasmonic nanoparticles can generate highly reactive reducing species under UV irradiation, capable of breaking even the strong C-F bonds in PFAS. The nanoreactor we developed achieved 81.5% mineralization of perfluorooctanoic acid (PFOA) after 24 hours of UV irradiation in pure water at room temperature, compared to only 16.6% mineralization by UV photolysis. Further reaction monitoring under various conditions and multimodal NMR-guided investigation were conducted to elucidate PFAS degradation mechanisms and pathways. We further explored the potential of PARPs for the chemical-free remediation of nitrate, a prevalent oxyanion pollutant that is resistant to conventional oxidation-based treatments. Our findings highlight the transformative promise of nanoconfinement engineering to catalyze innovation in environmental nanotechnology and extend the frontier of advanced reduction processes for water treatment.

Bio- Haklae Lee is a PhD student in the Environmental Engineering & Science program and a member of the Gray Lab in the Department of Civil and Environmental Engineering at Northwestern University. He holds a B.S. and M.S. in Environmental Engineering from Pusan National University in South Korea. His work focuses on the design and engineering of nano-sized reactors for efficient and more sustainable remediation of emerging contaminants from wastewater. He uses mesoporous silica to spatially confine various metal nanoparticles within multi-layered nanoreactors, enabling unique features such as multifunctional compartments and nanoconfinement effects for previously unexplored environmental applications.