Colorado School of Mines
Mr. Shilai Hao is currently a PhD student at Colorado School of Mines. He received his bachelor degree at Hefei University of Technology and his master degree in environmental engineering at Fudan University in China in 2016. He started to focus on destruction of PFAS in site investigation derived waste using hydrothermal technology in 2018.
Destruction and defluorination of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foam (AFFF) by hydrothermal treatme
The widespread use of aqueous film-forming foam (AFFF) for firefighting at multiple sites (e.g., military base) has led to groundwater and soil contamination by diverse classes of per- and polyfluoroalkyl substances (PFAS). Due to the environmental persistence, high bioaccumulation potential, and associated toxicities of PFAS, an effective treatment method leading to complete destruction and defluorination is imperative. This study examines the destruction of PFAS present in different AFFF matrices (stockpiles, diluted into lab water, groundwater) by hydrothermal treatment. A target and suspect screening analysis by high resolution mass spectrometry was conducted to track the decomposition of individual PFAS during treatment. The total fluorine mass balance result revealed that high temperature (350°C) and alkaline conditions (e.g., 1-5 M NaOH) promote destruction of PFAS within 90 minutes with near 100% defluorination being observed with different AFFF formulations (sulfonate based versus fluorotelomer based). This indicated potential for wide application of hydrothermal treatment, including on-site treatment of investigation-derived wastes, concentrated source zone materials, and chemical stockpiles of AFFF.
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