Shilai Hao
PhD Graduated Student
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.
Application of Hydrothermal Alkaline Treatment (HALT) for Destruction of PFASs in Contaminated Groundwater and Soil
The presentation will report on our team’s application of a new hydrothermal alkaline treatment technology (HALT-PFAS) to treat two groundwaters and three soils from AFFF-impacted sites, tracking the fate of individual PFAS using high-resolution mass spectrometry (HRMS). Targeted and suspect screening analysis protocols identified many PFASs, including perfluoroalkyl carboxylic and sulfonic acids. All detected PFASs were degraded to non-detectable levels within 90 min when treated with 5 M NaOH under 350 °C. Among the detected PFASs, perfluoroalkyl sulfonic acids, particularly short-chain structures, were most recalcitrant and required the most severe reaction conditions to bring about degradation. Rates of PFAS destruction in site groundwater was found to be similar to laboratory water solutions, but reactions in soil were retarded due to base-neutralizing properties of the soil. Thus, soil treatment applications need to be designed to include this consideration to ensure treatment goals are met.