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Mechanochemical Destruction of PFAS
Citation:
Shields, E. AND A. Whitehill. Mechanochemical Destruction of PFAS. Noblis Engineering Community of Practice August 2021 Brown Bag Lunch, NA, August 25, 2021.
Impact/Purpose:
Per- and polyfluoroalkyl substances (PFAS) make up a unique and useful class of man-made molecules. PFAS' use in fire fighting foams and industrial processes has led to their widespread presence in soils. Unfortunately, many PFAS have been found to accumulate in humans and have been associated with several detrimental health effects. Here high energy ball-milling, or mechanochemical destruction (MCD), was tested to determine its efficacy for destroying PFAS in soil. This preliminary study shows the promise of ball-milling for soil remediation. This may be an important technique for soil remediation that could help local communities, regional partners, and the department of defense remediate PFAS contaminated soils.
Description:
The detrimental health effects associated with many per- and polyfluoroalkyl substances (PFAS) have raised concerns about PFAS contaminated soils and concentrated PFAS sources, like aqueous film forming foam (AFFF). Mechanochemical destruction (MCD), or high energy ball-milling, is a technique that has been used to remediate soil contaminated with other persistent organic pollutants. Preliminary studies of MCD to remediate AFFF contaminated soil and AFFF concentrate were conducted to determine if the MCD technology could be effective for destroying PFAS. According to the targeted PFAS analysis, MCD was effective at destroying the known PFAS in AFFF contaminated soil with over 99% destruction. The liquid AFFF concentrate was added to quartz sand and processed by a ball-mill, destroying over 99% of the known PFAS in the AFFF and about 98% of the extractable organic fluorine. Comparing the destruction profiles of PFAS and other organic pollutants, it was determined that the full-scale mechanochemical reactors should have about the same capacity for PFAS as for other pollutants, about 3 tons per hour. According to the power usage, this comes to about $25 per ton of soil in energy costs. More studies are needed to evaluate potential by-products not detected in the analyses and to ensure the capacity of the full-scale system. However, these preliminary studies show that MCD is a promising method to remediate PFAS contaminated soils.