(654g) Present Status and New Results for Pfas Destruction Chemistry | AIChE

(654g) Present Status and New Results for Pfas Destruction Chemistry


Westmoreland, P. - Presenter, North Carolina State University
Ram, H., North Carolina State University
Sadej, T. P., North Carolina State University
Murphy, C. C., North Carolina State University
A combustion/pyrolysis mechanism is presented for the destruction chemistry for perfluorooctanoic acid (PFOA), an important PFAS compound. Per- and Polyfluoroalkyl Substances (PFAS) have rapidly become a high national environmental priority. PFAS are durable chemicals whose valuable properties have led them to be widely used in cookware, outdoor wear, food wrappers, and firefighting; unfortunately, they bio-accumulate and can have adverse health effects. Furthermore, fluorocarbons have flame-suppressant characteristics as understood through our mechanistic modeling since 1994 [1,2], making incineration more difficult.

PFOA incineration chemistry occurs in the presence of hydrocarbon combustion. The first step in alkane combustion is abstraction of the weakest-held hydrogen to form an alkyl radical that unzips (beta-scissions) to generate olefin degradation products. In contrast, carbon-fluorine bonds are 20-40 kJ/mol stronger. Fluorine atoms are thus harder to abstract. The acidic H is abstracted more easily, forming an unstable Criegee radical that can rapidly eliminate CO2 to make perfluorohept-1-yl, which can unzip. Thermochemistry and kinetics are generated using computational quantum chemistry (G16 DFT and ONIOM), statistical mechanics, and transition-state theory; compared to literature where possible, including group-additivity estimates from the RMG/Arkane package; combined with the current NIST kinetics model; tested in plug-flow reactor calculations to establish consistency and dominant mechanistic pathways; compared and contrasted with the recent model-compound mechanism of Altarawneh et al. [3]; and further tested against data from a lab incinerator.


  1. P.R. Westmoreland, D. R. F. Burgess, Jr., W. Tsang, M. R. Zachariah, "Fluoromethane Chemistry and Its Role in Flame Suppression," Proceedings of the Combustion Institute 25, 1505-1611 (1994).
  2. C.D. Needham, P.R. Westmoreland, “Combustion and Flammability Chemistry for the Refrigerant HFO-1234yf (2,3,3,3-tetrafluroropropene)," Combustion and Flame 184, 176-185 (2017).
  3. M. Altarawneh, M.H. Almatarneh, B.Z. Dlugogorski, "Thermal decomposition of perfluorinated carboxylic acids: Kinetic model and theoretical requirements for PFAS incineration," Chemosphere 286, 131685 (2022).