New SRP Publication: Vapor Pressure of Nine Perfluoroalkyl Substances (PFASs) Determined Using the Knudsen Effusion Method

May 1, 2020

In understanding how contaminants move around in the environment and for predicting where they will ultimately settle, it is important to have a clear understanding of their chemical and physical properties. The measurement of such properties has been a focus of the Suuberg lab for a number of years. Beginning with their work on vapor pressures and mixture thermodynamics of polycyclic aromatic compounds (PACs), they have looked aat materials ranging from coal tars to biomass tars to oxygenated polycyclics to flame retardants such as polybrominated diphenyl ethers (PBDEs). Now, they have turned their attention to per- and polyfluorinated alkyl substances (PFAS). Because the PFAS are often viewed more as a groundwater or soil pollution problem, they have not been very actively studied as vapor phase pollutants. But as very recent work on fugitive emissions from incinerators has suggested, they can be volatilized, and the vapor pressures of some of the more familiar PFAS compounds place them squarely in the class of semi-volatile organic compounds (SVOCs). In their recent publication, Mengke Zhang and co-authors from the Suuberg lab have measured the vapor pressures of nine different PFAS compounds at near ambient conditions. Many of these measurements were the first to be made under these environmentally-relevant conditions, and in some cases, the first to be made at all on some of the compounds.  The measurements (now in the online edition of the Journal of Chemical and Engineering Data) also led to more general conclusions regarding the contribution to certain properties of each CF2 group in the fluoroalkyl chain, as well as pointing out the complexity in characterizing the melting phase transitions of these compounds. It is hoped that such basic thermodynamic property data will provide a solid basis for those faced with predicting other properties under different conditions of relevance in different environmental scenarios. 

This new publication can be found here.