The Effects of Fluoridated Chain Lengths on Surface Chemistry

Perfluorinated alkyl substances, also known as PFAS, are water repellent and utilized for nonstick products, fast food containers, and even foams to put out forest fires. PFAS are also known as “forever chemicals”, owing to their resistivity to environmental degradation. Research has determined that PFAS are carcinogenic for humans and toxic to animals. Determining pathways to remove PFAS from the environment is essential since PFAS have been found in remote areas, such as Antarctica, that have no source to have PFAS. Understanding the surface properties and behavior of PFAS is essential to removing them from the environment. Here, we studied the effect of chain length of different PFAS on the surface pKa. Specifically, we investigated perflorooctanoic acid (PFOA) and perfluorodecanonic acid (PFDA) and their nonfluorinated versions, octanoic acid (OA) and decanonic acid (DA), utilizing surface tension measurements and bulk pH measurements. We determined that the fluorinated molecules have a lower surface pKa than the nonfluorinated versions. Moreover, as chain length increases, pKa also increases. This information provides details on the surface behavior of PFAS and may aid in the rational design of remediation technologies to remove PFAS from the environment