Per- and polyfluoroalkyl substances (PFAS) are a class of ubiquitous chemicals found in innumerable industrial and consumer products. They are extremely persistent and have been detected in diverse environmental compartments. Sampling and quantifying PFAS are required before remediation of the contaminated sites can begin. Given their vast variety and structural diversity, comprehensive characterization and quantification of PFAS represent a considerable analytical challenge. Total organic fluorine (TOF) may be a representative of total PFAS and can be measured rapidly, but inorganic fluorine (i.e., fluoride, F–) interferes with the measurement. Concentrating PFAS as extractable organic fluorine (EOF) or adsorbable organic fluorine (AOF) results in removal of F– but recovery of some PFAS is low and others unknown. We propose to remove F– from aqueous suspension via adsorption rather than selectively adsorb PFAS. Once F– is removed, the liquid sample is directly combusted and the resulting F– represents TOF. The advantage is that there is no need to conduct ion chromatography (IC) analysis on the raw sample or to perform solid phase extraction, although the disadvantage is the limit of detection that is far higher than AOF and EOF pre-concentrating methods. Multi-valent metal oxides (MOx) are among the plausible candidates. Tin (IV) dioxide (SnO2) and hafnium dioxide (HfO2) were shown to adsorb F– in early studies, yet no report on their adsorption of PFAS is available based on our knowledge. Preliminary results suggested minimal adsorption of perfluorooctanoic acid (PFOA) under certain conditions. Other perfluorocarboxylic acids (PFCAs) with chain lengths ranging from C2 to C10 and perfluorooctane sulfonic acid (PFOS, C8) were further used to study their adsorption by MOx. Influence of some key parameters such as the adsorbent dose and pH was evaluated. Their separation efficiency was compared to the most conventional adsorbent alumina (Al2O3). The outcome of this study provides an important set of information on the robust and cost-effective quantification of PFAS.

Adsorptive separation of fluoride and per- and polyfluoroalkyl substances (PFAS) for direct total organic fluorine (TOF) measurement

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.