Linear perfluoroalkyl carboxylate reduction dynamics with solvated electrons from ferrocyanide and sulfite

The initial reduction dynamics of perfluoroalkyl substances (PFASs) by the hydrated electron, eaq-, is a topic of great interest and importance due to the pervasive environmental presence of PFAS in soil and waters and the need to remediate the contamination. Understanding how PFAS behaves in water, including the potential effect of aggregation on the apparent PFAS reduction rate constant (kPFAS) is, therefore, of paramount importance. In this publication we re-examine the proposition that submicellar aggregation decreases the apparent kPFAS for sodium perfluorocarboxylates of varying chain lengths (NaPFxA, x = number of carbons in the PFAS backbone, ranging from 4 to 8) using transient absorption spectroscopy. We compare the dynamics for eaq- quenching by NaPFxA in aqueous solutions of ferrocyanide, Fe(CN)64-, and sulfite, SO32-. The results demonstrate that the apparent rate constant depends on the choice of eaq- precursor. We demonstrate that the ionic strength of the solution and the counterion of the PFxA salt both affect the measured rate constant of PFAS reduction by eaq-. The results presented here help to better understand PFAS degradation by advanced reduction processes. Hydrated electron quenching by perfluoroalkyl carboxylates in ferrocyanide and sulfite is examined with nanosecond transient absorption spectroscopy. The results show distinct differences that are influenced by ionic strength and PFAS counterion.