Nanosecond Transient Absorption Of Hydrated Electrons And Reduction Of Linear Perfluoroalkyl Acids And Sulfonates

We report the rate constants (k(q)) and activation energies (E-a) associated with the initial reduction of linear perfluoroalkyl carboxylates (PFxA, x = the number of carbons present in the surfactant) and perfluoroalkyl sulfonates (PFxS) by the hydrated electron (e(aq)(-)) as measured using temperature-dependent transient absorption spectroscopy. The reduction of PFxA and PFxS by e(aq)(-) displays a negligible dependence on the number of carbons present in the surfactant and occurs with an apparent k(q) on the order of 10(8) to 10(9) M-1 s(-1) with the k(q) corresponding to PFxA reduction being on average two times smaller than those for PFxS. There are no significant differences in the E-a associated with PFxA or PFxS reduction; the magnitude of E-a (similar to 11 kJ mol(-1)) is consistent with the reduction of PFxA and PFxS being a diffusion controlled process. These results are discussed within the framework of recent theoretical and experimental work on the degradation of PFxA and PFxS.