Figure 6.

Modeling PFOA degradation in UV/SO₃^–2 with estimated values of hydrated electron formation rate (R^e_aq–_f) and scavenging capacity (k′_S) in (A) No Particles, (B) GAC, (C) CNT, and (D) Lignin systems. The markers illustrate measured total (aqueous + sorbed) PFOA degradation. Black and red lines represent the lower (lowest generation R^e_aq–_f, highest scavenging k′_S) and upper (highest generation R^e_aq–_f, lowest scavenging k’_S) bounds on the kinetic models respectively based on the standard error measured for these parameters (R^e_aq–_f and k′_S) for each system (No Particles, GAC, CNT, and Lignin). Experiments were run at pH 10 with 20 mM initial SO₃^–2 and [PFOA]₀ = 12 μM (*for GAC, [PFOA]_0,aq = 0.1 μM), irradiated with 254 nm light at ambient temperature (20 °C). The bimolecular rate constant k_PFOA= 3.40 × 10⁷ M^–1 s^–1 is an average from reported literature values from Huang et al. (5.10 × 10⁷ M^–1 s^–1)⁷⁷ and Szajdzinska-Pietek et al. (1.70 × 10⁷ M^–1 s^–1).⁷⁸ Markers are the means of experimental duplicates, and error bars represent their standard error. *In the GAC system (B), measured PFOA concentrations are only from the aqueous phase ([PFOA]_0,aq = 0.1 μM), thus excluding adsorbed PFOA.