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Figure 1. 

Defluorination of PFOA in UV, UV/PS, UV/ H₂O₂, UV/SO₃²⁻, UV/PS/FA, and UV/PS/MeOH systems. Reaction conditions: PFOA = 20 µM, PS = 5 mM, H₂O₂ = 5 mM, SO₃²⁻ = 10 mM, FA = 2 mM, MeOH = 2 mM, initial pH of 2.5, anaerobic environment for UV/SO₃²⁻, UV/PS/FA and UV/PS/MeOH systems, aerobic environment for the rest of the systems.

Figure 2. 

(a) EPR analysis of UV/PS/FA, UV/PS, and UV/FA systems. (b) Free radical quenching experiments. Reaction conditions: PFOA = 20 µM, initial pH of 2.5, anaerobic environment. (a) PS = 2 mM, FA = 15 mM, DMPO = 100 mM, reaction time = 5 min, anaerobic environment. (b) PS = 4 mM, FA = 2 mM, MV²⁺ = 10 mg/L, CCl₄ = 10 µM, Cr(VI) = 1 mM.

Figure 3. 

(a) Fluoride ion concentration. (b) Defluorination rate at different initial PFOA concentrations. Reaction conditions: PFOA = 20–200 µM, PS = 5 mM, FA = 2 mM, initial pH of 2.5, anaerobic environment.

Figure 4. 

Effect of (a) PS, and (b) FA concentration on PFOA defluorination by the UV/PS/FA system. Reaction conditions: PFOA = 20 µM, initial pH of 2.5, anaerobic environment. (a) PS = 1–5 mM, FA = 2 mM. (b) PS = 5 mM, FA = 2–20 mM.

Figure 5. 

Effect of initial pH on PFOA defluorination in (a) UV/PS/FA and (b) UV/PS/MeOH systems. Reaction conditions: PFOA = 20 µM, PS = 4 mM, initial pH = 2.5, 5, 7, 9, 12, anaerobic environment. (a) FA = 2 mM. (b) MeOH = 2 mM.

Figure 6. 

Effect of NO₃⁻, NO₂⁻, SO₄²⁻, and HCO₃⁻ on PFOA defluorination. Reaction conditions: PFOA = 20 µM, PS = 4 mM, FA = 2 mM, NO₃⁻, NO₂⁻, SO₄²⁻, HCO₃⁻ = 10 mM, unadjusted pH, anaerobic environment.

Figure 7. 

(a) Effect of humic acid on PFOA defluorination. (b) Effect of xanthohumic acid on PFOA degradation. Reaction conditions: PFOA = 20 µM, PS = 4 mM, FA = 2 mM, initial pH of 2.5, anaerobic environment. (a) HA = 10–100 ppm, (b) XA = 10–100 ppm.