Defluorination of Aqueous Perfluorooctanesulfonate by Activated Persulfate Oxidation

Activated persulfate oxidation technologies based on sulfate radicals were first evaluated for defluorination of aqueous perfluorooctanesulfonate (PFOS). The influences of catalytic method, time, pH and K(2)S(2)O(8) amounts on PFOS defluorination were investigated. The intermediate products during PFOS defluorination were detected by using LC/MS/MS. The results showed that the S(2)O(8) (2−) had weak effect on the defluorination of PFOS, while the PFOS was oxidatively defluorinated by sulfate radicals in water. The defluorination efficiency of PFOS under various treatment was followed the order: HT (hydrothermal)/K(2)S(2)O(8) > UV (ultraviolet)/K(2)S(2)O(8) > Fe(2+)/K(2)S(2)O(8) > US (ultrasound)/K(2)S(2)O(8). Low pH was favorable for the PFOS defluorination with sulfate radicals. Increase in the amount of S(2)O(8) (2−) had positive effect on PFOS defluorination. However, further increase in amounts of S(2)O(8) (2−) caused insignificant improvement in PFOS defluorination due to elimination of sulfate radicals under high concentration of S(2)O(8) (2−). CF(3)(CF(2))(n)COOH (n = 0–6) were detected as intermediates during PFOS defluorination. Sulfate radicals oxidation and hydrolysis were the main mechanisms involved in defluorination process of PFOS.