Defluorination of Aqueous Perfluorooctanesulfonate by Activated Persulfate Oxidation

Abstract

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 K2S2O8 amounts on PFOS defluorination were investigated. The intermediate products during PFOS defluorination were detected by using LC/MS/MS. The results showed that the S2O8 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)/K2S2O8 > UV (ultraviolet)/K2S2O8 > Fe2+/K2S2O8 > US (ultrasound)/K2S2O8. Low pH was favorable for the PFOS defluorination with sulfate radicals. Increase in the amount of S2O8 2− had positive effect on PFOS defluorination. However, further increase in amounts of S2O8 2− caused insignificant improvement in PFOS defluorination due to elimination of sulfate radicals under high concentration of S2O8 2−. CF3(CF2)nCOOH (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.

Treatment of perfluoroalkyl acids by heat-activated persulfate under conditions representative of in situ chemical oxidation

“…This observation agrees with data reported in a recent study 27 but is at odds with the results of a study in which PFOS was transformed by heat-activated persulfate to produce shorter-chain PFCAs. 31 It is difficult to reconcile the results of the study in which PFOS degradation was reported for several reasons. First, the temperature at which persulfate activation was performed was not reported.…”

“…One research group employed S 2 O 8 2− concentrations of up to 84 mM and activation temperatures up to 60°C, but observed no PFOS defluorination, 27 whereas another research team reported up to 22.5% defluorination of PFOS using 18.5 mM of heat-activated S 2 O 8 2− . 31 …”

An overview on the advanced oxidation processes applied for the treatment of water pollutants defined in the recently launched Directive 2013/39/EU

“…Sulfate radical-based AOPs were also tested for PCB removal and the presence of chloride ion inhibited their transformation (Fang et al, 2012). Persulfate oxidation processes were applied to PFOA using UV-visible light (Hori et al, 2005(Hori et al, , 2008 and PFOS using an UV lamp (Yang et al, 2013). Persulfate produced a highly oxidative sulfate radical anion and PFOA (1.35 mM) was efficiently removed in 4 h (Hori et al, 2005).…”

Photo enhanced degradation of polyfluoroalkyl and perfluoroalkyl substances

“…Its comparative stability and pH independent activity, makes it reactive with a wide range of pollutants [ 67 ]. It also react with electron-rich moieties via various reaction routes such as hydrogen abstraction, electron exchange and direct oxygen transfer [ 68 ]. Hori et al.…”