27 research outputs found
Defluorination of Aqueous Perfluorooctanesulfonate by Activated Persulfate Oxidation
<div><p>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<sub>2</sub>S<sub>2</sub>O<sub>8</sub> 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<sub>2</sub>O<sub>8</sub><sup>2−</sup> 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<sub>2</sub>S<sub>2</sub>O<sub>8</sub> > UV (ultraviolet)/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> > Fe<sup>2+</sup>/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> > US (ultrasound)/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>. Low pH was favorable for the PFOS defluorination with sulfate radicals. Increase in the amount of S<sub>2</sub>O<sub>8</sub><sup>2−</sup> had positive effect on PFOS defluorination. However, further increase in amounts of S<sub>2</sub>O<sub>8</sub><sup>2−</sup> caused insignificant improvement in PFOS defluorination due to elimination of sulfate radicals under high concentration of S<sub>2</sub>O<sub>8</sub><sup>2−</sup>. CF<sub>3</sub>(CF<sub>2</sub>)<sub>n</sub>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.</p></div
Schematic representation of reactor. (A) UV/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>. (B) US/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>.
<p>Schematic representation of reactor. (A) UV/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>. (B) US/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub>.</p
Possible defluorination pathways of PFOS in the activated K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation systems.
<p>Possible defluorination pathways of PFOS in the activated K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation systems.</p
Changes in the concentration of PFOS and intermediates through the PFOS defluorination in UV/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> system.
<p>Changes in the concentration of PFOS and intermediates through the PFOS defluorination in UV/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> system.</p
Mass spectrometry acquisition parameters of the intermediates. * Quantitative product ion.
<p>Mass spectrometry acquisition parameters of the intermediates. * Quantitative product ion.</p
Effect of K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> amounts on defluorination of PFOS in activated K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation systems.
<p>Effect of K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> amounts on defluorination of PFOS in activated K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation systems.</p
Time course of SO<sub>4</sub><sup>2−</sup> amounts in activated K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation systems.
<p>Time course of SO<sub>4</sub><sup>2−</sup> amounts in activated K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation systems.</p
The calculated pseudo-first-order constants and defluorination efficiency (%) of PFOS with 18.5 mM persulfate in activated K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation systems at different initial pH values.
<p>The calculated pseudo-first-order constants and defluorination efficiency (%) of PFOS with 18.5 mM persulfate in activated K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation systems at different initial pH values.</p
MRM spectra of assigned ionic compounds in the degraded solutions after 4h by UV/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation.
<p>MRM spectra of assigned ionic compounds in the degraded solutions after 4h by UV/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> oxidation.</p
Irradiation-time dependence of fluorine element mass balance during decomposition of PFOS in UV/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> systems.
<p>Irradiation-time dependence of fluorine element mass balance during decomposition of PFOS in UV/K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> systems.</p