Insights into perfluorooctane sulfonate photodegradation in a catalyst-free aqueous solution

Abstract

Photodegradation in the absence of externally added chemicals could be an attractive solution for the removal of perfluorooctane sulfonate (PFOS) in aqueous environment, but the low decomposition rate presents a severe challenge and the underlying mechanisms are unclear. In this study, we demonstrated that PFOS could be effectively degraded in a catalyst-free aqueous solution via a reduction route. Under appropriate pH and temperature conditions, a rapid PFOS photodegradation, with a pseudo-first-order decomposition rate constant of 0.91 h−1, was achieved. In addition, hydrated electrons were considered to be the major photo-generated reductive species responsible for PFOS photodegradation in this system. Its production and reduction ability could be significantly affected by the environmental conditions such as pH, temperature and presence of oxidative species. This study gives insights into the PFOS photodegradation process and may provide useful information for developing catalyst-free photodegradation systems for decomposing PFOS and other persistent water contaminants.

Enhanced photoreductive degradation of perfluorooctanesulfonate by UV irradiation in the presence of ethylenediaminetetraacetic acid

“…The decomposition percentage was highest under an initial pH of 10.0, while lowest observed rate was at an initial pH of 4.0. These results show that the e aq --mediated decomposition of PFOS is more effective under alkaline conditions, which is a result that is consistent with previous report[17,18]. The defluorination percentage after 10 h also increased with an increase in pH as follows for pH of 4, 6, 7, 9 and 10 after 10 h of irradiation were 27.77%, 29.99%, 41.38%, 46.38% and 51.19%, respectively.…”

“…Electron beam and gamma-ray radiation has been used to decompose PFOS, considering the fixed cost such as high equipment cost, interest and depreciation [16], the cost is too high for an economical engineering treatment method. A catalyst-free PFOS photodecomposition method that requires high temperatures (e.g., 100 o C) and alkaline conditions (pH =11.8) has been reported to exhibit great performance in PFOS decomposition [17]. But high temperature and strong alkaline conditions would be bottleneck of the application of this process.…”

Directional electron transfer mechanisms with graphene quantum dots as the electron donor for photodecomposition of perfluorooctane sulfonate

“…To elucidate the effect of GQDs in the reaction, it was of vital importance to investigate the physical, optical and electronic properties of the prepared GQDs. Characterization of the as-synthesized SiC/GQDs nanocomposites by high-resolution transmission electron microscopy 12 (HRTEM) showed the highly uniform dispersion of GQDs (1.8 to 3.6 nm in diameter) embedded onto the SiC nanoparticles ( Figure S3). UV-vis absorption and fluorescence emission-excitation spectrum are shown in Figure 4.…”

“…Persistence of perfluoroalkyl compounds (PFCs) is mainly caused by their intrinsic bond strengths (C-F, 531.5 kJ mol -1 ) [10]. Compared with perfluorooctanoic acid (PFOA), PFOS is even more difficult to degrade for the presence of strong electron-withdrawing headgroupsulfonate group [11,12]. PFOS is inert to many methods that can efficiently decompose PFOA, such as electrochemical oxidation with Ti/SnO 2 -Sb/PbO 2 anode, photocatalysis with commercial nano-TiO 2 (Degussa P25), and photolysis under UVC light.…”

Monthly Variations in Perfluorinated Compound Concentrations in Groundwater

“…By creating a lower, combined health advisory level, water systems previously below the bounds of the 2009 advisory may no longer meet the more stringent guidance. Traditional removal techniques for water contaminants, such as flocculation, sand filtration, or photodegradation without additional chemicals are ineffective against PFAS [ 23 , 24 ]. To combat high levels of long chain PFAS, water systems install activated carbon filters or reverse osmosis systems, both of which are costly [ 25 ].…”