Anion affinities, γ X -, for the aerial interface of aqueous (Br -+ NO 3 -+ I -+ SCN -+ BF 4 -+ ClO 4 -) solutions are determined by electrospray ionization mass spectrometry. The composition of the ions ejected from the surface of fissioning nanodroplets shows that γ X -increase (decrease) exponentially with anionic radii, a X -(dehydration free energies, d G X -), and selectively respond to the presence of surfactants. BF 4 -, the least hydrated and polarizable anion of the set, has one of the largest γ X -values. Non-ionic surfactants decrease γ I -and γ SCN -but increase γ BF 4 -. Cetyltrimethyl ammonium markedly enhances the γ X -of smaller anions. A similar but weaker effect is observed upon lowering the pH of the bulk solutions from 8.2 to 3.0. Dodecyl sulfate has a negligible effect on γ X -. Considering that (i) universal many-body electrodynamic interactions will progressively stabilize the interfacial layer as its dielectric permittivity falls relative to that of the bulk solution and (ii) water permittivity is uniformly depressed by increasing concentrations of these anions, we infer that the observed Hofmeister correlation, ln γ X -∝ -d G X -, is consistent with the optimal depression of the permittivity of the drier interfacial layer by the least hydrated ions. Interfacial ion-ion interactions can significantly influence γ X -in environmental aqueous media.

Fluorochemicals (FCs) are oxidatively recalcitrant, environmentally persistent, and resistant to most conventional treatment technologies. FCs have unique physiochemical properties derived from fluorine which is the most electronegative element. Perfluorooctanesulfonate (PFOS), and perfluorooctanoate (PFOA) have been detected globally in the hydrosphere, atmosphere and biosphere. Reducing treatment technologies such as reverses osmosis, nano-filtration and activated carbon can remove FCs from water. However, incineration of the concentrated waste is required for complete FC destruction. Recently, a number of alternative technologies for FC decomposition have been reported. The FC degradation technologies span a wide range of chemical processes including direct photolysis, photocatalytic oxidation, photochemical oxidation, photochemical reduction, thermally-induced reduction, and sonochemical pyrolysis. This paper reviews these FC degradation technologies in terms of kinetics, mechanism, energetic cost, and applicability. The optimal PFOS/PFOA treatment method is strongly dependent upon the FC concentration, background organic and metal concentration, and available degradation time.

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Perfluorinated chemicals (PFCs) are distributed throughout the environment. In the case of perfluorinated alkyl carboxylates and sulfonates, they can be classified as persistent organic pollutants since they are resistant to environmentally relevant reduction, oxidation, and hydrolytic processes. With this in mind, we report on the reductive defluorination of perfluorobutanoate, PFBA (C(3)F(7)CO(2)(-)), perfluorohexanoate, PFHA (C(5)F(11)CO(2)(-)), perfluorooctanoate, PFOA (C(7)F(15)CO(2)(-)), perfluorobutane sulfonate, PFBS (C(4)F(9)SO(3)(-)), perfluorohexane sulfonate, PFHS (C(6)F(13)SO(3)(-)), and perfluorooctane sulfonate, PFOS (C(8)F(17)SO(3)(-)) by aquated electrons, e(aq)(-), that are generated from the UV photolysis (lambda = 254 nm) of iodide. The ionic headgroup (-SO(3)(-) vs -CO(2)(-)) has a significant effect on the reduction kinetics and extent of defluorination (F index = -[F(-)](produced)/[PFC](degraded)). Perfluoroalkylsulfonate reduction kinetics and the F index increase linearly with increasing chain length. In contrast, perfluoroalkylcarboxylate chain length appears to have a negligible effect on the observed kinetics and the F index. H/F ratios in the gaseous fluoro-organic products are consistent with measured F indexes. Incomplete defluorination of the gaseous products suggests a reductive cleavage of the ionic headgroup occurs before complete defluorination. Detailed mechanisms involving initiation by aquated electrons are proposed.

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