Reductive transformation of perfluorooctanesulfonate by nNiFe0-Activated carbon

[Display omitted] •nNiFeo-AC particles transformed both L- and Br-PFOS isomers.•PFOS transformation highest at 50 °C at 94 % (40–60 °C investigated).•Fluoride and sulfite generation accounted for nearly all the PFOS decomposed.•Several organic transformation products were identified in particle extracts. Degradation of linear (L) and branched (Br) perfluorooctanesulfonate (PFOS) using nNiFe° particles supported on activated carbon (AC) and heat is demonstrated for the first time and with several lines of evidence. At 60 °C, PFOS degradation plateaued at 50 ± 6%, while at 50 °C, 94 ± 4.1 % PFOS transformed. The accelerated iron corrosion at the higher temperature is attributed to the lower PFOS transformation at 60 °C. However, at both temperatures, ≥ 97 % of the PFOS transformed was accounted for by the moles of fluoride generated. At 60 °C, PFOS degradation rates were estimated at 0.028 ± 0.003 h−1 and fluoride and sulfite generation rates of 0.70 ± 0.165 h−1 and 0.62 ± 0.157 h−1, respectively, with no differences between L-PFOS and total Br-PFOS. Using time-of-flight mass spectrometry, some organic products were identified in the particle extracts from the 60 °C reaction. Products included single-bonded C8 polyfluoroalkyl sulfonates (F16 to F7) and alkyl acids (PFCAs, C4-C8) and one perfluorinated C8 desulfonated product supporting both defluorination and desulfonation pathways. Most of the organic products were gone after the first 25 h. High PFOS mineralization using nNiFe°-AC technology warrants further investigation for its use in permeable reactive barriers.