Elemental Sulfur as Electron Acceptor for Iron Recycling in Feammox Incubations

Abstract

The Feammox (iron reduction coupled to ammonium oxidation) reaction facilitated by Acidimicrobium sp. A6 can be used to defluorinate per- and polyfluoroalkyl substances (PFAS). The reaction is limited in part by the availability of the oxidizing agent, Fe(III), which is reduced to Fe(II) as the reaction proceeds. A theorized pathway of recycling the produced Fe(II) into Fe(III) through the addition of elemental sulfur (S0 ) was tested in Feammox incubations by varying S0 concentrations in incubations with and without PFOA. While the presence of S0 appeared to correlate with an increase in NH4 + removal and PFOA defluorination, differences between 400% Sulfur, 100%, and No sulfur generally lacked statistical significance due to varying bacterial activity. Furthermore, the apparent production of sulfate points to S0 oxidation rather than the expected reduction, making it seem unlikely that iron recycling was achieved in this case.