Reduction of Nitrite and Nitrate on Nano-dimensioned FeS
The reaction of nitrite (NO2 −) and nitrate (NO3 −) on nanometer-sized FeS particles was investigated in alkaline (initial pH = 10.3) solutions at reaction temperatures of 22, 70, and 120 °C using in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and fluorescence spectroscopy that allowed an analysis of adsorbate complexation on the FeS and reaction product in the aqueous phase, respectively. ATR-FTIR showed that NO was a surface-bound intermediate on FeS during its exposure to NO2 − at all three reaction temperatures. Ammonia/ammonium (NH3/NH4 +) product was also produced when FeS was exposed to NO2 − at the 70 °C and 120 °C reaction temperatures. Activation of NO3 − to form surface-bound NO was experimentally observed to occur at 120 °C on FeS, but not at the lower reaction temperatures. Furthermore, NH3/NH4 + product in the aqueous phase was only present during the reaction of FeS with NO3 − at the highest temperature used in this study.
KeywordsNitrite Nitrate Attenuated total reflection Fourier transform infrared Ammonium formation
The authors acknowledge support from the NASA Astrobiology Biogeocatalysis Center at Montana State University funded by the NASA Astrobiology Institute (NNA08CN85A).
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