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.