Reduction of Nitrite and Nitrate on Nano-dimensioned FeS

Abstract

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.

Bio-Minerals Combined with Bacillus cereus for Enhancing the Nitrogen Removal Efficiency under Aerobic Conditions

“…Previous studies showed that natural pyrite-based autotrophic treatment removed over 95% nitrogen with less than 10% ammonium produced, which was similar to our removal rate, but production of sulfate was about 650 mg/L for 5 days compared to less than 30 mg/L in this study [18]. In relation to the aqueous pH condition, chemically synthesized FeS reduced nitrate and nitrite to ammonia/ammonium under high temperature above 70 • C [24]. These reactions induced reducing and alkaline conditions through Fe 2+ and S 2− donating electrons to NO 2…”

“…For instance, in a previous finding, the optimal pH for the ammonium removal was ca. pH 8 [24]. In this study, compared to changes in pH-Eh of BC in a single nitrate reactor appeared insignificant both, in which of BC in a mixed nitrogen reactor the solution Eh transformed from 332 mV to 97 mV for 4-day and ended to 107 mV for 5-day, whereas the solution pH did not change (Figure 2b).…”

Nitrogen Oxides in Early Earth's Atmosphere as Electron Acceptors for Life's Emergence

“…At such high temperatures, nitrate and nitrite would be reduced back to N 2 by iron minerals within the crust. There may also be some reduction of nitrate in the water cycling by moderate-temperature, serpentinizationdriven alkaline springs, though the product in this case is likely to be ammonia, thus merely adding to that entity at alkaline vents (Gordon et al, 2013). Surface temperatures and the lightning flash rates were calculated by using the Generic LMDZ 3D global climate model for early Earth.…”

Staging Life in an Early Warm ‘Seltzer’ Ocean

“…In the presence of hydrogen sulfide, nickel-iron alloys are only stable at alkaline pH and they are replaced by sulfides of varying Ni:Fe:S ratios at low pH. While the presence of sulfur decreases abundances of pure Fe-Ni alloys/metals, sulfides such as heazlewoodite (Ni3S2), pentlandite ([Fe,Ni]9S8), pyrite (FeS2) or mackinawite (FeS) can also facilitate the formation of prebiotically useful reduced carbon and nitrogen compounds (Brandes et al 1998;Schoonen and Xu 2001;Cody et al 2004;Singireddy et al 2012;Gordon et al 2013).…”