A novel control strategy for N2O formation by adjusting Eh in nitrite/Fe(II–III) carbonate green rust system

Abstract

In order to improve the generation amount of nitrous oxide (N2O), the process of nitrite (NO2−) reduction was studied by Fe(II–III) carbonate green rust (GR(CO32−)). The results indicated that 97.1% NO2− was degraded, and over 71.3% N2O was achieved by the oxidation of GR(CO32−) to Fe3O4; 14.1% N2, 4.7% NH4+ and 3.0% NO3− were also formed in the denitrification process; the removal efficiency for total nitrogen (TN) was 89.6%; the optimal reaction condition was NO2− 10.71mM, pH 9.5 and an initial Eh (the maximum value of Eh reached at the beginning of the process) of −473mV. The generation of different reduction products was dependent on the initial Eh of the reaction system. Based on the adjustment of initial Eh, the formation order of reduction products was as follows: N2O, N2 and NH4+. Additionally, compared with initial nitrite concentration, pH played a decisive role in the initial Eh of the NO2−/GR(CO32−) system. The high amount of N2O generated by the adjustment of initial Eh provides new insight into the NO2−/GR(CO32−) system.