Effect of Property Changes of Iron Nanoparticles on Final Product Distribution in an Autotrophic Denitrification System from Groundwater

The iron particles extracted from biological and abiotic reactors were used to be characterized and compared with each other. TEM, SEM, XRD and XPS were utilized to observe and quantify the particle morphology and oxidized iron precipitates. Unlike the Fe
₃
O
₄
and Fe
₂
O
₃
coating of nanoscale zero-valent iron (NZVI) particles in the abiotic reactors, the major component of the coating of the activated particles from biological reactors was testified to be non-crystal FeOOH, which was the corrosive product in the reaction between iron and water. Furthermore, comparisons of different electron donors, including NZVI particles, corrosive particles and acid-washed Fe(0) powder, were carried out to evaluate the effect of this FeOOH coating. The results showed that application of corrosive particles could result in a lower nitrate reduction rate but a smaller proportion of ammonia relative to that in other two kinds of reactors. It indicated that the FeOOH coating might play an important role in the inhibition of ammonia generation.