Promotion effect of Fe2+ and Fe3O4 on nitrate reduction using zero-valent iron

The reductive efficiency of nitrate by zero-valent iron (Fe0) was increased under initial neutral conditions through addition of certain amount of Fe2+. Throughout the process, the NO3− and Fe2+ concentrations displayed a declining trend, but the general process was divided into three stages. It showed that Fe2+ could accelerate the corrosion of iron surface, accompanied by generating Fe3O4, and ionizing H+ which played an important role in buffering pH of the system. Fe3O4 behaved as a good conductor which favored the electron transfer on iron surface and accelerated the reductive denitrification rate of nitrate with Fe0 and Fe2+.

► Fe2+ promoted the nitrate reduction by ZVI under initial neutral conditions.
► Fe3O4 increased the reductive denitrification rate of nitrate with ZVI + Fe2+.
► Fe2+ accelerated the corrosion of iron surface, accompanied with generating Fe3O4.
► The nitrate reduction by ZVI + Fe2+ was continuously efficient at initial neutral pH.