Abstract: Zero-valent iron(Fe0) was widely used for in-situ and ex-situ remediation of nitrate in groundwater, however, it remained to
be studied that how existing of Fe2+ worked in the reduction of nitrate by Fe0 which was covered by iron oxides. In this study, batch
experiments were conducted to investigate the effect of Fe2 + on NO3- reduction using 100 mesh untreated zero-valent iron (Fe0) as
reductant. The results showed that, Fe2+ could significantly enhance the removal rate and removal efficiency of NO3- in the presence of
Fe0, and the removal efficiency increased with elevated Fe2+ concentration; but the reaction experienced an initial stage of low rate due
to the existence of oxide film on the Fe0 surface. Fe2+ could directly revolved in the reaction and transformed Fe2O3 which covers the Fe0
to Fe3O4, which accelerates the transfer of electrons from Fe0 to NO3- and promote the reduction of nitrate. What’s more, the removal
efficiency of NO3- by Fe0 will be further improved while adding Fe3O4 into the reaction system, however, with the absence of Fe2+ , the
adding of Fe3O4 only will not influence the reduction efficiency by Fe0.

Key words: zero-valent iron, Fe2+, Fe3O4, nitrate reduction, groundwater