In this paper, high specific surface area zerovalent Fe(0) nanoparticles with unusual morphology and high reductive activity were prepared using a chemical reductive reaction of iron chloride hydrate with sodium borohydride in an aqueous solution of ionic liquids (ILs). The ionic liquids, [C(4)mim]X (X=Cl-, Br-, BF4-, PF6-) and [C(n)mim][BF4] (n=4, 6, 8), were used for this purpose. Transmission electron microscopy, X-ray diffraction, and Brunauer-Emmett-Teller surface area measurements were used to characterize the morphology, structure, and physical properties of the as-prepared Fe(0). The results suggest that the nucleation and growth of the Fe(0) were governed by an IL-controlled reductive reaction mechanism. The effects of ionic liquids (cations, anions, and concentration) on the morphology of the Fe(0) were examined. It was shown that anions of the ILs played a key role in the morphology and size of Fe(0), and the nanoparticle size of the Fe(0) prepared in the presence of different ionic liquids follows the trend: [C(4)mim]Cl > [C(4)mim]Br> [C(4)mim][BF4] > [C(4)mim][PF6] and [C(4)mim][BF4] > [C(6)mim][BF4] > [C(8)mim][BF4]. The reductive activity of the iron nanoparticles was studied by the denitrification experiment of sodium nitrite. The removal rate of nitrite by the IL-capped Fe(0) was found to be much faster than that by the noricapped Fe(0). This indicates that the IL-capped Fe(0) particles are better candidates for the reductive degradation. The high reductive activity of the Fe(0) nanoparticles was attributed to their high surface area and more active sites.