The nano-iron oxyhydroxides (α- and γ-FeOOH) were synthesized by using three ferrous and ferric salts (FeSO4, FeCl2, Fe(NO3)3) as iron precursors under alkaline conditions. Morphologies of nano-iron oxyhydroxides were characterized by employing X-ray
powder diffraction (XRD) and specific surface area (SSA) analysis respectively. The occurrence of needle-like shape of nano-goethite
and rod-like shape of nano-lepidocrocite were attributed to hydrolysis of Fe3+ cations and/or oxidization of Fe2+ at alkaline conditions in terms of XRD analysis. The N2-BET SSA and BJH (Barrett–Joyner–Halenda) pore size analysis showed that internal SSA of nano-lepidocrocite is higher than
that of nano-goethite, although they have similar N2-BET SSAs. The distribution of average pore size of nano-iron oxyhydroxides are higher than that of predominant pore size
due to formation of the heterogeneous nanoparticles under the experimental conditions. These nanoparticles possess the high
sorption capacity and the strong affinity for contaminants. Application of nano-iron oxyhydroxides in environmental engineering
plays an important role to remove a variety of contaminants, such as heavy-metal ions and organic pollutants.