The preparation of different crystalline degree lepidocrocite (γ-FeOOH) from air oxidation of Fe(OH)2 under irradiation by visible light in the presence of trace EDTA at different temperatures (14～20 ℃) were described. And the mechanism of the liquid phase transformations of γ-FeOOH was also studied. The experimental result showed that the crystalline degree of γ-FeOOH became poor with the increase of the temperature; the lower the crystallization degree of γ-FeOOH, the easier of the transformation to hematite (α-Fe2O3) by boiling reflux method; the goethite (α-FeOOH) was obtained from the liquid phase transformations of the high crystalline γ-FeOOH; the low crystalline γ-FeOOH could transform to spherical α-Fe2O3 rapidly under a near-neutral pH condition and in the presence of trace Fe(II).

Key words: lepidocrocite, liquid phase transformation, hematite, goethite