The production of γ-FeOOH from FeSO4 in the presence of EDTA

Abstract FeOOH crystals were grown from FeSO4 by the oxidation of a hydroxide suspension. These reactions were carried out with a solution concentration of EDTA in a range up to 0.125 M and at temperatures from 25 to 50°C. At 25°C with 0.0075 M EDTA, 100% γ-FeOOH was produced. At higher temperatures a greater concentration of EDTA was required to produce 100% γ-FeOOH, while lower concentrations produced a mixture of α-FeOOH and γ-FeOOH. By varying the time of addition of EDTA, it was determined that EDTA was active in a reaction window when approximately one-quarter of the Fe2+ had been oxidized to Fe3+. The addition of EDTA after this reaction window produced only α-FeOOH. No model compound similar to EDTA was found that could also produce γ-FeOOH from FeSO4.