| The influence of initial pH on the formation of iron oxyhydroxide has been investigated. As the initial pH of reactant solution increased, β-FeOOH(pH=4.5), mixture of β-FeOOH and α-FeOOH(4 5$lt;pH$lt;5.5), mixture of α-FeOOH and Fe₃O₄(6.4$lt;pH$lt;12), Fe₃O₄(pH=12), α-FeOOH(pH$gt;13) were formed in order. At the end of reaction, the product was strongly acidic(pH$lt;3) when the initial pH was lower than 13. When the initial pH was higher than 13, the product was strongly basic(pH$gt;12). In order to synthesize only iron oxyhydroxide, we propose either precipitation after the oxidation of dissolved ion is completed perpectly or oxidation simultaneously with the precipitation. Oxidation of oxygen promotes not only the oxidation of ferrous ion but also dissolution and precipitation in the range of strong basicity. |
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