| 摘要 |
PURPOSE:To obtain alpha-ferric hydroxide oxide having excellent acicular form and free from coagulation, by oxidizing a mixed aqueous solution of a ferrous salt and an alkali hydroxide in the presence of a Ca salt, adjusting the concentration of the reaction product, and further oxidizing the product to complete the oxidization reaction. CONSTITUTION:A calcium salt is added to an aqueous solution of a ferrous salt in an amount of 0.5-2mol% based on iron, prior to the supply of oxidizing gas. The obtained aqueous solution of ferrous chloride is added at <=25 deg.C to an aqueous solution of an alkali hydroxide in an amount to give an iron concentration of 0.03-0.3mol/l. The amount of the alkali hydroxide is 6-16mol per 1mol of iron. An oxidizing gas is supplied to the mixture to an extent to give an oxidization ratio of <=50%, the temperature of the system is raised to 40- 80 deg.C in an inert gas atmosphere, and the alkali hydroxide concentration is adjusted to 12-30mol per 1mol of iron. The conditioned aqueous solution is supplied again with the oxidizing gas and the oxidization reaction is completed to obtain the objective alpha-ferric hydroxide oxide. |
