| 摘要 |
PURPOSE:The hydrolysis of a ferric salt with alkali is effected in 2-steps, as aging is effected, to give goethite of desired particle sizes with high needle shape, narrow particle size distribution and high dispersibility. CONSTITUTION:A ferric salt other than ferric sulfate such as ferric nitrate nonahydrate is combined with an alkali such as sodium hydroxide at a molar ratio OH/Fe of 0.5-2.9 to form a slurry of partially hydrolyzate of the ferric salt. Then, the first-step aging is effected in the presence or absence of a zinc salt such as zinc chloride in amount of 1-10mol% based on the ferric salt for hours selected from 1 to 72 hours to give goethite particles of 0.10-0.20 micrometer long axis and 6-12 average axis ratio. The alkali is further added so that the OH/Fe molar ratio becomes more than 3.5 and, when the first step is conducted in the absence of a zinc salt, the above-stated amount of a zinc salt is added, to effect the second aging at 50-200 deg.C and a pH of 13.0 (at 20 deg.C). |
