A PROCESS FOR PREPARING ACICULAR ALPHA-FEOOH

摘要

Acicular alpha FeOOH is prepared by partially neutralising and then oxidising a ferrous salt soln. in the presence of phosphonic acid or one of its salts. The soln. is further oxidised whilst being neutralised with alkali. Feed crystals are formed at 50-100 deg.C using pyrophosphonic acid (salt) in an amt. 0.05-0.8 wt.% as P based on the amt. of FeOOH. The concn. of Fe(II) ions during seed crystal formation is at least 40 g/l and the seed crystals are grown 1.0-3.5 times greater than the total initial wt. at 50-100 deg.C. The particle size distribution is lower than that when the Fe (II) ions concn. is less than 40 g/l.