PRODUCTION OF GRANULAR GOETHITE FINE-PARTICLE POWDER AND PRODUCTION OF GRANULAR IRON OXIDE FINE-PARTICLE POWDER USING THE POWDER

PURPOSE:To obtain a granular goethite fine-particle powder excellent in particle size dispersion by allowing a ferrous salt soln. to react with a specified aq. alkali soln. and to obtain a granular iron oxide fine-praticle powder excellent in dispersibility by heating and dehydrating or heating and burning the powder. CONSTITUTION:An aq. ferrous salt soln. contg. 0.3-0.6mol/l Fe is allowed to react with an aq. alkali soln. free of ammonia, contg. 0.1-0.3mol of alkali hydroxide per mol of alkali carbonate and with the total amt. controlled to >=1.0 equivalent with respect to Fe in a nonoxidizing atmosphere to obtain a suspension contg. an iron-contg. precipitate. The suspension is kept at 50-65 deg.C and agitated for 30 to 360min, then 0.5-5.0 atomic % water-soluble silicate, expressed in terms of Si and based of Fe, is added, the silicate is oxidized at 50-60 deg.C by passing air through the suspension, and the precipitate is filtered off, washed and dried to obtain a goethite fine-particle powder. The powder is heated at 250-500 deg.C and dehydrated or further heated at 300-800 deg.C and burnt to obtain a granular iron oxide fine-particle powder.