Patent ID: 6790274
Filing Date: 2004-09-14
Classification: B01J,B41F,C01G,C01P,C09C

Abstract:
A method for producing high-purity iron oxides, comprising the following steps, performed in succession or simultaneously:a) reaction of metallic iron, in the form of microspheroidal particles with an average diameter of no more than 250 microns or in the form of scraps or cuttings whose dimensions are such that their surface per kg of iron and per liter of reaction medium is greater than 0.01 m2, with an agitated aqueous solution of a carboxylic acid containing one or more carboxylic groups with a pKa of 0.5 to 6 at ambient temperature with reference to the first carboxyl, capable of decomposing by heating in air at temperatures between 200 and 350Â° C. into carbon dioxide and water, and of forming ferrous salts soluble under the aqueous solution under the reaction conditions, wherein the ratio between moles of carboxylic acid and g-atoms of iron is from 0.03 to 1.5, the water/iron weight ratio is from 1 to 20, the reaction temperature is between 0 and 100Â° C., and the microspheroidal particles are kept in suspension by agitation; b) forming an oxidation mother liquor by oxidation to ferric carboxylate of the ferrous carboxylate formed in a) with an oxidizing agent selected from oxygen, gaseous mixture containing oxygen, hydrogen peroxide, ozone, organic peroxides and hydroperoxides, used in excess of the stoichiometric value referred to the oxidation of the ferrous salt to ferric salt; and c) recovery of the iron oxide or iron oxides from the oxidation mother liquor.