METHOD FOR REMOVING SILICA IN AQUEOUS SOLUTION OF IRON CHLORIDE

PURPOSE:To remove silica in an aqueous solution of iron chloride readily, by adding a condensation auxiliary to a silica-containing aqueous solution of iron chloride acidified with hydrochloric acid, forming a polycondensate of silica and the condensation auxiliary, agglomerating it with a high polymer flocculant and separating. CONSTITUTION:A silica-containing aqueous solution 1 of iron chloride acidified with hydrochloric acid, such as hydrochloric acid washing waste liquor of steel plate, etc., is fed from a tank 2 to an agglomerating tank 4 and blended with a condensation auxiliary 6 (e.g., polyvinyl alcohol) to give a polycondensate of silica and the condensation auxiliary 6. Then, the aqueous solution of iron chloride containing the polycondensate together with a high polymer flocculant 8 (e.g., polyacrylamide) is fed to an aging tank 7, agglomeration of the polycondensate is aged, the agglomerated polycondensate is separated by a filter 10 to produce the aqueous solution of iron chloride with low silica content. The aqueous solution of iron chloride is preferably usable as a raw material for producing iron oxide for high-quality soft ferrite.