Red-mud is the residue from the Bayer process, in which the iron minerals should be removed before red-mud is used to produce refractory materials. The iron minerals in red-mud were extracted by oxalic acid solution. The content of Fe （calculated in Fe203） in red-mud was reduced from 17.6% to less than 1% after being treated by 1 mol/L oxalic acid solution at 75 ℃ for 2 h. The Fe（Ⅲ） oxalate solution obtained was then irradiated by UV light, resulting in the precipitation of Fe（Ⅱ） oxalate. Under UV photocatalysis, more than 90% of Fe（Ⅲ） oxalate in the extracted solution was transformed into the precipitation of Fe（Ⅱ） oxalate crystallite （fl-FeC2O4·2H2O）. The filtrate from the Fe（Ⅱ） oxalate precipitate filtration could be reused in the next cycle. The mechanism ofUV photocatalysis precipitation was also discussed.
