Iron impurities are removed from red mud by activating the material in batch or continuous reactors at 150-800 deg. C and 0.1-100 bar pressure with pure hydrogen or hydrogen contg. gas or with ammonia contg. gas in reducing conditions in the presence of more than one type of activator, and adding as promotor for the elimination of iron 0.1-30.0 wt.% sulphur contg. synergistic inorganic or organic sulphur cpds.. The mixt., is treated with carbon-monoxide or carbon-monoxide contg. gas at 50-300 deg. C and 25-300 bar pressure and the evolving iron-penta-carbonyl is continuously removed. - The resulting bauxite is suitable for the prodn. of alumina.
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