Method of obtaining magnesium oxide from sea water and from solutions of magnesium salts

摘要

Magnesium oxide is obtained from solutions containing magnesium salts, for example, sea water, by first precipitating and removing as calcium carbonate and free carbon dioxide or carbon dioxide present as bicarbonate in the solution, and then precipitating the magnesium as hydroxide by the addition of a solution or slurry of an alkaline material, for example sodium hydroxide or carbonate, ammonia, milk of lime, or dolomite milk, an inorganic flocculating agent having been added before the separation of the precipitates, and adding a magnesium silicate slurry before the removal of the magnesium hydroxide precipitate in an amount to provide sufficient silica in the precipitate to lower the sintering temperature of the magnesium oxide derived therefrom. Suitable flocculating agents are aqueous solutions of aluminium sulphate or iron sulphate, or, preferably, a hydrochloric acid or sulphuric acid extract of metallurgical slag, especially of slags obtained in copper processing.