| 摘要 |
<p>Aluminium oxide is treated with alkali to give sodium aluminate solution, which is filtered through iron bed to reduce iron content. Specif., iron content is reduced to 0.004-0.018g Fe2O3 per litre. Iron bed is in form of grit or shot. Preferred filtration conditions are 5.79-149.35 cm/minute, contact time 0.44-7.7 minutes, depth of bed 30.5-122 cm. Iron bed regenerated by treatment with inorganic acid. During treatment, content of other oxides, particularly MnO, MgO, CuO, TiO2, CaO is also lowered. In example sodium aluminate solution containing 0.018-0.03g/litre Fe2O3 filtered through iron bed. Al2O3 reprecipitated contained 0.022% by weight Fe2O3 after treatment compared with 0.063% by weight before treatment.</p> |
