| 摘要 |
High-purity alumina is extracted from alimina-containing ores as follows. The ores are kneaded with 70-95% H2SO4 soln. and the mixture is baked at 100-200≦̸C. Water-insoluble SiO2 in the mixture is separated through filtration; Al scrap is introduced to thd filtrate to reduce Fe+3 ions to Fe+2 ions. (NH4)2SO4 is added to the soln. to crystallize alum, which is hydrolyzed to produce Al2O33H2O under NH3 atmosphere, Fe in the soln. is changed to Fe2o3 XB2o under and air atmosphere; effluent (NH4)SO4 soln. is then concentrated and recirculated to the crystallization step. By-products, such as Na2SO4 or gypsum, are obtained and the separated NH3 is re cycled.
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