METHOD OF MAKING IMPROVED ALUMINA

摘要

A process is provided which allows control of the impurity level of Bayer process streams with simultaneous generation of an environmentally acceptable effluent and recovery of valuable dissolved aluminum and sodium values. The process involves carbonation of a blow-down stream at 40 DEG -100 DEG C to produce sodium dawsonite [NaAl(OH)2CO2] and an effluent essentially free of dissolved alumina and significantly depleted in dissolved sodium. The sodium dawsonite can be used as such or returned to the Bayer process after thermal decomposition to sodium aluminate. The effluent can be directly discharged into natural receiving bodies without further treatment.