Abstract:Surface tension of sodium aluminate solution and the contact angle between Al(OH)₃ particles and aluminate solution were measured, then the dependence of Al(OH)₃ solubility on its particle size was calculated and thus the variation of the critical nucleus sizes was determined based on the Ostwald ripening formula. The results show that the Al(OH)₃ solubility in sodium aluminate solution decreases with the increment of particle size, and the critical nucleus sizes increase with the rise of alkali concentration, caustic ratio and precipitation temperature. The results also imply that the presence of small particles in seeded precipitation system is an important factor to limit the depth of precipitation.

Key words: Bayer liquor; Al(OH)₃; interfacial property; solubility; critical nucleus size