A KINETIC MODEL FOR CRYSTALLIZING ALUMINUM HYDROXIDE FROM ALUMINATE SOLUTIONS WITH VARYING CARBONATE COMPOUNDS

摘要

When separating aluminum hydroxide from aluminate solutions by their carbonization it is impossible to produce alumina with specific physico-chemical properties without knowing the basic kinetic rules governing formation of the solid phase. This work looked into the effect of soda on the crystallization rate of aluminum hydroxide from aluminate solutions, containing 100 g/l Na2O_(tot) and from 100 to 20 g/l Na_2O_c. The tests were conducted in 1.5-liter laboratory crystallizers using mechanical mixing. 160 g/l industrial aluminum hydroxide was used as theseed crystal. During the crystallization process (12-24 hours), without stopping the mixers, samples of 40-50 cm~3 were selected by means of vacuum samplers. The granulometric composition of the deposit was determined and the aqueous phase was analyzed for aluminum and sodium oxides contents.