Equilibrium concentration of lithium ion in sodium aluminate solution.

Excess lithium in alumina is significantly bad for aluminum reduction. In this study, the concentration variation of lithium ion in sodium aluminate solution with addition of synthetic lithium aluminate was investigated. Elevating temperature, increasing caustic soda concentration, reducing alumina concentration or raising molar ratio α _k improved equilibrium concentration of lithium ion in sodium aluminate solution. Agitation speed had a minimal effect on lithium ion concentration. Over 0.65 g/L lithium ion equilibrium concentration was observed in digestion process, whereas 35 mg/L lithium ion concentration remained in solution after precipitation time of 9 h. Moreover, equilibrium concentration decreased sharply from digestion of boehmite or diaspore to seed precipitation, about 95% lithium was precipitated into red mud (bauxite residue) and aluminum hydroxide. This study provides a valuable perspective in removal or extraction of lithium from sodium aluminate solution in alumina refineries. [ABSTRACT FROM AUTHOR]