Solubility of Sodium Aluminosilicates in Synthetic Bayer Liquor

The solubility of two major sodium aluminosilicate Bayer refinery scale phases, sodalite and cancrinite, has been measured in sodium aluminate liquor as a function of time, sodium carbonate concentration, initial seeding phase, and temperature. Solubility is assessed by the measurement of SiO 2 concentration in solution for at least 13 days. At both 90 °C and 160 °C, sodalite seed partially transforms to cancrinite over 13 days. As this transformation is partial, the use of the term “equilibrium solubility” is not justified. The kinetics of this process are faster at the higher temperature; hence, the proportion of cancrinite in the final crystalline products is greater at 160 °C. As expected, the more thermodynamically stable product, cancrinite, was found to be less soluble. Hence, SiO 2 solubility in sodalite-seeded solutions was not greater at 160 °C than at 90 °C. In cancrinite seeded solutions, where no further phase transformation occurs, the equilibrium SiO 2 concentration in solution increases with increasing temperature. Increasing Na 2 CO 3 concentration does not appear to affect the sodalite-to-cancrinite transformation kinetics. In all sodalite or cancrinite-seeded solutions, SiO 2 solubility decreases with increasing Na 2 CO 3 concentration.