The solubility of sodalite and cancrinite in synthetic spent Bayer liquor

The equilibrium SiO2 solubility of sodalite and cancrinite crystals in sodi um aluminate solutions containing low concentrations of aluminium (syntheti c spent Bayer liquor) has been determined over a range of temperatures (90- 220 degrees C) and as a function of solution NaOH and AI(OH)(3) concentrati on for cancrinite. The same SiO2 solubilities, within experimental error, w ere measured when equilibrium was approached from both above and below SiO2 solubility for spent Bayer liquors in contact with either sodalite or canc rinite crystals. The solubility of sodalite and cancrinite (expressed in te rms of SiO2 concentration) increased linearly with increasing temperature. The equilibrium SiO2 solubility of sodalite was higher than that of cancrin ite at all temperatures. The solubility of cancrinite increased with increa sing concentration of NaOH (3.87-5.42 M) and Al(OH)(3) (1.39-2.23 M) in sol ution. The SiO2 solubilities of four types of dimorphic sodalite/cancrinite mixed phase seed crystals synthesised from Bayer plant spent liquor and sy nthetic Na2CO3, Na2SO4 or NaNO3 rich NaOH solutions containing dissolved ka olinite were investigated, The solubility of the four types of mixed phase seed crystals was found to be substantially the same as the solubility for pure cancrinite. (C) 1999 Elsevier Science B.V. All rights reserved.