Phase Diagrams for the Ternary Na₂O−Al₂O₃−H₂O System at (150 and 180) °C

Abstract

The full alkali concentration range phase diagrams of the Na2O−Al2O3−H2O system were constructed at (150 and 180) °C. The compositions of the clear liquids and wet solid phases were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the results show that, as the Na2O concentration increases, the Al2O3 solubility initially increases monotonically, to maximum values of 100 w (mass fraction) = 33.58 and 35.86 at (150 and 180) °C, respectively, and then decreases. At both temperatures, the solid phases were determined to be Al2O3·H2O, Na2O·Al2O3·2.5H2O, Na2O·Al2O3, and NaOH by X-ray diffraction coupled with Schreinemaker’s method. The phase diagrams indicate that, as the temperature increases, the Na2O·Al2O3·2.5H2O phase region shrinks, while that of the Na2O·Al2O3 phase expands.

Phase Equilibrium in the Ternary System K2O–Al2O3–H2O at 323.15, 333.15, 343.15, and 353.15 K

“…13 According to the research, it was found that the equilibrium solid phases of this ternary system diversified with temperature and concentration. At low concentrations, the equilibrium solid was determined to be Al 2 O 3 •3H 2 O at 368.15 and 383.15 K, 14 prior to becoming Al 2 O 3 •H 2 O at 403.15, 15 423.15, and 453.15 K. 16 Meanwhile, with an increase in the Na In general, it needs a broad temperature operating range (from 323.15 to 353.15 K) for separating the soluble alumina from the alkaline leaching solution, since the flowsheet could include cooling crystallization. Nevertheless, the existing phase equilibrium data of the corresponding system at this temperature range are deficient.…”

“…According to the research, it was found that the equilibrium solid phases of this ternary system diversified with temperature and concentration. At low concentrations, the equilibrium solid was determined to be Al 2 O 3 ·3H 2 O at 368.15 and 383.15 K, prior to becoming Al 2 O 3 ·H 2 O at 403.15, 423.15, and 453.15 K . Meanwhile, with an increase in the Na 2 O concentration at 383.15 K, the equilibrium solid transforms from Na 2 O·Al 2 O 3 ·2.5H 2 O to a mixture of 4Na 2 O·Al 2 O 3 ·12H 2 O and 6Na 2 O·Al 2 O 3 ·12H 2 O …”

Phase Equilibrium of the Ternary System K2SO4–KOH–H2O at 313.15, 333.15, 343.15, and 353.15 K

“…Gessner once studied the stable liquid–solid phase equilibria for the ternary system Na 2 O–Al 2 O 3 –H 2 O at low temperature. Zhang et al − investigated the phase equilibrium for the same system at high temperature by the Schreinemaker method. Du measured the phase equilibria for the ternary system K 2 O–Al 2 O 3 –H 2 O at 313.15 K by the isothermal method and proposed a separation method of aluminum salt from the alkali solution according to the phase diagram.…”

Solubility Equilibrium of the NaOH–H2O–Na2CrO4–Na2SiO3–NaAlO2 Multicomponent Systems Involved in the Liquid-Phase Oxidation of Chromite

“…The phase equilibrium of the ternary system of Na 2 O−Al 2 O 3 −H 2 O was also studied in the literature at high alkaline conditions. 10,11 In this study, Na 2 CrO 4 solubility in the ternary system of NaOH−H 2 O−Na 2 CrO 4 was first measured under different temperatures and NaOH concentrations. Subsequently, the solubility of Na 2 CrO 4 , NaAlO 2 , and Na 2 SiO 3 in the quaternary systems of NaOH−H 2 O−Na 2 CrO 4 −NaAlO 2 and NaOH− H 2 O−Na 2 CrO 4 −Na 2 SiO 3 , and the quinary system of NaOH−H 2 O−Na 2 CrO 4 −NaAlO 2 −Na 2 SiO 3 was studied at temperatures from 353.15 to 403.15 K and specific NaOH concentrations at 400, 500, and 600 g·L −1 , respectively.…”