Crystallization separation of Na₂CO₃ and Na₂MoO₄ from the high-salinity ash slag produced by production process of Na₂MoO₄ based on the theory of phase equilibrium

High-salinity ash slag containing Na2CO3 and Na2MoO4 produced from the production process of Na2MoO4 brings about the resource waste and environmental pollution issues. To realize the resource utilization of these high-salinity ash slag, the phase equilibrium data of the ternary Na2CO3-Na2MoO4-H2O system at 298.15 K and 323.15 K were determined using the isothermal dissolution equilibrium method, and the equilibrium solid phase was determined by X-ray diffraction. By comparing the phase diagrams of the ternary Na2CO3-Na2MoO4-H2O system at 298.15 K, 323.15 K, and 353.15 K, the change rules of the crystallization region were analyzed. The Pitzer and HW models were used to calculate the ionic interaction parameters of theta(MoO4-CO3) and psi(Na-MoO4-CO3), which could be further used to predict the solubility curves of the ternary Na2CO3-Na2MoO4-H2O system. The calculation results were in good agreement with the experimental results. Furthermore, the phase diagrams of the ternary Na2MoO4-Na2CO3-H2O system at 298.15 K and 353.15 K were selected to design a process for the highly-efficient recovery of Na2MoO42H(2)O and Na2CO3H2O from the high-salinity ash slag. The experimental results showed that the one-way recovery rate of Na2CO3 could reach 92.55%, with a purity of 99.62%, and that of Na2MoO42H(2)O is 45.61%, with a purity of 99.14%. These results were almost consistent with the theoretical calculation results. After multiple cycles, Na2CO3 and Na2MoO4 could be completely recovered