Determination and Correlation of Phase Equilibrium of the Ethanol/Isopropanol plus Manganese Sulfate plus Water Ternary Systems

The phase equilibrium of MnSO4 in water-alcohol solution is indispensable for the separation and purification of MnSO4 based on solvent-out effects. To investigate the phase behavior of MnSO4 in water-alcohol solution, the phase equilibrium of CH3CH2OH + MnSO4 + H2O systems at 303.15 and 313.15 K and the (CH3)(2)CHOH + MnSO4 + H2O system at 303.15 K has been determined. Five regions, namely, L (liquid), L-1 + S (liquid 1 + solid), L-1 + L-2 (liquid 1 + liquid 2), L-1 + L-2 + S (liquid 1 + liquid 2 + solid), and L-2 + S (liquid 2 + solid), are observed. Furthermore, the effects of alcohol types and temperatures on the formation of aqueous two-phase systems (ATPSs) are discussed in detail. It is found that the three experimental systems are partially miscible systems. The (CH3)(2)CHOH + MnSO4 + H2O system has a larger split phase region and better solvent-out effect than the CH3CH2OH + MnSO4 + H2O systems. Meanwhile, the temperature has a slight influence on the phase behavior and the formation of ATPSs. The solubility of MnSO4 decreases with an increasing alcohol concentration. In addition, the relationship between the w(MnSO4) and w(alcohols) of the binodal curves is obtained based on the Mistry equation, Merchuk equation, and Pirdashti equation. The NRTL model is applied to fit the liquid-liquid equilibrium. The correlation coefficients show that the experimental data is in good agreement with the calculated values. It is worth mentioning that the equilibrium solid phase is MnSO4 center dot H2O. This work provides basic data for manganese sulfate purification and can be applied to develop thermodynamic models of ATPSs.

Automated summary

The phase equilibrium behavior of MnSO4 in water-alcohol solution was investigated, and different combinations of liquid and solid phases were observed. The effects of alcohol types and temperatures on the formation of aqueous two-phase systems (ATPSs) were discussed. The results showed that the (CH3)2CHOH + MnSO4 + H2O system exhibited better solvent-out effect. The temperature had a slight influence on the phase behavior and the formation of ATPSs. This study provides basic data for manganese sulfate purification and can be applied to develop thermodynamic models of ATPSs.