Measurement and Thermodynamic Modeling of Liquid-Liquid Equilibrium Data for Ternary Systems (Water plus Formaldehyde plus Methyl Isobutyl Ketone/Cyclohexanone) at Different Temperatures

To explore the separation of formaldehyde from its aqueous solution, the liquid-liquid equilibrium data for the systems (water + formaldehyde + methyl isobutyl ketone/cyclohexanone) were measured at 303.15, 313.15, and 323.15 K in 101.3 kPa. The separation effect was judged by the separation factor and the partition coefficient. The S values of methyl isobutyl ketone and cyclohexanone are greater than unity, and the S and D values of cyclohexanone are greater than methyl isobutyl ketone, indicating that cyclohexanone is a suitable extractant compared with methyl isobutyl ketone. The reliability of the measured data is evaluated by Hand and Othmer-Tobias equations, and the R-2 values of the two equations are close to unity. The universal quasi-chemical theory and nonrandom two-liquid theory models were applied to fit the tie-line data of the investigated mixtures with a root mean square deviation lower than 0.01. Moreover, the binary interaction parameters were validated using a topology of Gibbs energy of mixing surface analysis.