Equilibrium Data and Correlation with Redefined NRTL Equation of Aqueous Two-phase Systems Based on 1,4-Bis-(2-hydroxyethyl)-piperazine and Na<sub>2</sub>SO<sub>4</sub>

Aqueous two-phase system (ATPS) is considered a new method to remove heat stable salts (HSS) from flue gas desulfurizer 1,4-bis-(2-hydroxyethyl)-piperazine (BHEP). In this work, the liquid-liquid phase equilibrium data of BHEP-Na2SO4 ATPS in 303.15 – 323.15 K were measured and correlated by NRTL equation with redefined adjustable characteristic constant at different concentrations. It revealed that correlate ternary well within experimental temperature range. The root-mean-square deviations (RMSD) average absolute (AAD) calculated value are less than 1.9% 1.5% respectively. binary interaction parameters have minor changes, ranging -68 75. Thereby, consistent actual calculation engineering application requirements.