A comparative theoretical and experimental study on liquid-liquid equilibria of membrane forming polymeric solutions

Abstract

The phase equilibria of two ternary system of Polyethersulfone (PES) - n-methyl pyrolidine (NMP) – distilled Tap water (H2O) and Polysulfone (PSf) – NMP - H2O has been investigated critically using both theoretical and experimental methods. The cloud point measurement technique was used for determination of experimental binodal curves. Gamma-gamma (γ-γ), gamma-phi (γ-φ), phi-gamma (φ-γ) and phi-phi (φ- φ) approaches were assessed using measured binodal data. Compressible regular solution (CRS), Nonrandom Two Liquids model (NRTL), Universal Quasi-Chemical theory (UNIQUAC) were used for activity coefficient (gamma) calculations and Gasem–Gao–Pan–Robinson modification to the PR EOS (PRGGPR) and Twu–Coon–Cunningham modification to the RK EOS (RKTCC) were used for fugacity coefficient (phi) calculations. The Othmer-Tobias and the Hand correlation equations were used to check the consistency of the obtained tie-line data, by which the distribution coefficients (D) and separation factors (S) were calculated. Description of LLE using CRS-UNIQUAC in a gamma-gamma approach, the RKTCC-RKTCC in a phi-phi approach, CRS-RKTCC in a gamma-phi approach and the RKTCC-UNIQUAC in a phi-gamma approach gives the best agreement and correlation to the experimental data. The overall performance of gamma-gamma approach using CRS-UNIQUAC model revealed an averaged Accumulative Absolute Relative Deviation (AARD) of 2.47%.