BREAKING THE LIMITATION OF COMPOSITION CHANGE DURING ISOTHERMAL MASS-TRANSFER PROCESSES AT THE SPINODAL

A governing equation describing the mass-transfer fluxes in practical membrane formation is derived using Markoffian and Onsager's thermodyn amic systems. This equation unambiguously demonstrates that isothermal mass-transfer fluxes at the spinodal composition may not be zero for systems operated in the gravitational field. This study suggests that the mass transfer equations derived by Cheng and Gryte are a special c ase of the present study and are not fully capable of describing the m ass transfer in practical membrane formation. Experimental results pub lished in previous literature qualitatively support our assessment. Th e Limitations of using Markoffian and Onsager's thermodynamic systems for membrane formation study are also reviewed. In conclusion, new the rmodynamic theories fur polymer solutions are needed to quantitatively describe the mass transfer fluxes in practical membrane formation.