Modeling and simulation of the phase-inversion process during membrane preparation

The objective of this work is to present a simple mathematical model to des cribe the main features of phase inversion by immersion precipitation. The model was developed for planar geometry and is used to simulate membrane sy nthesis. Two systems commonly used for membrane preparation were used for s imulations: cellulose acetate/acetone/water and polyetherimide/N-methylpyrr olidone/water. The influence of nonsolvent addition to initial polymer cast ing solutions, solvent addition to the coagulation bath, and geometric vari ables, such as polymer film thickness, on the Final precipitation condition s were studied through simulation and compared to available experimental da ta. The results are in good agreement with published results.(1-3) It is sh own that polymer film composition profiles at the moment of precipitation m ay give important information about the structure and substructure of forme d membrane. It is also shown, for both polymeric systems investigated in th is work, that the dynamics of the mass transfer process seems to be much mo re important than the influence of the concentration on the diffusion and t hermodynamic partition coefficients, as fair agreement with available exper imental data was obtained even when these coefficients were assumed to be c onstant. (C) 2001 John Wiley & Sons, Inc.