The validity of the time-lag method for the characterization of mixed-matrix membranes

Abstract

Abstract The time-lag method is commonly used for the characterization of gas separation membranes. It allows the determination of the diffusion, permeability, and solubility coefficients from a single dynamic gas permeation experiment. This method is widely used for any membrane material, including glassy polymers, polymers with intrinsic microporosity, and mixed-matrix membranes. However, it is understood that for such determined transport coefficients, it is effective rather than intrinsic parameters that are estimated. In this paper, we focus on the applicability of the time-lag method for the characterization of theoretical mixed-matrix membranes (MMMs), in which impermeable particles of different shapes are ideally dispersed in a continuous polymer phase. Dynamic gas permeation experiments were simulated by solving the three-dimensional Fick s second law of diffusion numerically. The generated data allowed the estimation of the effective diffusion coefficient from the time lag and the ratio of the effective permeability and solubility coefficients.