Plasticization Modeling in Cellulose Acetate/NaY Mixed Matrix Membranes

Abstract

The plasticization of mixed matrix membranes (MMMs) in the presence of solid particles differs from pure glassy polymeric membranes. This study aims to develop a mathematical model for gas permeability in the glassy polymer/nano-porous filler MMMs, considering the plasticization phenomenon in the presence of the solid particles. The diffusivity of each component is assumed to be a function of the plasticization in the presence of nano-porous fillers. The partial immobilization model with the insertion of filler contributions in gas solubility of MMMs is also applied to determine the fraction of sorbed mobile gases. In this case, the model parameters were determined by fitting the experimental data of cellulose acetate/sodium Y zeolite (CA/NaY) MMMs for CO2 /N2 separation. The results showed that the plasticization parameter (β) is reduced by increasing the zeolite content in the MMMs, both for CO2 and N2 gases. The MMM plasticization declined by a shift in the plasticization pressure towards larger values. Except for the MMM with 20 wt.% NaY content, CO2 - induced plasticization fugacities of all the MMMs were best modeled with a relative error of less than 8%. Moreover, an acceptable mean relative error of 7.57% was obtained for all the MMMs containing 0-20 wt. % NaY. Statistical analysis with calculating the Pearson correlation's parameters showed a direct and strong relationship between the two coefficients C′HA and b. Furthermore, it revealed a close relationship between all other coefficients, while no relationships were observed between D0 and β, and also, F and D0 for both the CO2 and N2 gases, maybe because of the small sizes of these coefficients. The zeolite particles play a role of anti-plasticizer. Additionally, by increasing the zeolite loading, the gas diffusivity variations in the membranes decreased. This reduction is another sign of the plasticization reduction in the MMMs as compared to the pure glassy membranes.