Theoretical models for gas separation prediction of mixed matrix membranes: effects of the shape factor of nanofillers and interface voids

Abstract

In this work, a new model is developed by modifying the existing Maxwell–Wagner–Sillars (MWS) model to predict the gas separation properties of mixed matrix membranes (MMMs). The new modified MWS model, for the first time, provides the simultaneous exploration of the role of nanofillers/matrix interface voids and the exact geometrical shape of nanofillers in predicting the gas separation properties of MMMs. To unveil the crucial role of nanofillers/matrix interface voids, a mixed matrix membrane is considered a three-component system composed of the polymer matrix as the continuous component, nanofillers as the dispersed component and the interface voids between the two components. Moreover, the new model elucidates the role of the exact ellipsoidal shape of nanofillers within the membrane on the gas separation of MMMs by considering the shape factor of nanofillers. The newly developed modified MWS model is accurately able to predict the gas permeation of MMMs with a lower average absolute relative error (%AARE) of around 8% compared with the around 30% for conventional models such as the Maxwell model, Bruggeman model, Lewis–Nielsen model and Pal model and even compared with the modified Maxwell model (∼24%).

Molecular Dynamics Simulations of Gas Transport Properties in Cross-Linked Polyamide Membranes: Tracing the Morphology and Addition of Silicate Nanotubes

“…The diffusion coefficient of gas molecules through a dense membrane is governed by the kinetic diameter of penetrant gas. The kinetic diameter of different gases decreases in the sequence CH 4 > N 2 > CO 2 . − It is expected that the smaller penetrant gas shows a higher diffusion coefficient through the dense membrane. Although the CO 2 molecule has a smaller kinetic diameter than CH 4 and N 2 , the lowest simulated diffusivity is observed for CO 2 .…”

Molecular Simulations of MXene Nanosheet-Based Membranes for Syngas Separation

“…The main assumption of the Maxwell’s equation is that the polymer–nanomaterial interface is perfect, and the model is applicable for MMM with a low nanomaterial concentration . The geometry shape factor ( n ) for MXene structures with 2D nanolayer is calculated as 0.161 using eqs S1–S2 . For the MXene-based MMMs, the volume ratio (ϕ) is assumed to be 0.2, as for the MOF-based MMMs …”

“…49 The geometry shape factor (n) for MXene structures with 2D nanolayer is calculated as 0.161 using eqs S1−S2. 50 For the MXene-based MMMs, the volume ratio (ϕ) is assumed to be 0.2, as for the MOF-based MMMs. (1) where P P , P MXene , and P MMM represent the permeability (Barrer) of polymer, MXene, and MMM, respectively.…”

Metal–Organic-Frameworks Based Mixed-Matrix Membranes for CO2 Separation: An Applicable-Conceptual Approach

“…The most critical challenge in development of MMMs is the fillers/polymer matrix compatibility, that governs the gas separation performance. Therefore, investigating the fillers/polymer matrix interactions allows us to find out the key features of gas separation in MMMs. , Hence, interfacial engineering, that results in different interfacial morphologies, has gained more attention in fabricating gas separation membranes with desirable properties. , The poor polymer/filler adhesion leads to the “sieve-in-cage”, also called interfacial void, morphology in MMMs . This undesirable morphology restricts the gas separation performance of MMMs.…”

“…88,89 Hence, interfacial engineering, that results in different interfacial morphologies, has gained more attention in fabricating gas separation membranes with desirable properties. 90,91 The poor polymer/filler adhesion leads to the "sieve-in-cage", also called interfacial void, morphology in MMMs. 92 This undesirable morphology restricts the gas separation performance of MMMs.…”