Pebax-1657 mixed matrix membrane containing surface modified multi-walled carbon nanotubes for gas separation

Abstract

Poly ether-block-amide (Pebax-1657) is a promising polymeric membrane material applied in the separation of gas mixtures like CO₂/N₂ and O₂/N₂. In order to further improve its gas separation abilities and develop a membrane with a superior performance, multi-walled carbon nanotubes (MWCNTs) were incorporated into the Pebax-1657 matrix. In this study, the gas separation performance of Pebax-1657 and Pebax-1657/modified MWCNTs mixed matrix membranes (MMMs) was investigated for O₂, N₂ and CO₂ at different pressures and temperatures. The MWCNTs prior to embedding in the polymeric matrix, were functionalized and modified with carboxylic and amine groups and Triton X-100 as a strong surfactant. The functionalized MWCNTs and prepared MMMs were characterized by FTIR and SEM and tensile tests. The amine functionalized MMM showed 125% enhancement in selectivity of CO₂/N₂ compared to the neat membrane at 30 °C and 3 bar without reduction in the permeability of CO₂. This outstanding performance could be a consequence of the homogeneous dispersion of the MWCNTs within the Pebax matrix which was confirmed by SEM and tension results. For CO₂/N₂ separation, the MMM containing Triton X-100 modified MWCNTs overcomes the Robeson's upper bound and showed fairly good gas separation performance, compared with the similar Pebax mixed matrix membranes in the literature.