Polyethersulfone/cloisite 15A mixed matrx membranes for gas separation

Abstract

Fabrication of mixed matrix membrane (MMM) with superior gas transport properties is challenging due to the poor dispersion of the filler in the membrane and the complicated interaction of polymer-clay surface. The purpose of this study is to develop polymer-clay based MMM for carbon dioxide (COz) removal from methane (CH+) and to study the effects of interface voids and clay dispersion on gas separation. Asymmetric flat sheet MMM from polyethersulfone (PES) and sonicated cloisitel5A (C15A) clay particles was prepared by a controlled fabrication parameters and phase inversion technique. The impacts of adding C15A on the MMM properties were investigated by using morphological, structural, thermal, mechanical, functional group and performance analyses. In the first phase of the study, the effect of different loading of C15A was investigated. Significant changes on the membrane morphology and thermal stability were observed for the fabricated MMMs. At 1 weighr% ClsA loading (PES/C15A1), MMM showed the best gas transport properties wrfh 37% and l00o/o improvement on CO2 permeance and COzICH+ selectivity, respectively. For the second part of the study, the state of dispersion of the silicate layers in MMM was investigated by qualitative and quantitative analyses. Partial intercalated and exfoliated silicate layers in PES/C15A1 contributed to the enhancement of the membrane mechanical properties. The increase of tortuosity in MMM reduced the CH+ peflneance with a significant improvement for the COzlCHq selectivity from22.57 to 46.89. Particle size measurement, particle density measurement and free-path spacing measurement also demonstrated that the dispersion state in PES/C15A1 was striking with the increase in aspect ratio, dispersed single silicate layers, particle density and evidence of several tactoid classes. It was discovered that high C15A loading (5 weight%) deteriorated the PES/C15A5 performance due to the interfacial voids. Hence in the third phase, C154 was functionalized with 3-aminopropyl triethoxysilane coupling agent. Selectivity improvement was observed on the modified-Cl5A MMM suggesting a better interaction between the clay surface and PES matrix. From this study, incorporation of C15A has shown great CO2lCHa separation enhancement and can be regarded as potential filler for MMM.