Abstract
Due to the high affinity of ceria (CeO2) towards carbon dioxide (CO2) and the high thermal and mechanical properties of cellulose triacetate (CTA) polymer, mixed-matrix CTA-CeO2 membranes were fabricated. A facile solution-casting method was used for the fabrication process. CeO2 nanoparticles at concentrations of 0.32, 0.64 and 0.9 wt.% were incorporated into the CTA matrix. The physico-chemical properties of the membranes were evaluated by SEM-EDS, XRD, FTIR, TGA, DSC and strain-stress analysis. Gas sorption and permeation affinity were evaluated using different single gases. The CTA-CeO2 (0.64) membrane matrix showed a high affinity towards CO2 sorption. Almost complete saturation of CeO2 nanoparticles with CO2 was observed, even at low pressure. Embedding CeO2 nanoparticles led to increased gas permeability compared to pristine CTA. The highest gas permeabilities were achieved with 0.64 wt.%, with a threefold increase in CO2 permeability as compared to pristine CTA membranes. Unwanted aggregation of the filler nanoparticles was observed at a 0.9 wt.% concentration of CeO2 and was reflected in decreased gas permeability compared to lower filler loadings with homogenous filler distributions. The determined gas selectivity was in the order CO2/CH4 > CO2/N2 > O2/N2 > H2/CO2 and suggests the potential of CTA-CeO2 membranes for CO2 separation in flue/biogas applications.
Highlights
The separation of CO2 from other light gases has been practiced for decades
Polymer membrane-based gas separation has been considered a promising technology due to advantages such as low energy consumption, operational simplicity, environmental friendliness and high efficiency compared to other gas separation techniques [2]
Despite advancements in the design of novel membrane materials with improved gas separation performance, polymers still play a crucial role in the current gas separation field due to their easy processability and solid mechanical strength, which lay the foundation for their industrial deployment [3]
Summary
The separation of CO2 from other light gases has been practiced for decades. The significance of this process is directly linked to the importance of CO2 as a major anthropogenic greenhouse gas responsible for climate change [1]. Despite advancements in the design of novel membrane materials with improved gas separation performance, polymers still play a crucial role in the current gas separation field due to their easy processability and solid mechanical strength, which lay the foundation for their industrial deployment [3]. Permeability can be improved by increasing the polymer’s free volume or using structural features to alter the interchain polymer spacing. This approach is unable to improve selectivity [5]. Improving both permeability and selectivity above the Robeson upper bound is desirable but challenging to achieve using a neat polymeric membrane
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