Cellulose Triacetate-Based Mixed-Matrix Membranes with MXene 2D Filler—CO2/CH4 Separation Performance and Comparison with TiO2-Based 1D and 0D Fillers

Abstract

Mixed-matrix membranes (MMMs) possess the unique properties and inherent characteristics of their component polymer and inorganic fillers, or other possible types of additives. However, the successful fabrication of compact and defect-free MMMs with a homogeneous filler distribution poses a major challenge, due to poor filler/polymer compatibility. In this study, we use two-dimensional multi-layered Ti3C2Tx MXene nanofillers to improve the compatibility and CO2/CH4 separation performance of cellulose triacetate (CTA)-based MMMs. CTA-based MMMs with TiO2-based 1D (nanotubes) and 0D (nanofillers) additives were also fabricated and tested for comparison. The high thermal stability, compact homogeneous structure, and stable long-term CO2/CH4 separation performance of the CTA-2D samples suggest the potential application of the membrane in bio/natural gas separation. The best results were obtained for the CTA-2D sample with a loading of 3 wt.%, which exhibited a 5-fold increase in CO2 permeability and 2-fold increase in CO2/CH4 selectivity, compared with the pristine CTA membrane, approaching the state-of-the-art Robeson 2008 upper bound. The dimensional (shape) effect on separation performance was determined as 2D > 1D > 0D. The use of lamellar stacked MXene with abundant surface-terminating groups not only prevents the aggregation of particles but also enhances the CO2 adsorption properties and provides additional transport channels, resulting in improved CO2 permeability and CO2/CH4 selectivity.

Gas-Phase Adsorption of Dimethyl Methylphosphonate over Ce(OH)4@PIM-1 Composites Prepared via Matrix Incorporation and Surface Coating Methods

“…This occurs because the surface-coated metal hydroxides provide more accessible and unobstructed sites, promoting quicker diffusion and adsorption of DMMP. In contrast, the incorporated Ce­(OH) 4 , while providing more overall binding sites, may suffer from restricted diffusion pathways and increased tortuosity within the composite, thus exhibiting slower kinetics but higher capacity . In addition, the incorporation of Ce­(OH) 4 particles into polymeric substrates improves the composites’ mechanical stability and heat resistance .…”

“…In contrast, the incorporated Ce(OH) 4 , while providing more overall binding sites, may suffer from restricted diffusion pathways and increased tortuosity within the composite, thus exhibiting slower kinetics but higher capacity. 34 In addition, the incorporation of Ce(OH) 4 particles into polymeric substrates improves the composites' mechanical stability and heat resistance. 35 Therefore, the difference in the adsorption kinetics and capacity can be mechanistically rationalized through the spatial orientation and availability of Ce(OH) 4 , whether it is incorporated into or coated on the PIM-1 matrix, affecting both the diffusion of DMMP molecules and their subsequent interactions with the adsorption sites.…”

Liquid-Phase Adsorption of Dimethyl Methylphosphonate on Poly(ether imide) and its Metal Hydroxide-Integrated Composites

“…Particularly, the surface-coated metal hydroxides offer more readily available sites, facilitating faster diffusion and DMMP adsorption. In contrast, while incorporated metal hydroxides yielded more binding sites, their inherent structure might introduce greater diffusion barriers and tortuosity, leading to slower kinetics but increased capacity over time . Moreover, incorporating Ce­(OH) 4 or Zr­(OH) 4 particles within polymers enhances the resultant composite’s thermal and mechanical properties.…”

“…In contrast, while incorporated metal hydroxides yielded more binding sites, their inherent structure might introduce greater diffusion barriers and tortuosity, leading to slower kinetics but increased capacity over time. 41 Moreover, incorporating Ce(OH) 4 or Zr(OH) 4 particles within polymers enhances the resultant composite's thermal and mechanical properties. The variation in adsorption behavior, illustrated in Figure 3, highlights the importance of material design in fine-tuning the adsorption characteristics.…”

Chiral separation of D,L‐phenylglycine by cellulose triacetate membranes

“…Meanwhile, membrane separation with its low energy consumption, ease of operation, and continuous separation is considered the most favorable chiral separation technique. [32][33][34][35] CTA membranes are extensively utilized in diverse applications, including desalination, [36][37][38][39] wastewater treatment, [40][41][42] and gas separation, 43,44 owing to their straightforward fabrication, high durability and stability. The six-membered ring of the CTA backbone contains chiral carbons, thus potentially enabling CTA to facilitate chiral recognition.…”