Nanocellulose Crystal-Enhanced Hybrid Membrane for CO₂ Capture

Abstract

Developing a membrane material with both high CO2 permeability and high CO2/N2 selectivity is always desired for CO2 capture, while improving the sustainability of the membrane preparation process is of equal importance. In the current work, a nanocellulose crystal (CNC) was blended with hydrophilic Pebax 1657 for CO2 separation application. The CO2/N2 separation performance of Pebax 1657/CNC hybrid membranes with up to 40 wt % CNC was evaluated by mixed-gas permeation tests under both dry and humid conditions. The humid test condition simultaneously increases CO2 permeability and CO2/N2 selectivity of all CNC/Pebax hybrid membranes compared to those under dry conditions. Introduction of only 5 wt % CNC into Pebax 1657 realizes 42 and 18% increments in CO2 permeability (305.7 Barrer) and CO2/N2 selectivity (41.6), respectively. However, further increasing the CNC loading increases the tortuosity of the membrane and results in the self-assembly of CNC in the Pebax matrix, which is observed by SEM, thus leading to both reduced gas permeability and CO2/N2 selectivity. The CO2/N2 separation results of 5 wt % CNC/Pebax locate close to Upper Bound 2008, showing its potential as a CO2/N2 separation membrane material.

Effects of Porous Supports in Thin-Film Composite Membranes on CO2 Separation Performances

“…It is well accepted that increasing the RH value will enhance the Pebax gas permeability [ 36 ]. For instance, in our previous study, the CO 2 permeability was greatly improved as the RH value increased [ 27 , 37 ]. However, in the present study, the CO 2 permeance of the Pebax/PAN membrane was sharply reduced during humidification, denoting that the PAN support dominated the gas transport in the TFC membrane, rather than the Pebax layer.…”

“…As most CO 2 -containing streams include water vapor, and water is involved in CO 2 transport mechanism, water vapor is critical in membranes for CO 2 separation. Water vapor could not only contribute to the reversible reaction involved in the facilitated transport mechanism and swell the selective layer membrane materials [ 27 , 28 ]. However, these also significantly affect the mass transfer in porous supports.…”

Pebax/Modified Cellulose Nanofiber Composite Membranes for Highly Enhanced CO2/CH4 Separation

“…The chemical functional group of Pebax/SCNF membranes was determined by Fourier-transform infrared spectroscopy (FTIR) as shown in Figure . The peaks of amide and ketone groups of pure Pebax (Figure a) were found around 3300 cm –1 (N–H), 1636 cm –1 (H–N–CO), and 1732 cm –1 (CO stretching), corresponding to polyamide (PA) blocks (hard segments). ,,, The vibrational peaks were observed around 1096 and 847 cm –1 , corresponding to the C–O–C ether group in poly­(ethylene oxide) (PEO) blocks (soft segments) of Pebax. ,,, Displayed in Figure b, the as-synthesized SCNF showed typical peaks of cellulose with O–H stretching (3370 cm –1 , broad band), C–H stretching of methyl and methylene groups (2800–2900 cm –1 ), C–O–C glycoside bond (1164 cm –1 ), C–OH stretching (1063 cm –1 ), and ring vibration of β-glycosidic linkages between glucose units (897 cm –1 ). , The succinic group was successfully functionalized on the cellulose structure as confirmed by the peak at 1730 cm –1 , which can be assigned to carbonyl (CO) stretching vibration of the ester linkages. , The small amount of SCNF in Pebax did not significantly change the vibrational patterns of the whole FTIR spectrum of Pebax/SCNF composites compared with neat Pebax. In addition, multiple peaks of SCNF overlapped with those characteristic peaks of Pebax.…”

“…30 The 5 wt % cellulose nanocrystal (CNC)-blended Pebax 1657 membranes were studied for a CO 2 /N 2 separation material and showed high CO 2 permeability (305.7 Barrer) and CO 2 /N 2 selectivity (41.6). 31 The high loading of CNC up to 40% increased the self-assembly of CNC in the Pebax matrix, leading to a reduction in both gas permeability and selectivity.…”

Recent developments in polysaccharide and lignin-based (nano)materials for CO2 capture

“…41–44 Among these, natural polymers or biopolymers are very efficient materials for CO 2 capture and polysaccharides have attracted much attention. 45–51…”