Polyvinylamine/graphene oxide/PANI@CNTs mixed matrix composite membranes with enhanced CO2/N2 separation performance

Lamellar PANI@CNTs-GO materials were prepared by intercalating polyaniline-coated carbon nanotubes (PANI@CNTs) in graphene oxide (GO) layers to regulate the interlayer spacing. Mixed matrix membranes (MMMs) with tuned structures were achieved by coating a mixed dispersion of PANI@CNTs-GO and polyvinylamine (PVAm) on an asymmetric polysulfone (PSf) membrane for enhancing its CO2 separation performance. The Fourier-transform infrared spectroscopy results showed that PANI was successfully coated on the surface of the CNTs. The X-ray diffraction results confirmed the intercalation of GO sheets with PANI@CNTs. PANI@CNTs-GO was uniformly dispersed in PVAm, as confirmed by scanning electron microscopy. The attenuated total reflectance Fourier transform infrared spectroscopy results revealed that strong interfacial interactions were present between PVAm and PANI@CNTs-GO. The MMM loaded with 1 wt% PANI@CNTs-GO showed the best CO2 separation performance with a CO2 permeance of 170 GPU and a CO2/N-2 selectivity of 122.4 at 1 bar under the pure gas condition. These values were much higher than those of the pristine PVAm membrane (CO2 permeance = 73 GPU and CO2/N-2 selectivity = 45.7). This enhanced separation performance can be mainly attributed to the effect of the facilitated transport carriers from amine groups in the interlayer spacing and the molecular sieving effect of the interlayer spacing. The MMMs exhibited excellent long-term stability even under the mixed-gas conditions for over 300 h with a CO2 permeance of 264 GPU and a CO2/N-2 selectivity of 149.8.