Polyethyleneimine-modified multi-walled carbon nanotubes mixed matrix membranes for CO2/N2 separation

Abstract

In recent years, membrane separation technology has received extensive attention in CO2/N2 separation. Carbon nanotubes (CNTs) were regarded as ideal fillers for constructing high permeability mixed matrix membranes (MMMs) due to their special tubular structure. However, the interfacial compatibility between CNTs and organic polymer phases is a large challenge, seriously hindering the development of carbon-based mixed matrix membranes. In this work, we proposed a novel polyethyleneimine (PEI) surface functionalization strategy to effectively improve the compatibility between multi-walled carbon nanotubes (MWCNTs) and Pebax-1657. The as-prepared PEI@MWCNTs/Pebax-1657 MMMs were analyzed by XRD, EDS, FTIR, TG, etc. The PEI can improve the compatibility of MWCNTs with the polymer matrix. In addition, the abundant amino groups in the PEI structure can provide ample active sites for CO2, which can improve CO2 permeability and CO2/N2 selectivity simultaneously. Combining the low resistance of MWCNTs to gas transport, the membrane showed 178.08% enhancement in selectivity (82.06) of CO2/N2 compared to the pristine membrane with 152.49% increment in the permeability (150.51 Barrer) of CO2. This work provides a novel strategy for preparing carbon-based mixed matrix membranes with high gas separation performance.