Amine-Functionalized MCM-41/Polysulfone Mixed Matrix Membranes: Preparation, Characterization and Its Performance in CO2/CH4 Separation

Mixed matrix membrane or MMM, comprising polymeric membrane and inorganic fillers, is promising in gas separation as it combines the advantages of the two components. However, the fabrication of MMM is challenging due to the issue of agglomeration of inorganic fillers and the formation of interfacial voids on MMM surface morphology. Nevertheless, the dispersion of the filler and interaction between filler-polymer can be improved by modifying filler with binding agents, which improves the separation performance of MMM. This work is about synthesis and characterization of new modified fillers to be used in MCM-41/Psf MMM for CO2/CH4 separation. Mesoporous MCM-41 silica is modified with primary (APTMS) and secondary amine functional groups (AAPTMS) using grafting method. MMMs with MCM-41, APTMS-MCM-41 and AAPTMS-MCM-41 were synthesized using dry/wet inversion method. The filler loadings were set as 0.1 wt% and 1 wt%. The synthesized MMMs were characterized using TEM, SEM, FT-IR and EDX. The CO2/CH4 separation performance of MMMs was tested using gas permeation test rig, where the permeance and selectivity of MMMs were compared to pure Psf membrane. TEM results showed reduction of particles agglomeration after amine functionalization. Besides, the hexagonal structure of MCM-41 remained intact after functionalization. Based on the results obtained from SEM and EDX, the fillers were uniformly dispersed in the Psf matrix, while the presence of amine functional groups APTMS and AAPTMS on MCM-41 has improved the compatibility between fillers and matrix. FT-IR results confirmed the successful grafting of the amine groups on MCM-41 at the band of ~690 cm-1 and ~1530cm−1. The incorporation of APTMS-MCM-41 into Psf has successfully increased the CO2 permeability by 410.44% (0.1 wt% loading) and 569.97% (1 wt% loading), while AAPTMS-MCM-41 has 114.10% (0.1 wt% loading) and 309.32% (0.1 wt% loading). APTMS-MCM-41 has better overall performance than AAPTMS-MCM-41 in terms of permeance. All MMMs showed an inverse relationship between permeance and ideal selectivity as indicated by Robeson’s trade-off bound.