Membranas de matriz mista preparadas a partir da dispersão de nanotubos de carbono funcionalizados com grupos oxigenados em polissulfona: caracterização e aplicação para separação de CO2

Abstract

Symmetric and asymmetric mixed matrix membranes (MMMs) were developed using polysulfone (PSF) and multi-walled carbon nanotubes functionalized with oxygenated groups (MWNT-O). The preparation of the symmetric membranes was performed by solvent evaporation technique (dry phase inversion), while the asymmetric membranes were obtained by immersion precipitation (wet phase inversion) and by combining the two methods (dry/wet phase inversion). MWNT-O with functionalization contents of 6 wt.% and 9 wt.% were used, incorporated into PSF with contents between 0.1 and 5 wt.%. The membranes were characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential exploratory calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and permeation tests with pure CO2 and N2. The polymer precipitation rate was affected by the incorporation of MWNT-O, such that significant changes occurred in the morphology of the MMMs. The thermal stability of the MMMs was slightly reduced and was shown to be dependent on their respective morphologies. The FTIR results indicated the presence of the MWNT-O in the MMMs and the formation of interactions of the functional groups present on the surface of the MWNT-O with the PSF. Considering the transport properties, the symmetric and asymmetric MMMs prepared with 1 wt.% of MWNT-O showed the best performance. For symmetric membranes, there were evidence that the incorporation of MWNT-O increased the tortuosity of the gas diffusion path, reducing the permeability and increasing the selectivity of the pure PSF membrane. For asymmetric membranes, in terms of productivity, the instantaneous precipitation method proved to be more effective, giving rise to the MMM that had the CO2 permeation increased from 11 to 80 GPU compared to the pure PSF membrane. On the other hand, in terms of selectivity, the delayed-immersion precipitation method proved to be more effective, originating a MMM with selectivity for CO2/N2 of 14.3, while the pure PSF membrane showed a selectivity of 9.5. The results indicate that PSF and MWNT-O can be successfully combined to prepare asymmetric membranes with potential application in CO2 separation.