que se tornou para mim exemplo de ética, comprometimento e didática. Ao meu parceiro de trabalho, o Doutorando Abdul Orlando Cárdenas Gómez, cuja cooperação foi extremamente importante para conclusão desta pesquisa. Ele dedicou seu tempo, conhecimento e trabalho para realizarmos os testes e as modificações na bancada.

Multiwalled carbon nanotubes (MWCNTs)‐containing polysulfone (PSf) mixed matrix membranes (MMM) are prepared using phase inversion by immersion precipitation. MWCNT are functionalized with oxygen groups to allow the dispersion of the filler in the polymer solution. Membranes with 0, 1, 3 and 5% w/w MWCNTs in PSf are prepared. The addition of the filler changed the permeability of pure PSf. The best results are found for the 1 wt% membrane, with increase in CO2 permeability of 660% and ideal selectivity CO2/N2 of 547%. The MMM also exhibited good thermal stability for gas separation. DSC and SEM results revealed that the addition of 1wt% of the filler caused changes in chain arrangements and membrane morphology.

Graphene is a promising material for membrane applications. However, the graphene production with large specific area and good structural quality is a challenge. Therefore, the production and characterization of composite membranes with graphene grown by chemical vapor deposition (CVD) over a porous polymethylmethacrylate (PMMA) substrate was investigated. The experimental strategy consisted in applying CVD‐graphene on a PMMA surface using PMMA‐assisted graphene wet transfer. The proposed methodology resulted in large‐area membranes with 2 cm diameter. The samples were characterized by Raman spectroscopy, indicating the presence of graphene in good quality and relative structural integrity. The analysis by scanning electron microscopy revealed the formation of a microporous support with an asymmetric structure. The gas permeation measurements of graphene/PMMA membranes showed a permeability reduction of 81.9% for CO2 and 83.7% for N2. The contribution of PMMA to flow resistance was 2% and 11% for CO2 and N2, respectively, and the contribution of graphene was 98% and 89% for CO2 and N2. Therefore, this research presents a potential advance in transferring graphene to porous support, and the impermeability process of membranes composed of graphene/PMMA, a fundamental step for the development of graphene membranes before the production of controlled‐sized pores.

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Mixed matrix membranes (MMMs) consist of a polymeric phase and a dispersed solid filler such as zeolites or carbon nanotubes. We prepared symmetric and asymmetric polysulfone-based MMMs containing functionalized multi-walled carbon nanotubes (MWNT-O) for CO2/N2 separation. Maxwell’s model was used to predict the permeabilities of MMMs. The permeability achieved using the model exhibited a good fit of the model in symmetric MMMs, especially for CO2. This can be potentially attributed to the high affinity of the system toward the polymer matrix. The permeability recorded using Maxwell’s model could not reflect the properties of the asymmetric membranes, and this could be attributed to the generation of voids around the fillers or defects present on the surface of the skin. Finally, a mathematical fit was proposed to improve prediction accuracy for both the MMM systems.

Carbon dioxide separation from flue gases is an important challenge to be faced. Membrane processes are a promising alternative to increase technical and economical constraints once the development of materials with superior characteristics are attained. Integrally asymmetric mixed matrix membranes (MMMs) were prepared by dry/wet phase inversion process of polysulfone (PSF) containing oxygen‐functionalized multiwalled carbon nanotubes (MWNT‐O). Fourier transform infrared (FTIR) spectroscopy confirmed the presence of MWNT‐O in MMMs. Thermal gravimetric analysis (TGA) showed that MMMs are stable up to 150°C. Photomicrographs from scanning electron microscopy (SEM) revealed that MMMs consist of an asymmetric structure with a skin layer supported on a sponge‐like substructure. The pore size of the support of MMMs increased with MWNT‐O content from 0.4 to 0.8 wt.% and the thickness of the dense layer decreased. However, when the content of MWNT‐O increased to 1 wt.%, the pore size decreased, and the dense layer increased. Therefore, MMMs changed CO2 separation performance. For 1 wt.% MWNT‐O loading compared to the neat polymer, CO2 permeance and CO2/N2 selectivity was increased from 1.5 to 2.7 GPU, and from 9.5 to 14.3, respectively.

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