Biomass derived carboxylated carbon nanosheets blended polyetherimide membranes for enhanced CO₂/CH₄ separation

The fillers/nanofillers combinations with ideal interfacial morphologies could adjust the performance of pristine polymeric membranes and enhance the gas separation performances. In this study, biomass-derived 2D carboxyl functionalized nanocarbon (nanosheets) were produced from pyrolysis of the rain/monkey pod tree (Samanea saman) leaves. The X-ray diffraction, Raman spectroscopy, and X-Ray photoelectron spectroscopy (XPS) confirmed the chemical structure and carboxyl functionalization of carbon nanosheets (CCNS). The carboxyl-functionalized nanosheets blended into polyetherimide (PEI) solutions was used to fabricate mixed matrix membranes (MMMs) through modified dry/wet phase inversion method using different wt. % [0.0%, 0.25%, 0.5% and 1.0% of CCNS] of fillers into the pristine PEI NMP solutions. Surface and cross-sectional micrographs discerned the defects and dispersion of CCNS into the polymer matrix. Finally, the transport properties of pure gases (CH₄ and CO₂) were evaluated using constant pressure/variable volume apparatus. The gas separation studies showed improved permeance and selectivity of MMMs [(P_CO2 = 1.84 GPU, (α = CO₂/CH₄) = 42.73] than pristine PEI membranes [P_CO2 = 1.29 GPU, (α = CO₂/CH₄) = 23.30] under identical conditions of pressure and temperature.