Polysulfone Mixed-Matrix Membranes Comprising Poly(ethylene glycol)-Grafted Carbon Nanotubes: Mechanical Properties and CO₂Separation Performance

Polysulfone (PSF)-based mixed-matrix membranes (MMMs) were developed through incorporation by solvent casting of poly(ethylene glycol)-grafted carbon nanotubes (PEG-g-CNTs) into the polymer matrix. Single-gas permeability and the respective perm-selectivity values of the resulting MMMs for CO2, CH4, and N2 along with mixed-gas selectivities were determined at various temperatures and pressures. The performance was further analyzed by obtaining gravimetrically gas adsorption isotherms and interpreting the results to determine the solubility and diffusivity coefficients of the prepared membranes. Simultaneous improvement in CO2 permeability, selectivity, and mechanical robustness was achieved. Indicatively, an increase in CO2 permeability by 52.4% at 1.5 bar was discerned for the MMM containing 5 wt % PEG-g-CNTs along with enhancements of 81 and 74% in CO2/N2 and CO2/CH4 perm-selectivities, respectively, while an up to 43.4% increase in tensile modulus and a 12.5% increase in tensile strength were achieved as well. This performance, in conjunction with the stability of the fillers, and the low cost, structural stability, and commercial availability of the polymer make the PSF/PEG-g-CNT MMM a promising base case for developing industrially relevant CO2 separation membranes.