The nano-porous sodium zeolite Y (NaY) was ion exchanged with cobalt(II) cations. The Co2+ exchanged NaY zeolite, Co(II)–NaY, was incorporated (0–20 wt%) into the cellulose acetate (CA) membrane to form new mixed matrix membranes (MMMs), the CA/Co(II)–NaY. The particles and MMMs were characterized by UV–vis DRS, N2 adsorption–desorption isotherm, XRD, SEM, and FTIR-ATR. The CO2 and N2 permeation measurements (2–10 bar) were carried out to determine the potential of the MMMs for CO2 separation. Characterization results confirmed a suitable ion exchange treatment of the zeolite and as well the formation of MMMs with favorable morphological/structural properties. The gas permeation results of CA/Co(II)–NaY membranes revealed considerable enhancement of CO2/N2 ideal selectivities with respect to the neat CA and CA/NaY membranes. The ideal selectivity (=29.9; with a permeability of 3.28 Barrer) of 15 wt% Co(II)–NaY loaded MMM at 4 bar was increased about 17.3% in comparison with the ideal selectivity of neat CA membrane (=25.5; with a permeability of 2.28 Barrer) and also increased 44.4% in comparison with that of 15 wt% NaY loaded MMM (=20.7; with a permeability of 3.43 Barrer). Moreover, the CO2 permeability was increased about 43.9% in comparison with the neat CA and approximately remained unchanged, compared with the CA/NaY 15 wt%. In addition, the optimum zeolite loading decreased from 20 wt% for CA/NaY (with a CO2 permeability of 4.87 Barrer and ideal selectivity of 25.0) to 15 wt% for CA/Co(II)–NaY, which also causes CA/Co(II)–NaY to surpass the parents' CA and CA/NaY membranes from the most prominent technical factor of selectivity.
