CO₂ Separation Membranes Consisting of Ionic Liquid/CdO Composites

CdO nanoparticles were utilized in the fabrication of a composite membrane containing the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM+BF⁻ ₄) for CO₂ separation. The use of BMIM+BF⁻ ₄containing CdO nanoparticles as a CO₂ separator greatly improved separation performance. The ideal selectivity for CO₂/N₂ was 32.5 with a CO₂ permeance of 57.1 GPU when CdO 4 liquid. The enhanced separation performance nanoparticles were incorporated into the BMIM+BF⁻ ₄and the was attributed to increased CO₂ solubility facilitated by both the free ions in BMIM+BF⁻ ₄ oxide layer of the CdO nanoparticle. The CdO nanoparticles were identified with transmission electron microscopy and the physical and chemical properties of the membranes were investigated using scanning electron microscopy, Raman spectroscopy and TGA. Interestingly, we found a correlation between CO₂ permeance and electronegativity differences between the metal and oxygen for CO₂ separation membrane. The electronegativity differences between the metal and oxygen was ZnO (1.79) > CdO (1.75) > CuO (1.54) > AgO (1.51). The order of CO₂ permeance was ZnO in BMIM+BF⁻ ₄ (101 GPU) > CdO in BMIM+BF⁻ ₄ (57.1 GPU) > CuO in BMIM+BF⁻ ₄ (52.4 GPU) > AgO in BMIM+BF⁻ ₄ (14.1 GPU).