Fabrication of a Polyetherimide/ZIF-8 Composite Membrane for Separating Carbon Dioxide from Methane.

In the present work, a polyetherimide/ZIF-8 composite membrane was fabricated by solution casting technique. The prepared membranes were Characterized using Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy – attenuated total reflectance (FTIR-ATR), energy dispersive X-ray (EDAX) and X-ray diffraction (XRD). Furthermore, the membrane''''s performance in separating carbon dioxide and methane was analyzed through single gas permeability measurements. FTIR-ATR spectrum of the prepared membrane confirmed the functional groups of polyetherimide. XRD analysis showed that the additive was well dispersed in the polymer, resulted in a reduction in the membrane''''s crystallinity. EDAX analysis confirmed the existence and proper dispersion of Zn particles in the membrane. Finally. The results of permeability tests showed that adding ZIF-8 to the membrane significantly increased its permeability and selectivity. The permeability of the composite membrane for CO₂ gas was 5.91 GPU, more than twice that of the pure polyetherimide membrane. Additionally, the permeability for CH₄ gas was 0.31 GPU, representing a significant improvement over the pure membrane''''s permeability of 0.17 GPU. The carbon dioxide/methane selectivity also rose from 15.3 in the pure membrane to 19.1 in the composite membrane. In conclusion, the study demonstrated that adding ZIF-8 to a polyetherimide matrix can improve the effectiveness of the resulting composite membrane for separating CO₂ from CH₄. The improvement in selectivity was primarily due to the increased solubility coefficient of carbon dioxide compared to methane in the composite membrane.