Improvement of CO₂/CH₄ separation characteristics of polyethersulfone by modifying with polydimethylsiloxane and nano-silica

Porous asymmetric polyethersulfone (PES) hollow fiber membrane was fabricated via dry/wet spinning process. The spinning dope consisted of 18 wt.% PES in N-methyl-2-pyrrolidone (NMP) solvent. Distilled water was used as bore fluid to make hollow fiber membrane without inner skin layers. Then, a skin layer consisting of poly (4-vinyl pyridine), PVP, silicon rubber PDMS and silica nanoparticles (nano-SiO₂) was transferred to the PES substrate surface by means of a dip coating method, leading to a nanocomposite hollow fiber membrane. Investigation of the cross-section of the prepared membranes via scanning electronic microscopy (SEM) revealed a good adhesion between the top dense layer and the PES substrate. Moreover, tensile strength and ultimate elongation of the pristine membrane were increased 2.3 and 5 times, respectively, when the PVP/PDMS/nano-SiO₂ coating was formed on its outer surface. Finally, according to the results of gas permeation tests, the prepared nanocomposite membrane, with a CO₂/CH₄ selectivity of 45 and CO₂ permeance of 102 GPU would be an attractive candidate for applications such as natural gas purification and control of anthropogenic carbon dioxide emissions.