Polyethylene terephthalate track etched membrane for recovery of helium from helium-nitrogen system

In this work, for the first time, the authors report polyethylene terephthalate (PET) track-etched membrane fabrication and detailed quantitative parametric studies for its application in He-N2 separation. The study also covers theoretical studies to understand the irradiation of PET film with ions as well as the contribution of gas flow domains, which is attempted for the first time. Monte Carlo simulations were carried out using the FLUKA code to evaluate the dose deposited by the ions in the PET film and the displacement per atom (DPA). The distribution of absorbed dose in the film as a function of thickness, the mean absorbed dose as a function of ion energy, and DPA at various depths in the film was determined using these simulations. The range of various ion beams was also calculated using the SRIM code. The effect of incident energy of irradiation beam (Si: 70 and 90 MeV and Cl: 84, 100 and 115 MeV) and etching parameters like concentration of NaOH, temperature, UV radiation, and ultrasonication on the control and irradiated polymer films (~25 µm thickness) were studied. Gas permeation studies of in-house synthesized track etched membrane (optimum) were carried out and a promising He/N2 selectivity of ~2.4 was achieved. The results confirmed that the membranes can have a potential application in the separation of He from natural gas.