Preparation and characterization of PDMS/zeolite 4A/PAN mixed matrix thin film composite membrane for CO2/N2 and CO2/CH4 separations

In this study, new thin film composite membranes were synthesized from polydimethylsiloxane/zeolite 4A (PDMS/zeolite 4A) as a mixed matrix thin selective layer coated on a polyacrylonitrile ultrafiltration membrane sublayer attached on a non-woven polyester fabric support in order to carry out CO2 removal. The scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry, atomic force microscopy, dynamic light scattering, Fourier transform infrared (FTIR) spectroscopy, and thermal gravimetric analysis were applied to evaluate the particle/membrane properties. The effect of zeolite loading (0-30 wt%), feed pressure (1-5 bar), and polymer concentration in coating solution (5-10 wt%) were investigated on the CO2, N-2, and CH4 permeations. SEM images of the composite membranes showed good adhesion and distribution in 15 wt% zeolite 4A. Furthermore, FTIR spectra of the composite membranes indicated that no chemical interaction exists between the particles and the polymer matrix. Gas permeation results showed that with the addition of zeolite particles into the polymer matrix, permeance of all gases increase compared to the pure PDMS membrane. The optimum performance, i.e. CO2 permeance of 3457 GPU and selectivity of 23.8 for CO2/N-2 and 8.2 for CO2/CH4, was achieved with a membrane composed of 15 wt% zeolite 4A loadings, 5 wt% polymer concentration in coating solution, and at a pressure of 3 bar.