Synthesis and preparation of asymmetric PSf/ZIF-8 mixed matrix membrane for CO2/CH4 separation

Abstract

Utilizing nano-size filler into polymer matrix would overcome challenges in developing MMM by providing good dispersion in polymer matrix, high contact polymer-filler even at low filler loading. Asymmetric neat Polysulfone (PSf) and PSf/Zeolitic Imidazole Framework-8 (PSf/ZIF-8) mixed matrix membrane was prepared using dry/wet inversion method. Membrane prepared was coated with 3wt% of polydimethylsiloxane (PDMS) in n-hexane and undergoes heat treatment. The membranes was characterized using x-ray diffraction (XRD), thermagravimetric analysis (TGA), differential scanning calorimetry (DSC), and gas permeation test at 4 bar. XRD pattern revealed that ZIF-8 was successfully synthesis with crystal size around 73nm. Lowered membrane Tg after embodiment of ZIF-8 suggests that additional free volume form, while thermal stability up to 350°C related to ZIF-8 stability. Neat PSf prepared shows CO2 permeance at 4.97 GPU with CO2/CH4 selectivity at 7.52. Interestingly, incorporation of ZIF-8 showing improvement for both CO2 permeance and CO2/CH4 selectivity up to 51% and 47% respectively. Thus, employing nano ZIF-8 as filler into PSf matrix has resultant promising membrane for CO2/CH4 separation.