Morphological, chemical and thermal stability of microporous LDPE hollow fiber membranes in contact with single and mixed amine based CO2 absorbents

Abstract

The gradual deterioration in the morphological and chemical stability of membranes in membrane contactors can extensively influence the membrane wettability, leading to reduction of CO2 absorption efficiency. In the present work, morphological, chemical and thermal stability of microporous low density polyethylene (LDPE) hollow fiber membranes, intended to be used in membrane contactors, was studied in contact with primary amine (monoethanolamine, MEA) and sterically hindered amine (2-amino-2-hydroxymethyl-1,3-propanediol, AHPD) solutions. The effect on membrane stabilization of a diamine (piperazine, PZ) having the operational advantages of fast CO2 absorption rate and capacity was also investigated.The surface properties of neat (before contact) and used (after contact with amine solutions) membranes were analyzed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and contact angle measurements. For membranes immersed in amine solutions of commonly used concentrations (30wt.% MEA and 11wt.% AHPD), the results show morphological degradation of membranes, caused by the intrusion of the solution into the pores, as well as chemical degradation caused by the LDPE auto-oxidation. However, a less significant effect was found by the addition of PZ. A two-step mechanism was proposed to explain the stabilizing effect of PZ. PZ containing amine solutions are suggested as strong candidates for CO2 absorption in membrane contactors due to their efficient dual-function properties (high CO2 absorption efficiency and polyolefin membrane stabilization).