Preparation and characterization of PVDF-filled MWCNT hollow fiber mixed matrix membranes for gas absorption by Al2O3 nanofluid absorbent via gas–liquid membrane contactor

Abstract

Porous polyvinylidene fluoride (PVDF)-filled MWCNT hollow fiber mixed matrix membranes were fabricated and applied for carbon dioxide absorption in a gas–liquid membrane contactor with Al2O3 water-based nanofluid absorbent. The formation of MWCNTs’ nanotubes was verified through Transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FESEM) images while the resultant membranes were characterized for their morphology, gas permeation rate, pore size, porosity, surface hydrophilicity and wettability resistance. Upon the incorporation of MWCNT into the matrix, the formation of finger-like pores was facilitated and surface roughness increased. Gas permeation test results showed increasing the surface porosity and reducing the pore size. The surface contact angle also was improved from 83°±1.5 for the unfilled membrane to 103°±1.5 for the membrane containing 5wt% CNT. CO2 absorption flux also was enhanced considerably. For instance, the flux of the membrane containing 5wt% CNT as the best performing membrane at a liquid velocity of 2.5m/s and Al2O3 water-based nanofluid as absorbent was 3.85×10−3mol/m2s which was approximately 200% higher than that of the plain membrane at the same operating conditions. A long-term absorption test also revealed non-wetting tendencies of the membranes as well as the unclogged membrane pores by the nanomaterials existed in the nanofluid absorbent. Therefore, it could be hypothesized that the improved membrane structure and synthesized nanofluid absorbent considering their superior performance to several commercial and in-house made membranes can be suitable alternatives to the current polymeric membranes and commercial used absorbents, respectively.