| Summary: | The main objective in this research was to study the effect of air-gap length, one of the main spinning parameters, on the structure and carbon dioxide (CO2) absorption performance of hollow fiber membrane (HFM), while other spinning conditions were kept constant. Firstly, surface modified Polyvinylidene fluoride (PVDF) hollow fiber membranes were spun via dry-wet spinning method under different air-gap lengths (0-20 cm). Then the morphology of prepared membranes was evaluated by scanning electron microscopy (SEM). Also membranes structure was examined in terms of gas permeation, overall porosity, critical water entry pressure (CEPw) and contact angle. To determine the CO2 flux of HFMs, a system of gas-liquid membrane contactor was used. Experimental results of this study reveal that by increasing the air-gap distance from 0 to 20 cm, wetting resistance and contact angle of fabricated membranes increased due to enhancement of membrane surface hydrophobicity in higher air-gaps. Moreover, a decrease in average pore size of fabricated membranes was observed in higher air-gaps. The highest helium (He) permeation was achieved for the spun fiber at the air-gap of 10 cm. From CO2 absorption experiment it was found that the prepared membrane at the air-gap of 10 cm had the maximum CO2 flux of 1.57×10-3 mol/m2.s at the absorbent flow rate of 300 ml/min, which was significantly higher than CO2 flux of other PVDF membranes produced by other researchers. This significant increase in the CO2 flux could be related to its high effective surface porosity. Considering the high CO2 flux of this membrane, it can be concluded that in this study, the optimum air-gap distance was 10 cm to fabricate surface modified PVDF hollow fiber membranes using dry-wet spinning method. Lastly, it was found that applying an appropriate air-gap length for fabrication of surface modified hollow fiber membranes could be a promising method to improve CO2 removal in membrane contactor systems.
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