Effect of PVDF concentration on the morphology and performance of hollow fiber membrane employed as gas–liquid membrane contactor for CO2 absorption

Abstract

In this study, poly(vinylidene fluoride) (PVDF) hollow fiber membranes were fabricated and used in gas–liquid contacting process. Porous PVDF hollow fiber membranes were fabricated via thermal induced phase separation method. The polymer solution was formulated by varying polymer concentrations. The polymer concentration in dope solution varied from 25 to 34wt.% PVDF. Triacetin was used as solvent and internal coagulant while water as external coagulant. Measurement of membrane pore size, membrane porosity, liquid entry pressure of water (LEPw), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used for membrane characterization. The mean pore size, effective surface porosity and void fraction of membranes decreased as the polymer concentration increased, by contrast, LEPW and membrane density increased. Furthermore the performance of PVDF membrane in contactor applications in terms of CO2 absorption with 0.5M NaOH as absorbent liquid is compared with the absorption flux of commercial and in-house made hydrophobic membranes. Results showed that as polymer concentration in the dope solution increased, CO2 flux of membrane decreased. This means that outer skin layer of the membranes became apparently thicker and denser with increasing polymer concentration. Additionally, a mathematical model describing the non-wetted gas–liquid membrane contactors were solved using COMSOL software. Comparisons of model predictions with experimental data were in good agreement.