Effect of operating conditions on the physical and chemical CO2 absorption through the PVDF hollow fiber membrane contactor

Porous polyvinylidene fluoride (PVDF) hollow fiber membranes were fabricated via a wet phase-inversion process and used in the gas–liquid membrane contactor for physical and chemical CO2 absorption. Effect of different operating parameters such as absorbent temperature, CO2 pressure, absorbent flow rate and long-term operation on the CO2 flux of the membrane were investigated. The characterization results showed that the prepared membrane possess small pore size with high surface porosity and wetting resistance, which are favorable for gas absorption application. Results of CO2 absorption experiments revealed that in case of physical absorption with distilled water, CO2 solubility was the key parameter which significantly affected the membrane CO2 flux. A significant increase in the CO2 flux was observed by increasing CO2 pressure and decreasing the absorbent temperature. However, in case of chemical absorption with NaOH (1 M), the reaction rate was dominant, where the CO2 flux was significantly increased by increasing the absorbent temperature. It was also found that when the liquid contacted the outer skin layer of the hollow fiber membrane, the operation was stable at the same gas and liquid pressure without bubble formation in the liquid phase. In addition, the results of long-term study demonstrated that the membrane performance was maintained constant for long-term operation. The initial flux reduction was found to be about 30% within the 23 h of physical absorption, and 20% of gradual reduction within 80 h of chemical absorption.