Blend polyvinylidene fluoride/surface modifying macromolecule hollow fiber membrane contactors for CO2 absorption

• Blending SMM resulted in higher hydrophobicity and gas permeability.
• The modified membrane showed higher wetting resistance at 24 cm air gap.
• The membrane showed less mass transfer resistance by removing inner skin.
• Increasing air gap and SMM concentration resulted in higher CO2 flux.
• A long-term stable operation was achieved by developing PVDF membranes.

Recently, membrane contactors have attracted attentions as an efficient and flexible technology for CO2 capture. In the present work, blend hydrophobic polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared via a dry–wet phase-inversion process. Surface modifying macromolecule (SMM) was introduced to improve the membrane properties for CO2 absorption in gas–liquid membrane contactors. The effect of SMM concentration in the polymer dope, air gap distance and bore fluid composition on the structure and performance of the membranes were investigated. By increasing SMM in the polymer dope, the membranes presented smaller mean pore sizes, higher permeability and surface hydrophobicity. Using 2 wt.% SMM, the membranes prepared at 24 cm air gap showed larger mean pore size, higher hydrophobicity and lower permeability compared to those prepared at 0 cm air gap. By using 60 wt.% DMAc aqueous solution as the bore fluid, the membrane permeability and CO2 flux significantly improved. Maximum CO2 absorption flux of 6.8 × 10−4 mol/m2 s was achieved at absorbent velocity of 0.025 m/s. The surface modified membrane demonstrated about 10% gradual CO2 flux reduction for over 140 h of the long-term operation. In conclusion, by improving surface hydrophobicity of the membrane, a long-term stable operation can be achieved for practical implication of gas–liquid membrane contactor technology.