Surface Modification of PVDF-CTFE Hollow Fiber Membrane with Surface Modifying Macromolecules for Carbon Dioxide Absorption and Stripping

 Hydrophobic surface modifying macromolecules (SMM) have a main chain of polyurethane with two ends having a fluorine-based hydrophobic polymer. These macromolecules tend to migrate to the membrane surface during membrane fabrication process and alter the physical and chemical properties of the membrane surface by formation of a thin layer on the surface of the membrane. Therefore, they can increase the hydrophobicity of the membrane surface which is an important parameter in gas-liquid membrane contactor system.

Poly(vinylidene fluoride-co-chlorotrifluoroethlene), PVDF-CTFE, hollow fiber membranes were fabricated using surface modifying macromolecules through a dry-wet phase inversion method. Structure and characteristics of fabricated membranes were evaluated and they were used in carbon dioxide absorption and stripping processes in a gas-liquid membrane contactor system.

Water contact angle of outer surface of the fabricated membrane without SMM was measured as 90.51°. Addition of SMM into the membrane increased contact angle to 114.20°. Critical entry pressure of water of the membrane fabricated without/with SMM was measured as 7 and 10.50 bar, respectively. The CO2 absorption flux of 1.76×10-3 mol/m2.s and 9.70×10-4 mol/m2.s, at the liquid phase flow rate of 300 mL/min, was achieved for the fabricated membrane without/with SMM, respectively. The CO2 stripping flux, at the liquid flow rate of 200 mL/min, for the fabricated membrane was achieved at 1.30×10-3 mol/m2.s without SMM and 6.40×10-4 mol/m2.s with SMM. The maximum CO2 stripping efficiency, at the liquid flow rate of 200 mL/min, was achieved for the fabricated membrane at 72.10% without SMM and 42.60% with SMM.