Department of Chemical Engineering, Gachsaran branch, Islamic Azad University, Gachsaran, I.R. IRAN
Polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride--chlorotrifluoroethylene) (PVDF-CTFE) hollow fiber membranes were fabricated via a wet phase-inversion method and the fabricated membranes were used for CO2 absorption with 1 M monoethanolamine solution in a gas-liquid membrane contactor system. Both types of hollow fiber membranes have a sponge-like structure close to the inner surface of the membrane and a finger-like structure close to the outer surface of the membrane but, the sponge-like structure of PVDF-CTFE membrane is thicker than PVDF membrane. The overall porosity of PVDF and PVDF-CTFE membranes were measured as 75.49 % and 69.51%, respectively. The critical Entry Pressure of water (CEPw) of PVDF-CTFE membrane is 9.5 bar and CEPw of PVDF membrane is 7 bar. The contact angle of water with PVDF-CTFE hollow fiber membrane surface is higher than PVDF membrane, which indicates higher hydrophobicity of this membrane. The maximum CO2 absorption flux of 7.20×10-3 (mol m-2 s-1) and 4.4×10-3 (mol m-2 s-1) at the liquid phase flow rate of 300 (ml min-1) was achieved for PVDF and PVDF-CTFE hollow fiber membranes, respectively. The results of the long-term CO2 absorption experiment showed that the CO2 absorption flux of PVDF membrane decreased by about 85% and reached 6.6×10-3 (mol m-2 s-1), 20 h after the beginning of the process. The CO2 absorption flux of PVDF-CTFE membrane decreased by about 15% and reached 8.8×10-3 (mol/m2.s), 70 h after the beginning of the process.