Hydrophobic PVDF/graphene hybrid membrane for CO2 absorption in membrane contactor

Graphene nanosheets were incorporated into polyvinylidene fluoride (PVDF) membrane in order to improve the membrane hydrophobicity. The hybrid membrane was prepared using the non-solvent induced phase separation method, and used in a membrane contactor for CO2 absorption. The incorporation of graphene induced the PVDF crystal transformation from γ-form to α-form, and resulted in a more open and loose sub-layer structure. The hydrophobicity of the hybrid membrane was enhanced compared to the pristine PVDF membrane. However, the increase in the contact angle values with the graphene concentration only occurred for the bottom surface (i.e., the surface of the substrate interface). The CO2 absorption performance with water as the absorption solution was dependent on the membrane orientation. When the bottom surface of high roughness faced the absorption solution, the hybrid membrane exhibited a faster CO2 transfer. Due to the improvement in the membrane hydrophobicity, the wetting problem was significantly mitigated, and a long term run with high CO2 absorption efficiency could be guaranteed. Our results demonstrated that the incorporation of graphene is a promising approach to obtain hydrophobic PVDF membrane for gas membrane absorption.