Preparation of Highly Hydrophobic PVDF-HFP Membrane with Anti-Wettability Characteristic

Membrane gas-liquid separation technology has gained great interest in membrane desalination, distillation, and gas absorption attributed to its good operation flexibility, small footprint and high specific interfacial area. Membrane acts as the non-selective barrier between gas and liquid solvent by allowing the diffusion of gas molecules via pressure difference. Currently used membrane is susceptible to pore wetting at high operational pressure, transforming its non-wetted condition to partially wetted and wetted mode. Such condition introduces additional mass transfer resistance to gas molecules, leading to the poor removal flux. In order to alleviate the wetting tendency, membrane hydrophobicity needs to be enhanced. In this work, highly hydrophobic PVDF-HFP membrane of improved anti-wettability properties was synthesized via non-solvent induced phase separation. The effect of polymer concentration and coagulation medium on membrane wettability were studied. The results revealed that PVDF-HFP membrane of 10wt% polymer concentration presented high water contact angle of 100.4 degrees. By changing water to ethanol as coagulation medium, membrane exhibited a symmetric nodular structure which enhanced water contact angle by 20.3% to 130.5 degrees. To further improve membrane hydrophobicity, modified silica (MS) nanoparticles were used as surface modifier in coagulation bath. When the nanoparticles content increased from 0g to 2g, the water contact angle of the PVDF-HFP modified membrane increased significantly from 130.5 degrees to 163.1 degrees. As a result, the liquid entry pressure of the membranes increased gradually from 0.58bar to 3.38bar with MS incorporation. This disparity in membrane anti-wettability is due to the increase in surface roughness and reduction in surface energy. Additionally, the modified membrane at MS loading of 2g showed high porosity at 78%, which is adequate to provide increased mass transfer rate between gas and liquid solvent.