Fabrication and characterization of highly hydrophobic PVDF membrane by phase inversion method with high anti-wettability characteristics

Abstract

Membrane gas-liquid separation technology has garnered significant attention in applications such as membrane desalination, distillation, and gas absorption due to its operational flexibility, compact design, and large specific interfacial area. However, the currently used membranes are prone to pore wetting under high operational pressures, transitioning from a non-wetted state to partially or fully wetted conditions. This undesired wetting increases mass transfer resistance for water vapor molecules, ultimately leading to reduced removal efficiency. To address this issue and enhance wetting resistance, membrane hydrophobicity needs to be improved. In this study, a highly hydrophobic polyvinylidene fluoride (PVDF) membrane was developed using the phase inversion method for membrane distillation applications. We mixed a 16wt% polymer concentration with N-Methylpyrrolidone (NMP) as a solvent at 50°C for 24 hours. Subsequently, the polymer solution was cast and exposed to different non-solvents, namely water and methanol, to investigate their impact. Surface morphology and hydrophobic properties of the synthesized membranes were analyzed using Scanning Electron Microscope (SEM) and a Goniometer. Our findings indicate that the PVDF membrane fabricated with methanol as the non-solvent exhibited a significantly higher water contact angle of 126°, compared to 70° when deionized water was used as the non-solvent. This change from water to methanol as the non-solvent resulted in a more symmetrical membrane structure, enhancing the water contact angle from 70° to 126°. It is interesting to note that increase in the water contact angle increases the hydrophobicity of the PVDF membrane.