Thermal treatment enhanced the hydrophobicity of PVDF hollow fibers membrane for brine treatment using membrane distillation

The objective of this research was to explore the impact of thermal treatment on the characteristics and performance of Poly (vinylidene fluoride) (PVDF) hollow fiber (HF) membranes utilized in direct contact membrane distillation (DCMD). To assess the effects of thermal treatment, the PVDF polymer's allotropy and crystallinity were analyzed using Fourier transform infrared ATR-FTIR and Differential scanning calorimetry (DSC). The thermal treatment predominantly affected the alpha-phase of the membrane, leading to increased hydrophobicity. On the other hand, Atomic Force Microscopy (AFM) characterized the membrane surface morphology. The AFM characterization revealed an increment in surface membrane roughness leading to an improvement in membrane hydrophobicity. This straightforward technique of thermal treatment resulted in improved membrane properties for DCMD application, such as increased LEP, porosity, and hydrophobicity, as well as reduced water uptake. The DCMD's efficacy was then evaluated using seawater reverse osmosis (SWRO) brine and it was observed that thermal treatment improved flux while slightly reducing salt rejection. In conclusion, these findings display the potential of thermal treatment to enhance the performance of PVDF HF membranes for DCMD applications.