Enhanced desalination performance of aluminium fumarate MOF-incorporated electrospun nanofiber membrane with bead-on-string structure for membrane distillation

Abstract

Although electrospun nanofiber membranes (ENMs) are attractive for membrane distillation (MD), the desalination performance needs further improvement for practical applications. In this work, aluminium fumarate (AlFu) metal organic frameworks (MOFs) were incorporated into polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) nanofiber membranes via electrospinning to obtain substantial performance improvement. The results showed that the fluxes of the composite ENMs were increased by 60% and 114% when adding 0.1 and 2 wt% of AlFu MOF, respectively, compared to the pristine PVDF-HFP ENM. The systematic characterization proved that, the mean pore sizes of the composite ENMs were enlarged due to the unique bead-on-string structures, which was the key factor for flux enhancement demonstrated by theoretical calculation. The improved thermal efficiency in DCMD process due to the low thermal-conductivity of AlFu MOF also helps to increase permeate flux. Other factors such as increased surface roughness and additional nanochannels for water vapors were also considered helpful in flux enhancement. The optimum membrane (2 wt% AlFu MOF) showed stable desalination performance during a 46-h DCMD test using seawater as feed, demonstrating the durability and robustness of the composite ENMs. The present study confirms the positive role of MOFs for performance enhancement of ENMs in DCMD application, showing great potential in seawater desalination.