Superhydrophobic modification of PVDF–SiO₂ electrospun nanofiber membranes for vacuum membrane distillation

Abstract

Electrospun nanofiber membranes having a hierarchical structure with multilevel roughness were generated via electrospinning of poly (vinylidene fluoride) (PVDF)-SiO 2 blend solutions.The composite PVDF-SiO 2 nanofiber membranes were then endowed with superhydrophobicity by the fluorosilanization of the surface with low surface energy fluoroalkylsilane (FAS). The results showed that when the SiO 2 content in the dope solutions increased from 0 wt% to 8 wt%, the water contact angles of the FAS modified nanofiber membranes increased significantly from 130.4° to 160.5°. The increment of the silica content in the dope solutions decreased the fiber diameters and pore sizes of the modified membranes, while the mechanical properties were enhanced with the silica addition. The liquid entry pressures of the membranes increased gradually from 84 kPa to 195 kPa with silica addition due to the increased contact angles and decreased pore size. Vacuum membrane distillation experiments were carried out for the modified nanofiber membranes to evaluate the anti-wetting properties. The optimal superhydrophobic nanofiber membrane maintained a stable flux of 31.5 kg/m 2 h with a permeate conductivity approximately 10 μs/cm over the entire test, while the fluxes and conductivities of the nanofiber membranes without superhydrophobicity showed a significant decrease and increase, respectively. The results indicated that the superhydrophobic modification process rendered the nanofiber membrane anti-wetting properties without compromising its excellent permeability.

A review of nanoparticle‐enhanced membrane distillation membranes: membrane synthesis and applications in water treatment

“…SiO 2 NPS were characterized by water‐hating methyl functional groups which subsequently improved the contact angles of the membranes from 139° to 154°. The water‐membrane contact angle and roughness observed in this study was similar to those shown by many other previous studies reporting a decrease in membrane wetting and an improvement on membrane fouling resistance . In addition to several studies reporting the use of SiO 2 NPs and TiO 2 NPs for enhancing membrane hydrophobicity, graphene and carbon nanotubes (CNTs) have also been observed to render MD membranes super‐hydrophobic .…”

“…The synthesis of super‐hydrophobic PVDF nanofibre membranes has been achieved by the incorporation of multi‐walled carbon nanotubes (MWCNTs), SiO 2 NPs, and TiO 2 NPs onto polymeric membranes (e.g. PVDF membranes) resulting in contact angles higher than 150° . Not only do these modified nanofibre membranes display high contact angles, they are also characterized by a mechanical strength high enough to sustain low pressures in MD .…”

“…PVDF membranes) resulting in contact angles higher than 150° . Not only do these modified nanofibre membranes display high contact angles, they are also characterized by a mechanical strength high enough to sustain low pressures in MD . These nanofibre membranes have been successfully used in the production of potable water at fluxes between 28 and 42 L m −2 h −1 and removal efficiencies of ∼99.9%.…”

Handspinning Enabled Highly Concentrated Carbon Nanotubes with Controlled Orientation in Nanofibers

“…ES produces a variety of polymer fibers or fiber sheets with diameters ranging from a few nanometers to several micrometers and that have a high surface area-to-volume ratio456. The polymer solution is ejected from the tip of an ES apparatus and forms a fiber structure due to static electrical forces during in-flight solvent evaporation, which leads to the nanofiber structure78.…”

Effect of different treatments and SiO2/PVDF coatings on morphology and wettability of electrospun polyamide 6 membranes

“…Spinning solution can mix polymers with hydrophobic nanoparticles to fabricate the roughness surface. Polyvinylidene fluoride (PVDF)‐SiO 2 blend solution was applied to electrospinning, and then the membrane was modified by (heptadecafluoro‐1,1,2,2‐tetradecyl) trimethoxysilane/hexane solution, which was endowed with water contact angle of 160.5° . Al 2 O 3 nanoparticles were added in the polystyrene solution to increase the surface roughness by Radwan et al .…”