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Enhanced flux in direct contact membrane distillation using superhydrophobic PVDF nanofibre membranes embedded with organically modified SiO<inf>2</inf> nanoparticles

Abstract:

BACKGOUND: Membrane distillation (MD) is a promising low-cost and efficient desalination process, yet it has not been fully implemented at an industrial scale. Membrane wetting and low porosity are limiting factors leading to low water recovery rates. The current study involved the synthesis of membranes that combined high mechanical stability, porosity and superhydrophobicity, to prevent wetting, with high salt rejection and water flux. RESULTS: Silica nanoparticles (SiO2NPs) were synthesized by a novel green chemistry procedure, modified with three different silane reagents [octadecyltrimethoxysilane, N-octadecyltrichlorosilane (ODTS) and chlorodimethyl-octadecyl silane] and finally embedded on polyvinylidene fluoride (PVDF) nanofibre membranes using an in-situ electrospinning technique. These modified membranes displayed a Young's modulus of ∼43 MPa and showed highly porous properties (∼80% porosity, 1.24–1.41 μm pore sizes) and superhydrophobic surfaces (contact angle >150o); thus possessing parameters falling within the range of highly recommended values in MD. Remarkably, the concentration of modified SiO2NPs used to produce the superhydrophobic PVDF nanofibre membranes was significantly lower (1% w/w) than those reported in the literature (3–4% w/w), clearly indicating the efficiency of these silane reagents. CONCLUSION: Membranes embedded with ODTS-modified SiO2NPs were the most efficient; rejecting salts at high efficiencies (>99.9%) with water fluxes of ≈34.2 LMH at 60 °C, thus indicating their capacity as an energy-efficient process to produce high purity water. © 2019 Society of Chemical Industry.