Electrospun polyvinylidene fluoride/fluorinated acrylate copolymer tree-like nanofiber membrane with high flux and salt rejection ratio for direct contact membrane distillation

Abstract

A hierarchical tree-like nanofiber membrane (TLNM) with high hydrophobicity was prepared via electrospinning polyvinylidene fluoride (PVDF) blended with tetrabutylammonium chloride (TBAC) and fluorinated acrylate copolymer (FA). Then, the hydrophobicity of PVDF/TBAC/FA TLNMs was further enhanced after ultrasonic treatment. The introduction of TBAC and FA promoted the formation of tree-like structures and the as-prepared PVDF/TBAC/FA TLNMs showed strong hydrophobicity with a water contact angle of 137 ± 3°, extremely small pore size of 0.21–0.26 μm, outstanding mechanical strength of 7.90 MPa and high liquid entry pressure of 0.23 MPa, making the membrane possess excellent performance in the direct contact membrane distillation (DCMD) process. The PVDF/TBAC/3% FA TLNMs with a thickness of 60 ± 3 μm showed a superior permeate flux of 54.39 L/m2 h and the salt rejection rate kept above 99.5% after 9 h using a 3.5 wt% NaCl as the feed solution while with the feed and permeate temperatures were set as 60 °C and 20 °C, respectively. This work highlights the promising application of this TLNMs in the field of membrane distillation.