Novel three-dimensional superhydrophobic and strength-enhanced electrospun membranes for long-term membrane distillation

The practical applications of membrane distillation (MD) are hindered by the absence of effective membranes with high porosity, sufficient strength, and durable wetting repellency for long term operation. In this study, we developed a facile method to construct composite membranes with high MD performance via one-step electrospinning of PVDF solutions blended with hydrophobic silica nanoparticles (NPs). The characterizations reveal that the incorporation of silica NPs have altered the membrane surface morphology and endowed the composite membrane with hierarchical structure on both surface and bulk layers (three-dimensional (3D) superhydrophobic membrane). The hydrophobicity of the membranes can be easily tailored by the dosage of silica NPs, and the water contact angle (WCA) of the membranes can be optimized to be 157 ± 1°, which was close to that of the lotus leaf (160°). Furthermore, the incorporation of silica NPs have promoted the mechanical strength, salt rejection, and water permeation flux of the membranes. The composite membrane containing 7.47 wt% silica NPs (designated as SIL40) can achieve a high MD performance with a water flux of 25.73 kg m −2 h −1 and a permeate conductivity below 5.0 μS cm −1 during a 100 h test-period. The SIL40 also shows a tensile strength and a Young’s modulus of 3.18 and 12.8 MPa, respectively; the values surpassed those of the pristine PVDF membrane (1.5 and 5.4 MPa, respectively). In addition, the MD test indicates that the 3D superhydrophobic membrane exhibits a more durable wetting resistance and a more stable MD performance than the surface-modified superhydrophobic membranes.