Dual-Bioinspired Design for Constructing Membranes with Superhydrophobicity for Direct Contact Membrane Distillation

Abstract

Water flux and durability are the two critical parameters that are closely associated with the practical application of membrane distillation (MD). Herein, we report a facile approach to fabricate superhydrophobic polyimide nanofibrous membranes (PI NFMs) with hierarchical structures, interconnected pores, and high porosity, which was derived from the electrospinning, dual-bioinspired design, and fluorination processes. Bioinspired adhesive based on polydopamine /polyethylenimine (PDA/PEI) composite was first linked onto membrane substrates and then assembled lotus leaf hierarchical structure by binding the negatively charged silica nanoparticles (SiO NPs) via electrostatic attraction. The resultant superhydrophobic PI NFMs exhibit a water contact angle of 152°, robust hot water resistance of 85 °C, and high water entry pressure of 42 kPa. Moreover, the membrane with omniphobicity presents high water flux over 31 L m h and high salts rejection of ∼100% as well as robust durability for treating high salinity wastewater containing typical low surface tension and dissolved contaminants (Δ T = 40 °C). Significantly, the novel dual-bioinspired method can be used as a universal tool to modify various materials with hierarchical structures, which is expected to provide more effective alternative membranes for MD and even for other selective wetting separation fields.

Superhydrophobic Bilayer Coating Based on Annealed Electrospun Ultrathin Poly(ε-caprolactone) Fibers and Electrosprayed Nanostructured Silica Microparticles for Easy Emptying Packaging Applications

“…Thus, for an electrospinning deposition time of 10 min, the apparent contact angle value reached a value of 98.8 • and thus, was clearly not superhydrophobic. The use of longer electrospun PCL deposition times further increased the apparent water contact angle values, perhaps due to the presence of more fibrous structures, leading to enhanced roughness and a reduction in porosity [31] and showing values above 130 • . However, as explained above, only 120 min of PCL deposition generated the required morphology to achieve superhydrophobicity.…”

“…Additionally, PCL has an inherently low surface energy due to its chemical structure, so its hydrophobic fibers may also prevent water droplets from penetrating into the valleys between the ultrathin fibers and microparticles, which could help to further enhance the surface hydrophobicity [5,6]. In terms of previous works that have described hydrophobic surfaces prepared by EHDP with the additional incorporation of SiO 2 particles, Zhu et al [31] reported an apparent water contact angle of 152 • for a membrane consisting of SiO 2 nanoparticles bonded to an electrospun polyimide (PI) membrane by electrostatic attraction. Similarly, Su et al [16] successfully created highly porous membranes with superhydrophobic structures via simultaneous electrospraying of SiO 2 /dimethylacetamide (DMAc) colloids and electrospinning of poly(vinylidene fluoride) (PVDF)/DMAc solutions, which exhibited a water contact angle of 163 • .…”

Waterproof and Breathable Electrospun Nanofibrous Membranes

“…In comparison to organic nanoparticles, SiO 2 nanoparticles have some unique advantages including good thermal stability, tunable particle size, good corrosion resistance, etc . Therefore, incorporating hydrophobic SiO 2 nanoparticles into electrospun nanofibers has become a common route to construct stable hydrophobic layer for nanofibrous membranes .…”

Nitrogen doped hierarchically structured porous carbon fibers with an ultrahigh specific surface area for removal of organic dyes

“…26,27 Electrospinning, a facile and powerful technique, provides a straightforward and inexpensive fabrication strategy for organic, inorganic or composite ber preparation. [28][29][30][31] The electrospun products have features such as a three-dimensional open porous structure, high surface area and huge aspect ratio, which would be benecial to mass transfer for effective wastewater treatment. However, it is still challenging to construct hierarchical porous carbon bers with an ultrahigh SSA for effective wastewater treatment.…”