Claiming water from the atmosphere or fog harvesting could be a promising route to relieve the scarcity of fresh water. The unidirectional water transportation of a Janus membrane has indicated a potential way of efficient fog collection. In this study, a facile two-step electrospun protocol was established to patch hydrophobic PVDF domains on a hydrophilic PAN nanofibrous texture in a designer manner inspired by the heterogeneous back structure of a desert beetle. The tuned heterogeneous surface morphology and the vertically varied wettabilities of the prepared Janus membrane indicated a more significant fog collection rate (FCR) than the homogeneous PAN or PVDF membrane. Moreover, the optimized Janus membrane (10 min of PVDF spinning on PAN to reach a coverage of 44.3%) indicated a promising FCR at 88.5 mg/(min cm2), which was comparable with the highest reported FCR of a more complicated organic/inorganic Janus system. It is possible that the synergistic effect of the capillary force and the Laplace pressure determined the high FCR of the Janus membrane in this study. In addition, the prepared Janus membrane was used for an efficient oil–water phase separation contributed by the excellent unidirectional water transportation effect. The novel morphology design protocol provided new insights of the Janus membrane fabrication, which obviously evoked the potential of the Janus membrane for practical applications.
Membrane fouling is one of the difficult challenges that restrict the efficient application of membrane separation technology in oil/water separations. Hydrogel with strong hydration capability has been considered as an ideal material for preparing anti-oil-fouling coating for membranes. Although some hydrogel-based coatings have been developed for the membrane interface hydrophilization modification, controlling the morphology of gel layers and improving the flux of hydrogel coated membranes remains a difficult matter to resolve. In this study, we elegantly designed a new mineral-hydrogel coating with nanostructures to modify hydrophobic polyvinylidene fluoride (PVDF) microfiltration membranes by an alternate quaternary soaking strategy. Compared with the merely hydrogel-coated membrane, the pure water flux of novel mineral-hydrogel coating membrane increased by 214% and the permeation increased by 127% with the oil rejection rate of 99.6% at 0.4 bar. Most importantly, the newly-built mineral-hydrogel layer on porous support possessed excellent hydrophilicity, underwater super-oleophobic properties and superior anti-oil-fouling performance, which is greatly promising in oily sewage remediation. In addition, this mineral-hydrogel coating could also be constructed on other hydrophobic substrates successfully, such as commercial melamine resin. Our facile strategy for designing and constructing synergetic mineral-hydrogel architecture may also inspire other functional coatings with nanostructures.
危险品化学品经营许可证（带存储）