All-Polymer and Self-Roughened Superhydrophobic PVDF Fibrous Membranes for Stably Concentrating Seawater by Membrane Distillation

Abstract

Novel specially wettable membranes have been attracting significant attention for durable membrane distillation (MD). However, constructing a superhydrophobic interface often has to undergo complex modification procedures including roughness construction and hydrophobic modification. Herein, all-polymer and self-roughened superhydrophobic poly­(vinylidene fluoride) fibrous membranes (PVDF FMs) with robustly stable pores were successfully constructed via electrospinning of fluorinated polyhedral oligomeric silsesquioxanes/PVDF (F-POSS/PVDF) emulsion solution in combination with hot-pressing. The comparative experiment reveals that proper hot-pressing, including adequate temperature and pressure, can help improve membrane pore stability by welding the intersecting fibers and increase the membrane surface hydrophobicity by transferring the inner fluorine chains to the outer fiber surface, simultaneously advancing membrane scaling and fouling resistance. Nevertheless, excessive temperature or pressure will destroy the interconnected pores and surface wettability of the PVDF FM. Significantly, the hot-pressing-treated F-POSS/PVDF FM shows a high water recovery (∼90%) and robust stability after five rounds of the concentration process toward concentrating natural seawater as a target. Thus, the all-polymer and self-roughened superhydrophobic PVDF FMs constructed via electrospinning combined with the thermal treatment have potential applications in concentrating hypersaline brines, which make up for the other membrane technology, including reverse osmosis and nanofiltration technologies that failed to concentrate hypersaline solutions.

Tuning the Functionalization of Graphite for Hydrovoltaic Power Generation

“…To counteract this, a hydrophobic material, PVDF was added to the FG6 and SDS prior to sonication. PVDF could then act as a blocker, preventing water flow through certain porous areas of the FG films and slowing the overall capillary flow of water. − By incorporating PVDF in the device fabrication, a stable OCP could be sustained without detrimental device saturation (Figure S9). Surface characterization before and after the addition of PVDF can be seen in Figure S13.…”

Interlayered Interface of a Thin Film Composite Janus Membrane for Sieving Volatile Substances in Membrane Distillation

“…The fluorinated polyhedral oligomeric silsesquioxanes (F-POSS) was first synthesized according to previous work. , The detailed synthesis procedures can be seen in the Supporting Information. To prepare F-POSS/PVDF-HFP solution, 0.90 g of F-POSS and 6.00 g of PVDF-HFP powders were dissolved in a mixed DMAc/acetone (23.80 g/10.20 g) solution with vigorous stirring at 80 °C for 6 h. To prepare SiO 2 /PAN solution, 0.048 g of SiO 2 powder was first dispersed in 19.20 g of DMAc solution and sonicated at 200 W for 30 min.…”

Electrospun Nanofibrous Membranes: A Versatile Medium for Waterproof and Breathable Application

“…[59] Constructing a rough surface to enhance the hydrophobicity is one method to enhance the waterproofness of PVDF membranes. [60,61] Hu et al, inspired by the micro/nanostructures of lotus leaves, constructed a structured electrospun membrane with adjustable microbeads by regulating the spinning voltage, the feed speed, the polymer solution concentration, and the conductivity of the solution. [57] Benefiting from the micronanoscale rough structure, the obtained PVDF nanofibrous membranes achieved impressive WVTR of >17.5 kg m −2 d −1 , good air permeability >5 mL s −1 , and high hydrostatic pressure of 623 mbar.…”