We report a robust and continuous oil/water separation with nanostructured glass microfiber (GMF) membranes modified by oxygen plasma treatment and self-assembled monolayer coating with vertical polymerization. The modified GMF membrane had a nanostructured surface and showed excellent superhydrophobicity. With an appropriate membrane thickness, a high water intrusion pressure (< 62.7 kPa) was achieved for continuous pressure-driven separation of oil/water mixtures with high flux (< 4418 L h−1 m−2) and high oil purity (> 99%). Under simulated industrial conditions, the modified GMF membrane exhibited robust chemical stability against strong acidic/alkaline solutions and corrosive environments. The proposed superhydrophobic composite coating technique is simple, low cost, environmentally friendly, and suitable for the mass production of scalable three-dimensional surfaces. Moreover, its stability and customizable functionality offers considerable potential for a wide range of novel applications.
The adherence of underwater air bubbles
to surfaces is a serious
cause of malfunction in applications such as microfluidics, transport,
and space devices. However, realizing spontaneous and additional unpowered
transport of underwater air bubbles inside tubes remains challenging.
Although superhydrophilic polydimethylsiloxane (PDMS) tubes are attracting
attention as air bubble repellents, superhydrophilic PDMS, which is
fabricated via oxygen plasma treatment, has a disadvantage in that
it is weak against aging. Here, we present a tube with the ability
to self-remove air bubbles, which overcomes the drawback of rapid
aging. PDMS containing Silwet L-77 with a hierarchical nano–microstructure
exhibiting subaqueous aerophobicity was fabricated. We conducted adherence
and saturation experiments of air bubbles using the fabricated PDMS
tube with Silwet L-77 to investigate the mechanism of bubbles adhering
to and separating from the fabricated tube surface. The developed
PDMS with Silwet L-77 exhibits a strong self-removal effect with an
air bubble removal of 97.7%. The adherence and saturation experiments
suggest that the transparent superhydrophilic–underwater aerophobic
PDMS is a potentially exceptional tool for spontaneously separating
air bubbles attached to tube surfaces.
The chemical industry needs filter systems with selective wetting properties for environmental protection and effective liquid separation. Current liquid-separation systems are mainly based on the surface energy of the meshes used to separate liquid particles; the smaller the difference between the surface tension of the liquids to be separated, the lower the separation efficiency of these systems. Sophisticated control of the surface wettability of a separation system is necessary to separate liquids with small differences in their surface tension. We precisely adjusted the surface-energy threshold of aluminium meshes used for separation by simply coating their hierarchical microcube and nanohole structures with different materials. We also applied patterning technology to create a single mesh with a heterogeneous distribution of surface tension to successively separate four liquids. Under the force of gravity, the hybrid system of meshes effectively separated the mixture of four liquids, yielding a perfect collection rate (≥98%) and high content ratio (≥96%). Even multiphase mixtures of immiscible liquids with surface tension differences as small as 10.4 mN/m could be effectively separated. Thus, multiphase liquid-separation systems can be used for the efficient and economical separation of various liquid mixtures in many industrial and environmental fields.
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