Smart Nylon Membranes with pH‐Responsive Wettability: High‐Efficiency Separation on Demand for Various Oil/Water Mixtures and Surfactant‐Stabilized Emulsions

Abstract

and costly device, as well as the inability to separate efficiently various emulsions including oil-in-water and water-in-oil types.Taking all strategies into account, membrane separation technique governed by interfacial phenomena is regarded as an ideal candidate due to the advantages of method simplicity, low cost, and high efficiency. [13][14][15][16] Since the idea of taking special wettability into membrane separation technique was proposed, [13] superwetting materials have aroused considerable interest in either immiscible oil/water separation or emulsified oil/water ones. Numerous superwetting materials have been realized in terms of the synergistic effect of chemical composition and hierarchical structures on the surface in last decades. Nevertheless, the surfaces of accustomed superwetting materials have constant water wettability of superhydrophilicity or superhydrophobicity, which are classified into "water-removing" materials or "oil-removing" materials aiming to separate single type of oil/ water mixtures. [17][18][19][20] The rigid wettability for nonswitchable separation type cannot adapt to the multicomponent immiscible oil/water mixtures involved different density of oils, not to mention the disposal of oil-in-water or water-in-oil emulsions in the actual processing situation. Hence, it is expected that smart materials with tunable wettability in response to external stimuli are promising for application of multitype oil/water separation, which requires simpler separation equipment and lower energy consumption than monofunctional separation materials.Driven by the actual processing demand for oily sewage treatment, impressive progress has been made in the field of smart materials that show switchable and reversible wettability in response to external stimulus, such as electric field, [21,22] light irradiation, [23][24][25] temperature, [26,27] counterions, [28,29] pH value, [30][31][32] or multistimuli. [33,34] For instance, Kung et al. demonstrated an approach for fast and reversible control over the wettability of electrodeposited copper meshes by electrochemical manipulating of the oxidation state of the copper oxide shell phase, achieving the controllable separation of immiscible oil/water mixtures in either oil removal or water-removal mode. [21] Kwon et al. prepared dye-sensitized nanoporous TiO 2 surfaces via dip-coating method to change selectively the wettability toward contacting liquids upon visible light illumination, revealing promise of new light-driven oil-water cleanup and demulsification technology. [23] Our Water contaminated with various oils has become one of the most pervasive environmental issues. Developing an efficient and durable separation membrane is of significance but challenging due to the critical limitations of nonuniversality and discontinuity for oil/water separation. Herein, a material is presented by combining the porous nylon membrane with self-assembled thiol molecules, exhibiting tunable wettability property upon the pH variation. Such a smart membrane show...

Smart Bionic Surfaces with Switchable Wettability and Applications

“…9c) [99] . For example, combined the porous nylon membrane with self-assembled thiol molecules, Li et al fabricated a smart membrane with tunable wettability property upon the pH variation, effectively separating various oil/water mixtures and surfactant-stabilized emulsions with excellent recyclability of the long-term separation [104] . Similarly, through the grafting of HS(CH 2 ) 11 CH 3 and HS(CH 2 ) 10 COOH, Liu et al fabricated pH-responsive super-wettable surfaces on the metal substrate, such as copper foams, aluminum alloy and copper alloy [105][106][107] .…”

High-Flux pH-Responsive Ultrafiltration Membrane for Efficient Nanoparticle Fractionation

“…Moreover, the pH-responsive membranes attracted more attention than the other stimuli-responsive membranes because pH adjustment is a routine procedure of water and wastewater treatments , and the pH-responsive membrane could be facilely setup in a conventional membrane filtration system . In general, the pH-responsive membranes could be prepared by blending the pH-responsive polymer with the bulk polymer followed with a phase inversion process; , in addition, post treatments such as grafting the pH-responsive brushes , and coating the pH-responsive materials , on the supporting membrane were adopted in the pH-responsive membrane preparation. Nevertheless, the membrane modified by blending or post treatment was usually suffering from the wide pore size distribution but narrow pore size adjustable range …”

A Fluoride‐Free and Super‐Wetting Functionalized‐Material with pH‐Responsiveness for Controllable Separation of Multiphase Oil/Water Mixtures

“…[32,33] Previous studies have displayed that weak polybase and polyacid, such as dimethylaminoethyl methacrylate (DMAEMA), 2-vinylpyridine (VPy), methacrylic acid (MAA), and other constituents containing amine or carboxyl groups, can rapidly protonate and deprotonate at various pH additions. [34,35] They are endowed with priority to achieve pH-triggered switchable wettability surface. According to this attractive advantage, it can successfully separate oil/water mixtures with different requirements via controllable adjustment.…”