Underoil Superhydrophobicity Research Articles

High-Performance Membranes Based on Spherical-Beaded Nanofibers and Nanoarchitectured Networks for Water-in-Oil Emulsion Separation.

High-performance separation materials for oil-water emulsions are crucial to environmental protection and resource recovery; however, most existing fibrous separation materials are subject to large pore size and low porosity, resulting in limited separation performance. Herein, we create high-performance membranes consisting of spherical-beaded nanofibers and nanoarchitectured networks (nano-nets) using electrostatic spinning/netting technology, for water-in-oil emulsion separation. By manipulating the nonequilibrium stretching of jets, spherical-beaded nanofibers capable of generating a robust microelectric field are fabricated as scaffolds, on which charged droplets are induced to eject and phase separate to self-assemble nano-nets with small pores. Benefiting from 3D undulating networks with cavities originating from 2D nano-nets supported by 1D spherical-beaded nanofibers, the membranes exhibit under-oil superhydrophobicity (>152°), a striking separation performance with an efficiency of >99.2% and a flux of 5775 L m-2 h-1, together with wide pressure applicability, antifouling, and reusability. This work may open up new horizons in developing fibrous materials for separation and purification.

An Eco-Friendly Manner to Prepare Superwetting Melamine Sponges with Switchable Wettability for the Separation of Oil/Water Mixtures and Emulsions.

Oil/water separation processes have garnered significant global attention due to the quick growth in industrial development, recurring chemical leakages, and oil spills. Hence, there is a significant demand for the development of inexpensive superwetting materials in an eco-friendly manner to separate oil/water mixtures and emulsions. In this study, a superwetting melamine sponge (SMS) with switchable wettabilities was prepared by modifying melamine sponge (MS) with sodium dodecanoate. The as-prepared SMS exhibited superhydrophobicity, superoleophilicity, underwater superoleophobicity, and underoil superhydrophobicity. The SMS can be utilized in treating both light and heavy oil/water mixtures through the prewetting process. It demonstrated fast permeation fluxes (reaching 108,600 L m-2 h-1 for a light oil/water mixture and 147,700 L m-2 h-1 for a heavy oil/water mixture) and exhibited good separation efficiency (exceeding 99.56%). The compressed SMS was employed in separating surfactant-stabilized water-in-oil emulsions (SWOEs), as well as surfactant-stabilized oil-in-water emulsions (SOWEs), giving high permeation fluxes (reaching 7210 and 5054 L m-2 h-1, respectively). The oil purity for SWOEs' filtrates surpassed 99.98 wt% and the separation efficiencies of SOWEs exceeded 98.84%. Owing to their remarkable capability for separating oil/water mixtures and emulsions, eco-friendly fabrication method, and feasibility for large-scale production, our SMS has a promising potential for practical applications.

Controllable construction of the underwater superoleophobic surface from superhydrophilicity to superhydrophobicity in oil

Superwetting that is being subdivided to multiple superlyphobic states exists unique superiority in a specific interfacial application. Fine controlling superwetting surface is lack of systematic research. Due to the harsh conditions on the creation of underoil superhydrophilicity and suerhydrophobicity in oil of underwater superoleophobic surface, so far controllable fabrication strategies of the underwater superoleophobic surfaces in oil still remain a challenge. Herein, underwater superoleophobic surfaces from superhydrophilicity to superhydrophobicity in oil are controllable constructed by mixing commercial titanium dioxide nanoparticles, aluminum phosphate, and n-Alkyl acids, where the surface heterogeneous chemistry is finely controlled by changing the chain length of n-alkanoic acids. Under the rational surface energy, underoil superhydrophilicity and underoil superhydrophobicity of the underwater superoleophobic surfaces can be efficiently regulated via simply adjusting the chain length of n-alkanoic acids. The under-liquid dual superlyophobic surface can be achieved when an appropriate parameter denoted chain length of n-Alkyl acids (n) is between 14 and 16. However, when the parameter (n) is to be within 4 and 6, the superhydrophilicity in oil of underwater superoleophobic surface can be realized. This finding can connect the molecular-level conformational transformation and the conversion of macroscopic surface alternative wettability, providing the molecular-level design principle of superwetting interfacial in under-liquid environments.

3D‐Printed Robust Dual Superlyophobic Ti‐Based Porous Structure for Switchable Oil/Water Emulsion Separations

AbstractSmart surfaces with responsive wettability are unstable, and depend upon continuous external stimuli, which limits their widespread application in switchable oil/water emulsions separations. In this study, a Ti‐based 3D porous structure (SLM‐3DTi) is printed using advanced selective laser melting (SLM) technology for the switchable separation of oil/water emulsion. With the assistance of the computer program, porous structure and re‐entrant texture can be easily designed and printed in one step. Without any continuous external stimulus, the wettability of SLM‐3DTi can be reversibly switched between underwater superoleophobicity and underoil superhydrophobicity simply by drying and washing cycles. The SLM‐3DTi achieves switchable surfactant‐stabilized oil‐in‐water emulsion (SSE(o/w)) and surfactants‐stabilized water‐in‐oil emulsion (SSE(w/o)) separation with purity above 99.8% at a flux of more than 2000 L m−2 h−1. In addition, the re‐entrant texture of the SLM‐3DTi surface is formed with the partially melting powder particles on the part contour, which has much stronger mechanical durability than any binder. Furthermore, SLM‐3DTi has excellent corrosion resistance due to the material properties of Ti. More importantly, based on the visualization analysis of the simulation, the mechanism of SLM‐3DTi emulsion separation is further elucidated. Therefore, SLM‐3DTi has broad practical application potential for high‐flux, high‐purity, and switchable oil/water emulsion separation.

Green tubular micro/nano architecture constructed by in-situ planting of small AgNPs on Kapok fiber for oil spill recovery, smart oil–water separation and multifunctional applications

The ubiquitous existence of harmful contaminants in water is recognized as a major threat to aquatic ecosystems and human health, and renewable, economical, and superefficient new materials are needed to eliminate these dangers. Here, the ultrasmall silver nanoparticles (AgNPs) anchored Kapok fiber (KF) (KF/AgNPs) composite capable of efficiently separating various oil–water systems and eliminating other pollutants or bacteria was prepared by a green self-reducing reaction process using natural KF as the “microreactor” and water as the only solvent. The introduction of AgNPs endows KF/AgNPs with significantly improved liquid storage capacity, underwater superoleophobicity and underoil superhydrophobicity, so it shows excellent switchable oil–water separation capability. The oil–water separation efficiencies under gravity reached 99.90 % for the oil-in-water (O/W) emulsion (water flux: 1300 L·m−2·h−1), 99.91 % for the water-in-oil (W/O) emulsion (oil flux: 1500 L·m−2·h−1), and 99.80 % for the immiscible oil–water mixture (flux: 1900 L·m−2·h−1). In addition, KF/AgNPs composite can serve as absorbents to remove oil slicks from sewage (removal efficiency: 99.95 %; absorption capacity: 42.3 g/g) and adsorbents to rapidly remove microplastics in actual natural waters (concentration: 10 mg/L and can inhibit the growth of E. coli bacteria. After use, approximately 96.4 % of Ag was recovered from spent composite, and an excellent biochar adsorbent for the dye was obtained simultaneously.

Fabrication of raspberry-like starch-based polymer microspheres for W/O and O/W emulsions separation and purification

Oil/water separation and purification is an important pursuit because of uncontrolled emissions of industrial effluent, which has a catastrophic impact on our aquatic environment and body health. Here, an amino-functionalized composite particles material was developed via Pickering polymerization and grafting of poly(ethylene imine) (PEI). The wettability of the resultant composite particles can be easily regulated via changing the dosage of PEI. At lower dosage of PEI, the composite particles exhibited underoil superhydrophobicity (UOWCA: 158.8°) which applied to separate W/O emulsions with high flux (∼ 170 L/m2 h). At higher dosage of PEI, it converted to underwater superoleophobicity (UWOCA: 158.1°) and could efficiently realize the separation of O/W emulsions with high flux (∼ 160 L/m2 h bar). And at specific dosage range of PEI, the resultant composite particles can separate W/O and O/W emulsions simultaneously under the joint action of rough structures, unique surface wettability and positive charge. In addition, the resultant amino-functionalized composite particles were positive charged which could effectively absorb many anionic water-soluble pollutants with high removal rate of almost 90 % during oil/water separation process. This research may provide a new idea for intelligent oil/water separation and purification in the future.

A smart underoil“water diode”Janus TiO2 mesh membrane

Recently, Janus membranes with particular ability in unidirectional water permeation, known as “water diode”, have attracted increased attention. However, almost all existing Janus membranes are focused on controlling water permeation in air, similar membranes can work in complicated environments, such as oil, are still quite unusual, let alone with smart controllability. Herein, we report a TiO2 nanostructures coated mesh membrane. The membrane’s surface wettability can be reversibly switched between uniformly underoil superhydrophobicity and Janus underoil hydrophobicity/hydrophilicity as unilateral UV irradiation and heating are alternately carried out, consequently, on/off control of water permeation between blocking state and unidirectional penetrating state can be realized. Moreover, by controlling the size of the region irradiated by UV light for 50 min, penetrating channels with controlled size can be designed. Based on this advantage, different independent penetrating channels with diameter from 2 mm to 10 mm can be obtained, and precise control of water permeation flux from 48,432 Lm−2h−1 to 70,553 Lm−2h−1 can be achieved. Finally, based on the excellent controllability, some significant applications such as the removal of water from oil, underoil multichannel chemical reaction, and droplet pumping were also demonstrated. This work reports a new membrane with smart underoil water permeation controllability, given its controllability and particular wetting performance, it is potentially used in many fields, for example, oil purification, droplet manipulation, and microfluidic devices.

Customizing multiple superlyophobic surfaces in water-oil-air systems: From controllable preparation to smart switching via manipulating heterogeneous surface chemistry

Superlyophobicity that is being subdivided to multiple extreme wetting states has unique superiority in a specific interfacial application. Controllable preparation and smart switching of multiple superlyophobic surfaces are significant but remain a challenge. Here a flexible bilayer strategy is presented to construct three kinds of multiple superlyophobic surfaces with controllable extreme wetting behaviors of water and oil droplets in air while ultimately showing underoil superhydrophobicity and underwater superoleophobicity. A robust hydrophobic polyacrylate adhesive can be used expediently to adjust the heterogeneous surface chemistry resulting from extremely-low-surface-energy CF chain and water-loving TiO2 sol. Moreover, solvent-triggered process and ultraviolet irradiation enable smart switching among these fine superwetting states. Under the stimuli, the heterogeneous surface chemistry is further regulated by reconstruction of the bilayer components. Utilizing the superhydrophobic and underwater superoleophobic properties, the smart membrane realizes effective on-demand emulsion separation. This study provides an approach to customize smart surfaces with switchable superwettability among subdivided multiple superlyophobicity.

Controllable Fabrication of Durable, Underliquid Superlyophobic Surfaces Based on the Lyophilic-Lyophobic Balance.

Surfaces possessing desirable underliquid special wettability, particularly underliquid dual superlyophobicity, have a high potential for extensive applications. However, there is still a lack of controllable preparation strategies to regulate the underliquid wettability via balancing the underliquid lyophilicity-lyophobicity. Herein, we develop a nanocomposite coating system comprising silica nanoparticles (NPs), glycerol propoxylate triglycidyl ether (GPTE), and fluorinated alkyl silane (FAS) to obtain controllable underliquid special wettability surfaces. FAS is the vital factor in guiding the preparation of the surface coating with expected underliquid superwettability. Increasing the FAS content results in a tendency toward underwater superoleophobicity/underoil hydrophilicity to underwater oleophilicity/underoil superhydrophobicity. Significantly, the underliquid dual superlyophobic surface can be achieved when an appropriate FAS content is located. After the coating treatment, the fabric exhibits superamphiphilicity in air and superlyophobicity in liquid (i.e., exhibiting both underwater superoleophobicity and underoil superhydrophobicity). The coating also exhibits an adaptable antioil fouling ability and high durability against harsh environments. Furthermore, oil/water separation based on the underliquid dual superlyophobicity of coated fabrics is successfully demonstrated. Our work proposes a new fabrication principle for the design of underliquid special wettability surfaces and offers broad applications, such as switchable oil/water separation, antibiofouling, liquid manipulation, and smart textiles.

Antibacterial waterborne polyacrylate coated fabric with underwater superoleophobicity and underoil superhydrophobicity for continuous oil/water separation

Antibacterial superamphiphilic materials with green and facile preparation process have attracted extensive attention in oil/water separation. Herein, an antibacterial waterborne polyacrylate (AWBPA) composed of [2-(methacryloyloxy)-ethyl] trimethylammonium chloride (METAC) and basic acrylate monomers has been successfully developed using the emulsion polymerization method and water as the sole solvent. By sequentially simple dip-coating of polyethyleneimine (PEI) and AWBPA, the polyester fabric can be endowed with the superamphiphilic and antibacterial properties. By prewetting with water/oil, the modified fabric holds underwater superoleophobicity/underoil superhydrophobicity, and can be used for continuous separation of light oil/water, heavy oil/water and light oil/water/heavy oil mixtures. Importantly, these modified fabrics have high antibacterial activity (99.3 ± 0.2 %), and can maintain its underwater superoleophobicity and underoil superhydrophobicity even after immersion in corrosive solution for 15 d, 100 g sand impact and 200-cycle adhesive tape-peeling, and are suitable for practical large-scale production applications.

Waste to treasure: Superwetting foam enhanced by bamboo powder for sustainable on-demand oil-water separation

Low-cost and sustainable superwetting materials are urgently required for oily wastewater treatment. Many poly(vinylidene fluoride) (PVDF)-based materials have been designed for oil-water separation. However, their fabrication processes frequently require toxic organic solvents and high-cost materials (e.g., carbon tubes and graphene). In this study, a highly porous and superhydrophobic bamboo powders (BP)-enhanced PVDF foam (SBPF) was fabricated via an organic solvent-free process. The SBPF exhibits efficient adsorption and recovery for various oils and organic solvents. Moreover, the SBPF shows high adsorption and separation performance under ultraviolet exposure and turbulent environments. It can also be used for water-in-oil emulsions separation, with a high separation efficiency more than 99.3 % under gravity. Interestingly, the amphiphilic PVDF-BP foam (ABPF) shows underwater superoleophobicity and underoil superhydrophobicity after delignification of SBPF. Owing to the conversion of wettability, it presents a high performance in treatment of both surfactant-stabilied water-in-oil and oil-in-water emulsions with the high separation efficiency achieving more than 99.6 % and 99.5 % respectively under gravity. In addition, the ABPF shows a high separation performance even after ten cycles. Hence, this fabricated organic solvent-free foams are promising candidates for sustainable on-demand separation of oils or organic solvents and water in complex environments.

Design of a simple nanoscale hydrophilic-hydrophobic heterojunction system with under-liquid dual superlyophobicity for application in controllable droplet-based microreactor system and oil/water emulsions separation

Recently, many superwetting materials have emerged to deal with environmental problems. Among them, the under-liquid dual superlyophobic superwetting surface has attracted widespread attention due to the possessing of underwater superoleophobicity and underoil superhydrophobicity at the same time, and without the requirement of any energy stimulation when compared to conventional or responsive superwetting surfaces. However, A rational design of this deliciated surface state still lacking. Herein, a novel dual superlyophobic surface was achieved by simply modulating the relative proportion of a nanoscale hydrophilic-hydrophobic heterojunction system - cellulose nanofibrils (CNFs) and graphited multiwalled carbon nanotubes (gMWCNTs), and without any additional chemical modification. Besides, the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory or extended-DLVO (EDLVO) theory was introduced first to help understand the wettability variation of such a heterogeneous surface, which is mainly attributed to the changing stability of oil or water film covering the membrane surface. Additionally, this novel nanoscale hydrophilic-hydrophobic heterojunction system with dual superlyophobicity and excellent flexibility can not only separate both oil-in-water emulsion and water-in-oil emulsion simultaneously, but also achieve the lossless transfer in the droplet-based microreactor system under both water and oil environments. This may bring novel applications to the field of dual superlyophobicity. Moreover, this nanoscale hydrophilic-hydrophobic heterojunction system offers new and universal theoretical guidance for facile preparation of dual superlyophobic surfaces, owing to the richness in the functionality of low dimensional nanomaterials, it is foreseeable that more potential applications in various fields can be coupled with such an adaptable platform.

Robust preparation of braid-reinforced hollow fiber membrane covered by PVDF nanofibers and PVDF/SiO2 micro/nanospheres for highly efficient emulsion separation

The PVDF nanofibers and the PVDF/silica (SiO2) micro/nanospheres were deposited simultaneously on the outer surface of a rotating PVDF braided tube by electrospinning and electrospraying to fabricate a new type of enhanced hollow fiber membrane. By adjusting the content of SiO2 in electrospraying solution, the micro/nanospheres with different morphology were obtained to optimize the performance of the prepared membranes. When 2 wt% SiO2 was added, the deposited micro/nanospheres mainly took loose porous PVDF aggregates as the skeleton and SiO2 particles as the filler to construct the micro/nano structure on the membrane surface like that on the lotus leaf surface. Therefore, the membrane surface exhibited superoleophilicity (θo = 0°) and underoil superhydrophobicity (θuow = 154°). In addition, the deposited micro/nanospheres can effectively weakened the stacking between the deposited nanofibers. The resultant membrane not only had the high permeability with pure oil flux of 8557 L·m−2·h−1, but also possessed the excellent oil-water separation performance with separation efficiency of 99.70%. Meanwhile, it also showed the outstanding tensile strength of 79.40 MPa. The preparation method was simple and easy to operate, which would provide more possibilities for the preparation of hollow fiber membranes with efficient separation performance to the water-in-oil emulsion.

Smart Hierarchical Zeolitic Imidazolate Framework-Coated Stainless Steel Meshes with Switchable Wettability for Oil/Water Separation.

Selective filtration based on superwetting materials has brought about widespread attention in the field of oil/water separation. In this study, a ZIF-L@8-coated stainless steel mesh (ZIF-L@8-coated SSM) was prepared via in situ growth of two-dimensional leaf-shaped ZIF-L nanosheets on SSM, followed by heterogeneous epitaxial growth of ZIF-8 on a ZIF-L coating. The synthesized ZIF-L@8-coated SSM with a hierarchical micro/nanoscale structure exhibited outstanding switchable wettability between underwater superoleophobicity and underoil superhydrophobicity upon respective prewetting using water and oil without additional external stimuli. It possessed excellent separation performances and stabilities with respect to various types of oil/water mixtures. The switchable wettability mechanism was analyzed and elucidated in detail. The synthesized ZIF-L@8-coated SSM with switchable wettability in this study would have great potential in on-demand oil/water separation.

Nanostructured copper hydroxide-based interfaces for liquid/liquid and liquid/gas separations

Development of an under-liquid super-repellent (ULSR) surface that can act as a versatile platform for separating both liquid/liquid and liquid/gas mixtures is highly desirable, yet still hard to realize. Herein, to address this challenge, a Cu(OH)2 nanowire textured surface on copper mesh was developed through a simple immersion process. The resulting Cu(OH)2 nanowire surface displayed underwater superoleophobicity, underoil superhydrophobicity, and unusual dual superoleophobicity under immiscible oil-oil system. Exploiting its superlyophobicity under-liquid, the Cu(OH)2 nanowire covered copper mesh was applied to separate oil/water mixtures, emulsions, and oil/oil mixtures effectively, even though the surface tension between two liquids was just 2.4 mN/m. The separation efficiency is higher than 99% for all mixtures, and the oil/water separation efficiency can maintain above 98% even after 40 cycles. Furthermore, owing to its superaerophobicity underwater and underoil, the obtained copper mesh was also able to separate gas from bulk water and oil efficiently. This work is hoped to provide a key addition to the fields of ULSR surfaces as well as membrane-based separation techniques.

Wetting-induced superlyophobic polyacrylonitrile membranes: From reversible wettability to switchable on-demand emulsion separation

Super-wettable membranes have been extensively investigated due to their prospective applications in oily wastewater remediation. However, it is still a big challenge to develop super-wettable membranes via a facile and rationally designed method. In this work, we proposed a novel strategy to develop wetting-induced superlyophobic polyacrylonitrile (PAN) membranes with reversible wettability via in situ cross-linking polymerization and surface immobilization of nanoparticles during phase inversion process. The resulting membranes exhibited super-amphilic property in air, and were capable of converting their wetting behavior from underwater superoleophobicity to underoil superhydrophobicity with excellent dynamic stability. The membranes also displayed outstanding separation capability toward various surfactant-stabilized emulsions with separation efficiencies exceeding 99.2% under gravity. Moreover, the membranes could be regenerated with high performance preserved using a facile rinsing-and-drying method, and could be repeatedly applied to separate surfactant-stabilized emulsions. This work has made progress in the fabrication of super-amphiphilic membranes with superior separating performance through a facile method, providing great potential in practical application for oily wastewater treatment.

Superwettable neuron-inspired polyurethane nanofibrous materials with efficient selective separation performance towards various fluids

The filtration membranes for selective separating mixture of fluids or particles are of great importance to numerous fields, ranging from pharmaceutical industries, automotive industry, and chemical engineering to individual protection. However, current membranes are difficult to simultaneously attained high separation efficiency, high flux, and easy to scale up, which have restricted their practical applications. Herein, we have prepared the neuron-like polyurethane nanofibrous materials with numerous cavities among fibers and beads. The resultant membranes exhibited underoil superhydrophobicity (163°), extremely low adhesion force (1.13 μN), and sliding angle (1.7°). The superwettability, small pore size, high porosity, and interconnected pore channel endowed the membranes with good separation performance towards water-in-oil emulsions, including high separation efficiency of 99.44%, permeation flux of 3874 L m −2 h −1 , and good reusability in 15 cycles. In addition, the neuron-like PU nanofibrous membranes presented intriguing waterproof performance with water vapor transmission rate of 10592.3 g m −2 d −1 . Furthermore, the neuron-like PU nanofibrous membranes exhibited superior separation performance towards both sodium chloride and oily aerosol particles with filtration efficiency >99.99%, pressure drop of ∼90 Pa, and quality factor value > 0.1. The good selective separation performance of prepared PU nanofibrous membranes paves a way for fabricating filters for the separation of air/particles, oil/particles, emulsions, and water/moisture in different fields. • The robust neuron-like PU nanofibrous membranes were fabricated by electrospinning • The PU nanofibrous membranes exhibited superwettability to water and oil. • The membranes exhibited intriguing separation performance towards W/O emulsions. • The membrane presented good waterproof and air/oily aerosols filtration performance.

Superlyophobic graphene oxide/polydopamine coating under liquid system for liquid/liquid separation, dye removal, and anti-corrosion

It is highly desirable to develop superlyophobic surfaces under liquid system that can act as a versatile platform for separation of both oil/water and oil/oil mixtures and removing dye from water, but it is still hard to achieve. Herein, a graphene oxide/polydopamine (GO/PDA) coating with superlyophobicity under liquid system was fabricated through the self-polymerization of dopamine anchored on the GO sheet surface. The obtained GO/PDA coating possessed both under-water superoleophobicity and under-oil superhydrophobicity. Utilizing its dual superlyophobicity under an oil/water system, the GO/PDA coated fabric was applied to on-demand oil/water separation. Amazingly, the GO/PDA coated fabric exhibited dual superoleophobicity under an immiscible oil/oil system, which allowed it to separate oil/oil mixtures effectively. Due to the water affinity, layered texture, and absorption effect of the GO/PDA coating, the GO/PDA coated fabric can be served as a filtration module for removing dye from water efficiently. Moreover, the GO/PDA coating could also serve as a barrier to protect metal against corrosion.

Anchoring metal organic frameworks on nanofibers via etching-assisted strategy: Toward water-in-oil emulsion separation membranes

The zeolitic imidazolate framework-71/poly(vinylidene fluoride-hexafluoropropylene) (ZIF-71/PVDF-HFP) nanofibrous membrane was fabricated via anchoring ZIF-71 on PVDF-HFP nanofibrous membrane with targeted sites assisting. The ZIF-71 facilitated demulsification with increasing hydrophobicity. Eventually, the ZIF-71/PVDF-HFP nanofibrous membrane exhibited excellent separation performance for water-in-oil emulsions. • Etching-assisted strategy is used to anchor ZIF-71 nanoparticles on nanofibers. • The ZIF-71 increased roughness and hydrophobicity (162.1°). • Ultrahigh flux (4827.97 L m -2 h −1 ) and high efficiency (>99%). • The membranes exhibited excellent antifouling and cyclic stability. Efficiently separating water-in-oil emulsions is urgent demand and still worldwide challenge. Nanofibrous membranes with super-wetting surface have drawn wide concern to solve it. Herein, under-oil superhydrophobic zeolitic imidazolate framework-71/poly(vinylidene fluoride-hexafluoropropylene) (ZIF-71/PVDF-HFP) nanofibrous membranes were prepared via electrospinning and etching-assisted in-situ growth strategy for water-in-oil emulsions separation. ZnO was etched to create adsorption sites, ensuring the dispersed ZIF-71 nanoparticles firmly anchoring on nanofibers. The membranes showed under-oil superhydrophobicity with under-oil water contact angle 162.1°. The membranes could effectively separate a variety of water-in-oil emulsions (such as dichloromethane, chloroform, and toluene) by gravity. The separation efficiency of all emulsions was higher than 99% and the flux of water-in-chloroform without surfactant reached up to 6577.68 L m -2 h −1 . Moreover, the membranes exhibited excellent cyclic stability and anti-fouling. Therefore, the MOF/nanofibrous membranes fabricated by etching-assisted strategy are promised candidates for efficient oil/water separation.

Amphiphilic wood powders with dual superlyophobicity enabled the switchable separation of oil-in-water and water-in-oil emulsion with high flux

Materials with dual superlyophobicity (underwater superoleophobicity and underoil superhydrophobicity) show great promise in the switchable separation of oil-in-water (O/W) and water-in-oil (W/O) emulsion, while its preparation remains a challenge due to the contradictory demand of surface chemistries. In the present investigation, the green wood powders mainly consisted of cellulose, hemicellulose and lignin were demonstrated to be a dual superlyophobic platform by regionally wetting the hydrophilic or hydrophobic regions of the wood powders without additional modifications. The underwater oil contact angle and the underoil water contact angle of wood powders are high up to 158.0° and 161.5°, respectively. Furthermore, the wood powders feature fibrous structure, as well as a large porosity of 91.05%. Combined with the superior dual superlyophobicity and the unique fibrous structure, the wood powders enable the switchable separation of O/W and O/W emulsions efficiently. The achieved separation efficiency is as high as 99.9992%, with a flux of 4280.3 L m−2 h−1. The wood powders also showed good recycling capability. Our strategy might provide a general avenue to design dual superlyophobic materials that could be applicable for achieving switchable separation of O/W and W/O emulsions.