High Separation Flux Research Articles

Long-lived superhydrophobic micro/nano-locked fiber membranes for long-lasting oil-water separation effectiveness

Superhydrophobic/superoleophilic oil-water separation membranes have great potential for treating industrial, domestic, and marine oily wastewater. However, the robustness of these membranes remains a challenge that restricts their ability to maintain long-lasting oil-water separation effectiveness. Inspired by the adhesion mechanisms of snail and tree frog, exploiting the synergistic effects of interfacial hydrogen bonding and mechanical interlocking, we herein achieved strong adhesion between hydrophobicized in-situ nanoparticles and textile fibers to fabricate a long-lived superhydrophobic micro/nano-locked fiber membrane (LSMFM). LSMFM maintains excellent superhydrophobicity even when exposed to mechanical and chemical damage, such as continuous sandpaper abrasion, tape-peeling, weight impact, water jet, and acid/alkali/salt erosion. Additionally, LSMFM efficiently separates various light/heavy oil-water mixtures, achieving a remarkable separation flux of >10,000 L·m−2·h−1 and an efficiency >98 %, even after 200 cycles with n-hexane. Importantly, such membranes still maintain a high separation flux >19,000 L·m−2·h−1 and efficiency >97 % after sequentially being subjected to acids, alkalis, freezing, and high temperatures, and even the adsorption bag formed by wrapping LSMFM with superhydrophilic wood pulp cotton can adsorb oil at fixed-point and continuously recover pure oil from oily wastewater. This study paves a new way for the sustainable purification of oily wastewater in extreme environments.

Degradable polyvinyl alcohol/chitosan@carnauba wax superhydrophobic composite membrane for water-in-oil emulsion separation and heavy metal adsorption

At present, many oil-water separation membranes are being developed to purify oily wastewater. However, oily wastewater often contains heavy metal, which are often difficult to dispose during separation. Furthermore, most of the oil-water separation membranes cannot be degraded after scrap, producing pollution to environment. Herein, the polyvinyl alcohol/chitosan@carnauba wax (PCGCW) membrane with heavy metal adsorption and biodegradation performance was acquired by electrospinning and spraying process. The acquired PCGCW membrane had excellent mechanical properties after crosslinking glutaraldehyde (GA). Furthermore, the composite membrane had excellent superhydrophobic property (WCA = 154°) with a rolling angle of 2°, due to the introduction of carnauba wax. Exhilaratingly, for emulsions with surfactant, it had a high separation flux with 19,217 L·m−2·h−1·bar−1 and splendid an oil purity over 99.9 %. Besides, the efficiency of oil purity and separation flux remained stable even after 10 separations. In addition, the PCGCW membrane had the ability to adsorb heavy metals with adsorption capacity of 51–106 mg/g for Cu2+, Fe3+, Co2+ ions. Foremost, the superhydrophobic PCGCW membrane was biodegradable, with degrading 29.76 % within 40 days. The prepared composite membrane had the advantages of low cost, high separation flux, great repeatability, adsorbable heavy metals and degradability, which had a vast application prospect.

Highly Water‐Rich Robust Coating for Separating Immiscible Liquids Mixtures of Wide Range of Surface Tension Differences

AbstractDeveloping mechanically robust and chemically tolerant coatings that maintain a high water content remains an extremely challenging task to pursue to date. Here, an optimum reinforcement of a hollow nano‐clay i.e., halloysite in a dual crosslinked and interpenetrating polymeric network is introduced to yield a high (≈95 wt%) water content coating with an ability to improve toughness (9.9 ± 0.6 MJm−3 Vs. 0.5 ± 0.03 MJ m−3) of a deformable fibrous substrate. The association of covalent and physical crosslinking chemistries provides essential tolerance against exposures to diverse severe chemically complex conditions, including extremes of pH, seawater, river water, and organic solvents. High water content in the prepared hydrogel network endows a robust bio‐inspired underwater nonadhesive superoleophobicity with oil contact angle of 160.7 ± 0.2° and force of oil‐droplet adhesion of 8.7 ± 0.3 µN. This approach provides a liquid selective filtrating membrane with ultrahigh crude oil/water separation efficiency (99.7%), superior intrusion pressure (3.5 ± 0.4 kPa), relatively high separation flux (11,162 Lm−2 h−1), and the ability to perform even when the surface tension of aqueous phase is brought down to similar of oily phase. Moreover, a mixture of immiscible, non‐aqueous liquids having differences in surface tension below 2.5 mN m−1 is successfully separated.

Anti-fouling underwater superoleophobic membranes based on hierarchical double networks for high efficiency oil–water separation

Oil fouling is a key problem of superwettable oil–water separation membranes because the membranes are inevitably susceptible to varying degrees of oil contamination during the ongoing separation processes, which usually results in a severe impact on separation performance. Consequently, it is a great challenge to construct oil-removal membranes with superior resistance to oil contamination. Herein, we fabricated hierarchical double networks (HDT)-modified porous glass membrane with superhydrophilicity/underwater superoleophobicity. Firstly, a layer of silicone nanofilament (SNF) network bearing tremendous C = C double bonds were fabricated on a porous glass membrane surface by one-step chemical vapor deposition (CVD) using vinyltrichlorosilane (VTCS) as a precursor. Subsequently, the second network layer was constructed by copolymerization of the C = C double bonds on the SNF network and those in sulfobetaine-derived monomer (sulfobetaine methacrylate, SBMA), using N,N′-methylenebisacrylamide (MBA) as the cross-linkering agent. It was observed that the obtained HDT-modified glass membranes displayed excellent superhydrophilicity/underwater superoleophobicity accompanied with superior self-cleaning performance and oil-resistance properties. As a result, the HDT-modified membranes showed high separation flux and high efficiency for both oil/water mixtures (7500 L m−2h−1, above 99.98%) and surfactant-stabilized oil-in-water emulsions (1100 L m−2h−1, above 99.96%) with excellent cyclability. The outstanding advantages with characteristics of excellent oil resistance and superior separation performance enable the HDT-modified glass membrane promising applications in a wide range of industries related to oil–water separations.

Cysteine-based antifouling superhydrophilic membranes prepared via facile thiol-ene click chemistry for efficient oil-water separation

Superhydrophilic membranes with underwater superoleophobicity for oil-water separation have been attracted widely attention. Nevertheless, oil contamination of such membranes represents a pressing challenge in this field. Superhydrophilic/underwater superoleophobic membranes with surface zwitterionic moieties are proved to show excellent antifouling properties; however, such zwitterionic surface modifiers adopted previously usually face the problem of cumbersome synthesis relying on expensive reagents and complicated procedures, accompanied with poor acid/alkali resistance due to the unstable linkers, restricting their practical applications. Herein, we describe an alternative strategy for fabricating antifouling superhydrophilic/underwater superoleophobic membranes from a natural amino acid. Sand particle-based sintered glass membranes were firstly coated with silicone nanofilaments using vinyltrichlorosilane as a precursor through chemical vapor deposition; and then the surfaces of silicone nanofilaments were further functionalized with cysteine via thiol-ene click chemistry. The resulting membranes exhibited high separation flux and efficiency for gravity-driven separation of various oil-water mixtures and surfactant-stabilized oil-in-water emulsions. Moreover, such membranes displayed excellent antifouling properties and were reusable for the separation of oil-water mixtures and surfactant-stabilized oil-in-water emulsions. With the advantages of facile fabrication, low-cost, fouling resistance and high separation performance, we believe that cysteine-based glass membranes without any hydrolytic bonds will arouse tremendous attentions for oil-water separation.

Flower-like ZnO modified TiO2@Ti3C2Tx composite for efficient adsorption of malachite green and oil-water separation

The intensification of industrial production has led to a sharp increase in the discharge of toxic organic chemicals and wastewater from printing and dyeing industry. In this study, flower-like ZnO modified TiO2@Ti3C2Tx composites (ZnO/TiO2@Ti3C2Tx) were prepared by in-situ oxidation solvothermal method from zinc nitrate hexahydrate and tetramethylammonium hydroxide intercalated Ti3C2Tx. During the solvothermal processes, sodium hydroxide acted as an etchant to further exfoliated the accordion-like Ti3C2Tx into single or few-layer; and at the same time, TiO2 was formed in-situ on the surface of Ti3C2Tx with simultaneous deposition of flower-like ZnO. The layer structural Ti3C2Tx facilitates the loading and dispersion of ZnO and TiO2 on its surface. After the in-situ oxidation by solvothermal method, TiO2 was evenly distributed on the surface of Ti3C2Tx, adjusting the functional groups on the surface of the ZnO/TiO2@Ti3C2Tx composite, and improving its adsorption performance. ZnO/TiO2@Ti3C2Tx can be used as an efficient adsorbent for malachite green with a high maximum adsorption capacity of 1232.7 mg g−1, which is higher than that of TiO2@Ti3C2Tx (628.57 mg g−1). Moreover, a superhydrophilic and underwater superoleophobic ZnO/TiO2@Ti3C2Tx@PU sponge was prepared by loading ZnO/TiO2@Ti3C2Tx onto polyurethane (PU) sponge. The introduction of ZnO enhances the surface roughness of the ZnO/TiO2@Ti3C2Tx@PU sponge, which can effectively separate six oil-water mixtures, and has a high separation flux of 171784 L m−2 h−1 and separation efficiency of 99.6% for cyclohexane-water mixture.

Robust and flexible polyester fiber membrane with under-liquid dual superlyophobicity for efficient on-demand oil-water separation

Functional materials with under-liquid dual superlyophobicity have generated a great deal of concern from researchers due to their switchable separation ability oil-water mixtures and emulsions. Conceptually, under-liquid dual superlyophobicity is a Cassie state achievable under-liquid through the synergy of an under-liquid double lyophobic surface and the construction of a highly rough surface. However, obtaining an under-liquid dual superlyophobic surface remains difficult due to its thermodynamic contradiction and complex surface composition. Herein, we successfully prepared a functional coating by modifying the mixture of cellulose nanocrystals (CNCs) and nano-TiO2 with perfluorooctanoic acid (PFOA) via a simple method, then obtained a polyester fiber membrane with under-liquid dual superlyophobicity by roll coating method. The surface wettability of the polyester (PET) membrane was altered, transforming it from the original under-water oleophobic/under-oil superhydrophilic state to the under-water superoleophobic/under-oil superhydrophobic state after coated. The resulting membrane was applied to separate oil and water on-demand. The coated PET membrane exhibited high separation efficiency (>99 %) and high separation flux, effectively separating immiscible oil-water systems as well as oil-in-water and water-in-oil emulsions. The coated PET membrane also demonstrated the ability to perform alternate separation of oil-water mixtures through wetting, washing, and rewetting cycles, with repeated processes up to 10 times without significant reduction in separation efficiency. Furthermore, compared with the previous works, our approach offers a simpler and more convenient method for constructing under-liquid dual superlyophobic surface, making it more suitable for continuous corporate production. This study may provide inspiration for the production and application in large-scale of under-liquid dual superlyophobic membranes.

Facile construction of robust superhydrophobic ZIF‐8@pulp/cellulose nanofiber (CNF) membrane for multifunctional applications

Given the increasing contamination of freshwater supplies, it is essential to effectively treat industrial wastewater. However, treating industrial wastewater using a single method is challenging due to the presence of complex contaminants like petroleum, organic dyes, bacteria, and other complex contaminants. In this study, we present a straightforward and scalable approach to prepare multifunctional nanocellulose-based membranes (NM) that exhibit superhydrophobicity, self-cleaning, oil/water separation, photocatalysis, and anti-bioadhesion properties. To begin with, we created NM by extruding fiber slurry onto a stencil and drying it. Next, we built a polyurethane (PU)/ZIF‐8/1H, 1H, 2H, 2H‐perfluorooctyltriethoxysilane (POTS)-based superhydrophobic layer by spraying it over the NM's surface. By employing the aforementioned processes, we successfully integrated multiple functions into a single superhydrophobic NM. Our results demonstrate that the NM-PU/ZIF-8/POTS membrane exhibits superior hydrophobicity performance, with a high-water contact angle (166.8 ± 0.8°) and a low rolling angle (5 ± 0.3°). Moreover, these samples retain high-water contact angles and low rolling angles even in harsh environments such as acid and alkali solutions, high temperatures, abrasion resistance, UV aging resistance, bending and folding, tape peeling, and self-cleaning. The NM-PU/ZIF-8/POTS membrane also exhibits high and stable oil-water separation performance, with a separation efficiency of 94.6% and a relatively high separation flux (133.2 L·m−2·h−1). At the same time, the NM-PU/ZIF-8/POTS membrane exhibits water-in-oil emulsion separation ability. The membrane’s stability, effectiveness, and reusability were demonstrated through ten repetitions of degradation experiments using aqueous methylene blue solution, with the NM-PU/ZIF-8/POTS membrane exhibiting an excellent degradation rate (>94%). Finally, the bioadhesion resistance test indicated a reduction of 69.1% in the adhesion rate of the NM-PU/ZIF-8/POTS membrane. Overall, the creation of the NM-PU/ZIF-8/POTS membrane serves as a useful inspiration for the practical application of superhydrophobic NM in multifunctional integration, while also broadening the scope of membrane applications.

One-step candle soot-PDMS dip-coated superhydrophobic stainless steel mesh for oil-water separation

We presented a superhydrophobic stainless steel mesh (SSM) developed by facile one-step dip coating of candle soot (CS)-polydimethylsiloxane (PDMS) using chloroform as solvent for effective and durable oil-water separation. SSM dip coated with chloroform solution of 200 mg CS and 0.5 mL PDMS yielded water contact angle (WCA), oil contact angle (OCA) and sliding angle (SA) of 162 ± 2°, 0° and 4 ± 1°, respectively. In series of oil-water separation studies, superhydrophobic mesh revealed >98 % separation efficiency with high separation flux of 7810 L·m−2·h−1. The superhydrophobic mesh revealed excellent mechanical, chemical and thermal durability.

Anti-abrasion collagen fiber-based membrane functionalized by UiO-66-NH2 with ultra-high efficiency and stability for oil-in-water emulsions separation

Membrane separation strategies offer promising platform for the emulsion separation. However, the low mechanical strength of membrane separation layers and the trade-off between separation flux and efficiency present significant challenges. In this study, we report a CFM@UiO-66-NH2 membrane with high separation flux, efficiency and stability, through utilizing a robust anti-abrasion collagen fiber membrane (CFM) as the multifunctional support and UiO-66-NH2 by an in-situ growth as the separation layer. The high mechanical strength of the CFM compensated for the weakness of the separation layer, while the charge-breaking effect of UiO-66-NH2, along with the size sieving of its constituent separating layers and the capillary effect of the collagen fibers, contributed to the potential for efficient separation. Additionally, the CFM@UiO-66-NH2 membrane exhibited superhydrophilic properties, making it suitable for separating oil-in-water microemulsions and nanoemulsions stabilized by anionic surfactants. The membrane demonstrated remarkable separation efficiencies of up to 99.960% and a separation flux of 370.05 L·m−2·h−1. Moreover, it exhibits stability, durability, and abrasion resistance, maintaining excellent separation performance even when exposed to strong acids and alkalis without any damage to its structure and performance. After six cycles of reuse, it achieved a separation flux of 417.97 L·m−2·h−1 and a separation efficiency of 99.747%. Furthermore, after undergoing 500 cycles of strong abrasion, the separation flux remained at 124.39 L·m−2·h−1, with a separation efficiency of 99.992%. These properties make it suitable for the long-term use in harsh operating environments. We attribute these properties to the electrostatic effect resulting from the amino group on UiO-66-NH2 and its in-situ growth on the CFM, which forms a size-screening separation layer. Our work highlights the potential of the CFM@UiO-66-NH2 membrane as an environmentally friendly size-screening material for the efficient emulsion wastewater separation.

Asymmetric wettable three-dimensional Janus all-cellulose aerogel: Controllable construction with a similar phase self-assembling strategy and oil-water separation performance

Aqueous ecological environment is exacerbated by indiscriminate discharge of industrial and municipal wastewater, particularly oily contaminants. Janus materials with unique asymmetric wettability have been considered potential candidates for oil-water separation. Herein, we developed a novel approach to accomplish controllable construction of three-dimensional Janus all-cellulose aerogel with asymmetric wettability based on a similar phase self-assembling strategy. Significantly, the ratio of asymmetric structures could be controlled by tailoring thickness of hydrophobic/hydrophilic layers. Three-dimensional Janus all-cellulose aerogel had both super-hydrophilic/oleophilic and super-hydrophobic/oleophilic cellulose skeleton structures simultaneously. The adsorption capacity of the aerogel for oil reached up to 34.38 g/g. It could effectively separate a variety of oil-water mixtures and water-in-oil emulsions only driven by gravity, even surfactant-stabilized emulsions. The separation efficiency was more than 99% with the high separation flux. The ‘Trade-off’ effect in the field of membrane separation was avoided effectively. Three-dimensional Janus all-cellulose aerogel exhibited good stability and recyclability. Moreover, the demulsification and separation mechanism was analyzed in details. This work provided not only an environmental-friendly, facile and flexible approach to construct controllable three-dimensional asymmetric wettable Janus materials, but also a scientific understanding and development of the separation mechanism of three-dimensional Janus materials.

Dual-bionic superwetting gears with liquid directional steering for oil-water separation

Developing an effective and sustainable method for separating and purifying oily wastewater is a significant challenge. Conventional separation membrane and sponge systems are limited in their long-term usage due to weak antifouling abilities and poor processing capacity for systems with multiple oils. In this study, we present a dual-bionic superwetting gears overflow system with liquid steering abilities, which enables the separation of oil-in-water emulsions into pure phases. This is achieved through the synergistic effect of surface superwettability and complementary topological structures. By applying the surface energy matching principle, water and oil in the mixture rapidly and continuously spread on preferential gear surfaces, forming distinct liquid films that repel each other. The topological structures of the gears facilitate the overflow and rapid transfer of the liquid films, resulting in a high separation flux with the assistance of rotational motion. Importantly, this separation model mitigates the decrease in separation flux caused by fouling and maintains a consistently high separation efficiency for multiple oils with varying densities and surface tensions.

Functionalized waterworks sludge particles as column packing materials for simultaneous Cr (Ⅵ) removal and oil separation

Highly efficient and low-cost treatment of waterworks sludge and oil-containing Cr (Ⅵ) wastewater in one way is a challenge in the field of water treatment. Herein, a waste-control-waste strategy was proposed to fabricate a functionalized waterworks sludge-based Zn–Al layer double oxides material (Zn–Al LDOs/WS) for simultaneously separating Cr (Ⅵ) and oil. During the column separation process, due to the superhydrophilic/underwater superoleophobicity of Zn–Al LDOs/WS and the memory effect of LDHs, Cr (Ⅵ) will be stabled in the filter layer by electrostatic attraction and surface complexation between the Zn–Al LDHs/WS and Cr (Ⅵ), and the small oil droplets will coalesce into big oil droplets that be blocked in the separation column, thus achieving simultaneous separation. The Zn–Al LDOs/WS with hierarchical porous structure exhibit excellent simultaneous separation efficiency for Cr (Ⅵ) (99.69%) and oil (99.24%), and high separation flux (1063 L m−2 h−1). In addition, the separation efficiency and flux can be flexibly controlled by adjusting the filter layer thickness. The Zn–Al LDOs/WS also display strong acid and alkali resistance (pH 1–11), wide applicability range of initial Cr (Ⅵ) concentration (5–200 mg/L) and outstanding anti-interfering ion ability (Cl−, HCO3−, SO42−, NO3−, H2PO4−, CO32− and F−) in Cr (Ⅵ) and oil separation. Therefore, this work can not only improve treatment efficiency and save costs through simultaneous separation, effectively treat solid waste and complex wastewater, but also provide a theoretical basis for the design and application of functional materials derived from waste sludge.

A wood-based MOF membrane with high flux and efficiency for oil-in-water emulsions separation

Oily wastewater discharged from households and industries, especially stable oil-in-water emulsions, causes serious pollution to the human habitat. Thus, it is urgent to find an environmentally friendly, efficient, and low-cost method for separating stable oil-in-water emulsions. In this paper, a superhydrophilic wood-based composite membrane (wood/MIL-100(Fe) membrane) for separating oil-water emulsion was reported. The wood/MIL-100(Fe) membrane was made by in-situ growing MIL-100(Fe) on wood, which enhances the hydrophilic properties and roughness. The vertical micro-nano structure and superhydrophilicity of wood/MIL-100(Fe) membrane determines separation flux and efficiency. Consequently, the wood/MIL-100(Fe) membrane displays high separation flux (more than 1061 L·m−2·h−1) and efficiency (more than 99.9 %). In addition, the wood/MIL-100(Fe) membrane has good mechanical stability, chemical stability, and anti-fouling properties. The wood/MIL-100(Fe) membrane is expected to replace other filter membranes in water treatment and environmental restoration.

Switchable CAU-10-H mesh membrane for on-demand separation of immiscible oil/water mixtures and emulsions

There remains a great challenge to develop a switchable and feasible membrane for integrate reversible separation of oil/water mixtures. Herein, a highly-quality CAU-10-H mesh membrane with switchable superwettability was fabricated via solvothermal synthesis for on-demand oil/water separation. The CAU-10-H membrane exhibited under-liquid dual superlyophobicity due to the hierarchical micro-/nanostructures constructed by interpenetrating CAU-10-H crystals grown on the mesh. Meanwhile, the secondary growth time affecting the wetting behavior of the membrane is studied. More importantly, the membrane can achieve both immiscible oil/water separation and emulsion separation with high separation flux and high efficiency (>99.9%). Moreover, the membrane shows an excellent anti-corrosive property in various harsh environment. The present development would provide novel insights into the rational fabrication of MOF-based membranes for on-demand oil/water separation.

A biomimetic beetle-like membrane with superoleophilic SiO2-induced oil coalescence on superhydrophilic CuC2O4 nanosheet arrays for effective O/W emulsion separation

It is highly attractive to develop highly efficient oil-in-water (O/W) emulsion separation technologies for promoting the oily wastewater treatment. Herein, a novel inversely Stenocara beetle-like hierarchical structure of superhydrophobic SiO2 nanoparticle-decorated CuC2O4 nanosheet arrays were prepared on copper mesh membrane by bridging polydopamine (PDA) to make a SiO2/PDA@CuC2O4 membrane for substantially enhanced separation of O/W emulsions. The superhydrophobic SiO2 particles on the as-prepared SiO2/PDA@CuC2O4 membranes were served as localized active sites to induce coalescence of small-size oil droplets in oil-in-water (O/W) emulsions. Such innovated membrane delivered outstanding demulsification ability of O/W emulsion with a high separation flux of 2.5 kL⋅m−2⋅h−1 and its filtrate’s chemical oxygen demand (COD) being 30 and 100 mg⋅L−1 for surfactant-free emulsion (SFE) and surfactant-stabilized emulsion (SSE), respectively, and also exhibited a good anti-fouling performance in cycling tests. The innovative design strategy developed in this work broadens the application of superwetting materials for oil-water separation and presents a promising prospect in practical oily wastewater treatment applications.

Intelligent pH-responsive PMIA membrane with reversible wettability for controllable oil/water and emulsion separation

Intelligent membrane with reversible wettability is an ideal strategy for oil/water separation, but there are still limitations of the reality application of oil/water separation. This effort produced a distinctive, intelligent, pH-sensitive oil/water separation membrane. Modified silica (SiO2-OTES), low-budget titanic oxide (TiO2), decanoic acid (DA), pollution-free chitosan (CTS), and Poly (m-phthaloyl-m-phenylenediamine) (PMIA) are selected to combine to form a superhydrophobic SO@TDC/PM membrane. The wettability of the modified membrane is reversible under the different effects of ammonia treatment and heat treatment. Also, the intelligent membrane is used to achieve controllable separation of oil/water mixtures, and to effectively separate various oil-in-water emulsions and water-in-oil emulsions before and after wettability conversion. In addition, the intelligent membrane has excellent self-cleaning ability, a high separation flux, and high separation efficiency. At the same time, the intelligent membrane itself has good organic solvent, storage, and mechanical stability. The results show that SO@TDC/PM membrane has good reversible wettability, which provides a broad prospect for the development of intelligent response materials with reversible wettability.

Superhydrophilic polymer coatings based on PVDF membranes for oil-water separation

Recently, the excellent anti-pollution performance of superhydrophilic membrane has attracted much attention in the field of wastewater treatment and oil-water separationIn. At present, the widely used commercial membrane materials have good pore structure and mechanical properties, but most of the commercial membranes are hydrophobic, so a simple, environmentally friendly and universal method is urgently needed to change its hydrophobic membrane to superhydrophilic membrane. In this paper, tannic acid (TA, natural plant polyphenols) and polydopamine (PDA) were used to build an anti-stain coating. The synthesized hydrophilic polymer containing polyphenols crosslinks with the base layer through hydrogen bonding, π-π and Michael addition. After the modified PVDF membrane is moistened by water, the superhydrophilic polymer network on the surface binds the water to form a stable hydration layer, showing the superhydrophilic/underwater superhydrophobic properties. The wettability of the modified film in air and water was investigated. The contact Angle of the modified separation membrane prepared in this paper is more than 150°, and the separation efficiency exceeded 98%. The good flux and efficiency can be maintained after 5 cycles, and it is found that the membrane has a certain anti-protein adsorption capacity. The modified membrane has high separation flux and excellent reuse, and has great uses in other ways.

Hydrophobic Ti3C2Tx/PU sponge prepared from commercial amphiphilic PU sponge for oil/water separation with ultrahigh flux

The development of highly-selective absorbents with high separation flux for oil/water separation is a key requirement for wastewater pollution treatment. Herein, we successfully prepared a hydrophobic Ti3C2TX/polyurethane (Ti3C2TX/PU) sponge for oil/water separation with superior separation performance. The PU sponge selected in this paper features a sandwich-like structure with subcentimeter-level pores on its surface. After being modified with Ti3C2TX via a facile dip-coating process, the surface wettability of the PU sponge changed from amphiphilicity to hydrophobicity with a water contact angle of 122.4°. The as-prepared Ti3C2TX/PU sponge demonstrated high separation efficiencies (≥ 95.7%) and ultrahigh separation fluxes (up to 360340 L m−2 h−1) for various oil/water mixtures. Furthermore, it possessed a remarkable absorption capacity of 11–36 times its own weight towards a variety of oils and organic solvents. To verify the practical application of the Ti3C2TX/PU sponge, the separation and absorption performance was further investigated under various harsh conditions, such as high temperature, vigorous stirring, acidic/alkaline environments. Combining its excellent mechanical elasticity and recyclability, the Ti3C2TX/PU sponge can be suggested as a promising absorbent for removal of pollutants from wastewater under a wide range of harsh conditions.

An internal electrostatic force-driven superoleophilic membrane-magnetic nanoparticles coupling system for superefficient water-in-oil emulsions separation

The inefficient separation of water-in-oil emulsions through conventional techniques and the troublesome membrane fouling of membrane technology call for alternative efficient and antifouling membrane separation approaches to meet the increasing demands for global environmental protection and energy recovery. Here, we demonstrate an internal electrostatic force-driven superoleophilic membrane-magnetic particles coupling system enabling water-in-oil emulsions super-efficiently separated. Specifically, as-prepared magnetic nanoparticles significantly facilitate the separation of water-in-oil emulsions due to their superoleophilic behaviors and electrostatic repulsion forces between the magnetic nanoparticles-encapsulated Pickering emulsions. Furthermore, the magnetic nanoparticles incorporate into the membrane to increase the roughness and superoleophilic ability, distinctly leading to superefficient separation capacity for water-in-oil emulsions. Meanwhile, their separation performances are so stable that remarkably outperform other membrane systems during 10-cycle operation owing to the enhanced antifouling efficacy, under the support of electrostatic repulsion forces caused by the magnetic nanoparticles-modified composite membrane and magnetic nanoparticles-encapsulated Pickering emulsions. Hence, the combination of the electrostatic repulsion forces and interfacial forces render the as-constructed superoleophilic membrane-magnetic nanoparticles coupling system dramatically exhibit a remarkably high separation flux of 8.76 × 104 L m−2 h−1 bar−1 for the water-in-toluene emulsion under the conditions of pH of 10 and sodium dodecyl sulfate surfactant, considerably higher than the existing reports of the state-of-the-art membranes. This study will open up new avenues for superefficient and stable separation of water-in-oil emulsions in actual situations, and this concept will be promising for extending to other oil-in-water emulsions and oily waste water treatment.