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Although the evaporation efficiency of photothermal materials (PMs) in pure water and brine solutions has been extensively studied, there few research on the performance in complex ...oily wastewater. Herein, a new monolithic solar steam generator derived from kapok fiber-based MXene composite aerogel (named as KFs-MXene) was fabricated by dipping the aerogels (KFs) which composed of kapok fiber and sodium alginate (SA) as substrates in the suspension of MXene. Benefitting from the outstanding light absorption (about 97%), better thermal insulation (thermal conductivity, 0.05039 W m−1 K−1), abundant porosity (95.60%) and rapid water transportation. KFs-MXene show good interfacial solar steam generation (ISSG) performance, resulting in a high water evaporation rate of 1.47 kg m−2h−1 with an outstanding evaporation efficiency of 90.4% under 1 kW m−2 irradiation. To improve the antifouling performance of KFs-MXene, chemically hydrophilic and oleophobic modification was applied, making the KFs-MXene can also be widely used in oily wastewater. Under 1 kW m−2 illumination, the evaporation rate and energy conversion efficiency of KFs-MXene with hydrophilic and oleophobic modification (O-KFs-MXene) in 1 wt% oily water can reach to 1.40 kg m−2h−1 and 82.87%, and the evaporation efficiency and rate of O-KFs-MXene remain stable in the continuous 6 h solar driven interface evaporation process.
Super-wetting membranes with outstanding permeation and anti-fouling performance are promising candidates for highly-efficient oily wastewater treatment. Herein, we designed a facile strategy to ...fabricate the super-hydrophilic/underwater super-oleophobic two-dimensional MXene-based composite membrane via vacuum-assisted self-assembly of two-dimensional MXene nanosheets on porous polyvinylidene fluoride (PVDF) substrate and in situ mineralization of photocatalyst β-FeOOH on the membrane surface. Benefiting from the inherent super-wettability and regulated lamellar structure (Short transport pathway and abundant nanochannels), the resultant MXene-based composite membrane displayed fast permeation flux (500.38–1022.7 L m−2 h−1) and favorable separation efficiency (99.32–99.72%) for a series of micro-scaled oil-in-water emulsions. Importantly, the excellent photo-induced self-cleaning capability and low oil-adhesion contributed to the high anti-fouling resistance, outstanding reusability, and durability of 2D MXene composite membrane. Moreover, the 2D MXene composite membrane exhibited superior chemical stability, which enabled it to maintain highly efficient oil/water separation performance in high-temperature, high salty, and strongly corrosive conditions. This work provides a feasible route to fabricate durable super-wetting 2D membranes with photo-Fenton self-cleaning capability for the oily wastewater treatment in harsh environments.
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•A novel strategy was developed to prepare superwetting MXene composite membrane.•Photocatalyst β-FeOOH endowed membrane with photo-induced self-cleaning ability.•Membrane exhibited high flux and oil rejection for various oil/water emulsions.•Membrane kept stable and efficient separation performance in harsh environments.
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•TA-APTES/MXene composite membranes were fabricated by nature-inspired method.•Ultra-high flux and excellent rejection for O/W emulsion were realized.•The membranes exhibited ...outstanding oleophobic and antifouling properties.
Nature inspired ‘green’ method has been reported for the fabrication of nanoparticles from the plant derived polyphenol tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES). In present investigation, TA-APTES nanoparticles decorated MXene nanosheets were acted as active layers and TA-APTES@MXene composite membrane were constructed by vacuum self-assembly on cellulose acetate support in order to improve membrane performance. The modified membrane showed an excellent hydrophilicity with a water flux of 5990.11 L·m−2·h−1 at 0.1 MPa, which is 15 times higher than pure MXene membrane. Moreover, the removal ratios of three different types of oil/water emulsions (petroleum ether, lubricating oil and vegetable oil) were found to be more than 98%. More importantly, the highly oleophobic membrane surface maintained a relatively high separation performances after four consecutive cycles of performances. This investigation achieves a leap of MXene-based membrane materials from nano- to micro-scale, which provides valuable insights in the field of oil/water separation.
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•A superamphiphilic TiO2-coated stainless steel mesh is fabricated.•The mesh is superhydrophobic under oil and strongly oleophobic under water.•The mesh realizes switchable and ...simultaneous oil/water separation via prewetting.•The mesh shows good oil/water separation performance and self-cleaning property.
To address the challenges for the common single-mesh oil/water separation, prewetting-induced simultaneous separation methodology with the same material is developed and achieved by a self-fabricated superamphiphilic TiO2-coated stainless steel mesh with switchable transportation manners of oil and water based on its superhydrophobicity under oil and strong oleophobicity under water. Furthermore, the mesh is highly recyclable in its separation efficiency (more than 99.9%), flux and self-cleaning property, and tends to be a promising material for controllable oil/water separation.
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•The porous structure of the PDMS is formed by an emulsion template method.•Polydopamine and silver endow the foams with underwater superoleophobicity.•Oil rejection efficiency of ...99.99% is reached by gravity-driven filtration.•During the gravity-driven filtration high flow rates are reached.•The foams filter oil-water mixtures while disinfecting the permeate.
Herein, we present the fabrication of multifunctional polydimethylsiloxane (PDMS) foams with antibacterial, hydrophilic, and underwater superoleophobic properties for the separation of oil-water mixtures and simultaneous water disinfection. The PDMS foams, prepared following the high internal phase emulsion templating method, exhibit a porous interconnected structure and were further functionalized with a polydopamine (PDA) layer and in-situ grown silver nanoparticles (Ag NPs) upon successive dipping processes in dopamine and silver nitrate solutions. We demonstrate the successful use of the developed foams as 3D filters for the gravity-driven separation of oil-water mixtures and the subsequent disinfection of the filtered water. The flow rate of oil-water mixtures is strongly correlated to the in-situ grown Ag NPs density present on the foams, in contrary to the oil rejection efficiency, which is above 99.99% in all the studied cases. In fact, the flow rate values increase with the increasing density of the in-situ formed Ag NPs starting from 1937.7 ± 580.4 L m−2 h−1 for the foam without Ag NPs and reaching 4043.0 ± 710.7 L m−2 h−1 for the foam with the highest amount of NPs. Taking the latter as an example, we prove that the foams can be used for several filtration cycles without any modification of their oil rejection efficiency. In addition to efficient oil-water separation, the foams have antibacterial properties and are able to disinfect the permeate. The simple preparation method, effective gravity-driven filtration, robust nature, and antibacterial capability make the herein engineered multifunctional foams promising for highly efficient filtration processes.
•Compressive bending for modulating microscale shapes.•Downsizing microscale features by applying compressive bending.•Fabrication of inversely tapered shapes for oil repellent ...functions.•Manipulation of oil repellency by using elastomeric films.•Enhancement of oil repellency on a surface with hyperbolic microarrays.
Applying elastic deformation to modulate the microscale surface shapes of films is an efficient way to prepare samples with various geometric designs. Tensile stress can be applied by stretching films, and it can increase the pitches of line arrays or the diameters of pillar arrays on a film surface. However, it is difficult to apply lateral compressive stress to films because films buckle during compression. In this study, we exploit bending to apply lateral compressive stress to the surface of a film. To accomplish this, we use arrays of microhyperbolic pillars or lines that have inversely tapered shapes in the upper region and widened bottoms. By using deformation of elastomeric films and a subsequent replication process, we fabricate microhyperbolic structures with decreased pitches and increased pattern heights. In addition, the deformation of microarrays by compressive stress can enhance oil repellency by increasing the sharpness of the inversely tapered shapes. Using this concept, we demonstrate the enhancement of oil repellency on patterned surfaces prepared by compressive bending of microarrays. Furthermore, we provide selective oil repellency by modulating the compressive stress on a single line array. The concept of compressive bending can be applied widely to decrease the dimensions of arrays and modulate surface shapes for greater oil repellency.
Membrane distillation, which can utilize low grade energy, has attracted significant attention recently. However, membrane fouling is a big issue impeding its development and industrialization. ...Hence, it is essential to prepare amphiphobic membrane for comprehensive anti-fouling performance. Herein, a facile and biomimetic method is explored to design amphiphobic surface with special structure and controllable wettability. Commercial polyvinylidene fluoride (PVDF) was primarily functionalized with polydopamine (PDA) coatings and then nanoscale roughness was introduced on the membrane surface, followed by the fluorination of 1H,1H,2H,2H-perfluorodecanethiol. It is revealed that the amphiphobic property can be accurately controlled by controlling the dosage of Ag+. When the concentration of Ag+ is 300 mM, the water and oil contact angle of the optimal membrane can achieve 167.6 ± 0.27° and 136.9 ± 0.4°, respectively, while the water sliding angle is only 3 ± 0.1°, which demonstrates prominent superhydrophobicity and oleophobicity. Furthermore, the amphiphobic membrane exhibits excellent chemical and thermal stability under harsh conditions as well as outstanding comprehensive anti-fouling capacity with higher flux and excellent salt rejection in the long-term direct contact membrane distillation (DCMD) experiments, which shows promising potentials for application in the field of membrane distillation.
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•A facile method was explored to prepare amphiphobic membrane for desalination.•The surface wettability can be accurately controlled.•The amphiphobic membrane showed high permeate flux and excellent fouling resistance.
Emulsion-templated, hydrophilic-oleophobic porous materials are promising for various applications, but their relatively weak mechanical properties of the resulting materials hinder them from real ...applications. Herein, we report the fabrication of emulsion-templated, hydrophilic and underwater oleophobic poly(vinyl alcohol) aerogels with enhanced mechanical property, bereft of the use of fluorine-containing components. The resulting aerogels exhibited flexibility, compression and stretchability both in dry and in wet states, showing enhanced compressive and tensile performances. The hydrophilicity and underwater oleophobicity enabled the pre-wet aerogels to have anti-fouling property and suitable for removing water from oil-water mixtures and surfactant-stabilized, water-in-oil emulsions. Taking their advantageous wettability, the aerogels were studied for solar steam evaporation from oil-containing salt aqueous solution after coating a thin layer of carbon nanotubes at the top. The evaporators showed high water evaporation rate (up to 2.7 kg m−2 h−1), high light-to-thermal conversion efficiency (up to 99%) and excellent continuous evaporation rate at 2.1 kg m−2 h−1 after 10 h′ continuous evaporation. The hydrophilicity, underwater oleophobicity and enhanced mechanical properties enabled the PVA aerogels as good candidates for removing water from various oil-water mixtures and for preparing solar steam evaporators.
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•Hydrophilic and underwater oleophobic PVA aerogels were obtained from emulsion templating.•The aerogels exhibited flexibility, robust compression and stretchability.•The pre-wet aerogels could remove water from oil-water mixtures (emulsions).•The aerogels served as an efficient solar steam evaporator, after surface coating.
A hierarchically structured membrane was fabricated for oil/water separation by effectively depositing ZnO nanoparticles on a glass fiber (GF) membrane. Simple potassium permanganate solution ...treatment of the GF membranes resulted in the formation of an Mn–(hydroxy)oxide deposit seed layer on the membranes, and then, chemical bath deposition was applied to deposit zinc oxide nanoparticles on the membranes. The scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) showed that ZnO nanostructures were effectively deposited on the membrane surfaces. The ZnO coated membranes were underwater superoleophobic with oil contact angles greater than 150°. An oil-water separation process driven by gravity demonstrated that the membranes could maintain a permeation flux greater than 250 L/m2-h with separation efficiencies above 98%. In addition, the ZnO coated membranes exhibited excellent oil/water separation performance in the reusability and durability tests. The results suggest that the ZnO coated membranes possess not only stability but also comprehensive applicability.
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•The membranes were fabricated by designing hierarchical structures on GF membranes.•The ZnO coated membrane can effectively separate water from oil/water mixtures.•The NP-60 membrane showed excellent oil/water separation performance in the tests.
In this study, we developed composite membranes with a hydrophobic substrate and a hydrophilic top surface using electrospinning to mitigate oil fouling in membrane distillation (MD). The ...electrospinning approach can be universally applied to any hydrophobic membrane substrate and to ensure the non-wetting condition of the substrate due to the electrospun fibrous structure. Using this approach, polytetrafluoroethylene (PTFE) hydrophobic substrate was coated with two different hydrophilic fibrous networks, including a cellulose acetate (CA) fibrous network and a nanocomposite fibrous network comprising CA and silica nanoparticles (SiNPs). We characterized the pristine and the modified membranes using contact angle measurements and tensiometer-based oil probe force spectroscopy, and tested the anti-fouling performance of the different membranes in MD experiments using a saline crude-oil emulsion as the feed solution. While both coatings offered significant improvement in oil fouling resistance compared to the substrate PTFE membrane, the nanocomposite CA-SiNPs fibrous coating outperformed the CA coating in terms of hydrophilicity, oil adhesion resistance, and anti-oil-fouling performance in MD experiments.
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•Composite membrane with electrospun multiscale-textured surface was fabricated.•The membrane surface was hydrophilic in air and underwater superoleophobic.•The composite membrane showed robust oil-fouling resistance in DCMD.•Oil probe force spectroscopy was introduced to evaluate oil-membrane interaction.
