High Oil-water Separation Efficiency Research Articles

Electrospun nanoscale bent fibrous membrane with controllable porous structure and hydrophilic modification for high-efficiency oil-water separation, particle/bacterial filtration and antibacterial applications

Electrospun nanofiber membranes' pore structure and hydrophilicity are essential for water filtration. Pore size may be efficiently lowered in this work by decreasing the fiber diameter, changing the fiber morphology, and constructing a silicon hybrid hydrophilic coating. The hydrophilic nanofiber membranes have a small pore size (0.72 μm) and an extremely low diameter (73.5 nm). Meanwhile, the synergistic combination of catechol (CA) and tannic acid (TA) with γ-(2, 3-epoxypropyl) propyl trimethoxysilane (KH560) resulted in the formation of a homogenous silicon hybrid hydrophilic coating on the surface of the fiber membrane. The hydrophilic nanofiber membrane has an outstanding hydrophilicity (WCA = 28.3°), excellent oil-in-water emulsion separation efficiency (>99.0%), extremely high particle filtration efficiency (>99.0%), and an LRV value of more than 7.50 for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). At 6.0 mg/mL, the antibacterial efficiency was 80% against E. coli and 96% against S. aureus. The preparation of such hydrophilic membranes can provide a novel strategy for high-quality design and development that can be applied to various water filtration applications.

Attapulgite-based nanofiber membrane with oriented channels for high-efficiency oil-water separation

Nanofiber membranes are distinguished for their high porosity and interconnected pore structures. However, their separation application and performances are affected by irregular pore structures which are formed by the randomly packing of nanofibers. Herein, we report a facile approach to produce nanofiber membranes with oriented channels, narrow pore size, and low tortuosity. The membranes show a bi-layered structure where magnetic attapulgite (mATP) nanofiber layers are directly supported on macroporous Al2O3 substrates. The mATP layers are prepared by drop-coating suspensions on top of the substrates pre-filled with water, and the ordered pore structures are formed at the presence of a magnetic field. Compared with the unordered membranes, average pore size of the ordered membranes reduces from 0.45 to 0.28 μm, with the water permeance increase from 1007 to 1121 L m−2 h−1·bar−1. Moreover, the stationary flux of ordered membranes increase by 59% with the retention to oil-in-water emulsion increase from 98.7% to 99.2%. Analysis of membrane fouling using the Hermia model shows that the ordered membrane can reduce membrane blocking and thus facilitate membrane cleaning and restore of separation performance.

Fabrication of ZnO/PDA/GO composite membrane for high efficiency oil–water separation

Fabrication of ZnO/PDA/GO composite membrane for high efficiency oil–water separation

Enhanced hydrophobicity of shell-ligand-exchanged ZIF-8/melamine foam for excellent oil-water separation

Oil and organic solvent spills have caused serious environmental issues. To address these issues, several novel materials have been developed for the efficient separation of oil/organic solvents from water. In this study, ZIF-8 was loaded onto a melamine foam (MF) skeleton a simple in situ growth method. ZIF-8/MF was modified via a shell-ligand-exchange reaction (SLER) to improve its hydrophobicity. The prepared D-ZIF-8/MF exhibited strong hydrophobicity, with a WCA of 145.1° and an OCA of 0°. D-ZIF-8/MF can absorb up to 68–165 times its weight in oil/organic solvents. D-ZIF-8/MF also exhibited excellent stability, corrosion resistance, recovery, and recyclability. Furthermore, D-ZIF-8/MF has a high oil-water separation efficiency for absorbing organic solvents through a continuous oil-water separation device. This study provides a novel strategy for the preparation of strong hydrophobic foams via surface modification and SLER for oil-water separation. It has immense potential for the scale-up practical treatment of oily wastewater.

Rational design of self-cleaning superhydrophobic coating with outstanding abrasion resistance and weatherability: Towards highly efficient oil-water separation and anti-corrosion application

The importance of superhydrophobic coating in modern industries cannot be overstated. However, conventional superhydrophobic coatings are challenged by poor mechanical stability, single functionality, and toxic content (fluorine element), which pose a challenge to the large-scale use of superhydrophobic coatings. Herein, a MOF-based superhydrophobic coating is proposed, which is constructed by introducing self-designed small-molecule resins combined with modified ZIF-8 particles through a one-step spraying method. Notably, the coating exhibits excellent superhydrophobicity (CA = 169.05°, SA = 3.7°), mechanical stability (CA > 155° after 200 cm of wear), high oil-water separation efficiencies (for oil-water mixture separation efficiency up to 98.57 %) and satisfactory anti-corrosion property. The superior performance of the coating comes from the layer-by-layer structure formed by the γ-AP resin-coated ZIF-8 particles after curing, which the silicone in the resin forms a dense cross-linked network on the surface of the coating. In summary, ZIF-8/HDTMS/γ-AP coating not only has the advantages of a simple preparation process, wide application range, and no secondary pollution but also has excellent mechanical properties, high oil-water separation efficiency, and satisfactory corrosion resistance, which can provide new ideas to expand the application scope of superhydrophobic coating.

Novel Engineered Carbon Cloth-Based Self-Cleaning Membrane for High-Efficiency Oil-Water Separation.

A novel engineered carbon cloth (CC)-based self-cleaning membrane containing a Cu:TiO2 and Ag coating has been created via hydrothermal and light deposition methods. The engineered membrane with chrysanthemum morphology has superhydrophilic and underwater superoleophilic performance. The cooperativity strategy of Cu doping and Ag coating to the TiO2 is found to be critical for engineering the separation efficiency and self-cleaning skill of the CC-based membrane under visible light due to the modulated bandgap structure and surface plasmon resonance. The CC-based membrane has excellent oil-water separation performance when Cu is fixed at 2.5 wt% and the Ag coating reaches a certain amount of 0.003 mol/L AgNO3. The contact angle of underwater oil and the separation efficiency are 156° and 99.76%, respectively. Furthermore, the membrane has such an outstanding self-cleaning ability that the above performance can be nearly completely restored after 30 min of visible light irradiation, and the separation efficiency can still reach 99.65% after 100 cycles. Notably, the membrane with exceptional wear resistance and durability can work in various oil-water mixtures and harsh environments, indicating its potential as a new platform of the industrial-level available membrane in dealing with oily wastewater.

One-pot preparation of superhydrophobic lignocellulose composites and their oil-water separation properties

ABSTRACT Lignocellulose is a kind of renewable material with stable structure and abundant reserves. The superhydrophobic lignocellulose composites prepared by one-pot method in this study had the advantages of pollution-free, stable structure and simple processes. The prepared superhydrophobic lignocellulose composites exhibited superhydrophobic-superoleophilic wettability, with a water contact angle (CA) of 157° ± 3.6° and an oil CA of about 0°. Abrasion and ultraviolet (UV) radiation experiments demonstrated that the prepared composites had good mechanical stability and UV resistance. In addition, the composites presented an ultra-fast oil absorption rate and high oil-water separation efficiency of more than 96% for various types of oil-water mixtures. And the maximum oil flux was greater than 6500 L·m−2h−1bar−1. Such superhydrophobic lignocellulose composites hold great application prospects in the field of oil-water separation.

Rational Design of PDA/P-PVDF@PP Janus Membrane with Asymmetric Wettability for Switchable Emulsion Separation.

Water pollution caused by oil spills or sewage discharges has become a serious ecological environmental issue. Despite the membrane separation technique having a promising application in wastewater purification, the membrane fabrication method and separation robustness have remained unsatisfactory until now. Herein, we developed a novel strategy, spacer-assisted sequential phase conversion, to create a patterned polyvinylidene fluoride@polypropylene (P-PVDF@PP) substrate membrane with a multiscale roughened surface. Based on that surface structure, the underwater oil resistance behavior of the P-PVDF@PP membrane was improved. Moreover, owing to the abundant active sites on the P-PVDF@PP surface, the polydopamine/P-PVDF@PP (PDA/P-PVDF@PP) Janus membrane could be readily fabricated via wet chemical modification, which exhibited excellent switchable oil-water separation performance. Regarding surfactant-stabilized oil-water emulsion, the as-prepared PDA/P-PVDF@PP Janus membrane also had robust separation efficiency (as high as 99% in the n-hexane/water, chloroform/water, and toluene/water emulsion separation cases) and desirable reusability. Finally, the underlying mechanism of emulsion separation in the PDA/P-PVDF@PP Janus membrane was specified. The as-designed PDA/P-PVDF@PP Janus membrane with high-efficiency oil-water separation shows potential application in oily wastewater treatment, and the developed fabrication method has implications for the fabrication of advanced separation membranes.

Underwater superoleophobic GO-PEI-SiO2-Hal quaternary sphere-rod nacre-inspired mesh by LBL self-assembly for high-efficiency oil-water separation

The easy preparation of robust superwetting materials for oily wastewater disposal still remains a challenge. Inspired by the self-cleaning and mechanical properties of natural nacre underwater, herein, we have successfully developed sphere-rod quaternary artificial nacre-inspired meshes (named GO-PEI-SiO2-Hal) via interfacial self-assembly using 2D graphene oxide nanosheets, hyperbranched polyethyleneimine, SiO2 nanospheres, and hollow halloysite nanotubes (Hal) as the building blocks. The nacre-like “brick-and-mortar” layered microstructure was successfully formed and tightly coated to the mesh, showing excellent mechanical properties with Young's modulus up to 19.7 ± 2.6 GPa. Compared to the ternary structures, the quaternary sphere-rod morphology improved the surface roughness, and these four organic/inorganic building blocks are all hydrophilic, which together resulted in the superhydrophilic and underwater superoleophobic characteristics. The effects of building block concentration, dipping number, and mesh size on wettability and oil-water separation performance were studied in detail. The optimal (GO-PEI-SiO2-Hal-1)15@Fe300 mesh showed an underwater oil contact angle of 159o for 1,2-dichloroethane, low oil adhesion, and excellent separation efficiency up to 99.8% at an ultrahigh flux up to 195,038 L m−2 h−1. This nacre-like mesh exhibited excellent salt tolerance, acid-alkali resistance, recycling ability, and mechanical properties for practical oily wastewater treatment.

High-hydrophobic ZIF-67@PLA honeycomb aerogel for efficient oil–water separation

The ZIF-67 @PLA honeycomb aerogel was formulated by using the metal–organic frame (MOF) ZIF-67 through physical mixing and heat-induced phase separation interaction. Changing the mass fraction ratio of ZIF-67 in aerogels can effectively adjust the pore size, pore surface unevenness, and specific surface area of pure polylactic acid (PLA) aerogels. In comparison to PLA aerogels, the ZIF-67 @PLA honeycomb aerogels showed greater oil wettability combined with a notable increase in mechanical characteristics. In this paper, the morphology, oil adsorption capacity, oil wettability, oil–water separation ability and sample reuse of composite aerogels were studied in depth. The ZIF-67 @PLA aerogel with 3 wt% ZIF-67 has the highest oil wettability, highest oil–water separation function, maximum specific area and good reusability. Compared to pure PLA, which has a tensile strength and elongation at break of 0.1424 MPa and 13%, ZIF-67 @PLA has a tensile strength and elongation at break of 0.3344 MPa and 15%, respectively. After 20 cycles, the separation flux of ZIF-67 @PLA is still 98% of the initial flux. The experimental results show that the use of MOF as a nanofiller-filled pure PLA aerogel exhibits high oil wettability and has been demonstrated to be an ideal material for high-efficiency oil–water separation.

Hyper cross-linked poly(ionic liquid)s with special anions as “smart materials” for switchable oil-water separation

Smart materials with superhydrophobic-superlipophobic switchability can selectively penetrate one phase (oil or water) through the surface, and the other is trapped. In this study, several super wetting materials were fabricated based on the modulation of Friedel–Crafts alkylation and ion exchange on hyper cross-linked poly(ionic liquid)s (HCPILs) properties. They showed high oil-water separation efficiency in different complex environments. These synthetic HCPILs exhibit different hydrophilicity or lipophilicity when containing various anions. In particular, the HCPIL with a hexafluorophosphate (HCPIL-PF6) or a bis(trifluoromethylsulfonyl)imide (HCPIL-TF2N) possesses a switchable super wetting property due to its unique surface structure and chemical composition. They can be freely switched between hyperhydrophilicity and hyperlipophilicity according to the corresponding solvent changes and are suitable for separating many oil-water mixtures, especially the emulsions. The respective separation flux of the oil-water mixture or lotion is up to 9450 L/m2·h and 800.32 L/m2·h. Besides, they have strong durability and stability in harsh environments such as high concentrations of salt, acid, and basic solutions. After dozens of cycles, they can maintain efficient oil-water separation efficiency and exhibit a high underwater oil contact angle or underoil water contact angle. Such smart materials have great potential in various practical applications, providing a significant idea for future continuous production.

Facile fabrication of superhydrophobic porous materials using the water-based aza-Michael reaction for high-efficiency oil-water separation

Superhydrophobic porous materials are widely used in oil-water separation due to their water-blocking and oil-passing properties. However, the preparation of most superhydrophobic porous materials is generally energy-intensive and must be performed using organic solvents. In this study, we describe a straightforward and cost-effective strategy for fabricating superhydrophobic coatings on nanosized soil particle-modified stainless steel mesh (SSM). The coating is prepared via the aza-Michael reaction of stearyl acrylate and melamine-urea–formaldehyde (MUF) resin catalysed by methyl cyclodextrin in water. Superhydrophobic meshes with water contact angles (WCAs) exceeding 150° are obtained, exhibiting extraordinary water repellency. The superhydrophobic mesh also effectively prevents surface contamination, creating a self-cleaning surface that is both waterproof and dustproof. Most importantly, the superhydrophobic mesh presents excellent oil separation performance for oil-water mixtures of various compositions, maintaining extremely high separation efficiency (>98%) even after 80 cycles. Additionally, we successfully apply this strategy to the preparation of superhydrophobic melamine sponges with excellent oil adsorption capacity (17.6–44.2 g/g). This innovative study provides an effective strategy for designing biomimetic superhydrophobic surfaces and is a promising development in the field of environmentally friendly oil-water separators.

Antifouling Hydrophilic Electrostatic Spinning PAN Membrane Based on Click Chemistry with High Efficiency Oil-water Separation

Antifouling Hydrophilic Electrostatic Spinning PAN Membrane Based on Click Chemistry with High Efficiency Oil-water Separation

A novel strategy to extend near-infrared light harvest of graphene for solar vapor generation and high-efficiency oil-water separation

Due to the feature of zero bandgap, graphene has presented a rapid and broadband photothermal responsibility. However, the near-infrared light absorption of graphene is relatively low, which is unfavourable for the full utilization of solar energy. Therefore, in our work, flower-like MoS2 nanostructure was used to promote the optical absorption of graphene. Further, combining with the porous skeleton of sugarcane residues and the simplified hydrophobic treatment method, a novel water treatment material (GNS@MoS2-SR) is successfully prepared. Recently, solar-assisted oily water treatment and solar steam generation were widely proposed to relieve the shortage of clean water. In the absorption test, it is confirmed that GNS@MoS2-SR can absorb 8.02–16.8 g/g oils from oil-water mixture and presents high stability during recycle. Moreover, the great hydrophobicity and photothermal conversion effect helps GNS@MoS2-SR to evaporate ∼1.778 kg/m2 water in 1 h, under one solar illumination (1 kW/m2). Besides, the optimized hydrophobicity of GNS@MoS2-SR effectively suppressed the salt precipitation and prevented the decline of spectrum absorption. The multifunctional water treatment material we designed integrates the respective advantages of graphene and MoS2, presents a significant potential in relieving water stress.

Wodyetia bifurcate structured carbon fabrics with durable superhydrophobicity for high-efficiency oil-water separation

The superhydrophobic fiber-based membranes with features of high separation efficiency and low energy consumption for oil-water separation remains a formidable challenge. In this paper, a robust and durable superhydrophobic cotton-derived carbon fabric (CDCF) with wodyetia bifurcate-like structure is fabricated via in situ cobalt-nickel basic carbonate (CNC) deposition and 1 H, 1 H, 2 H, 2 H-perfluorooctyltriethoxysilane (POTS) coating. The combined action of rough surface structure and low surface energy makes CDCF/CNC/POTS with superhydrophobicity/superoleophilicity, anti-wetting, and self-cleaning performance. Intriguingly, the CDCF/CNC/POTS can keep its superhydrophobicity under of the water droplet impact pressure of 781 Pa. In addition to its robust dynamic superhydrophobicity, CDCF/CNC/POTS can also maintain its non-wetting property under harsh environmental conditions such as mechanical abrasion treatment, acidic, alkaline and salt solutions, and ultraviolet radiation. Importantly, the CDCF/CNC/POTS can separate various oil-water mixtures and emulsions under gravity with ultrahigh oil-water mixtures permeate flux (∼19,126 L/m2h), high surfactant-stabilized emulsion permeate flux (∼821 L/m2h), and high separation efficiency (> 98.60 %). Moreover, remarkable recyclability endow the CDCF/CNC/POTS with promising application in treating oily wastewater. This work may benefit the low-cost mass production of cotton-based carbon fabrics for developing eco-friendly high-efficiency separators.

2D nanoneedle-like ZnO/SiO2 Janus membrane with asymmetric wettability for highly efficient separation of various oil/water mixtures

The offshore oil spills and the discharge of oily wastewater are not only doing harm to the economy but also disrupting our aquatic and biotic environment. In order to alleviate this serious situation, researchers have developed super-wettability membranes to achieve efficient oil-water separation. Among them, asymmetric wettability Janus membranes with unique selective permeable properties have received widespread attention. However, utilizing a facile and environment-friendly method to endow a material with Janus super wettability to realize high oil-water separation efficiency and selectivity is still a challenge. Herein, a low-cost strategy is used to electrodeposit flake Zn on the copper mesh. Super-hydrophilic ZnO can be grown on it by a simple hydrothermal method, and then the Janus membrane with asymmetric wettability can be obtained by spraying SiO2 and octadecanethiol modification. It is worth noting that at a suction pressure of 4 kPa, the separation efficiency of the light oil-water mixture can reach more than 99.99%, and the flux is up to 13067.5 L·m-2·h-1. Under the action of gravity, the separation efficiency of the heavy oil-water mixture can reach more than 99.80%, and the flux is about 2000 L·m-2·h-1. Undoubtedly, the Janus membrane can simplify the operation to achieve on-demand oil-water separation. Last but not least, it can still maintain good performance after acid-base corrosion, wear, and cyclic tests, thereby showing broad potential in the field of oil-water separation and environmental protection.

Facile preparation of hybrid coating-decorated cotton cloth with superoleophobicity in air for efficient light oil/water separation

Superwetting materials have attracted broad attention in oil-water separation application in the last few years. In our work, a kind of modified cotton cloth with superoleophobicity/superhydrophilicity in air is obtained by using polydopamine and nano silica powder to construct micro-nanostructure on cotton cloth and subsequent sodium perfluornonanoate decoration to reduce the surface energy. The results show that the modified cotton cloth has high contact angle (CA) to various oils, and the CAs to canola oil, flaxseed oil, corn oil, and sesame oil are 164.5°, 153°, 152.5°, 144.5°, respectively. The constructed cloth has high oil-water separation efficiency to the mixtures of corn oil, linseed oil, rapeseed oil and water. Even after 25 cycles, the efficiency is still higher than 97%. Besides, the modified cloth can resist severe friction damage and the CA to oil is still greater than 135° after 18 cycles of friction on sandpaper. Especially, the separation efficiencies to rapeseed oil in pH 2 solution, pH 12 solution, 3.5% NaCl solution, hot water, ice water are above 96%, implying the applicability of the cloth in harsh water environments.

High-strength, superhydrophilic/underwater superoleophobic multifunctional ceramics for high efficiency oil-water separation and water purification

The impacts of oily wastewater on water quality, aquatic ecosystems and human health are a global problem. Therefore, the development of multifunctional oil-water separation materials, that are capable of organic pollutant removal, is of high importance and remains a significant challenge. Herein, we report a combination of 3D printing technology with hydrothermal method and liquid phase deposition to prepare a hierarchical TiO2/Cu2O porous lattice structure with 3D structure strengthening with oil-water separation performance and visible light catalytic degradation. Due to its micro-nano hierarchical structure, the as-prepared ceramic lattice structure exhibited very high levels of hydrophilicity and oleophobicity in aquatic environments. The 3D printed lattice structure achieved excellent oil-water separation performance, with the separation efficiency of the body-centered cubic lattice structure reaching 99.6%. Furthermore, organic pollutants dissolved in water can be decomposed by visible light irradiation after separation, improving the utilization rate of solar energy. The 3D printed lattice structure exhibited a compressive strength of 44.89 MPa and an absorption energy of 55.17 kJ m−3, indicating good mechanical strength and resistance to deformation. Overall, the use of 3D printing for structural strengthening of this multifunctional superhydrophilic and underwater superoleophobic lattice structure, is a promising method with a wide range of potential applications in environmental protection, particularly for the treatment of oily wastewater and the degradation of organic pollutants.

High-efficiency oil-water separation and passive radiant cooling performance of nano-ZnO- embedded dust-free paper

Developing a flexible nano-composite material which is not only impermeable to low-polar oil, but also has the ability of daytime radiation cooling, remains a huge challenge for both academia and industry. By modifying the fiber network of the dust-free paper using nano-ZnO particles (ZnO-DF), we strategically designed and demonstrated dual capabilities of superhydrophilicity/superoleophobicity and daytime radiant cooling for the flexible cellulose nano-composite simultaneously. A superior surface with superhydrophilic/superoleophobic (oil contact angle up to 159° and water contact angle down to 0°) was attained by regulation of surface energy components and roughness. Furthermore, the materials revealed outstanding corrosion and mechanical damage resistance, 152,788 L m−2 h−1 high permeation flux and >99.2% continuous and efficient oil-water separation performance. In addition, a cooling effect of about 5.6 °C of ZnO-DF paper could be achieved by cooperative function of both radiative cooling and sweat evaporation. It is expected that the ZnO-DF paper is promising for the thermal management of wearable products integrated with passive radiant cooling, phase change cooling (e.g., sweat evaporation) and large-scale industrial oil-water separation.

Superhydrophobic, flame-retardant and magnetic polyurethane sponge for oil-water separation

With the increasing environmental pollution by frequent spill accidents and industrial wastewater emissions, superhydrophobic materials for oil-water separation have attracted considerable attention. Herein, we proposed a facile method to prepare superhydrophobic, flame-retardant and magnetic polyurethane sponge (SFRM-PUS) for oil-water separation. Firstly, pristine PUS was immersion-coated with ferric oxide (Fe3O4) nanoparticles, graphene oxide (GO) and phytic acid, and then treated with hydroiodic acid (HI) to reduce GO and modified with perfluorooctyltriethylsilane to provide low surface energy. The SFRM-PUS had a high water contact angle of 156° and a low water sliding angle of 8.9°, and exhibited excellent anti-adhesion property and high oil-water separation efficiency of 98.9%. By means of the magnetic property, the SFRM-PUS was also applied for the removal of oil from water in specified area. In addition, the SFRM-PUS showed superior flame-retardant performance, and the ignited flame extinguished within only 4 s. Our findings conceivably provided a new strategy to prepare functional superhydrophobic materials for the treatment of oil spill accidents and industrial sewage emissions.