Underwater Superoleophobic Mesh Research Articles

The optimized microbial-induced calcium carbonate precipitation process to fabricate underwater superoleophobic mesh for efficient oil-water separation

Microbial-induced calcium carbonate precipitation (MICP) is an environmentally-friendly and easy operation technique for separating oil-water mixtures. However, the effect of environmental factors on the wettability and oil-water separation performance of MICP remains unclear. In this study, three primary factors including mineralization solution (MS) concentration, bacterial suspension (BS) concentration, and temperature were carefully investigated. Under these varying conditions, stainless steel meshes (SSM) were chosen as the substrates for the growth of CaCO3 precipitations. Experimental results demonstrate a strong dependence of the morphology and wettability of CaCO3 precipitations on these factors. Higher MS concentration and temperature contribute to enhanced hydrophilicity of CaCO3 coatings due to the increased surface roughness. The water flux of MICP-coated SSMs decreases with the increase of BS concentration, MS concentration, and temperature. The MICP-coated SSM obtained with MS concentration of 0.15 M, BS concentration of 0.1 × 108 cells/mL, and mineralization reaction at 25 ℃ for 24 hours demonstrated the optimal comprehensive performance, exhibiting underwater superoleophobicity with an underwater oil contact angle (UWOCA) exceeding 151°, an ultra-high oil intrusion pressure (> 3.0 kPa), ultrahigh flux (28,644 L m−2 h−1), and a preferable oil rejection rate (> 99.9%). Additionally, the as-prepared mesh exhibited superior anti-oil-fouling property and reusability, while concurrently demonstrating excellent chemical and thermal stability. This work contributes to advancing our knowledge of the influence of various environmental factors on the wetting characteristics of MICP and provides a feasible solution for the highly efficient and low-cost preparation of oil-water separation membranes based on the MICP process.

High flux durability underwater superoleophobic mesh modified by poly (maleic acid mono-(2-(dimethylamino)-ethyl ester-co-hydroxyethyl acrylate) and nanosilica particles hybrid

It is difficult to separate oil-polluted water mixtures, which has been considered a global problem. In this study, a simple dip-coating process was used to produce a stainless-steel mesh coated with poly (malaic acid mono-(2-(dimethylamino)-ethyl ester-co-hydroxyethyl acrylate)-tetraethyl orthosilicate-silica (P(MDME-co-HEA)-TEOS-SiO2). The membrane’s shape, chemical composition, separation capabilities, and mechanical properties were carefully examined. The membrane was extremely hydrophilic and extremely oil-phobic underwater due to its rough surface structure and hydrophilic chemical composition. For petroleum ether/water mixture, the separation flux of the membrane reached 224,600 l·m−2·h−1, with a 99.96% separation efficiency. The coated mesh also presented outstanding anti-oil fouling performance. Moreover, it exhibited excellent mechanical resistance and chemical stability.

A durable Ni3S2 coated mesh with reversible transition between superhydrophobicity and underwater superoleophobicity for efficient oil-water separation

Oil leakage and the discharge of industrial oil/water mixtures have posed a serious threat to the water environment and ecosystem. With the purpose of tackling this issue, a Ni3S2 coated mesh with switchable wettability was fabricated for efficient oil-water separation. Surface morphology and chemical compositions of the coated mesh were characterized to analyze the formation mechanism and their influence on surface wettability. The reversible transition between superhydrophobicity and underwater superoleophobicity allows the coated mesh to selectively separate heavy or light oil under gravity, respectively. A T-shaped tube with a superhydrophobic mesh and an underwater superoleophobic mesh was proposed to overcome the limitation of oil density and the conventionally necessary intrusion pressure to achieve continuous and efficient separation. This system functioned well in separating complex mixtures including oil-hot water mixtures and oil-in-water emulsions. Therefore, this Ni3S2 nanorods grown on stainless steel mesh present a promising solution towards oily water treatment.

Underwater superoleophobic mesh with robust Anthurium andraeanum-like attapulgite coating layer for effective oil spill recovery

It is highly desired to develop an efficient and stable approach to recover water from oil-water mixtures. In this work, we reported the facile fabrication of superhydrophilic and underwater superoleophobic membranes by coating a layer of Anthurium andraeanum-like attapulgite (ARATP) on commercially available wire meshes via sintering. The ARATP was obtained through anchoring nano-Fe3O4 on attapulgite (ATP), and its micro nano-structures can be adjusted by varying Fe3O4 content. Molecular dynamic simulations revealed the benefits of Fe3O4 in constructing superwetting coating layer with oil droplet repulsion larger than 227 KJ·mol−1. The membrane exhibited underwater superoleophobicity (with underwater oil contact angle at 157°) and was proven to treat various oil-water mixtures effectively (with a water permeation flux above 3249 L·m−2·h−1 and oil content in filtrate less than 2 mg·L−1). Furthermore, the chemical, mechanical stability and easy-cleaning property of the as-prepared membrane was demonstrated by different tests.

Synergistic effect of nano-silica and eco-friendly hydrogel for the cost-effective and highly efficient oil-water separation

Reported herein is a novel eco-friendly and low-cost oil-water separation mesh that can achieve a high separation efficiency up to 99%, while the prepared mesh maintained excellent performance even after immersion in salty water for 5 days, or cycle use for 20 times. The superhydrophilic and underwater superoleophobic mesh was modified with a layer of rough nano silica by soot template method firstly, and then the mesh was covered with the calcium alginate hydrogel coating via a simple dip-coating method. The synergistic effect of the low-cost nano-silica and environmentally friendly calcium alginate hydrogel not only endowed the mesh with outstanding oil-water separation performance but also overcame the shortcoming of high-cost and pollutive in the fabrication of oil-water separation materials. The prepared mesh maintained excellent oil-water separation efficiency and water permeation flux, even after treatment in various harsh environments. The cost-effective and eco-friendly oil-water separation mesh holds great potential in the treatment of industrial and domestic waste oil.

Fabrication of superhydrophilic and underwater superoleophobic CuxO/TiO2 mesh for oil–water separation

Superhydrophilic and underwater superoleophobic meshes were fabricated for oil–water separation applications. High purity copper (Cu) meshes were anodized to produce a mixed-phase copper oxide (CuxO) layer. Titanium dioxide (TiO2) films were grown on the CuxO meshes via reactive sputter deposition in an admixture of argon and oxygen plasma followed by heat treatment. The CuxO/TiO2 meshes exhibited superhydrophilicity through the complete wetting of water in air. When the meshes were submerged underwater, the superoleophobic property was revealed using a mineral oil droplet with a contact angle of up to 151°. Separation of mineral oil from water (1:1 v/v) using the CuxO/TiO2 meshes was demonstrated using a custom-built separator. Chemical oxygen demand (COD) concentration measurement of the filtrates showed a decrease from 350 mg O2/L using a Cu mesh only to 84 mg O2/L using the CuxO/TiO2 mesh. Visible-light sensitivity was realized with the coupling of CuxO with TiO2. When the meshes were exposed to simulated solar light, self-cleaning property of the composite was activated. The visible-light irradiation of the used mesh exposed for at least 30 min degraded the residual oil thereby restoring the superhydrophilic property of the surface. The restoration would allow reusability of the CuxO/TiO2 meshes. After visible-light-induced cleaning of the mesh and reusing the mesh with a fresh oil–water sample, the COD of the filtrate was 86 mg O2/L.

Micro/Nanoscale Structured Superhydrophilic and Underwater Superoleophobic Hybrid-Coated Mesh for High-Efficiency Oil/Water Separation.

A novel micro/nanoscale rough structured superhydrophilic hybrid-coated mesh that shows underwater superoleophobic behavior is fabricated by spray casting or dipping nanoparticle–polymer suspensions on stainless steel mesh substrates. Water droplets can spread over the mesh completely; meanwhile, oil droplets can roll off the mesh at low tilt angles without any penetration. Besides overcoming the oil-fouling problem of many superhydrophilic coatings, this superhydrophilic and underwater superoleophobic mesh can be used to separate oil and water. The simple method used here to prepare the organic–inorganic hybrid coatings successfully produced controllable micro-nano binary roughness and also achieved a rough topography of micro-nano binary structure by controlling the content of inorganic particles. The mechanism of oil–water separation by the superhydrophilic and superoleophobic membrane is rationalized by considering capillary mechanics. Tetraethyl orathosilicate (TEOS) as a base was used to prepare the nano-SiO2 solution as a nano-dopant through a sol-gel process, while polyvinyl alcohol (PVA) was used as the film binder and glutaraldehyde as the cross-linking agent; the mixture was dip-coated on the surface of 300-mesh stainless steel mesh to form superhydrophilic and underwater superoleophobic film. Properties of nano-SiO2 represented by infrared spectroscopy and surface topography of the film observed under scanning electron microscope (SEM) indicated that the film surface had a coarse micro–nano binary structure; the effect of nano-SiO2 doping amount on the film’s surface topography and the effect of such surface topography on hydrophilicity of the film were studied; contact angle of water on such surface was tested as 0° by the surface contact angle tester and spread quickly; the underwater contact angle to oil was 158°, showing superhydrophilic and underwater superoleophobic properties. The effect of the dosing amount of cross-linking agent to the waterproof swelling property and the permeate flux of the film were studied; the oil–water separation effect of the film to oil–water suspension and oil–water emulsion was studied too, and in both cases the separation efficiency reached 99%, which finally reduced the oil content to be lower than 50 mg/L. The effect of filtration times to permeate flux was studied, and it was found that the more hydrophilic the film was, the stronger the stain resistance would be, and the permeate flux would gradually decrease along with the increase of filtration times.

NiCo2O4 hierarchical structure coated mesh with long-term stable underwater superoleophobicity for high-efficient, high-flux oil-water separation

NiCo2O4 structure coated stainless steel mesh has been successfully fabricated via a facile hydrothermal-calcination method. The combination of the hierarchical NiCo2O4 structure and high hydrophilicity contributed to the superhydrophilic and underwater superoleophobic mesh. The NiCo2O4 coated mesh could be used to separate various oil-water mixtures with a efficiency exceeding 99.9% and a water flux above 11,600 L·m−2·h−1. Furthermore, the NiCo2O4 coated mesh shows good mechanical durability, chemical stability under weak acid, base and simulated seawater solution and long-term storage stability in ambient atmosphere. Given high separation efficiency and flux, excellent stability and simple fabrication process, the NiCo2O4 coated mesh is promising in the field of oily sewage treatment.

Calcium ions enhanced mussel-inspired underwater superoleophobic coating with superior mechanical stability and hot water repellence for efficient oil/water separation

The presented study proposed a simple, eco-friendly, and inexpensive route for improvement in mechanical robustness and hot solutions resistance of underwater superoleophobic mesh. The robustly underwater superoleophobic mesh was fabricated by introducing polydopamine (PDA)-calcium (Ca) complex aggregations to form hierarchical micro/nano-structures on the mesh surface. The wettability, appearance, roughness, and chemical composition of the obtained mesh were investigated. The generated coating reveals ultralow underwater oil adhesion and superior resistance to ultraviolet irradiation, hot water, oils, mechanical abrasion and folding. Moreover, the fabricated mesh can separate all sorts of oil/hot (95 ℃) water mixtures with high efficiencies (>97.8%) and satisfactory oil intrusion pressure. Especially, the decorated mesh can maintain high efficiency (>98.2%) after the separation of 80 cycles to oil/hot water mixtures, showing outstanding stability. Besides, the developed mesh can be applied as a separation material for gravity driven penetration of corrosive water from oil with high efficiency (>97%). We believe that the fabricated mesh with good stability and excellent separation performance has great potential to solve large-scale water contamination resulted from oil leaking accidents and oily water emission.

Eco-friendly and scratch-resistant hybrid coating on mesh for gravity-driven oil/water separation

Abstract Oil/water separation by the membranes with unique wetting behavior has been widely reported. Unfortunately, many approaches can cause secondary contamination because of the use of toxic solvents and coating materials. In this work, a new type of underwater superoleophobic mesh with natural attapulgite nanorods (APT) coating was successfully constructed via an eco-friendly bioadhesion method. The decorated mesh possesses satisfactory superoleophobicity not only in its initial state, but after being treated by highly corrosive aqueous solutions containing acid, alkaline or salt as well as strongly mechanical scraping. The mesh prewetted with water is able to filtrate a series of the mixtures of light oil and water with the separation efficiency over 97.5%. It is also demonstrated that the mesh has good recyclability and quick separation rate in oil/water separation. Especially, a gravity driven oil/water filtration for the oils in hot (90 °C) acidic, caustic and salty water environments can be achieved using the as-constructed mesh, and the separation efficiencies are more than 97.8%. Because of facile and eco-friendly preparation process as well as durably underwater superoleophobicity, the decorated mesh is potentially useful in the treatment of oily wastewater.

Environmentally benign development of superhydrophilic and underwater superoleophobic mesh for effective oil/water separation

Superhydrophilic and underwater superoleophobic materials for oil/water separation have recently attracted much attention due to the urgent needs of water protection. However, the environmental problems, complex preparation process and poor stabilities seriously restricted the practical applications. Herein, a waterborne organic–inorganic composite coating was prepared by mechanical mixing a silicone acrylic emulsion with nano-silica particles. The silica particles could be introduced to polymeric latexes to generate the cross-linked structure due to the polycondensation between hydroxyl groups. A simple spray technique was applied to deposit the as-prepared composite coating on a stainless steel mesh which exhibited a favourable superhydrophilicity (nearly 0°) and underwater superoleophobicity (above 155°) towards various oil droplets. The coated mesh presented a high separation efficiency of above 99% towards a series of light oil–water mixtures and it also showed a good recyclability after 30 separation cycles. Furthermore, the coated mesh kept excellent underwater superoleophobicity under a series of pH solutions and immersion tests in water and 3.5 wt% NaCl solution. Therefore, the as-prepared mesh is highlighted in its simple and environmental fabrication, high separation efficiency, good recyclability, excellent chemical stability and water resistance, exhibiting a bright prospect for scalable production.

Graphene oxide coated meshes with stable underwater superoleophobicity and anti-oil-fouling property for highly efficient oil/water separation

Developing underwater superoleophobic filtration materials with robust stability and excellent anti-oil-fouling performance in harsh environments is desired for high efficiency oil/water separation. In this work, irregular hydrophilic graphene oxide (GO) was adopted as a coating material to modify oxidized copper mesh with desired hierarchical surface roughness and hydrophilic composition through a novel in situ copper ion induced crosslinking method. The combination of microscale copper wires and nanoscale hydrophilic GO sheets endowed the resultant GO coated oxidized copper mesh (GO@CuO) with unique underwater superoleophobicity and excellent anti-oil-fouling property. Moreover, the mesh exhibited excellent stability in corrosive solutions with no apparent variations in wetting properties, indicating its good stability. The as-prepared GO@CuO mesh can be applied to separate oil/water mixtures with high efficiency (>99.49%) and good reusability. Due to the excellent anti-oil-fouling property, high separation efficiency, and good stability, the as-prepared underwater superoleophobic mesh could find broad applications in oil/water separations.

3D Printing of an Oil/Water Mixture Separator with In Situ Demulsification and Separation.

Currently, many meshes, membranes, and fabrics with extreme wettability of superhydrophobicity/superoleophilicity, or superhydrophilicity and underwater superoleophobicity are promising candidates for oil/water mixture separation. Nevertheless, a facile yet effective way to design and fabricate porous mesh still remains challenging. In this work, fused deposition modeling (FDM) 3D printing of Fe/polylactic acid (PLA) composites was employed to fabricate superhydrophilic and underwater superoleophobic mesh (S-USM) with hydrogel coatings via the surface polymerization of Fe(II)-mediated redox reaction. In addition, salt of aluminum chloride was incorporated within the hydrogel coating, which was attributed to strengthening the demulsification of oil-in-water emulsions, resulting in efficient separation of oil-in-water mixtures. The S-USM was efficient for a wide range of oil-in-water mixtures, such as dodecane, diesel, vegetable oil, and even crude oil, with a separation efficiency of up to 85%. In this study, the flexible design and fabrication of 3D printing were used for the facile creation of spherical oil skimmers with hydrogel coatings that were capable of removing the floating oil. Most importantly, this work is expected to promote post-treatment processes using 3D printing as a new manufacturing technology and, in this way, a series of devices of specific shape and function will be expanded to satisfy desired requirements and bring great convenience to personal life.

Facile preparation of superhydrophilic and underwater superoleophobic mesh for oil/water separation in harsh environments

An effective solution to separate oil and water is urgently needed owing to the increasingly serious problem of oil pollution. Numerous studies have been done to endow ordinary materials with extreme wettability for oil/water separation. Unfortunately, most of these materials cannot work in harsh environments, resulting in the low stability and practicability in practice. Herein, a facile method was proposed to fabricate superhydrophilic and underwater superoleophobic mesh by immersing ordinary mesh in a mixture of sulfuric acid (H2SO4) and chromium trioxide (CrO3). After immersing for just 1 min, the mesh was endowed with superhydrophilicity (CA = 0°) and underwater superoleophobicity (hexane CA = 151°, SA = 14°). Increasing the immersion time to 3 min, the prepared mesh exhibited better superoleophobicity. A separation device was developed based on the prepared mesh and the separation efficiencies for diverse oil/water mixtures containing acid, alkaline, salt and hot water were above 95%. The device retained a high efficiency after being reused for 20 times and the prepared mesh maintained superoleophobicity after immersing underwater for 72 h and abrasion test of 100 cycles. This oil/water separation method is easy-to-use, inexpensive, power-free and it can be used to separate caustic oil/water mixtures.

High-Flux and Robust Co3O4 Mesh for Efficient Oil/Water Separation in Harsh Environment.

Material with special wettability for oil/water separation has drawn more and more attention, since the oil spill accidents and industrial processing are growing in frequency and in volume. A superhydrophilic and underwater superoleophobic mesh was prepared by introducing Co3O4 on a stainless steel mesh, through a simple hydrothermal process and subsequent calcination. The as-prepared Co3O4 mesh can not only separate various oil/water mixtures with high efficiency and high flux, but also work effectively in harsh environment such as highly acidic, alkaline, and salty solutions. Moreover, the Co3O4 mesh can still retain good separation performance after 40 abrasion cycles with sandpaper. The outstanding anticorrosion and antiabrasion behaviors make the Co3O4 mesh promising for oil/water separation even in harsh environment.

Efficient oil/water separation by a durable underwater superoleophobic mesh membrane with TiO2 coating via biomineralization

In this work, a novel and facile method was used to coat a uniform and conformal TiO2 film on a stainless steel mesh via polyethylenimine-catalyzed biomineralization of titanium bis(ammonium lactato)dihydroxide at neutral pH, ambient temperature and pressure. The fabricated mesh showed excellent superhydrophilicity and underwater superoleophobicity. It separated immiscible oil/water mixtures by gravity at a high flux (∼3 × 104 L m−2 h−1), high separation efficiency (∼99.999%), and exhibited excellent anti-oil-fouling ability. The mesh also demonstrated great durability: (1) it had outstanding stability in 1 M NaCl, 0.1 M HCl, 0.1 M NaOH solutions, and absolute ethanol; (2) it maintained underwater superoleophobicity in solutions of pH from 1 to 13 and saturated NaCl solutions; and (3) the separation efficiency was retained after high temperature treatment and mechanical wear tests (sonication, abrasion and crumpling). The biomineralization coating method was also applied on other substrates (nonwoven mesh, filter paper and PVDF membrane), which also showed good capability for oil/water separation. Therefore, this new environmentally benign approach of preparing superwetting surfaces provides a durable and sustainable solution to the treatment of oily wastewater.

Surface chemistry-dominated underwater superoleophobic mesh with mussel-inspired zwitterionic coatings for oil/water separation and self-cleaning

Mussel-inspired surface modification has been received great attention due to the universal adhesive properties of catechols for fabrication of multifunctional coatings, especially for gluing hydrophilic polymers to fabricate underwater-superoleophobic materials utilizing in oil/water separation. Despite the extensive research carried out on this topic, the similarity and discrepancy between catecholamine and catecholic amino acid on surface modification and post functionalization have not been fully addressed yet. In this work, underwater superoleophobic surfaces have been successfully developed by a two-step dip-coating method with mussel-inspired coatings and subsequent zwitterionic sulfobetaine methacrylate (SBMA) grafting onto stainless steel meshes and used in oil/water separation. Here, dopamine and 3,4-dihydroxy-L-phenylalanine were both served as mussel-adhesives. More specifically, small molecule zwitterion rather than polyzwitterion was functionalized onto mussel-inspired coatings to minimize the effect of surface topography on surface wettability. The modified surfaces were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements to observe the surface morphology, estimate the surface roughness, and evaluate the wettability, respectively. It showed that SBMA modified meshes with polydopamine (PDA) or poly(3,4-dihydroxy-L-phenylalanine) (PDOPA) layer possessed quite different surface roughness, while both presented excellent oil repellency in water with underwater oil contact angles of 153°–160°, indicating a less dependence on surface roughness. Although by using the small molecule as the hydrophilic functionalized groups, the as-prepared meshes exhibited good self-cleaning and oil/water separation performance (separation efficiency >98% for hexane and >97% for soybean oil) and outstanding recyclability with 98% separation efficiency after 30 cycles. This method provides insight into different properties of polycatechols and simplifies the fabrication process through the use of small molecule zwitterion rather than zwitterionic polymer. Besides, the modified meshes also exhibited excellent stability for long-term use. The resulting underwater superoleophobicity and robust self-cleaning ability promise an ideal candidate for oil/water separation and oil contamination restriction.

A pair of MnO2 nanocrystal coatings with inverse wettability on metal meshes for efficient oil/water separation

Water contamination arising oil spill and industrial oily wastewater discharge has posed a severe threat to ecological environment and human health. To address the issues, the metal meshes with superwetting performance for selective oil/water separation have received extensive attention. But, it is still a great challenge to fabricate durable meshes with special wettability and high liquid intrusion pressure, which can be utilized for oil/water separation under harsh environments. Herein, two types of MnO2 nanocrystal coated meshes with inverse wettability, namely superhydrophobicity and underwater superoleophobicity, were fabricated via a single hydrothermal strategy or combining dipping modification. The resulting superhydrophobic mesh and underwater superoleophobic mesh are suitable for removing heavy oil and light oil from water, respectively. The oil/water separation efficiencies of greater than 96.2% are achieved for the two meshes. Importantly, both meshes exhibit quick separation rate for the permeable liquid and high intrusion pressure (>1.38 kPa) for the intercepted liquid, and can maintain excellent superwetting performance and high oil/water separation efficiency under harsh environments (acidic, alkakine and high-concentration salt solutions). We believe the as-fabricated meshes are promising and effective filters for purifying oil-polluted water.

ZrO2-coated stainless steel mesh with underwater superoleophobicity by electrophoretic deposition for durable oil/water separation

Underwater superoleophobic mesh has been broadly investigated but its mechanical durability was seldom mentioned. Thus, in this work a ZrO2-coated stainless steel mesh was prepared for durable oil/water separation by an electrophoretic deposition method using ZrO2 sol as electrolyte. The ZrO2 coating is of hierarchical structure, making the Z-SSM superhydrophilic in air and superoleophobic underwater. The mesh exhibited outstanding separation efficiency of above 97.5% for various oil/water mixtures. The separation efficiency of n-hexane/water mixture maintained over 98% after 50 times of recycle separation. Moreover, the coated mesh maintained high separation efficiency after 30 cycles of abrasion, showing good stability.

Matchstick-Like Cu2S@CuxO Nanowire Film: Transition of Superhydrophilicity to Superhydrophobicity

We fabricated a matchstick-like Cu2S@CuxO nanowire film on copper mesh by applying a Cu(OH)2 nanowires template-sacrificial method, which can transformed from superhydrophilic to superhydrophobic just after storage in air for a certain period without any further organic modification. The surface morphology, chemical composition and the wettability were investigated by Scanning Electron Microscopy (SEM), X-ray diffractometer (XRD), Raman, X-ray Photoelectron Microscopy (XPS), and contact angle measurement. Results showed that the change of surface chemical composition and the trapped air among the matchstick-like structures were the decisive factors for the wettability transition. Therefore, on-demand oil/water separation was achieved, which was performed by using the superhydrophilic–underwater superoleophobic mesh for separating light oil/water mixtures and the superhydrophobic one for separating heavy oil/water mixtures.