Gravity-driven Oil-water Separation Research Articles

Foldable, Stretchable, Superelastic, and Tunable Wettability Aramid Nanofiber Aerogels for Efficient Thermal Insulation and Oil-Water Separation.

Aerogels hold great potential in thermal insulation, catalytic supports, adsorption, and separation, due to their low density, high porosity, and low thermal conductivity. However, their inherent mechanical fragility and limited control functionality pose substantial challenges that hinder their practical use. In this study, a strategy is developed for the fabrication of cross-linked aramid nanofiber aerogels (cANFAs) by combining internanofiber surface cross-linking with ice-templating techniques. This approach enables the production of cANFAs with an ultralow density of 6.3 mg/cm3 while exhibiting robust mechanical properties, including exceptional mechanical resilience, withstanding 90% compression in air and 80% compression underwater for 100 cycles, and high stretchability with a tensile strain of 34%. The cANFAs demonstrate remarkable thermal insulation properties, with low thermal conductivities of 0.03816 W/(m·K) at room temperature and 0.03518 W/(m·K) at -40 °C. Additionally, the cANFAs exhibit tunable wettability, being hydrophilic and oleophilic in air while becoming superhydrophobic underwater, which enables efficient gravity-driven oil-water separation performance. This study presents a promising route to create robust and functional aramid nanofiber aerogels for practical applications across various fields.

Novel conductive Janus membranes with water diode effect assisted by an electrostatic field for efficient mass transfer and oil-water separation

Novel conductive Janus membranes with water diode effect assisted by an electrostatic field for efficient mass transfer and oil-water separation

Enhanced superhydrophobic melamine sponge with bimetal organic framework for simultaneous oil-water separation and microplastic removal

Enhanced superhydrophobic melamine sponge with bimetal organic framework for simultaneous oil-water separation and microplastic removal

Tune wastepaper to hydrophobic membranes through metal-ion-induced lignocellulose nanofibril crosslinking for oil-water separation

Tune wastepaper to hydrophobic membranes through metal-ion-induced lignocellulose nanofibril crosslinking for oil-water separation

Facile fabrication of super-wettable mesh membrane using locally-synthesized cobalt oxide nanoparticles and their application in efficient gravity driven oil/water separation

Facile fabrication of super-wettable mesh membrane using locally-synthesized cobalt oxide nanoparticles and their application in efficient gravity driven oil/water separation

Application of Superhydrophobic Mesh Coated by PDMS/TiO2 Nanocomposites for Oil/Water Separation.

Superhydrophobic materials have recently attracted great interest from both academia and industry due to their promising applications in self-cleaning, oil-water separation, etc. Here, we developed a facile method to prepare hybrid PDMS/TiO2 fiber for superhydrophobic coatings. TiO2 could be uniformly distributed into PDMS, forming a hierarchical micro/nano structure on the surface of the substrate. The contact angle of the superhydrophobic coating could reach as high as 155°. The superhydrophobic coating possessed good self-cleaning performance, corrosion resistance, and durability. It was found that gravity-driven oil-water separation was achieved using stainless steel mesh coated with the PDMS/TiO2 coating. More importantly, the coated filter paper could not only separate oil and pure water but also corrosive solutions, including the salt, acid, and alkali solution.

Mg-calcite CaCO3 particle: Rapid synthesis and application in fabrication of environmentally friendly hydrophobic polyurethane sponge for oil–water separation

The hydrophobic modification of polyurethane (PU) sponge is attracting considerable attention in the field of oil–water separation. A hydrophobic PU sponge with microsize cavities on the skeleton surface and interior was prepared with hierarchical structural Mg-calcite CaCO 3 (MCC) particles as a template. Hydrophobic-modified MCC particles with controllable morphologies were firstly synthesized by a facile and rapid batch method under high-speed stirring for 1 min by the presence of cetyltrimethyl ammonium bromide. MCC particles were then blended into the starting foaming materials to fabricate hydrophobic PU/MCC sponge by in-situ polymerization method. Finally, MCC particles of PU/MCC sponge were etched by acid solution and microsize cavities were generated on the surface and interior of EPU/MCC sponge skeleton. The oil-adsorption capacity of obtained hydrophobic EPU/MCC sponge was 7.58 and 5.31 times higher than pristine PU sponge for engine oil and sunflower oil, respectively. This could be attributed to the microsize cavities on the skeleton surface and interior which would increase the skeleton flexibility and enhance adhesion level between the oil and sponge surface. The underwater CCl 4 was completely adsorbed into the EPU/MCC sponge within 1 s, indicating its high adsorption speed. EPU/MCC sponge exhibited high separation selectivity and separation efficiency in gravity-driven oil-water separation. The results could provide a strategy to develop hydrophobic sponges with excellent oil-water separation property. • Rapid and shape-controlled synthesis of Mg-calcite CaCO 3 (MCC) particle is developed. • Hydrophobic PU/MCC sponge was fabricated by in-situ polymerization method. • Micro-cavities were generated on PU sponge skeleton by etching MCC particles. • Micro-cavities on sponge skeleton dramatically enhanced the oil adsorption performance.

Facile fabrication of 2D MOF-Based membrane with hierarchical structures for ultrafast Oil-Water separation

• 2D Cu-CAT-1 was directly grown on copper mesh by one-step electrochemistry method. • Cu-CAT-1@CM membrane with unique hierarchical structures shows extreme wettability. • The membrane exhibits ultrafast permeation flux and high separation efficiency for various oil–water mixtures. • The membrane shows robust recovery ability and high acid/alkaline stability. The surface chemical composition and building unit structures of membrane are the key factors to realize highly-efficient oil–water separation. Here we report the synthesis of Cu-CAT-1 metal–organic frameworks (MOFs) with unique two-dimensional (2D) hierarchical structures grown directly on copper mesh (Cu-CAT-1@CM) for oil–water separation. The Cu-CAT-1@CM membrane with micro/nano- architecture exhibits robust superhydrophilicity and underwater superoleophobicity characteristics, allowing gravity-driven oil–water separation by achieving ultrahigh flux up to 329 kL∙m −2 ∙h −1 . The membrane shows excellent separation performances by testing various oils, particularly actual crude oil and xylene, which are considered as the notorious pollutants in the water. The residual oil contents of six samples are all less than 24.6 mg∙L -1 . The mechanism analysis demonstrated that the appropriate hierarchical structures of the membrane surface is the code for the extreme wettability that remarkably improved the separation efficiency. Moreover, such a membrane with high performance can be readily synthesized by electrochemical method at room temperature in only 20 min, which shows the advantages of facile and environmentally friendly fabrication process as well as low cost. Overall, the membrane with energy-saving of gravity-driven and ultra-high permeability allows the rapid separation of oil–water mixture, showing the potential applications for resolving the problem of oil pollution.

Nanosecond laser induced glass particle deposition over steel mesh for long-term superhydrophilicity and gravity driven oil water separation

In this report we show that the laser textured stainless steel meshes which serve as excellent oil water separator immediately after laser processing, lose their oil water separation capability after storage in ambient air. This was possibly due to the reactive nature of the metal oxides formed during laser processing which resulted in transition of the wettability of processed metallic meshes from superhydrophilic to superhydrophobic during storage. To overcome this issue, we show that by using a glass cover plate over the metal mesh during laser processing, micron/submicron sized glass particles can be deposited on to the mesh via a process known as laser induced plasma assisted ablation. Since the glass is inherently hydrophilic and inert, and therefore the glass particles coating produced a stable superhydrophilic/underwater-superoleophobic surface which was observed to maintain its superhydrophilicity for the tested duration of ~8 months and perform oil/water separation with an efficiency of ~96% for various oils. Further, the glass particles coated mesh was found to sustain several cycles of sandpaper abrasion before losing its oil water separation capability. • Laser textured metal mesh undergo wettability transition due to aging. • Such wettability transition renders the mesh unusable for oil water separation. • Use of a top glass plate during laser processing addresses the issue. • Mesh gets covered with glass particles which provide stable wettability. • Prepared mesh performs efficient oil water separation even after 8 months of storage.

One-step synthesis of a steel-polymer wool for oil-water separation and absorption

Methods for the efficient and affordable remediation of oil spills and chemical leaks are crucially needed in today’s environment. In this study, we have developed a simple, magnetic, porous material based on polydimethylsiloxane (PDMS) and steel wool (SW) that can fulfill these needs. The PDMS-SW presented here is superhydrophobic, superoleophilic, and capable of absorbing and separating oils and organic solvents from water. The material is mechanically and chemically stable, even in salty environments, and can be magnetically guided. It exhibits good selectivity, recyclability, and sorption capacity, and can quickly and continuously absorb and remove large amounts of oils and organic solutions from stationary and turbulent water. In addition, PDMS-SW’s inherently high porosity enables direct, gravity-driven oil-water separation with permeate flux as high as ~32,000 L/m2·h and separation efficiency over 99%. The solution immersion process used to prepare the material is easily scalable and requires only a single step. Thus, with its demonstrated combination of affordability, efficiency, and ease of use, PDMS-SW has the potential to meet the demands of large-area oil and chemical clean-ups.

Electrospun frogspawn structured membrane for gravity-driven oil-water separation

The aim of this study is to prepare a fibrous membrane scaffold that possesses a frogspawn structure for high-efficiency oil-water separation. Polyamic acid was first electrospun onto a rotating wheel-collector to obtain the fibrous membrane. Subsequently, post-processing by immersion in a polydimethylsiloxane solution and a silica nanoparticles suspension, followed by a thermal treatment generated a frogspawn-structured fibrous membrane. The obtained membrane achieved superhydrophobicity and superoleophilicity, with the water contact angle as high as 155.75° and the oil contact angle lower than 10°. The separation efficiencies of the membrane were higher than 99.55% and the permeate flux was maintained at greater than 4400 L/m2∙h after 20 separation cycles. Additionally, the wettability studies suggested the membrane exhibits high stability because it can resist damages due to high temperature (150 °C), acid/basic conditions and organic/inorganic solvents. These findings indicated that this composite membrane has great potential for use in gravity-driven oil-water separation and can extend the range of its application for treatments of oil spills incident, oily wastewater and spent liquor.

Pouring‐type gravity‐driven oil–water separation without water bridge

Oil pollution brings great challenge to environmental protection. Utilising oil-water separation device to separate and recycle oils is an environment-friendly approach to dispose mixtures containing oils. Pouring-type gravity-driven oil-water separation method based on extremely wettable materials is an interesting area of research because of its high separation velocity, selectivity and purity. However, the presence of water bridge results in low separation efficiency. Herein, the authors first synthesised a facile etching method and a dipcoating method to fabricate contrary extreme wettability sponges including superhydrophilic-underwater-superoleophobic (SHI-U-SOO) sponge and superhydrophobic-superoleophilic (SHO-SOI) sponge. Accordingly, they designed a three-way oil-water separation system whose left and right bottom tubes were installed with the SHI-U-SOO sponge and the SHO-SOI sponge, respectively. Water and oil separately flow out from the left and right tubes, thereby eliminating the water bridge and increasing separation efficiency, and still having ideal separation selectivity and separation purity. The developed three-way oil-water separation system has promising application prospects in disposing oil spills, oil leakage from factories and industrial effluents.

Modified metal mesh with bipolar wettability for rapid and gravity-driven oil-water separation and oil collection

Abstract Oil contamination from oilfield geothermal water severely restricts the efficient utilization of geothermal energy. Oil-water separation pretreatment via removing oil from water may provide a kind of possibility to mitigate the oil pollution problem. Stainless steel filtration mesh with bipolar wettability was successfully fabricated to attempt the gravity-driven separation of various oil-water mixtures. The highly hydrophilic mesh was prepared by liquid phase deposition of TiO2, and the hydrophobic mesh was realized via the subsequent modification of fluorosilane on highly hydrophilic mesh deposited by TiO2. Only with relatively small pore size, the highly hydrophilic mesh and the hydrophobic mesh were applicable for separating oil-water mixtures. Besides, microscopic morphologies, surface chemical compositions, contact angles, water wetting behaviors, water-holding capacities, abrasion test and oil collection were also investigated. In general, the modified mesh with bipolar wettability presents gravity-driven oil-water separation for various oil-water mixtures, which may have potential industry application value such as the pretreatment of oilfield geothermal water.

Wrinkled Graphene Monoliths as Superabsorbing Building Blocks for Superhydrophobic and Superhydrophilic Surfaces.

Superhydrophobic and superhydrophilic surfaces are of great interest because of a large range of applications, for example, as antifogging and self-cleaning coatings, as antibiofouling paints for boats, in metal refining, and for water-oil separation. An aqueous ink based on three-dimensional graphene monoliths (Gr) can be used for constructing both superhydrophobic and superhydrophilic surfaces on arbitrary substrates with different surficial structures from the meso- to the macroscale. The surface wettability of a Gr-coated surface mainly depends on which additional layers (air for a superhydrophobic surface and water for a superhydrophilic surface) are adsorbed on the surface of the graphene sheets. Switching a Gr-coated surface between being superhydrophobic and superhydrophilic can thus be easily achieved by drying and prewetting with ethanol. The Gr-based superhydrophobic membranes or films should have great potential as efficient separators for fast and gravity-driven oil-water separation.

Gravity-driven hybrid membrane for oleophobic-superhydrophilic oil-water separation and water purification by graphene.

We prepared a simple, low-cost membrane suitable for gravity-driven oil-water separation and water purification. Composite membranes with selective wettability were fabricated from a mixture of aqueous poly(diallyldimethylammonium chloride) solution, sodium perfluorooctanoate, and silica nanoparticles. Simply dip-coating a stainless steel mesh using this mixture produced the oil-water separator. The contact angles (CAs) of hexadecane and water on the prepared composite membranes were 95 ± 2° and 0°, respectively, showing the oleophobicity and superhydrophilicity of the membrane. In addition, a graphene plug was stacked below the membrane to remove water-soluble organics by adsorption. As a result, this multifunctional device not only separates hexadecane from water, but also purifies water by the permeation of the separated water through the graphene plug. Here, methylene blue (MB) was removed as a demonstration. Membranes were characterized by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy to elucidate the origin of their selective wettability.

Underwater superoleophobic graphene oxide coated meshes for the separation of oil and water.

Hydrophilic graphene oxide (GO) nanosheets can be easily coated onto stainless steel meshes. Compared to neat meshes, GO coated meshes become more hydrophilic in air and superoleophobic under water. Taking advantage of this completely opposite wettability, GO coated meshes were used for gravity-driven oil-water separation.