One-Step Coating toward Multifunctional Applications: Oil/Water Mixtures and Emulsions Separation and Contaminants Adsorption

Here, a method that can simultaneously separate oil/water mixtures and remove water-soluble contaminants has been developed. Various substrates with different pore size were coated by polydopamine and polyethylenepolyamine codeposition films. The as-prepared materials were superhydrophilic and under-water superoleophobic. The materials can separate a range of different oil/water mixtures (including immiscible oil/water mixtures and surfactant-stabilized emulsions) in a single unit operation, with >99.6% separation efficiency and high fluxes. Copper ion and methyl blue can be effectively absorbed from water when it permeates through the materials. This method can be applied on organic and inorganic substrates and used in preparing large-scale product. Therefore, the simple and facile method has excellent potential in practical application and creates a new field for oil/water separation materials with multifunctional applications

A Facile Solvent-Manipulated Mesh for Reversible Oil/Water Separation

A controllable oil/water separation mesh has been successfully developed and easily manipulated by immersion in a stearic acid ethanol solution and tetrahydrofuran with a very short period of time. The superhydrophilic and underwater superoleophobic mesh is first obtained via a one-step chemical oxidation and subsequently converts to superhydrophobic after it is immersed in an ethanol solution of stearic acid for 5 min. The surface wettability is regained to superhydrophilic quickly by immersion in tetrahydrofuran for 5 min. More importantly, the reversible superhydrophobic-and-superhydrophilic switching can be repeated multiple times with almost no visible morphology variation. Therefore, this approach provides potential application in controllable oil/water separation and opens up new perspectives in manipulation of various metallic oxide substrates

A Facile Solvent-Manipulated Mesh for Reversible Oil/Water Separation

A controllable oil/water separation mesh has been successfully developed and easily manipulated by immersion in a stearic acid ethanol solution and tetrahydrofuran with a very short period of time. The superhydrophilic and underwater superoleophobic mesh is first obtained via a one-step chemical oxidation and subsequently converts to superhydrophobic after it is immersed in an ethanol solution of stearic acid for 5 min. The surface wettability is regained to superhydrophilic quickly by immersion in tetrahydrofuran for 5 min. More importantly, the reversible superhydrophobic-and-superhydrophilic switching can be repeated multiple times with almost no visible morphology variation. Therefore, this approach provides potential application in controllable oil/water separation and opens up new perspectives in manipulation of various metallic oxide substrates

Mussel-Inspired Chemistry and Michael Addition Reaction for Efficient Oil/Water Separation

An oil/water separation mesh with high separation efficiency and intrusion pressure of water has been successfully developed by combining mussel-inspired chemistry and Michael addition reaction. The substrate of the stainless steel mesh was first coated with the adhesive polydopamine (PDA) film by simple immersion in an aqueous solution of dopamine at pH of 8.5. Then n-dodecyl mercaptan (NDM) was conjugated with PDA film through Michael addition reaction at ambient temperature. The as-prepared mesh showed highly hydrophobicity with the water contact angle of 144° and superoleophilicity with the oil contact angle of 0°. It can be used to separate a series of oil/water mixtures like gasoline, diesel, etc. The separation efficiency remains high after 30 times use (99.95% for hexane/water mixture). More importantly, the relatively high intrusion pressure (2.2 kPa) gives the opportunity to separation of large amount of oil and water mixtures. This study provides a new prospect to simply introduce multiple molecules on the adhesive PDA-based mesh to achieve various functional oil/water separation materials

Thermo and pH Dual-Responsive Materials for Controllable Oil/Water Separation

Thermo and pH dual-controllable oil/water separation materials are successfully fabricated by photo initiated free radical polymerization of dimethylamino ethyl methacrylate (DMAEMA). The PDMAEMA hydrogel coated mesh shows superhydrophilicity and underwater superoleophobicity at certain temperature and pH. Due to the double responsiveness of PDMAEMA hydrogel, the as-prepared mesh can selectively separate water from oil/water mixtures and make water and oil permeate through the mesh orderly and be collected separately by adjusting the temperature or pH. Water can pass through the as-prepared mesh under 55 °C (pH 7) and pH less than 13 (<i>T</i> = 25 °C) while oil is kept on the mesh. When the temperature is above 55 °C or pH is larger than 13, the water retention capacity of PDMAEMA hydrogel is significantly reduced and the swelling volume is decreased. Therefore, oil can permeate through the mesh and be collected in situ. Additionally, this material has excellent potential to be used in practical applications and has created a new field for water/oil separation in which the process can be diversified and more intelligent

Mercury Ion Responsive Wettability and Oil/Water Separation

A novel Hg²⁺ responsive oil/water separation mesh with poly­(acrylic acid) hydrogel coating is reported. The mesh can separate oil and water because of the superhydrophilicity of the poly­(acrylic acid) hydrogel coating on the mesh, and switch the wettability based on the chelation between Hg²⁺ and poly­(acrylic acid) . The reversible change in oil contact angle of as-prepared mesh is about 149° after immersion in Hg²⁺ solution. This mesh is an ideal candidate for oil-polluted water purification, especially for water that contains Hg²⁺ contaminant

One-Step Breaking and Separating Emulsion by Tungsten Oxide Coated Mesh

Tungsten oxide coated mesh has been fabricated by a simple and inexpensive method. This coated mesh has a dual structure on the surface, consisting of microscale “flower” and nanoscale acicular crystal as the “petal”. Combining the micro/nano structure of the surface and the native hydrophilic property of tungsten oxide, the coated mesh shows special wettability: superhydrophilic in air and superoleophobic under water. Because of the special wettability, such a mesh can be used to separate oil/water mixtures as well as emulsions. Attributed to the good water adsorption capacity of tungsten oxide, the abundant grooves of the micro/nanostructure, and the microsized pores of the surface, this coated mesh can accomplish the demulsification process and the separation process in one single-step, and no further post treatment is needed. As an “emulsion breaker and separator”, this kind of mesh gives another idea of emulsion separation, which has prospective application in industrial fields such as water treatment and petroleum refining

One-Step Breaking and Separating Emulsion by Tungsten Oxide Coated Mesh

Tungsten oxide coated mesh has been fabricated by a simple and inexpensive method. This coated mesh has a dual structure on the surface, consisting of microscale “flower” and nanoscale acicular crystal as the “petal”. Combining the micro/nano structure of the surface and the native hydrophilic property of tungsten oxide, the coated mesh shows special wettability: superhydrophilic in air and superoleophobic under water. Because of the special wettability, such a mesh can be used to separate oil/water mixtures as well as emulsions. Attributed to the good water adsorption capacity of tungsten oxide, the abundant grooves of the micro/nanostructure, and the microsized pores of the surface, this coated mesh can accomplish the demulsification process and the separation process in one single-step, and no further post treatment is needed. As an “emulsion breaker and separator”, this kind of mesh gives another idea of emulsion separation, which has prospective application in industrial fields such as water treatment and petroleum refining

Breathing Demulsification: A Three-Dimensional (3D) Free-Standing Superhydrophilic Sponge

A novel three-dimensional (3D) free-standing superhydrophilic sponge for industrial wastewater treatment was formed by combining chitosan and linear polyacrylamide (PAM). When the chitosan–PAM sponge is immersed into an oil-in-water emulsion, the milky white emulsion containing surfactant turns clear and clarified. Demulsification efficiency, capacity, and recyclability of this positively charged chitosan–PAM sponge to oil-in-water emulsions stabilized by different types of surfactants including anionic, nonionic, and cationic surfactants, has been investigated for further practical evaluation. A “breathing demulsification” mechanism is presented to explain this attractive demulsified process. The effective contact area between emulsion and sponge is increased by the microcomposite and nanocomposite hierarchical structure of the chitosan–PAM free-standing sponge. Then, interfacial interactions, size effect, and strain act as the driving force for the demulsification of the emulsified droplets at the surface of the sponge

Polyacrylamide-Polydivinylbenzene Decorated Membrane for Sundry Ionic Stabilized Emulsions Separation via a Facile Solvothermal Method

Aiming to solve the worldwide challenge of stabilized oil-in-water emulsion separation, a PAM-PDVB decorated nylon membrane is fabricated via a facile solvothermal route in our group. The main composition is PAM, while the PDVB plays a role as cross-linker in order to improve the interaction between the polymer and the substrate. By the combination of the superhydrophilic and underwater superoleophobic wettability of the PAM polymer with the micropore size of the substrate, the as-prepared material is able to achieve the separation of various stabilized oil-in-water emulsions including cationic type, nonionic type, and anionic type. Compared with previous works, the emulsions used in this case are more stable and can stay for several days. Besides, the solvothermal method is facile, cost saving, and relatively environmentally friendly in this experiment. Moreover, the PAM-PDVB modified membrane exhibits excellent pH stability, recyclability, and high separation efficiency (above 99%), which can be scaled up and used in the practical industrial field