Versatile Fabrication of Ultralight Magnetic Foams and Application for Oil–Water Separation

Ultralow-density (<10 mg cm^–3) materials have many important technological applications; however, most of them were fabricated using either expensive materials or complicated procedures. In this study, ultralight magnetic Fe₂O₃/C, Co/C, and Ni/C foams (with a density <5 mg cm^–3) were fabricated on the centimeter scale by pyrolyzing commercial polyurethane sponge grafted with polyelectrolyte layers based on the corresponding metal acrylate at 400 °C. The ultralight foams consisted of 3D interconnected hollow tubes that have a diameter of micrometer and nanoscale wall thickness, forming hierarchical structures from macroscopic to nanometer length scales. More interesting was that the wall thickness and morphology of the microtubes could be tuned by controlling the concentrations of acrylic acid and metallic cations. After modification with low-surface-energy polysiloxane, the ultralight foams showed superhydrophobicity and superoleophilicity, which quickly and selectively absorbed a variety of oils from a polluted water surface under magnetic field. The oil absorption capacity reached 100 times of the foams’ own weight, exhibiting one of the highest values among existing absorptive counterparts. By controlling the composition and conformation of the grafted polyelectrolyte layers, the present approach is extendable to fabricate a variety of ultralow-density materials desirable for absorptive materials, electrode materials, catalyst supports, <i>etc</i>

Three-Dimensionally Macroporous Fe/C Nanocomposites As Highly Selective Oil-Absorption Materials

In this study, three-dimensionally macroporous Fe/C nanocomposites were investigated as highly selective absorption materials for removing oils from water surface. The macroporous nanocomposites were synthesized by sintering a mixture of closely packed polystyrene microspheres and ferric nitrate precursor. These nanocomposites exhibited superhydrophobic and superoleophilic properties without the modification of low-surface-energy chemicals. And the pore size of the nanocomposites, which is crucial for the oil-absorption capacity, was tuned by varying the diameter of polystyrene microspheres. The macroporous nanocomposites fast and selectively absorbed a wide range of oils and hydrophobic organic solvents on water surface, and the removal of the absorbed oils from the water surface was readily achieved under a magnetic field. Moreover, the nanocomposites still kept highly hydrophobic and oleophilic characteristics after repeatedly removing oils from water surface for many cycles. Because of frequently occurring environmental pollution arising from oil spills and chemicals leakage, the results of this study might offer a kind of efficient and selective absorbent materials for removing oils and nonpolar organic solvents from the surface of water

Mussel-Inspired Direct Immobilization of Nanoparticles and Application for Oil–Water Separation

Immobilization of various nanoparticles onto complex 2D or 3D macroscopic surface is an important issue for nanotechnology, but the challenge remains to explore a facile, general and environmentally friendly method for achieving this goal. Taking inspiration from the adhesion of marine mussels, we reported here that oxide nanoparticles of different compositions and sizes were directly and robustly anchored on the surface of monolithic foams ranging from polymer to metals in an aqueous solution of dopamine. The effective immobilization of the nanoparticles was strongly dependent on the oxidation of dopamine, which could be tuned by either pH or by adding <i>n</i>-dodecanethiol. Interestingly, the thiol addition not only allowed the immobilization to take place in a wide pH range, but also led to superhydrophobicity of the resulting foams. Application of the superhydrophobic foams was illustrated by fast and selective collecting oils from water surface. Because catecholic derivatives exhibit high affinity to a variety of substances, the present strategy might be extendable to fabricate hybrid nanomaterials desirable for self-cleaning, environmental protection, sensors and catalysts, and so forth

Miniature Boats with Striking Loading Capacity Fabricated from Superhydrophobic Copper Meshes

A novel kind of miniature boat that might have many potential applications was fabricated from superhydrophobic copper meshes for the first time. These boats not only floated freely on a water surface but also exhibited striking loading capacities. By selection of the pore size of copper meshes, a loading capacity greater than 11.0 g could be readily achieved for a boat of 8.0 cm3 in volume. The large loading capacity is believed to arise from the air film surrounding the superhydrophobic surfaces of boats. The results of this study present new applications of artificial superhydrophobic surfaces in areas of miniature aquatic devices

Facile Removal and Collection of Oils from Water Surfaces through Superhydrophobic and Superoleophilic Sponges

The development of a convenient method for the removal (or collection) of oils and organic solvents from water surface is of great significance for water environmental protection, especially for the cleanup of oil spillage on seawater. A major challenge is the fabrication of an oil absorber with high absorption capacity, low cost, scalable fabrication, high selectivity, and excellent recyclability. In this paper, we present a simple method for the removal and collection of oils and organic solvents from the surfaces of water based on superhydrophobic and superoleophilic sponges that were fabricated by solution-immersion processes. The as-prepared sponges fast and selectively absorbed various kinds of oils up to above 13 times the sponges’ weight while completely repelling water through a combination of porous, superhydrophobic, and superoleophilic properties. More interesting, the absorbed oils were readily collected by a simple mechanical squeezing process, and the recovered sponges could be reused in oil–water separation for many cycles while still keeping high separation efficiency. The findings presented in this study might provide a fast and simple approach for the cleanup of oils and organic solvents on water surfaces

Intelligent Icephobic Surface toward Self-Deicing Capability

Superhydrophobic surfaces show attractive anti-icing properties. However, it remains a challenge for them to achieve icephobicity and ultralow ice adhesion in a humid environment, which is fundamentally attributed to the icing behavior on their hierarchical textures. Here, we address the issue by integrating a superhydrophobic copper mesh with an intelligent organogel that can secrete antifreezing agent autonomously in response to temperature. The antifreezing agent is composed of ethylene glycol and water. By autonomously secreting the antifreezing agent at subzero temperatures, the hybrid surface effectively inhibits the frosting process on the hierarchical texture of the superhydrophobic mesh. Consequently, the surface not only exhibits excellent antifrosting properties in a humid atmosphere but also repeatedly removes the ice deposited spontaneously due to ultralow ice adhesion (8 Pa). This integration of intelligent organogel paves a new and promising avenue to design superhydrophobic surfaces with excellent icephobic properties

Fast and Selective Removal of Oils from Water Surface via Highly Hydrophobic Core−Shell Fe₂O₃@C Nanoparticles under Magnetic Field

The removal of oil spills or organic contaminants from water surface is of great technological importance for environmental protection. A major challenge is the fast distribution and collection of absorbent materials with high separation selectivity, good thermal stability, and excellent recyclability. Here we reported fast and selective removal of oils from water surface through core−shell Fe2O3@C nanoparticles under magnetic field. These nanoparticles combined with unsinkable, highly hydrophobic and superoleophilic properties, could selectively absorb lubricating oil up to 3.8 times of the particles’ weight while completely repelling water. The oil-absorbed nanoparticles were quickly collected in seconds by applying an external magnetic field. More importantly, the oil could be readily removed from the surfaces of nanoparticles by a simple ultrasonic treatment whereas the particles still kept highly hydrophobic and superolephilic characteristics. Experiment results showed that the highly hydrophobic Fe2O3@C nanoparticles could be reused in water−oil separation for many cycles. Our results suggest a facile and efficient method that might find practical applications in the cleanup of oil spills and the removal of organic pollutants on water surface

Fast and Selective Removal of Oils from Water Surface via Highly Hydrophobic Core−Shell Fe₂O₃@C Nanoparticles under Magnetic Field

The removal of oil spills or organic contaminants from water surface is of great technological importance for environmental protection. A major challenge is the fast distribution and collection of absorbent materials with high separation selectivity, good thermal stability, and excellent recyclability. Here we reported fast and selective removal of oils from water surface through core−shell Fe2O3@C nanoparticles under magnetic field. These nanoparticles combined with unsinkable, highly hydrophobic and superoleophilic properties, could selectively absorb lubricating oil up to 3.8 times of the particles’ weight while completely repelling water. The oil-absorbed nanoparticles were quickly collected in seconds by applying an external magnetic field. More importantly, the oil could be readily removed from the surfaces of nanoparticles by a simple ultrasonic treatment whereas the particles still kept highly hydrophobic and superolephilic characteristics. Experiment results showed that the highly hydrophobic Fe2O3@C nanoparticles could be reused in water−oil separation for many cycles. Our results suggest a facile and efficient method that might find practical applications in the cleanup of oil spills and the removal of organic pollutants on water surface

Facile Removal and Collection of Oils from Water Surfaces through Superhydrophobic and Superoleophilic Sponges

The development of a convenient method for the removal (or collection) of oils and organic solvents from water surface is of great significance for water environmental protection, especially for the cleanup of oil spillage on seawater. A major challenge is the fabrication of an oil absorber with high absorption capacity, low cost, scalable fabrication, high selectivity, and excellent recyclability. In this paper, we present a simple method for the removal and collection of oils and organic solvents from the surfaces of water based on superhydrophobic and superoleophilic sponges that were fabricated by solution-immersion processes. The as-prepared sponges fast and selectively absorbed various kinds of oils up to above 13 times the sponges’ weight while completely repelling water through a combination of porous, superhydrophobic, and superoleophilic properties. More interesting, the absorbed oils were readily collected by a simple mechanical squeezing process, and the recovered sponges could be reused in oil–water separation for many cycles while still keeping high separation efficiency. The findings presented in this study might provide a fast and simple approach for the cleanup of oils and organic solvents on water surfaces

Intelligent Icephobic Surface toward Self-Deicing Capability

Superhydrophobic surfaces show attractive anti-icing properties. However, it remains a challenge for them to achieve icephobicity and ultralow ice adhesion in a humid environment, which is fundamentally attributed to the icing behavior on their hierarchical textures. Here, we address the issue by integrating a superhydrophobic copper mesh with an intelligent organogel that can secrete antifreezing agent autonomously in response to temperature. The antifreezing agent is composed of ethylene glycol and water. By autonomously secreting the antifreezing agent at subzero temperatures, the hybrid surface effectively inhibits the frosting process on the hierarchical texture of the superhydrophobic mesh. Consequently, the surface not only exhibits excellent antifrosting properties in a humid atmosphere but also repeatedly removes the ice deposited spontaneously due to ultralow ice adhesion (8 Pa). This integration of intelligent organogel paves a new and promising avenue to design superhydrophobic surfaces with excellent icephobic properties