Bioinspired, Mechano-Regulated Interfaces for Rationally Designed, Dynamically Controlled Collection of Oil Spills from Water

Selective Wettability Membrane for Continuous Oil-Water Separation and In Situ Visible Light-Driven Photocatalytic Purification of Water

Membrane-based technologies are attractive for remediating oily wastewater because they are relatively energy-efficient and are applicable to a wide range of industrial effluents. For complete treatment of oily wastewater, removing dissolved contaminants from the water phase is typically followed by adsorption onto an adsorbent, which complicates the process. Here, an in-air superhydrophilic and underwater superoleophobic membrane-based continuous separation of surfactant-stabilized oil-in-water emulsions and in situ decontamination of water by visible-light-driven photocatalytic degradation of dissolved organic contaminants is reported. The membrane is fabricated by utilizing a thermally sensitized stainless steel mesh coated with visible light absorbing iron-doped titania nanoparticles. Post annealing of the membrane can enhance the adhesion of nanoparticles to the membrane surface by formation of a bridge between them. An apparatus that enables continuous separation of surfactant-stabilized oil-in-water emulsion and in situ photocatalytic degradation of dissolved organic matter in the water-rich permeate upon irradiation of visible light on the membrane surface with greater than 99% photocatalytic degradation is developed. The membrane demonstrates the recovery of its intrinsic water-rich permeate flux upon continuous irradiation of light after being contaminated with oil. Finally, continuous oil-water separation and in situ water decontamination is demonstrated by photocatalytically degrading model toxins in water-rich permeate.

EcoFlex Sponge with Ultrahigh Oil Absorption Capacity

A paraffin microsphere-templated 3D porous EcoFlex sponge was prepared to selectively absorb oil or chemicals from water. The technology for producing this EcoFlex sponge does not need complicated synthesis processes or instruments, and the materials applied in this work are ecofriendly. Therefore, this sponge can be employed in the environmental field. EcoFlex sponges showed high hydrophobicity (contact angle = 140-143°) and oleophilicity. The developed sponge exhibits a porous three-dimensional framework inside with excellent internal connectivity, which contributes both better absorption capacity and faster absorption rate. For instance, the absorption capacity for chloroform can reach 3400 wt %. The absorption capacity of the sponge was optimized using different size of paraffin microspheres and these sponges exhibit relatively high absorption capacity in a short time (2 min). The volume of sponge expands in some oils and organic solvents: the increased volume capacity for hexane can reach 2200%. This sponge also has great recovery capability and durability; it keeps its original shape and absorption capacity after 15 cycles of oil absorption and compression.

Polydimethylsiloxane/Nanodiamond Composite Sponge for Enhanced Mechanical or Wettability Performance

Polydimethylsiloxane (PDMS) is widely utilized in material science, chemical engineering, and environmental science due to its excellent properties. By utilizing fillers, so-called composite materials can be obtained with enhanced mechanical, wettability, or thermal conductivity performance. Here, we present a simple, cost-effective approach to vary either the mechanical properties (Young's modulus) or surface wettability of bulk PDMS and PDMS sponges simply by adding nanodiamond filler with different surface terminations, either oxidized (oND) or hydrogenated (reduced, rND) nanodiamond. Minuscule amounts of oxidized nanodiamond particles as filler showed to benefit the compressive Young's modulus of composite sponges with up to a 52% increase in its value, while the wettability of composite sponges was unaffected. In contrast, adding reduced nanodiamond particles to PDMS yielded inclined water contact angles on the PDMS/nanodiamond composite sponges. Finally, we show that the PDMS/rND composites are readily utilized as an absorbent for oil/water separation problems. This signifies that the surface termination of the ND particle has a crucial effect on the performance of the composite.

Natural-Light-Initiated 3D Macro Zigzag Architecture of Graphene-Reinforced Polystyrene for Gravity-Driven Oil and Water Separation

Superhydrophobic 3D robust materials are introduced for the separation of hexane and water. For the first time, novel 3D zigzag polystyrene on graphene-incorporated polyurethane (3D zz-PS/GR/PU) is prepared using exclusively natural sunlight without any chemical initiator. The zigzag polystyrene growth is accomplished by polymerizing the styrene vapors. The natural sunlight provides a compact 3D zz-PS/GR/PU material with superoleophilic and hydrophobic channels that allow for the rapid passage of oil, whereas water is entirely prevented from passing. The 3D zz-PS/GR/PU compact channels are transformed into the compressible material by treating them with toluene without affecting the hydrophobicity of the material. The 3D zz-PS/GR/PU displays a high-water contact angle of approximately 150°. The developed materials are characterized by FTIR, SEM, and BET. The graphene incorporation makes surface area of the 3D zz-PS/GR/PU substantially large compared with PU. It is improved from 15 to 67 m2 g-1. The pore size of the adsorption and desorption in the 3D zz-PS/GR/PU is also reduced from 354 and 352 Å to 34 and 33 Å. The 3D zz-PS/GR/PU satisfies the requirement of high-demanding superhydrophobic materials, like a low-cost fabrication process, reusability, and tunability. This strategy can trigger large-scale production with a controlled morphology.

Hydrophilic Sponges for Leaf-Inspired Continuous Pumping of Liquids

A bio-inspired, leaf-like pumping strategy by mimicking the transpiration process through leaves is developed for autonomous and continuous liquid transport enabled by durable hydrophilic sponges. Without any external power sources, flows are continuously generated ascribed to the combination of capillary wicking and evaporation of water. To validate this method, durable hydrophilic polydimethylsiloxane sponges modified with polyvinyl alcohol via a "dip-coat-dry" method have been fabricated, which maintains hydrophilicity more than 2 months. The as-made sponges are further applied to achieve stable laminar flow patterns, chemical gradients, and "stop-flow" manipulation of the flow in microfluidic devices. More importantly, the ease-of-operation and excellent pumping capacity have also been verified with over 24 h's pumping and quasi-stable high flow rates up to 15 µL min-1. The present strategy can be easily integrated to other miniaturized systems requiring pressure-driven flow and should have potential applications, such as cell culture, micromixing, and continuous flow reaction.