Facile preparation of a superamphiphilic nitrocellulose membrane enabling on-demand and energy-efficient separation of oil/water mixtures and emulsions by prewetting

A Self-Cleaning TiO2 Bacterial Cellulose Super-Hydrophilic Underwater Super-Oleophobic Composite Membrane for Efficient Oil-Water Separation

Due to the increasingly serious problem of offshore oil spills, research related to oil-water separation has attracted more and more attention. Here, we prepared a super-hydrophilic/underwater super-oleophobic membrane (hereinafter referred to as BTA) using poly-dopamine (PDA) to adhesive TiO₂ nanoparticles on the surface of bacterial cellulose, coated with sodium alienate by vacuum-assisted filtration technique. This demonstrates its excellent underwater super-oleophobic property. Its contact angle is about 153°. Remarkably, BTA has 99% separation efficiency. More importantly, BTA still showed excellent anti-pollution property under ultraviolet light after 20 cycles. BTA has the advantages of low cost, environmentally friendliness and good anti-fouling performance. We believe it can play an important role in dealing with problems related to oily wastewater.

Cellulose/Poly(vinyl alcohol)/Tannic Acid Porous Cross-Linked Composite Frame Materials with Excellent Oil/Water Separation Performance

Problems such as increasingly serious water pollution attracted widespread concern. The underwater OCAs of the samples became larger with increasing pH and the under-oil WCAs of the samples did not vary regularly with increasing pH. Nanoneedle structures were grown on metal foam by anodization. Cellulose is fixed to the frame by cross-linking with supramolecular binder poly(vinyl alcohol)/tannin. A cellulose/poly(vinyl alcohol)/tannin porous composite framework with special wettability is prepared. This porous composite framework can be used for the continuous separation of oil/water mixtures with high separation efficiency, high throughput, excellent reusability, and mechanical durability. In addition, due to the coating of cellulose and the supramolecular binder, the pore size of the frame is reduced, and the cagelike structure of the porous framework can promote its demulsification effect. Therefore, the cellulose/poly(vinyl alcohol)/tannic acid porous composite frame can also be used for the separation of oil/water emulsions. This porous frame material has broad application prospects in oil spill treatment and sewage purification.

Durable 3D Porous Superhydrophobic Composites for Versatile Emulsion Separation in Multiple Environments

Polydopamine as a multifunctional biomimetic polymer with nonselective strong adhesion properties has become a hot research topic in recent years. However, there are a few reports on the durable and effective emulsion separation of polydopamine composites from other materials. Therefore, it is necessary to construct durable polydopamine composites to achieve selective adsorption of materials. In this work, polypyrrole (PPy)-PDA was obtained on sponges by an in situ polymerization reaction, followed by the attachment of SiO₂ nanoparticles to the surface by polydimethylsiloxane to achieve superhydrophobicity. As a result, previously unreported selective superhydrophobic adsorbents for PPy-PDA coatings were obtained. The prepared sponges have an excellent adsorption capacity for oils and organic solvents. Not only can the sponges absorb 19-39 g of organic solvents per gram but they can also absorb oil from oil-in-water emulsions. The chemical oxygen demand value of the emulsion can be reduced to 219 mg/L after separation. More importantly, the performance remains good in the cycle test, and due to the construction of a durable superhydrophobic sponge, it can still maintain its relatively good performance in artificial seawater, acid-base environments, and can achieve relatively stable emulsion separation. At the same time, the potential of the polymer material composited with PDA in lasting and stable emulsion separation was also verified.

Two-step facile fabrication of superamphiphilic biomimic membrane with micro-nano structure for oil-water emulsion separation on-demand

Superamphiphilic materials have attracted much attention due to their different wettability in different media. Through a simple two-step method, we fabricated a smart separation membrane with super-amphiphilic wettability. Under the...

One-Step Fabrication of a Functionally Integrated Device Based on Polydimethylsiloxane-Coated SiO2 NPs for Efficient and Continuous Oil Absorption

The construction of superhydrophobic surfaces necessitates the rational design of topographic surface structure and the reduction of surface energy. To date, the reported strategies are usually complex with multi-steps and costly. Thus, the simultaneous achievement of the two indispensable factors is highly desired, yet rather challenging. Herein, we develop a novel structure engineering strategy of realizing the fabrication of a functionally integrated device (FID) with a superhydrophobic surface via a one-step spraying method. Specifically, silica nanoparticles are used to control the surface roughness of the device, while polydimethylsiloxane is employed as the hydrophobic coating. Benefitting from the adopted superhydrophobicity, the as-fabricated FID exhibits a continuous, excellent oil-water separating performance (e.g., 92.5% separating efficiency) when coupled with a peristaltic pump. Notably, a smart design of incorporating a gas switch is adopted in this device, thereby effectively preventing water from entering the FID, realizing thorough oil collection, and avoiding secondary pollution. This work opens up an avenue for the design and development of the FID, accessible for rapid preparation and large-scale practical application.

A robust surface with superhydrophobicity and underwater superoleophobicity for on-demand oil/water separation

Superhydrophobic and underwater superoleophobic surface combine the superiorities of the two opposite wettabilities. Generally, such a surface is constructed by hydrophilic areas and hydrophobic areas treated with fluorine-containing modifiers. However, the surface energy in a narrow range and poor bonding force between water-loving and water-repelling components make the surface fragile and its wettability unstable. Herein, we present a strategy to fabricate a robust surface with superhydrophobicity and underwater superoleophobicity. Hydrophilic aluminum phosphate as a binder can strongly interact with superhydrophobic titanium dioxide nanoparticles. Mixing the two ingredients to accurately control the surface energy in a narrow range and then spray coating, the superhydrophobic and underwater superoleophobic surfaces are conveniently prepared on diverse substrates. Under acid/base aqueous solution conditions, O₂-plasma etching, and sand impingement, the coatings remain superhydrophobic and underwater superoleophobic. Taking advantage of the wettability and robustness of coatings, the as-prepared membranes realize on-demand and multicycle separation under gravity without continuous external stimulus. Importantly, even after 100 sand impingement cycles, the treated membranes still maintain prominent separation performance.

Simple preparation of a durable and low-cost load-bearing three-dimensional porous material for emulsion separation

Superhydrophobic MR–C composites were used for the separation of water-in-oil emulsions. Under a load of 500 N with a reciprocating wear, the contact angle was kept at 146 ± 2°. The oil-in-water emulsion can still be separated efficiently.