Underwater Superoleophobicity Research Articles

Design of 3D printing superhydrophilic pyramid-shaped porous materials for oil-in-water emulsion separation and visualization of separation mechanism

This study focuses on the design and fabrication of a superhydrophilic pyramid-shaped porous material using high-precision 3D printing technology for effective oil-in-water emulsion separation. The unique pyramid-shaped structure enhances droplet interception, significantly improving separation efficiency. The material’s surface was modified with a self-polymerized dopamine (DA) and polyethyleneimine (PEI) coating, resulting in superhydrophilic and underwater superoleophobicity. This porous material achieved a separation flux of 3098 L/m2h with a separation purity of 99.3 %. Computational Fluid Dynamics (CFD) simulations were employed to visualize the emulsion separation mechanism, providing insights into the dynamic process of droplet behavior within the funnel structure. The material also demonstrated excellent corrosion resistance, maintaining its performance after prolonged exposure to acidic, alkaline, and saline environments. These results suggest that the developed material offers a promising solution for high-efficiency oil–water separation with potential applications in environmental remediation and industrial wastewater treatment.

A Ni-based metal hydroxide-organic framework mesh membrane with ultra-durable underwater superoleophobicity for high-efficient oil/water separation

Recently, MOF-based oil/water separation membranes with superwettability have attracted great attention in the treatment of oily wastewater due to their uniform chemical composition and intrinsic porosity. However, the real separation performance is still limited by broking the metal-ligand bonds of conventional MOF materials in extreme chemical and mechanical environments, such as acidic, alkaline, saline, organic, and abrasion. Herein, we provide a metal hydroxide-organic framework (MHOF) composite mesh membrane for high-efficient oil/water separation by simply growing Ni2(OH)2 clusters onto a polydopamine (PDA)-modified stainless-steel mesh (SSM). Compared with conventional MOF materials, our membrane possesses ultra-durable underwater superoleophobicity by taking advantages of its strong chemical bridging, rich hydrophilic groups, and rough surface morphology, which enables a 1 μL water droplet to spread to 0° contact angle within <100 ms and also obtains an ultra-low underwater oil adhesion force ∼1.9 μN. Separation of both oil/water mixtures and oil-in-water emulsions can be achieved by this Ni-based MHOF mesh membrane with high separation efficiency >99.7 % and large permeate flux >57,000 L m−2 h−1. Furthermore, the Ni2(OH)2@PDA-SSM mesh membrane exhibits excellent anti-oil-fouling, chemical stability and abrasion resistance, which shows a promising candidate for practical applications. This study provides a rational strategy to construct high-performance MHOF membranes for oil/water separation.

Simple and Scalable Approach for Fabrication of a Durable Conjugated Polymer-Decorated Multichannel Tubular Ceramic Membrane with Superoleophobic (Underwater) and Superhydrophilic Surface for Treatment of Oily Wastewater

Simple and Scalable Approach for Fabrication of a Durable Conjugated Polymer-Decorated Multichannel Tubular Ceramic Membrane with Superoleophobic (Underwater) and Superhydrophilic Surface for Treatment of Oily Wastewater

Bifunctional TiO2-Coated SSM for Efficient Emulsion Separation and Photocatalytic Degradation of Soluble Organic Pollutants.

The oily wastewater containing complex organic pollutants poses a great threat to the environment and human beings. At present, the membrane used to treat oily wastewater has some problems, such as complicated preparation and serious membrane pollution. Superhydrophilic/underwater superoleophobic membranes overcome the problems of the surface of the membrane being easily polluted or even blocked by oil, so they have been widely studied by many researchers. In this work, we used an electrochemical deposition method to uniformly load titanium dioxide (TiO2) nanoparticles onto pretreated stainless-steel mesh for efficient oil-in-water (O/W) emulsion separation (TiO2@SSM). The membrane of TiO2@SSM exhibited superior superhydrophilicity and underwater superoleophobicity, ensuring high O/W separation efficiency, reaching 99.8%, and fast water flux of up to 208.0 L·m-2·h-1 for various O/W emulsions. Meanwhile, the membrane possessed a desirable photocatalytic degradation property under visible light irradiation and a degradation efficiency of 98.1% for RhB pollutant. Specially, the as-prepared membrane had long-lasting robustness, sustainability, and recyclability through the cyclic experiments of emulsion separation and photocatalytic degradation. Our results provide a simple and universally applicable route to construct a multifunctional membrane for simultaneously achieving water purification in complex oily wastewater.

Nacre-inspired graphene oxide/polyethyleneimine-based ultra-thin heterogeneous superwetting membrane for highly stable separation of oil-in-water emulsions

Since the massive discharge of oily wastewater seriously affects both humans and natural development, the performance of conventional membrane materials in terms of interfacial stability and antifouling in the treatment of surfactant-containing emulsified oily wastewater is a major challenge. In this work, a novel nacre-inspired graphene oxide/polyethyleneimine-based ultra-thin chemically heterogeneous superwetting membrane was fabricated through vacuum-assisted self-assembly and post-modification methods for oil-in-water emulsion separation. The nacre-inspired heterogeneous membrane exhibited superhydrophilicity, underwater superoleophobicity (underwater oil contact angle was 157.7°), excellent crude oil adhesion resistance, high acid/alkaline stability, outstanding salt resistance, and good mechanical properties (Young’s modulus 1391.7 MPa). The heterogeneous membranes showed separation efficiencies of more than 99.9 % for a range of oil-in-water emulsions. The high-value membranes could achieve the permeances of 917–1256 L m−2h−1 bar−1 for pure water and 339.7–577 L m−2h−1 bar−1 for emulsion through a dead-end filter device, with the optimal long-term stable permeance only decreasing by 30.0 % compared to the initial value. After six test cycles, the membrane’s antifouling and self-cleaning properties were enhanced by constructing heterogeneous superwetting properties, and the flux recovery rate remained at 96.5 %. All of these results indicated that this method provides new ideas for the design and fabrication of highly stable and antifouling membrane materials.

An Anchored Fe-Cu LDH onto a Polyvinylidene Fluoride Membrane with Strong Peroxymonosulfate Activation-Induced Degradation of Methylene Blue and Self-Cleaning Property of Oil/Water Separation.

Developing a strong catalytic antifouling membrane to achieve efficient sewage purification has great potential for alleviating water crisis. In this work, we designed and prepared an Fe/Cu-layered double hydroxide (Fe-Cu LDH)-coated polyvinylidene fluoride (PVDF) composite membrane (PVDF/Fe-Cu LDHs) with strong antifouling and activating peroxymonosulfate (PMS) catalytic degradation performance through polydopamine-coordination anchoring and hydrothermal reaction. The results showed that abundant hydroxyl groups of the LDH surface endowed the superhydrophilicity (water contact angle <10°) and underwater superoleophobicity (underwater-oil contact angle >150°) of the membrane surface, which displayed outstanding resistance to crude oil adhesion. With assistance of the LDH surface-bound sulfate radical of the peroxymonosulfate system, the PVDF/Fe-Cu LDH membrane demonstrated robust catalytic degradation performance for the methylene blue (MB) in the dark; the degradation rate constant (k, min-1) reached 0.96. Meanwhile, facing the oily wastewater, the selective wettability and charge effect of LDH of the surface made the PVDF/Fe-Cu LDH membrane realize the separation for the various surfactant-free and surfactant-stabilized emulsions. Importantly, the PMS-activation catalytic produced the ROS (•SO4-,•OH, •O2-, and 1O2), which enhanced the regeneration of the fouled PVDF/Fe-Cu LDH membrane and obtained a high flux recovery ratio in the dark (94.7%) after 10 cycles of separation experiments. Hence, we believed that the PVDF/Fe-Cu LDH membrane can provide inspiration for the development and further practical application of antifouling membranes.

Enhancing durability and oil-water separation efficiency with plasma-treated graphene oxide coated mesh

In recent years, there has been a surge in interest surrounding the fabrication and utilization of superhydrophobic and superhydrophilic surfaces, driven by their exceptional functionalities and properties. Graphene Oxide (GO) has inherent hydrophilicity and underwater superoleophobicity, which has made this material a particularly capable candidate for oil-water separation. Addressing the persistent challenge of efficient oil-water separation in industrial contexts, this study presents the fabrication of a GO-coated stainless steel mesh via a facile dip coating method augmented by an intermediate two-step O2 plasma treatment. The coated meshes were tested with various oil and water mixtures, including neutral, acidic, saline, and hot water, to find separation efficiency and recyclability. Notably, the meshes can achieve excellent separation efficiency of approximately 98.9 % and a superior flux of 11,464 L m−2 h−1 driven by gravity. This is a significant improvement over GO-coated meshes without O2 plasma treatment. Moreover, the plasma-treated meshes exhibit robust long-term durability and chemical stability, maintaining high underwater oil contact angles ≥119° even after extended immersion in diverse pH mediums and salt solutions for 150 days. This work showcases the practical viability of plasma-treated GO-coated meshes for oil-water separation applications and establishes a framework for systematically evaluating their long-term performance in harsh immersion conditions.

Double bioinspired of robust BaSO4/SnO2 membrane with anti-crude oil adhesion and remarkable emulsion separation

Pollution from oily waste water is a serious environmental problem worldwide, causing serious damage to the environment and human health. At the same time, emulsifiers also cause great difficulties in wastewater treatment. Although efforts have been made to develop many high performance emulsion separation membranes, it is difficult to have the ability to resist crude oil pollution in practical applications. The construction of superoleophobic micro/nano-scale lamellar structured membranes with the potential to efficiently separate oil/water emulsions was inspired by the observation of bi-organisms, specifically the oil-resistant properties of fish scales and the unique adhesion of mussels. Tin dioxide, polydopamine and hydrophilic barium sulphate have been modified on the surface of stainless steel mesh by in-situ hydrothermal and dip coating. The superhydrophilic stainless steel mesh was successfully prepared by using the adhesion of polydopamine. Using the excellent underwater hydration ability of tin dioxide and the hydroxyl group-rich hydrophilic barium sulfate, the modified membrane showed excellent resistance to crude oil pollution. The superhydrophilic membrane can continuously separate different types of oil-in-water emulsions with high separation efficiency (99.9 %) and excellent separation flux (900 L m−2 h−1), with no decrease in efficiency and flux after 10 emulsion separation cycles. In addition, the superhydrophilic membrane has excellent durability and stability, remaining super-oleophobic underwater to sand shock, sandpaper abrasion, high saline corrosion and UV ageing. The prepared stainless steel membrane not only provides a novel anti-fouling strategy, but its excellent stability also provides some new inspiration for the treatment of oil and water pollution in the future.

Robust antifouling Poly(ionic liquid)s membrane with cyclodextrin skeleton for separation of oil/water emulsions

Membrane fouling remains a persistent and arduous challenge in the industrial treatment of different surfactants-stabilized oily wastewater. Constructing a robust antifouling and sustainable hydration coating on the membrane surface to efficiently repel oils or surfactants is a critical requirement. Herein, cyclodextrin-based poly(ionic liquid)s (PILs) coatings are cross-linked via the co-deposition on poly(vinylidene fluoride) (PVDF) of quaternized heptkis(6-deoxy-6-vinylimidazolium)-β-cyclodextrin (CD-Vi) derivatives as skeleton and acrylic acid (AA) monomers, and following one-step free radical photopolymerization. Combining with the strong hydration of the CD-based PILs coating, the resultant membrane exhibits fabulous superhydrophilicity and underwater superoleophobicity, oil repulsion, and self-cleaning capability. It demonstrates robust mechanical durability and chemical stability in harsh environments without losing its superhydrophilicity. Besides, the PIL-CD/AA coating can separate various surfactant-free and different surfactants (cationic CTAB, anionic SDS, and nonionic TWEEN 80) stabilized oil / water emulsions. During the long-term cycle operations, it also realizes stable recyclability with a series of permeation fluxes as high as removal efficiencies (>99.6 %) after 20 cycles for surfactant-free cyclohexane-in-water emulsion and 10 cycles for CTAB-stabilized isooctane-in-water emulsion.

High-permeance nanocellulose/ZnO hybrid membranes with photo-induced anti-fouling performance for wastewater purification

A hybrid ultrafiltration membrane based on nanocellulose and zinc oxide nanoparticles (ZnO NPs) was prepared by simple layered filtration without any chemical modification. Microscopic morphology analysis showed that the loading ZnO NPs significantly increased the membrane roughness, and wettability test demonstrated that the membrane surface possessed underwater superoleophobicity. Due to the “puncture effect” of the embedded ZnO NPs, abundant nanochannels were formed in the nanocellulose membrane and the highest water permeance of 5439.7 L·m−2·h−1·bar−1 was achieved. The hybrid membranes exhibited high rejection of nanoparticles larger than 20 nm and macromolecules with molecular weights higher than 100 kDa. Furthermore, ZnO NPs significantly improved the wet tensile strength of membrane. The hybrid membranes achieved high separation efficiency of nano-sized emulsions via size exclusion and demulsification effect, as well as the efficient removal of organic dyes and antibiotics via filtration-adsorption. The combination of underwater superoleophobicity and photocatalytic self-cleaning performance effectively solved the problem of a sharp decrease in permeance caused by oil contamination. This type of nanocellulose/ZnO hybrid membrane, which integrates high permeance, high filtration accuracy, and photocatalytic anti-fouling performance in one design, offers an innovative approach to the preparation of nanocellulose membranes for the treatment of organic wastewater.

Fabrication of a ZIF-8/PVA Membrane on PVDF Fiber by Spray for the Highly Efficient Separation of Oil-in-Water Emulsions.

In human life and production, excessive oily wastewaters containing detergents are produced and discharged, causing severe environmental pollution and water resource problems. A metal-organic framework (MOF)-based membrane is an economical and environmentally friendly tool for emulsion separation but is limited by a complex preparation process and poor flexibility. Herein, we developed a simple method to synthesize a MOF-based mixed-matrix membrane (MMM) by spray and fabricated the membrane on poly(vinylidene fluoride) (PVDF) fibers via postdeposition and in situ growth manners. The prepared ZIF-8/PVA MMMs have uniform distribution of ZIF-8 particles and poly(vinyl alcohol) (PVA) on the PVDF fibers. PVA improved the adhesion between the ZIF-8 particles and between the MOF layer and PVDF fiber, endowing the separation membrane with high flexibility and bendability. The prepared ZIF-8/PVA membrane exhibited hydrophilicity and underwater superoleophobicity, which showed high separation efficiency and considerable water flux for emulsions, emulsion containing dye, and surfactant-stabilized emulsion. In addition, the fabricated ZIF-8/PVA/PVDF fibers exhibited good antifouling property and flexibility and can maintain stable separation efficiency after working several times and even under bending, demonstrating the stability and potentiality of the ZIF-8/PVA/PVDF fibers in practical applications. This work paves a new avenue for the synthesis and application of MOF-based MMMs.

BiOCl-PVDF nanofibrous membrane for synergic oil-water separation and degradation of dye

Polymeric membranes have garnered remarkable attention, attributed to the significant breakthrough in the filtration of oily wastewater. However, the major setbacks of pristine polymeric membranes include susceptibility to fouling and chemical instability. Addressing such issues, this work focusses in the modification of polymer membranes using a metal oxyhalide, such as Bismuth oxychloride (BiOCl). This modification not only enhances water purification capabilities but also strengthens the membrane, protecting it from environmental deterioration and extending its lifespan. BiOCl was integrated into an electrospun pristine nanofibrous polymeric membrane using hydrothermal technique. The synthesized membrane matrix displayed superhydrophilicity and underwater superoleophobicity, effectively separating oil-in-water mixtures and emulsions. Moreover, BiOCl was effectively utilized to assess organic pollutant adsorption and degradation through photocatalysis. In addition, the membrane exhibited exceptional recyclability and withstood harsh conditions, contributing to its mechanical stability. The numerous advantages, enhance the effectiveness of BiOCl modified membrane in water pollution remediation.

A novel asymmetric superwetting filter prepared by easily mass-produced strategy for high-efficient and switchable water/oil filtration

All-purpose materials with on-demand oil/water separation property have received broad attention recently. Herein, a filter paper (FP)-based filter with asymmetric wettability was designed and fabricated via simple combination of liquid phase reduction route with symmetry adhesion method. The fabricated filter exhibits underoil superhydrophobic (UOSHP) and underwater superoleophobic (UWSOP) property. Especially, the good underliquids lyophobicity is still maintained after tape peeling and corrosive, organic solvents treatments. By fixing the hydrophobic (HO) side of filter facing up, the water/light oil mixtures and oil-in-water (O-in-W) emulsions can be highly efficient separated, and the water/heavy oil mixtures and water-in-oil (W-in-O) emulsions are able to be separated with the HI side facing up. The separation efficiencies for water/oil mixtures and oil/water emulsions are higher than 98% and 99.1%, respectively. The study offers a new idea for the preparation of asymmetric superwetting materials with good stability and on-demand water/oil separation capability.

Mesh coated with microbially induced nanoscale vaterite for oil-in-water emulsion separation

Microbial-induced calcium carbonate precipitation (MICP), with its hydrophilic rough microstructures and as an environmentally friendly material modification method, has shown great potential for oil-water separation. However, its efficiency in separating oil-in-water emulsions remains challenging. This study advances the MICP method by producing microbially induced nanoscale calcium carbonate on a mesh using calcium acetate instead of traditional calcium chloride, successfully achieving efficient separation of oil-in-water emulsions. The stainless-steel mesh (SSM) after calcium acetate-MICP treatment obtained nano-elliptical flake-like vaterite (vaterite-SSM) and demonstrated superior superhydrophilicity and underwater superoleophobicity compared to the mesh coated with micro-cubic structured calcite (calcite-SSM) treated by calcium chloride-MICP. Notably, vaterite-SSM achieved a flux of up to 309 L·m−2·h−1 and an oil rejection rate of over 98.7 % in gravity-driven separation of oil-in-water emulsions, demonstrating significant reusability after 6 cycles. Conversely, calcite-SSM was ineffective in emulsion separation due to coating instability and large particle spacing. Additionally, vaterite-SSM effectively separated various oil-water mixtures, maintaining high performance across 30 separation cycles. This study underscores the important use of calcium acetate in MICP to obtain nano-elliptical flake-like vaterite for efficient oil-water emulsion separation, advancing the promise of MICP as an effective and sustainable method for environmental applications.

Exploring the potential of perovskite structured SrTiO3 ceramics nanoparticles for developing SrTiO3 ceramics-decorated advanced Super-Wettable and photocatalytic self-cleaning membrane and its applications

There is a huge potential in developing robust, highly stable, and covalently crosslinked ceramics-decorated membranes that can be efficiently used for the treatment of oil-contaminated water. Hence, the current work was focused on developing a photo-active strontium titanate (SrTiO3) perovskite ceramics decorated highly stable membrane with photocatalytic self-cleaning, superoleophobic underwater and superhydrophilic in air features. The SrTiO3 perovskite structured ceramics were decorated in the active layer of the membranes through interfacial polymerization on a polyvinylidene difluoride (PVDF) ultrafiltrationsupport. For the sake of photoactive SrTiO3 ceramics nanoparticles to take part in the interfacial polymerization, the SrTiO3 ceramics nanoparticles were functionalized with amino silane using 3-aminopropyltriethoxysilane yielding amino-functionalize-SrTiO3 (F-SrTiO3). Ethylenediamine (EDA) was used as an additional amine for ensuring the suitable cross-linking of the polyamide (PA) network where isophthaloyl chloride (IPC) was used as a crosslinker. The resultant F-SrTiO3/PA@PVDF membrane was thoroughly investigated through several membrane characterization techniques confirming the existence of all the components in the membrane structure. When applied for separating the emulsified and surfactant stabilized oil from water, the F-SrTiO3/PA@PVDF membrane showed excellent separation efficiency reaching >99 % for an emulsion of 200 ppm with a permeance of 56 L m−2 h−1 bar−1. Moreover, the membrane showed an underwater superoleophobic (θO, W = 159.9°) nature owing to the presence of amide linkages and superhydrophilic F-SrTiO3 nanoparticles. These features lowered the evidence of membrane fouling and the photocatalytic self-cleaning potential of F-SrTiO3 resulted in removing the foulants from the membrane surface with a flux recovery of 95 % while keeping the separation efficiency intact. Hence, the current approach of covalently incorporating the photocatalytic, superhydrophilic F-SrTiO3 in the membrane active layer proved to be robust and can be readily scaled up and applied in real-life filtration conditions.

MOF-Decorated Poly(tetrafluoroethylene) Membranes with Underwater Superoleophobicity for Extracting Osmotic Energy from Oily Wastewater Effluents.

Industrial processes generate huge volumes of oily saline wastewater. Instead of being sent to the drainage system immediately, extracting osmotic energy from these effluents represents a promising means to reuse these wastes and contributes to mitigate the ever-growing energy crisis. Herein, an MOF-decorated PTFE membrane is engineered to extract osmotic energy from oily wastewaters. Copper hydroxide nanowires (CHNs) are intertwined with polystyrenesulfonate sodium (PSS), deposited onto a poly(tetrafluoroethylene) (PTFE) membrane, and thereafter used as metal precursors to in situ generate HKUST-1 doped with negative charges. The resulting HKUST-1PSS@PTFE hybrid membrane possesses abundant angstrom-scale channels capable of transporting cations efficiently and features a hierarchically structured surface with underwater superoleophobicity. The energy conversion performance of the HKUST-1PSS3.5@PTFE membrane can reach an output power density of 6.21 W m-2 at a 50-fold NaCl gradient, which is superior to those of pristine PTFE membranes. Once exposed to oily saline wastewater, the HKUST-1PSS@PTFE membrane can exhibit an excellent oil-repellent ability, thus contributing to sustain its osmotic energy harvesting. This work may promote the development of antifouling osmotic energy harvesters with a long working life and pave the way to fully exploit oily wastewater effluents as valuable energy sources.

Bioinspired surface silicification of cellulose-mediated PVDF membranes for significantly enhancing superhydrophilicity and anti-oil adhesion toward ultrafast oil/water emulsion separation

Cellulose is a widely used hydrophilic material due to its rich hydrophilic hydroxyl groups. However, the presence of its lipophilic segment will affect the antifouling performance. Finding strategies to improve this problem has attracted considerable attention. In this work, a layer of silica was applied to a cellulose-deposited polyvinylidene fluoride membrane through a straightforward in-situ bionic silicification process of tetraethyl orthosilicate. The contact angle and oil droplet contact test proved that the high-hydrophilicity and underwater superoleophobicity of the silicified membranes were significantly enhanced. The surface structure and composition were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results of show that this improvement was mainly attributed to the presence of silicon hydroxyl groups, buried cellulose chains, and micro-nanostructures composed of cellulose and silica. The stable silica coating also provided protection for the polymeric membrane against degradation after water washing for 24 h, ultrasonic treatment (40 KHZ) for 10 min or exposure to different pH levels (pH=1, 4, 9 and 12) and saturated sodium chloride solution for 24 h. Furthermore, the silicified membrane showed outstanding oil adhesion resistance and permeation flux, enabling effective purification of different oil-in-water emulsions that were stabilized by emulsifiers. Notably, the membrane achieved a high oil removal rate (> 99.4 %) of various emulsions (toluene-in-water, cyclohexane-in-water, tetrachloroethane-in-water, soybean oil-in-water, toluene-in-salt solution, toluene-in-acid solution and toluene-in-alkaline solution emulsions). In particular, for toluene-in-water emulsions (oil droplets in the emulsion ranged from 58.77 nm to 615.1 nm), a significantly enhanced permeation flux (4777 L·m−2·h−1·bar−1) was obtained at 0.8 bar pressure. Even after multiple cycles of separation, the flux was higher than that of the unsilicified membrane. Overall, this approach is mild, simple, efficient, and easily scalable, making it an ideal method for producing superhydrophilic coatings with substantial application potential.

A universal strategy for efficient separation from single emulsion separation to oil-in-water and water-in-oil mixed emulsions

To realize efficient treatment of oily wastewater, various super-wetting materials have been developed. Oily wastewater is often complex and may contain both oil-in-water and water-in-oil emulsions. However, most of the current studies focus on the treatment of single emulsions, and there are fewer studies on the simultaneous separation of oil-in-water and water-in-oil emulsions. In this paper, by removing hemicellulose and lignin from bamboo processing waste powder (BPWP), the treated bamboo powder (TBP) containing mainly cellulose was obtained. TBP has superoleophobicity underwater and superhydrophilicity underoil, which can separate not only various oil-in-water emulsions stabilized by surfactants, but also water-in-oil emulsions stabilized by different surfactants, and the separation efficiency is higher than 99 %. The separation efficiencies of TBP for different water-in-oil emulsions were all higher than 99 %. On this basis, we have established an intelligent device that makes full use of underwater super-hydrophobic and under-oil super-hydrophilic properties to realize the purification of water and de-watering and recycling of floating oil in complex oil-water systems. This work provides a very promising direction for industrial application in practical oily wastewater treatment and fuel recovery.

A “like-zwitterionic” forward osmosis membranes with electrostatic deposition of aluminosilicate nanotubes for resisting positively and negatively charged protein and oil contaminant

Membrane fouling has always been a huge obstacle to the development of membrane separation technology, including forward osmosis (FO) technology. In this work, polyamide (PA) thin-film composite (TFC) membranes were simply immersed in aluminosilicate nanotubes (ANTs) dispersions to obtain thin-film nanocomposite (TFN) FO membranes. With the help of the opposite surface charge of ANTs and PA layer, and the representative “peak-valley” structure of PA TFC membrane, ANTs are stably bound to the surface of TFC membrane by electrostatic adsorption and physical confinement. The TFN membrane has greatly enhanced hydration ability due to the rich hydrophilic hydroxyl groups of ANTs, “like-zwitterionic” surface composition and rough nanostructure morphology, resulting in good underwater superoleophobicity. Combined with the water transport channel formed by its nanoporous structure, the surface anti-protein adhesion and anti-oil–water emulsion adhesion can be achieved without affecting the water flux. It is worth noting that the surface potential of TFN membrane is close to neutral due to charge neutralization. This avoids the electrostatic interaction between the membrane surface and the contaminant, and further achieves a universal anti-fouling ability that is not affected by protein or emulsion charge, and the irreversible adsorption is close to zero. In addition, the rigid ANTs coating exhibits excellent stability and reusability under long-term use, and the water flux after cleaning can be restored to nearly 99.9%. In general, this method of using ANTs deposition to improve the antifouling performance of PA based TFC membrane is simple, efficient, stable, and easy scalable. This method is not only limited to FO membrane, but also can be extended to PA based reverse osmosis and nanofiltration membranes, which has great practical application potential.

All cellulose-based superwetting aerogel/wood composite with disordered/ordered pores structure for rapid emulsion separation

Rapid and efficient separation of oil from emulsions is critically required prior to addressing the global challenge of oily sewage, but most separation membranes encounter intractable challenges in terms of the trade-off effect between separation efficiency and flux, as well as the use of petrochemical feedstocks. Herein, an all-biomass wood/aerogel composite with a disordered/ordered structure was constructed by filling cellulose nanofibers aerogel into the intertubular cavities of delignified wood using cotton and wood as building blocks through a series of processes, including casting, regeneration, and freeze-drying. The parallel channels of wood and the porous structure of aerogel constitute the special disordered/ordered pores structure, which accelerates vertically oriented permeation and enhances emulsified droplets coalescence for demulsification. In addition, the aerogel/wood composite retains the inherent hydrophilicity of cellulose and exhibites excellent underwater superoleophobicity with an underwater oil contact angle of 159.6°, which is chemically stable and salt resistant. The unique disordered/ordered structure and superwettability of the aerogel/wood composite contribute to its exceptional separation efficiency (99.25 %) and high flux (2580 L·m−2·h−1) for the separation of oil-in-water emulsions when driven only by gravity. Additionally, the composite shows good utility and ease of cycling. These outstanding properties highlight its promising practical application in the oil-related industry.