Superoleophilic Properties Research Articles

Buoyancy-Assisted Fabrication of Liquid Diode: Janus Nanofibrous Membrane for Efficient Wastewater Treatment.

The pressing need for effective methods to separate oil and water in oily wastewater has spurred the development of innovative solutions. This work presents the creation and evaluation of a Janus nanofibrous membrane, also known as the Liquid Diode, developed using electrospinning (e-spinning) and buoyancy-assisted hydrothermal techniques. The membrane features a unique structure: one side is composed of PVDF nanofibers embedded with a GO/TiO2 composite, exhibiting in-air superhydrophobic and superoleophilic properties, while the reverse side consists of PVDF nanofibers with a ZnO nanorod array, demonstrating in-air superhydrophilic and underwater (UW) superoleophobic properties. This distinct asymmetric wettability enables the membrane to effectively separate both water-in-oil (w-in-o) and oil-in-water (o-in-w) emulsions, achieving an impressive liquid flux and separation efficiency (SEff). The in-air superhydrophobic side of the Janus nanofibrous membrane achieves a maximum oil flux (Fo) of 3506 ± 250 L m-2 h-1, while the in-air superhydrophilic side achieves a maximum water flux (Fw) of 1837 ± 150 L m-2 h-1, with SEff exceeding 98% for both sides. Furthermore, the Janus nanofibrous membrane maintained reliable mechanical stability after 10 cycles of sandpaper abrasion test and demonstrated excellent chemical stability when subjected to acidic, alkaline, cold water and hot water conditions for 24 h. These properties, combined with its ability in breaking down of organic contaminants (98% ± 2% in 210 min) and pharmaceutical contaminants (97% ± 2% in 210 min) under visible light, highlight its photocatalytic potential. Additionally, the membrane's antifouling and antibacterial properties suggest long-term and sustainable use in wastewater treatment applications. The synergistic combination of these superior properties positions the Janus nanofibrous membrane as a promising solution for addressing complex challenges in wastewater treatment and environmental remediation.

Nanosheet BiOBr Modified Rock Wool Composites for High Efficient Oil/Water Separation and Simultaneous Dye Degradation by Activating Peroxymonosulfate.

The development of superlyophobic materials in liquid systems, enabling synchronous oil/water separation and dye removal from water, is highly desirable. In this study, we employed a novel superwetting array-like BiOBr nanosheets anchored on waste rock wool (RW) fibers through a simple neutralization alcoholysis method. The resulting BiOBr/RW fibers exhibited superoleophilic and superhydrophilic properties in air but demonstrated underwater superoleophobic and underoil superhydrophobic characteristics. Utilizing its dual superlyophobicity, the fiber layer demonstrated high separation efficiencies and flux velocity for oil/water mixtures by prewetting under a gravity-driven mechanism. Additionally, the novel BiOBr/RW fibers also exhibited excellent dual superlyophobicity and effective separation for immiscible oil/oil systems. Furthermore, the BiOBr/RW fibers could serve as a filter to continuously separate oil/water mixtures with high flux velocity and removal rates (>93.9%) for water-soluble dye rhodamine B (RhB) simultaneously by directly activating peroxymonosulfate (PMS) in cyclic experiments. More importantly, the mechanism of simultaneous oil/water separation and RhB degradation was proposed based on the reactive oxygen species (ROS) quenching experiments and electron paramagnetic resonance (EPR) analysis. Considering the simple modified process and the waste RW as raw material, this work may open up innovative, economical, and environmentally friendly avenues for the effective treatment of wastewater contaminated with oil and water-soluble pollutants.

Whole-Waste synthesis of Kilogram-Scale Macropores adsorbent materials for Wide-Range oil and heavy metal removal

The rapid pace of social development leads to the generation of significant quantities of oily wastewater and heavy metal ions, posing severe threats to the environment and human health. Therefore, finding cost-effective and efficient adsorbent materials is crucial. In the present study, a porous organic polymer based on waste cooking oil was synthesized as a macropores material called POP-WCO, allowing for preparation in kilogram quantities (more than one kilogram in a single batch). This material effectively removes oil and heavy metals, exhibiting excellent hydrophobic and superoleophilic properties, enabling the adsorption of various common oils within 22 s. POP-WCO is designed to swiftly remove and recover eight common oils through simple mechanical extrusion, maintaining a consistent oil recovery efficiency of 94% after 10 cycles. It can effectively treat and recover oil spills at sea through static and continuous adsorption. In addition, the POP-WCO material removes over 99% of the heavy metal mercury, showing exceptional resistance to acid, alkali, and salt, as well as economic value. The mechanism of Hg(II) adsorption by POP-WCO has been confirmed through density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analysis, elucidating the microdynamics process of the adsorption mechanism. This research presents an important strategy for achieving resource sustainability by transforming waste into valuable materials.

Development of superhydrophobic and superoleophilic CNT and BNNT coated copper meshes for oil/water separation

In this research, chemical vapor deposition (CVD) method was used to synthesize boron nitride nanotube (BNNT) powder. This method involves heating multi-walled carbon nanotube (MWCNT) and boric acid in the presence of ammonia gas up to 1000 °C. Then MWCNT and synthetic BNNT were coated on the copper mesh via dip-coating method separately to prepare nano-structured membranes for efficient oil/water separation. Various analyzes were performed to identify the synthetic BNNT properties (X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and prepared coated membranes (FESEM, atomic force microscopy (AFM), water contact angle (WCA), oil contact angle (OCA) and oil/water separation process). Water and oil contact angle analyzes showed the super-oleophilic properties of both membranes with the underwater OCA of about 128°. For the separation process, a dead-end filtration setup was used, and free oil water mixture and o/w emulsion were prepared. So, in the separation process water was retained and decalin passed through both prepared membranes. The flux of CNT coated membrane was about 458 L m2 h−1, while this amount was 1834 L m2 h−1 for BNNT coated membrane and 99% separation efficiency was achieved by both of them. This four-fold increase in flux is due to the fact that the inner diameter of boron nitride nanotubes synthesized is four times larger than the inner diameter of MWCNT.

Enhanced superhydrophobic melamine sponge with bimetal organic framework for simultaneous oil-water separation and microplastic removal

The escalating problem of oily wastewater and microplastic pollution poses a significant threat to our environment. Addressing this challenge has been hampered by the lack of sustainable materials capable of handling multiple pollutants effectively. However, this research introduces a groundbreaking approach for designing a superhydrophobic composite sponge, MS@ZnCo-ZIF@HDTMS. Utilizing a straightforward layer-by-layer self-assembly strategy, this work achieved the robust integration of bimetallic organic framework (ZnCo-ZIF) onto the sponge surface. This integration was facilitated by the adhesive and ion exchange properties of polydopamine (PDA), thereby constructing intricate micro- and nanocomposite structures. The immense specific surface area of ZnCo-ZIF offered numerous absorption sites for the assembly of PDA and hexadecyltrimethoxysilane (HDTMS). Remarkably, the composite sponge exhibits superhydrophobic and superoleophilic properties, demonstrating exceptional oil absorption capacities ranging from 55 g/g to 96 g/g, even after enduring 50 cycles. Moreover, MS@ZnCo-ZIF@HDTMS possesses remarkable mechanical and chemical stability. Its gravity-driven oil-water separation capabilities are noteworthy, achieving a permeate flux of 10,000 L m-2 h-1 and a removal rate of up to 99.2 %. Crucially, the superhydrophobic nature of the composite sponge, coupled with capillary effect, Van der Waals forces, hydrogen bonding, and other interactions, enables MS@ZnCo-ZIF@HDTMS to capture a diverse range of microplastics from water relatively swiftly. Therefore, this work not only provides effective candidates for the sustainable treatment of oil and microplastics in water but also opens new avenues for the restoration of aquatic environments.

Ultrasonic Plasticizing and Pressing of High-Aspect Ratio Micropillar Arrays with Superhydrophobic and Superoleophilic Properties

An ultrasonic plasticizing and pressing method (UPP) that fully utilizes ultrasonic vibration is proposed for fabricating thermoplastic polymer surface microstructures with high aspect ratios (ARs). The characteristics of UPP are elucidated based on the plasticization of the raw material, the melt flow, and the stress on the template microstructure during the forming process. Initially, the micronscale single-stage micropillar arrays (the highest AR of 4.1) were fabricated by using 304 stainless steel thin sheets with micronscale pore (through-hole) arrays as primary templates. Subsequently, anodic aluminum oxides (AAOs) with ordered nanoscale pore arrays were added as secondary templates, and the micro/nanoscale hierarchical micropillar arrays (the highest AR up to 24.1) were successfully fabricated, which verifies the feasibility and forming capability of UPP. The superiority and achievements of UPP are illustrated by comparing the prepared hierarchical micropillar arrays with those prepared in the previous work in four indexes: microstructure scale, aspect ratio, forming time, and preheating temperature of the raw material. Finally, the water contact angle (WCA) and oil droplet complete immersion time of the surface microstructures were measured by a droplet shape analyzer, and the results indicate that the prepared micropillar arrays are superhydrophobic and superoleophilic.

A rapid two-step process to prepare a high-throughput, efficient, reusable superhydrophobic–superoleophilic stainless steel mesh for oil/water separation

Currently, due to the industrial development, the direct discharge of large amounts of oil-containing wastewater has led to serious water pollution. It is necessary to develop an efficient, durable, and high-throughput material for oil–water separation. To achieve this, we prepared a nickel (Ni) coating with a loose leaf-like micro/nanostructure on the surface of stainless steel mesh (SSM), imparting it with superhydrophobic and superoleophilic properties. The deposition of ions onto the substrate was carefully controlled by adjusting the deposition parameters. Subsequently, the as-prepared Ni coating was further modified using a solution of perfluorooctyltriethoxysilane (PFOTS) in ethanol to obtain a PFOTS/Ni mesh (PNM) with excellent superhydrophobic–superoleophilic properties. Wettability tests revealed that the water contact angle (WCA) and oil contact angle (OCA) of the PNM, prepared under the optimized deposition conditions, were 161 ± 1° and 0°, respectively, with a water sliding angle (WSA) of less than 10°. Importantly, the PNM demonstrated remarkable mechanical stability in blade scratch and tape peel tests, as well as excellent chemical stability in acid-alkali resistance and electrochemical corrosion tests. And, the PNM exhibited remarkable self-cleaning capability. Additionally, PNMit filters displayed outstanding efficiency in separating oil and water (reaching 91.5%) and remarkable durability. The results indicate that the well-designed superhydrophobic–superoleophilic SSM exhibits advantages such as simple fabrication, low cost, high reusability, and strong robustness. It holds great potential for practical applications in the treatment of oily wastewater and oil spill remediation.

Magnetic luffa/graphene/CuFe2O4 sponge for efficient oil/water separation

In this study, a novel magnetic composite material comprising luffa sponge derived graphene aerogel embedded with hollow CuFe2O4 nanospheres (LGN) is successfully synthesised for the first time by a clean and low-cost one-step solvothermal electrostatic co-assembly method. The resultant LGN aerogel exhibits superhydrophobic and superoleophilic properties with the water and oil contact angles of 162.1° and 0°, respectively, along with magnetic properties characterized by the saturation magnetization of 51.6 emu/g, and a large specific surface area of 218.8 m2/g. The saturation sorption capacity of LGN for organic solvents/oil is found to be in the range of 47.6–86.8 g/g, exhibiting an excellent oil/water emulsion separation ability. Through the capillary action, oil and organic solvents spontaneously penetrate into the interior of the aerogel, while the superhydrophobic surface prevents water from entering, thereby enabling the separation of oil and water. These characteristics enable the real-time sorption of organic pollutants from water, with the capability of exhausted sorbent being regenerated. Notably, even after 20 sorption-volatilisation cycles, the saturated sorption capacity of LGN remains high at the 92.2 % of the initial value, demonstrating a remarkable recycling performance. In addition, LGN can exhibit an oriented sorption performance by controlling the applied magnetic field, enabling sorbent recycling even under extreme environmental conditions. Such an effective strategy offers a new route to high value utilisation of biomass waste with significant potential in the field of oil spill treatment.

Superhydrophobic PODS-modified nickel foam with reversible wettability for oil-water separation

In this work, superhydrophobic and superoleophilic nickel foam was fabricated to effectively purify oil-water mixtures. Octadecyltrichlorosilane (OTS) was utilized to form polymerized octadecylsiloxane (PODS) coatings on the nickel foam through hydrolysis and subsequent polycondensation reactions. The surface composition and morphology of the nickel foam were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The initially smooth surface of the nickel foam became rough upon being coated with the PODS. The incorporation of long alkyl chains from the PODS coating, along with the introduced roughness, synergistically provided the nickel foam with superhydrophobic and superoleophilic properties. The PODS-modified nickel foam demonstrated a water contact angle (WCA) of 151.3° and oil contact angle (OCA) of 0°, exhibiting excellent wettability selectivity towards water and oil. Additionally, it showcased a remarkable permeation flux of 7468.4 ± 236.3 L·m−2·h−1 when tested with a water-n-hexane emulsion. This superior performance enabled efficient separation of oil and water. Notably, even after 20 cycles, the PODS-modified nickel foam maintained a separation efficiency of over 98.4 %. Furthermore, the wettability of the PODS-modified nickel foam could be easily switched from superhydrophobicity to superhydrophilicity through a straightforward prewetting treatment using ethanol. In this process, ethanol served as a mediator between the hydrophobic surface and water. Once the prewetted foam was thoroughly dried, the hydrophilic channels were eliminated, thus restoring the superhydrophobicity of the nickel foam. This reversible transition of wettability holds great potential for the development of smart filters capable of effectively addressing diverse challenges in oily wastewater treatment.

Magnetic superhydrophobic melamine sponges for crude oil removal from water

This paper proposes the preparation of a new sorbent material based on melamine sponges (MS) with superhydrophobic, superoleophilic, and magnetic properties. This study involved impregnating the surface of commercially available MS with eco-friendly deep eutectic solvents (DES) and Fe3O4 nanoparticles. The DES selection was based on the screening of 105 eutectic mixtures using COSMO-RS modeling. Other parameters affecting the efficiency and selectivity of oil removal from water were optimized using the Box-Bhenken model. Menthol:Thymol (1:1)@Fe3O4-MS exhibited the highest sorption capacity for real crude oils (101.7–127.3 g/g). This new sponge demonstrated paramagnetic behavior (31.06 emu/g), superhydrophobicity (151°), superoleophobicity (0°), low density (15.6 mg/cm3), high porosity (99 %), and excellent mechanical stability. Furthermore, it allows multiple regeneration processes without losing its sorption capacity. Based on these benefits, Menthol:Thymol (1:1)@Fe3O4-MS shows promise as an efficient, cost-effective, and eco-friendly substitute for the existing sorbents.

Modification of cotton fibers with functional silane and application for emergency treatment of spilled oil or other organic pollutants

Water contamination issues caused by spilled oil or other organic pollutants are urgently requiring the development of new oil sorbent materials that may desirably have the functionalities of reusability and efficiency. To further improve hydrophobicity, sorption capacity and oil retention rate, in this study, cotton modified with vinyl triethoxysilane (VTES, KH-151) to improve them. The introduction of KH-151 onto the surface of cotton was verified by SEM, FT-IR, XPS and EDS. The oil-water selectivity, sorption and retention capacities and cycling performance were tested. Compared with the raw cotton, modified cottons surface enhanced the rate and capacity of oil separation from oily water, the sorption capacity for soybean oil was increased from 9.83 g g–1 to 27.26 g g–1 and for dimethylsilicone oil from 7.92 g g–1 to 25.09 g g–1 after 10 cycles. The oil retention rates of modified cottons exceed 95 % for soybean oil within 10 min at low specific volumes. It gradually decreased by specific volume increasing but still maintained over 75 % at the 14 cm3 g–1. These indicated the hydrophobic and superoleophilic properties, and good recyclability. The developed method and sorbent hold promise for easy storage, environmentally friendly, reusable and relatively cost-effective oil cleanup in emergency treatment of spilled oil or other organic pollutants.

Candle soot nanoparticle embedded nanofibrous membrane for separation of miscible and immiscible oil/water mixtures

AbstractCandle soot (CS) nanoparticles exhibit excellent superhydrophobic and superoleophilic properties, making them an ideal absorbent for separating oil and oil/water mixtures. Although their cost‐effectiveness is attractive, the challenges associated with recovering soot nanoparticles after oil absorption and producing secondary pollutants have limited their attention. Our study demonstrates the synthesis of CS nanoparticles embedded polystyrene (PS) nanofibrous membranes with excellent stability, surface‐to‐volume ratios, and flexibility. CS‐incorporated composite membrane with a rough surface showed a water contact angle (WCA) of 156° ± 1.5°, about 20% higher than the smooth pristine PS membrane. The CS‐based composite membrane also demonstrated improved performance as an absorbent, owing to its hydrophobic characteristics linked with surface roughness when employed for separating oil from oil/water mixtures. Furthermore, when exposed to four different oils, the CS‐based membrane displayed a higher absorption capacity (up to ≈120 g oil/g membrane) than the pristine membrane. Using a gravity‐assisted continuous oil/water separation setup, we measured the oil permeate flux using nanofiber mats as a membrane. Compared to the original membrane, the modified membrane showed enhanced oil permeate flux of ~2873 ± 122 L m−2 h−1 and separation efficiency of over 99%.

Robust 3D porous superhydrophobic foam with excellent photothermal effect and Joule heating effect for efficient all-weather cleanup of highly viscous crude oil spills

Crude oil spill is difficult to deal with and still a global challenge due to its high viscosity. Developing foams with excellent mechanical properties, photothermal effect and Joule heating effect simultaneously to achieve crude oil all-weather recovery is desirable. Here, 3D porous foams were successfully fabricated by the composite of polydimethylsiloxane (PDMS) and multi-walled carbon nanotubes (MWCNT) by a combination of sacrificial template method and laser etching treatment. Benefiting from the low surface energy of PDMS itself and the micro-nano structures constructed in the preparation, the obtained foams exhibit excellent superhydrophobic and superoleophilic properties (WCA of 157° and OCA of 0°). Significantly, MWCNT do not exist as a coating around the foam surface, but as the main component constituting the foam skeleton, so the foam shows excellent mechanical property, low temperature resistance, high temperature resistance, salt resistance and abrasion resistance. Moreover, taking the advantage of the addition of MWCNT, the foam shows excellent photothermal effect requiring 1 sun irradiation to attain a temperature of 60.7 ℃ after 4 min and a stable temperature of 71.6 ℃ after 10 min, and Joule heating effect requiring only 9 V voltage to attain a temperature of 64.5 ℃ after 1.5 min and a stable temperature of 91.1 ℃ after 10 min, respectively. Besides low viscosity oil–water separation, it can achieve rapid crude oil spill recovery under the photothermal effect or Joule heating effect. The combination of the two effects can realize the coupling effect and achieve high-efficiency all-weather high viscosity crude oil recovery, thus making the foam more practical. This foam is expected to be an ideal material for all-weather dealing with oil spills.

PVDF/PLA electrospun fiber membrane impregnated with metal nanoparticles for emulsion separation, surface antimicrobial, and antifouling activities.

Although many superwetting materials have been designed for the treatment of oil-containing wastewater, separation strategies for oil-in-water systems containing bacteria have rarely been reported. Herein, poly(vinylidene difluoride)- and poly(lactic acid)-blended fibrous membranes loaded with silver and copper oxide nanoparticles were successfully prepared by a two-step method of electrostatic spinning and liquid-phase synthesis. The product membrane showed excellent super-oleophilic properties in air and hydrophobicity under oil. It could separate water-in-oil emulsion systems containing surfactants with an efficiency above 90%. More importantly, the nanoparticle-loaded fibers were characterized by material degradability and slowly released ions. The fibers exhibited excellent antibacterial activities against both gram-positive and -negative bacteria. This work provides a feasible strategy for water-in-oil emulsion separation and bacterial treatment of wastewater.

Durable superhydrophobic/superoleophilic melamine foam based on biomass-derived porous carbon and multi-walled carbon nanotube for oil/water separation

In the present study, fabrications of two eco-friendly superhydrophobic/superoleophilic recyclable foamy-based adsorbents for oil/water mixture separation were developed. Hierarchically biomass (celery)-derived porous carbon (PC) and multi-walled carbon nanotube (MWCNT) were firstly synthesized and loaded on pristine melamine foam (MF) by the simple dip-coating approach by combining silicone adhesive to create superhydrophobic/superoleophilic, recyclable, and reusable three-dimensional porous structure. The prepared samples have a large specific surface area of 240 m2/g (MWCNT), 1126 m2/g (PC), and good micro-mesoporous frameworks. The water contact angle (WCA) values of the as-prepared foams, PC/MF and MWCNT/MF, not only were 159.34° ± 1.9° and 156.42° ± 1.6°, respectively but also had oil contact angle (OCA) of equal to 0° for a wide range of oils and organic solvents. Therefore, PC/MF and MWCNT/MF exhibited superhydrophobicity and superoleophilicity properties, which can be considered effective adsorbents in oil/water mixture separations. In this context, superhydrophobic/superoleophilic prepared foams for kind of different oils and organic solvents were shown to have superior separation performance ranges of 54–143 g/g and 46–137 g/g for PC/MF and MWCNT/MF, respectively, suggesting a new effective porous material for separating oil spills. Also, outstanding recyclability and reusability of these structures in the ten adsorption-squeezing cycles indicated that the WCA and sorption capacity has not appreciably changed after soaking into acidic (pH = 2) and alkaline (pH = 12) as well as saline (3.5% NaCl) solutions. More importantly, the reusability and chemical durability of the superhydrophobic samples made them good opportunities for use in different harsh conditions for oil-spill cleanup.

A compressible porous superhydrophobic material constructed by a multi-template high internal phase emulsion method for oil-water separation.

Superhydrophobic porous materials exhibit remarkable stability and exceptional efficacy in combating marine oil spills and containing oily water discharges. This work employed the multi-template high internal phase emulsion method to fabricate a multi-template porous superhydrophobic foam (MTPSF). The materials were characterized through SEM, IR spectroscopy, contact angle measurement, and an electronic universal testing machine. Moreover, the materials' oil-water separation capability, reusability, and compressibility were thoroughly evaluated. The obtained results demonstrate that the material displays a water contact angle of 143° and an oil contact angle of approximately 0°, thus exhibiting superhydrophobic and superoleophilic properties. Consequently, it effectively facilitates the separation of oil slicks and heavy oil underwater. Furthermore, the MTPSF conforms to the second kinetic and Webber-Morris models concerning the oil absorption process. MTPSF exhibits an outstanding oil absorption capacity, ranging from 39.40 to 102.32 g g-1, while showcasing reliable reusability, high recovery efficiency, and excellent compressibility of up to 55%. The above exceptional attributes render the MTPSF highly suitable for oil-water separation applications.

Fabrication of Superhydrophobic/Superoleophilic Bamboo Cellulose Foam for Oil/Water Separation.

Water is an indispensable strategic resource for biological and social development. The problem of oily wastewater pollution originating from oil spillages, industrial discharge and domestic oil pollution has become an extremely serious international challenge. At present, numerous superwetting materials have been applied to effectively separate oil and water. However, most of these materials are difficult to scale and their large-scale application is limited by cost and environmental protection. Herein, a simple, environmentally friendly strategy including sol-gel, freeze-drying and surface hydrophobic modification is presented to fabricate a bamboo cellulose foam with special wetting characteristics. The bamboo cellulose foam is superhydrophobic, with a water contact angle of 160°, and it has the superoleophilic property of instantaneous oil absorption. Owing to the synergistic effect of the three-dimensional network structure of the superhydrophobic bamboo cellulose foam and its hydrophobic composition, it has an excellent oil-absorption performance of 11.5 g/g~37.5 g/g for various types of oil, as well as good recyclability, with an oil (1,2-dichloroethane) absorption capacity of up to 31.5 g/g after 10 cycles. In addition, the prepared cellulose-based foam exhibits an outstanding performance in terms of acid and alkali corrosion resistance. Importantly, owing to bamboo cellulose being a biodegradable, low-cost, natural polymer material that can be easily modified, superhydrophobic/superoleophilic bamboo cellulose foam has great application potential in the field of oily wastewater treatment.

Atmospheric Pressure Plasma-Treated Polyurethane Foam as Reusable Absorbent for Removal of Oils and Organic Solvents from Water.

This paper reports the optimization of a two-step atmospheric pressure plasma process to modify the surface properties of a polyurethane (PU) foam and, specifically, to prepare a superhydrophobic/superoleophilic absorbent for the removal of oils and nonpolar organic solvents from water. In particular, in the first step, an oxygen-containing dielectric barrier discharge (DBD) is used to induce the etching/nanotexturing of the foam surfaces; in the second step, an ethylene-containing DBD enables uniform overcoating with a low-surface-energy hydrocarbon polymer film. The combination of surface nanostructuring and low surface energy ultimately leads to simultaneous superhydrophobic and superoleophilic wetting properties. X-ray photoelectron spectroscopy, scanning electron microscopy and water contact angle measurements are used for the characterization of the samples. The plasma-treated PU foam selectively absorbs various kinds of hydrocarbon-based liquids (i.e., hydrocarbon solvents, mineral oils, motor oil, diesel and gasoline) up to 23 times its own weight, while it completely repels water. These absorption performances are maintained even after 50 absorption/desorption cycles and after immersion in hot water as well as acidic, basic and salt aqueous solutions. The plasma-treated foam can remove mineral oil while floating on the surface of mineral oil/water mixtures with a separation efficiency greater than 99%, which remains unaltered after 20 separation cycles.

Constructing superhydrophobic sands layer with PTFE nanocoating for desert water storage and oil/water separation

Desert sand is one of the most abundant natural resources, its reutilization is of significance and very valuable for the sustainable development of the environment. In this work, to realize the efficient reutilization of desert sand, we developed a facile method to fabricate superhydrophobic sands based on the self-assembly of PTFE nanocoating. The as-prepared sands exhibit simultaneously superhydrophobic and superoleophilic properties with a water contact angle is ∼150° and an oil contact angle is ∼0°. Besides, the applications of the as-prepared functional sands in water storage and oil/water separation were investigated in detail. The results show that the as-prepared sands exhibit good water storage capacity compared with the raw desert sand. Additionally, the as-prepared sand layer used as an adsorbent or filter can efficiently separate both light and heavy oil/water mixtures with a separation efficiency of > 96% and separation flux of > ∼24000 L/m2h. This work provides a good alternative for achieving the reutilization of desert sand and other natural resources.

Reduced graphene aerogels as energy efficient selective oil sorbents

Graphene aerogels are widely used in the oil–water system as they possess high internal surface area and super-oleophilic properties. However, they tend to absorb water along with oil, and to overcome this problem; surface coatings are generally employed using expensive fluoro-silane compounds. It leads to an increase in production costs and environmental concerns. Herein, we report super-hydrophobic 3D graphene aerogels as selective oil sorbent for oil–water​ separation. The reduction of oxygen-containing functional groups on the surface of graphene aerogels has been studied and characterized with FTIR. The thermal treatment of up to 700 °C was carried out using an in-house flow system. The gases used to reduce graphene oxide aerogel are H2 and N2 with an optimized ratio of 5:95. The presence of H2 significantly decreased the oxygen-containing functional groups in graphene aerogel. The increase in the C/O ratio results in higher uptake capacity due to higher surface area and pore volume. The thermal reduction yields a C/O ratio of 24:1, slightly higher than most reported values.