Oil Contact Angle Research Articles

Enhancing the oil/water separation efficiency of polylactic acid fiber membrane via polydimethylsiloxane-polycaprolactone copolymer

Membrane technology is one of the important methods of treating oily wastewater due to low energy consumption. How to design the membrane with high efficiency, biodegradable, reusable and good mechanical properties has attracted increasing interest. In this work, a polydimethylsiloxane-polycaprolactone (PDMS- PCL) was synthesized to endow polylactic acid (PLA) fiber membrane with superhydrophobicity and superoleophilicity via electrospinning without secondary processing. When the blend ratio of PDMS-PCL/PLA is 15wt%, the water contact angle of the fiber membrane is 155.1 ± 3°, and the oil contact angle is almost zero. The tensile strength and elongation at break are 2.05 ± 0.16MPa and 37.9 ± 2.3%, respectively. The fiber membrane exhibited high oil/water separation performance and quick adsorption of oil drop underwater. The permeate flux and separation efficiency for n-hexane are 3550 ± 50L·m-2·h-1 and 99.3 ± 0.2%, separately. It also has excellent self-cleaning and durable properties. The fiber membrane maintains high oil flux, separation efficiency, and mechanical properties after more than 10 rounds of separation. The fiber membrane can resist the external environment variation such as to some extent. The water contact angle of the fiber membrane undergoing friction and heating at 100 °C stably remains at about 150°. The weight loss is little in salt solution. Then this simple efficient method is suitable large-scale production and will promote membrane technologies in application of oil/water separation.

Dopamine triggered the polymerization and co-deposition of HEMA on PVDF membranes to prepare oil-water separation membranes

A one-step co-deposition method based on dopamine and hydrophilic hydroxyethyl methacrylate (HEMA) was proposed for the modification of polyvinylidene fluoride (PVDF) membrane, which could ameliorate its oil-water separation performances and hydrophilicity. A range of modified membranes were prepared by adding different content of HEMA in the reaction solution. For the improved membrane, the minimum water contact angle can reach 13.63°, and the maximum underwater oil contact angle can reach about 150°. The pure water flux for the improved membrane reaches 9668 L·m-2·h-1·bar-1, showing excellent hydrophilicity. In addition, the separation efficiency of the improved membrane for a variety of oil-water emulsions exceeds 98%, indicating good permeability and circulating oil resistance. At the same time, this approach is also applicable to other membranes on account of the extensive availability of dopamine.

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.

A versatile superhydrophilic/air-superoleophobic glass fiber membrane: Fabrication and application in oil/water separation

Superwetting materials have received extensive interest owing to their potential for efficient oil/water separation. Herein, a superhydrophilic-superoleophobic glass fiber membrane was fabricated through a simple spraying coating method. The membrane was coated with a composite layer of methyltrimethoxysilane (MTMS), fluorosurfactant (FS-50) and TiO2 nanoparticles. Accordingly, both hydrophilic groups (i.e., -OH) and oleophobic groups (i.e., fluorinated groups) were distributed on the membrane, and its surface roughness was improved by TiO2. The contact angles of water and oil on the coated membrane were 0° and 156.8° in air, respectively. By virtue of its selective permeability, it demonstrated separation efficiencies larger than 99.2 % for oil/water mixtures, which remained 98.7 % after 40 separation cycles. Furthermore, its separation efficiencies for oil-in-water emulsions were over 98.3 %, which remained 98 % after 10 separation cycles. Owing to its strong superoleophobicity, it displayed prominent anti-oil-fouling performance both in air and underwater. Besides, presence of TiO2 endowed it with photocatalytic capability, enabling it to recover from organic dye pollution. Moreover, the coated membrane maintained superoleophobic after 10 sandpaper-abrading or squeezing cycles. It also exhibited excellent stability under acid/alkali/salt conditions. The study provided new insights for constructing superwetting materials and an effective strategy for oil/water separation.

A robust and high-throughput superhydrophobic-superoleophilic Zn/Ni composite coating prepared on stainless steel mesh for oil-water separation

Frequent oil spills and the discharge of oily wastewater have adverse effects on the environment and ecosystems. Against the backdrop of escalating environmental concerns, developing high-performing and eco-friendly oil-water separation techniques is crucial. In this study, we successfully created a PFOTS-Zn/Ni superhydrophobic-superoleophilic coating, abbreviated as PZNM, by electroplating Zn2+ and Ni2+ on the stainless steel mesh, followed by modification with perfluorooctyltriethoxysilane-ethanol solution. The wettability test results show that the water contact angle (WCA) reaches 161.3°, with a water sliding angle (WSA) of 2°, and the oil contact angle (OCA) is approximately 0°. Subsequently, the PZNM samples were subjected to tests including blade scratching combined with sandpaper abrasion, tape peeling, bending tests, submerging in acidic and alkaline solutions, high-temperature gradient exposure, and electrochemical corrosion to verify their outstanding long-term durability. Most importantly, it can be shaped into a practical continuous oil-water separation device. In the oil-water separation test, it was found that the superhydrophobic-superoleophilic PZNM achieves highly efficient oil-water separation, with a water/n-hexadecane separation efficiency of up to 93.2 % and a water-chloroform separation flux of 6450±30 L·m−2·h−1. The preparation process is straightforward and green, providing an economical solution. This design holds considerable prospects for applications in the domain of oil-water separation.

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.

Modified PVDF ultrafiltration membrane with host–guest supramolecular trapping for efficient separation of multiple organic contaminants

In our modern lifestyle, the cocktail of organic pollutants from everyday items, such as hair dyes, cloth dyes, food colours, hair oils, cooking oils, and agricultural proteins, enters water streams through household pipelines. This unnoticed contamination, growing alarmingly, poses a serious challenge beyond the scope of conventional separation techniques, calling for a comprehensive solution. While membrane technology offers a promising solution, it grapples with persistent surface fouling issues. This study introduces a novel approach through the development of extraordinary Polyvinylidene fluoride-Montmorillonite-Cucurbit[6]uril (PVDF-M-CB[6]) mixed matrix membranes, presenting a potential breakthrough in overcoming surface fouling challenges and offering a versatile solution for the separation of an array of organic contaminants. Powered by the synergistic host–guest supramolecular complexation of CB[6] onto montmorillonite (M) clay support, these membranes demonstrate swift and selective encapsulation, leading to superior cationic dye rejection. Adding to the allure, CB[6]’s structure encourages favorable carbonyl interactions with bovine serum albumin (BSA), effectively repelling the protein away from the membrane, while also promoting seamless oil–water emulsion separation with an underwater oil contact angle of 150 ± 3°, displaying its superoleophobic nature and enhancing remarkable antifouling properties. The PV-M-CB[6] membranes showcased 2x removal of cationic dyes, 1.3x removal of anionic dyes, 1.4x oil–water emulsion separation, and 2x BSA separation compared to the pristine polyvinylidene fluoride (PVDF) membrane. These membranes displayed 98.3 % efficiency in oil–water emulsion separation and sustained a flux recovery ratio of over >75% after seven cycles. Overall, PV-M-CB[6] membranes represent an innovative solution with heightened hydrophilicity, remarkable antifouling performance, and exceptional proficiency in delivering one-stop organic foulant separation.

Superhydrophobic/superoleophilic polyurethane /reduced graphene oxide/ sponge for efficient oil-water separation and photothermal remediation

Due to the rapid development of global industrialization, the frequent occurrence of organic matter leakage and oil leakage accidents has led to increasingly serious environmental pollution. Therefore, this paper has proposed a facile and affordable method for creating oil water separation materials, and successful creating a super hydrophobic/super oleophilic functional porous polyurethane sponge modified by reduced graphene oxide and polydopamine (PDA-rGO-PU). Dopamine undergoes a self-polymerization event that creates polydopamine, which is subsequently coated on a polyurethane framework to create a sponge structure with several active sites. The surface of the modified sponge structure was coated with graphene oxide by a simple drop-coating method, and graphene oxide coated on the surface of polydopamine was reduced to create the superhydrophobic/superoleophilic material. The PDA-rGO-PU demonstrated strong anti-adhesion properties and a high oil-water separation efficiency of 99.8 % while having high water contact angles of 155 ° ± 3 ° and oil contact angles (OCA) of 0 °. It has a strong ability to adsorb various oils and organic solvents, the excellent photothermal effect allows PDA-rGO-PU to raise temperature by 37.9 % in the presence of light. PDA-rGO-PU has good continuous oil sorption performance after installing the pump. When under simulated lighting conditions, the sorption time of modified sponge on crude oil was shortened by 2.3 times.

Enhancing mechanical properties of cellulose acetate/carbon black nanofibers for oil spill cleanup

Oil contamination caused by various oil-related industries and domestic usage is one of the major global challenges that threaten the environment. Therefore, employing efficient and environmentally friendly methods for oil removal from oily water is crucial. Nanofibers offer suitable mediums for such applications due to their low fiber diameter and high surface area. Herein, mechanically enhanced carbon black (CB) loaded-cellulose acetate (CA) nanofiber mats were developed for oil removal applications. Initially, CA/CB nanofibers were fabricated from 15% wt. CA solutions containing 2% wt. CB. To improve the mechanical properties, the samples were treated in an ethanol:acetone bath for 2 and 4h. Increasing post-treatment duration increased the nanofiber diameters from 438 nm to 601 nm and decreased porosities from 75% to 66%. The post-treatments improved the mechanical properties of the samples and the highest modulus was achieved as 20.85 MPa. The water and oil contact angles increased from 86° to 102° and 61° to 80°, respectively. The liquid absorption and retention capacities of the samples were evaluated by immersing them in water, seawater, waste oil, and their emulsions. Despite their lower initial oil absorption compared to the non-treated one, post-treated samples still retained large amounts of oil at the end of 24 h.

Facile fabrication of multifunctional superhydrophilic composite membranes for efficient oil-in-water emulsion separation

Numerous superwetting separation membranes have been designed for the management of oily wastewater due to their highly efficient oil/water separation efficiency. However, the long-term stability of these developed membranes is still restricted by membrane fouling. In this study, we synthesized multifunctional superhydrophilic membranes with superior anti-adhesive and anti-biofouling properties through simple co-deposition of dopamine, polyethyleneimine and CoFe2O4 (CFO) photocatalyst on the porous PVDF substrates for sustainable management of oil-in-water emulsion. The resultant optimal composite membranes showed the superhydropilicity with an underwater oil contact angle of 162.4° and achieved ca. 99.51 % oil/water separation efficiency with a maximum permeability of 232.2 L·m−2·h−1 in the treatment of oil-in-water emulsions driven by gravity. Moreover, the outstanding antibacterial performance of composite membrane was demonstrated by a nearly 100 % antibacterial rate during the exposure in 120-min visible light irradiation. Based on the synergistic effect of superhydrophilicity and photocatalysis, the fabricated composite membranes experienced a stable gravity-driven oil/water separation (oil rejection: >99.46 %) even after a 50-cycle filtration. Such an impressive filtration performance of the polydopamine/PEI/CFO composite membranes highlights their promising potential for sustainable and efficient treatment of oily wastewater.

Preparation of superhydrophobic/oleophobic wood coating with fluorinated silica sol by a simple spraying method

The biomimetic construction of superhydrophobic coatings on wood surfaces significantly reduces the water absorption capacity of wood while enhancing its deformation resistance, thereby extending the service life of wooden structures. In this work, a fluorinated silica sol was prepared from alkaline silica sol and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDMS), and evenly sprayed over the wood surface to effectively produce superhydrophobic/oleophobic wood specimens. The effect of the preparation procedure of fluorinated silica sol on the wettability of the coating was investigated. Acid and alkali corrosion tests were conducted to assess the chemical stability of the superhydrophobic coating, while sandpaper abrasion tests were used to evaluate its mechanical stability. The results showed that with a volume ratio of silica sol to PFDMS of 6:1 and a reaction period of 30 min, the modified wood exhibited excellent superhydrophobicity, with a water contact angle of 157.3° and an oil contact angle of 126.5°. Furthermore, the superhydrophobic coating demonstrated excellent mechanical and chemical durability, along with self-cleaning properties. These findings have significant practical implications for enhancing the performance and longevity of wood.

Preparation of a rubber nanocomposite for oil/water separation using surface functionalized/silanized carbon black nanoparticles

Clean water is the basic need of living organisms on the earth. Oil spills to free waters is one of the most important threats to living beings. It has been believed that using sorbents is the most effective method for this purpose. In this research, usage of tire rubber with improved hydrophobic properties is considered. For this purpose, carbon black nanoparticles (CBNs) were surface modified with vinyltrimthoxysilane (VTMS) at concentrations of 1, 5 and 10 by sol-gel method. Before, the CBNs were hydroxylated to increase silane grafting content. The surface modified was evaluated using XPS, FTIR, TGA, BET and FESEM analysis. Results showed a great change in the CBNs nature from hydrophilic to hydrophobic after silane modification that could help in more oil absorption and water repletion at the same time. In fact, the water contact angle (WCA) of the CBNs changed from 40 to 135°. The pure and silane grafted CBNs were added to the tire tread compound to prepare elastomeric nanocomposites as oil sorbent. The results showed that the modified nanocomposite had a higher reinforcement index than the samples contained pure and hydroxylated CBNs. The effects of CBNs on WCA, OCA and oil absorption capacity of the samples were also determined. It was found that silane modification a considerable increase in the WCA from 61.2° to 125.03° and a decrease in the oil contact angle (OCA) from 70.01° to 17.74°. Also, the oil absorption capacity of rubber enhanced from 0.55 to 1.95 g/g.

In situ gel-forming oil solubilizing α-lipoic acid as a physical shielding alleviated chemotherapy-induced oral mucositis via inhibiting oxidative stress

Oral mucositis (OM) is a common and serious complication of cancer chemoradiotherapy. OM managements mainly focused on topical healthcare or analgesia, which offers limited wound healing. Herein, in situ gel-forming oil (LGF) have been developed as a physical shielding for OM treatment. LGF oil, composed of soybean phosphatidyl choline (40 %, w/w), glycerol dioleate (54 %, w/w), and alcohols (6 %, w/w), is a viscous oil-like liquid. The contact angle of LGF oil on porcine buccal mucosa were 30°, significantly smaller than that of water (60°), indicating its good wetting and spreading properties. Besides, the adhesion force and adhesion energy of LGF oil toward porcine buccal mucosa was as high as 3.9 ± 0.2 N and 60 ± 2 J/m2, respectively, indicating its good adhesive property. Moreover, the hydrophobic α-lipoic acid (LA) as a native antioxidative agent was highly solubilized in LGF oil, its solubility in which was above 100 mg/mL. Upon contacting with saliva, LA-loaded LGF oil (LA-LGF) could rapidly transform from oil into gel that adheres on oral mucosa. Moreover, LA was slowly released from the formed LA-LGF gel, which benefited alleviating oxidative stress caused by chemoradiotherapy. In vivo animal experiments showed that LA-LGF could effectively promote the repairing of oral mucosa wound of 5-fluorouracil induced OM rats. Besides, the mucosa edema was greatly improved and new granulation around wound was produced after LA-LGF treatment. Meanwhile, the production of proinflammatory cytokines such as IL-1β, TNF-α, 1L-6 was substantially inhibited by LA-LGF. Collectively, LGF oil as carrier of hydrophobic drug might be a promising strategy for oral mucositis.

The Preparation and Properties of a Ni-SiO2 Superamphiphobic Coating Obtained by Electrodeposition

Superamphiphobic coatings have shown great potential in many fields such as with their anti-corrosion, high-temperature resistance, self-cleaning, and drag reduction properties. However, due to the poor stability of their coatings, it is difficult to apply them on a large scale. In this paper, two kinds of SiO2 particles and nickel were co-deposited on the surface of steel to construct a micro/nano dual-scale structure by composite electrodeposition. The surface of the coating was then fluorinated with the low-surface-energy material 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (AC-FAS) to prepare a Ni-SiO2 superamphiphobic coating. The coating has a water contact angle of 159° and an oil contact angle of 151°. The effect of nanoparticle concentration on the wettability and surface morphology of the coating was systematically studied. Comparative experiments revealed that the optimal micro/nanoparticle concentrations were 8 g/L of 20 nm SiO2 and 2 g/L of 1 μm SiO2. This preparation method greatly improves the corrosion resistance, wear resistance, chemical stability, and high-temperature resistance of the coating.

Preparation and Properties of Lightweight Amphiphobic Proppant for Hydraulic Fracturing.

The wettability of the proppant is crucial in optimizing the flowback of fracturing fluids and improving the recovery of the produced hydrocarbons. Neutral wet proppants have been proven to improve the fluid flow by reducing the interaction between the fluid and the proppant surface. In this study, a lightweight amphiphobic proppant (LWAP) was prepared by coating a lightweight ceramic proppant (LWCP) with phenolic resin, epoxy resin, polytetrafluoroethylene (PTFE), and trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane (TMHFS) using a layer-by-layer method. The results indicated that the LWAP exhibited a breakage ratio of 2% under 52 MPa (7.5 K) closure stress, with an apparent density of 2.12 g/cm3 and a bulk density of 1.21 g/cm3. The contact angles of water and olive oil were 125° and 104°, respectively, changing to 124° and 96° after displacement by water and diesel oil. A comparison showed that the LWAP could transport over a significantly longer distance than the LWCP, with the length increasing by more than 80%. Meanwhile, the LWAP displayed notable resistance to scale deposition on the proppant surface compared to the LWCP. Furthermore, the maintained conductivity of the LWAP was higher than that of the LWCP after displacement by water and oil phases alternately. The modified proppant could minimize production declines during hydrocarbon extraction in unconventional reservoirs.

A novel formulation of an eco-friendly calcium nitrate-based heavy completion fluid

Calcium-nitrate-based transparent completion fluids are widely used in the oil and gas industry for well completion and stimulation operations in carbonate reservoirs. These fluids have many advantages, such as medium density, low corrosion, good temperature stability, low clay swelling, and high wettability. However, the density of calcium nitrate brine is limited by its solubility, which can be increased by the addition of alcohols. This study investigated the effects of adding different types of alcohols (G1, G2, and G3) to calcium nitrate brine on the properties and performance of the completion fluid for carbonate reservoirs. The fluid properties and performance were evaluated through a series of laboratory tests, including density measurement, corrosion test, viscosity measurement, rheology test, temperature stability test, clay swelling test, wettability test, and compatibility test. The results showed that the addition of alcohols to brine can improve or reduce the fluid density, viscosity, corrosion, temperature stability, clay swelling, wettability, and compatibility, depending on the type and amount of alcohols. The optimum fluids have been selected based on their highest density, lowest viscosity, lowest corrosion, highest temperature stability, lowest clay swelling, highest wettability change, and highest compatibility with formation fluids. The densities of the fluids CN4, CNG14, CNG24, and CNG34 were respectively 96, 101, 101.5, and 100 pounds per cubic foot (pcf). Their rates of corrosion on L80 steel were respectively 0.829, 0.589, 0.720, and 0.599 mils per year (mpy). Their apparent viscosities at 62.4 °F were respectively around 15, 120, 100, and 60 centipoise (cp). Their apparent viscosities at 176 °F were all around 10 to 25 mpy. The fluids remained clear with no evidence of suspended solid particles at 20 °F, indicating their resilience to low-temperature conditions and suitability for use in cold weather operations. The fluid CNG24 becomes cloudy at 285 °F, and the fluid CNG34 becomes cloudy from 212 °F onward, but the CN4 fluid remains clear and transparent at all temperatures. In the tested high temperatures, the effect on their pH was around the same. The fluids CN4, CNG24, and CNG34 had a lower swelling index than 5 ml per 2 g of bentonite clay. The contact angles of oil and carbonate-type thin sections after their wettabilities were affected by the fluids were also 99.5, 36.54, and 46.03°, respectively. Finally, they’re all relatively compatible with formation fluids. The best completion fluid for carbonate reservoirs was CNG24, which contained calcium nitrate and G2 alcohol. This fluid had the best overall performance and safety of the fluids tested.

Super-hydrophilic membranes fabricated by synergistic integration of covalent organic framework nanoflowers and hydrophilic layers for efficient oil-water separation

Despite numerous advancements, the development of super-hydrophilic membranes for efficient oil-water separation remains a significant challenge due to issues such as membrane fouling and the trade-off between selectivity and permeability. This study addresses these issues by innovatively integrating covalent organic framework nanoflowers with hydrophilic layers of polydopamine and polyethylene glycol. The research introduces a novel membrane, DP/COF3/PVDF, fabricated through a layer-by-layer self-assembly process and subsequent co-deposition of dopamine and PEG, which combines the nanostructured COF with a hydrophilic coating. Experimental results reveal that the optimized membrane exhibits remarkable hydrophilicity, with a water contact angle of 17.0° and an underwater oil contact angle of 176.9°. Notably, the membrane achieves an impressive pure water flux of 3919.9 L m−2 h−1 bar−1 and a rejection rate exceeding 98.0 % across various oil-water emulsions, significantly outperforming traditional membranes. The membrane exhibits superior antifouling capabilities and stability over ten cycles of use, with negligible flux decline and consistent rejection rates, showcasing robust durability and reusability. This study's findings highlight the potential for developing next-generation super-hydrophilic membranes with improved oil-water separation efficiency and durability.

Superhydrophilic‐underwater superoleophobic polyvinyl alcohol membranes for oily water treatment

AbstractPolyvinyl alcohol (PVA) and potato starch‐based porous hydrogels have been fabricated and studied for their wettability. The starting material was crosslinked by glutaraldehyde performed via co‐polymerization reaction at room temperature and low temperature (freeze–thaw). The gels were characterized by Fourier transform infrared (FT‐IR), field emission scanning electron microscope (FE‐SEM), thermogravimetric (TG), and powder X‐ray diffraction (PXRD) analysis. The wetting studies of the gels were evaluated at ambient and submerged conditions by considering both oil and water drops as probe liquids. The gels tend to absorb oil and water in air, however, water‐wet gels demonstrated a very high oil contact angle (>150°). The gels demonstrated superoleophobicity, and the underwater oil CA >172° as the concentration (wt%) of PVA was increased in the gels. Overall, the freeze–thaw gels demonstrated higher underwater oil CA, however, both (room temperature and freeze–thaw fabricated) gels demonstrated similar affinity for under‐oil–water absorption and separation. The hydrogel can retain water easily and thus remove water (even dye dissolved in water) with high separation efficiency and recyclability.

Experimental and theoretical assessment of bioinspired next-generation intercalated graphene oxide-based ceramic membranes for oil-in-water emulsion separation

2D graphene oxide (GO) membranes are gaining prominence for water reclamation from oily wastewater. Unresolved challenges include low membrane permeance from tight sheets and fouling during separation. In this work, a bioinspired Arabic gum (AG) was used as an intercalated agent with the help of glutaraldehyde to improve the GO membranes’ permeation and fouling resistance. The 2D-laminated separating layer is crafted through a self-assembling innovative approach utilizing pressurized dead-end assembly. The Arabic gum intercalated graphene oxide-modified ceramic membrane (AGIGO-CM) appeared superhydrophilic and underwater (UW) superoleophobic with a UW oil contact angle (UWOCA) of 156.1 ± 1.2°. The membrane prepared with 1 mg of AGIGO (AGIGO-1-CM) offers a flux of 17 times higher than pristine graphene oxide (p-GO) while maintaining a separation efficiency of >99% during the separation of the oil-in-water emulsions. Molecular dynamics (MD) simulations showed AG intercalation expanding the interlayer distance by up to 20 Å, with AGIGO having a higher fractional free volume (FFV) of 0.986 compared to p-GO’s 0.599. AGIGO-CM displayed lower interfacial formation energy (EIFE) of −1865.2 kcal/mol versus −765.5 kcal/mol for p-GO, indicating easier separation. It is further supported by the substantial interfacial thickness of 148 Å for AGIGO-CM compared to 53.0 Å for the p-GO membranes. AGIGO-CM showed minimal fouling, retaining >99% separation efficiency for 6 h. Compared to p-GO-CM, AGIGO-CM flux decreased by only 17.84% versus 44.72%. AGIGO-CM exhibited stability even in acidic and basic environments, showcasing its potential for high performance.

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.