Excellent Oil-water Separation Research Articles

Natural grass to all-biomass biodegradable tape and superior oil-water separation fabric

Valorization of agricultural and forestry wastes is a promising and meaningful strategy to turn wastes into treasure. Here, we developed a simple and easy-to-scale method to fabricate all-biomass biodegradable tape and superior oil-water separation fabric from the natural grass. The natural Hybrid Pennisetum grass was transformed into the biodegradable and low-cost tapes by partially removing hemicellulose to destroy “biomass recalcitrance” and following a direct dissolution/regeneration process in ionic liquids, because the regenerated all-biomass films from grass exhibit high tensile strength of 58.6 ± 2.9 MPa, which achieves the standard of engineering plastics. In addition, the all-biomass ultrafine fibers with micron-scale diameters were prepared by the air-blowing spinning process. Due to the outstanding hydrophilicity and under-water super-hydrophobicity, the non-woven fabric consisting of 8–12 μm fibers had excellent oil-water separation performance with a super-high flux of exceed 25,000 L•m −2•h −1 (only with gravity) and an extremely high separation efficiency of 100%, which are much better than the previous reports. Furthermore, the all-biomass oil-water separation fabric can be easily prepared and is completely feasible in the high salty solution and acid/alkaline solution. Therefore, a simple and practical process is demonstrated to construct high-performance matetials from low-cost biomass wastes, providing a huge potential in circular economy, environmental protection and bioresource utilization.

Multifunctional fluorine‐free superhydrophobic coating with flame‐retardant, anti‐icing, anti‐corrosion, and oil–water separation properties

A fluorine-free and multifunctional superhydrophobic coating (r-MSC) was prepared by the one-step spraying method. The coating had superhydrophobic and low-adhesion properties with the water contact angle of 161.5° ± 1° and the sliding angle of 3.2° ± 0.5°. It could be prepared by spraying while maintaining superhydrophobic surface characteristics on any substrates. The coating owed outstanding mechanical durability and chemical stability. Moreover, the coating also possessed the ability of self-cleaning, anti-fouling, anti-icing, and flame retardant ability. Importantly, the presence of multifunctional coating endowed the substrate with both water-resistant and fireproof properties. Besides, it also showed excellent oil-water separation ability, which presented the oil-water separation efficiency of over 90% for different types of oils after 10 separation cycles. Furthermore, the coating could improve corrosion inhibition performance and the corrosion current density was reduced by two orders of magnitude from the polarization curve. The r-MSC had the advantages of simple preparation, fluorine-free, environmentally friendly and appropriate for large-area fabrication, which could be applied to various fields.

Fabrication of novel superhydrophilic/underwater superoleophobic composite coatings and study on the relationship between their long-term wettability and excellent oil-water separation performance

A superhydrophilic/underwater superoleophobic composite coating (ES@SSM) was fabricated through etching and subsequent modification of stainless steel mesh (SSM). It had a water contact angle of 0° in the air, an oleophobic angle of 162.7° underwater, and a sliding angle of 5°. Even after 15 days, the separation efficiency of crude oil-water was up to 98.6% and had a high water flux of 13535 L m−2 h−1. After 50 sandy impacts, the ES@SSM had an oil contact angle of 158.5° and sliding angles of 13° underwater. Experimental results show that the water flux and the contact angle were closely related, and there was a negative correlation between the water flux and the water contact angle. Furthermore, the ES@SSM was featured with long-term stability, chemical stability and excellent mechanical stability. Apart from that, it has potential application value in the field of oil and water treatment.

Mussel-Inspired Fabrication of PDA@PAN Electrospun Nanofibrous Membrane for Oil-in-Water Emulsion Separation.

Emulsified oily wastewater threatens human health seriously, and traditional technologies are unable to separate emulsion containing small sized oil droplets. Currently, oil–water emulsions are usually separated by special wettability membranes, and researchers are devoted to developing membranes with excellent antifouling performance and high permeability. Herein, a novel, simple and low-cost method has been proposed for the separation of emulsion containing surfactants. Polyacrylonitrile (PAN) nanofibers were prepared via electrospinning and then coated by polydopamine (PDA) by using self-polymerization reactions in aqueous solutions. The morphology, structure and oil-in-water emulsion separation properties of the as-prepared PDA@PAN nanofibrous membrane were tested. The results show that PDA@PAN nanofibrous membrane has superhydrophilicity and almost no adhesion to crude oil in water, which exhibits excellent oil–water separation ability. The permeability and separation efficiency of n-hexane/water emulsion are up to 1570 Lm−2 h−1 bar−1 and 96.1%, respectively. Furthermore, after 10 cycles of separation, the permeability and separation efficiency values do not decrease significantly, indicating its good recycling performance. This research develops a new method for preparing oil–water separation membrane, which can be used for efficient oil-in-water emulsion separation.

Synergistic effect of nano-silica and eco-friendly hydrogel for the cost-effective and highly efficient oil-water separation

Reported herein is a novel eco-friendly and low-cost oil-water separation mesh that can achieve a high separation efficiency up to 99%, while the prepared mesh maintained excellent performance even after immersion in salty water for 5 days, or cycle use for 20 times. The superhydrophilic and underwater superoleophobic mesh was modified with a layer of rough nano silica by soot template method firstly, and then the mesh was covered with the calcium alginate hydrogel coating via a simple dip-coating method. The synergistic effect of the low-cost nano-silica and environmentally friendly calcium alginate hydrogel not only endowed the mesh with outstanding oil-water separation performance but also overcame the shortcoming of high-cost and pollutive in the fabrication of oil-water separation materials. The prepared mesh maintained excellent oil-water separation efficiency and water permeation flux, even after treatment in various harsh environments. The cost-effective and eco-friendly oil-water separation mesh holds great potential in the treatment of industrial and domestic waste oil.

High-efficient novel super-wetting HKUST-1 membrane for oil-water separation: Development, characterization and performance

In the current work, novel super-wetting HKUST-1 membrane was fabricated via seed-mediated growth method. These HKUST-1 crystal seeds were successfully sprouted on the polydopamine coated stainless steel mesh surface. The characterization results showed that the as-prepared membrane had an excellent superhydrophilic and underwater superoleophobic property because of the presence of polydopamine and HKUST-1 crystal seeds. Meanwhile, the membrane still maintained high separation flux and separation efficiency after high temperature treatment and immersion in different concentrations of acid-base salt solutions, which indicated that the HKUST-1 membrane has excellent thermal stability and chemical stability. The as-prepared membrane also showed remarkable anti-fouling performance and self-cleaning property to crude oil. Moreover, the as-prepared membrane achieved an excellent separation efficiency against four different oil-water mixtures just driven by gravity. The continuous separation tests and oil-water separation in different acid, alkali and salt environments indicated that the as-prepared membrane had an excellent oil-water separation performance for practical applications. The oil-water efficiency was over 99% and the pure water flux was up to 11.1 × 104 L m−2 h−1.

Preparation and characterization of super hydrophobic aerogels derived from tunicate cellulose nanocrystals

First time aerogels composite with super hydrophobic properties were developed by using tunicate cellulose nanocrystals (TCNC), which expanded the application scope of animal cellulose resources. In this study, the TCNC was firstly cross-linked with silica and methyltrimethylsilane (MTMS), further coated with fluorodopa to form an aerogel with super hydrophobic properties. The aerogel was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). Results indicated that the contact angle of aerogel was 158.7°, which showed good hydrophobicity. The composite aerogel has superior stability in wide pH range, after 72 h immersion in pH = 0 and 12 solutions, the contact angle was still greater than 150°. The aerogel shows excellent oil-water separation ability and it can be repeatedly used more than 10 times. The separation efficiency can all reach more than 90% for different water-oil mixtures. This synthesized super hydrophobic aerogels derived from tunicate cellulose has greatly extended the application of marine animal celluloses.

Zwitterionic hydrogel-coated cotton fabrics with underwater superoleophobic, self-healing and anti-fouling performances for oil-water separation

• Zwitterionic hydrogel with self-healing property was coated on the cotton fabric. • The coated fabric exhibited anti-fouling and underwater superoleophobic properties. • The coated fabric had superior oil/water separation property under gravity drive. • The coated fabric displayed the outstanding cyclic stability and reusability. Oil-water separation technology has attracted widespread attention, due to the increasingly serious oil pollution. In this work, novel poly(sulfobetaine methacrylate- co -2-hydroxyethyl acrylate)/poly(vinyl alcohol)/borax (PSBMA/PVA/Borax) hydrogels were prepared. Then, the related gel-coated cotton fabrics for oil-water separation were successfully developed in a facile route. The results presented the as-prepared zwitterionic hydrogels had outstanding self-healing ability, low swelling ratio, and satisfactory mechanical properties because of multiple interactions in the hydrogel’s network. As expected, the zwitterionic hydrogel-coated cotton fabric was imparted with excellent underwater superoleophobicity and outstanding anti-fouling ability due to the existence of zwitterionic groups on the surface. The underwater oil contact angle of the as-prepared fabric was approximately 160° towards a series of oils. Meanwhile, oily contaminations on the zwitterionic hydrogel-coated fabric surface can be rapidly removed just by water immersion. Most importantly, the zwitterionic hydrogel-coated fabric exhibited excellent oil-water separation efficiency (approximately 99%) and water flux (about 15, 181 L -1 ·m −2 ·h −1 ) even after 50 successive cycles. Additionally, the zwitterionic hydrogel-coated fabric also presented remarkable chemical and mechanical stabilities in harsh conditions. The as-prepared cotton fabric presents a great application prospect in oily wastewater treatment.

Synthesis of cellulose based super absorbent and its excellent oil–water separation properties

AbstractThe work reported aims to developing the grafted cellulose fiber‐based material (polyethylene wax‐grafted maleic anhydride)/cellulose fiber; PEW‐g‐MA/CF) for efficient absorption of oil from aqueous solution. PEW‐g‐MA/CF was prepared via grafting modification between cellulose fiber and the maleic anhydride modified polyethylene wax, resulting in a cost‐effective approach for synthesizing cellulose‐based oil super absorbent. The as‐prepared PEW‐g‐MA/CF was systematically characterized via Fourier‐transform infrared, atomic force microscope, and thermogravimetric; the influencing factors of oil absorption, including the weight ratio of the raw materials, reaction temperature, and reaction time, were studied and compared. The maximum oil absorbency was up to 19.36 g/g‐1 with the condition of weight ratio 1:1; temperature 60°C; and reaction time 3 h. Overall, PEW‐g‐MA/CF is an environmentally friendly and cost‐effective material for high oil absorption from aqueous solution, and the valuable findings might provide an idea for maximizing the potential of the cellulose‐based absorbents for a variety of applications.

Imparting Superhydrophobicity to Porphyrinic Coordination Frameworks Using Organotin

Imparting Superhydrophobicity to Porphyrinic Coordination Frameworks Using Organotin

Recycled carbon fiber nonwoven functionalized with fluorine-free superhydrophobic PDMS/ZIF-8 coating for efficient oil-water separation

This study introduces a feasible approach for producing a functional nonwoven from carbon fiber waste and demonstrates its excellent performance in oil-water separation. Carbon fiber scraps were recycled into a nonwoven product through conventional textile processing methods of carding and needle-punching, followed by surface modification with fluorine-free coatings containing polydimethylsiloxane (PDMS) and zeolite imidazole framework-8 (ZIF-8) particles. The capacity of PDMS/ZIF-8 coating to impart superhydrophobic-superoleophilic properties to the developed nonwoven was investigated, particularly for organic solvents/oils absorption, and oil-water separation. Different characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), BET surface area, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) were used to characterize the synthesized ZIF-8 particles and developed coatings. The results showed that the application of PDMS initially increased the water contact angle, but its excess amount lowered the superhydrophobicity and absorption capacity of coated nonwovens. The presence of ZIF-8 particles boosted the superhydrophobicity and absorption capacity where the sample coated with PDMS/ZIF-8 exhibited superior superhydrophobicity having a water contact angle of 153.5°. The PDMS/ZIF-8 coated nonwoven displayed a highly efficient gravity-driven and continuous oil-water separation performance. This research presents a sustainable approach to the development of a multifunctional carbon fiber nonwoven with excellent oil-water separation capability from waste materials.

Low-temperature carbonization synthesis of carbon-based super-hydrophobic foam for efficient multi-state oil/water separation

In view of the complexity and diversity of multi-state oils, the development of green and low-cost materials with high selectivity to oils has important ecological significance in the polluted water treatment. Herein, a simple method was proposed to develop large-scale production of superhydrophobic sponges (CPMF200 sponges) for high-efficiency oil/water separation under different complex environments. The as-prepared CPMF200 sponges possessed many superior properties, including high roughness, well-developed porosity, good thermal stability, excellent chemical stability, and superhydrophobic properties (water contact angle is 152°), which is conducive to high oil adsorption capacity (up to 70–179 times of its own weight) and oil-water separation. More importantly, the CPMF400 sponge has an excellent photothermal conversion capability to improve the fluidity of high viscosity oil for oil recovery. Based on a simple synthesis method, it exhibits high-efficiency absorption of multi-state oils and excellent oil-water separation performance and strongly proves their application prospects in treating oily wastewater.

Robust CuO micro-cone decorated membrane with superhydrophilicity applied for oil–water separation and anti-viscous-oil fouling

Oil pollution caused by oil spills and oily wastewater has become a global issue. Oil–water separation with help of membrane possessing special wettability is a significant and feasible solution. The special wettability can be achieved by many materials. However, recent researches still have several limits for practical application. Herein, we report a surface of CuO with special microstructure, which is achieved by a simple thermal oxidation treatment of the Cu micro-cone decorated membrane. In the dynamite contact angle test, the CuO micro-cone decorated membrane exhibits higher water affinity than Cu micro-cone decorated membrane and superhydrophilicity with a water contact angle of 0°. In addition, the special micro-cone structure of CuO contributes to high mechanical and thermal stability (up to 400 °C). Furthermore, the CuO micro-cone decorated membrane presents its practical applications for oil–water separation and anti-fouling property for various viscous oils. We believe this membrane with robust stability and superhydrophilicity has great potential for practical applications in oil pollutant treatment. • A CuO micro-cone decorated membrane is synthesized by a simple and economical method. • The membrane exhibits superhydrophilicity, superior mechanical and thermal stability. • The membrane shows excellent oil–water separation and anti-fouling property.

In-situ construction of MOFs-based superhydrophobic/superoleophilic coating on filter paper with self-cleaning and antibacterial activity for efficient oil/water separation

Superhydrophobic/superoleophilic paper with excellent self-cleaning and antibacterial activity was prepared via combination of in-situ growing Cu metal-organic frameworks (Cu-MOFs) nanoparticles on paper surface by simple layer-by-layer assembly together with subsequent polydimethylsiloxane (PDMS) treatment under ambient conditions. The surface chemical composition, crystalline pattern, surface chemical functional group, surface morphology and wettability of the modified paper samples were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscope and water contact angle measurement. The synergetic effect of Cu-MOFs nanoparticles and PDMS was crucial and essential for achieving a superhydrophobic surface. The PDMS/(Cu-MOFs) 5 @paper not only showed self-cleaning, antibacterial activity and superhydrophobicity/superoleophilicity, but also exhibited excellent oil-water separation performance for oil-water mixture and emulsion. In addition, this obtained superhydrophobic paper showed good mechanical and chemical durability. In summary, the proposed method provides a new perspective into preparing superhydrophobic paper for oil spills treatment and environmental remediation.

Robust superhydrophilic and underwater superoleophobic membrane optimized by Cu doping modified metal-organic frameworks for oil-water separation and water purification

The traditional oil-water separation methods suffer from many problems such as low separation efficiency, high energy consumption, and rapid contamination by oil. We fabricated superhydrophilic and underwater superoleophobic stainless steel mesh (SSM), which was modified by copper mesh (CM) doped UiO-66-NH2, named SSM/UiO-66-NH2/CMn, for efficient oil-water separation and organic matter degradation. Our fabrication strategy mainly includes the growth of structural tunable metal-organic frameworks (MOF, UiO-66) on metal meshes via hydrothermal reaction. The UiO-66 was doped and modified by reusable copper mesh, which enhanced the hydrophilicity and photocatalytic properties of the mesh. The SEM, XRD, AFM, FTIR, and XPS characterizations demonstrated that the meshes were successfully prepared and showed a rough structure surface. In virtue of the special wetting and robustness, the prepared meshes could maintain superhydrophilicity and underwater superoleophobicity with underwater oil contact angle (UWOCA) above 150° after oil/water separation at extreme conditions, including high salt concentrations, low/high temperatures, presence of organic solvents, alkaline and acidic solutions, sandpaper friction, and long-time UV irradiation. Even under harsh conditions, the mesh showed an excellent oil-water separation efficiency of up to 99.7%. Moreover, the fabricated meshes can degrade dye pollutants under visible light with a degradation rate of 99.5% within 80 min, which solves the dependence of traditional photocatalysts on UV and improves solar energy utilization. This research paves the way for preparing super wetting membranes for oil-water separation and organic matter degradation in actual complex oily wastewater.

Durable hydrophobic Enteromorpha design for controlling oil spills in marine environment prepared by organosilane modification for efficient oil-water separation

Hydrophobic and oleophilic materials are attractive candidates for efficient oil collection due to their excellent oil-water separation. However, the most of currently reported oil adsorption materials are limited resources or require complicated preparation steps, which causes high energy consumption and not be practical for large-scale application. Herein, we report a facile strategy to modify the wettability of Enteromorpha from hydrophilic to hydrophobic, which not only greatly reduces energy consumption but also shows the outstanding capacity for oil-water separation with the maximum adsorption capacities is 11.4 g/g and the contact angle reaches 137°. The successful modification of the Enteromorpha is achieved by grafting n-octyltriethoxysilane on the surface of the pristine Enteromorpha. The hydrophobic and superoleophilic Enteromorpha guarantee adequate voids in the fibrous bundles only for oil adsorption and the oil floating on the seawater is removed by the formation of hydrogen bonding between oil and modified Enteromorpha. By optimizing test, the optimal adsorption conditions are adsorption time of 60 min, oil-water ratio of 1:10 and pH of 7. Our reported hydrophobic organosilane modified Enteromorpha will open a new avenue to control marine oil pollution and suppress the damage of Enteromorpha to the marine ecology system.

A Simple Process to Prepare High‐Efficiency Durable Oil–Water Filter

AbstractA simple process is designed to conveniently prepare a high‐efficiency oil–water filter to satisfy the need to separate oil from large amounts of oily wastewater. In this strategy, a porous sand core (SC) is selected as the substrate, and a hydrophilic sodium alginate gel layer is introduced to uniformly cover the outer and inner surfaces of the SC by briefly and successively soaking the SC into sodium alginate solution and CaCl2 solutions. Significant underwater ultra‐oleophobicity is achieved by combining a hydrophilic gel coating with a rough surface microstructure. This modified filter exhibits excellent oil–water separation ability. The SCs with various pore sizes exhibit a separation efficiency of nearly 100% when filtering various oil–water mixtures and oil‐in‐water emulsions, and a water flux of approximately 200–5000 L m–2 h–1 depending on the pore size of the SC and the operating pressure. Moreover, the filter reveals excellent chemical stability, excellent mechanical strength, ease of cleaning, and strong durability, thereby making it a potential candidate for large‐scale applications in wastewater treatment.

Robust super hydrophobic cotton fabrics functionalized with Ag and PDMS for effective antibacterial activity and efficient oil–water separation

The development of multifunctional super hydrophobic cotton materials for oil–water separation and biological activities has attracted significant research interest. In the present study, a robust, fluorine-free, durable and recyclable modified cotton fabric was created by graft polymerization and coating techniques. The surface was grafted with poly(glycidyl methacrylate) (PGMA), subsequently aminated with diethylenetriamine (DETA), and then immobilized with Ag to obtain CF@GMA@DETA(Ag). Moreover, Polydimethylsiloxane (PDMS) was coated on CF@GMA@DETA(Ag) for super hydrophobicity to obtain the modified cotton fabrics (CF@GMA@DETA(Ag)/PDMS). The water contact angle (WCA) reached 155° ± 1.5°. The modified cotton material had excellent oil–water separation efficiency. Meanwhile, the modified cotton material also has outstanding recyclability and stability. With Ag modification, the modified cotton material also showed impressive antibacterial properties. Furthermore, oil–water separation efficiency was generally higher than 97% in artificial seawater, which offers a possible application to separate oil and water in seawater. These properties render the as-prepared cotton fabric a promising material with potential applications.

Eco-friendly and superhydrophobic nano-starch based coatings for self-cleaning application and oil-water separation

High-performance nano-based superhydrophobic coatings have attracted tremendous attention in a wide range of sectors. As a biodegradable and low-cost natural polymer, starch nanoparticles (SNPs) exhibit significant potential for use in many advanced materials. However, nano-starch based superhydrophobic coatings have not yet been reported. Herein, SNPs/polydimethylsiloxane composites were applied to fabricate these coatings using an environmentally friendly approach. The coating exhibited superhydrophobic (water contact angle >152.0° and sliding angle <9.0°) and self-cleaning properties owing to the hierarchical micro and nanostructures formed by coralloid SNP aggregates combined with the low surface energy of the PDMS covering. Meanwhile, the strong adhesion of PDMS and chemical bonding of SNPs with PDMS endowed the coatings with mechanical and chemical robustness. The excellent oil-water separation abilities of the coating were also comprehensively confirmed. This coating shows the potential application in the development of eco-friendly self-cleaning materials and oily wastewater treatment.

Robust preparation of flexibly super-hydrophobic carbon fiber membrane by electrospinning for efficient oil-water separation in harsh environments

Conventional polymer filtration membranes suffer from low efficiency, easy fouling and serious degradation in harsh environments, due to its low chemical and separation stability. Herein, a flexible super-hydrophobic carbon nanofiber membrane (CFMHF) was prepared using electrospinning and subsequently fluorinated treatment. The zinc acetate (ZnAc) was introduced to form pores in carbon fibers during heat treatment, and the pore-forming mechanism was well discussed. As a result, the flexibility and specific surface area of the carbon fibers were increased. The CFMHFs exhibited excellent super-hydrophobicity (water contact angle, WCA = 155.9°), high oil flux (3590 L m−2 h−1) and excellent oil-water separation performance. Driven by gravity alone, the separation efficiencies of the CFMHFs for non-emulsified oil-water and emulsified water-in-oil mixtures were both more than 98%. More importantly, the as-prepared CFMHFs showed good stability in harsh conditions, including high or low temperature, strong acid and alkali solutions, organic solvents and salt solutions. This strategy has directive significance for designing high performance oil-water separation membranes.