Continuous Oil Water Separation Research Articles

Manta ray gill inspired radially distributed nanofibrous membrane for efficient and continuous oil–water separation

Manta ray gill inspired super-hydrophilic membrane for efficient and continuous oil–water separation.

Fabrication of superhydrophobic nano-aluminum films on stainless steel meshes by electrophoretic deposition for oil-water separation

Stainless steel meshes with superhydrophobic surfaces were successfully fabricated via a facile electrophoretic deposition process. The surface morphology and chemical compositions were characterized by a field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscope (EDS), X-ray diffraction (XRD) and fourier-transform infrared spectrophotometer (FTIR). After stearic acid modification, the obtained nano-aluminum films on stainless steel meshes showed an excellent superhydrophobic properties with a water contact angle of 160° ± 1.2° and a water sliding angle of less than 5°. In addition, on the basis of the superhydrophobic meshes, a simple, continuous oil-water separation apparatus was designed, and the oil-water separation efficiency was up to 95.8% ± 0.9%. Meanwhile, after 20 oil-water separation cycles, the separation efficiency without significant reduction suggested the stable performance of superhydrophobic stainless steel meshes on the oil-water separation. Moreover, the flow rate of oil-water mixture and effective separation length were investigated to determine their effects on the oil-water separation efficiency, respectively. Our work provides a cost-efficient method to prepare stable superhydrophobic nano-Al films on stainless steel meshes, and it has promising practical applications on oil-water separation.

Recyclable and biodegradable superhydrophobic and superoleophilic chitosan sponge for the effective removal of oily pollutants from water

Superhydrophobic and superoleophilic chitosan sponge (MCTCS) was successfully prepared via a facile freeze-drying method with the assistance of TPP/citral crosslinking and octadecanethiol modification. The three dimensional porous structure endowed the MCTCS sponges with large pore volume and good compressive property. Moreover, the MCTCS sponge could effectively absorb oil with an absorptive capacity up to 60 times of its own weight. More importantly, the MCTCS sponge could selectively absorb the emulsified oils in water effectively, and achieve continuous oil–water separation with the assistance of peristaltic pump. The oil and water separation efficiency was up to 99%. Furthermore, the MCTCS sponge still maintained a highly absorptive capacity after being reused for many cycles and possessed ideal biodegradability. It was believed that the superhydrophobic/superoleophilic chitosan sponge would be a promising absorbent material for the removal of oil from water in environmental remediation.

Fabrication of durable super-repellent surfaces on cotton fabric with liquids of varying surface tension: Low surface energy and high roughness

In this study, we have developed super-repellent surface on cotton fabric via a facile and eco-friendly strategy using zirconia particles with water-soluble siloxane emulsion. The coated fabric using zirconia-siloxane (ZS) coating showed super-repellency of liquids with surface tension >47.7mN/m, like water, mixtures of isopropyl alcohol with deionized water (2% and 5%, v/v), and ethylene glycol with contact angle of 158°, 155°, 153° and 152°, respectively. Furthermore, the coated fabric displays low sliding angle, <10°, with these liquids. The super-repellency of the coated fabric is attributed due to its lower surface energy (<1.0mJm−2). The produced coating exhibited excellent durability and retained its super-repelling properties under harsh environment conditions like acidic, alkaline, salty, ultraviolet irradiation, mechanical abrasion and repeated tear test with an adhesive tape. In addition, in a mixture of water and oil (having surface tension <30mN/m), the developed coated fabric exhibited dual nature viz., superhydrophobicity and superoleophilicity, maintaining the super-repellency with water even they are wetted with oily liquids. The materials with ability to repel water in the presence of oily pollutants are very useful in application related to sea water. Thus as-prepared coated fabric, with dual functionality, is a promising material for many applications including anti-wetting, self-cleaning, support for aquatic floating devices and as a filtration material for rapid and continuous oil-water separation.

Facile preparation of superhydrophobic metal foam for durable and high efficient continuous oil-water separation

Foam-based material with unique wettability is one of the promising materials for developing oil-spill cleanup, benefiting from its intrinsic interconnected three-dimensional skeleton, oil permeation and water repellency. However, obtaining a foam-based material capable of in situ separating oil spills, especially with superhydrophobic durability and simple recycling mode, remains challenging. Herein, we reported a one-step spraying approach to fabricate fluorinated ethylene propylene (FEP)/polyvinylidene fluoride (PVDF)/ultrafine polyurethane (UPU)/hydrophobic nanosilica (HSiO2)-decorated nickel foam coating with a static water contact angle (WCA) of 157±1.5° and a static oil contact angle (OCA) of 0°. Owing to the foldability of the coated nickel foam, we established a continuous in-situ collection apparatus by external pumping on 3D nickel foam box. UPU addition endowed the resultant 3D nickel foam with excellent interfacial adhesion. After 7days of continuous oil-water experiment that simulated cleanup oil-spill, the static WCA of the 3D nickel foam with 10wt% UPU was still above 130°. Notablely, after heat treatment at 240°C, the fabricated 3D nickel foam coating could be refreshed from the damaged surface to superhydrophobic.

Underwater superoleophobic mesh based on BiVO4 nanoparticles with sunlight-driven self-cleaning property for oil/water separation

There is an increasingly significant issue on oil/water separation in modern chemical industry and environmental protection on account of the frequent oil spills and large amounts of oily industrial wastewater. Herein, we demonstrate an underwater superoleophobic BiVO4 coated mesh with sunlight-driven self-cleaning property for oil/water separation. The as-prepared coating has micro/nano structures and shows underwater superoleophobicity for various oils and organic solvents. It also exhibits excellent durability against abrasion, cavitation erosion and ultra-low temperature. Such coating can be used in separation of oil/water mixtures and further applied in a continuous oil-water separation system. More importantly, the BiVO4 coating can decompose organic contaminants in water and those absorbed on the surface under simulated solar irradiation, thus make both water and the coating clean. All these features make the BiVO4 coated mesh an ideal candidate for potential application in water contamination treatment.

A magnetic superhydrophilic/oleophobic sponge for continuous oil-water separation

In this work, a magnetic, superhydrophilic/oleophobic (MSHO) sponge was prepared by a facile one-step dipping method. It not only showed excellent capacity for oil-water separation but also could selectively absorb and continuously remove water from bulk oil, which is probably owing to the combination of its high porosity, superhydrophilic and oleophobic nature, as well as its capillary action. The magnetic property of the MSHO sponge made it easily being removed with a magnet. It was believed that the MSHO sponge had potential application prospect in industrial oil products purification and oil spill cleanup.

Paper‐Based Surfaces with Extreme Wettabilities for Novel, Open‐Channel Microfluidic Devices

In this work, a facile methodology is discussed, involving fluoro‐silanization followed by oxygen plasma etching, for the fabrication of surfaces with extreme wettabilities, i.e., surfaces that display all four possible combinations of wettabilities with water and different oils: hydrophobic–oleophilic, hydrophilic–oleophobic, omniphobic, and omniphilic. Open‐channel, paper‐based microfluidic devices fabricated using these surfaces with extreme wettabilities allow for the localization, manipulation, and transport of virtually all high‐ and low‐surface tension liquids. This in turn expands the utility of paper‐based microfluidic devices to a range of applications never before considered. These include, as demonstrated here, continuous oil–water separation, liquid–liquid extraction, open‐channel microfluidic emulsification, microparticle fabrication, and precise measurement of mixtures' composition. Finally, the biocompatibility of the developed microfluidic devices and their utility for cell patterning are demonstrated.

One-pot synthesis of robust superhydrophobic, functionalized graphene/polyurethane sponge for effective continuous oil–water separation

Graphene/polyurethane (PU) sponges with superhydrophobicity have been one-pot synthesized by solvothermal technique. The surfaces of interconnected pores within the PU sponges were modified with (3-Mercaptopropyl)trimethoxysilane and graphite oxide via a solvothermal treatment, allowing crater-like functionalized graphene layers to be formed as a substructure and attached firmly to the polyurethane skeleton. By forming such characteristic nano–micro substructures on the backbones of PU sponges, the graphene/PU sponges possessed a superhydrophobicity with WCA exceeding 160°. When applied in conjunction with a simple vacuum system, this sponge could act as a selective filter to continuously and effectively separate the oil from water. Because the functionalized PU sponge retained original PU structural integrity, the material was chemically robust and capable of separating oil up to 53,000 times of its own mass with high oil–water separation efficiency (>99.5%). The functionalized PU sponge and integrated oil–water separation system proposed in this study may provide a novel and practical methodology for industrious scale oil–water separation.

Engineering Reduced Graphene Oxide Aerogel Produced by Effective γ-ray Radiation-Induced Self-Assembly and Its Application for Continuous Oil–Water Separation

Reduced graphene oxide aerogel (RGO aerogel) is successfully synthesized via simultaneous reduction and self-assembly of graphene oxide (GO) sheets under γ-ray irradiation. As the resulting RGO aerogel possesses an interconnected macroporous structure with strong hydrophobicity and oleophilicity, it has great potential in oil–water separation. Adsorption–distillation and adsorption–combustion are both utilized to treat oil floating on water or oil sinking below the water surface. More importantly, a simple device has been developed to adsorb continuously and collect floating oil, and it has shown great promise for practical application.

Continuous Oil–Water Separation Using Polydimethylsiloxane-Functionalized Melamine Sponge

The development of absorbent materials with high selectivity for oils and organic solvents is of great ecological importance for removing pollutants from contaminated water sources. We have developed a facile solution-immersion process for creating polydimethylsiloxane (PDMS)-functionalized sponges for oil–water separation. Sponge materials with densities ranging from 8 to 26 mg/cm3 were investigated as candidate skeletons. After functionalization, the lowest-density melamine sponge exhibits superior superhydrophobic and superoleophilic properties, absorption capacity, oil–water selectivity, and absorption recyclability. Via suction through such a functionalized sponge, we have experimentally demonstrated that various kinds of oils can be continuously separated from immiscible liquid mixtures without any water uptake. The widely available raw materials (melamine sponge and PDMS solution) and simple synthesis steps yield a cost-effective and scalable process for fabrication of absorbent materials that can ...

PH-Induced switches of the oil- and water-selectivity of crosslinked polymeric membranes for gravity-driven oil–water separation

A membrane with pH-induced switchable oil- and water-selectivity for gravity-driven continuous oil–water separation.

Magnetically driven functionally integrated device for continuous and efficient collection of oil droplets from water

A novel magnetically driven functionally integrated device for continuous oil–water separation with high collecting efficiency was reported.

One-step fabrication of a nickel foam-based superhydrophobic and superoleophilic box for continuous oil–water separation

Developing novel oil–water separation material, especially with uncomplicated fabrication and easily continuous separation procedure, is of great significance for environmental protection, but it is still a worldwide challenge. In this study, we present a simple one-step copolymerization method for fabrication organics coated three-dimensional material based on commercial nickel foam with dopamine and octadecylamine. The as-prepared nickel foam shows high superhydrophobicity with water contact angle (CA) of 154° ± 2°, water shedding angle of 4° ± 1° and superoleophilicity with oil CA of almost 0°. The as-prepared foam can fast and selectively remove oil from water due to its special wettability and porous structure. Besides, the foam can be manipulated to realize oil–water separation with a magnet bar due to its intrinsic magnetism. More interestingly, because of it being lightweight, and softness and toughness performance, the as-prepared foam can continuously remove and collect oil from water surface by folding it to a closed hollow box, which integrates the functions of oil containment boom, oil-absorption material and oil skimmer into one device. We believe that this research can provide a nice idea to design new material and device for practical oil–water separation.

Self-roughened superhydrophobic coatings for continuous oil–water separation

Hydrophobic polydimethylsiloxane based coatings were self-roughened on poly(ethylene terephthalate) textiles via a nonsolvent-induced phase separation method to fabricate superhydrophobic and superoleophilic surfaces. The method is simple and large-area scalable and the obtained textiles could be used as excellent filters for continuous oil–water separation.

Continuous oil–water separation with surface modified sponge for cleanup of oil spills

A continuous in situ oil–water separation technique for cleanup of oil spills has been designed using surface modified polyurethane (PU) sponges as sorbents. By connecting PU sponges to a vacuum pump, they can continuously separate various kinds of oil and organic pollutant, including engine oil, diesel oil, peanut oil, liquid paraffin and hexane, from the surface of water with negligible water take-up. The sorbents used in the technique were prepared by dip-coating commercial PU sponges with TiO2 sol and n-octadecylthiol successively. After surface modification, the sponges change from hydrophilic to superhydrophobic and superoleophilic surface with the water contact angle measured to be 152°. The as-prepared sponges absorb a broad variety of oils and organic solvents with high oil absorption capacity (80–110 g g−1) and negligible water take-up at both static and dynamic conditions. The success of the continuous in situ oil–water separation technique is based on the excellent oil–water selectivity and oil adsorption capacity of the modified sponges.

Emulsion layer growth in continuous oil–water separation

The relationship between emulsion coalescence and emulsion layer growth was investigated using batch, continuous, and decay experiments on model emulsion systems. Model oil-in-water emulsions were prepared at 45 °C from water containing NEO-10 surfactant and an organic phase consisting of 50 vol% toluene and 50 vol% n-heptane. Model water-in-oil emulsions were prepared at 60 °C from water containing AOT and Tween 80 and an organic phase (1.5 g/L asphaltenes in a solution of 50% toluene and 50% n-heptane). In a batch experiment, the emulsion was allowed to coalesce and the height of the free water and oil layers were measured over time. The bulk coalescence rate was determined from the change in height over time. Continuous experiments were performed where the emulsion was continuously fed to a separator until a steady state condition was reached. Decay experiments involved shutting of the feed and measuring the decrease in emulsion layer height over time. It was demonstrated that the bulk coalescence rate is proportional to the volume of the emulsion layer consistent with droplet–droplet coalescence. Using a model based on this assumption, the steady state height in continuous experiments was predicted from the initial coalescence rate determined from a decay experiment. Interestingly, for oil-in-water emulsions, the coalescence rate was found to decrease exponentially over time possibly due to surfactant accumulation in thinning continuous phase films. Hence, compaction of the emulsion layer can slow that rate of coalescence. For water-in-oil emulsions, the coalescence rate was constant for approximately 30 min and then decreased to zero, suggesting that the aging of asphaltene films may play a significant role in emulsion layer growth. The effect of flow rate of the emulsified feed, separator geometry, and wall effects were also studied.