Application In Oil-water Separation Research Articles

Fabrication of pre-wetting induced superamphiphobic meshes for on-demand oil-water separation of light or heavy oil-water mixtures

In this study, a facile approach was proposed to fabricate superamphiphobic meshes for on-demand separating light or heavy oil and water mixtures after pre-wetting process. The micro-nano hierarchical structures on superamphiphobic stainless steel mesh were fabricated via vacuum thermal evaporation and chemical deposition. Low surface energy was acquired by modification with perfluorooctanoic acid. The effect of reaction time on wettability was investigated to obtain the optimal parameters of fabricating samples exhibiting superhydrophobicity and superoleophobicity simultaneously. The wettability of superamphiphobic meshes was controlled by the liquids of pre-wetting process. The superamphiphobic surfaces pre-treated with ethanol and water were used to separate the mixtures of light oil and water, while the meshes sequentially pre-soaked with ethanol and oil to separate the mixtures of heavy oil and water. The separation efficiency of up to 98 % was found even after multiple cycles. The fabricated superamphiphobic surfaces can avoid contamination and achieve on-demand oil-water separation without any external forces, which will have promising potential for application in oil-water separation.

Polysulfone-iron acetate/polyamide nanocomposite membrane for oil-water separation

Polysulfone (PSF) membranes are widely used for water filtration, however, their hydrophobic nature limits their application in oil-water separation. Herein, we report on the preparation of hydrophilic, high-flux and mechanically-stable PSF-based nanofiber membrane. The membrane was fabricated via electrospinning of a PSF solution containing iron acetate powder followed by deposition of a polyamide (PA) layer using interfacial polymerization on both sides of the membrane. This treatment resulted in switching membrane from being hydrophobic (contact angle = 100 ± 7°) to be highly hydrophilic (contact angle = 37 ± 5°) and the membrane porosity reached up to 83 ± 7 % after the deposition of the PA layer. Results from field emission electron microscopy with energy dispersive spectroscopy (FESEM-EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) showed the unique nanofiber characteristics with uniform iron distributions. The new membranes have also improved mechanical properties as indicated by Young's modulus and mechanical strength. In addition, the membranes efficiently separated water from oil-water mixtures and the water flux of the modified membrane was three times higher than the unmodified PSF membrane in this study and also higher than previously reported membranes.

Lower-temperature preparation of SiC ceramic membrane using zeolite residue as sintering aid for oil-in-water separation

Due to their excellent attributes of high water permeance, good stability and antifouling properties, silicon carbide (SiC) membranes have achieved widespread application in industrial wastewater treatment facilities. However, the high sintering temperature (usually beyond 2000 °C) during the preparation of porous silicon carbide is a challenge for the transfer of the technology from the laboratory to industry. An efficient sintering additive method was proposed herein to address this issue. Inexpensive residues (containing oxides of sodium, aluminum and silicon) from an NaA zeolite production line were used as the sintering additives to make the SiC particles more tightly connected due to the formation of new phases. Thus, a SiC network could be formed during an in-situ reaction at lower sintering temperature (e.g., 1000 °C) in air without inert gas protection. The as-prepared SiC membranes exhibited a high pure water permeance of 3700 L m-2 h-1 bar-1 and open porosity of 46%. The mechanical strength of the membrane reached 45 MPa. After alkali corrosion or thermal shock resistance tests, the bending strength was maintained at least 38 MPa. The membrane with a mean pore size of 0.4 μm exhibited a high rejection rate to oil droplets (˃ 90%) in various oil-in-water emulsions with a high water permeance. Membrane cleaning with an ultrasonic treatment resulted in good stability in long-term filtration tests. The utilization of zeolite residues successfully reduced the operational cost of heating during ceramic membrane fabrication with recycled solid wastes. Hence, the proposed preparation method for SiC membranes has good sustainability and is scalable for oil-water separation applications.

Self-cleaning and Oil/Water Separation of 3D Network Super-hydrophobic Bead-like Fluorinated Silica Pellets/Poly(aryl ether ketone) Composite Membrane Fabricated via a Facile One-step Electrospinning

Novel super-hydrophobic fluorinated silica pellets/poly(aryl ether ketone) composite membranes with controllable structure have been prepared through incorporating poly(aryl ether ketone)s with (3-trifluoromethyl)-phenyl side groups and fluorinated silica pellets(F-SiO2) by a facile one-step electrospinning. Under the condition of adding 50%(mass fraction) F-SiO2 in the composite membrane, the water contact angle(WCA) reached its maximum (157°±4.3°). The controllable micro/nano-structures grown on the electrospun fibers could be regulated by the F-SiO2 loading, which was illustrated by scanning electron microscopy(SEM). Moreover, these super-hydrophobic membranes also demonstrated excellent durability, anti-fouling property and oil-water separation ability after 200 h of water flushing. These promising PAEK composite membranes with controllable structure have the potential values in large-scale application of filtration, oil-water separation and antifouling.

Synthesis of Iron Oxide Nanoparticles and its Application for OilWater Separation

Magnetic nanoparticles have been explored extensively for their applications in day to day life. Among their various uses like magnetic data storage and biomedical applications, they have remained a field of interest for researchers. The well known magnetic nanoparticles are iron oxide nanoparticles. In this work, iron oxide nanoparticles are prepared by self sustained combustion technique. Ferric nitrate (Fe (NO3)3.9H2O) was used as a precursor and ethylene glycol as a fuel. Solution was heated at 120°C. After being preheated to the boiling point of ethylene glycol and its evaporation, the solution self-ignites and the temperature rises rapidly to values as high as 1500°C. Magnetic properties of Fe2O3 are studied using vibrating sample magnetometer (VSM). The magnetic properties are utilized for separation of oil from oil-water mixture.

Magnetically recoverable magnetite-reduced graphene oxide as a demulsifier for surfactant stabilized crude oil-in-water emulsion.

Oily wastewater, especially water-oil emulsion has become serious environmental issue and received global attention. Chemical demulsifiers are widely used to treat oil-water emulsion, but the toxicity, non-recyclable and non-environmental friendly characteristic of chemical demulsifiers had limited their practical application in oil-water separation. Therefore, it is imperative to develop an efficient, simple, eco-friendly and recyclable demulsifiers for breaking up the emulsions from the oily wastewater. In this study, a magnetic demulsifier, magnetite-reduced graphene oxide (M-rGO) nanocomposites were proposed as a recyclable demulsifier to break up the surfactant stabilized crude oil-in-water (O/W) emulsion. M-rGO nanocomposites were prepared via in situ chemical synthesis by using only one type Fe salt and GO solid as precursor at room temperature. The prepared composites were fully characterized by various techniques. The effect of demulsifier dosage and pH of emulsion on demulsification efficiency (ED) has been studied in detailed. The demulsification mechanism was also proposed in this study. Results showed that M-rGO nanocomposites were able to demulsify crude O/W emulsion. The ED reaches 99.48% when 0.050 wt.% of M-rGO nanocomposites were added to crude O/W emulsion (pH = 4). Besides, M-rGO nanocomposites can be recycled up to 7 cycles without showing a significant change in terms of ED. Thus, M-rGO nanocomposite is a promising demulsifier for surfactant stabilized crude O/W emulsion.

Multifunctional TiO2-Based Superoleophobic/Superhydrophilic Coating for Oil-Water Separation and Oil Purification.

Materials that possess distinguishable superwettability toward oil and water have aroused widespread attention for their application in oil-water separation. Among them, a superoleophobic/superhydrophilic material is considered as the ideal candidate because of its antioil-fouling and water-wetting behavior; however, the fabrication is a challenge and there has been insufficient attention given to multipurpose applications in treating intricate mixtures. Herein, for the first time, a multifunctional superoleophobic/superhydrophilic coating integrated with a photocatalysis property was fabricated by the combination of polarity component-enhanced fluorosurfactant and titanium dioxide (TiO2) nanoparticles. The coating applied on stainless steel mesh preserves the ability to separate immiscible oil-water mixtures, whereas the coated cotton preserves the ability to separate both surfactant-stabilized oil-in-water and water-in-oil emulsions. Notably, benefiting from the photocatalysis property of titanium dioxide, the coating also can be used in liquid purification. Contaminated oil can be separated and purified by a separation-purification process, during which the oil-soluble contamination is degraded under ultraviolet (UV) irradiation. The multipurpose coating provides an alternative solution for oil-water remediations, which has prospects in intricate liquid treatment in industrial and domestic applications.

Structural conversion of PLLA/ZnO composites facilitated by interfacial crystallization to potential application in oil-water separation

Focus on the potential application in oil-water separation for porous and biodegradable Poly(L-latic acid) (PLLA) amenable to economically viable water treatment, we designate the controllable pores, fibrillary network and protrusion structure by crystallization induced phase separation in poly(L-latic acid)/Zinc oxid (PLLA/ZnO) materials, ready for their potential application in oil-water separation. It’s worth noting that the interface effect between PLLA and ZnO is strengthened by silane coupling agent KH570. The crystallinity of the PLLA/ZnO@KH570 materials are correspondingly increased from 36.9% to 41.1% as the slightly increasing content of ZnO@KH570 from 1% to 7%, indicating that ZnO@KH570 nanoparticles can act as heterogeneous nucleating agent to promote crystallization of PLLA, which facilitate the conversion of PLLA solution from liquid-liquid phase separation mechanism to solid-liquid phase separation mechanism, resulting in the formation of microstructures. Very interestingly, the porosity of PLLA/ZnO@KH570 composite is highest up to 94.1% compared to its value of 87.8% for pure PLLA. Due to the multiple structures, the water contact angle of composite is significantly improved to 146°, allowing the oil/water mixture solution to be effectively separated. In brief, we have successfully manufactured hydrophobic PLLA/ZnO@KH570 composite with the multi-scale microstructure which may be potentially applied in oil-water separation.

Sprayable superhydrophobic coating with high processibility and rapid damage-healing nature

Superhydrophobic coatings simultaneously exhibiting high substrate binding, mechanical robustness and damage-healing properties are of great significance for practical applications. In this work, an effective silicone-based paint was developed to prepare superhydrophobic coating for the first time with the abovementioned properties. The paint is formulated with supramolecular silicone polymers and silica nanoparticles, which can be sprayed on solid substrates and assembled into porous films with enhanced water repellency. The abundant hydrogen bonds and coordination bonds in the supramolecular silicone polymers provided additional substrate binding and damage-healing properties. The coating can maintain water-repellency upon a series of tests including tape peeling, sandpaper abrasion and underwater placement. They can repeatedly heal chemical and topographical defects by simple thermal treatment due to the dynamic intermolecular crosslinking and chemical reorganization of the supramolecular polymers. Taking advantages of their high processibilty, multifaceted robustness and inherent healing ability, the developed superhydrophobic coatings hold great promise for applications in liquid transportation, oil-water separation, anti-icing and drag reduction.

Bio-based polybenzoxazine composites for oil-water separation, sound absorption and corrosion resistance applications

In the present work, an attempt has been made to develop bio-based composites using cardanol and eugenol based benzoxazine matrices with bio-silica as well as natural fibrous materials (coir felt, kapok fabric, jute felt and rice husk) as reinforcements. The bio-composites developed were studied for different applications viz., dielectric, water repellent, oil-water separation, sound-absorption including corrosion resistance use. Among the bio-silica reinforced benzoxazine composites, 7 wt% bio-silica reinforced cardanol composites possesses the highest value of water contact angle (147°) and the lowest value of dielectric constant (2.0) than those of other bio-silica reinforced composites. Further, the cotton fabric was coated with cardanol and eugenol based polybenzoxazines separately, whose values of water contact angles are found to be 159° and 157° with oil-water separation efficiency as 96% and 95% respectively. Furthermore, the cardanol based benzoxazine was separately reinforced with jute felt, coir felt, kapok fabric and rice-husk. The corresponding sound absorption efficiency was found to increase in the following order, Neat polybenzoxazine < rice husk < coir felt < kapok fabric < jute felt. Data resulted from corrosion studies, it was noticed that the mild steel specimen coated with bio-based benzoxazine matrices and bio-silica reinforced benzoxazine composites coated specimens exhibit an excellent resistance to corrosion. Data resulted from different studies, it is suggested that the cardanol and eugenol based bio-composites can be considered as an effective materials for microelectronics insulation, water repellent, oil-water separation, sound absorption and corrosion resistant applications.

Non-fluorinated superhydrophobic spray coatings for oil-water separation applications: An eco-friendly approach

Inspired by nature, we prepared durable superhydrophobic coating materials (SHC) using Hexamethyldisilazane (HMDS) modified silica (SiO2) nanoparticles with acrylic resin, coupled with γ-Aminopropyltriethoxysilane (γ-APS) without the need of the perfluorinated and isocyanate based compounds. As we have prepared the organic acrylic resin by surfactant based emulsion polymerization method the material exhibited good film formation and inorganic silica functionalized with HMDS also exhibited low surface energy and good superhydrophobic property. The hybrid nanocomposites with and without γ-APS were characterized by FT-IR, TGA, particle size analyzer and SEM. The results shows that γ-APS strongly attaches with trimethylsilyl modified SiO2 and acrylic resin and form strong covalent network with excellent superhydrophobic property. The prepared superhydrophobic material was coated on various substrates like glass, wood, filter paper, cotton, plastic, stone, fabric and aluminium foil by spray coating. The SHC coated glass slides which were treated under various chemical and thermal conditions exhibited water contact angle of >150. Similarly, the samples were tested for mechanical durability, sand paper abrasion test shows the contact angle of >150 and sliding angle <10 which does not change up to 30 abrasion cycles. Further, we showed that prepared SHC can be used for oil/water separation study and the material exhibited excellent mechanical durability up to 50 cycles.

Cellulose-based, highly porous polyurethanes templated within non-aqueous high internal phase emulsions

Cellulose is one of the most abundant resources in nature. Cellulose-based porous monoliths have been fabricated by direct drying of oil-in-water high internal phase emulsions (HIPEs) stabilized using either cellulose derivatives or surface-modified cellulose. The resulting cellulose-based porous polymers, however, were usually fragile, reflecting the lack of crosslinking. Herein, we report a new strategy to fabricate cellulose-based porous materials (polyurethane polyHIPEs, PU polyHIPEs) templated within non-aqueous HIPEs through the covalent crosslinking between isocyanates and unmodified cellulose. The PU polyHIPEs exhibited interconnected macroporous structures and exhibited tunable wettability from hydrophilicity/oleophilicity to hydrophobicity/oleophilicity. The PU polyHIPEs were able to absorb a wide variety of oils, exhibiting relatively large capacities and high absorption rates. We further showed that the PU polyHIPEs were robust, and they did not fail under compressive stress even at strains of 70%. The robustness, large absorption capacities, rapid absorption, and hydrophobicity/oleophilicity make these cellulose-based PU polyHIPEs suitable for oil absorption and/or oil–water separation applications.

Superhydrophobic and superoleophilic polyethylene aerogel coated natural rubber latex foam for oil-water separation application

The oil-water separation has made an attention due to over-increased production of oily water from the industrial process and everyday routine of humans. The current work reports on preparation and characterization of High-Density Polyethylene (HDPE) aerogel coated Natural Rubber Latex foam (NRLF) with superhydrophobic and superoleophilic character, good sorption capacity for oil-water separation application and were investigated. The HDPE aerogel and the coated NRLF material was prepared by a cooling process from a solution of HDPE in xylene solvent (HDPE sole, which resulted into thermally induced phase separation of the Polyethylene molecular network). The HDPE aerogel coated NRLF displayed a porous surface morphology with particle-like structural features. The HDPE aerogel coated NRLF showed superhydrophobicity with static water contact angle >150°. The effect and recyclability of the HDPE aerogel coated NRLF for oil-water separation was investigated using different model oil solvents to explore their repeatable application in oil spill clean-up process. Modified NRLF shows an excellent mechanical property (compressibility). The average modulus and average stiffness of the modified NRLF increased with the increase of the concentration of HDPE sol. The modified superhydrophobic sponge has good durability under acid and base conditions.

Preparation of superhydrophobic and flexible polysiloxane aerogel

Silica aerogels, which consist of nano-particles and abundant nano-pores, have many outstanding properties. However, poor mechanical performances dramatically limit the practical applications of aerogel. Herein, we reported the preparation of novel superhydrophobic and flexible silica aerogel with several kinds of polysiloxane. The aerogel was formed with the polysiloxane and multimethoxy-POSS, the POSS was efficiently synthesized by thio-ene reaction and used as a crosslinking agent to strengthen the structure. The obtained data revealed all aerogels had the mesoporous structure (19–27 nm), high specific surface area (476.3–632.9 m2 g−1) and fine heat resistance. The different ratio of side groups on polysiloxane and the content of POSS led to the different mechanical properties, the ultimate compression strain was up to 50%. Moreover, the further oil-water separation application has also been demonstrated.

Carbon Microtube Aerogel Derived from Kapok Fiber: An Efficient and Recyclable Sorbent for Oils and Organic Solvents

Carbon microtube aerogel (CMA) with hydrophobicity, strong adsorption capacity, and superb recyclability was obtained by a feasible approach with economical raw material, such as kapok fiber. The CMA possesses a great adsorption capacity of 78-348 times of its weight. Attributed to their outstanding thermal stability and excellent mechanical properties, the CMA can be used for many cycles of distillation, squeezing and combustion without degration, which suggests a extremely potential pratical application in oil-water separation. In addition, the adsorption capacity still retained 98% by distillation, 97% by squeezing, and 90% by combustion after 10 cycles. Therefore, the obtained CMA has a broad prospect as an economical, efficient and environment-friendly adsorbent.

Superhydrophobic Treatment of Polyurethane Sponge and Its Application in Oil-water Separation

The superhydrophobicity of the polyurethane sponge was realized by attaching the complex of copper and mercaptan on the outer surface of the polyurethane sponge. As a special case, the complex of 1-dodecanthiol and copper chloride was intensively investigated in this study, with emphasis on the influences of concentration, temperature and residence time on the reaction. SEM and EDS were used to analyze the surface structure and elemental composition of the sponge. The superhydrophobicity of the sponge are contributed by the rough treatment on sponge surface. It is found that a large number of long carbon chains appear on the surface reduces the surface energy. The wettability of the surface was determined by a contact angle meter. The material demonstrates great oil-water separation performance and high repeatability in superhydrophobicity during the the separation process of oil and water before first 39 times.

Blends of Chalcone Benzoxazine and Bio-benzoxazines Coated Cotton Fabrics for Oil–Water Separation and Bio-silica Reinforced Nanocomposites for Low-k Applications

In the present work, chalcone benzoxazine (Chal-Bz) was co-polymerized with two bio-based benzoxazines namely cardanol (CrAb) and eugenol (EuAb) benzoxazine and coated over cotton fabric. The Chal-Bz/CrAb and Chal-Bz/EuAb blends coated cotton fabrics show water contact angle values of 163° and 156° respectively and their oil–water separation efficiency were observed found to be 97 and 96% respectively. In addition, the glycidoxypropyltrimethoxysilane (GPTMS) functionalized bio-silica in varying weight percentages (1, 3, 5, 7 and 10 wt%) was also reinforced with two co-polymerized blended matrices to obtain respective composites. The developed composites were studied for their dielectric, thermal and morphological behaviours. The values of dielectric constant of 10 wt% bio-silica reinforced Chal-Bz/CrAb and Chal-Bz/EuAb composites were found to be 2.1 and 2.3, respectively. Similarly the values of contact angle of 10 wt% bio-silica reinforced chal-Bz/CrAb and Chal-Bz/EuAb composites were 137° and 116°, respectively. Data obtained from different studies suggest that these bio-silica reinforced benzoxazine composites can be used in the form of coatings, adhesives, sealants and encapsulants for high performance micro-electronics insulation applications under adverse environmental conditions. Thermal assisted polymerization of chalcone based benzoxazine (Chal-Bz) with bio based benzoxazines cardanol-aniline based benzoxazine (CrAb) and eugenol-aniline based benzoxazine (EuAb)) for low k and oil–water separation application.

Silk fibres exhibiting biodegradability & superhydrophobicity for recovery of petroleum oils from oily wastewater

Present study reports superhydrophobic-oleophilic, environment-friendly, & biodegradable silk material derived from Bombyx mori silkworm, for practical oil-water separation and oil recovery applications. In this study, raw silk fibers were degummed using water and Na2CO3 (at 100 °C), for removal of outer gummy sericin protein layer, which was confirmed using FTIR & FE-SEM analysis. The water & Na2CO3 degummed silk fibers showed superhydrophobicity with water contact angles (WCA) of 153° & 158°, respectively, demonstrating Wenzel & Cassi-Baxter states. Degummed silk fibers showed superoleophilicity (OCA∼0°) towards petroleum oils like Petrol, Diesel, & Engine oil. The water & Na2CO3 degummed silk fibers showed oil-water separation efficiencies of 95 % & 87.5 %, respectively. Both degummed silk fibers showed more than 50 % efficiency till 10 separation cycles. Further, raw & degummed silk fibers showed an environmental biocompatibility, by their biodegradation under in-house developed biotic de-compost culture consisting of biodegrading micro-organisms. Their analysis showed that biotic de-compost culture rendered biodegradation weight loss of 11 % and 18 %, respectively, in 35 days. Successive results showed that, degummed silk fibers can be effectively utilized for practical oil-water separation, and further, they can be environmentally biodegraded, thereby mitigating their waste generation and disposal problem.

PH-sensitive organic diimide materials-based superhydrophobic surface for oil-water separation applications

pH-responsive superhydrophobic surfaces (SHSs) have recently represented reliable ability in oil-water separation applications. In this work, for the first time we could develop a switchable SHS based on (E)-4-(anthracen-9-yldiazenyl) benzoic acid (4-ABA) pH-responsive organic molecules and stearic acid (SA) using self-assembly method for oil-water separation applications. Molecular structure of 4-ABA obtains the smart pH sensitive SHS and makes it able to use in oil-water separation process. TiO2 decorated 4-ABA and SA composite (TiO2@4-ABA/SA)-based SHS could tune the surface charge in different pH (2.0–7.0) and subsequently could influence on wettability and contact angle (CA) of surface which makes the surface suitable to represent oil-water separation properties. Density functional theory (DFT) mechanic quantum calculation showed stable absorption of the 4-ABA molecules on TiO2 nanoparticles (∼ >1.3 eV) that rely on the reusability (>20 cycles) of the surface during oil-water separation. Morphology of switchable SHSs were considered by scanning electron microscopy (SEM) and wettability of the surface has been evaluated by CA. The UV–vis spectroscopy showed packing density (Γ = ∼4.35 × 10−7 mol.cm−2) of the 4-ABA in TiO2@4-ABA/SA approach which caused to high rate of switching in wettability (∼5 s per cycle). Transition between superhydrophobic (CA = ∼152.39°) and hydrophilic (CA = ∼26.11°) states is the main advantage of this surface obtained from the different charges of the surface in various pH. Therefore, the 4-ABA molecules-based pH-responsive SHS with ability in adjusting the surface wettability can be applied for oil-water separation applications. The mentioned versatile advantages open a new horizoffn for environmentally friendly applications of this approach which cannot achieved by conventional methods and materials.

Luminescent and hydrophobic textile coatings with recyclability and self-healing capability against both chemical and physical damage

Luminescent and hydrophobic textile coatings with recyclability and self-healing capability against both chemical and physical damage were prepared, which present multi-functions and long service life cycles. The applications in self-cleaning, oil-water separation, and anti-counterfeit technology were successfully demonstrated. The coatings can be easily created onto different fabrics including cotton cloth, filter paper, and chemical fabric. A rare earth organic complex of SmTTAPhen(NO3)3 (STPN), silane modified epoxy oligomer, and bis(4-maleimidophenyl)methane (BMI) provide luminescence, hydrophobicity, as well as recyclability and self-healing capability, respectively, to the coatings. More specifically, high transparency but high luminescence were achieved due to the good dispersion of STPN in coating matrix, resulting from the hydron bonding between nitrate groups from STPN and hydroxyl groups from epoxy oligomer. Silane modification facilitated the accumulation of Si–O bonds on the free-surface of the coating, which offers hydrophobic features. The introduction of reversible Diels-Alder reactions provided the self-healing capability and recyclability. Upon heating using an electronic iron, the hydrophobicity can be recovered from physical or chemical damage to the coatings. Besides, the coatings on abandoned fabrics can be recycled and reused to a new bare fabric. We believe that the concept and coating materials are useful to further expand the areas of smart and multi-functional coatings with long service life.