Selective Oil Absorption Research Articles

Robust super-hydrophobic/super-oleophilic sandwich-like UIO-66-F4@rGO composites for efficient and multitasking oil/water separation applications

Super-wetting MOFs@graphene hybrid has shown promising application for oil/water separation, due to high porosity, low density, and controllable wettability, however, achieving excellent stability and recyclability are found to be still challenging. In this study, sandwich-like UIO-66-F4@rGO hybrid was synthesized by immobilization of UIO-66-F4 nanoparticles on rGO matrix, which featured the unique micro/nano hierarchy with hydrophobic characteristics. In order to realize the oil/water separation, as-prepared sandwich-like UIO-66-F4@rGO hybrid was applied as a potential candidate for constructing robust super-hydrophobic/super-oleophilic interfaces by using filter paper (FP) and melamine sponge (MS) as substrates. Typically, the surface modification of substrates can be easily achieved by simple dip-coating method, and interfacial adhesion between substrates and UIO-66-F4@rGO was enhanced by cross-linking of hydroxyl-fluoropolysiloxane (FPSO). Consequently, the super-hydrophobic/oleophilic UIO-66-F4@rGO/FP exhibited high contact angle of 169.3 ± 0.6° and was capable of separating various water-in-oil emulsions effectively. The flux and separation efficiency were 990.45 ± 36.28 Lm−2 h−1 and 99.73 ± 0.19 % driven by gravity, respectively. The super-hydrophobic/super-oleophilic UIO-66-F4@rGO/MS possessed selective oil absorption with absorption capacity of 26∼61 g/g depending on the viscosity of oils and continuous cleaning of oil spill. Furthermore, the UIO-66-F4@rGO composite could tolerate high/low temperature, corrosive solutions, and physical damage, displaying robust and stable super-hydrophobic/super-oleophilic interfaces for treating oily wastewater in harsh environments.

Fabrication of compressible polyolefin monoliths and their applications

Abstract In this study, we contribute the facile fabrication of tough polyolefin monoliths from their polymer solutions using a phase separation method. Compressive stress–strain tests demonstrate that the monoliths have excellent mechanical properties. The monoliths show macroporous structures where the pore sizes can be tuned from sub-1 to 16 µm by adjusting the fabrication conditions. The monoliths exhibit high hydrophobicity/ oleophilicity and good resistance toward different chemicals. Based on the above properties, we applied the monoliths to the selective absorption of oil from an oil/water mixture. By simply squeezing the monoliths, the absorbed oil can be recovered. The monoliths are useful for more than 10 cycles of absorption and recovery, showing a good stability for industrial-scale oil spill treatment.

A Scalable Chemical Approach for the Synthesis of a Highly Tolerant and Efficient Oil Absorbent.

In the past, bio-inspired extreme water repellent property has been strategically embedded on commercially available sponges for developing selective oil absorbents. However, most of the reported materials lack physical and chemical durability, limiting their applicability at practically harsh settings. Herein, a stable dispersion of polymeric nanocomplexes was exploited to achieve a chemically reactive coating on the highly compressible melamine foam. A superhydrophobic melamine foam (SMF) was achieved after post-covalent modification of the reactive coating through 1,4-conjugate addition reaction at ambient conditions. The durability of the embedded extreme water repellent property in the as-modified melamine foam has been elaborately demonstrated through exposing it to severe physical manipulations, chemically harsh aqueous media including pH 1, pH 12, surfactant contaminated water, river water, seawater and prolonged UV irradiation. Thus, the highly tolerant SMF was utilized as an efficient oil absorbent wherein oils of varying densities could be selectively recovered from an oil/water interface with high (e.g., 137 g g-1 for chloroform and 83 g g-1 for diesel) oil absorption capacity. Moreover, the selective oil absorption capacity of the as-synthesized material remained unaffected at practically relevant severe chemical and physical settings, and the extreme water repellency of the material remained unaltered even after repetitive (at least 50 cycles) use for oil/water separation.

Superswelling Hybrid Sponge from Water Glass for Selective Absorption of Crude Oil and Organic Solvents.

A lightweight super hydrophilic hybrid sponge is designed and demonstrated out of water glass and an organic polymer, which has a macroporous flaky nature and is superflexible with an apparent density of 0.069 g cc–1, ∼97% porosity, and 3000% water uptake. The octadecyltrimethoxy silane-modified hybrid sponge exhibits selective absorption of oil and organic solvents in open water. An absorption capacity in the range 12–23 g g–1 for the test liquids light crude oil, engine oil, paraffin oil, chloroform, kerosene, and hexane is revealed. Absorption capacity by a weight basis was directly proportional to the density and inversely proportional to the viscosity of test liquids. Trials under both stagnant and turbulent conditions verify selective uptake of oil from sea water. Complete regeneration of the absorbent was possible for ten cycles for the test liquids. The work provides design of an affordable water clean-up material alternative to commonly used polyurethane sponges.

Versatile fabrication of anisotropic and superhydrophobic aerogels for highly selective oil absorption

Aerogels have shown great potential as oil absorbents, but they typically suffer from poor hydrophobicity and inferior mechanical property. Herein, anisotropic, superhydrophobic and superoleophilic fluorinated aerogels were prepared by directionally freeze-casting aqueous suspensions of graphene oxide and agarose in the presence of fluorine containing organosilane sol. The hydrogen bonding interactions between graphene oxide and agarose, and the directionally aligned porous structure gave the fluorinated aerogel prominent compression and recoverability properties. Due to its superoleophilicity, the fluorinated aerogel could collect a wide range of organic solvents and oils with excellent absorption capacities, which exceeded those of all cellulose-based aerogels and most carbon-based aerogels. The fluorinated aerogel also proved to be highly efficient in removing oil spills from water surface with outstanding selectivity due to its superhydrophobic and superoleophilic characteristics. Moreover, the high compression flexibility of the fluorinated aerogel facilitated fast and efficient recovery of the absorbed oil by simple mechanical squeezing, and ensured stable performance over repeated use. The present study provided a versatile method for design and fabrication of anisotropic, superhydrophobic and superoleophilic aerogels for environmental remediation and other potential applications.

New Fibrillar Composites Based on Biodegradable Poly(3-hydroxybutyrate) and Polylactide Polyesters with High Selective Absorption of Oil from Water Medium

New Fibrillar Composites Based on Biodegradable Poly(3-hydroxybutyrate) and Polylactide Polyesters with High Selective Absorption of Oil from Water Medium

Superhydrophobic Polyurethane Foam Coated with Polysiloxane-Modified Clay Nanotubes for Efficient and Recyclable Oil Absorption.

Superhydrophobic polyurethane foam (PUF) is prepared by surface coating of halloysite nanotubes. The nanotubes were first modified by surface grafting with hexadecyltrimethoxysilane, followed by assembly on thePUF by dip coating. This treatment makes the water contact angle of the modified PUF higher than 150°. The modified foam has a highly selective absorption of oils and organic solvents. The absorption ratios of the modified PUF for chloroform and dichloroethane reached 104 and 74, respectively. Such superhydrophobic foam can maintain the oil absorption performance even after 10 absorption-squeezing cycles, demonstrating good recyclability. The modified foam can pick up oil or organic solvent continuously and quickly from water's surface. This hydrophobic nanotube coating also enhances the flame retardancy of the PUF, and the modified foam will extinguish itself maintaining its integrity. The preparation method for hydrophobic and flame-retardant PUF by coating with natural clay nanotubes is a simple process and promises scalable applications in oil-water separation.

Continuous ZIF-8/reduced graphene oxide nanocoating for ultrafast oil/water separation

Continuous ZIF-8/reduced graphene oxide (RGO) nanocoating is fabricated by growing ZIF-8 on RGO-coated polyurethane (PU) foam. Surface modification of PU foam can be easily achieved by immersing the PU foam in GO solution, followed by mild thermal treatment to turn the GO layer into RGO layer. Adhesion between polymer foam and ZIF-8 layer was enhanced by the inserted RGO layer because oxygen-containing groups of RGO could interact with Zn2+ precursor of ZIF-8 localizing the layer growth preferentially on the surface of RGO. The synergetic hydrophobic/oleophilic properties of RGO and ZIF-8 enable selective oil absorption of PU foam with an absorption capacity of 15–35 g/g depending on the viscosity of organic solvents. Most of all, the ZIF-8/RGO coated PU foam can filter organic solvent selectively via vacuum filtration, showing ultrafast hexane flux up to 800,000 Lm−2 h−1 and no water flux.

An efficient use of waste PE for hydrophobic surface coating and its application on cotton fibers for oil-water separator

In this study, we report the fabrication of hydrophobic cotton fibers via simple and cost-effective one step easy fabrication approach by utilizing waste recycled polyethylene (PE) gloves. Also, we prepared silres-modified cotton fibers with hydrophobic and oleophilic properties via a simple dip coating process. The resultant both coated cotton (PE and silres) fibers exhibited high repellency towards the water with water contact angle < 135° and superoleophilicity with an oil contact angle ˜ 0°. Due to such special wettability, the as-prepared cotton fibers exhibited high selective oil absorption capacity when used as absorptive materials for separating various oil/water mixtures under acidic, alkaline, and salt aqueous solutions. It was observed that oil/organic solvents absorption capacity of the PE coated cotton fibers was better (16.8–59.7 %, depending on the type of oil) than that of silres modifications. The fabricated PE fiber shows oils and organic solvents absorption ability in the range of 22–61 times their weight as well as good reusability in oil/water separation even after ten absorption-desorption repeated cycles by simple squeezing method. Thus, the utilization of PE waste materials provides an extremely low cost and better approach in the fabrication of promising surfaces for oil/water separation applications.

Durable superhydrophobic glass wool@polydopamine@PDMS for highly efficient oil/water separation

The application of superhydrophobic materials for oil/water separation is receiving increasing attention. Meanwhile, durable superhydrophobic/superoleophilic materials and simple preparation methods are highly desired. Here, inspired by nature, we report a simple method for preparation of durable superhydrophobic glass wool (GW) for highly efficient oil/water separation. The durable and low-cost GW was converted to superhydrophobic simply by polymerization of dopamine followed by chemical vapor deposition of polydimethylsiloxane (PDMS). The polymerization of dopamine generated a lot of polydopamine nanoparticles on the surface of GW microfibers, forming hierachical micro-/nanostructures. The chemical vapor deposition of PDMS efficiently reduced the surface energy. The combination of the hierachical micro-/nanostructure and the PDMS layer successfully made the GW superhydrophobic with a water contact angle of ∼156° and water drops could easily roll off. In addition, the superhydrophobic GW showed high chemical stability in corrosive solutions and oils and high thermal stability. Moreover, the superhydrophobic GW showed high efficiency in selective oil absorption and oil/water separation as well as high recyclability. We believe that the superhydrophobic GW may find application in practical oil/water separation because of its good performance in oil/water separation and high stability under diverse harsh conditions.

Designing Carbon Nanotube-Based Oil Absorbing Membranes from Gamma Irradiated and Electrospun Polystyrene Nanocomposites.

Carbon-based materials are outstanding candidates for oil spill clean-ups due to their superhydrophobicity, high surface area, chemical inertness, low density, recyclability, and selectivity. The current work deals with the fabrication of membrane oil absorbents based on carbon nanotube (CNT) reinforced polystyrene (PS) nanocomposites by electrospinning technique. The spun membranes are also irradiated with the gamma radiation to induce enough crosslinks and thus good polymer-filler interactions. The structural, morphological, and surface properties in addition to the oil/water separation efficiency were investigated by varying the concentration of CNT and the dose of γ-irradiation. Fabricated nanofiber membranes show superior hydrophobicity and selective oil absorption at 0.5 wt.% of CNT concentration. The best mechanical properties are also obtained at this particular concentration and at 15 KGy optimum γ-irradiation dosage. The gamma irradiated PS/0.5 wt.% CNT membrane also exhibits good antibacterial effects against the bacteria, Escherichia coli, in the form of bacterial inhibition rings around the membranes. The present study thus shows the environmental applicability of the fabricated PS/CNT membranes in treating oil-contaminated water.

Highly Durable Superhydrophobic Polymer Foams Fabricated by Extrusion and Supercritical CO2 Foaming for Selective Oil Absorption.

The severe water contamination caused by oil leakage is calling for low-cost and high-performance absorbent materials for selective oil removal. In this study, a scalable green method was proposed to produce polypropylene (PP)/poly(tetrafluoroethylene) (PTFE) composite foams via conventional processing techniques including twin-screw extrusion and supercritical carbon dioxide foaming. To produce the superhydrophobic foam, micro- and nanosized PTFE particles were melt blended with PP and subsequently foamed. Ascribed to the nanofibrillation of microsized PTFE during processing, the fabricated foam exhibited a special highly porous structure with PTFE nanofibrils and nanoparticles uniformly distributed on the pore surfaces within the PP matrix, which resulted in a remarkably high water contact angle of 156.8° and a low contact angle hysteresis of 1.9°. Unlike traditional surface-modified superhydrophobic absorbers, the foams prepared are entirely superhydrophobic, which means that they remain superhydrophobic when being fractured or cut. Moreover, they are highly durable and maintained the superhydrophobicity when subjected to ultrasonication and mechanical sanding. When used in selective oil absorption, the durable foams exhibited excellent absorption efficiency and high stability in repetitive and long-term use. These advantages make the PP/PTFE foam a promising superabsorbent material for water remediation.

Bio‐Based Polybenzoxazine Modified Melamine Sponges for Selective Absorption of Organic Solvent in Water

AbstractMelamine sponge (MS) has drawn increasing attention in the field of oil/water separation. To realize the selective absorption of oil, lots of efforts have been made to change its hydrophilicity to hydrophobicity. Here, several bio‐based main‐chain type benzoxazines with extremely low surface tension are synthesized from a renewable feedstock and loaded on the skeleton of MS through a simple dipping–squeezing–curing process. Consequently, a series of polybenzoxazine‐modified MSs (PB–MSs) are fabricated. With the benzoxazine loading content ranging from 0.13% to 30.4%, the PB–MSs show a high water contact angle (WCA) of 137.8° ± 1.5° to 144.5° ± 1.0° and excellent gravimetric absorption capacity (Qm/m) of 117.0 ± 1.59 to 140.64 ± 0.68 g g−1 when chloroform is used as the oil phase. After 15 absorbing–squeezing cycles, the 67.47% to 76.29% retentive absorption capacity is observed. Notably, the excellent absorption selectivity is reflected by the trace amount of water (ppm grade) in the separated oil phase. The bio‐based benzoxazine shows great potential to functionalize MSs for effective oil/water separation and the application of bio‐based materials in the field of environmental pollution treatment is demonstrated.

Practical Oil Spill Recovery by a Combination of Polyolefin Absorbent and Mechanical Skimmer

The objective of this research is to develop a practical and efficient oil recovery method that can be applied in large-scale crude oil spills in open water. The method is centered on a newly developed polyolefin oil superabsorbent, called “i-Petrogel”, in conjunction with existing mechanical (skimmer) recovery method. The i-Petrogel absorbent can be produced in large scale (>90 kg in our laboratory) by mixing two polyolefin polymers, including a semicrystalline linear low-density polyethylene (LLDPE) thermoplastic and a thermally cross-linkable poly(1-decene-co-divinylbenzene) (D-DVB) elastomer, to form an interpenetrated network structure with porous morphology. In two practical tests, i-Petrogel with a specific composition (LLDPE/D-DVB:1/1 weight ratio) shows selective absorption of Alaska North Slope crude oil on open water surface with fast kinetics and high absorption capacity of more than 40 times that of the polymer weight. In fact, i-Petrogel effectively stops the crude oil weathering process (ev...

Facile preparation of novel hydrophobic sponges coated by Cu2O with different crystal facet structure for selective oil absorption and oil/water separation

In this work, a series of novel Cu2O@sponge composite materials including cubic Cu2O@sponges, octahedral Cu2O@sponges and cubo-octahedral Cu2O@sponges were prepared through a facile dip coating method to coat Cu2O particles on melamine sponge, all of which possess very highly hydrophobic and oleophilic properties. The crystal phase, microstructure and surface functional group of the as-prepared materials were characterized by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectra. The effect of different crystal facet of Cu2O on contact angle, wettability and oil absorption was systematically investigated. Meanwhile, the DFT calculation results show that the surface energy has significant influence on the hydrophobic property of Cu2O, and the calculated surface energies of Cu2O (111) and Cu2O (100) crystal surface are 0.73 and 1.29 J/m2, respectively. On basis of the DFT calculations and experimental results, the octahedral Cu2O with eight (111) crystal facet-coated sponges has the highest hydrophobic properties with the contact angle of 149°, which therefore shows very high separation efficiency in oil/water separation and quickly absorbs floating oils on the water surface. Additionally, all the Cu2O@sponges composite materials indicate excellent oil absorption performances and reusability in terms of hydrophobicity and oil absorbency, which would provide new materials for the potential application of oil/water separation.

Electrospun Gelatin Membrane Cross-Linked by a Bis(diarylcarbene) for Oil/Water Separation: A New Strategy To Prepare Porous Organic Polymers

Porous organic polymers (POPs) as absorbing materials have attracted increasing attention. Here, we report a new approach to prepare these polymers for selective oil absorption from oil/water mixtures. Perfluoroalkylbis(diaryldiazomethane) was synthesized and used to modify the surface of an electrospun gelatin membrane by a carbene insertion reaction, not only to immobilize the porous network morphology by cross-linking but also to introduce perfluoroalkyl groups for oil/water separation. The membrane was characterized to show its surface and bulk properties, as well as its performance for absorption capacity, selectivity, and renewability. This approach offers a new horizon in the preparation of POPs for oil/water separation.

Coating Cellulosic Materials with Graphene for Selective Absorption of Oils and Organic Solvents from Water

Development of efficient and eco-friendly sorbents used for selective oil removal after oil spill disasters is one of the main topics in environmental science. By using various cellulosic materials coated with graphene flakes, using simple, one-step dip-coating method, it was possible to manufacture environmentally friendly, selective oil sorbents. The cellulosic materials of different yarn size and distribution such as cotton roving, gauze, fabric, and cellulosic wipe and Whatman filter paper were chosen. The scanning electron microscopy showed that simple dip-coating of any cellulosic materials into graphene dispersion creates a uniformly distributed nanomaterial coating. The wetting tests confirmed that the coating endowed cellulosic materials with hydrophobic properties, regardless of their initial yarn distribution and purity. Moreover, the water repellent samples were simultaneously highly sorptive towards oils and organic solvents. Sorption tests performed for a representative group of organic solvents and oils have shown that depending on cellulosic material the oil sorption capacity varied from 4 g/g to 33 g/g for cotton fabric and roving, respectively. Moreover, the absorption selectivity of chloroform versus water exceeded 90 % for each sample and reached over 99 % for the graphene coated cotton roving and gauze. Finally, the recyclability tests have shown that graphene coated materials are less fragile for reuse than naturally hydrophobic sorbents.

Fabrication and evaluation of nanocellulose sponge for oil/water separation

Nanocellulose sponge was fabricated by a facile method: freeze-drying of nanocellulose aqueous suspension to sponge state, following by hydrophobic treatment with stearoyl chloride at 50 °C for 1 h. The obtained nanocellulose sponge showed superhydrophobicity (160° of water contact angle) and superoleophilicity with high protection from water but selective absorption of oil. Its absorption capacities for various kinds of oil and non-polar liquids were 25–55 times higher than its dry weight and exhibited excellent selectivity for absorbing of oil which spilled on the surface of water or underwater with high separation efficiency. This superhydrophobic nanocellulose sponge can be easily recovered by simple squeezing and reused at least 10 cycles with remained high separation efficiency. It is expected that such a biodegradable nanocellulose sponge can be applied to solve the oil spill accident and treat the oily wastewater from households and industries.

Preparation of a new superhydrophobic/superoleophilic corn straw fiber used as an oil absorbent for selective absorption of oil from water

BackgroundOil leakages frequently occur during oil product development and oil transportation. These incidents are a vital factor in water contamination, thus leading to serious environmental destruction. Therefore, superhydrophobic/superoleophilic material is one of the solutions to treat oily wastewater.ResultsThis study aimed to develop a simple, fast and low-cost method to treat oily wastewater by synthesizing a new superhydrophobic/superoleophilic corn straw fiber via conventional impregnation. The corresponding results illustrate that abundant homogeneous silica (SiO2) granules evenly accreted on the surface of the prepared fiber were conducive to high surface roughness. Meanwhile, (Heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane, a sort of silane coupling agent, could greatly reduce surface free energy by grafting with SiO2 particles on the corn straw fiber surface. The obtained superhydrophobic/superoleophilic corn straw fiber exhibited a water contact angle of 152° and an oil contact angle of 0° for various oils, strongly demonstrating its considerable application as an oil absorbent that can be applied for oil cleanup. In addition, the prepared fiber displayed a great chemical stability and environmental durability.ConclusionsDue to its high absorption capacity and absorption efficiency, the prepared fiber has great potential as a new oil absorbent for treatment of oily water.

Highly compressible ultra-light anisotropic cellulose/graphene aerogel fabricated by bidirectional freeze drying for selective oil absorption

Low density aerogels are promising materials for oil absorption, but they typically suffer from low compressibility and elasticity. Herein, three-dimensional (3D) highly compressible, elastic, anisotropic, cellulose/graphene aerogels (CGAs) were prepared by bidirectional freeze drying. After the grafting of long carbon chains through chemical vapor deposition, the modified cellulose/graphene aerogels (MCGA) gained superhydrophobicity. The synergistic effects of flexible cellulose, stiff graphene, and the special bidirectionally aligned porous structure gave MCGA outstanding compression and recoverability properties. MCGA was able to recover 99.8% and 96.3% when compressed to 60% and 90% strain, respectively. Due to its ultra lightweight (bulk density of 5.9 mg/cm3) and high surface area (47.3 m2/g), MCGA possesses a remarkable absorption capacity of 80–197 times its weight, which surpasses all hydrophobic cellulose aerogels and most carbon-based aerogels. Furthermore, the high elasticity of MCGA facilitates fast and efficient recovery of the absorbed oil by simple mechanical squeezing, and ensures excellent performance stability over repeated use. The high compressibility and high oil recovery ability though mechanical squeezing has never been achieved by other aerogels. Hence, MCGA can serve as a promising super absorbent material for selective oil absorption and recovery.