Selective Removal Of Oil Research Articles

The evaluation of fibrous disposable facemask for oil sorption and efficient oil/water separation

During the pandemic period, people have used various personal protective equipment including gloves, face mask and face shields. Among them, disposable face mask plays a critical role to control the spread of COVID-19. Hence, there is an urgent need to evaluate and suspend such waste materials from environment. Herein, we have investigated the potential use of disposable face mask as oil sorbent material for efficient oil/water separation due to their hydrophobic/oleophilic characteristics. Some structural characterization techniques are employed to examine the face mask. A number of tests including absorbency, oil/water separation stability in oils and waters, selective removal of oils in different water medium have been systematically investigated. The outcomes show that waste face mask have great potential in the field of oil-water separation that achieve selectively separate the oil from oily wastewater.

Fabrication of superhydrophobic melamine sponge composite sorbent in supercritical carbon dioxide atmosphere for selective and effective oil removal from water

In this study, both the modification of activated halloysite nanotube (HNT) with methyltriethoxysilane (METES) and the fabrication of durable, superhydrophobic (water contact angle: 153.0°) and superoleophilic (oil contact angle: 0 °) melamine sponge (MS)-HNT-METES sorbent material (MS-METES) were achieved in supercritical carbon dioxide (scCO2) atmosphere. For the coating of MS with clay mineral and METES through sol-gel reaction in scCO2, optimal process conditions were determined to be pressure difference of 60 bars at 35 °C, solvent/METES mass ratio of 7.5, METES/MS mass ratio of 10, and degas time of 400 s. Successful preparation of MS-METES was proven by XPS, FTIR, 29Si-MAS NMR, SEM, and contact angle measurements. MS-METES displayed excellent sorption capacity for various petroleum products, oils, and organic solvents (49.6–122.4 g/g), remarkable oil-water separation efficiency (99.1%, for continuous separation technique), high selectivity for oil/organic solvent in acidic, salty, and alkaline solution conditions, good reusability, chemical stability and robustness, and outstanding flexibility and mechanical stability. We believe that the innovative process used in this study will have great potential to be used by researchers in the direct fabrication of new superhydrophobic and superoleophilic sorbent materials for the selective removal of oil and organic solvent spills from water.

Hydrophobic sponge derived from natural loofah for efficient oil/water separation

Polymer sponge and carbon aerogel have received widespread attention because of their high specific surface area and controllable wettability. However, the complex manufacturing processes and non-renewable raw materials of these porous materials have limited their practical applications. Herein, we conducted the thermal chemical vapor deposition (CVD) of hydrophobic methyltrichlorosilane (MTCS) on loofah sponge (LS), which led to the formation of a novel oil-adsorbing hydrophobic MTCS-coated loofah sponge (MTCS-LS). The obtained MTCS-LS retained the interconnected 3D porous structure and robust structure stability of natural LS, while exhibited dramatically improved hydrophobicity with contact angle of 137° in the pH range of 2–12. This unique characteristic conferred MTCS-LS selective oil removal ability from water, and MTCS-LS possessed oil sorption capacity of 13 times of its dry weight and high separation efficiency (>92%). Results of the adsorption-squeezing tests proved that the excellent reversible compressibility of natural LS was maintained after the silanization modification. Compared to other known oil-adsorbing materials, the MTCS-LS displayed apparent advantage in adsorbing oils with high viscosity (e.g. crude oil). Our study provides a simple approach to exploitation of biomass in pollutants removal.

The construction of composite hydrogel evaporator with interfacial heating performance and its application in water treatment

To meet the needs of sewage cleaning and clean drinking water, a multifunctional photothermal device is designed in this paper, which mainly includes the non-infiltrating layer of copper stearate, bismuth tungstate and copper oxide composite hydrogel. By improving the synthesis process, sheet-like copper stearate and flower-like bismuth tungstate were prepared, realizing the load of canvas, felt and fabric, with the contact angles reaching 158º, 162º and 161º, respectively. The nonwetting layer has the performance of not only selective oil removal, but also mechanical stability. Through traditional non-infiltrating materials, dyes cannot be degraded, while with the introduction of bismuth tungstate, superhydrophobic materials are given photodegradation properties, thus solving the recovery problem of powder photocatalysts. The photodegradation stability was demonstrated via multiple photodegradation processes by calculating the reaction kinetic coefficient, with a degradation efficiency of greater than 90%. The position of valence (1.9 eV) and conduction (-0.735 eV) band of bismuth tungstate was calculated based on Mott-Schottky curve, DRS and VB-XPS. With the construction of copper oxide composite hydrogel, the mechanical stability was improved and an efficiency of 1.76 kg•m−2•h−1 was obtained. The composite hydrogel device can also be used to treat the aqueous solutions containing metal ions and dyes, which operates stably in aqueous solutions containing 3.5% NaCl without salt crystallization, thus proving the application value of the photothermal device.

Development of corn-stalk based aerogel for selective removal of oil from water

The recurrent oil spillage owing to natural processes or oil transportation in marine bodies causes substantial environmental problems and aquatic life damage. In this regard, the present work envisages preparing an aerogel using waste corn-stalk as the base material. The synthesis method is easy, cost-effective, and scalable. The prepared aerogel is ultra-lightweight and possesses low density, high surface area, and porosity. Further, the water contact angle of the prepared aerogel is 142.5°. The oil sorption studies revealed that the maximum oil sorption capacity of the prepared aerogel is 28 g/g. The oil sorption kinetic study revealed that experimental data of oil sorption follows second-order kinetics. Moreover, the aerogel possesses recyclability, as seen from the oil sorption capacity of 15.22 g/g after five cycles. Furthermore, it could uptake other organic solvents with appreciable sorption capacity, thus the as-prepared aerogel can be used for the selective removal of different organic solvents from water.

Mesoporous SiO2 decorated superhydrophobic fabric evaporator with selective oil removal and Rh B photodegradation performance

Solar steam generation devices assembled based on interfacial heating technology show the ability to produce clean water, while it faces challenges in the sewage environments. The superhydrophobic fabric was used to selectively adsorb surface oily pollutants based on its non-wettability. Soluble pollutants remaining in water after evaporator treatment can be further removed through photodegradation. Herein, the device composed of superhydrophobic C3N4/Bi2MoO6 heterojunction, water supply layer and CuO photothermal layer was assembled to remove oily and water-soluble pollutants and produce clean water. The contact angle of water on the superhydrophobic C3N4/Bi2MoO6 surface reaches 154° and shows the selective adsorption of cyclohexane. The prepared bulk catalyst C3N4/Bi2MoO6 not only indicate the stability of reuse, but also maintained the degradation efficiency of 98.7% under outdoor light conditions. Through the active species capture experiments, •O2− was verified as the main active material in the photodegradation process. The formation of Type II heterojunctions between C3N4 and Bi2MoO6 facilitated the separation of e−/h+ at the C3N4/Bi2MoO6 interface.

Magnet-assisted selective oil removal from water in non-open channel and continuous oil spills clean-up

• A superhydrophobic-superoleophilic, magnetic foam is synthesized. • The foam can selectively remove oil from water in both open and non-open environment. • The foam can be reused for multicycle oil adsorption, and shows long-term durability. • A novel magnetic attraction strategy is proposed to assemble the foam. 3D porous superhydrophobic materials have been widely developed for selective oil adsorption from open water surface, but it is still challenging for the oil removal from water in non-open environment. Herein, a superhydrophobic-superoleophilic, magnetic and 3D porous carbon-based foam, containing carbon-nanosheet frameworks (CNFs), iron/iron carbide nanoparticles (Fe/Fe 3 C NPs) and polydimethylsiloxane (PDMS) coating, is synthesized via ferric nitrate assisted chemical blowing and carbonization of polyvinylpyrrolidone (PVP), and post-treatment by PDMS. The PDMS-CNF-Fe/Fe 3 C foam shows low density (<90 mg cm −3 ), extremely high compressive strength (≈47.7 kPa) and selective oil removal ability with high oil adsorption capacity (>2700% for chloroform). The remarkable paramagnetic property of the foam enables it to be capable of removing oil selectively from water in non-open channels under assistance of a magnet bar. Additionally, the foam can be easily reused for oil adsorption by heating or releasing in other solvents with negligible adsorption capacity decline. The chemically stable carbon-based matrix and PDMS coating impart the foam with excellent high/low temperature stability and certain corrosion resistance, which facilitate effective oil removal from caustic aqueous solutions (especially in alkaline and salty conditions) or under extreme temperature environment. The 3D porous and self-similar micro structures enable the foam to be mechanical abrasion resistant, and the foam retains its water repellence and oil adsorption capacity after repeated and intensive abrasion by sandpaper. Moreover, we propose to assemble the foam with a vacuum pumping system by ring-shaped magnet to realize continuous oil removal. The mechanochemically durable PDMS-CNF-Fe/Fe 3 C foam with magnetic response capacity and outstanding reusability is therefore a promising candidate for selective oil removal from water in both open and non-open environments under remote control of magnet. The novel magnet assisted assembly strategy also provides a simple, reliable and automatable method to integrate magnetic 3D oil adsorbent with pumping system for large-scale oily wastewater remediation.

Exfoliated graphite blocks with resilience prepared by room temperature exfoliation and their application for oil-water separation

Exfoliated graphite (EG) blocks are prepared from the ultra-large flakes of graphite by intercalation of H2SO4 using a large amount of H2O2 at 5 °C and following exfoliation at 30 °C. By the exfoliation in a closed container, EG blocks with the bulk densities of 0.008–0.024 g/cm3 are successfully prepared. The resultant EG blocks have high sorption capacities for a diesel oil, up to 45 g/g. The EG blocks after oil sorption can get certain resilience for compressive stress with high reproducibility by compression-release cycles, which allows us to apply the compression-releasing for the oil sorption-desorption of the EG blocks. The performance of cyclic oil sorption-desorption by compression-releasing of EG block is compared with those of filtration and distillation. Since the resultant EG blocks had sufficient mechanical strength, the continuous removal of oil floating on the water surface is possible, exporting oil through a catheter inserted into the block and connected to a peristaltic pump. By warming up by Joule heating, even a crude oil having high viscosity can be continuously removed from the water with sufficient rate. The high hydrophobicity and lipophilicity of EG make selective removal of oil from water possible.

Superhydrophobic leached carbon Black/Poly(vinyl) alcohol aerogel for selective removal of oils and organic compounds from water

The remediation of oil spills and treatment of oily wastewater remains challenging to cope with nowadays. This has caused a surge in demand on adsorbent materials with multi-functionalities to effectively separate oils and nonpolar solvents from water. A superhydrophobic composite aerogel prepared from industrial waste-derived leached carbon black waste (LCBW) and polyvinyl alcohol (PVA) was developed in this work via conventional freeze-casting followed by surface coating. The composite aerogel was ultralight and porous with porosity >85% and tunable density ranging between 0.015 and 0.065 g/cm3. It was found that the embedded LCBW in the PVA network is crucial to impart superhydrophobicity and superoleophilicity to the aerogel as it enhances the surface roughness. Wettability test showed that composite aerogel prepared from 0.5 wt% PVA at PVA/LCBW ratio of 1 exhibited the highest water contact angle (156.7 ± 2.9°). LCBW also improved the thermal stability of the composite aerogel. With its superior selectivity, PVA/LCBW aerogel was used as selective adsorbent for a variety of oils and organic solvents. The adsorption test showed that the composite aerogel exhibited an adsorption capacity up to 35 times its original weight and could be reused repeatedly and easily recovered through a simple drying method.

Highly Hydrophobic Polydimethylsiloxane-Coated Expanded Vermiculite Sorbents for Selective Oil Removal from Water.

Naturally abundant vermiculite clay was expanded by using an aqueous solution of H2O2 and its surface was modified with ultra-thin polydimethylsiloxane (PDMS) using facile thermal vapor deposition to prepare an ecologically friendly, low-cost oil sorbent that plays an important role in oil spillage remediation. The resulting PDMS-coated expanded vermiculite (eVMT@PDMS) particles exhibited adequate hydrophobicity and oleophilicity for oil/water separation, with numerous conical slit pores (a size of 0.1–100 μm) providing a great sorption capacity and an efficient capillarity-driven flow pathway for oil collection. Simply with using a physically-packed eVMT@PDMS tube (or pouch), selective oil removals were demonstrated above and beneath the surface of the water. Furthermore, these sorbents were successfully integrated and then applied to the advanced oil-collecting devices such as a barrel-shaped oil skimmer and a self-primed oil pump.

Construction of superhydrophobic directly Z-scheme bismuth oxybromide/silver phosphate fabric surface with UV shielding and enhanced visible light absorption activity

Various forms of pollutants discharged from industrial and life; how to treat the opposite water-soluble pollutants at the same time is a challenge. Here, a superhydrophobic BiOBr/Ag3PO4 fabric (SH fabric) bulk material was prepared aiming at the diversity of pollutants. Water (WCA=160°) and oil contaminants (spread) have different wetting behavior on fabric surfaces. The high recovery efficiency for oil pollutants was achieved by using the selective oil removal property of the SH fabric. Meanwhile, the pollutants in the aqueous phase were removed by photocatalyst after oil/water separation. Mechanism analysis demonstrated that the direct Z-type heterojunction formed between BiOBr (EVB=1.66 eV; ECB=−1.08 eV) and Ag3PO4 (EVB=3.03 eV; ECB= 0.6 eV). It is worth noting that the SH fabric exhibited good mechanical stability and UV shielding performance, which have potential application in environmental control.

Superhydrophobic cellulose nanofibril/silica fiber/Fe3O4 nanocomposite aerogel for magnetically driven selective oil absorption

The development of superabsorbent materials with high absorption capacity, selectivity, and stable performance is needed for oil recovery. Remote-controlled oil absorption is highly favorable for oil absorption in harsh environment. In this study, a novel ultralight superhydrophobic nanocomposite aerogel composed of organic cellulose nanofibrils (CNFs), inorganic silica fiber, and magnetic Fe3O4 nanoparticles was developed through a simple freeze drying and surface modification method as a magnetically driven superabsorbent material. The aerogel has a highly porous and fibrous structure that contains hierarchical micro-nano surface topography. Low surface energy carbon–fluorine chains were grafted on aerogel surface which rendered the aerogel superhydrophobic. The addition of Fe3O4 nanoparticles significantly improved the surface area, compressive property, water contact angle, and the separation efficiency of the aerogel, but reduced the absorption capacity due to the increase of bulk density. The developed nanocomposite aerogel has a high absorption capacity (weight gain of 3420–5837%), separation efficiency ~ 100%, and a water contact angle of 150°. It also demonstrated high elasticity and performance stability in repetitive use. Given its magnetic property, the CNF/silica/Fe3O4 nanocomposite aerogel is a promising candidate for selective oil removal from open water, especially for remotely controlled applications.

Superhydrophobic metal organic framework doped polycarbonate porous monolith for efficient selective removal oil from water

A series of superhydrophobic polycarbonate porous monoliths modified with metal organic framework (Z8/PC) were firstly fabricated through a facile thermally impacted non-solvent induced phase separation method for efficient selective oil/water separation. The performance of the monoliths on oil/water separation was evaluated in terms of selectivity, equilibrium adsorption capacity, corrosion resistance, kinetics, and circulation. The results showed that the use of ZIF-8 significantly compensated for the shortage of pure monolith. Compared with pure PC monolith, the hydrophobic angle of the Z8/PC-2 monolith promoted from 136.18° to 154.25° due to the micro-nano flower surface. Meanwhile, the Z8/PC-2 monolith displayed a more intricate and continuous interconnected 3D hierarchical micro-nano structure, which possessed the monolith a higher specific surface area of 146.84 m2 g−1 and porosity of 89.5%. What’s more, more superior oil/water separation abilities of Z8/PC-2 monolith were manifested by the selective removal of oil or organic solvent from water within 30s, high equilibrium adsorption capacity, and excellent corrosion resistance. In addition, the ten-cycle regeneration of porous monoliths via centrifugation or evaporation displayed additional attractiveness. Therefore, porous Z8/PC monolith will be a promising candidate for the efficient selective oil/water separation of oil spills and organic solvents.

A General in Situ Deposition Strategy for Synthesis of Janus Composite Fabrics with Co(CO3)0.5OH·0.11H2O Nanoneedles for Oil–Water Separation

For a fixed porous framework, developing an efficient composite material with selective removal of oil and water from an oil–water mixture is of significance but challenging because of the effect of its decreased pore size and porosity and single wettability. Herein, a Janus fabric via a general strategy of surface hydrophobization, oxidation treatment, and chemical bath deposition is constructed. The obtained composite fabric consists of a hydrophilic Co(CO3)0.5OH·0.11H2O nanoneedle/cotton fiber side and a hydrophobic cotton fiber side, which endows it with a unidirectional water transportation capability and exhibits an effective separation for both light and heavy oil–water mixtures under gravity. Especially using the water wetted composite fabric as a separation cell, the built-in lyophobic layer originating from fluid passed through the nonwetting region of wetted fabric decreases the unfavorable contact between lyophobic interface and separated liquid, and the permeation flux is enhanced by 214.5% for water and by 112.5% for oil, respectively, compared to that in the pristine fabric, whereas it has no effect on the separation efficiency of a heavy oil–water mixture. Meanwhile, the Janus composite fabric exhibits an excellent oil–water separation stability and durability and is easily recycled for long-term use. The facile Janus material synthesis strategy is available on various substrates including melamine sponge, Ni foam, cellulose paper, and other nanosheet arrays on cotton fabric. Thus, this work provides a route to develop multifunctional materials for potential application in quick oily wastewater remediation.

Rapid, large-scale preparation of non-wetting bismuth oxybromide surface and its practical outdoor applications for the water purification

The availability of two-dimensional composite photocatalyst materials under rapid, large-scale and mild conditions is a bottleneck for the application of water pollution treatment materials. In this paper, a superhydrophobic-BiOBr composite (WCA = 158°) with size of 0.5 m × 0.5 m was prepared by spraying and combustion methods within 1 h. The obtained fabric has selective oil removal performance and can be used for degrading the water-soluble pollutant under outdoor exposure to sunlight irradiation. The degradation efficiency of rhodamine B can reach 97.4% after 140 min. This excellent light activity can be attributed to the higher roughness requirements of the superhydrophobic fabric that the catalyst exposed area be increased. This work discusses not only the photodegradation active species (O2−) as well as the valence band (3.025 eV.) and conduction band (0.315 eV) information, but also the mechanical stability and verification of large-scale preparation. It also provides a new solution for the practical application of photodegradable materials.

Eco-friendly preparation of superhydrophobic copper surfaces for oil/water separation

Copper surfaces decorated with micro- and nanostructures can be applied to self-cleaning superhydrophobic surfaces, energy devices and pollution remediation. Wet chemical etching is the classical strategy to grow micro- and nanostructures on copper surfaces. However, such processes usually produce hazardous chemical waste. Here, we present a one-step, eco-friendly and solvent-less alternative to conventional wet chemical methods. Our method involves the use of volatile compounds released from yolk and egg white of boiled chicken eggs as green oxidants for the growth of micro- and nanostructures on the copper surface. After treatment with egg components, copper substrates were modified with stearic acid to make them superhydrophobic. Stearic acid-coated substrates had a contact angle of about 150°, thus confirming their superhydrophobicity. Similar to copper sheets, superhydrophobic copper meshes were also prepared and used for the selective removal of oil from oil/water mixture. Results show that our method produces a wide range of shapes including hollow and solid spheres, nanoflakes, nanoneedles and dome shapes. We found that H2S, the major volatile compound emitted by eggs, is mainly responsible for the growth of microstructures. Therefore, our method can be used both to capture H2S and to design specific surfaces. The mesh exhibited excellent separation efficiency, more than 95% for the organic solvents. A key advantage of our method is that it can be performed also using waste and expired eggs.

Magnetic superabsorbents based on nanocellulose aerobeads for selective removal of oils and organic solvents

Superabsorbent aerogels are fascinating materials for oil and chemical spillage cleanup. However, the development of an economic and efficient superabsorbent is still highly challenging. In this study, we introduce a novel approach to prepare very low density (0.005 g/cm3), highly porous (>99.6%), economic, reusable, hydrophobic, and magnetic spherical cellulose nanofiber-derived aerogels (i.e., aerobeads) prepared from waste boxboards via a simple freeze-drying procedure. The spherical aerobeads were fabricated easily after dropping a hydrophobized nano-fibrillated cellulose solution containing magnetic Fe3O4 nanoparticles into liquid nitrogen. The aerobeads showed outstanding absorption efficiency for several oils and organic solvents (up to 279 g/g with castor oil) and demonstrated excellent selectivity for absorbing oil from an oil/water mixture. Moreover, they were easily collected by an external magnet, indicating excellent recyclability and reusable for at least 10 cycles while still retaining supreme absorption capacity (up to 101 g/g for diesel oil). This study proposes an economic and novel method for the large-scale preparation of spherical superabsorbent aerobeads, making them a promising candidate for the efficient and sustainable cleaning of oil and chemical spills.

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.

Highly hydrophobic ZIF-8 particles and application for oil-water separation

ZIF-8(zinc-methylimidazolate framework-8) is reported for selective removal of oils from water surface, Experiment results show that the highly hydrophobic ZIF-8 particles could be reused in water-oil separation for 20 cycles. • The as-synthesized ZIF-8 exhibited highly hydrophobic and superoleophilic properties. • The highly hydrophobic ZIF-8 particles could be reused in water-oil separation for twenty cycles. • ZIF-8 particles could be regenerated by heating combined with reduced pressure treatment. ZIF-8(zinc-methylimidazolate framework-8), one of the zeolitic imidazolate frameworks (ZIFs), was put into a tea bag for selective removal of oils from water surface, and exhibits strong hydrophobicity with a water contact angle of 142°, ZIF-8 particles combined with highly hydrophobic and superoleophilic properties. Our Experiment results showed that the highly hydrophobic ZIF-8 particles and the ZIF-8/tea bag could be reused in oil-water separation for twenty cycles. More importantly, the oil could be readily removed from the surfaces of particles by heating combined with reduced pressure treatment whereas the particles still kept highly hydrophobic and superolephilic characteristics, which render its potential applications in the cleanup of oil spills and the removal of organic pollutants on water surface.

Superhydrophobic three-dimensional porous ethyl cellulose absorbent with micro/nano-scale hierarchical structures for highly efficient removal of oily contaminants from water

The development of efficient absorbent materials is of global importance for oil spillage cleanup and environmental protection. In this work, a novel superhydrophobic micro/nano-scale hierarchical structured ethyl cellulose sponge was successfully fabricated via an eco-friendly salt-templating method followed by immobilizing silver nanoparticles on the surface and subsequent modification with long-chain alkanethiols. The as-prepared sponge with unique micro-nano structure and porous interconnected network exhibited low density (<17 kg m−3), high porosity (>98%) and robust superhydrophobicity (θwater = 161.3°, θoil = 0°, sliding angle = 3.6°). The sponge could collect a wide range of organic solvents and oils with absorption capacity of 36–48 times of its own weight. Furthermore, the absorption capacity decreased slightly to 89.8% of its initial value after 50 cycles, demonstrating excellent recyclability of the sponge. It was believed that the superhydrophobic/superoleophilic sponge would be a promising absorbent material for the selective oil removal and recovery in environmental remediation.