Excellent Oil-water Separation Research Articles

A superhydrophobic PVDF-based membrane containing Metal-organic framework for efficient Oil-water separation

The discharge of oily wastewater has caused heavy burden to the environment, so it is necessary to solve this problem. Membrane separation, as a simple and efficient separation technology, has attracted widespread attentions in the field of oil–water separation. In this work, a superhydrophobic PVDF-based membrane containing MOFs with small size (ZJU-64-CH3-S) was prepared. ZJU-64-CH3-S with different amounts (200 mg, 400 mg and 600 mg) were added into PVDF to obtain ZJU-64-CH3-S/PVDF membranes, which named as M1, M2 and M3. They displayed ideal hydrophobicity according to the large water contact angle (about 130°). And composite membranes showed good oil adsorption and excellent oil–water separation efficiency. In particularly, the oil flux of M2 reached to 333.33 L/(m2·h) and its oil–water separation efficiency was as high as 99 %. The composite membrane was expected to be used in the field of oil–water separation.

Development of superhydrophobic PVA/CNC nanofibrous membranes for enhanced oil-water separation

Effective oil–water separation is crucial for environmental purification and the remediation of oil pollution, yet current methods face limitations in efficiency, durability, and environmental impact. In this study, we aimed a green nanofibrous membrane with excellent oil–water separation efficiency, addressing the significant environmental challenge of separating oil from water in various states. For this purpose, polyvinyl alcohol (PVA)-based nanofibers were prepared by aqueous electrospinning. The mechanical strength of the nanofibers was reinforced by adding cellulose nanocrystals (CNCs). The surface of the nanofibers was modified with hexadecyltrimethoxysilane (HDTMS) to induce hydrophobicity, evidenced by the increase in contact angle from 44.41° to 133.19°, facilitating effective oil separation from various states, including dispersed, suspended, and emulsified states. The prepared PVA/CNC-HDTMS nanofiber showed 194 %, 539 %, and 407 % higher tensile strength, yield strength, and Young’s modulus than PVA nanofibers, respectively. The oil sorption capacity of the nanofibers varied widely from 17.01-113.76 g/g, which is strongly influenced by the viscosity and volatility of the oil species. The durability and reusability of the nanofibers were well maintained, even after being reused more than 10 times without morphological deterioration. In separating oil–water mixtures, the nanofibers maintained a high flux of 40,039 L/m2h and a separation efficiency of 99.2 % under pressurized conditions. Additionally, the nanofibers achieved a separation efficiency of 98.5 % in oil–water emulsion states.

Superhydrophobic cotton for addressing fatbergs through oily wastewater treatment

Fats, oils and grease (FOGs) deposits in sewers have recently become a significant problem, causing financial strain on water companies, damaging sewer lines, and exposing the environment to dirty water through sanitary sewer overflows. Despite the proactive use of grease traps/interceptors for physical oil-water separation, the issue of FOG deposits persists. This study proposes the use of adsorption-based oil-water separation, employing superhydrophobic cotton, as a new alternative method for removing FOGs. Durable superhydrophobic cotton was successfully prepared using a simple two-step sol-gel method, with octadecyltrimethoxysilane (ODTMS) as a modifying silane. The resulting cotton samples demonstrated remarkable superhydrophobicity, evidenced by water contact angle (WCA) above 154°. Additionally, it exhibited exceptional durability and stability when exposed to hot water, harsh acidic and alkaline solutions, as well as during a laundry test. Moreover, the cotton displayed excellent oil-water separation efficiency (> 98 %) and maintained consistent performance throughout 20 reuse cycles, highlighting its high reusability. This approach holds the potential to address the prevailing FOG deposit issues and contribute to more efficient and sustainable wastewater management practices.

Wood sponge with photothermal, magnetically driven, and superhydrophobic characteristics for high-viscosity oil–water separation

In this work, naturally degradable porous balsa wood was used as a raw material to prepare a highly elastic wood sponge (WS) substrate using a two-step chemical method and a freeze-drying method. The surface hydrophobic modification of Fe3O4 nanoparticles using the fluorine-free material octadecyltrimethoxysilane (C18TMS) solved the problem of agglomeration caused by the high nanoparticle surface energy. Polydopamine (PDA), hydrophobically modified Fe3O4 (C18TMS/Fe3O4), and low-surface-energy polydimethylsiloxane (PDMS) were sprayed onto WS substrates using a simple spraying method. An environmentally friendly adsorption sponge with photothermal, magnetically driven, and superhydrophobic properties was prepared for the first time using this method. The prepared sponge had a water droplet contact angle of 156.8° and exhibited excellent oil–water separation performances. Due to the addition of PDA and Fe3O4, the modified sponge exhibited excellent photothermal performance, rapidly heating to 63.4°C under a sunlight intensity of 1 kW m−2. The superhydrophobic WS prepared in this experiment provides a more environmentally friendly and low-cost way for high viscosity oil–water separation and targeted removal of oil pollution.

Facile preparation of poly(melamine formaldehyde) sponge/bacterial nanocellulose composite for oil-water separation

The treatment of a large amount of oil-water mixture generated by oil leakage accidents is an environmental issue that cannot be ignored. Achieving fast and efficient oil-water separation is a goal pursued by both academia and industry. In this paper, poly(melamine formaldehyde) (PMF) sponges were modified by the hydrophilic bacterial nanocellulose (BNC) through mild and facile conditions. With increasing the concentration of BNC dispersion used, the pore size of the composite decreases. The water contact angle of the obtained PMF/BNC composite surface is 0° or so, and the underwater oil contact angle is greater than 150°. Based on its hierarchical pore structure, hydrophilicity and oil repellency, the PMF/BNC composite exhibits excellent oil-water separation efficiency and water treatment flux for layered oil-water mixture (>1.0×107L/(m2·h·bar)). In addition, the PMF/BNC composite also exhibits high water treatment flux and oil-water separation efficiency (> 95%) for oil-water emulsion with and without surfactant. Stacking several composite slices could achieve higher oil-water separation efficiency.

Multi-functional self-cleaning superhydrophobic cotton fabric as photothermal-reinforced crude oil separator, oil skimmer and underwater oil absorbent

Removing oil pollution from seawater prior to its desalination helps in saving time and cost. In this study, a novel superhydrophobic cotton fabric with photothermal effect and self-cleaning property was prepared via the incorporation of Fe3+-polydopamine (PDA) coating and carbon nanotubes (CNTs) on the fabric surface (termed as CF@PDA/CNT), followed by the grafting of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and octadecylamine (ODA) (termed as the CF@PDA/CNT-GPTMS-ODA). CF@PDA/CNT exhibits good desalination with photothermal conversion capability on the high-salinity water (evaporation rate > 1.11 kg/(m2⋅h)), providing an effective basis for the preparation of the photothermal-assisted oil–water separator (CF@PDA/CNT-GPTMS-ODA), with which the crude oil permeation time was improved from 58 s without light to only 9 s with light, showing the pronounced contribution of the photothermal effect on the oil permeation. In addition, CF@PDA/CNT-GPTMS-ODA used in the form of oil skimmer and underwater oil absorbent demonstrates excellent oil–water separation performance (separation efficiency > 97 %). Notably, the fabric can isolate various oil phases from both pure water and simulated seawater, with separation efficiencies exceeding 97 %. This novel material offers a promising solution for addressing complex water pollution issues and introduces a potential approach for integrating photothermal conversion effect into the field of oil–water separation.

Superhydrophobic fluorinated metal–organic framework (MOF) devices for high-efficiency oil–water separation

A series of fluorinated UiO-66 was prepared using the bottom-up method. The composites of 2CF3-UiO-66 and cotton show excellent oil–water separation efficiency (up to 99.66%).

Simple one-pot fabrication of durable superhydrophobic cotton wool using octadecyltrimethoxysilane modified silica-sol for oil-water separation

A fluorine-free superhydrophobic cotton is successfully fabricated using a simple and cost-effective one-pot synthesis method, employing octadecyltrimethoxysilane (ODTMS) as a modifying silane in a silica-sol. Unlike conventional techniques that utilise coupling agents or post-synthesis curing methods to enhance coating stability, this approach eliminates the need for extra chemicals thus saving time and reducing fabrication cost. The prepared cotton demonstrates remarkable superhydrophobicity, as evidenced by a water contact angle of 159°. Additionally, it exhibits exceptional durability and stability when exposed to harsh acidic and alkaline solutions, as well as during laundering test. Moreover, the cotton displays excellent oil–water separation efficiency (>99.0 %) and maintains consistent performance throughout 20 reuse cycles, highlighting its high reusability. Furthermore, the modified cotton is highly effective for separating oil-in-water emulsions, even for highly stable emulsions, achieving separation efficiencies above 90.0 %. The fabrication process is simple and environmentally safe, offering an economical and viable solution for industries handling oily wastewater. Overall, this fluorine-free superhydrophobic cotton presents a promising and cost-effective option for various industrial applications.

Fabrication of bio-based biodegradable poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composite foams for highly efficient oil-water separation

The open-cell bio-based biodegradable polymer foams show good application prospect in dealing with the serious environmental issue caused by oil spill and organic solvents spills, while the cell structures and hydrophobic properties of the foams limit their performance. In this work, the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was selected to help prepare bio-based biodegradable poly(lactic acid) (PLA) foams. Based on a two-step foaming method, the crystallization ability of different samples was regulated by the “original crystals” together with PHBV in the foaming process, where skeleton structures were provided to facilitate the open-cell structures and promote their mechanical property. As illustrated, PHBV facilitated the formation of open-cell PLA foams, where the foams displayed superior oil-water separation capacity. The maximum volume expansion ratio of the foams was 80.08, the contact angle of deionized water reached to 134.5°, the adsorption capacity for oil or organic solvents was 10.8 g/g-51.8 g/g, and the adsorption capacity for CCl4 can still maintained 83.5 % of the initial value after 10 adsorption-desorption cycles. This work not only clarified the foaming mechanism of open-cell foams, but also provided a green and simple method for preparing bio-based biodegradable foams possessing excellent oil-water separation performance.

TiO2-PAA-SiO2 pearl chain blend modified polyvinylidene fluoride ultrafiltration membrane with excellent oil-water separation, anti fouling performance and durability

ABSTRACT In this work, a new type of composite nanoparticles, ‘pearl chain’, was developed by linking titanium dioxide and silicon dioxide by polyacrylic acid polymer chains, and the prepared TiO2-PAA-SiO2 composite nanoparticles were analysed by SEM, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy and thermogravimetric analysis, zeta potential, x-ray diffraction, etc. The success of this work was verified by the successful linking of TiO2-PAA-SiO2 composite nanoparticles.TiO2-PAA-SiO2 composite nanoparticles were analysed to verify the successful attachment of pearl chains. The obtained TiO2-PAA-SiO2 were subsequently blended in different ratios to prepare polyvinylidene fluoride (PVDF) ultrafiltration membranes. The membrane performance was tested by porosity and water contact angle measurements, scanning electron microscopy, as well as experiments using bovine serum proteins and MTBE interception. The results showed that when a certain amount of TiO2-PAA-SiO2 was added, the surface wettability, porosity and permeability of the prepared modified composite membranes were significantly improved, and the BSA adsorption rate was increased from 71.59% to 80.86%, and the retention rate of MTBE was increased by 77%, in addition to showing a better anti-pollution effect (FRR: 91.07%). It was finally concluded that the prepared membranes embedded with 1.0 wt.% TiO2-PAA-SiO2 nanofillers showed good overall filtration performance, better contamination resistance and remarkable durability. The present work successfully demonstrated the feasibility of using polyacrylic acid chemical chains to connect nanoparticles with different functions to prevent particle loss and substantially enhance membrane performance, which is valuable for bridging connection of composite nanoparticles and exploring the development of high-performance ultrafiltration membranes.

Biomimetic stable cellulose based superhydrophobic Janus paper sheets engineered with industrial lignin residues/nano-silica for efficient oil-water separation

The preparation of degradable, stable, acid- and alkali-resistant oil/water separation materials from renewable biomass resources is a vast challenge as well as vital for sustainable development. Inspired by the asymmetric wettability of lotus leaf, a brand-new type of cellulose-based Janus paper sheets with anisotropic wettability was successfully designed and engineered with industrial lignin residues and nano-silica. By easy spraying of coatings to construct hierarchical networks, the papers achieved robust superhydrophobicity in a variety of acidic and alkaline conditions (pH = 3–11) with a water contact angle about 153°. Benefiting from the lipophilicity of lignin and the hydrophilicity of cellulose, Janus paper sheets were endowed an excellent oil-water separation efficiency. It reached a maximum flux of 654.46 L·m−2h−1 of dichloromethane in the solvent-water mixture. Furthermore, the mechanical properties, folding and tearing resistance of the obtained materials were significantly improved due to the splendid interfacial adhesion, rendering them satisfied stability and durability. The oil-water separation efficiency of the Janus paper sheets was maintained at 90% over 8 recycles. In contrast to cumbersome oil-water separation materials, the proposed Janus paper sheets can operate as an efficient, stable, acid- and alkali-resistant, abrasion-resistant biodegradable material to effectively absorb heavy oils and waste organic solvents. A novel application possibility is provided by such an environmentally friendly, reliable, and efficient preparation process for oil-water separation.

Facile Fabrication of High-Performance Superhydrophobic Reusable Oil-Absorbing Sponges

Wastewater treatment from oil, oil products and organic mixtures is a very relevant topic that can be successfully utilized to solve problems of severe environmental pollution, such as oil spills, industrial oily wastewater discharges and water treatment in the water treatment process. In this work, we have developed new superhydrophobic magnetic polyurethane (PU) sponges, functionalized with reduced graphene oxide (RGO), MgFe2O4 nanoparticles, and silicone oil AS 100 (SO), as a selective and reusable sorbent for the purification and separation of wastewater from oil and organic solvents. The surface morphology and wettability of the sponge surface were characterized by scanning electron microscopy (SEM) and a contact angle analysis system, respectively. The results showed that the obtained PU sponge PU/RGO/MgFe2O4/SO had excellent mechanical and water-repellent properties, good reusability (lasted more than 20 cycles), as well as fast (immersion time 20 s) and excellent absorption capacity (16.61–44.86 g/g), and additional good magnetic properties, which made it easy to separate the sponge from the water with a magnet. The presence of RGO in the composition of the nanomaterial improves the separating and cleaning properties of the materials and also leads to an increase in the absorption capacity of oil and various organic solvents. The synthesized PU sponge has great potential for practical applications due to its facile fabrication and excellent oil–water separation properties.

Ultralight, elastic, magnetic and superhydrophobic cellulose nanofibril based aerogel with layer-support structure designed for both excellent oil-water separation and efficient PM2.5 removal

It is unquestionably a great challenge to develop elastic cellulose nanofibril (CNF) based aerogels satisfying both excellent oil-water separation and efficient PM2.5 removal. In this work, the CNF based aerogel with a layer-support structure was design through CNF as the aerogel scaffold and compositing with bamboo activated charcoal (BAC) and Fe3O4 as the functional particles, followed by hydrophobic modification. The resultant aerogel displays ultra-low density (30.12 mg/cm3), good specific surface area (25.38 m2/g), magnetism (9.44 emu/g) and superhydrophobicity (water contact angle (WCA) of 153.8° and slide angle (SA) of 7°). Benefiting from high internal porosity of the layer-support structure, the system shows excellent absorption efficiency (16.79–51.93 g/g) for various oils and filtration efficiency (97.85 ± 1.2%) for PM2.5 with a low pressure drop (58 Pa). As well as it also shows outstanding mechanical properties and able to maintain a high recovery of 75.4% at 50% strain (corresponding 25.29 kPa) due to the flexibility of the “support” structure given by methyltrimethoxysilane (MTMS). Based on its simple preparation and excellent properties, the magnetic and superhydrophobic CNF/Fe3O4@BAC composite aerogel shows great potential in multifaceted separation technique and recycling of natural resources.

Light-Propelled Super-Hydrophobic Sponge Motor and its Application in Oil-Water Separation.

Self-propelled separation materials, that is, motor, are one of the keys to realizing smart oil-water separation. Although three-dimensional sponges such as commercial melamine sponge (MS) exhibit excellent oil-water separation ability, they cannot move by themselves on water. Aiming at solving this problem, a polydimethylsiloxane (PDMS) and molybdenum disulfide (MoS2) modified MS motor (PDMS@MS/MoS2) with an asymmetric multilayer structure was prepared, in which the photothermal layer MoS2 provided the propelling force for the motor under infrared light irradiation, and the middle layer PDMS was used as the superhydrophobic modified agent and adhesive agent between commercial MS and MoS2 powder. PDMS coated MS (PDMS@MS) as the superhydrophobic layer showed good superhydrophobic ability (153.1°) and oil-water separation capacity (52.33 g/g to liquid paraffin). Furthermore, the introduction of MoS2 made the speed of the sponge motor reach 8.27 mm s-1 with a removal quantity of 12.20 g/g for cyclohexane. After recycling 8 times, the contact angle, cyclohexane capturing amount, and average velocity of the motor were 150.3°, 11.40 g/g, and 8.41 mm/s, respectively. Meanwhile, PDMS@MS/MoS2 kept a similar light-propelling velocity (∼8 mm) at different pH values and in simulated seawater, demonstrating that the light-propelling motor possessed a good cycle and practical performance, which provides a possibility for the directional light propulsion of a sponge motor in oil-water separation.

Facile fabrication and application of highly efficient reduced graphene oxide (rGO)-wrapped 3D foam for the removal of organic and inorganic water pollutants.

The pace of water contamination is increasing daily due to expanding industrialisation. Finding a feasible solution for effectively remediating various organic and inorganic pollutants from large water bodies remains challenging. However, a nano-engineered advanced hybrid material could provide a practical solution for the efficient removal of such pollutants. This work has reported the development of a highly efficient and reusable absorbent comprising a porous polyurethane (PU) and reduced graphene oxide (rGO) nanosheets (rGOPU) for the removal of different organic oils (industrial oil, engine oil and mustard oil), dyes (MB, MO, RB, EY and MV) and heavy metals (Pb(II), Cr(VI), Cd(II), Co(II) and As(V)). The structure, morphology and properties of the rGOPU hybrid absorbents were analysed by using Raman spectroscopy, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunner-Emitte-Teller (BET) analysis. The rGOPU possessed both superhydrophobicity and superoleophilicity with water and oil contact angles of about 164° and 0°, respectively. The prepared rGOPU has demonstrated an excellent oil-water separation ability (up to 99%), heavy metals removal efficiency (more than 75%), toxic dye adsorption (more than 55%), excellent recyclability (> 500 times for oils), extraordinary mechanical stability (90% compressible for > 1000 cycles) and high recoverability. This work presents the first demonstration of rGOPU's multifunctional absorbent capacity in large-scale wastewater treatment for effectively removing a wide variety of organic and inorganic contaminants.

Preparation of superhydrophobic sponge and its application in oil-water separation and treatment of polymer-containing wastewater.

At present, the application prospect of superhydrophobic materials in oil-water separation, an-tibacterial and other aspects have attracted more and more attention. However, preparing a simple and low-cost superhydrophobic material remains a challenge. Using acetone as solvent, candle soot, silver/silica nanoparticles and polydimethylsiloxane were uniformly mixed to form a mixed solution, and the superhydrophobic sponge was successfully prepared by spraying method. The results show that the superhydrophobic sponge has high water contact Angle (162°) and excellent oil-water separation efficiency, which can realize effective treatment of polymerized wastewater. In addition, the superhydrophobic sponge showed better antibacterial properties on the surface of Escherichia coli and Staphylococcus aureus. In this work, a simple way to prepare superhydro-phobic oil-water separation material is proposed. The preparation process is green, the material is easy to obtain, and it is expected to be widely used in practical production.

Preparation of underwater superoleophobic SiO2/CS/PVA coating on 304 stainless-steel mesh with excellent oil–water separation performance and stability

Preparation of underwater superoleophobic SiO2/CS/PVA coating on 304 stainless-steel mesh with excellent oil–water separation performance and stability

Dopamine/β-cyclodextrin synergistically modified core-shell MF@ZIF-8 porous membrane for high-efficient filtering of particulate matter (PM) in air and gathering oil in water

Air and water pollution have caused severe environmental concerns with the rapid process of industrialization. Therefore, it is urgent to fabricate advanced membranes for the efficient removal of these pollutants. Herein, we present a low-cost melamine formaldehyde (MF) substrate decorated by ZIF-8 via engineering surface chemistry for the removal of particulate matter (PM) and oil-water separation. β-cyclodextrin (β-CD) and polydopamine (PDA) were assembled on the MF substrates to synergistically tune the surface chemistry and facilitate the dense growth of ZIF-8 in a one-pot synthesis. Benefiting from the macro/nanopores structure of the composite membrane (MF@PDA&β-CD@ZIF-8), it displayed superior filtration properties with high removal efficiencies (94.16±1.70%). More importantly, the hydrophobic property of the composite membrane delivered excellent oil-water separation and oil absorption capacity achieving up to 73 times. The facile synthesis, good stability, and superb specific absorbing properties of composite membrane showed its great potential in air and water treatments.

Swan feather-spired fluorine-free superhydrophobic self-cleaning cotton cloth with strong oil-water separation function

With the increasing demand of oil-water separation, superhydrophobic materials have garnered tremendous research attention due to their excellent oil-water separation efficiency. However, the biological toxicity and poor durability of fluorine-containing compounds in superhydrophobic materials severely restrict their application. In this work, inspired by the superhydrophobic/lipophilic swan feathers, we proposed a two-stage thiol-ene click reaction strategy to fabricate a fluorine-free superhydrophobic and super-lipophilic oil/water separation membrane (Cotton-S-PB-SiO2). Firstly, based on this thiol-ene click reaction, the rubber molecular chain 1,2-polybutadiene (1,2-PB) with low surface energy was coated with cotton fiber through chemical bonds. Subsequently, the coated cotton fiber was employed to establish chemical bonds with silica. The Cotton-S-PB-SiO2 possessed low surface energy and abundant micro-nano structures. Meanwhile, the Cotton-S-PB-SiO2 showed extremely high wettability selectivity to water and oil phases. The flux reached 44,554 L m−2 h−1, and the separation efficiency for immiscible oil/water mixtures was above 99.9 %. More remarkably, the Cotton-S-PB-SiO2 demonstrated excellent anti-fouling and operation stability even under some harsh environments such as strong acid, alkali, salt, etc. The prepared self-cleaning cotton cloth provides insights toward mild, low-cost and high-efficiency oil-water separation.

A facile approach to fabricating fluorine‐free superhydrophobic cotton fabric with excellent oil–water separation performance

AbstractWith the increasing deterioration of environmental and ecology caused by industrial wastewater pollution and petroleum spill accidents, superhydrophobic materials for oil–water separation have attracted considerable attention. Herein, we propose a facile approach to fabricate fluorine‐free superhydrophobic cotton fabric (CF) for oil–water separation after the coverage of chitosan (CS) and titanium dioxide (TiO2) nanoparticles and the subsequent hydrophobization modification by hexadecyltrimethoxysilane (HDTMS). The obtained HDTMS‐TiO2/CS@CF showed superhydrophobicity with a high water contact angle of 160.6° as well as excellent self‐cleaning capability, non‐adhesion capability and surface stability. Moreover, the CF was successfully applied for the separation of various oil–water mixtures. The separation efficiency for trichloromethane‐water mixture reached 95.8%, and still maintained 95.6% after 30 separation cycles. In addition, the CF also possessed superior photocatalytic degradation capability for organic contaminant such as oil red O and the degradation rate was 86.2% under UV irradiation for 180 min. The preparation method in this work is simple, environmentally friendly, low‐cost, and easy to produce on a large scale. The findings conceivably stand out as a new method to fabricate superhydrophobic materials and show great application potential in the fields of oil–water separation and water purification.