Effective Oil-water Separation Research Articles

Nanostructured CFO@SiN-DICP-DHDA as a novel reversible magnetic gelator for the fast and effective oil–water separation: Toluene optimization by CCD approach

In the present work, a novel approach has been described for the synthesis of a durable and recyclable functionalized nanomagnetic gelator namely CoFe2O4@SiO2-NH2-1-5 di isocyanatopentane- di Hexadecylamine (CFO@SiN-DICP-DHDA). The nanocomposite was then used for efficient oil/diesel separation from water, a combination of organic solvents and oil that has rarely applied. CFO@SN-DICP-DHDA was characterized using various techniques, including Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), Vibrating sample magnetometer (VSM), X-ray diffraction (XRD), and inverted microscopic and differential scanning calorimetry (DSC). The successful gelation of the oil leads to facile isolation of the gelator by an external magnetic field. Due to the remarkable oil separation capability, as well as the great mechanical and chemical stability of CFO@SiN-DICP-DHDA, it can tightly bind the organic and inorganic layers on the CoFe2O4 nanoparticles. The gelator demonstrates reproducible application for up to seven consecutive cycles without a significant reduction in performance. These outstanding results will pave the way for the removal of oil stains from water and the development of functional super magnetic gel materials. The initial maximum toluene uptake of ∼58 % was boosted to approximately ∼97.65 % through optimization using the central composite design (CCD) approach.

Dual-bioinspired fabrication of Janus Micro/nano PDA-PTFE/TiO2 membrane for efficient oil-water separation

Oily wastewater poses a severe threat to the environment and human health, and its disposition is a worldwide urgency. Rencently, Janus membranes has provided excellent selectivity for oil/water separation due to thin layers of different wettability on opposite sides. However, the fabrication of Janus asymmetric multilayer with simple syntheses and excellent stability has been proved challenging. Herein, a Janus polydopamine-polytetrafluoroethylene/titanium dioxide (PDA-PTFE/TiO2) membranes were inspired by dual-bionic strategy (lotus leaf and mussel) and constructed by centrifugal spinning technology. The membranes showed significant separation efficiency for both water–oil mixtures and emulsions above 99%. Most notably, the separation efficiency of the membranes are still maintained above 98.5% after 24 h immersion in the corrosive solutio. Meanwhile, the nanofiber membrane has outstanding reusability, acid/alkali resistance, and mechanical stability. Therefore, the dual-bioinspired Janus micro/nano PTFE/TiO2 membrane suggests a promising potential application for a sustainable and effective oil–water separation membrane in the future.

Superhydrophobic TiN-Coated Cotton Fabrics with Nanoscale Roughness and Photothermal Self-Healing Properties for Effective Oil–Water Separation

Superhydrophobic TiN-Coated Cotton Fabrics with Nanoscale Roughness and Photothermal Self-Healing Properties for Effective Oil–Water Separation

Facile fabrication of hydrophobic covalent organic framework decorated melamine sponge for efficient separation of immiscible oil-water mixture and water-in-oil emulsion

Frequent oil spills and oily sewage have caused serious environmental problems. Sponges have attracted great attention in oil-water separation due to their low cost and high porosity, but it still remains challenge to hydrophobic modification of sponge in facile and scalable manner. Here is reported a facile fabrication of porous and hydrophobic sponge composite (MS@COF) with effective oil-water separation by in-situ growth of hydrophobic TFB-BD(Me)2 COF on the surface of melamine sponge. Combining the porous structure of the sponge and hydrophobicity of COF, the composite can separate oil-water mixture and water-in-oil emulsions in a fast way. The prepared MS@COF showed oil adsorption capacity up to 160 g g-1. In addition, continuous separation of oil-water mixture was demonstrated using a peristaltic pump with a separation rate of 50 mL min-1. More importantly, the composite could separate surfactant-stabilized water-in-oil emulsions with separation efficiency of 98.8%. The oil-water mixture and oil-water emulsion separation ability of the composite persisted after 50 separation cycles thereby demonstrating good recyclability. The composite also showed good chemical stability, mechanical and flame retardancy. This work introduces a new approach for the synthesis of hydrophobic sponge decorated with COF nanoparticles for oily wastewater treatment and organic pollutant removal on water surfaces.

Polyacrylonitrile nanofibrous membrane composited with zeolite imidazole skeleton-8 and silver nanoclusters for efficient antibacterial and emulsion separation

Oily wastewater discharged by industrial development is an important factor causing water pollution. Membrane separation technology has the advantages of low cost, simple operation, and high efficiency in the treatment of oily wastewater. However, membrane materials are easily eroded by microorganisms during long-term storage or use, thereby resulting in reduced separation efficiency. Herein, a zeolite imidazole skeleton-8@silver nanocluster composite polyacrylonitrile (ZIF-8@AgNCs/PAN) nanofibrous membrane was fabricated by electrospinning and in situ growth technology. The surface chemistry, morphology, and wettability of the composite membranes were characterized. The carboxyl groups on the surface of hydrolyzed PAN nanofibers, which can be complexed with zinc ions (Zn2+), are utilized as growth sites for porous metal organic frameworks (ZIF-8). Meanwhile, AgNCs are loaded into ZIF-8 to achieve stable hybridization of ZIF-8@AgNCs and nanofibers. The loading quantity of ZIF-8@AgNCs, which can dominantly affect the surface roughness and the porosity of the membranes, is regulated by the feeding amount of AgNCs. The ZIF-8@AgNCs/PAN membrane achieves effective oil-water separation with high separation efficiency toward petroleum ether-in-water emulsion (98.6%) and permeability (62 456 ± 1343 Lm-2 h-1 bar-1). Furthermore, the ZIF-8@AgNCs/PAN membrane possesses high antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), which is beneficial for the long-term storage and use of the membrane.

Bio-based phytic acid@polyurushiol‑titanium complex coated cotton fabrics with durable flame retardancy for oil-water separation

Bio-based hydrophobic coating modified cotton fabrics with durable flame retardancy are of high interest in the application of oil-water separation for not only avoiding the use of hazardous substances but also improving the fire safety during use. Herein, phytic acid@Polyurushiol‑titanium complex coated cotton fabric was developed using the facile dip-coating method involving the sequential immersion in the solution of poly(ethyleneimine), phytic acid, titanium oxide, and urushiol. The underlying coating accommodated abundance of phytic acid, which imparted excellent flame retardancy to cotton fabric, and the top coating composed of the polyurushiol‑titanium complex endowed cotton fabric with high hydrophobicity that the water contact angle (WCA) was up to 149.8°. The hydrophobicity also guaranteed effective protection of the underlying phytic acid against chemical solvents and abrasion. Besides, the hydrophobic coating allowed cotton fabric for good self-cleaning and effective oil-water separation. Therefore, the preparation of phytic acid@polyurushiol‑titanium complex coated cotton fabric offers a promising approach to construct durable biomass-coated cellulose-based fabric with multifunctionality.

Green Fabrication of Underwater Superoleophobic Biopolymeric Nanofibrous Membranes for Effective Oil–Water Separation

Green Fabrication of Underwater Superoleophobic Biopolymeric Nanofibrous Membranes for Effective Oil–Water Separation

Cubic MOF coated stainless steel mesh with underwater superoleophobicity for highly efficient oil/water separation

A novel superhydrophilic and underwater superoleophobic material (MOF-5/PDA/SSM) with high flux, outstanding oil/water separation performance and durability was prepared. The stainless steel mesh (SSM) was modified by MOF-5 crystals and PDA. The introduction of MOF-5 can improve the hydrophilicity of SSM and achieve high water flux at the same time. PDA is a substance with strong adhesion which can be used as an effective bonding intermediate. The preparation strategy includes the self-polymerization of dopamine and the deposition of cubic clusters on SSM via hydrothermal reaction. The MOF-5 particles on the mesh are cubic hexahedral crystal with a uniform size diameter, which can trap water in the rough microstructure, forming a strong hydration barrier layer or composite water-solid interface on its surface, hindering the penetration of oil. The super-hydrophilicity and underwater superoleophobicity of the modified meshes were introduced by pre-wetting surface. The FTIR, XRD, XPS and SEM characterizations demonstrated that the successfully growth of MOF-5 and a rough structure was obtained on the mesh. The special wetting and the robustness of the fabricated mesh led to the outstanding separation efficiency (up to 99.5%), excellent recyclability (about 20 cycles) and high water flux (53.9 k L m−2 h−1). The mesh also showed remarked water flux and various oil/water mixtures separation performance. Particularly, the successfully prepared materials were found to be significant stable under various physical and chemical extremes environments, including maintain UWOCA>150 under acid/alkali media, marvelous performance after 120 min of continuous separation and high anti-oil intrusion pressure. The combination of metal organic framework and stainless steel mesh may provide a candidate application to effective oil-water separation.

Facile preparation of superhydrophilic and underwater superoleophobic stainless steel mesh for oil–water separation

Effective oil–water separation is necessary to cope with frequent oil spill accidents, which pose huge risks to the marine ecosystem. Among existing oil–water separation methods, gravitational filtration is the most efficient. When super-wetting materials are used for gravitational filtration, they have the merit of high efficiency but they still have the disadvantages of high price, low eco-friendliness, and complex procedures. To overcome those problems, we fabricated a stainless steel mesh by a one-step method via an annealing process. The annealed mesh achieved both superhydrophilicity and superoleophilicity. For oil–water separation, the annealed mesh, which was pre-wetted by water, demonstrated underwater superoleophobicity. Thus, this study confirmed that the proposed system can separate various oily mixtures with high efficiency (>99 %) and it exhibits underwater anti-oil-fouling.

Surface engineering of a superamphiphilic, self-growing fibrous Janus membrane prepared from mycelium

Fully biobased and self-growing Janus membrane without additives or blending. Interface design enabling mycelium growth and facile harvesting. Exploitation of hydrophobins for Janus membranes. Membrane contactor was leveraged to grow mycelium.

Bioinspired Composite Hydrogel‐Coated Stainless Steel Screen for Efficient and Stable Gravity‐Driven Oil–Water Separation

The reasonable and efficient treatment of oily wastewater has attracted wide attention. Herein, a composite hydrogel‐modified filter screen, inspired by fish scales and marine mussels, is prepared via layer‐by‐layer modification to separate oil–water mixture even in harsh environments. First, a stainless steel filter screen is coated by a layer of silicon dioxide (SiO2) microspheres by the vapor deposition of polydimethylsiloxane. Then, a SiO2@polydopamine‐polyacrylamide composite hydrogel (SiO2@P–PGel)‐modified screen is prepared by dipping the screen into a prepolymer solution. Due to the special wettability and micronanostructures, the stable and high efficient water permeation in the air and oil repellency in water are achieved by the screen. A very effective oil–water separation rate of over 99% can be achieved for various types of oil–water mixtures. The separation efficiency and water flux remain stable even after 70 cycles. Another significant feature of the innovative screen is that it displays excellent underwater superoleophobicity in very salty, acidic, and alkaline solutions, suggesting that the screen has excellent oil–water separation performance and stability, even in corrosive aqueous media. This innovative screen is a potentially attractive candidate for the treatment and recovery of oily wastewater due to its high efficiency and stability.

Green and rapid fabrication of superhydrophilic and underwater superoleophobic coatings for super anti-crude oil fouling and crude oil-water separation

The development of surfaces with super anti-crude oil-fouling behavior and crude oil-water separation properties is still a global challenge owing to the high viscosity of crude oil. Herein, superhydrophilic and underwater superoleophobic surfaces were successfully prepared by a simple, green and environmentally friendly one-step dip coating method. In the whole process, microcrystalline cellulose with hydrophilic hydroxyl functional groups was introduced into the coating with the help of inorganic adhesives, water was the only solvent, and no other organic solvents or surface modifiers was added. Besides being highly resistant to low viscosity oils and achieving effective oil-water separation (more than 98.3% separation efficiency after 30 cycles), the surface effectively resisted crude oil adhesion and achieved high viscosity crude oil-water separation. In addition, the underwater oil contact angle can still reach 147.5° and 152.5° after 20 cycles of sandpaper friction tests and 50 cycles of finger pressure tests, respectively, which indicates excellent durability. Furthermore, the method can achieve excellent superhydrophilicity and underwater superoleophobicity on varieties of substrates (such as copper foil, aluminum sheet and glass), showing very extensive applicability. It is expected that such fabrication strategy can provide a low cost, green and environmentally friendly approach to construct a series of superhydrophilic and underwater superoleophobic surfaces to achieve super anti-crude oil-fouling and (crude) oil-water separation.

A bio-inspired green method to fabricate pH-responsive sponge with switchable surface wettability for multitasking and effective oil-water separation

Smart oil-water separation materials with stimuli-responsive wettability surfaces have attracted wide attention. In this paper, a novel, simple and low-cost method is developed to prepare a pH-responsive melamine sponge (MS) with switchable wettability. This approach involves the hydrophobic modification of hexadecyltrimethoxysilane (HDTMS) on the MS surface modified by polydopamine (PDA) and the Michael addition reaction and Schiff base reaction between 12-aminododecanoic acid (NH2(CH2)11COOH) and PDA. Hydrophobic/oleophilic HDTMS and pH-triggered NH2(CH2)11COOH enable the functionalized sponge to repeatedly switch between the two extreme wettability under different pH environments. Benefiting from the excellent 3D porous surface structure and smart wettability, the as-prepared sponge can be applied in the on-demand separation of various oil-water mixtures by adsorption or filtration with a separation efficiency over 98.5% and high absorption capacity of 72.7–161.3 g·g−1. With the assistance of pump-driven, continuous adsorption separation can be achieved in two cases by utilizing the wettability transformation. Moreover, in an alkaline solution, the sponge can quickly release most of the absorbed oil, showing a controllable desorption process. This smart wettability material with simple preparation and green has application potential in controllable oil-water separation and on-demand oil-spills treatment.

Electrospun rough PVDF nanofibrous membranes via introducing fluorinated SiO2 for efficient oil-water emulsions coalescence separation

Oily wastewater pollution is grievous and challenging all over the world and how to effectively and economically remove emulsified oils from wastewater is a tough problem. A novel rough polyvinylidene fluoride (PVDF)-F-SiO2 nanofibrous membrane as the polyester (PET) substrate was fabricated by the facile one-step electrospinning technology with introducing fluorinated SiO2 nanoparticles for effective oil-water coalescence separation. Fluorinated SiO2 could increase the microscopic roughness, leading to a higher hydrophobicity. The obtained PVDF-F-SiO2 nanofibrous membrane had a high under oil contact angle (UOCA) of 122.3° indicating a high under-water hydrophobicity. The prepared membrane could perform the high oil-water emulsion coalescence separation efficiency with 99.2 % for treating surfactant-free hexadecane-in-water emulsions after 5 cycles. The PVDF-F-SiO2 nanofibrous membrane demonstrated high separation efficiencies under different flow rates, initial oil concentrations, and oil types in emulsified oil-water systems. More importantly, the SDBS-surfactant-stabilized hexadecane-in-water emulsion could be separated with efficiencies above 82.0 % after 5 cycles, which showed promising potential in treating oily wastewater.

Facile fabrication of superhydrophobic–superoleophilic ZnCo2O4 nickel foam for highly efficient oil/water separation

AbstractIn recent years, the fabrication of hydrophobic materials and their excellent applications in oil spill cleanup has attracted widespread attention. Herein, we report the rapid and straightforward preparation of ZnCo2O4 nickel foam by hydrothermal synthesis. The prepared sample surfaces possess excellent superlipophilicity and superhydrophobicity after modification by stearic acid, so it can efficiently absorb light and heavy oil in water, and the absorption efficiency is over 99%. Besides, the unmodified ZnCo2O4 nickel foam could be subjected to effective oil–water separation at standard temperature and pressure, and its separation efficiency can be more than 97.4%. After 20 continuous filtration cycles, it can maintain stable high separation efficiency and even work under harsh environmental conditions, like acid, alkali, salt solution, high and low temperature, and ultraviolet radiation. Compared with other methods of manufacturing hydrophobic materials, this method is facile, lower cost, environmentally durable, and highly efficient. Therefore, the as‐prepared ZnCo2O4 nickel foam has good application value in treating oily wastewater.

Ultra-Light GO@KGM Aerogels for Oil-Water Separation Based on CVD Modification.

Nowadays, oil pollution of water caused by illegal discharges or accidental events occurs frequently, and the waste of resources and environmental pollution cannot be ignored, so effective oil–water separation methods are needed to cope with such incidents. To solve these problems, this paper investigated an aerogel made from a plant polysaccharide, konjac glucomannan (KGM), supplemented with graphene oxide (GO), to improve the mechanical properties. Finally, a hydrophobic layer was attached to the surface and interior of the aerogel via chemical vapor deposition to improve its selectivity toward oil. Through a series of characterization methods such as infrared, X-ray photoelectron spectroscopy, and X-ray diffraction, it was demonstrated that KGM and GO were successfully cross-linked, resulting in excellent mechanical properties and directional absorption properties on oil. This composite polysaccharide aerogel could absorb oil 48 times its own weight. In addition, due to its strong mechanical properties, the gel can be reused many times, and the maximum recovery rate can be maintained at 96% after 10 cycles. Furthermore, the absorption of oil from water was conducted in a continuous mode, demonstrating the diversity of application scenarios. Generally, the results observed in this work have shown that the KGM aerogels have great potential for applications in oil–water separation.

Hydrodynamics and morphologies of droplets coalescence on fiber

AbstractFiber coalescence is an effective oil–water separation technology. In this article, the micro‐coalescence process of droplets on fiber was studied through high‐speed camera technology, and the hydrodynamics and morphology evolution in the process of droplet‐fiber coalescence were explored and compared with non‐fiber system. The results show that the change of the droplet surface morphology is local at the initial stage of the coalescence process. The droplet morphology changes obviously near the neck. The growth rate of the liquid bridge and the propagation speed of capillary wave in droplet‐fiber system are higher than those in non‐fiber system. At 0.8 ms, the capillary waves' polar angle difference between the two conditions reaches 10.44°. There is an obvious periodicity and damping attenuation mechanism in the oscillation process. In the droplet‐fiber system, the oscillation process attenuates faster and the average oscillation period is shorter. The droplet relaxes to a stable state more quickly.

Facile one-step fabrication of superhydrophobic melamine sponges by poly(phenol-amine) modification method for effective oil–water separation

Although polydopamine (PDA)-related modification is widely studied in the fabrication of superhydrophobic sponges, the high cost of dopamine limits its widespread application. To imitate PDA modification, a low-cost and facile one-step poly(phenol-amine) modification was performed on melamine sponges in this study. Low-cost catechol and diethylenetriamine (DETA) were used as the monomers, and n-dodecanethiol was used as an additive in the one-step modification. The results confirmed that the poly(phenol-amine) aggregations were successfully anchored on the sponge skeleton surface and that the aggregations were formed via the Schiff base reaction and the Michael addition reaction. Furthermore, the as-prepared sponges still showed excellent mechanical properties after modification. Additionally, the optimally modified sponge (MS-0.5) exhibited superhydrophobic properties with a contact angle value above 150° under various environments, high oil-absorption capacity for various oils and organic solvents, high continuous oil–water separation performance with efficiency greater than 98.8% in 30 cycles, outstanding demulsification performance with 99.52% toward oil-in-water emulsion, and excellent recoverability and long-term stability. Thus, this work provides a feasible facile one-step modification method that can be used in place of PDA-related modification.

ZnO/WO3.H2O micro-nanostructures coated mesh for efficient separation of oil-water mixture

In this work, we report the fabrication of superhydrophilic-underwater superoleophobic ZnO/WO3.H2O coated stainless steel mesh for the effective oil-water separation. X-ray diffraction studies confirm the occurrence of hexagonal wurtzite and orthorhombic phase of ZnO and WO3.H2O respectively in the ZnO/WO3.H2O coated mesh. The superhydrophilic-underwater superoleophobic nature of ZnO/WO3.H2O covered mesh is attributed to the innate hydrophilicity and surface roughness of WO3.H2O, which is again enhanced by the inclusion of ZnO. The oil-water separation efficiency of ZnO/WO3.H2O covered stainless steel mesh was over 98% for various oil-water mixtures. The coated mesh maintains high efficiency of separation even after 10 cycles of operation. Moreover, the as-deposited meshes demonstrated good separation ability for the emulsified oil droplets larger than its pore size. The excellent abrasion-resistant ability of ZnO/WO3.H2O coated mesh indicate its excellent mechanical stability. In addition, the high intrusion pressure of ZnO/WO3.H2O coated mesh favors the separation of oil-water mixture in large volumes. Furthermore, the photocatalytic activity of the coated mesh could degrade the organic pollutants present in the oil-water mixture. The proposed novel strategy in designing a multifunctional surface paves the way for the treatment of oleaginous water for environmental remediation.

Recent Developments and Advancements in Graphene-Based Technologies for Oil Spill Cleanup and Oil-Water Separation Processes.

The vast demand for petroleum industry products led to the increased production of oily wastewaters and has led to many possible separation technologies. In addition to production-related oily wastewater, direct oil spills are associated with detrimental effects on the local ecosystems. Accordingly, this review paper aims to tackle the oil spill cleanup issue as well as water separation by providing a wide range of graphene-based technologies. These include graphene-based membranes; graphene sponges; graphene-decorated meshes; graphene hydrogels; graphene aerogels; graphene foam; and graphene-coated cotton. Sponges and aerogels modified by graphene and reduced graphene oxide demonstrated effective oil water separation owing to their superhydrophobic/superoleophilic properties. In addition, oil particles are intercepted while allowing water molecules to penetrate the graphene-oxide-coated metal meshes and membranes thanks to their superhydrophilic/underwater superoleophobic properties. Finally, we offer future perspectives on oil water separation that are hindering the advancements of such technologies and their large-scale applications.