Oil-water Emulsion Separation Research Articles

Pickering Emulsion-Templated Nanocomposite Membranes for Excellent Demulsification and Oil-Water Separation.

A worldwide steady increase in oily wastewater, due to oil spillage and various industrial discharges, requires immediate efforts toward development of an effective strategy and materials to preserve the natural water bodies. Designing a superwettable fibrous membrane of robust structure and anti-fouling property for efficient separation of oil-water mixtures and emulsions is therefore highly demanding. The electrospun fibrous membrane, which possesses porosity and flexibility and properties including superwettability and tunable functionality, can be considered as apposite materials for this cause. In this approach, we combined two strategies, viz., Pickering emulsion and near gel resin (nGR) emulsion electrospinning together to produce a fibrous nanocomposite membrane for efficient oil-water separation and demulsification. nGR Pickering emulsions were stabilized using hydrophilic SiO2 nanoparticles and successfully optimized for fabricating the crosslinked core sheath-structured fibrous membrane. The prepared membrane provided twofold functionality due to the core sheath structure of the fibers. The crosslinked polystyrene core offered high oil adsorption capacity, whereas SiO2-functionalized crosslinked polyvinyl alcohol sheath provided a rough, superhydrophilic surface with underwater oleophobic behavior to the membrane. The optimized SiO2-Pickering emulsion-templated nanocomposite membrane demonstrated excellent underwater anti-oil adhesion behavior (UWOCA ∼148°) with efficient oil-water separation capacity of more than 99% and separation flux up to 3346 ± 91 L m-2 h-1. The membrane was evaluated against various oil-water emulsions and found to have a superior separation efficiency. Moreover, excellent anti-oil adhesion property provided the intact membrane, where consistent separation performance was achieved up to 10 separation cycles without any loss. The membrane was used for separation of hot oil-water emulsions and showed no structural disintegration or loss in separation performance when exposed to elevated temperatures. The developed nanocomposite membranes could efficiently be used for separation and demulsification, and their applications can be explored in various other fields including selective sorption, catalysis, and storage in future.

Facile preparation of hydrophilic PVDF membrane via tea polyphenols modification for efficient oil-water emulsion separation

Facile preparation of hydrophilic membranes is essential for achieving efficient separation of oil-water emulsion. In this paper, a hydrophilic PVDF@TP membrane was prepared by very simple direct modification using green tea (The main extract is tea polyphenols, TP). The PVDF@TP membrane exhibits good hydrophobicity in air and underwater superoleophilicity. The oil-water separation potential of this membrane was studied using several model oil-in-water emulsions. The resulting membrane exhibitd high separation efficiency (above 99 %) and separation fluxes (955–1672 L m−2 h−1 bar−1) for various oil-in-water emulsions. Additionally, separation efficiency of PVDF@TP membrane was still above 98 % even after 10 times continuous separation, demonstrating its good antifouling ability and stability. In addition, bending, ultrasonic and stirring treatments showed that the membrane has good mechanical durability. In view of the advantages of facile preparation, economy and high-performance, the hydrophilic PVDF@TP membrane has a very broad application potential in industrial oily wastewater and oil spill treatment.

Rapid Approach to Synthesizing a Tannic Acid (TA)-3-Aminopropyltrietoxysilane (APTES) Coating for Efficient Oil-Water Emulsion Separation.

Plant polyphenol-inspired surface modification of membranes is helpful for oil-water separation. However, the preparation of this coating is time-consuming. Herein, we introduce a rapid synthesis of the TA-APTES coating by the addition of sodium periodate (SP). The surface chemical composition and morphology of the resultant TA-APTES hybrid coatings were characterized using SEM, ATR-FTIR, and XPS. The hydrophilicity and membrane performance were investigated by the water contact angle, pure water permeability, and oil rejection for an isooctane-in-water emulsion. The experimental findings revealed that the optimal microfiltration (MF) membrane (MF-TA-APTES-SP-0.05) displayed exceptional hydrophilicity and water permeability (9558 L m-2 h-1 bar-1). The membrane realized highly efficient separation with a permeability (4117 L m-2 h-1 bar-1) and rejection of oils (>99%). Furthermore, it possessed outstanding chemical stability and maintained underwater superoleophobicity even after exposure to harsh conditions. This simple and rapid strategy of developing hydrophilic coatings as a modifier for the poly(vinylidene fluoride) membranes has potential applications in oil-water separation and wastewater treatment.

Engineering a superwetting membrane with spider-web structured carboxymethyl cellulose gel layer for efficient oil-water separation based on biomimetic concept

Superhydrophilic and underwater superoleophobic membranes have recently attracted significant interest as materials for effective oil-water emulsion separation.In this work, a superwetting membrane with a spider web structured gel layer was designed for efficient oil-water separation. Biomaterial, carboxymethyl cellulose (CMC), was used as the raw material, a spider web structured gel layer was constructed on the PVDF membrane surface by heat-treatment and chemical cross-linking. The hydrophilic gel layer imparted excellent superhydrophilic and underwater superoleophobic properties to the membrane, while the special spider web structure improved the membrane mechanical stability. The fabricated membrane exhibited superhydrophilicity and underwater superoleophobicity. Among different CMC concentration-modified membranes, the M-0.5 membrane containing 0.5 wt% CMC exhibited a flux of 612 L·m−2 h−1 during dichloromethane oil-water emulsion separation, which was 4.2-fold higher than that of the pristine PVDF membrane, while the membrane showed efficient oil-water separation capacity. Additionally, the water flux recovery reached as high as 93.3 %, and oil rejection attained 99.1 %. Meanwhile, the spiderweb-structured gel layer on the membrane surface displayed good mechanical stability. In summary, this novel membrane-modification method, inspired by the spider web structure, was simple, cost effective and environmentally friendly, thereby making it promising for future preparation of highly efficient oil-water emulsion separation membranes.

Separation of oil-water emulsions by a novel packed bed electrocoagulation (EC) process using anode from recycled aluminum beverage cans

Electrocoagulation (EC) is an emerging technology for the elimination of oil and COD content from oily wastewaters. However, higher operating costs and electrode passivation are pressing challenges for its wide speared application. To overcome this setback, the present work has attempted to develop a new and inexpensive electrode using recycled aluminum (Al) beverage cans for the treatment of oily wastewater by electrocoagulation (EC) technology. It could be an alternative to conventional plate or tube electrodes in the EC process, it is the first contribution into the literature. In current work, recycled Al beverage cans filled with steel wool was used as anode, and commercial stainless-steel mesh (304) with cylindrical shape was used as cathode. The main EC performance measure was COD removal efficiency, impacts of significant process parameters in the EC process (such as operating voltage, electrocoagulation time, stirring rate, and NaCl concentration) on the effectiveness of EC process were investigated by using response surface methodology (RSM) based Box-Behnken Design (BBD) model. The RSM analysis results demonstrated that the highest COD removal rate of 93.53% was achieved under optimal conditions of operating voltage (15 V), electrocoagulation time (10 min), stirring rate (250 rpm), and NaCl concentration (1 g/L). In addition, energy consumption analysis was performed, an electrical energy efficiency of 0.160 kWh/kg COD was achieved. Afterward, ATR-FTIR spectroscopy, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and XRD analysis were performed under optimal conditions to characterize anode, and generated sludge during the EC process. Collectively, the findings in this study paves the way toward the development of sustainable EC technology for separation of emulsified oil-water mixtures, which gives the importance of the circular economy and sustainable management of industrial wastewaters.

Effect of cellulose nanocrystals on bacterial cellulose hydrogel for oil-water separation

Cellulose hydrogels reveal potential application for oil-water emulsion separation. However, they still suffer from lower flux, resulting from their stable hydration layers. In this work, bacterial cellulose (BC)/cellulose nanocrystals (CNC) hydrogels were prepared via the immersion method. The hydrogels also showed good superhydrophilicity/underwater-superoleophobicity. They can separate oil-in-water and water-in-oil emulsions with separation efficiency > 97.6 %. More importantly, the addition of CNC improved the crystallinity of BC hydrogels and decreased the accessibility to water molecules, which increased the water flux of hydrogels. This work provides a feasible strategy to enhance the separation flowrate for oil-water emulsions.

Preparation of an environmentally friendly demulsifier using waste rice husk as raw materials for oil–water emulsion separation

Demulsification of crude oil emulsions still face many difficulties in the petroleum industry. Therefore, it is very important to develop innovative materials to achieve the effective separation of oil–water emulsions. In this work, an environmentally friendly RHC-0.5 demulsifier was prepared via a simple one-step hydrothermal route using rice husk (RH) as raw materials. It was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectrometer and thermogravimetric analysis. The possible breaking mechanism was analyzed by particle size analysis, Zeta potential, interfacial activity, interfacial tension, self-assemble of interfacial film and microscopic analysis. The influence of some important factors such as dosage, temperature, standing time and salinity on the demulsifying efficiency (DP) was explored through bottle tests. The optimal DP of 95.01 % could be obtain with 300 mg/L of RHC-0.5 at 70 °C for 10 min. Meanwhile, RHC-0.5 had a good salt tolerance even at the salinity of 40000 mg /L. In addition, its DP was compared with that of commercial demulsifiers such as SP169, CH-66 and AR-32. This work not only can promote the efficient utilization of biological waste (RH), but also provides an insight into the exploration of new demulsifying materials with excellent performance.

Silica nanoparticle modified polysulfone/polypropylene membrane for separation of oil-water emulsions

Oil spillage and industrial discharge of oily wastewater threaten the health of the human beings and the environmental life. To perform oil cleaning from the water bodies, several physicochemical methods have been employed. However, these methods experience various challenges hindering their absolute usage. To curb these problems, smart materials are fabricated, thus gravitating interests towards research. The current study provides a comprehensive outline for preparation and evaluation of hybrid membranes towards separation of oil from water. The membranes were prepared via a facile phase separation process using polysulfone/polypropylene casting solution. To improve oil filtration of these membranes, perfluorooctyltriethoxysilane-modified silica nanoparticles (FOTS-SiO2NPs) were embedded into the casting solution. Based on contact angle (CA) and membrane pore sizes, hydrophobic-oleophilic and porous membranes were synthesized. Also, the liquid pressure (LEP) correlated with membrane CA and reduced pore sizes upon membrane modification. Interestingly, incorporation of the FOTS-SiO2NPs improved membrane oleophilicity, thus representing high performing membrane during oil-water separation. Respective oil flux and separation efficiency of 84.9 L/h·m2 and 83.4% were obtained. These results demonstrate a one-step success towards efficient oil cleaning from the polluted water sources.

Nano-modification of carboxylated polyether for enhanced room temperature demulsification of oil-water emulsions: Synthesis, performance and mechanisms

Oil-water emulsions separation is frequently required considering the production and environmental issues. Herein, a nano-modification strategy has been proposed for carboxylated poly(propylene oxide)-poly(ethylene oxide) block polyether (mANP) using epoxy-functionalized magnetic nanoparticles (Fe3O4@SiO2-GPTMS), achieving the construction of a highly efficient demulsifier (M-mANP). Bottle tests showed that M-mANP could separate over 98.5% of water from the asphaltene-stabilized water-in-oil (W/O) emulsion at mANP concentration of 150 ppm within 2 min at room temperature. The demulsification efficiency for crude oil-in-water emulsion was nearly 100%. According to interfacial tension and wettability tests, the nano-modification endows M-mANP with good amphiphilicity and high interfacial activity, which enables M-mANP to rapidly adsorb at the oil-water interface. Molecular dynamics simulation shows that abundant oxygen-containing groups (hydroxyl, ether bond, ester and carboxyl groups, Fe−O and Si−O bond) in M-mANP could strengthen the interaction with water, facilitating the replacement of asphaltene molecules at interfacial film. Observation of demulsification process by microscope reveals that the nano-size promotes M-mANP to bridge small dispersed droplets, enhancing the flocculation and coalescence of droplets. The nano-modified carboxylated polyether with outstanding demulsification ability shows a promising application for the treatment of different oil-water emulsions.

Bioinspired superwettability: From interfacial materials to chemistry

<p indent="0mm">Interfacial wettability is one of the fundamental problems in material science. The research on wettability regulation is of great significance in exploring new knowledge and creating new applications. Learning from nature, Prof. Jiang has summarized three basic principles of superwettability: (1) The static wetting is determined by the cooperative effect of nanostructure and surface energy; (2) the transition point of the superlyophilicity and superlyophobicity on the nanostructure is the lyophilicity-lyophobicity limitation; (3) the direction of liquid transport is regulated by chemical composition gradient, rough gradient, curvature gradient, etc. Based on these principles, he further extended the superwettability interfacial material systems to interfacial chemistry. He established a superwetting interfacial material system including 64 combinations, and expanded to various liquid systems with different pressure and temperature ranges, leading and promoting the global development of this field. In this paper, we will introduce the design of superwetting interface and the new law of liquid/gas/solid three-phase interfacial wettability. Based upon the new law of three-phase interfacial wettability, we state the application of water-oil separation, pesticide spraying, electrochemical sensors, and photoelectric material patterning. And the recent research and application prospect in the field of quantum-confined superfluid are discussed. In the part of water-oil separation, focusing on the key issue of constructing membrane materials with both fine pore structure and super-wetting properties, without changing the traditional separation membrane preparation process, the micro-nano multi-level structure of the membrane surface is constructed through structure-induced tuning, and the surface is chemically modified. Synergistic action is used to realize the regulation of membrane transport behavior of water droplets or oil droplets, and a series of novel structural membrane separation materials have been successfully prepared, realizing high-precision and high-throughput separation of oil-water emulsions under low driving pressure. In-depth research on the relationship between the molecular structure of surfactants and the kinetic behavior and thermodynamic state of droplets on specially wetted surfaces has led to the discovery of a very cheap anionic surfactant (sulfosuccinic acid) capable of forming vesicles. Sodium dioctyl ester (AOT) can inhibit the ejection and sputtering of pesticide droplets on the surface of superhydrophobic plants at a very low concentration (3/1000 mass concentration). Aiming at the historical problem of “deficient oxygen” during the use of electrochemical enzyme sensors, we proposed and constructed an oxygen-enriched enzyme electrode with solid/liquid/gas three-phase coexistence. The three-phase electrode will greatly improve the detection performance of existing sensors, has extremely broad application prospects in future disease monitoring, and provides a new design idea for the development of high-efficiency enzyme sensors. We exploit the principle of “liquid bridge confinement assembly” by inducing site-specific condensation and crystallization of small organic molecules by exploiting asymmetric wettability interfaces, fabricating one-dimensional arrays of organic polymer semiconductors by exploiting highly adhesive three-phase interfaces, and exploiting superwetting The micro-nano interface controls the three-dimensional dewetting process and realizes the preparation of highly oriented one-dimensional single-crystal nanowires. These three methods are the key issues to realize one-dimensional micro-nano materials from material preparation to device application. Since 2008, we have successfully achieved the fabrication of smart nanopores that mimic ion channels in biomembranes. This channel has properties similar to biological ion channel switching, selection and rectification. Furthermore, by imitating the mechanism of energy conversion in living systems, the design of energy conversion systems driven by chemical potential gradients based on biomimetic nanopores and the design of nanopore-based sensing devices are realized. Since 2018, we focused on dynamic superwetting. The concept of ionic/molecular superfluid is proposed, which promotes the understanding of the realization of ultra-low energy conversion and information transmission in biological systems and provides new ideas for the study of ultra-low energy chemical synthesis in biological systems. It is believed that future research on ionic/molecular superfluidity will promote the development of neuroscience and brain science, develop quantum ion technology, develop future chemical and chemical reactors with high flux, high selectivity and low energy consumption, and will produce a series of disruptive technologies.

Oil–Water Emulsion Separation and Cleaning Performance Study by Cross-Flow Membrane Filtration

Oil–Water Emulsion Separation and Cleaning Performance Study by Cross-Flow Membrane Filtration

Blending Electrostatic Spinning Fabrication of Superhydrophilic/Underwater Superoleophobic Polysulfonamide/Polyvinylpyrrolidone Nanofibrous Membranes for Efficient Oil-Water Emulsion Separation.

The scarcity of water resources has led to widespread interest in the treatment of oily wastewater. This study prepared a novel superhydrophilic/underwater superoleophobic polysulfonamide (PSA)/polyvinylpyrrolidone (PVP) nanofibrous membrane through electrostatic spinning for efficient oil-water emulsion separation. The surface morphology, fiber diameter distribution, wettability properties, and oil-water emulsion separation performance of the membranes were investigated. Results showed that the addition of PVP increases the diameter of the fibers, which led to a loose, large, porous structure and improved the permeability of the membranes. A high pure-water flux of 2057 L·m-2·h-1 was obtained for membranes with PVP addition of 3 wt%, providing an 835% increase in pure-water flux compared with a pure PSA nanofibrous membrane (220 L·m-2·h-1). For n-hexane-in-water emulsions, the optimum membrane obtained a high separation efficiency of 99.7%, in which flux was 1.5 times greater than that of the pure PSA nanofibrous membrane. Moreover, the optimum membrane exhibited good recycling stability and solvent resistance. The as-prepared PSA/PVP nanofibrous membrane displayed high permeability, an outstanding rejection rate, resistance to organic solvents, and reusability for oil-water separation, providing great potential in practical membrane separation applications.

Modification of Cellulose Acetate Membranes by Unipolar Corona Discharge for Separation of Oil-Water Emulsion

The separation of water-oil emulsion with cellulose membranes modified with a unipolar corona discharge at voltage of 5–25 kV and time of 1–5 min was investigated. The results of the X-ray diffraction analysis and of the electrostatic field parameters measurements showed a decrease in crystallinity from 0.29 to 0.27 and the formation of positive charges on the surface of the sample, while the formation of a double electric layer according to dielectric spectrometry data was not detected. During the separation of the model water-oil emulsions, an increase in efficiency was revealed as 80% to 98% and the separation productivity from 15 dm³/(m²·h) to 35 dm³/(m²·h) after treatment in the field of a unipolar corona discharge of cellulose acetate membranes, which is explained by a change in the supramolecular and chemical structure of the latter.

The structure and property of polyacrylonitrile-based microfiltration membranes for oil-water emulsion separation

The polyacrylonitrile (PAN)-based microfiltration membranes material was prepared used waste polyacrylonitrile fibers as the raw material. The PAN membranes have two different structure, the surface layer is finger pore structure, below layer is cavernous pore structure with the porosity is 85.92%. The PAN membrane shows super strong hydrophilicity (high water permeability) and ultra low adhesion of underwater oil (good oilresistance) under different pH values and different surfactants. The flux of PAN membranes is 1952.63 L•m−2• H−1 • bar−1, the oil retention ability is 99.14% when the film thickness was 100 μm, the PAN concentration was 7%, and the alkali treatment time was 1 h. The PAN membrane is an environmentally friendly material, have good application potential for oil-water emulsion separation and recycling of waste oil. Preparation of separation and filtration materials provides a good way to recycle waste PAN fibers and has potential practical value in oil-water separation field.

Superhydrophilic and underwater superoleophobic in-situ derived 2D Ni-Fe MOF/HNTs composite-enhanced polyvinyl alcohol (PVA) hydrogel membrane for gravity-driven oil/water separation

In this work, we successfully prepared the 2D Ni-Fe MOF-HNTs composites by in-situ hydrothermal growth, followed by enabling it to full into PVA hydrogels, thereupon fabricating the oil/water separation 2D Ni-Fe MOF-HNTs/PVA-decorated stainless steel mesh. The structures and mechanical properties of the composites were identified by a series of characterizations. The results showed that the 2D Ni-Fe MOF nanosheets were gown on the outer surface of HNTs to form the exclusive composite structure and the 2D Ni-Fe MOF-HNTs/PVA composite membrane possessed a more compact pore structure, which exhibited the outstanding mechanical performance and the fatigue resistance ability. The surface property characterizations demonstrated that the 2D Ni-Fe-MOF-HNTs/PVA composite membrane had the superhydrophilic and underwater superoleophobic features. Ultimately, the results of the water flux and separation efficiency on 2D Ni-Fe-MOF-HNTs/PVA composite membrane for oil-water separation and emulsion separation corroborated that it was a promising high-performance separation composite membrane.

Highly antifouling porous EVAL/F127 blend membranes with hierarchical surface structures

Membrane fouling is widely acknowledged as the major hindrance to the efficient separation of oil-water emulsions. Superhydrophilic EVAL/F127 porous membranes with micron-submicron hierarchical structure were prepared via micro-molding assisted immersion precipitation (PSμm process). The micron-scale concave-convex structure was constructed by the micro-molding process with 1000 mesh sandpaper, and then the sub-micron structure of the surface was modulated by F127. With the combination of optimized hierarchical structure and F127 hydrophilic modifier, EVAL/F127 porous membrane is superhydrophilic (water contact angle less than 10°) and strongly anti-fouling. ATR-FTIR, SEM, AFM, water contact angle (WCA), pure water flux, porosity and equilibrium water content were used to characterize the textural and properties of EVAL porous membranes. The separation performance and antifouling properties of the membranes were evaluated using oil-in-water emulsions as fouling agents. When the F127 content was 10%, the EVAL/F127 blended porous membrane not only performed well in retention performance (95.3% retention), but also had high flux recovery (91.6%) after hydrodynamic cleaning. Thus, the combined strategy based on hierarchical structure and hydrophilic modification provides a facile solution for the preparation of antifouling membranes.

Flexible and mechanically robust polyimide foam membranes with adjustable structure for separation and recovery of oil-water emulsions and heavy oils

Oil-water separation materials have been widely studied, however, these materials are mainly used to separate light oil-water mixtures, and the application of heavy oil separation and recovery is rarely involved. It is urgent to develop novel multi-functional oil-water separation materials, especially for the separation membrane for heavy oil. Herein, mechanically robust fiber-reinforced fluorinated polyimide foam membranes (FPIFMs) with adjustable multistage pore structure and high oil-water selectivity were prepared by freeze-drying and surface modification. FPIFMs exhibit high tensile strength of 3.80 MPa with the synergistic effect of PI fibers and PAA. Besides, the macro void structure of the foam membrane can be precisely adjusted to achieve the separation of different types of oil-water mixtures, oil-water emulsions, especially the separation and recovery of heavy oil. The results show that the foam membranes can separate light oil (26935L·m−2·h−1), oil-water emulsion (364L·m−2·h−1) and heavy oil (30L·m−2·h−1) under gravity. This stable, highly flexible, highly efficient and reusable foam membrane is an attractive option for oil spill treatment and wastewater purification.

High flux composite membranes based on glass/cellulose fibers for efficient oil-water emulsion separation

It is a challenge to develop an oil-water separation membrane that simultaneously meets the requirements of environmentally-friendly, low-cost, high flux, high wet strength, and excellent separation efficiency. Herein, composite membranes based on glass and cellulose fibers were prepared by a series of steps including cellulose fiber skeleton construction, maleic anhydride (MA) modification, and plasma treatment. The micro-sized beaten cellulose fibers and nano-sized bacterial nanocellulose (BC) are interlaced with each other during the layer upon layer deposition via vacuum filtration, thus effectively fixing the glass fibers. Combined with MA crosslinking, the wet strength of the composite membrane is greatly increased to 6.55 N·m/g. Besides, the underwater superoleophobicity of the composite membrane (UOCA＞150°) was realized by constructing the micro- and nano-scale roughness through plasma treatment. When used for oil-water emulsion separation, an ultrahigh flux up to 12, 070 L/m2·h with the separation efficiency of ≥ 98.1% were achieved for the composite membranes solely under the driving of gravity. Micro- and nano-scale fibers are used to synergistically increase strength, and the hierarchical roughness is generated as an inherent property of the membrane. The unique structure resulting underwater superoleophobic composite membrane is of practical interest for oily wastewater treatment.

Freeze-casting multicomponent aerogel membrane with controllable asymmetric multilayer configuration for high flux gravity-driven separation of oil-water emulsion

Freeze-casting has been widely used to mix one or several functional components to form aerogel where the resulting structure is uniform and has no distinctive asymmetrical morphology and characteristics. Hence, a multilayered, multicomponent aerogel with tunable physical and chemical properties is desirable as it can extend the multifunctionality and versatility of the aerogel by integrating multiple functional materials. Here, a facile stacked freeze-casting method is reported to fabricate multilayered aerogel membrane with asymmetric morphology and opposing surface wettability from polyvinyl alcohol(PVA)/leached carbon black waste (LCBW) solutions and carbon nanotube (CNT) dispersion for separation of water-in-oil emulsions. The results show that the aerogel membrane can easily demulsify the emulsion at a remarkably high permeate flux (up to 427 ± 40 × 103 Lm−2hr-1bar−1) with rejection higher than ∼96% at an ultralow driving pressure of ∼640 Pa.

Chemically stable NH2-MIL-125(Ti)/Sep/PDA composite membranes with high-efficiency for oil/water emulsions separation

Nowadays, oily wastewater is a severe threat to the living environment of humankind. In recent years, MOF materials have shown great application potential in membrane separation and treatment of oily wastewater. In this paper, the mixed cellulose ester membrane (MCEM) was modified by polydopamine, and the NH2-MIL-125 (Ti)/Sep(sepiolite)/PDA composite membrane was prepared by simple vacuum filtration. The composite membrane had super-hydrophilic performance and underwater super-oleophobic performance, and could effectively separate oil-water emulsion separation performance. Also, the composite membrane showed good repeatability. After 10 cycles, the retention rate of petroleum ether-in-water emulsion was still more than 99%, and the flux was more than 2000 L·m−2·h−1. Since strong adhesion ability of PDA and the covalent interaction between NH2-MIL-125(Ti) and Sep, the chemically stable NH2-MIL-125(Ti)/Sep/PDA composite membrane was exposed to the strong acid (pH=1), alkali (pH=11), and salt (5% saturated NaCl) solutions showed excellent chemically stable. These outstanding properties made the composite membrane have great potential in the removal of oily wastewater.