Emulsion Separation Research Articles

Simple temperature-regulated polymerization for the fabrication of a tea polyphenols-modified PVDF membrane for emulsion separation

Surface modification of membranes through facile coating methods is a promising way to improve their pollution resistance and separation performance.

Tannic acid induced in situ growth of an underwater superoleophobic ZIF-8 composite membrane for emulsion separation

Tannic acid induced in situ growth of ZIF-8 crystals on a nylon membrane, creating a multifunctional composite membrane that exhibits remarkable underwater superhydrophobicity and resistance to oil adhesion.

Liquid–liquid extraction for in situ carboxylic acid recovery via continuous membrane-based emulsion separations

A membrane-based emulsion separator can enable continuous solvent extraction in bioprocessing separations with substantially improved demulsification and mass transfer rates, including where emulsion formation is a challenge.

Numerical analysis of superoleophilic-superhydrophobic filtration system for emulsions separation using lattice Boltzmann method

Numerical analysis of superoleophilic-superhydrophobic filtration system for emulsions separation using lattice Boltzmann method

Constructing robust and anti-fouling superwettable membrane with layer-by-layer assembly of Fe(OH)3 colloid

Layer-by-layer (LBL) assembly method, with the advantages of simple operation and strong universality, has attracted much attention recently. However, the weak molecule-to-molecule and molecule-to-ion interactions have limited its development. During this work, the molecule-to-solid interaction was adopted and a robust LBL coating was achieved by alternately depositing positively charged Fe(OH)3 colloids and negatively charged sodium alginate molecules. The molecule-to-solid interaction could continuously regenerate under corrosive conditions due to water insolubility and the chemical stability of solids. When the electrostatic interaction was broken, the abundant chemically stable solids acted as anchors to immobilize the soluble molecules and maintain the stability of the LBL coating. The prepared superwettable membranes exhibited superior oil-in-water emulsion separation efficiency, anti-fouling properties, and chemical stability. Meanwhile, the separation performance survived one week's harsh environments of strong acid and alkali.

Rational designed of PVDF membrane based on surface modification of εPL anchored by PC for crude oil emulsion separation

For high-viscosity wastewater containing crude oil, the membrane material is easily clogged with contaminations, resulting in decreased flux and potentially loss of separation ability. In this study, a superhydrophilic/underwater superoleophobic PVDF membrane (PVDF-PC-εPL) was designed by the self-polymerization of proanthocyanidins (PC) and the grafting reaction of ε-polylysine (εPL), which showed a rough micro-nano structure without adding the inorganic particles. The PVDF-PC-εPL membrane displayed outstanding self-cleaning ability for high-viscosity crude oil, and the separation efficiency of the crude oil-in-water emulsion could be greater than 99.4%. The underwater oil contact angle (UWOCA) of the PVDF-PC-εPL membrane was 165°, after the PVDF-PC-εPL membrane had been exposed to air or water for 6 weeks, or soaked in different pH or seawater for 24 h, the UWOCA remained above 154° and the water contact angle was always 0°. The modification method on the PVDF membrane proposed in this study offers a fresh perspective and choice for preparing the oil-water separation materials.

Low-pressure driving Co3O4/PAN nanofiber membrane with peroxymonosulfate activation self-cleaning for efficient wastewater purification

Nanofiber membrane separation technologies are promising for separation of emulsions, but it is still limited by membrane fouling. Herein, a new low-pressure driving Co3O4/polyacrylonitrile (PAN) nanofiber membrane (CPNFM) with peroxymonosulfate (PMS) activation self-cleaning ability was developed by simple electrospinning technology. The effects of Co3O4 dosage on the properties and structures of resulting nanofiber membranes were investigated. The results revealed excellent superhydrophilic/underwater superoleophobic properties of the optimized CPNFM even under harsh conditions, such as acid, alkali and salt. Under sole gravity-driven, the optimized CPNFM efficiently separated multiple surfactant-stabilized emulsions with high separation efficiency (>99%) and superior flux (>300 L m−2 h−1). The optimized CPNFM also displayed a good catalytic effect toward the degradation of organic dyes through PMS activation. The effective synergy of the optimized CPNFM can also efficiently separate mixed wastewater composed of emulsion and organic dyes with high efficiency (99% for emulsion and 98% for methylene blue) and superior flux (>300 L m−2 h−1). Additionally, CPNFM displayed excellent self-cleaning ability, with restored separation performance after cycling through simple PMS activation. Overall, the high separation efficiency, good stability, and self-cleaning capability of the proposed CPNFM make it a potential candidate for long-term wastewater purification.

Cross-Linked Cellulose Nanofibril Aerogel with Multiscaled Pores and Dual Wettability for Emulsion Separation

Cross-Linked Cellulose Nanofibril Aerogel with Multiscaled Pores and Dual Wettability for Emulsion Separation

Macroporous polyvinyl alcohol-formaldehyde-silicon composite sponges with designed structure for high-efficiency water-in-oil emulsion separation

Macroporous materials with suitable pore structure and surface composition have demonstrated their advancing applications in absorption, adsorption, and separation. In this contribution, two types of macroporous polyvinyl alcohol-formaldehyde (PVFs) based composite sponges, stearoyl chlorides modified polyvinyl alcohol/PVF (PVA/PVF-CH) and octadecyltrimethoxysilane modified PVA/PVF (PVA/PVF-Si) are designed and synthesized through the secondary crosslinking reaction between the hydroxyl groups in PVA and PVF with formaldehyde, and subsequently covalently bonding the long-alkyl chains into the network of the composite sponge. Basic characterizations confirm PVA/PVF-CH and PVA/PVF-Si composite sponges exhibit the open-cell structure as original PVFs with porosity up to 80.1%, hydrophobic networks, and narrow pore size distribution (5 µm to 60 µm). Notably, the PVA/PVF-Si, possessing the smallest average pore size (14.4 µm), exhibits ignorable swelling performances in a wide range of organic solvents and excellent mechanical properties and separation properties for oil from water-in-oil emulsion with separation efficiency and flux up to 99.99% and 7.65 × 104 L m−2h−1bar−1 as compared to PVA/PVF-CH, respectively. Those features indicate that PVA/PVF-Si composite sponges can be desirable for emulsion separation.

РАЗДЕЛЕНИЕ ВОДОНЕФТЯНЫХ ЭМУЛЬСИЙ ИЗ НЕФТЕЙ ВОСТОЧНО-СИБИРСКИХ МЕСТОРОЖДЕНИЙ

The article deals with the problem of the formation of oil-water emulsions. It is shown that some chemical compounds in crude oil - asphaltenes, resins, organic acids, chloride salts, mechani-cal impurities and solid paraffins have an emul–gating ability due to their surface activity. The regulatory requirements for crude and incoming oil for deep processing are analyzed. The data on the physical properties and component composition of the oils extracted in the fields of East-ern Siberia are given, on the basis of which it is concluded that these oils belong to the category of resinous and paraffin and can give stable emulsions in a mixture with water. For dehydration and desalination of oil, it is proposed to use special chemical reagents - demulsifiers. The meth-odology and results of an experimental comparison of the effectiveness of surfactants for the de-tection of a demulsifier suitable for the separation of oil-water emulsions from the oils of East Siberian fields are presented

A charged superhydrophilic-oleophobic anti-fouling sponges for rapid separation of O/W emulsions

The crude oil spillage and large-scale industrial release of oily effluents has led to significant ecological degradation and resource wastage. Traditional superwetting materials encounter intractable challenges for treating surfactant-stabilized oil–water emulsions, including trade-off effect of permeation flux and separation efficiency, and low emulsion processing life. These issues considerably impede advancements in oil–water separation industry. In order to enhance the demulsification durability of materials while ensuring high separation efficiency and flux, this work doped perfluorooctanoic acid (PFOA) onto the modified sponge surface with superhydrophilic charged surface, and a unique in-air superhydrophilic-oleophobic sponge was prepared. This special surface allows rapid water phase permeation yet offers remarkably more stable oleophobicity compared with traditional underwater oleophobic materials when processing a large amount of emulsions. The intrinsic oleophobicity endows the sponge outstanding fouling resistance and greatly increases the one-cycle emulsion treatment amount up to 1695 L·m−2. Moreover, the sponge's inherent long permeation channels and surface charge maintain a high separation efficiency of over 97 %. The large pores of the sponges and superhydrophilic surface provide a high permeation flux exceeding 40,000 L·m−2·h−1. The sponge with high separation efficiency, flux, and capacity marks a significant advancement, offering a promising strategy for superwetting material applications in oil-in-water emulsion separation fields.

Preparation and properties of PEEK-g-PNIPAm separation membranes with thermo-responsiveness for emulsion and organic liquid separation

Although poly (ether ether ketone) (PEEK) exhibits excellent solvent resistance, it could not be prepared directly by non-solvent induced phase separation (NIPS) method due to its poor solubility. Herein, PEEK porous membranes were successfully fabricated by combining NIPS and acid hydrolysis. The superhydrophilic thermo-responsive poly (N-isopropylacrylamide) (PNIPAm) polymer was in-situ grafted on the PEEK membrane surface via the UV grafting polymerization and improved the membrane interface hydrophilicity, making the membrane water contact angle changed from 89.5° to 0° at 25 °C. After heating the membrane surface to 40 °C, the membrane exhibited hydrophobicity (100°), realizing the thermo-responsiveness via switching the temperature. Furthermore, due to the transferred membrane wettability at different temperatures, PEEK-g-PNIPAm could separate different types of oil-bearing systems with high rejection above 99.0 %. What’s more, the PNIPAm layer also enhanced the membrane anti-fouling capacity. Benefiting from the extraordinary solvent resistance of the PEEK matrix, PEEK-g-PNIPAm maintains its intact morphology after 6 h immersion in various organic solvents, addressing the commonly reported problem of polymer membranes having certain solubility in solvents. The PEEK-based membranes with excellent solvent resistance could be useful in the oil-bearing separation.

Amino-functionalization of tungsten oxide nanoparticles for stable decoration in the active layer of alumina-supported inorganic-organic hybrid membrane with super-wettable and photocatalytic self-cleaning surfaces for crude oil-in-water emulsion separation

The ceramic membrane was hybridized with an amino-functionalized inorganic metal oxide and organic polymer to achieve the optimal oil and water surface wettability and photo-catalytic self-cleaning capability. The resulting membrane was used for the treatment of crude oil-contaminated wastewater under cross-flow filtration mode. The fundamental functional material, tungsten oxide nanoparticles (NH2-WO3 NPs) modified by aminopropyl triethoxysilane (APTES) was created and coated on the alumina ceramic support surface via interfacial polymerization, in which the material covalently cross-links on the membrane's active layer in the presence of terephthaloyl chloride (TPC) as a cross-linker and piperazine (PIP) as an external amine. Achieving a unique combination of oil and water surface wettability- superhydrophilicity (0° water-in-air contact angle) and underwater super-oleophobicity (160.25° under-water oil contact angle) was the key to creating the water-permeating NH2-WO3/PA@alumina ceramic membrane. The second advantageous feature of the membrane is its capacity for self-cleaning, which results from WO3 NP's innate photocatalytic activity that has been further enhanced by amino functionalization. A water permeate flux of up to 250 L m−2 h−1 and an oil/water separation efficiency of nearly 100 % were attained for an oil concentration of 50 ppm of crude oil-in-water emulsion when NH2-WO3/PA@alumina ceramic membrane was employed as a separation medium in a cross-flow filtration system for the separation of crude oil-in-water emulsion. Furthermore, the permeate flux decreased to ∼25 % of its initial flux after using NH2-WO3/PA@alumina ceramic for approximately 210 min. This was caused by organic pollutants in the oily water clogging the membrane pores. The permeate flux was recovered by exposing the membrane to UV light for photo-catalytic self-cleaning. Due to its water-passing nature, this membrane has high efficiency. Additionally, because the self-cleaning add-on removes the need for chemical cleaning, it is environmentally friendly.

Dual role of silk fabric functionalized with polymer/GO-tungsten oxide nanocomposites as superwettable membranes and photocatalysts for removing dye contaminants and emulsion separation

BackgroundWastewater containing hazardous dye contaminants has aroused significant concern and poses a great challenge to membrane technology. Herein, a novel bio-inspired silk fabric membrane modified with L-histidine functionalized polyglycidyl methacrylate composited with graphene oxide and tungsten oxide (amino-PGMA/GO-WO2.72) was successfully produced to treat wastewater contaminants. MethodsAn urchin-like WO2.72 nanoparticle is synthesized using the hydrothermal method. The synthesized WO2.72 nanoparticles are composited with an amino-functionalized PGMA/GO via dispersion polymerization techniques. Finally, a flexible membrane is created by dip-coating silk fabric in the amino-PGMA/GO-WO2.72 nanocomposite solution. Significant findingsThe fabricated membrane showed excellent superhydrophilicity, underwater superoleophobicity, and outstanding performance in separating methylene blue (MB) dye-mixed emulsions under gravity with a high permeation flux of about 1690 ± 40 L m−2 h−1. The amino-PGMA/GO-WO2.72 modified silk fabric membrane showed remarkable stability, allowing the membrane to withstand a high separation efficiency of 99 %. Furthermore, the photo-responsive ability of the heterojunction GO-WO2.72 catalyst materials present in the modified membrane can lead to the reduction of toxic nitro phenols, degradation of various dyes and textile effluents wastewater with high photodegradation efficiency under UV–-visible and solar light irradiation.

2D Ti3C2Tx modified with nano-AgPNPs antioxidant constructed hierarchical interface for high-throughput oily wastewater separation

Over-exploitation of fossil energy has led to the formation of enormous amounts of oily wastewater, which is increasingly polluting the environment of water bodies. The Ti3C2Tx-modified separation material is limited by surface roughness and surface chemical composition, and the permeation flux decreases significantly during continuous testing. In this study, silver-loaded polydopamine nanospheres (nano-AgPNPs) as antioxidants were prepared by in-situ reduction from Ag+ ions and polydopamine nanospheres, and then they self-assembled with Ti3C2Tx nanosheets to obtain hierarchical micro-nano structural nano-AgPNPs modified Ti3C2Tx [(AgPNPs)xT (x = 0.25, 0.5, 0.75, and 1)]. Because of their strong reduction properties, nano-AgPNPs antioxidants can effectively protect the active edges of Ti3C2Tx from dissolved oxygen, and greatly improve the oxidation resistance of Ti3C2Tx nanosheets, with no significant changes in morphology and physical phase after long-term placement. (AgPNPs)xT formed underwater oleophobic interfaces with the hierarchical structure on polyurethane (PU) sponge to prepare (AgPNPs)xT@PU separation sponges. Among them, (AgPNPs)0.5T@PU sponge showed the highest comprehensive performance with separation efficiency higher than 99.6% for various oil-water mixtures, especially high-throughput and permeation flux up to 247,787 L m–2 h–1 for cyclohexane-water mixtures. In addition, nano-AgPNPs greatly broadened the layer spacing of Ti3C2Tx and can form a functionalized interface of modified Ti3C2Tx on polyamide (PA) membrane and provide additional permeation channels, which enabled the (AgPNPs)0.5T@PA membrane to have excellent toluene-water emulsion separation efficiency up to 99.6%.

Elevating oil-in-water emulsion separation: Unleashing the power of exfoliated graphitic carbon nitride composite membranes

The current study describes composite membranes that utilise exfoliated graphitic carbon nitride (Eg-C3N4) as a promising membrane additive for oily-water separation, owing to its hydrophilic nature and high functionality. The integrated membranes have been discovered to have outstanding properties when Eg-C3N4 is used as a composite material in polysulphone (PSf) membranes. The study provides provide insights into the usage of such nanosheets to achieve good chemical interaction with the membrane matrix, enabling both Eg-C3N4 and PSf synergistic characteristics. The well-planned exfoliated g-C3N4-PSf composite demonstrated promising oil-water separation with an oil rejection capacity of >99 %. Furthermore, these exfoliated laminar planes interacted well with the polymer, resulting in membranes that were both thermally and mechanically stable. The membrane also has a high porosity range of 46.13 % to 76.03 % and a high-water uptake range of 42.23 + 1.68 % to 71.34 + 1.24 %, which explains the membrane's enhanced hydrophilicity and appropriate oily-water treatment capacity. Furthermore, the addition of Eg-C3N4 lowers surface roughness, which explains for the great antifouling capacity exhibited by the composite membrane, demonstrating a remarkable flux recovery ratio of about 99.1 % with no compromise in oil rejection during subsequent cycles.

High flux, self-cleaning electrospun nanofiber membrane using one-step blending method for highly efficient oil-in-water emulsion separation

Membrane separation technology is a vital method for separating oil/water emulsions. However, membrane fouling caused by repeated use has brought a series of problems such as reduced permeation flux and poor recycling. Herein, we fabricated a high-flux and self-cleaning electrospinning nanofiber membrane Polyacrylonitrile-NH2-MIL-88B(PAN-NH2-M88B) by a facile one-step electrospinning blending method for highly efficient oil/water emulsion separation. Benefit from the constructed micro/nano rough structure and hydrophilic surface of NH2-MIL-88B(NH2-M88B), the PAN-NH2-M88B membrane exhibited excellent separation performances, high wettability and permeation flux after multiple oil/water emulsion separation tests under visible light irradiation. The fabricated nanofiber membrane can achieve a high separation efficiency of 99.5 % and a high flux of 5095–7662 L m−2h−1 respectively for five types of oil-in-water emulsions. More importantly, the flux of the fabricated nanofiber membrane is 2–3 times that of the membrane prepared by the traditional phase conversion method, which greatly reduces the separation time and improves the separation efficiency. Moreover, the flux of the oil-contaminated membrane can be restored by simple visible light irradiation, demonstrating excellent photocatalytic self-cleaning property. Therefore, the membrane has good stability and can be reused for many times with little change in separation efficiency and flux. Owing to the facile preparation method and the excellent performances, the developed nanofiber membrane was expected to be an ideal candidate for industrial oil–water emulsion separation.

Preparation of Hydrophobic Functionalized Poly(vinyl alcohol) Formaldehyde-Based Composite Sponges for Highly Effective Water-in-Oil Emulsion Separation

Preparation of Hydrophobic Functionalized Poly(vinyl alcohol) Formaldehyde-Based Composite Sponges for Highly Effective Water-in-Oil Emulsion Separation

C3N4-BiOBr/PVC photocatalytic submerged membrane for oil-in-water emulsion separation with visible light-driven self-cleaning performance

Membrane separation has been widely used for oil-in-water separation, but the fouling of oil droplets on the membrane surface is still a challenge. Coating a photocatalyst layer on the membrane surface is an effective method for the regulation of hydrophobicity, degradation of stuck oil, and boosting the self-cleaning properties of the membranes. Thus, in this work, a heterostructure photocatalyst of carbon nitride-bismuth oxybromide (C3N4-BiOBr) with different proportions was coated on a polyvinyl chloride (PVC) layer and the performance of the resultant membrane was studied in the separation of oil-in-water emulsion under visible light. The experimental results exhibited that the membrane with C3N4 to BiOBr ratio of 40:10 coating had the lowest water contact angle of 42°, the maximum light harvesting, the lowest surface roughness, and the low recombination rate of charge carriers. The correlations drawn between surface morphology and fouling behavior of this membrane led to the maximum flux of 65 L·m−2·h−1, 99% separation efficiency, 100% Total Organic Carbon (TOC) removal, and excellent self-cleaning properties (flux recovery ratio of 93.8%). Therefore, this study provides a novel design strategy for multifunctional membranes that achieve effective treatment of oil-in-water emulsion wastewater.

Flexible, durable, and anti-fouling maghemite copper oxide nanocomposite-based membrane with ultra-high flux and efficiency for oil-in-water emulsions separation

In this study, we developed a novel nanocomposite-based membrane using maghemite copper oxide (MC) to enhance the separation efficiency of poly(vinyl chloride) (PVC) membranes for oil-in-water emulsions. The MC nanocomposite was synthesized using a co-precipitation method and incorporated into a PVC matrix by casting. The resulting nanocomposite-based membrane demonstrated a high degree of crystallinity and well-dispersed nanostructure, as confirmed by TEM, SEM, XRD, and FT-IR analyses. The performance of the membrane was evaluated in terms of water flux, solute rejection, and anti-fouling properties. The pinnacle of performance was unequivocally reached with a solution dosage of 50 mL, a solution concentration of 100 mg L−1, and a pump pressure of 2 bar, ensuring that every facet of the membrane’s potential was fully harnessed. The new fabricated membrane exhibited superior efficiency for oil–water separation, with a rejection rate of 98% and an ultra-high flux of 0.102 L/m2 h compared to pure PVC membranes with about 90% rejection rate and an ultra-high flux of 0.085 L/m2 h. Furthermore, meticulous contact angle measurements revealed that the PMC nanocomposite membrane exhibited markedly lower contact angles (65° with water, 50° with ethanol, and 25° with hexane) compared to PVC membranes. This substantial reduction, transitioning from 85 to 65° with water, 65 to 50° with ethanol, and 45 to 25° with hexane for pure PVC membranes, underscores the profound enhancement in hydrophilicity attributed to the heightened nanoparticle content. Importantly, the rejection efficiency remained stable over five cycles, indicating excellent anti-fouling and cycling stability. The results highlight the potential of the maghemite copper oxide nanocomposite-based PVC membrane as a promising material for effective oil-in-water emulsion separation. This development opens up new possibilities for more flexible, durable, and anti-fouling membranes, making them ideal candidates for potential applications in separation technology. The presented findings provide valuable information for the advancement of membrane technology and its utilization in various industries, addressing the pressing challenge of oil-induced water pollution and promoting environmental sustainability.Graphical