Oil-water Emulsion Separation Research Articles

Freeze-Casting Multicomponent Aerogel with Controllable Asymmetric Multilayer Configuration for High Flux Gravity-Driven Separation of Oil-Water Emulsions

Freeze-Casting Multicomponent Aerogel with Controllable Asymmetric Multilayer Configuration for High Flux Gravity-Driven Separation of Oil-Water Emulsions

Two-step facile fabrication of a superamphiphilic biomimic membrane with a micro–nano structure for oil–water emulsion separation on-demand

A smart separation membrane with super-amphiphilic wettability was fabricated by a simple two-step method. The separation efficiency of the membrane towards the emulsion is more than 99.6%, and it can be recycled.

Robust Ag@Pda/Pen Nanofibrous Membrane with Anti-Bacterial Performance for Durable and Efficient Oil-Water Emulsion Separation

Robust Ag@Pda/Pen Nanofibrous Membrane with Anti-Bacterial Performance for Durable and Efficient Oil-Water Emulsion Separation

Fabrication of magnetically responsive anti-fouling and easy-cleaning nanofiber membrane and its application for efficient oil-water emulsion separation

The magnetically responsive anti-fouling nanofiber membrane (MRANM) was fabricated for efficient oil-water emulsion separation, which could be cleaned using oscillating magnetic field. MRANM was prepared by grafting superparamagnetic Fe3O4 nanoparticles onto the surface of electrospun polyacrylonitrile nanofiber membrane (PANM). Compared with PANM, the water contact angle of MRANM decreased from 104° to 0°, indicating that the hydrophilicity of the membrane was significantly improved. For the emulsions of hexadecane, octane and rapeseed oil, the separation efficiency was 98.04%, 96.59% and 92.67%, respectively. After the treatments in oscillating magnetic field, the separation efficiency kept above 95% after 8 times recycling, which indicated that the MRANM had good regenerability and reusability. The as-fabricated membrane with magnetic responsiveness facilitated an effective method for solving the membrane fouling problem during practical applications of separation high viscosity oil-water emulsion.

A reusable, biomass-derived, and pH-responsive collagen fiber based oil absorbent material for effective separation of oil-in-water emulsions

Absorbent material plays an increasingly important role in oil-water separation due to its high-efficiency, cost-effective and environment-friendly. Herein, amino-functionalized biomass-derived collagen fiber matrix (defined as A-CFM) with dodecyl hydrocarbon chains was prepared as oil-water separation adsorbent material by in-situ graft copolymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and glycidyl methacrylate (GMA). The A-CFM possesses favorable porosity, appropriate pore size and excellent hydrophobicity, which exhibits high separation efficiency (~99.90%) for whether surfactant-free emulsions or surfactant stabilized emulsions, even after three cycles. In addition, the tunable wettability of A-CFM can be achieved by altering the pH value, which not only imparts outstanding recycling performance, but also improves the antifouling performance to A-CFM absorbent material. Furthermore, the analysis of oil-water separation mechanism indicates that hydrophobicity and capillary force, especially electrostatic interaction (electrostatic attraction/repulsion), play a key role in separating emulsions stabilized by ionic surfactant. Our findings expend the knowledge of oil-in-water emulsion separation, as well as pave a new way for developing high-performance adsorbent materials with good application prospects in oil-water emulsion separation.

Robust antifouling NH2-MIL-88B coated quartz fibrous membrane for efficient gravity-driven oil-water emulsion separation

Here, a robust antifouling NH2-MIL-88B coated quartz fibrous membrane (NM88B@QFM) was developed for efficient oil-water emulsion separation via a one-step solvothermal method. The effects of NM88B precursor concentration on the morphology and surface wettability of the membranes were investigated. The prepared NM88B@QFM showed good photo-Fenton self-cleaning ability and superhydrophilicity/underwater superoleophobicity with water contact angle and underwater oil contact angle of 0° and 161.3°, respectively. The NM88B@QFM exhibited high separation efficiencies and high permeation fluxes (up to 99.4% and above 350 L m−2 h−1, respectively for a series of surfactant-stabilized oil-in-water emulsions under solely gravity-driven separation. Moreover, the NM88B@QFM showed good antifouling self-cleaning ability because Fenton-like catalytic NM88B can degrade the foulant on the membrane surface, enabling it to maintain its performance over many separation cycles. In view of the advantages of NM88B@QFM such as high separation efficiency, excellent self-cleaning and gravity self-driven performance, this type of membrane appears to be a promising candidate for low energy input, long-lasting oil-water separation.

Bifunctional BiOCl/TiO2 decorated membrane for antibiotic photodegradation and oil-water emulsion separation

Membrane separation is a simple and efficient technology for waste water treatment. However, organic pollutants such as antibiotics in complex water environment are hard to remove by the physical separation process. The coupling of photocatalysis and membrane separation can effectively remove the oil pollutants, meanwhile degrade the antibiotics. In this work, a composite membrane (BiOCl/TiO2@PAN) was prepared by the electrospinning technology and hydrothermal process. The membrane showed an excellent superhydrophilicity in air and an underwater superoleophobicity, thus it could separate a series of oil in water emulsions with a high permeability (231–613 L m-2h−1) without extra energy supply. Moreover, owing to the photoresponse ability of BiOCl and TiO2, the membrane could effectively degrade a variety of antibiotics including the typical antibiotic tetracycline, chlortetracycline, oxytetracycline and demeclocycline within 30 min under full-spectrum and visible light irradiation. Eight-cycle repeating experiments showed that composite membrane had an excellent stability and an efficiency in photocatalytic degradation and oil–water emulsion separation. Photo-responsive composite membrane prepared in this work showed a broad application prospect in treatment of complex sewage where oily waste and antibiotics simultaneously exist.

Molecular grafting and zwitterionization based antifouling and underwater superoleophobic PVDF membranes for oil/water separation

Effective surface modification strategies are at the core of developing efficient and antifouling membranes for a range of separation, purification, and wastewater treatment applications. The inherently hydrophobic nature of most polymeric membranes is one of the primary factors for their high fouling susceptibility. In this work, we have designed a simple and straightforward membrane modification methodology utilizing the reactive nature of polydopamine to molecularly graft short chain amino alkanes followed by zwitterionization using 1,3-propanesultone. The prepared membranes demonstrated superhydrophilicity accompanied with underwater superoleophobicity originating from the hydrophilic nature of polydopamine, aminoalkanes, and strong hydration due to zwitterionic functionality. The surface chemistry, nanostructuring, and surface roughness play an essential role in delivering required properties in the membranes. The prepared membranes showed ultrahigh BSA protein resistance and low oil droplets adhesion. The functionalized membranes showed a manifold boost in permeability for pure water and BSA solution, and separation of oil-water emulsion at high permeation rates. The antifouling nature of the membranes helped in maintaining the permeation behavior for multiple cycles with >96% flux recovery after ten consecutive cycles and excellent rejection in oil-water emulsion separation (>98%). The superwetting properties, along with high permeation, rejection, and antifouling properties, make these membranes a potential candidate for oily water separation and demonstrate the effectiveness of simple molecular level grafting and functionalization as a straightforward method for membrane modifications.

Preparation and application of low-cost ceramic membranes for separation of oil-water emulsion

This work presents the impact of fabricating pressure on the performance of ceramic membranes during the dead-end microfiltration of an oil-water emulsion. The membranes used in this study were fabricated at a pressure of 40 kN and 100 kN using the dry compaction method. The membrane characterization was done using XRD and FTIR analysis. The membrane performance was evaluated by carrying dead-end microfiltration experiments using synthetic oil-water emulsion as a feed at a trans-membrane pressure of 30 psi. The experimental results confirmed that the membrane fabricated at higher fabricating pressure (100 kN) gives better performance in terms of maximum oil rejection of 95.7% with the maximum flux of 2.04x10−3 m3/m2.s.

Facile fabrication of 3D hierarchical micro-nanostructure fluorine-free superhydrophobic materials by a simple and low-cost method for efficient separation of oil-water mixture and emulsion

In this paper, a simple, environmentally friendly, fluorine-free, economical and effective hydrophobic modification method for melamine sponge (MS) with cobalt oxyhydroxide (CoOOH) and stearic acid (STA) was developed. The 3D pine needle-like hierarchical micro-nanostructure CoOOH coated onto the framework of MS as superhydrophobic materials were successfully constructed and synthesized by low temperature hydrothermal method. By combining the high porosity, superior elasticity, and mechanical stability of the MS with the nanometer scale roughness of CoOOH and low surface energy of STA, the modified CoOOH@STA@MS not only has superhydrophobic surface with the water contact angle of 155°, but also shows outstanding adsorption performance towards the various organic solvents/oils (absorption weight ranging from 20 to 50 times of its own) and excellent recyclability. Additionally, the modified MS can be used as an efficient oil pollutant removal equipment for continuous oil-water separation with the help of peristaltic pump. Furthermore, the CoOOH@STA@MS could be able to separate immiscible oil-water mixture as well as surfactant-stabilized water-in-oil emulsions. All the advantages indicate that the superhydrophobic sponge is the ideal material for oil spills treatment and environmental control.

Robust paper-based materials for efficient oil–water emulsion separation

Robust paper-based materials for efficient oil–water emulsion separation

MOF-Embedded Bifunctional Composite Nanofiber Membranes with a Tunable Hierarchical Structure for High-Efficiency PM0.3 Purification and Oil/Water Separation.

Herein, a unique hierarchically structured composite nanofiber membrane, consisting of a zeolitic imidazolate framework-8-embedded polyethersulfone (PES@ZIF8) fiber layer and a polysulfonamide/polyethersulfone (PSA/PES) fiber layer, was successfully developed to cope with the complex environments during the actual filtration/separation process and overcome the conflict between high filtration efficiency and low air pressure resistance. Due to the advantages of the synergistic effect of multicomponents and the bi-layer hierarchical structure, the integrated PES@ZIF8-PSA/PES filter possesses an extremely high air filtration efficiency (up to 99.986%) under a very low pressure drop (only 15 Pa), superior PM0.3 purification capacity (close to 99.95%), long-term recycling ability for purifying real smoke PM2.5 from >800 to <10 μg/m3, extremely high temperature resistance (exceed 200 °C), flame retardancy, good chemical stability, satisfactory transmittance, and robust self-cleaning ability. Apart from these, it achieves effective separation of oil-water mixtures and oil-water emulsions as a result of selective wettability including hydrophobicity and superoleophilicity. In particular, the PES@ZIF8-PSA/PES nanofiber membranes maintain outstanding air filtration and oil/water separation properties under the high temperature or strong acid/alkali conditions. This special comprehensive performance gives the PES@ZIF8-PSA/PES-based filtration/separation membranes a wider application prospect ranging from environmental governance to individual protection and industrial security.

Desert beetle-like microstructures bridged by magnetic Fe3O4 grains for enhancing oil-in-water emulsion separation performance and solar-assisted recyclability of graphene oxide

Owing to its high selective adsorption and excellent cyclability, superwetting materials have attracted considerable attention in environmental governance, especially oily wastewater treatment. However, the inferior separation efficiency and high recovery energy consumption seriously limit the actual application of superwetting particles in oil–water emulsion separation. Herein, inspired reversely by the water collection and water retention of the hydrophilic/superhydrophobic structure on the Stenocara beetle’s back, we fabricated magnetic graphene oxide composite with beetle-like microstructure by one-step solvothermal and environmentally friendly ball milling method. Magnetic composite with superhydrophobic/superoleophilic bumps–hydrophilic underlayer exhibits high hydrophobicity/oleophilicity in air and high oleophobicity underwater. In the process of particle assembly, the Fe3O4 grains with abundant oxygen vacancies peeled off from the in-situ deposited magnetic Fe3O4 microspheres play a bridging role to immobilize the superhydrophobic carbon black particles on the graphene oxide (GO) surface. On the unique surface of magnetic composite, attributed to strong π–π/n–π interface adsorption and hydrophobic interaction, the oil–water separation can be rapidly demulsified and the superoleophilic bumps (superhydrophobic carbon black nanoparticles) can capture and aggregate tiny oil droplets. The hydration layer formed in the hydrophilic region effectively prevents the captured oil droplets from spreading on the composite structure, thus enhancing the emulsion separation ability of magnetic GO. More importantly, the prepared composites exhibit efficient recycling and regeneration under solar irradiation, which is superior to the recovery efficiency of traditional GO sheets lacking high self-heating components. These inverse beetle-like magnetic GO-based particles open up a new opportunity for the design and fabrication of advanced demulsifiers in the field of oil–water emulsion separation.

Asymmetric superwetting stainless steel meshes for on-demand and highly effective oil-water emulsion separation

Oil-water separation, especially emulsion separation, has become a global challenge due to frequent oil spills and the increase in industrial oily wastewater. It is of great significance to develop a feasible and effective separation membrane to purify highly stable emulsified oily wastewater. Here, a Janus membrane that can be used to realize the on-demand separation of oil-water emulsion is prepared by spraying silicon dioxide nanoparticles modified by hexadecyltrimethoxysilane onto the stainless steel meshes. The on-demand separation of surface-stabilized emulsions whether water-in-oil or oil-in-water emulsions can be achieved by using the Janus membrane. In addition, the prepared membrane still maintains outstanding performance after 10 oil-water separation cycles and 50 sandpaper abrasion cycles. The membrane can keep hydrophobicity whether under acidic or alkaline conditions, so it can cope with various harsh environments.

Fast demulsification of oil-water emulsions at room temperature by functionalized magnetic nanoparticles

Oil-water emulsions separation is a significant and intractable problem in many industrial processes, especially in petroleum industry. To deal with the demulsification of oil–water emulsions, a novel kind of amphiphilic magnetic demulsifier (M-ANP) has been designed and successfully synthesized by grafting aliphatic alcohol nonionic propylene oxide-ethylene oxide block polyether (ANP) (~22.3 mg/g) onto the surface of epoxy-functionalized magnetite (Fe3O4) nanoparticles (~9.1 nm). The physicochemical and interfacial properties of M-ANP have been characterized and analyzed. The bottle tests show that the M-ANP performs well in fast (less than 5 min) and relatively complete demulsifying (up to 95.5%) both water-in-oil emulsions (water-in-crude oil, water-in-bitumen) and oil-in-water emulsions (diesel-in-water, crude oil-in-water, etc.) under room temperature. It also works well in breaking the stable water-in-asphaltene emulsions, achieving the demulsification efficiency of 90.0% within 2 min without heating (at 2000 ppm of M-ANP). Mechanistic study shows that the ANP and magnetic nanoparticles work synergistically in emulsions separation. The hydrophilic polyethylene oxide segments in the ANP would form hydrogen bonds with water, facilitating the interfacial adsorption of M-ANP. Furthermore, the multi-functional characteristics of magnetic nanoparticles (nano size, magnetic response and high density) promote the transfer of nanoparticles in dispersed phase and enhance the gravity settling and magnetic separation process of coalesced droplets. This kind of nanoparticle demulsifier would serve for promising applications in a variety of industrial and environmental processes at an energy-saving way.

Fabrication of Manganese Oxide-silica Based Functional Polymer Composite Membranes and Their Environmental Application

ABSTRACT Oil-water emulsion separation is a complicated task and recently oil-water spills made it crucial to find a solution to resolve this unfavorable environmental concern. Membrane separation is economical, environmentally safe, and operationally feasible separation process among different methods adopted so far. Keeping this in view neat polysulfone and manganese oxide silica composite membrane were synthesized. The prepared Mn3O4, mesoporous silica, Mn3O4@SiO2, neat and fabricated PSF membranes were thoroughly characterized by X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric, and differential scanning calorimetry, tunneling electron microscopy and scanning electron microscopy. The solvent content, porosity, surface behavior, thermal, and mechanical properties of the membranes were also studied. The increase in the concentration of nanofiller increases the solvent interaction, porosity, thermal stability, and mechanical strength. Amongst all 5 wt.% composite membrane have greater oil/water separation capacity due to greater amount of nanofiller and high porosity. Facile tuning of properties during fabrication process makes these composite membranes a potential candidate to address the oil/water pollution problem of important environmental concern.

Enhancing oil-in-water emulsion separation performance of polyvinyl alcohol hydrogel nanofibrous membrane by squeezing coalescence demulsification

The membrane fouling is the obstruction that limits the efficiency and durability of the nanofibrous membrane in oil-water emulsion separation. Herein, a polyvinyl alcohol (PVA) hydrogel nanofibrous membrane could continuously separate emulsion by using squeezing coalescence demulsification (SCD). During this SCD process, the small oil droplets can coalesce into bigger ones under the mandatory compression of the pore wall. And then the coalesced oil droplets will pass through the nanofibrous membrane and form an oil layer, and the oil layer can be easily removed. Furthermore, a two-phase numerical model is proposed to demonstrate this coalescence process of oil droplets in the pore. The numerical results also indicate that the pore size, wettability of membrane, and the interface tension coefficient between oil and water can control the efficiency of SCD. This SCD method endows PVA hydrogel nanofibrous membrane with a sustained separation capability, which implys that this method has great potential in practical application.

A Universal Strategy for the Preparation of Dual Superlyophobic Surfaces in Oil-Water Systems.

There are some methods to prepare superwetting surfaces with underwater superoleophobicity (UWSOB) or underoil superhydrophobicity (UOSHB), but it is still thorny to put forward a universal strategy for constructing dual superlyophobic surfaces in oil-water systems due to a thermodynamic contradiction. Herein, a universal strategy was proposed to prepare the dual superlyophobic surfaces in oil-water systems only via delicately controlling surface chemistry, that is, adjusting the ratios of superhydrophilic and superhydrophobic counterparts in the spray solution. Three types of materials, attapulgite (APT), TiO2, and loess, were chosen to prepare a diverse series of mixed coatings (mass gradient of superhydrophobic counterparts from 0 to 100 wt %). With the proportion of each superhydrophobic counterpart increasing, the underwater oil contact angle (θo/w*) of each mixed coating slightly decreased but still was more than 150°, that is, UWSOB. In contrast, the underoil water contact angle (θw/o*) was significantly improved, realizing the transformation from UOHL (or UOHB) to UOSHB. More importantly, the respective mass ratios of superhydrophobic counterparts in the resulting mixed coatings of APT, TiO2, and loess were finally determined to be 0.3, 0.4, and 0.2, respectively. Taking APT as a model, a train of mixed APT coatings with different superhydrophobic components were systematically characterized and analyzed. Finally, the prepared superlyophobic separation mesh in oil-water systems was applied to the separation of various surfactant-stabilized oil-water emulsions. We envision that this universal strategy we proposed will show a significant application potential in addressing scientific and technological challenges in the field of interfacial chemistry such as oil-water separation, microfluidics, microdroplet manipulation, antifogging/icing, cell engineering, drag reduction, and so forth.

Preparation of Janus membrane based on biomimetic polydopamine interface regulation and superhydrophobic attapulgite spraying for on-demand oil-water emulsion separation

Here, we report a Janus membrane constructed using a sustainable regenerated cellulose (RC) membrane as matrix, based on biomimetic polydopamine (PDA) interface regulation and superhydrophobic attapulgite (SOATP) spraying. The dual-action PDA was reasonably interfacially-regulated by high temperature-induced self-polymerization to construct a superhydrophilic surface with PDA layer/particle hierarchical structures, which strengthened the interfacial interactions between the organic RC substrate and inorganic SOATP. Subsequently, SOATP was sprayed on the bottom surface of membrane via a simple spraying method to obtain a superhydrophobic surface. The resulting RC@PDA/SOATP Janus membrane exhibited a superhydrophilic top surface and superhydrophobic bottom surface, with excellent separation efficiency (>99%) and acceptable permeation flux toward different types of emulsions. The membrane also showed good renewability, excellent environmental durability and structural stability. The facile and versatile interface regulation and spraying techniques, as well as the environmentally friendly and economical raw materials, were used, which makes the Janus membrane a promising solution for a range of applications in the field of oil-water separation.

Fabrication of crosslinking modified PVDF/GO membrane with acid, alkali and salt resistance for efficient oil-water emulsion separation

Although a great deal of superhydrophilic/underwater superoleophobic membranes has been developing for oil-water emulsion separation, most of them could be destroyed or lose their underwater superoleophobicity after exposure to complex conditions. In this study, a crosslinking modified PVDF/GO membrane with acid, alkali and high salt resistance was successfully prepared by a simple crosslinking process between acrylic acid and ethylene glycol dimethacrylate (EGDMA). The influences of content of acrylic acid on the membrane performance and structure evolution were investigated. The resultant composite membrane showed superior underwater superoleophobicity even in acid, alkali and salt environments. Additionally, the composite membrane could effectively separate various surfactant-stabilize emulsions under gravity-driven via wettability capillary effect with high rejection (>99%) and flux (>145 L m−2 h−1). The composite membrane also exhibited outstanding recyclability because of the stable covalent bridged multiple networks structure. The antifouling performance, stability and impressive recyclability make the composite membrane a promising candidate for long-term oil-water emulsion treatment.