Fouling-resistant Composite Membranes for Separation of Oil-in-water Microemulsions

Fouling-resistant ceramic-supported polymer composite membranes were developed for removal of oil-in-water （O/W） mieroemulsions. The composite membranes were featured with an asymmetric three-layer structure, i.e., a porous ceramic membrane substrate, a polyvinylidene fluoride （PVDF） ultrafiltration sub-layer, and a polyamide/polyvinyl alcohol （PVA） composite thin top-layer. The PVDF polymer was east onto the tubular porous ceramic membranes with an immersion precipitation method, and the polyamide/PVA composite thin top-layer was fabricated with an inteffaeial polymerization method. The effects of the sub-layer composition and the recipe in the inteffaeial polymerization for fabricating the top-layer on the structure and performance of composite membranes were systematically investigated. The prepared composite membranes showed a good performance for treating the O/W microemulsions with a mean diameter of about 2.41μm. At the operating pressure of 0.4MPa, the hydraulic permeability remained steadily about 190L·m^-2·h^-1, the oil concentration in the permeate was less than 1.6mg·L^-1, and the oil rejection coefficient was always higher than 98.5% throughout the operation from the beginning.

Coalescence separation of oil water emulsion on amphiphobic fluorocarbon polymer and silica nanoparticles coated fiber-bed coalescer

Discharging untreated oily wastewater into the environment disrupts the ecological balance,which is a global problem that requires urgent solutions.Superhydrophilic and superoleophilic fibrous medium(FM)effectively separated oil–water emulsion as it was hydrophobic underwater.But its separation efficiencies(SEs)first increased to 98.9%,then dropped to 97.6%in 10 min because of oil-fouling.To tackle this problem,FM deposited with 0%–10%silica nanoparticle(NPsFMs),then coated by fluorocarbon polymer(X-[CH_(2)CH_(2)O]nCH_(2)CH_(2)O-Y-NH-COOCH_(2)C4F9)(FCNPs FMs),was used to enhance its roughness and regulate its initial wettability to improve the anti-fouling property.FCFM and FCNPs FMs were hydrophobic and oleophobic in air and oleophobic underwater.Their water contact angles,oil contact angles and oil contact angles were 115.3°–121.1°,128.8°–136.5°,and 131.6°–136.7°,respectively,meeting the requirement of 90°–140°for coalescence separation.FCNPs FM-5 had the best separation performance with a constant value of 99.8%in 10 min,while that of FCNPs FM-10 slightly decreased to 99.5%.Theoretical released droplet(TRD)diameter,calculated by the square root of the product of pore radius and fiber diameter,was used for the evaluation of coalescence performance.Analyzed by two ideal models,TRD diameter and fiber diameter showed a parabola type relationship,proving that the separation efficiency was a collaborative work of wettability,pore size and fiber diameter.Also,it explained the SEs reduction from FCNPs FM-5 to FCNPs FM-10 was revelent to the three parameters.Moreover,FCNPsFMs effectively separated emulsions stabilized by cationic surfactant CTAB(SEs:97.3%–98.4%)and anionic surfactant SDBS(SEs:91.3%–93.4%).But they had an adverse effect on nonionic surfactant Tween-80 emulsion separation(SEs:94.0%–71.76%).Emulsions made by diverse oils can be effectively separated:octane(SEs:99.4%–100%),rapeseed oil(SEs:97.3%–98.8%),and diesel(SEs:95.2%–97.0%).These findings provide new insights for designing novel materials for oil–water separation by coalescence mechanism.

Separation of Oil Phase from Dilute Oil/Water Emulsion in Confined Space Apparatus

A miniature process for separating the oil phase from dilute oil/water emulsion is developed.This process applies a confined space apparatus,which is a thin flow channel made of two parallel plastic plates.The space between the two plates is rather narrow to improve the collisions between oil droplets and the plate surface.Oil droplets have an affinity for the plate surface and thus are captured,and then coalesce onto the surface.The droplet size distribution of the residual emulsion resulted from the separation process is remarkably changed.The oil layer on the plate weakens the further separation of oil droplets from the emulsion.Three types of plate materials,polypropylene(PP),polytetrafluoroethylene(PTFE) and nylon 66,were used.It is found that PP is the best in terms of the oil separation efficiency and nylon 66 is the poorest.The interaction between droplets in the emulsion and plate surface is indicated by the spreading coefficient of oil droplet on the plate in aqueous environment,and the influences of formed oil layer and plate material on the separation efficiency are discussed.

Superhydrophobic melamine sponge prepared by radiation-induced grafting technology for efficient oil-water separation

This paper presents a superhydrophobic melamine(ME)sponge(ME-g-PLMA)prepared via high-energy radiation-induced in situ covalent grafting of long-alkyl-chain dodecyl methacrylate(LMA)onto an ME sponge for efficient oil–water separation.The obtained ME-g-PLMA sponge had an excellent pore structure with superhydrophobic(water contact angle of 154°)and superoleophilic properties.It can absorb various types of oils up to 66–168 times its mass.The ME-g-PLMA sponge can continuously separate oil slicks in water by connecting a pump or separating oil underwater with a gravity-driven device.In addition,it maintained its highly hydrophobic properties even after long-term immersion in different corrosive solutions and repeated oil adsorption.The modified ME-g-PLMA sponge exhibited excellent separation properties and potential for oil spill cleanup.

Experimental investigation on using CO_(2)/H_(2)O emulsion with high water cut in enhanced oil recovery

CO_(2) emulsions used for EOR have received a lot of interest because of its good performance on CO_(2)mobility reduction.However,most of them have been focusing on the high quality CO_(2) emulsion(high CO_(2) fraction),while CO_(2) emulsion with high water cut has been rarely researched.In this paper,we carried out a comprehensive experimental study of using high water cut CO_(2)/H_(2)O emulsion for enhancing oil recovery.Firstly,a nonionic surfactant,alkyl glycosides(APG),was selected to stabilize CO_(2)/H_(2)O emulsion,and the corresponding morphology and stability were evaluated with a transparent PVT cell.Subsequently,plugging capacity and apparent viscosity of CO_(2)/H_(2)O emulsion were measured systematically by a sand pack displacement apparatus connected with a 1.95-m long capillary tube.Furthermore,a high water cut(40 vol%) CO_(2)/H_(2)O emulsion was selected for flooding experiments in a long sand pack and a core sample,and the oil recovery,the rate of oil recovery,and the pressure gradients were analyzed.The results indicated that APG had a good performance on emulsifying and stabilizing CO_(2) emulsion.An inversion from H_(2)O/CO_(2) emulsion to CO_(2)/H_(2)O emulsion with the increase in water cut was confirmed.CO_(2)/H_(2)O emulsions with lower water cuts presented higher apparent viscosity,while the optimal plugging capacity of CO_(2)/H_(2)O emulsion occurred at a certain water cut.Eventually,the displacement using CO_(2)/H_(2)O emulsion provided 18.98% and 13.36% additional oil recovery than that using pure CO_(2) in long sand pack and core tests,respectively.This work may provide guidelines for EOR using CO_(2) emulsions with high water cut.

Effects of Different Heavy Crude Oil Fractions on the Stability of Oil-in-water Emulsions —— Isolation of functional fractions from heavy crude oil and study of their properties

The functional fractions (acid, basic, amphoteric and neutral fractions) are isolated from the Liaohe Du-84 heavy crude oil and Shengli Gudao Kenxi heavy crude oil by ion-exchange chromatography, but the conventional fractions (saturates, aromatics, resins and asphaltenes) are also isolated from the heavy crude oil. These components have been characterized by spectroscopic methods (FT-IR), namely acid number, basic nitrogen number, ultimate analysis and molecular weight measurements using vapor pressure osmometry (VPO). The ion-exchange chromatography method based on separation by a functional group induces a little change on the nature of the crudes and reasonable mass balances can be easily obtained.

Experimental measurements of water content in crude oil emulsions by terahertz time-domain spectroscopy

We measured the water content （0.01% 0.25% w/w） in crude oil emulsions using terahertz time-domain spectroscopy （THz-TDS）. To improve the precision and range of the measurements, we used 1 and 10 mm thick quartz cells. The experiments were performed at 20 ℃ and the THz wave was transmitted vertically to the samples and detected on the other side. The experimental results suggest linear relation for the THz absorption coefficient and the water content of the crude oil emulsions in the observed range. The linear dependence facilitates high-precision measurements of the water content of crude oil. This suggests the potential of THz-TDS in determining the water concentration in crude oil and borehole fluid identification.

Super-hydrophobic and super-lipophilic functionalized graphene oxide/polyurethane sponge applied for oil/water separation

Nowadays, oil spills have led to a serious environmental crisis of the world. To deal with this problem, inspired from super-hydrophobic lotus leaf, this study fabricated super-hydrophobic and super-lipophilic functionalized graphene oxide/polyurethane （FGP） sponge by a simple and inexpensive dip coating method. The resulting FGP sponge was characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and water contact angle. The results expressed that FGP sponge exhibited a similar surface structure to that of a lotus leaf, and possessed the super-hydrophobic characteristic with the water contact angle （WAC） of 152°± 1 °. The absorption capacity and reusability were also investigated. It can be seen that, the FGP sponge can remove a wide range of oils and organic solvents from water with good absorption capacities （up to 35 times of its own mass）. Significantly, after 10 cycles the absorption capacity of the oils and organic solvents was higher than 90°; for the reused FGP sponge, demonstrating the good reusability of the FGP sponge. Therefore, this study probably provided a simole way to remove the pollutions ofoil spills and toxic organism from water.

Superhydrophobic Micro/Nanostructured Copper Mesh with Self-Cleaning Property for E ective Oil/Water Separation

In this work, a simple method was carried out to successfully fabricate superoleophilic and superhydrophobic N-dodecyltrimethoxysilane@tungsten trioxide coated copper mesh. The as-fabricated copper mesh displayed prominent superoleophilicity and superhydrophobicity with a huge water contact angle about 154.39° and oil contact angle near 0° Moreover, the coated copper mesh showed high separation efficiency approximately 99.3%, and huge water flux about 9962.3 L·h^-1·m-2, which could be used to separate various organic solvents/ water mixtures. Furthermore, the coated copper mesh showed favorable stability that the separation efficiency remained above 90% after 10 separation cycles. Benefiting from the excellent photocatalytic degradation ability of tungsten trioxide, the coated copper mesh possessed the self-cleaning capacity. Therefore, the mesh contaminated with lubricating oil could regain superhydrophobic property, and this property of self-cleaning permitted that the fabricated copper mesh could be repeatedly used for oil and water separation.

Tungsten incorporated mobil-type eleven zeolite membranes: Facile synthesis and tuneable wettability for highly efficient separation of oil/water mixtures

Tungsten (W) incorporated mobil-type eleven (MEL) zeolite membrane (referred to as W-MEL membrane) with high separation performance was firstly explored for the separation of oil/water mixtures under the influence of gravity.W-MEL membranes were grown on stainless steel (SS) meshes through in-situ hydrothermal growth method facilitated with (3-aminopropyl)triethoxysilane (APTES) modification of stainless steel meshes,which promote the heterogeneous nucleation and crystal growth of W-MEL zeolites onto the mesh surface.W-MEL membranes were grown on different mesh size supports to investigate the effect of mesh size on the separation performance of the membrane.The assynthesized W-MEL membrane supported on 500 mesh (25μm)(W-MEL-500) exhibit the hydrophilic nature with a water contact angle of 11.8°and delivers the best hexane/water mixture separation with a water flux and separation efficiency of 46247 L·m^(-2)·h^(-1)and 99.5%,respectively.The wettability of W-MEL membranes was manipulated from hydrophilic to hydrophobic nature by chemically modifying with the fluorine-free compounds (hexadecyltrimethoxysilane (HDTMS) and dodecyltrimethoxysilane(DDTMS)) to achieve efficient oil-permselective separation of heavy oils from water.Among the hydrophobically modified W-MEL membranes,W-MEL-500-HDTMS having a water contact angle of146.4°delivers the best separation performance for dichloromethane/water mixtures with a constant oil flux and separation efficiency of 61490 L·m^(-2)·h^(-1)and 99.2%,respectively along with the stability tested up to 20 cycles.Both W-MEL-500-HDTMS and W-MEL-500-DDTMS membranes also exhibit similar separation performances for the separation of heavy oil from sea water along with a 20-fold lower corrosion rate in comparison with the bare stainless-steel mesh,indicating their excellent stability in seawater.Compared to the reported zeolite membranes for oil/water separation,the as-synthesized and hydrophobically modified W-MEL membranes shows competitive separation performances in terms of flux and separation efficiency,demonstrating the good potentiality for oil/water separation.

Zwitterionic monolayer grafted ceramic membrane with an antifouling performance for the efficient oil-water separation

Enormous demands on the separation of oil/water(O/W)emulsions in various industries,such as petrochemical,food and pharmaceutical industries,are looking for high performance and energy-efficient separation methods.Ceramic membranes have been used to deal with O/W emulsions,for its outstanding characteristics of easy-operation,high-flux,and long-term stability.However,membrane fouling is still a challenge in the industrial application of ceramic membranes.Herein,antifouling ceramic membranes were fabricated by grafting zwitterions on the membrane surface via an environment-friendly two-step grafting method,which improves the antifouling property and permeability.Successful grafting of such zwitterion on the ceramic surface was assessed by the combination of FTIR and XPS characterization.More importantly,the hydration can be formed by electrostatic interactions layer on the modified membrane,which was confirmed by TGA characterization.The antifouling performance of prepared zwitterionic ceramic membranes in the separation of O/W emulsions was systematically tested.The results suggested that zwitterion can significantly improve the flux of ceramic ultrafiltration membrane,and can also improve antifouling property dramatically by reducing the irreversible fouling in the separation of O/W emulsions.Therefore,zwitterionic ceramic membranes hold promising potentials as an antifouling,highly efficient and green method in the practical purification of the O/W emulsions.

Treatment of oil/water emulsion by polyethylene glycol ultrafiltration membrane

Polyethylene glycol(PEG) membranes with different molecular mass cut-offs were used to treat oil/water emulsion, and the effects of experimental conditions including pressure, temperature and different opera- ting modes on permeate flux and removal rate of chemical oxygen demand (COD_ Cr) were studied. The results show that the permeate flux of ultrafiltration membrane is influenced by pressure and temperature; practical pressure is chosen to be 0.30.7MPa for the PEG with molecular mass cut-offs of 8000 and 0.71.0 MPa for the PEG with molecular mass cut-offs of 2500; and the practical temperature is chosen to be 2532℃. Different operating modes of ultrafiltration also influence the permeate flux and removal rate of COD_ Cr. The ultrafiltration membrane of intermittent cross-flow operating mode is easier to be influenced by blocky polarization and contamination than that of sequential cross-flow operating mode. Removal rate of COD_ Cr in intermittent cross-flow and sequential cross-flow condition can be maintained at about 93%.

Experimental investigation of the effects of various parameters on viscosity reduction of heavy crude by oil-water emulsion

The effects of water content, shear rate, temperature, and solid particle concentration on viscosity reduction （VR） caused by forming stable emulsions were investigated using Omani heavy crude oil. The viscosity of the crude oil was initially measured with respect to shear rates at different temperatures from 20 to 70℃. The crude oil exhibited a shear thinning behavior at all the temperatures. The strongest shear thinning was observed at 20℃. A non-ionic water soluble surfactant （Triton X-100） was used to form and stabilize crude oil emulsions. The emulsification process has significantly reduced the crude oil viscosity. The degree of VR was found to increase with an increase in water content and reach its maximum value at 50 % water content. The phase inversion from oil- oil emulsion occurred at 30 in-water emulsion to water-in- % water content. The results indicated that the VR was inversely proportional to temperature and concentration of silica nanoparticles. For water-in-oil emulsions, VR increased with shear rate and eventually reached a plateau at a shear rate of around 350 s^-1. This was attributed to the thinning behavior of the continuous phase. The VR of oil-in-water emulsions remained almost constant as the shear rate increased due to the Newtonian behavior of water, the continuous phase.

Effects of Different Heavy Crude Oil Fractions on the Stability of Oil-in-water Emulsions—the film properties of heavy crude functional components and water system

A series of π-A isotherms are drawn to study the film properties of the components with Langmuir-Blodgett technique. The effects of the aromaticity of spread solvents and pH value on the air/water film formed by the components are investigated. Acid fraction and asphaltene can form stable two-dimensional insoluble films on an air/water surface. The surface film pressure of acid fraction and asphaltene is higher and more stable than that of the other fractions. The surface film pressure of the fraction increases evidently under the basic condition (pH=12). The results show that the interfacial activity of acid fraction and asphaltene is superior to that of the other fractions and the basic condition is favorable to the stability of the O/W emulsion.

Characterization of water-in-crude oil emulsions in oil spill response

The formation of water in crude oil emulsions occurs when crude oils are spilled into sea. The water in crude oil emulsions significantly change the properties of the spilled crude oils and in turn influence the choices made relating to oil spill countermeasures. The water in crude oil emulsions were characterized using various techniques in this study. The environmental scanning electron microscopy observation of water droplets in the emulsions is also presented. It is a powerful tool in emulsion observations.

The superhydrophobic sponge decorated with Ni-Co double layered oxides with thiol modification for continuous oil/water separation

In this paper, the superhydrophobic polyurethane sponge(SS-PU) was facilely fabricated by etching with Jones reagent to bind the nanoparticles of Ni-Co double layered oxides(LDOs) on the surface, and following modification with n-dodecyl mercaptan(DDT). This method provides a new strategy to fabricate superhydrophobic PU sponge with a water contact angle of 157° for absorbing oil with low cost and in large scale. It exhibits the strong absorption capacity and highly selective characteristic for various kinds of oils which can be recycled by simple squeezing. Besides, the as-prepared sponge can deal with the floating and underwater oils, indicating its application value in handling oil spills and domestic oily wastewater. The good self-cleaning ability shows the potential to clear the pollutants due to the ultralow adhesion to water. Especially, the most important point is that the superhydrophobic sponge can continuously and effectively separate the oil/water mixture against the condition of turbulent disturbance by using our designed device system, which exhibit its good superhydrophobicity, strong stability.Furthermore, the SS-PU still maintained stable absorption performance after 150 cycle tests without losing capacity obviously, showing excellent durability in long-term operation and significant potential as an efficient absorbent in large-scale dispose of oily water.

Quantitatively probing interactions between membrane with adaptable wettability and oil phase in oil/water separation

The membrane method based on adaptive wettability shows great advantages in oil-water separation.At present,researches focus on the excellent application performance of the membrane material,while the quantitative analysis of interactions in oil-water separation is rarely recognized.Herein,we constructed an adaptable wettability membrane with multiple polymer networks by polydopamine(PDA)and mussel-inspired amphiphilic polymer.Based on the Owens three-probe liquid method,the surface energy of the modified membrane was verified to meet the adaptive wettability conditions,with surface energies(γ-8)of 147.6 mJ m^(−2)(superhydrophilic/underwater superoleophobic)and 49.87 mJ m^(−2)(superhydrophobic/superoleophobic),respectively.The adhesion or repulsion of the membrane to the oil phase under different conditions during the separation process was quantified by the chemical probe AFM technique.In addition,the oil-water selective separation mechanism was further analyzed in a simplified membrane microchannel model.The results show that the different wetting produces capillary additional pressure in opposite directions,resulting in different energies to be overcome when the oil or water passes through the microchannels,thus achieving selective separation.

Highly Durable Ag-CuO Heterostructure-Decorated Mesh for Efficient Oil/Water Separation and In Situ Photocatalytic Dye Degradation

It is of great necessity yet still a challenge to develop superwetting functional interfacial materials for simultaneously separating insoluble oil and degrading soluble dye pollutants in practical wastewater.In this work,a Ag-CuO heterostructure-decorated mesh was fabricated via facile alkali etchingcalcination and photoreduction approaches.The as-synthesized mesh with superhydrophilicity and underwater superoleophobicity displayed high separation efficiency(>99.998%)for diverse oil/water mixtures.Besides,it demonstrated more superior photocatalytic performance in dye degradation than those of bare CuO nanostructure-coated materials,which is primarily attributed to the intensive visible light harvesting and efficient electron-holes separation occurred on noble metal-semiconductor heterostructures.Furthermore,on account of the tenacity of Cu substrate as well as enhanced structural stability,this binary composite-decorated mesh exhibited highly reliable durability and robustness after 10 cycles of photocatalytic degradation tests,and even being ultrasonic worn for 30 min.More importantly,our developed mesh was capable of in situ catalytic degrading water-soluble organic dyes during oil/water separation under visible light irradiation.Therefore,such a dexterous and feasible strategy may afford a new route to construct bifunctional and predurable materials for actual sewage purification.

Efficient oil-water separation by novel biodegradable all cellulose composite filter paper

Industrial production and domestic discharge produce a large amount of oily wastewater, which seriously affects the stability of the ecological environment. Membrane separation technology provides another path to treating oily wastewater. And appropriate surface modification of the membrane helps to achieve high efficiency of treating oily wastewater. With green, economy and stability been more concerned.The focal research reports a completely biodegradable all cellulose composite filter paper(ACCFP) composed of Ⅰ-cellulose macrofibers and Ⅱ-cellulose matrix. It is a simple one-step impregnation method to adjust the surface microstructure of the pristine filter paper(PFP), and it does not involve with chemical reaction. The pre-wetted ACCFP consist of Ⅱ-cellulose hydrogel and Ⅰ-cellulose reinforcement in the process of oil-water separation. This layer of hydrogel is the fundamental to underwater superoleophobicity, which determines their eligibility for applications of efficient oil-water mixture or oil-in-water(oil/water) emulsion separation. The separation efficiency of oil-water mixture and oil/water emulsion exceed 95% and 99.9%, respectively. In addition, excellent mechanical properties of ACCFP in dry and wet conditions ensure its stability in service and prolong service life in applications. The focal study provides a new method for high-performance oil-water separation and it is more in line with sustainable chemistry.

Oil-water Separation Properties of Produced Fluid by Polymer Flooding

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