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.

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.

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.

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.

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.

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.

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.

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.

Cyclonic separation process intensification oil removal based on microbubble flotation

The cyclonic-static microbubble flotation column has dual effects including the cyclonic separation and floatation separation with the characteristics of the small lower limit of the effective separation size, short separation time, large handling capacity, and low operation cost. It shows significant advantages in the oily wastewater treatment field, especially the polymer flooding oily wastewater treatment aspect. In this paper, the cyclonic separation function mechanism of the cyclonic-static microbubble flotation column was studied, the impact of the parameters including the feeding rate, aeration rate, circulating pressure, and underflow split ratio on the cyclonic separation efficiency was investigated, and the cyclonic separation efficiency model was established as well. In addition, by applying the Doppler Laser Velocimeter (LDV) and Fluent simulation software, the test and simulation to the single-phase flow velocity field of the cyclonic separation section of the cyclonic-static microbubble flotation column were carried out, and the velocity distribution rule of the cyclonic separation section was analyzed under the singlephase flow conditions.

Study on Application of Novel Flocculating Agent in Treating Refinery Wastewater with High Concentration of Pollutants

After conducting a lot of screening experiments the appropriate flocculating formulations for treating high-concentration wastewater discharged from a certain refinery were selected. The oil removal rate and COD removal achieved by these flocculating formulations were better than that achieved by the conventional compound formulation consisting of polyaluminium chloride(PAC) and polyacrylamide(PAA) . Addition of an oil/water separating agent to the formulation could improve its oil removal performance to facilitate the oil/water separation of the oil-in-water emulsion in the high-concentration wastewater along with improved adaptability of the formulation to the wastewater containing high concentration of pollutants. This flocculating agent has promising prospects for commercial application.

Demulsification with simultaneous water purification by coupling filtration and enhanced oil droplet coalescence at anode interface in an electrochemical reactor

With the increasing demand of recycling disposal of industrial wastewater,oil-in-water(O/W)emulsion has been paid much attention in recent years owing to its high oil con-tent.However,due to the presence of surfactant and salt,the emulsion was usually stable with complex physicochemical interfacial properties leading to increased processing diffi-culty.Herein,a novel flow-through electrode-based demulsification reactor(FEDR)was well designed for the treatment of saline O/W emulsion.In contrast to 53.7%for electrical demul-sification only and 80.3%for filtration only,the COD removal efficiency increased to 92.8%under FEDR system.Moreover,the pore size of electrode and the applied voltage were two key factors that governed the FEDR demulsification performance.By observing the mor-phology of oil droplets deposited layer after different operation conditions and the behavior of oil droplets at the electrode surface under different voltage conditions,the mechanism was proposed that the oil droplets first accumulated on the surface of flow-through elec-trode by sieving effect,subsequently the gathered oil droplets could further coalesce with the promoting effect of the anode,leading to a high-performing demulsification.This study offers an attractive option of using flow-through electrode to accomplish the oil recovery with simultaneous water purification.

OIL/WATER SEPARATION IN A LIQUID-LIQUID CYLINDRICAL CYC-LONE

The oil/water separation in a liquid-liquid cylindrical cyclone is experimentally studied in this article.The effects of the flow split-ratio and the flow rate on the oil/water separation performance are determined.From the experimental results,it is shown that with the increase of the flow split-ratio,the oil/water separation efficiency is enhanced at first,and an optimal flow split-ratio exists,beyond that optimal split-ratio,the watercut in the underflow keeps constant,while the oil content in the overflow begins to decrease.The process of the oil core structure formation and the phase distribution in the cyclone are determined by numerical simulations.Furthermore,the dependence of the separation efficiency on the Reynolds number and the flow split-ratio is investigated based on a dimensional analysis.A comparison between the predicted values and the experimental data shows a good agreement.

Advanced Electrospun Nanofibrous Materials for Efficient Oil/Water Separation

The frequent occurrence of crude oil leakage accidents and the massive discharge of industrial oily wastewater not only caused huge damage and pollution to the ecosystem but also wasted a lot of precious resources.Therefore,it is urgent to solve the worldwide problem of oil/water separation.As a leader in advanced fiber materials,nanofibrous materials prepared by electrospinning have the advantages of high permeability,high separation efficiency,large specific surface area,adjustable wettability,simple preparation process,and low cost,making it attracted more attention of researchers in oil/water separation.This article mainly reviews the recent progress of various electrospun nanofibrous materials for oil/water separation field.The preparation and synthesis of nanofibrous adsorbents,nanofibrous membranes,and nanofibrous aerogels in recent years based on different applications,design principles,and separation approaches are systematically summarized.Finally,this review discusses the challenges and future development directions in oil/water separation.

3D-printed controllable gradient pore superwetting structures for high temperature efficient oil-water separation

Superwetting surfaces have the potential to address oil pollution in water,through their ability to separate the two.However,it remains a great challenge to fabricate stable and efficient separation structures using conventional manufacturing techniques.Furthermore,the materials traditionally used for oil-water separation are not stable at high temperature.Therefore,there is a need to develop stable,customizable structures to improve the performance of oil-water separation devices.In recent years,3D printing technology has developed rapidly,and breakthroughs have been made in the fabrication of complicated ceramic structures using this technology.Here,a ceramic material with a gradient pore structure and superhydrophobic/superoleophilic properties was prepared using 3D printing for high-efficiency oil-water separation.The gradient pore structure developed here can support a flux of up to 25434 L/m^(2)h,which is nearly 40%higher than that an analogous structure with straight pores.At 200℃,the oil-water separation performance was maintained at 97.4%.Furthermore,samples of the material exhibited outstanding mechanical properties,and chemical stability in a variety of harsh environments.This study provides an efficient,simple,and reliable method for manufacturing oil-water separation materials using 3D printing,and may have broader implications for both fundamental research and industrial applications.

Efficient demulsification of ultralow-concentration crude oil-in-water emulsion by three-dimensional superhydrophilic channels

Efficient extraction of crude oil,the major energy resource of current concern and high demand worldwide,is of paramount importance in both energy and environmental fields.However,it remains a great challenge to separate the crude oil-in-water emulsions with an ultralow oil content of<200 ppm.Here,the three-dimensional and superwetting channels are developed by coating titanium foams with anodic TiO_(2) nanotube arrays.The channels render superhydrophilic and underwater superoleophobic feature,which enables rapid formation of water channels that expel the oil droplets.A high separation efficiency of ∼96.8% and low total organic carbon content of ∼6 ppm are thus achieved for the ultralow-concentration crude oil-in-water emulsions.The pressure and time dependence of the separation process is systematically studied with a critical pressure of 12.25 kPa.Such a high performance is close to the theoretical limit imposed by the ultralow concentration,and shows obvious advances over either organic membranes or inorganic frameworks.

Fast processing nylon mesh by surface diffuse atmospheric plasma for large-area oil/water separation

In recent years,numerous studies have been reported for oil/water separation,such as superoleophilic materials for oil absorption and underwater superoleophobic membranes for continuous separation.However,for the recovery of oil slick pollution on near-shore ocean surface caused by various reasons,large area and fast availability of used materials are needed to be considered.Herein,we report an efficient and environmentally friendly method to fast process nylon mesh by surface diffuse atmospheric plasma(SDAP)for large-area oil/water separation.Nylon mesh is funcionalized by atmospheric plasma to generate micro/nano composite structures on the surface,resulting in superhydrophilicity and underwater superoleophobicity within only seconds.The pre-wetted modified nylon mesh can achieve high efficiency(>99.9%)and circulating water flux(~30,000 L·m^(-2)·h^(-1)),with high intrusion pressure(~3 kPa)and universality in oil/water separation.Regular plasma unconditionally generated in the atmosphere with the merit of efficiently functionalizing surface has the potential of large-area materials treatment.This study might take one step further for large-area industrial oily wastewater recovery and even oil slicks collection in near-shore water bodies.

Electrospinning organic solvent resistant preoxidized poly(acrylonitrile)nanofiber membrane and its properties

A high performance preoxidized poly(acrylonitrile)(O-PAN)nanofiber membrane with excellent solvent resistance,thermal stability and flexibility was fabricated by the preoxidation of electrospun PAN nanofiber membrane.The performance of resultant O-PAN nanofiber membrane was optimized by altering the PAN concentration and preoxidation temperature.The results showed that the O-PAN nanofiber membrane which made from PAN concentration of 14%(mass)and preoxidation temperature of 250.0
℃ have a more optimal comprehensive performance.In the long-term separation test of SiO2 particle(1 μm)in DMAc suspension,the permeate flux of O-PAN nanofiber membrane stabilized at 227.91 L·m^(-2)·h^(-1)(25
℃,0.05 MPa)while the SiO2 rejection above 99.6%,which showed excellent solvent resistance and separation performance.In order to further explore the application of the O-PAN nanofiber membrane,the OPAN nanofiber membrane was treated with fluoride and used in oil/water separation process.The O-PAN nanofiber membrane after hydrophobic treatment showed excellent hydrophobicity and good oil/water separation performance with the permeate flux about 969.59 L·m^(-2)·h^(-1)while the separation efficiency above 96.1%.The O-PAN nanofiber membrane exhibited a potential application prospect in harsh environment separation.

Superhydrophobic, mechanically flexible and recyclable reduced graphene oxide wrapped sponge for highly efficient oil/water separation

Water pollution has become an urgent issue for our modem society, and it is highly desirable to rapidly deal with the water pollution without secondary pollution. In this paper, we have prepared a reduced graphene oxide （RGO） wrapped sponge with superhydrophobicity and mechanically flexibility via a facile low-temperature thermal treatment method under a reducing atmosphere. The skeleton of this sponge is completely covered with RGO layers which are closely linked to the skeleton. This sponge has an abundant pore structure, high selectivity, good recyclability, low cost, and outstanding adsorption capacity for floating oil or heavy oil underwater. In addition, this sponge can maintain excellent adsorption performance for various oils and organic solvents over 50 cycles by squeezing, and exhibits extremely high separa- tion efficiencies, up to 6 × 10^6 and 3.6 × 10^6 L·m^-3.h^-1 in non-turbulent and turbulent water/oil systems, respec- tively. This superhydrophobic adsorbent with attractive properties may find various applications, especially in large-scale removal of organic contaminants and oil spill cleanup.

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

Currently,most of the materials for oil-water separation membranes are limited to fluorine-based polymers with low surface energy.However,it is not biodegradable and requires large amounts of organic and toxic solvents in the membrane manufacturing process.Therefore,interest in the development of a new eco-friendly oil-water separation membrane that does not cause secondary pollution and exhibits selective wettability characteristics in water or oil is increasing.The biopolymeric nanofibrous membranes inspired by fish skin can provide specific underwater oleophobicity,which is effective for excellent oil-water separation efficiency and prevention of secondary contamination.Fish gelatin,which is highly soluble in water and has a low gelation temperature,can be electrospun in an aqueous solution and has the same polar functional groups as the hydrophilic mucilage of fish skin.In addition,the micro/nanostructure of fish skin,which induces superoleophobicity in water,introduces a bead-on-string structure using the Rayleigh instability of electrospinning.The solubility of fish gelatin in water was removed using an eco-friendly crosslinking method using reducing sugars.Fish skin-mimicking materials successfully separated suspended oil and emulsified oil,with a maximum flux of 2086 Lm^(−2) h^(−1) and a separation efficiency of more than 99%.The proposed biopolymeric nanofibrous membranes use fish gelatin,which can be extracted from fish waste and has excellent biodegradability with excellent oil-water separation performance.In addition,polymer material processing,including membrane manufacturing and crosslinking,can be realized through eco-friendly processes.Therefore,fish skin-inspired biopolymeric membrane is expected to be a promising candidate for a sustainable and effective oil-water separation membrane in the future.