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Optical trapping of inorganic nanocrystals at oil/water interfaces was investigated under a loose focus condition. The target nanocrystals were octahedral gold nanoparticles (OGPs, 70 nm in size), ...

Summary Liquid-liquid phase flow in pipes merits further investigation as a challenging issue that has very rich physics and is faced in everyday applications. It is the main problem challenging the fluid flow mechanism in the oil and gas industry. The pressure gradient of liquid flow and flow pattern are still the topics of numerous research projects. In this paper, the emphasis is on further investigation to research the flow pattern, water holdup (HW), and pressure decrease for vertical, horizontal, and inclined flow directions of oil and water flows. Test section lines of 4.19-in. (106.426 mm) inner diameter (ID) and 5-m horizontal, 5-m inclined, and 5-m vertical test sections were serially connected. The experiments were conducted at 40°C using 2-cp viscosity oil and tap water, and oil density of 850 kg/m3, at the standard conditions. Fifty experiments were executed at 250 kPa at the multiphase flow test facility, with horizontal, upward (0.6° and 4°), downward (−0.6° and −4°) hilly terrain and vertical pipes. The oil and water superficial velocities were changed between 0.03 and 2 m/s. This evidence was obtained using video recordings; the flow patterns were observed, and the selection of each flow pattern was depicted for each condition. For horizontal and inclined flow, new flow patterns were documented (e.g., oil transfer in a line forms at the top of the pipeline, typically at high water rate, and water transfer at the lower part of the pipe at a high oil rate). The data were taken at each flow condition, resulting in new holdup and pressure drop. The results show that the flow rate and the pipe inclination angle have major impacts on the holdup and pressure drop performances. In the vertical flow, a clear peak was demonstrated by experiments after the superficial oil velocity reached a certain value. This peak is known as phase inversion point, where after this peak, the pressure starts declining as the superficial oil velocity increases. Also, slippage has been observed after varying inlet oil flow rates between the two phases. The experiments showed that with minor alteration in the inclination angle, the slippage was significantly changed. This study presented new experimental results (measured mainly at horizontal, inclined, and vertical flow conditions) of HW, flow pattern, and pressure drop. These findings are key evidence of the evolving oil-water and flowline estimate models.

Stimuli-responsive surfaces with wettability change between superhydrophilic and superhydrophobic are susceptible to oil contamination which often ruins the surface. Herein, a coating with pH-switchable wettability transition between superamphiphobic and superhydrophilic-superoleophobic is achieved by rationally designing oleophobic/pH-responsive polymer heterogeneous chemistry. Fabrics modified with this coating show repellency to both water and oils, while upon exposure to acidic water (pH = 1) the fabrics change to be superhydrophilic-superoleophobic within a short response time of5 s. More importantly, the superamphiphobicity of the fabric can be restored under mild alkaline condition (pH = 10), and the transition is reversible for many cycles. The effective in situ or ex situ wettability change under acidic/alkaline water treatment makes the coated fabric capable of separating oil-water mixture or even some mixtures of immiscible organic solvents. In addition, the coated fabric is also demonstrated to be promising as a new class of functional fabrics that provide protection against water and many oils in one condition, and can change to be hygroscopic, anti-static, oil-repellent and anti-oil-fouling in the other condition for improved wear comfort and self-cleaning.

An increase in the consumption of petroleum products in the transport and energy systems and intensive development of some branches of industry (especially petrochemical industry and oil refining) results in the accumulation of numerous waste in the form of waste oils, oil sludge and other oily liquids. The problem of waste disposal can be solved by using oily liquids as fuel for combustion at thermal power plants in order to produce thermal and electrical energy. To study the rheological characteristics of oil-water-coal emulsions based on anthracite with the solid phase concentration of 40%, an oil phase with the concentration of 49% (motor oils Motul 8100 X-cess 5W-40 and Comma Xtech 5W-30), water (10%) and nonionic surfactant (1%) as an emulsifier-stabilizer. It was found that the rheological characteristics of oil-water-coal emulsions depend not only on the granulometric composition of coal, but also on the viscosity of the dispersed medium (motor oils). Physicochemical and service properties of oil-water-coal systems under consideration allow using them as fuel. Given the availability and relative cheapness of feedstock, this type of fuel can successfully compete with traditional types of liquid fuels.

A cotton fabric with special wettability was prepared in two simple steps. The surface of the fabric was grafted with silicon-oxygen group using 3-(methacryloyloxy) propyl trimethoxysilane (MSPMA) as the reagent, and then (3-mercaptopropyl)triethoxysilane (MPTES) was used to react with the grafted fabric under ultraviolet light according to the principle of thiolene reaction. Meanwhile, the modified cotton fabrics with various pore sizes were obtained via modifying the cotton fabric with different pore size under the same experimental conditions. The as-prepared fabric had a better hydrophobic and lipophilic effect, whose water contact angle could be up to 146.7° and the separation efficiency for different kinds of oil/water mixtures was better than 94%. In addition, the pore sizes of cotton fabrics had a great effect on the rate of oil/water separation, which increased with the increase of the pore size.

Present study reports the application potential of a natural down fiber in the fields of oil-water separation and interfacial dye adsorption. The dripping experiment shows that the blue water dropl...

Hypothesis A binary mixture was used during injection with one water-miscible component and the other water-immiscible, which can help particles to migrate toward and then self-assemble at the interface. Experiments The ethanol-tetrachloromethane binary mixture was used to verify the self-assembly method, with the diameter of droplets being about 1 mm. As the ethanol diffused into the colloidal solution, the colloidal particles efficiently moved towards and self-assembled on the oil/water interface, while a colloidal particle film with high-coverage was able to rapidly form on the droplet surface even in an ultra-low concentration colloidal solution. The effects of ethanol concentration and particle concentration on self-assembly were investigated. Findings The driving force for self-assembly originated from the tension gradient generated by ethanol's concentration gradient at the particle/liquid interfaces, where the concentrations of ethanol and the colloidal solution had significant effects on self-assembly. The simulation and calculations results aligned well with experiments, providing the theoretical basis for this self-assembly method. Further, as-prepared magnetic particle-coated droplets transformed into a non-wetting soft solid, which had long lifetimes and could be precisely moved, coalesced, and transferred in various two-dimensional and three-dimensional liquid environments. Thus, wider applications are facilitated, such as droplet transfer, microreactor and other potential fields.

This article provides a perspective review on the use of modified cotton fabrics for oil–water separation. The principles of surface hydrophobicity of cotton fabrics are first described, from which the basis for producing superhydrophobic surfaces is presented. Then the preparation methods to convert hydrophilic cotton fabrics to hydrophobic fabrics are reviewed and discussed. Based on literature results the way to design novel preparation methods, the need to summarize testing protocols, and the comprehensive technoeconomic and sustainability analyses, are proposed. A demonstrative cotton fabrics test is used to reveal the significant role of conjugated fluid flows and surface interactions under different application scenarios for determining the separation efficiency of the oil–water mix.

Summary An experimental and theoretical investigation of surfactant-stabilized oil/water emulsion characteristics was carried out under water sweep (WS) and oil sweep (OS) conditions. Both hydrophilic and hydrophobic surfactants were used, with concentrations less than and more than the critical micelle concentration (CMC). Experimental data were acquired for detection of the phase-inversion region, which was measured simultaneously by several independent methods. These include a circular differential dielectric sensor (C-DDS), a rectangular differential dielectric sensor (R-DDS) (both sensors accurately detect the phase-inversion region), a pressure transducer, and a mass flowmeter. The addition of an emulsifier surfactant to an oil/water mixture generated a stable emulsion, which resulted in a phase-inversion delay. For water-continuous to oil-continuous flow, a hydrophilic surfactant was a better emulsifier, while for oil-continuous to water-continuous flow, a hydrophobic surfactant was a better emulsifier for creating more stable emulsions. The surfactant/oil/water emulsion resulted in an increase of the dispersed-phase volume fraction required for phase inversion, as compared to the case of oil/water dispersions without surfactant. For emulsions with surfactant concentrations above CMC, the presence of micelles contributed to further delay of the phase inversion, as compared to those with surfactant concentrations below CMC. The phase-inversion region exhibits a hysteresis between the OS and WS runs, below CMC and above CMC, which was due to the difference in droplet sizes caused by different breakup and coalescence processes for oil-continuous and water-continuous flow. This research shows that the DDS is an efficient instrumentation that can be used to detect the region where the emulsion phase inversion is expected to occur. Moreover, the experimental results and the pertinent analysis and discussion provide useful insights for a more informed design of surface facilities (including emulsion separators) in oil and gas production operations.

Summary As the second most widely used artificial lift method in the petroleum industry, electrical submersible pumps (ESPs) maintain or increase flow rates by converting the kinetic energy to hydraulic pressure. As oilfields age, water is invariably produced with crude oil. The increase of water cut generates oil-water emulsions due to the high-shearing effects inside a rotating ESP. Emulsions can be stabilized by natural surfactants or fine solids existing in the reservoir fluids. The formation of emulsions during oil production creates a high viscous mixture, resulting in costly problems and flow assurance issues, such as increasing pressure drop and reducing production rates. This paper, for the first time, proposes a new rheology model to predict the oil-water emulsion effective viscosities and establishes a link of fluid rheology and its effect with the stage pressure increment of ESPs. Based on Brinkman's (1952) correlation, a new rheology model, accounting for ESP rotational speed, stage number, fluid properties, and so on, is developed, which can also predict the phase inversion in oil-water emulsions. For the new mechanistic model to calculate ESP boosting pressure, a conceptual best-match flow rate (QBM) is introduced. QBM corresponds to the flow rate whose direction at the ESP impeller outlet matches the designed flow direction. Induced by the liquid flow rates changing, various pressure losses can be derived from QBM, including recirculation losses, and losses due to friction, leakage, sudden change of flow directions, and so on. Incorporating the new rheology model into the mechanistic model, the ESP boosting pressure under oil-water emulsion flow can be calculated. To validate the proposed model, the experimental data from two different types of ESPs were compared with the model predictions in terms of ESP boosting pressure. Under both high-viscosity single-phase fluid flow and oil-water emulsion flow, the model predicted ESP pressure increment matches the experimental measurements well. From medium to high flow rates with varying oil viscosities and water cuts, the prediction error is less than 15%.

In this work, a durable and sunlight-driven self-cleaning superhydrophobic cotton fabric was developed as a multifunctional oil/water separation material. First of all, Ag/AgCl was successfully deposited on the polydopamine modified cotton fabric surface by electrostatic adsorption, then the Ag/AgCl loaded fabric was coated by the polydimethylsiloxane (PDMS) via simple dip-coating method. The as-prepared cotton fabric (PDMS-Ag/AgCl@CF) presented the superhydrophobic property with water contact angle about 155°. Meanwhile, the prepared PDMS-Ag/AgCl@CF exhibited great tolerance and resistance to broad pH and various organic solvents, and it can also withstand 50 cycles of abrasion or 60 min of ultrasound treatment without an apparent decrease of superhydrophobicity, indicating its outstanding mechanical durability. As expected, this durable superhydrophobic fabric can availably separate various oil/water mixtures by gravity-driven force with high separation efficiency (over 97.8%), and it possessed good reusability. Additionally, the PDMS-Ag/AgCl@CF exhibited an outstanding self-cleaning performance under sunlight irradiation, due to visible light photocatalytic performance of Ag/AgCl. Finally, the resultant cotton fabric displayed good antibacterial activity. Therefore, in consideration of its prominent comprehensive performances, it is expected that the PDMS-Ag/AgCl@CF can be used as a promising material for oily water remediation.

Stable high flux is a big challenge for oil/water separation membranes due to the adhesivity and spreadability of oil droplets. Membranes with hydrophilic modification usually have high basic flux, but suffer from a serious flux decline. Membranes with synergic hydrophilic and low-surface-energy (LSE) modification show a remarkably relieved flux decline, but at the expense of low basic flux. The LSE domains on membrane surfaces promote oil fouling release but hinder water permeation. In order to relieve the adverse side effects of LSE domains, this study focuses on the distribution of hydrophilic and LSE domains on membrane surfaces. Membranes with a fluorine island structure are prepared, in which LSE domains are discrete in sub-microscaled distribution, while hydrophilic domains are consecutive in a wide area. The diameters of oil droplets are much larger than those of water molecules; therefore, water molecules quickly permeate at consecutive hydrophilic domains, and oil droplets are still released by discrete LSE domains. The stable flux of the membranes is improved from 280 to 770 Lm−2 h−1 bar−1 just by the manipulation of domain distribution.

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/m2h, which is nearly 40% higher than that an analogous structure with straight pores. At 200 °C, 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.

The use of enzymes as biocatalysts in industrial applications has received much attention during the last few years. Lipases are widely employed in the food and cosmetic industry, for the synthesis of novel biomaterials and as a greener solution for the treatment of waste cooking oils (WCO). The latter topic has been widely explored with the use of enzymes from several origins and types, for the treatment of different used and non-used cooking oils. The experimental conditions of such works are also quite broad, hampering the detailed understanding of the process. In this work we present a detailed characterization of the interaction of several commonly used lipases with different types of vegetal oils and food fats through coarse-grained molecular dynamics simulations. First, the molecular details of the oil/water (O/W) mixtures, namely at the O/W interface, are described. The O/W interface was found to be enriched in triglyceride molecules with higher polarity. Then, the interaction of lipases with oil mixtures is characterized from different perspectives, including the identification of the most important protein residues for this process. The lipases from Thermomyces lanuginosus (TLL), Rhizomucor miehei (RML) and Candida antarctica (CALB) were found to bind to the O/W interface in a manner that makes the protein binding site more available for the oil molecules. These enzymes were also found to efficiently bind to the O/W interface of all oil mixtures, which in addition to reactivity factors, may explain the efficient applicability of these enzymes to a large variety of edible oils and WCO.

Discharge of oily sewage causes serious environmental pollution and waste of resources, which can be solved by the process of oil/water separation. Polyurethane foam is a kind of promising candidate material for oil/water separation. In this work, a series of hydrophobic/lipophilic polyurethane foams were prepared by the in situ self-foaming method. The as-prepared polyurethane foams exhibited abundant open pore structures, excellent stability and superior hydrophobicity/lipophilicity. Thus, the as-prepared polyurethane foams can selectively absorb various oils/organic solvents from static and dynamic oil/water mixtures. The maximum absorption capacity for pump oil was up to 75.0 g g−1, and the separation fluxes were 1.5 × 106 L m−3 h−1 and 3.0 × 105 L m−3 h−1 for layered and turbulent oil/water mixtures, respectively. Moreover, the as-prepared polyurethane foams can separate the oil-in-water emulsions with a separation efficiency of >99% and a separation flux of 2.7 × 105 L m−3 h−1. The large-scale preparation of hydrophobic polyurethane foams by this method confirmed their potential in practical applications.

Hydrophobic porous polymeric materials have attracted great interests recently as potential candicate for oil-water separation due to their high selectivity and sorption capacity. Herein, we present a green, simple and cost-effective method to change hydrophilic melamine formaldehyde (MF) foam to hydrophobic carbon nanotubes (CNTs) coated MF foam through an immersion process. The MF foam was produced from the MF resin which was synthesized in a laboratory by a condensation reaction between melamine and formaldehyde under alkaline condition with a molar ratio of melamine to formaldehyde of 1:3. The MF foam has an open-cell structure with the average pore diameter of 350 m, density of 25 kg •m-3 and porosity of 98 %. The as-prepared CNTs-coated MF foam exhibits high sorption capacity (23–-66 g/g) for oils and organic solvents, good recyclability and high selectivity.

Based on the theory of oil-water centrifugal separation, a novel oil-water helix separator for generating helix separation flow field by helical guide vanes is designed. The test prototypes with di...

Inspired by nature, Janus membranes with unidirectional liquid transport (ULT) were developed to be used in the fields of fog collection, moisture-wicking fabrics, demulsification, etc. However, the obtained Janus membranes are often unifunctional, and it is still a great challenge to adjust the ULT of Janus membranes for multifunctional applications. Herein, a scalable, low-cost, and machine-washable Janus membrane was developed by combining the cyclic self-assembly of phytic acid and FeIII and a one-side spraying coating of poly(dimethylsiloxane) (PDMS), featuring adjustable ULT upon challenge for multifunctional applications. By controlling the amount of PDMS, the Janus membranes exhibit two different performances, ULT and switchable permeation. The prepared Janus membranes achieved an excellent moisture-wicking fabric (1.6× the water evaporation rate of cotton), fast water collection under oil, rapid demulsification, and the efficient separation of an oil/water mixture. The separation efficiency of a light or heavy oil from water was higher than 99.9% even after 10 separation cycles, and the flux of the separation was up to 2.55 × 104 or 2.38 × 104 L m-2 h-1, respectively. This study could provide an idea for the development of more Janus membranes with adjustable performances to realize multifunctional applications.

In this study, a series of octyl-modified alginates (H-SA) were successfully synthesized via covalently coupling various amounts of octylamine (OA) to sodium alginate (SA) and was then characterized by multiple techniques. Despite its poor surface tension reduction effectiveness, the synthesized H-SA could effectively reduce the oil-water interfacial tension. Therefore, the H-SA was used to emulsify various types of oils, and their emulsification performances were evaluated in terms of the oil droplet size and emulsion viscosity after emulsification. It was found that the emulsifying efficiency was enhanced with increasing octyl substitution degree (OSD) over the studied range. Moreover, the influences of pH value and salt content on the emulsifying efficiency were also investigated in detail. Overall, H-SA can be easily synthesized, providing a promising biodegradable emulsifier for the oil emulsification in an aqueous environment.

Development of porous materials with anti-fouling and remote controllability is highly desired for oil-water separation application yet still challenging. Herein, to address this challenge, a sponge with unusual superhydrophilicity/superoleophobicity and magnetic property was fabricated through a dip-coating process. To exploit its superhydrophilic/superoleophobic property, the obtained sponge was used as a reusable water sorbent scaffold to collect water from bulk oils without absorbing any oil. Owing to its magnetic property, the sponge was manipulated remotely by a magnet without touching it directly during the whole water collection process, which could potentially lower the cost of the water collection process. Apart from acting as a water-absorbing material, the sponge can also be used as affiliation material to separate water from oil-water mixture and oil in water emulsion selectively, when fixed into a cone funnel. This research provides a key addition to the field of oil-water separation materials.

Stratified flow is a common occurrence for various internal flow based industrial multiphase flow patterns. This involves fully or partially well-defined interface which continuously evolve with space and time. Hence stratified flow analysis essentially involves proper interface capturing approach. The present work focuses on the numerical analysis of oil-water stratified pattern using the Coupled level set and volume of fluid method (CLSVOF) in ANSYS Fluent in a two-dimensional channel. The work involves predicting the effect of density ratio, kinematic viscosity and surface tension coefficient on the mixture velocity and total pressure changes. At outset, the final conclusions may be gainfully employed in oil transportation pipeline, chemical industries and in pipeline flow control administration, etc.

Effective oil-water separation is a continuous pursuit, not only for scientific research but also for engineering application, because oil spills are causing the great pollution in the current ocean environment. Here we reported a superhydrophobic coated-mesh, where the coatings were composed of fluorinated silica (F-SiO2) and polydimethylsiloxane (PDMS), demonstrating the excellent oil-water separation ability towards various organic liquids. The introduction of F-SiO2 could well induce a certain extent of microscopic roughness, leading to the remarkable water repellence. The resultant coatings exhibited the robust superhydrophobicity with the water contact angle reaching 155.9°±1.0°. On this basis, the pore size of polyethylene terephthalate (PET) mesh materials (as a substrate) was mainly discussed with the great oil-water separation efficiency of as high as 98% towards various organic liquids. Also, under the assistance of physical model, it was confirmed that there was a mechanical relation between pore size and organic liquids, where the main connotation was the matching issue of surface tension of organic liquids with the geometrical mechanic (induced by the pore size of the superhydrophobic coated-mesh). This work on the size effect of superhydrophobic coated-mesh materials on various organic liquids is beneficial to the design and manufacture of ideal oil-water separation materials.

Oily wastewater seriously pollutes the environment, and is difficult to separate. In this work, superhydrophobic cotton fabrics were fabricated through the combination of micro–nano-binary structure of polydopamine (PDA) and grafting of octadecylamine (ODA). Herein, fluorine-free compounds were used. The PDA binary structure was rapidly deposited on cotton fabric under the catalysis of metal salts and oxidants. Then, the ODA was grafted onto the cotton fabric through Schiff base reaction with o-quinone formed by oxidation of the catechol structure of PDA, which covered the surface of PDA coated cotton fabric. The superhydrophobic cotton fabric with contact angle up to 163.7° and scroll angle around 9° was obtained. Due to the excellent adhesion of polydopamine, the superhydrophobic cotton fabric demonstrated great stability and durability under a variety of harsh environmental conditions. After coating the polyurethane (PU) sponge with the prepared superhydrophobic cotton fabric, an oil absorbing bag was made and it showed good oil–water separation even after being reused 20 times, and the prepared cotton fabric also had excellent self-cleaning performance. This facile strategy of preparation of superhydrophobic materials for continuous oil–water separation is quick, efficient and environmentally friendly, which has great prospect for application in removal of marine oil spills.

The novel high hydrophobic graphene/vinyl-functionalized SiO2 composites were prepared via self-assembly of graphene sheets on the surface of vinyl-functionalized silica (VF-SiO2) nanoparticles. Th...

Inspired by the strong adhesion of mussels, a super-hydrophobic sponge was designed and prepared by a simple and inexpensive one-pot solution immersion method. The prepared superhydrophobic sponge can not only efficiently separate the oil–water mixture, more importantly, but also remove volatile organic compounds in the atmospheric environment. Polydopamine (PDA) enables polydivinylbenzene (PDVB) particles to be firmly and tightly attached to the melamine sponge skeleton, thereby making the hydrophilic sponge superhydrophobic and providing adsorption sites for volatile organic compounds in the air. The synergy enables the sponge/PDA/PDVB to quickly adsorb oils and organic substances, and it has high stability and capacity even after 20 cycles. In addition, superhydrophobic sponges can still perform outstanding adsorption performance even under highly acidic and alkaline environments. Meanwhile, the static adsorption capacity of the sponge/PDA/PDVB for gaseous toluene is 5.7 times that of activated carbon. Compared with pure PDVB, the super-hydrophobic sponge in the dynamic experiment has a penetration time increased from 6 to 390 min, which is 65 times longer than that of the PDVB, and the adsorption performance has been greatly improved. Therefore, our strategy may achieve a new effect, which can quickly and easily separate oil–water mixtures and remove volatile gaseous pollutants, and it can provide potential options for practical applications

Polyimide (PI) aerogels have great potential in oil/water separation field, but the extreme volume shrinkage during the fabrication still remains challenging. Herein, a simple yet efficient strategy of incorporating methylcellulose (MC) in PI aerogels is proposed. The MC/PI composite aerogels were fabricated by freeze-drying plus thermal imidization with subsequent trimethylchlorosilane (TMCS) functionalization. The results revealed that MC entered the skeleton of aerogels and strengthened it effectively by promoting the formation of robust and complete 3D porous structure, and the defects of as-prepared aerogels were eliminated when the proportion of MC was beyond 10 wt%. After modification with TMCS, the water contact angle of aerogels increased significantly by 30°–40°, and the functionalized aerogels showed excellent oil absorption capacity up to 28.44 g/g. The outstanding oil absorbency and simple process for separating oil and water with MC/PI composite aerogels are promising candidates in the field of oil/water separation.

SummaryAccurate quantification of phase behavior of solvent/heavy-oil/bitumen/water systems at high pressures and elevated temperatures is of high significance for the design of vapor extraction, cyclic solvent injection, expanding-solvent steam-assisted gravity drainage (ES-SAGD), and hot-solvent injection processes. The relevant experimental data and theoretical analyses are still insufficient for achieving a reliable model. This is especially true when the system temperatures approach or exceed the critical temperatures of the solvents used (i.e., when the solvent density is large enough).This study provides new experimental measurements of the phase behavior of propane (C3H8)/carbon dioxide (CO2)/heavy-oil/water systems at pressures up to 20 MPa and temperatures up to 432.3 K. More specifically, four feeds of C3H8/CO2/heavy-oil/water systems are used to conduct constant composition expansion (CCE) tests, during which the heights of the entire fluid system (i.e., total volume) and each phase are recorded at each pressure and temperature, respectively. Theoretically, a dynamic volume analysis (DVA) of the measured data is proposed for the first time to quantify each phase, provided that the assumption for vapor phase is valid and that the vapor and oleic phase densities can be accurately calculated. By tuning the binary interaction parameter (BIP) for solvent/heavy-oil pairs (denoted as BIPS−HO) to match the total volume, the height of the vapor/oleic (V/L) interface can be matched as well. By using the tuned BIPS−HO, the total volume and height of the V/L interface of C3H8/CO2/heavy-oil/water systems can be accurately predicted, no matter whether the solvent solubility in water is low (i.e., C3H8) or high (i.e., CO2). This DVA can be used to determine/evaluate the solvent solubility, saturation pressure/phase boundary, and phase volume/density accurately in a large temperature and pressure range. The newly proposed DVA method is also used to reproduce the experimental measurements collected from the literature, including phase-volume fractions, solvent solubility, and saturation pressure. In addition, the DVA method can serve as a tool to check whether the experimental measurements are reliable or not.

In this work, we reported a cuprous oxide/polypropylene (Cu2O/PP) fibrous membrane with superhydrophobic (WCA = 151.8°±2.1°) and superlipophilic (OCA = 0°) for highly efficient oil/water separation...

With the increasing occurrences of industrial oily wastewater emissions and oil spills, considerable efforts have been made to develop superhydrophobic materials for oil–water separation. Herein, we report a facile dipping-UV curing approach to fabricate superhydrophobic organosilicon/silica hybrid coating with crosslinked network structure on cotton fabric via thiol-ene reaction between thiol-functionalized silica nanoparticles (SH-SiO2 NPs) and acryloyloxy-terminated polydimethylsiloxane (A-PDMS-A). With the optimized mass ratio of SH-SiO2 NPs to A-PDMS-A at 0.2, the water contact angle of the fabric reached 155° and the water sliding angle was 8°, exhibiting excellent water repellency. Furthermore, the superhydrophobic cotton fabric possessed self-cleaning ability and good surface stability. In addition, the fabric was successfully applied for effective oil–water separation, and the separation efficiency reached up to 99.06%. Even after 15 cycles, the separation efficiency still maintained 98.93%, demonstrating excellent reusability. Our findings stand out as a new tool to fabricate UV-curable superhydrophobic coating on cotton fabric for efficient oil–water separation.

In this paper, a facile and efficient approach to robust and durable superhydrophobic cotton fabric was presented via in situ CuO deposition and stearic acid (STA) coating. The combined effects of both rough structure and low surface energy endowed cotton fabric (Cot) with superhydrophobicity, water repellency, and self-cleaning property. Moreover, the as-prepared fabric (Cot–CuO–STA) could keep its robust superhydrophobicity under harsh environmental conditions of acidic, alkaline and salt solutions, high temperature, mechanical abrasion and washing. Importantly, the obtained Cot–CuO–STA with WCA of 156.5° had great potential in oil/water separation with high separation efficiency of up to 98.7% for various oils (dichloromethane, trichloromethane, soybean oil, and n-heptane). Further, fascinating permeate flux (more than 1800 L.m−2.h−1) and remarkable recyclability made Cot–CuO–STA a promising application in oil-contaminated water treatment and marine spilt oil cleanup. Robust and durable superhydrophobic cotton fabric was fabricated for oil/water separation via a facile and efficient route. The resultant fabric exhibited remarkable separation efficiency for different kinds of oils, fascinating permeate flux, and excellent recyclability.

The influence of density of amino groups, nanoparticles dimension and pH on the interaction between end-functionalized polymers and nanoparticles was extensively investigated in this study. PS–NH2 and H2N–PS–NH2 were prepared using reversible addition–fragmentation chain transfer polymerization and atom transfer radical polymerization. Zero-dimensional carbon dots with sulfonate groups, one-dimensional cellulose nanocrystals with sulfate groups and two-dimensional graphene with sulfonate groups in the aqueous phase were added into the toluene phase containing the aminated PS. The results indicate that aminated PS exhibited the strongest interfacial activity after compounding with sulfonated nanoparticles at a pH of 3. PS ended with two amino groups performed better in reducing the water/toluene interfacial tension than PS ended with only one amino group. The dimension of sulfonated nanoparticles also contributed significantly to the reduction in the water/toluene interfacial tension. The minimal interfacial tension was 4.49 mN/m after compounding PS–NH2 with sulfonated zero-dimensional carbon dots.

Janus graphene oxide (GO) usually refers to a unique two-dimensional material with asymmetric surface chemistries on opposite faces of the sheets. Herein, we propose a facile and efficient method to fabricate Janus-like GO (JGO) with a novel asymmetric structure along the faces of the sheets. Unlike the traditional post-synthesis of double-faced Janus GO based on pre-prepared GO, the novel JGO with a randomly distributed asymmetric oxidation structure along the sheet face can be achieved by a simple ultrasonic treatment on partially oxidized graphene. The asymmetric oxidation structure along the sheet face of our Janus GO was confirmed by confocal micro-Raman imaging and analysis of height profiles by atomic force microscopy. Due to the asymmetric oxidation structure, the as-prepared JGO has amphiphilic characteristics, with hydrophilicity on one side of the sheet and hydrophobicity on the other side, leading to an eyelash-like liquid crystal alignment at the oil/water interface. The perpendicular alignment rather than the parallel orientation behavior of GO liquid crystals at the oil/water interface further confirms the asymmetric structure of our JGO along the face graphene sheets. The simple approach and a new class of JGO proposed herein provide a new insight into understanding the asymmetric chemistry of graphene.

Sustainable and robust superhydrophobic cotton fabrics were fabricated using a coating solution that consisted of a novel castor oil-based thiolated oligomer (CO-SH), octavinyl polyhedron oligomeri...

Drop-interface interaction under an electric field is relevant in commercial desalters wherein water droplets suspended in oil coalesce under an electric field, move down under gravity, and eventually coalesce with the water pool at the bottom of the desalter. In this work, we report our observation that the transition from coalescence to partial coalescence can be described by a critical electrocapillary number and is independent of the Ohnesorge number. On the other hand, the partial coalescence to noncoalescence transition depends upon both the electrocapillary number and the Ohnesorge number. The bridge during partial coalescence exhibits an electrocapillary-number-independent growth and collapse dynamics, although the transition time for growth to collapse depends upon the electrocapillary number (CaE). Lastly, contrary to previous studies, our results indicate that the secondary droplet size varies as CaE3/2 unlike the CaE1/2 reported in the literature.

An efficient continuous purification strategy based on rice straw (RS) composites for oil/water separation and removal of heavy metal ions is reported. Superhydrophobic octadecanoyl bonded and polystyrene grafted RS (C18-RS-g-PS) and aminated poly(styrene-co-acrylonitrile) grafted RS (RS-g-APSAN) were prepared by surface-initiated ATRP for the treatment of heavy metal ions contained oil/water mixtures. The efficiency of oil/water separation and subsequent adsorption behaviors of heavy metal ions including contact time, pH effect, adsorption kinetics and adsorption isotherms were evaluated systematically. The results showed that C18-RS-g-PS possessed high superhydrophobicity with water contact angle of 154° and demonstrated good separation efficiency of above 98%. Regarding above separated water with contaminated heavy metal ions, RS-g-APSAN displayed high adsorption capacity towards Pb2+, Cu2+, Zn2+, and Ni2+ with adsorption capacities of 662.9, 248.8, 110.1, and 94.9 mg/g, respectively. The superior comprehensive performance of RS composites makes them potential ideal candidates for continuous purification of oily wastewater.

It is a challenge to fabricate three-dimensional carbon aerogels based on natural renewable resources with stability, flexibility, and versatility. Here, an ultralight, elastic, and hydrophobic mul...

Velocity is an important parameter for fluid flow characteristics in profile logging. Particle tracking velocimetry (PTV) technology is often used to study the flow characteristics of oil wells with low flow velocity and high water cut, and the key to PTV technology is particle matching. The existing particle matching algorithms of PTV technology do not meet the matching demands of oil drops in the oil phase velocity measurement of oil-water two-phase flow with low velocity and high water cut. To raise the particle matching precision, we improved the particle matching algorithm from the oriented FAST and the rotated BRIEF (ORB) feature description and the random sample consensus (RANSAC) algorithm. The simulation and experiment were carried out. Simulation results show that the improved algorithm not only increases the number of matching points but also reduces the computation. The experiment shows that the improved algorithm in this paper not only reduces the computation of the feature description process, reaching half of the computation amount of the original algorithm, but also increases the number of matching results, thus improving the measurement accuracy of oil phase velocity. Compared with the SIFT algorithm and the ORB algorithm, the improved algorithm has the largest number of matching point pairs. And the variation coefficient of this algorithm is 0.039, which indicates that the algorithm is stable. The mean error of oil phase velocity measurement of the improved algorithm is 1.20 %, and the maximum error is 6.16 %, which is much lower than the maximum error of PTV, which is 25.89 %. The improved algorithm overcomes the high computation cost of the SIFT algorithm and achieves the precision of the SIFT algorithm. Therefore, this study contributes to the improvement of the measurement accuracy of oil phase velocity and provides reliable production logging data for oilfield.

Frequent oil spill accidents and industrial wastewater discharge result in severe health and ecological problems. Advanced materials with superwettability have been extensively applied for oil–wate...

Oil sorbent membranes are highly effective materials in combating oil spills. Recent technological advancements in membrane preparations permit higher oil-sorption efficiency and easier oil recover...

Bacteria are important examples of active or self-propelled colloids. Because of their directed motion, they accumulate near interfaces. There, they can become trapped and swim adjacent to the inte...

The interfacial assembly process and configuration of the pseudogemini surfactant fabricated by sodium dodecyl benzene sulfonate (SDBS) and 4,4'-oxydianilinium chloride (ODC) were studied using quantum mechanical calculations and molecular dynamics (MD) simulations. The MD simulation results revealed that SDBS and ODC showed the vertical and horizontal arrangements at the oil/water interface, respectively, and the interfacial assembled configuration presented an unexpected "H" shape rather than the traditional "U" shape. The radial distribution functions between the head groups and water molecules were employed to explore the effects of the surrounding water molecules on the SDBS/ODC interaction. Furthermore, the results of the nonbonded interaction calculations and the reduced density gradient method directly confirmed that the cation-π interaction should be responsible for the SDBS/ODC assembly mechanism and the final configuration at the oil/water interface.

Polylactic acid (PLA) is one of the most suitable candidates for environmental pollution treatment because of its biodegradability which will not cause secondary pollution to the environment after application. However, there is still a lack of a green and facile way to prepare PLA oil-water separation materials. In this work, a water-assisted thermally induced phase separation method for the preparation of superhydrophobic PLA oil-water separation material with honeycomb-like structures is reported. The PLA material shows great ability in application and could adsorb 27.3 times oil to its own weight. In addition, it could also be applicated as a filter with excellent efficiency (50.9 m3 m−2 h-1).

This study investigates the performance of oil-water separation experimentally using two methods: gravity separation, and electrolysis separation. A factorial design experiment was conducted for gr...

Summary Boscán is a giant multibillion-barrel heavy-oil (10.5 °API and asphaltic) field in Venezuela. Although a large part of the field is on primary production with a low recovery factor ( Water injection in such heavy oil was previously considered not effective by the industry because of adverse mobility ratio. However, water injection for pressure maintenance (WIPM) was successfully implemented using a new pattern configuration, a pseudo-1-3-1 inverted- spot pattern (an additional row of producers between conventional-pattern rows). Field-data and reservoir-simulation models show increased reservoir pressure up to the second row of producers from the injector. The pressure support is used to significantly improve recovery using the unique configuration at low water cut. WIPM has already resulted in significant reserves addition. Current production from water-injection areas is approximately 40,000 MBOPD (or approximately 47% of field production). However, it is estimated that because of high oil viscosity, a significant amount of oil remains bypassed in the WIPM area. An infill opportunity was identified from an integrated reservoir-management study that included detailed WIPM data analysis and dynamic (mechanistic and full-field) modeling. A unique infill configuration is proposed that conceptually uses the current injectors with an additional row of producers between the existing first and second row of the producers. This configuration has the potential to economically unlock millions of barrels of bypassed oil and significantly increase recovery in this prolific heavy-oil field. This study provides insights into HMRWF behavior, evaluating the relative effect of displacement vs. pressure. The unique and novel infill configuration can be used to improve recovery, a step vital to monetize this large resource in the low-price environment.

In this work, we proposed a mild and fluorine-free strategy for fabricating robust superhydrophobic coatings with TiO2, 3-mercaptopropyltriethoxysilane (MPTS) and polyhedral oligomeric silsesquioxanes using dip-coating and thiol-ene click reaction. The modified cotton exhibited superb superhydrophobicity with a WCA of 157.6°, which showed anti-wetting property in both water and air. Moreover, the durability of the treated cotton against acid and alkaline solutions, different temperatures, abrasion and peeling tests was verified. The highlight is the dual self-cleaning afforded by superhydrophobicity and photocatalytic degradation. The oil red O was adopted as organic pollutant model and could be decomposed completely with the aid of resultant coating after UV irradiation for 3 h. In addition, the modified cotton could be used as filter material and has the potential in the application of oil–water separation. After seven separation cycles, the separation efficiency still maintained 99.0%, while the WCA of cotton kept as high as 154.6°. Therefore, the above-mentioned features demonstrated that this fluorine-free method could reduce the usage of long-chain fluorinated polymers and prepare superhydrophobic cotton which could be applied in self-cleaning as well as oil–water separation fields.

To deal with the demulsification of O/W emulsions, a novel kind of core–shell structural amphiphilic soft matter, HPEI-g-Cn (n = 10, 12, 14, 16, 18), with hyperbranched polyethyleneimine (HPEI) as the core and fatty acid chain Cn as the shell, is designed and synthesized. With the existence of amphiphilic HPEI-g-Cn, O/W emulsions can be thoroughly separated into two phases with a clear oil–water interface to reach demulsification equilibrium within 40 min. The oil removal ratio can exceed 99.9% under the addition of 40 ppm in simulative emulsions, and simultaneously the water content in the oil phase is less than 0.01%. This demulsifier can also contribute to excellent separation efficiency (up to 99.9%) for O/W emulsions from two China's oilfields, and even for heavy oil emulsions. More importantly, it is noted that the HPEI-g-Cn demulsifiers after demulsification are evenly and tightly dispersed at the oil–water interface as shown by wide-angle X-ray scattering (WAXS) and cryo-electron microscopy (cryo-EM), which is beneficial to the subsequent recovery and utilization. With eco-friendly characteristics, outstanding demulsification performance and promising recyclability, the amphiphilic macromolecules HPEI-g-Cn as special soft matter display great promise to achieve industrial applications in the future.

Membrane filtration and absorption strategies based on superwetting surfaces for oil–water separation have regained tremendous attention due to their being low cost, highly efficient and environmentally friendly. Besides the usual superhydrophobic, superhydrophilic/underwater superoleophobic and dual superlyophobic surfaces, very novel and unprecedented surfaces with special extreme wetting behavior have been widely used in oil–water separation. In this review, novel surfaces with extreme wetting behavior for oil-water separation reported over the past three years including superhydrophilic–superoleophobic, superamphiphobic, superhydrophilic-underoil superhydrophilic, underoil superhydrophobic-underwater superoleophobic and liquid-infused surfaces, as well as oil–water separation mechanisms, separation approaches and design principles for obtaining novel superwetting membranes, are systematically summarized. The most common problems in the process of oil–water separation-membrane pollution and solutions are discussed. In addition, the selection of substrates, the swelling of hydrophilic membranes and the wettability conversion of intelligent response membranes are analyzed. The current trends, challenges and future research opportunities are also proposed, providing a road map for the future development of high-efficiency oil–water separation technology.

A novel ultralight superhydrophobic-superoleophilic hybrid Carbon Nanotubes (CNTs) film with double-layer structures is fabricated by using vacuum filtration method. The CNTs film can separate various surfactant-stabilized water-in-oil emulsions with a separation efficiency higher than 99.3%. Moreover, the hybrid films can be regenerated through a simple and rapid combustion process within 2 s. In addition, the CNTs film still retains good hydrophobic properties under the conditions of physical abrasion, and strong acidic and alkaline solutions, which shows the excellent durability. The hybrid CNTs film is ultralight, stable, and easily stored and reused. The outstanding features of the obtained CNTs films we present here may find many important applications in various fields like oil purification and wastewater treatment.

The separation of oil-water mixtures has attracted widespread attention for addressing increased oil spillage and oil-polluted water. In this study, a novel and low-cost oil-water separation coatin...

The use of chemical dispersants is a well-established approach to oil spill remediation where surfactants in an appropriate solvent are contacted with the oil to reduce the oil-water interfacial tension and create small oil droplets capable of being sustained in the water column. Dispersant formulations typically include organic solvents, and to minimize environmental impacts of dispersant use and avoid surfactant wastage it is beneficial to use water-based systems and target the oil-water interface. The approach here involves the tubular clay minerals known as halloysite nanotubes (HNTs) that serve as nanosized reservoir for surfactants. Such particles generate Pickering emulsions with oil, and the release of surfactant reduces the interfacial tension to extremely low values allowing small droplets to be formed that are colloidally stable in the water column. We report new findings on engineering the surfactant-loaded halloysite nanotubes to be stimuli responsive such that the release of surfactant is triggered by contact with oil. This is achieved by forming a thin coating of wax to stopper the nanotubes to prevent the premature release of surfactant. Surfactant release only occurs when the wax dissolves upon contact with oil. The system thus represents an environmentally benign approach where the wax coated HNTs are dispersed in an aqueous solvent and delivered to an oil spill whereupon they release surfactant to the oil-water interface upon contact with oil.