Immiscible Organic Liquid Research Articles

Facile preparation of superhydrophilic and superoleophobic sand for efficient oil-water separation

Superhydrophilic-superoleophobic materials possess unique advantages in oil-water separation due to their water permeability and oil repellency. In this study, superhydrophilic-superoleophobic sand (CQS) was prepared using a facile and rapid mixing-drying coating method. Quartz sand was modified with polydopamine (PDA) as the hydrophilic binding agent, fluorosurfactant (FS-50) as the oleophobic agent, and CaCO3/SiO2 to construct hierarchical surface roughness. The CQS exhibited a water contact angle of 0° and an oil contact angle of 154°, which resulted in a slightly increased water adhesion capacity and a significantly reduced oil adhesion capacity. Owing to its selective wettability towards oil and water, the CQS was capable of directly separating immiscible oil-water mixtures and oil-in-water emulsions with high separation efficiency (99.5 % and 98.5 %, respectively), driven by gravity. Moreover, immiscible oil/oil mixtures could be effectively separated by the CQS as well, expanding its application to separating immiscible organic liquids with different polarities. Additionally, the CQS demonstrated good reusability and superior stability against acid, alkali, salt, hot water and mechanical abrasion. These properties ensured its applicability in complex environments. The CQS, with exceptional separation capability and stability, holds promising prospects for future applications in related separation field.

Diversified separations of immiscible organic liquids by a modification of superwettable supramolecular framework composite on porous support

Superwetting porous materials possessing wide applicability and responsiveness are becoming highly desired for the needs of the separation of immiscible liquid mixtures with less difference in surface tension during the treatment of wastes. In targeting this purpose, we propose a strategy to regulate the wettability of a sponge by coating a supramolecular framework (SF) bearing tunable wetting states under the assistance of polycaprolactone. This SF assembly-modified porous support demonstrates the under-liquid dual lyophobicity for polar liquids under nonpolar ones and for nonpolar liquids under polar ones via a simple in-situ adjustment of intermediate fluids. Depending on the capillary force of nanopores and amphiphilic components existing in the SF assembly, the switchable surface-modified sponge connecting to a pump quickly suction lyophilic organic liquids either located on the top or bottom phase despite touching the lyophobic liquids. Moreover, in-situ modulated filtrations to the emulsions comprising polar and nonpolar liquids are achieved with high efficiency (greater than 94.8 %) and flux (up to 9261.2 L m−2 h−1). Importantly, the suction and filtration separations are also available for organic liquid pairs with a high viscosity. The reversible interconversion between nonpolar and polar liquids is achieved and can be recycled several times with undiminished performance.

Silk-derived nitrogen-doped porous carbon electrodes with enhanced ionic conductivity for high-performance supercapacitors

Supercapacitors are attracting extensive attention in energy storage fields thanks to their high safety, cost-effectiveness, and environmental friendliness. The carbon materials, especially for the porous carbon materials derived from renewable biomass materials, are important electrode materials with cost-effective feature for supercapacitors. However, the inferior ionic conductivity of biomass materials inhibits their electrochemical performance in energy storage devices. Herein, an immiscible liquid-mediated method is provided to improve the ionic conductivity of silk-derived nitrogen-doped porous carbon (NPC) electrodes. Natural Bombyx mori (silkworm) silk is used as a carbon source for the preparation of electrode of supercapacitor. Further introducing immiscible organic liquid into the NPCs promotes the ion transport in the inner pores of the electrodes. With the assistance of organic liquid, the supercapacitor presents a specific capacitance of 565.3 F g−1 at a current density of 1 A g−1. The supercapacitor shows the maximum specific energy and power density of 26.2 Wh kg−1 and 263.9 W kg−1, and holds a capacitance retention of approximately 93.3% after 10 000 cycles. This work provides a facile method for the rational design of carbon material derived from biomass material to fabricate electrode with high ionic conductivity, and the strategy will be extendable to other biomass materials for a wide range of applications.

Interfacial polymerization at unconventional interfaces: an emerging strategy to tailor thin-film composite membranes.

Interfacial polymerization is a well-known process to synthesize separation layers for thin film composite membranes at an immiscible organic liquid-aqueous liquid interface. The organic-aqueous interface determines the diffusion dynamics of monomers and the chemical environment for polymerization, exerting a critical influence on the formation of polymer thin films. This review summarizes recent advances in tailoring interfacial polymerization using interfaces beyond the conventional alkane-water interface to achieve high-performance separation films with designed structures. Diverse liquid-liquid interfaces are introduced for synthesizing separation films by adding co-solvents into the organic phase and/or the aqueous phase, respectively, or by replacing one of the liquid phases with other solvents. Innovative liquid-gel and liquid-gas interfaces are then summarized for the synthesis of polymer thin films for separation. Novel strategies to form reaction interfaces, such as spray-coating, are also presented and discussed. In addition, we discuss the details of how a physically or chemically patterned substrate affects interfacial polymerization. Finally, the potential of unconventional interfaces in interfacial polymerization is forecast with both challenges and opportunities.

A Stay-at-Home Chemistry Activity to Illustrate Intermolecular Forces

Water and an immiscible organic liquid are placed in a small plastic bottle. Ten small pieces of a notecard which is shaded on one side by crayon or pencil (graphite or colored) are cut out and placed inside the bottle. After capping and shaking, the notecard pieces float at the liquid–liquid interface with the shaded side facing the nonpolar organic solvent. This activity uses simple and easily obtained consumer materials and has been used with students from elementary school through introductory college to illustrate the concept of noncovalent (intermolecular) forces.

Viscoelastic effects of immiscible liquid–liquid displacement in microchannels with bends

The displacement flow of an organic Newtonian fluid by a pure viscoelastic aqueous solution is experimentally investigated inside a circular microchannel of 200 μm. Displacement is commonly encountered in many industrial applications, from cleaning and decontamination to enhanced oil recovery. In this study, a pure viscoelastic fluid with no shear-thinning properties (known as Boger fluid) made up of polyethylene oxide, polyethylene glycol, and zinc chloride is used to displace an immiscible organic liquid (silicone oil). The results were compared against those from displacement with a Newtonian fluid of similar density and viscosity as the viscoelastic one. High-speed imaging is used to track both the residual film thickness of the organic phase and the interface deformations during displacement. It is found that the Boger fluid displacing phase produces a thinner displaced phase film compared to the Newtonian fluid, particularly at high capillary numbers. A correlation is proposed for the film thickness, which includes the Weissenberg number for the viscoelastic case. After the displacement front, the interface becomes unstable with two modes of instability identified. In the case of the Boger fluid, the two modes of instability are core shifting, which is also present in the Newtonian case, and a periodic instability from the elastic stresses during displacement. Additionally, the shape of the interfacial instabilities switches freely from asymmetric to axisymmetric ones throughout the flow. The frequency of the periodic instabilities increases with the displacing phase flow rate. It was also found that microchannel bends downstream of the observation point affect the shape and frequency of the instabilities.

Mediator effect-assisted dual superlyophobic surface: PPY@Ni–Co LDH@PEEK textile for high performance separation of oil/water mixtures and immiscible organic liquids

Dual superlyophobic surface is of great value for selective rejections of oil and water, but it is still a formidable task. In this work, we develop a PPY and polygonal Ni–Co LDH nanosheets modified PEEK textile with dual superlyophobicity and great switchable stability. The membrane can separate not only oil/water mixtures but also immiscible organic liquids with different PSE. Moreover, attributed to the ‘mediator effect’ of ethanol, the membrane exhibits ultra-high rejection heights for low PSE organic liquids (80 cm for n-hexane). Last but not least, the membrane remained the high strengths, good solvent resistances, corrosion preventions and thermal stabilities of PPY and PEEK fibre.

ZnO Nanoneedle-Modified PEEK Fiber Felt for Improving Anti-fouling Performance of Oil/Water Separation.

Membrane separation has been considered to be the most effective decontamination method for oily waste water. The most significant point of membrane separation is the resistance against membrane fouling. Fabricating hierarchical architectures on the membrane surface is an available approach to improving its anti-fouling property. In this study, ZnO nanoneedles were successfully anchored onto surface-sulfonated poly(ether-ether-ketone) (PEEK) felt via UV/ozone cleaning and hydrothermal synthesis. The modified felt (PEEK-f-Z) showed much better anti-fouling properties and far higher rejection height (33 cm) than the unmodified felt (17 cm) with a separation efficiency up to 99.99%. The enhanced separation properties could be attributed to the stronger water locking capability of the hierarchical architectures on the surface. Furthermore, benefiting from the great chemical stability of PEEK substrates and ZnO nanoneedles, the as-prepared membrane exhibited admirable solvent resistance, mechanical strength, and thermal stability. As a result, PEEK-f-Z could even separate immiscible organic liquids with different polarities and collect hot water from the oil/water mixture, promising to be used under severe conditions.

High-strength corrosion resistant membranes for the separation of oil/water mixtures and immiscible oil mixtures based on PEEK

Nowadays, PEEK, as a kind of high performance polymer characterized with high strength, great corrosion resistance and thermal stability is regarded as a promising membrane material. In this study, PEEK fibers were prepared by melt spinning and then woven into textiles. Furthermore, interface reduction was utilized to give a more hydrophilic textile (PEEK-OH textile). In addition, considering to make full use of the huge membrane pores of the textile, a liquid-infused method was employed to regulate its surface energy and to establish an under-water oleophobic surface. Surprisingly, PEEK-OH textile functioned in not only oil/water separation, but also separating immiscible organic liquids with different polarities just through a liquid-infused approach. More importantly, we firstly introduced ‘mediator effect’ during the pre-wetting process before separation, taking ethanol as a ‘mediator’. Furthermore, according to the ‘mediator effect’, an under-oil hydrophobic membrane was established using dichloromethane as a ‘mediator’. As we expected, both PEEK and PEEK-OH textiles revealed features such as high flux, admirable selectivity, competitive strength, great corrosion resistance and thermal stability, herein, they promised to be used for oil/water separation in practical environment.

NAPL-water interfacial area as a function of fluid saturation measured with the interfacial partitioning tracer test method

The presence of organic immiscible liquids such as chlorinated solvents and fuels continues to be a primary source of risk for many hazardous waste sites. In this study, the standard miscible-displacement interfacial partitioning tracer test (IPTT) method was used for the first time to measure NAPL-water interfacial areas for a range of saturations. Multiple measurements were conducted for a natural quartz sand, with tetrachloroethene as the representative NAPL. The interfacial areas increased with decreasing water saturation. The measurements compared well to interfacial areas measured for the same sand with two alternative tracer methods, the mass-distribution batch method and the two-phase flow method. Measurements obtained with all three tracer-based methods exhibit a relatively large degree of variability. Thus, it is important to employ replication when using these methods. In contrast, interfacial areas measured with x-ray microtomography exhibit very small variability. However, the measured interfacial areas do not capture the contribution of surface-roughness to film-associated interfacial area. Each method has associated advantages and disadvantages, and it is important to be cognizant of them during their application.

Hierarchical Graphene/Metal-Organic Framework Composites with Tailored Wettability for Separation of Immiscible Liquids.

Membrane filtration is a promising technology for the separation of organic immiscible liquids. Surface topography has a direct impact on the wettability of membranes, and it remains largely unexplored. Here, we introduce on-demand liquid separation by coating porous graphene/metal-organic framework (MOF) composites with tunable wettability on porous substrates. Our results have shown that polydopamine (PDA) coating mediates the controlled growth of MOF nanostructures and subsequent fluorination on the porous graphene framework. Surface topography of the graphene frameworks strongly depends on the loading content of MOF nanostructures. The concurrent control of surface coverage of MOF and surface chemistry allows tailoring of the trapped air fraction underneath the porous graphene frameworks in the range of 0.97 to 0.8. As a result, the surface energy of the graphene/MOF coatings can be programmed to afford the change in surface properties from superamphiphobicity to lyophobicity and the selective penetration of low-surface-energy (SE) liquids and the interception of high-SE liquids were achieved. The tailored wettability of graphene/MOF coatings allows for the separation of liquid mixtures of different ranges of SE, making it a general strategy for complex liquid treatment and chemical purification.

Simulating PFAS transport influenced by rate-limited multi-process retention

The transport of per- and poly-fluoroalkyl substances (PFAS) in the vadose zone is complicated by the fact that multiple mass-transfer processes can contribute to their retention and retardation. In addition, PFAS transport at some sites can be further complicated by the presence of organic immiscible liquids (OIL). Mass-transfer processes are inherently rate limited and, therefore, have the potential to cause nonideal transport of PFAS. The objectives of this research were to: (1) develop a solute-transport model that explicitly accounts for multiple retention processes, including adsorption at air-water and OIL-water interfaces, adsorption by the solid phase, and diffusive mass-transfer between advective and nonadvective domains, and (2) apply the model to measured transport data to delineate which processes are rate limited and contribute to observed nonideal transport. Breakthrough curves for transport of two PFAS and one hydrocarbon surfactant in sand obtained from prior miscible-displacement experiments exhibited nonideal transport. The multiprocess model effectively simulated the measured transport data. The results of the analyses indicate that adsorption at the air-water and OIL-water interface can generally be treated as effectively instantaneous for transport in porous media. The rate limitations associated with solid-phase adsorption and diffusive mass transfer between advective and nonadvective domains were of greater significance.

Underliquid Superlyophobic Copper-Coated Meshes for the Separation of Immiscible Organic Liquid Mixtures.

Superwettable materials have been studied extensively and successfully applied in various forms liquid separation. However, because of low surface tension differences, organic liquids (OLs) exhibit approximate wettability on most of the material surfaces, and the separation of OL mixtures remains a challenge. The current separation method for OL mixtures is mainly dependent on covalent modification to precisely control the surface energy of the membranes, which is extremely complicated. Herein, we demonstrate a novel concept of underliquid superlyophobicity for the separation of immiscible OLs mixtures, which only depend on a relatively stable liquid-repellent interface. Furthermore, the minimum system's free-energy principle was used to explain this wetting behavior. Different from the previous reports, the method of separation of OL mixtures does not involve various low-surface-energy materials, thus it is facile and eco-friendly. Our research provides a general strategy for the efficient separation of immiscible OLs mixtures and is expected to promote the development of superwettable materials for multiphase liquid separation.

Transfer phenomena and interactions of non-aqueous phase liquids in soil and groundwater

Non-aqueous phase liquids are water immiscible organic liquids that are widely encountered in the environment. Exemplar NAPLs include chlorinated hydrocarbon solvents, petroleum products, and waste products such as coal tar. Real-world NAPLs are usually multi-component solution mixtures, and many of the components in NAPLs pose a major challenge to soil, air, and water quality. The purpose of this manuscript is to examine the key physico-chemical properties of NAPLs and how these affect the behaviour of NAPLs in the sub-surface environment.

The influence of molecular structure on the adsorption of PFAS to fluid-fluid interfaces: Using QSPR to predict interfacial adsorption coefficients

Per- and poly-fluoroalkyl substances (PFAS) are emerging contaminants of critical concern for human health risk. Assessing exposure risk requires a thorough understanding of the transport and fate behavior of PFAS in the environment. Adsorption to fluid-fluid interfaces, which include air-water, OIL-water, and air-OIL interfaces (where OIL represents organic immiscible liquid), is a potentially significant retention process for PFAS transport. Fluid-fluid interfacial adsorption coefficients (Ki) are required for use in transport modeling and risk characterization, yet these data are currently not available for the vast majority of PFAS. Surface-tension and interfacial-tension data sets collected from the literature were used to determine interfacial adsorption coefficients for 42 individual PFAS. The PFAS evaluated comprise homologous series of perfluorocarboxylates and perfluorosulfonates, branched perfluoroalkyls, polyfluoroalkyls, alcohol PFAS, and nonionic PFAS. The Ki values vary across eight orders of magnitude, and are a function of molecular structure. The results of quantitative-structure/property-relationship (QSPR) analysis demonstrate that a model employing molar volume (Vm) as a descriptor provides robust predictions of log Ki values for air-water interfacial adsorption of the wide range of PFAS. The model also produced good predictions for a limited set of data for OIL-water interfacial adsorption. The predictive capability of the QSPR model for a wide range of PFAS with greatly varying structures reflects the fact that molar volume provides a reasonable representation of the influence of molecular size on cavity formation/destruction in solution, and thus the hydrophobic-interaction driving force for interfacial adsorption. The QSPR model presented herein provides a means to incorporate the fluid-fluid interfacial adsorption process into transport characterization and risk assessment of PFAS in the environment. This will be particularly relevant for determining PFAS mass flux in the atmosphere, in the vadose zone, in source zones containing organic immiscible liquids, and in water/wastewater treatment systems.

An all superantiwetting surface in water–oil–air systems

Six superantiwetting states, superhydrophobicity, superoleophobicity, underoil superhydrophobicity, underwater superoleophobicity, and underoil and underwater superaerophobicity, are realized on one surface. The all superantiwetting surface can be extended to polar liquid–nonpolar liquid–air systems and be used for on-demand separation of immiscible organic liquids.

A dual underliquid superlyophobic surface in organic media for on-demand separation of immiscible organic liquid mixtures.

High-efficiency on-demand separation of immiscible organic liquid mixtures has rarely been achieved. Herein, we developed a facile and scalable protocol to prepare a practical dual underliquid superlyophobic surface for polar liquid droplets in nonpolar liquid media or nonpolar liquid droplets in polar liquid media. The challenging on-demand organic liquid separation was successfully realized.

Interfacial Tension between Water and Organic Liquid lighter than water by Capillary Rise Method

Interfacial tension between two liquids water and immiscible organic liquid heavier than water has been determined by capillary rise method. The difficulties encountered in the determination of interfacial tension by capillary rise method and how to overcome the difficulties has been discussed. The interfacial tensions between water and organic liquids, carbon tetrachloride, chloroform, nitrobenzene and o-anisidine which are heavier than water have been determined at room temperature (29±1oC) by capillary rise method using a pyrex glass capillary tube of uniform radius. The values of the interfacial tension determined by the capillary rise method were found to be negative indicating that the interfacial tension was acting in the downward direction. The force in the vertically upward direction was considered as positive. The interfacial tensions determined by capillary rise method were in close agreement with the reported values.

Organic Media Superwettability: On-Demand Liquid Separation by Controlling Surface Chemistry.

Superwettability involving water affinity has demonstrated prominent advantages in oil-water separation. However, superwetting surfaces in nonpolar liquid-polar liquid systems are rarely explored for the separation of organic liquids. In this work, a protocol of elaborately controlling surface chemistry is presented to construct dual superlyophobic surfaces for polar or nonpolar liquids in opposite organic media. On two kinds of silver-roughened copper coatings, a polar hydroxyl group is subtly integrated with nonpolar perfluoroalkyl chain at the nanoscale. Prewetted by one organic liquid, the obtained dual superlyophobic mesh can selectively intercept other immiscible organic liquids, realizing high-efficiency on-demand separation. In theory, the dual superlyophobic surfaces in organic media are strongly dependent on their affinity toward polar liquids and the surface roughness. The discovery may promote the development of organic liquid-related interfacial materials.

Cyclable membraneless redox flow batteries based on immiscible liquid electrolytes: Demonstration with all-iron redox chemistry

Membraneless redox flow batteries reported to date are microscale designs that have shown poor capacity retention and cyclability due to reactant crossover. Here, we present a new design of macroscale membraneless redox flow battery capable of recharging and recirculation of the same electrolyte streams for multiple cycles and maintains the advantages of the decoupled power and energy densities. The battery is based on immiscible aqueous anolyte and organic catholyte liquids, which exhibits high capacity retention and columbic efficiency during cycling. The aqueous anolyte consists of iron(II) sulfate (FeSO4) as active species, which is immiscible with the catholyte, having iron(III) acetylacetonate (Fe(acac)3) as active species dissolved in water-immiscible ethyl acetate, supported by ionic liquid (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide). Over 60% of initial discharge capacity was retained and over 80% of columbic efficiency was sustained after 25 cycles in a test flow cell, which is among the highest reported thus far.