Immiscible Liquid-liquid Systems Research Articles

Non-Newtonian nanofluids mediated 15-fold enhancement of mass transfer for two-phase flow systems in microchannel

Microfluidic systems have been more popular in recent years because of its multifunctional advantages, such as the higher level of process intensification. The mass-transfer properties can further be improved by the presence of the slug flow regime in the microdomain for biphasic flow systems. Microdomain, geometrical considerations, non-Newtonian fluid and nanofluid have been independently being investigated as a tool of process intensification. To the best of our understanding, the four-in-one method of process intensification has not been studied till date hence, new systems are being investigated to bridge the gap. In this work, we describe the combination of three enhancing factors - microdomain, slug flow and non-Newtonian nanofluids (NNnF) on hydrodynamic and mass transfer studies for two-phase flow systems. The effect of non-Newtonian fluid (NNF) on the flow pattern and mass transport properties of an immiscible liquid-liquid system in straight and helical microchannels with internal diameters of 0.15 mm and 0.25 mm is being explored experimentally as well with CFD simulations. The range of slug flow has been increased along with enhancement of mass transfer coefficient with the introduction of non-Newtonian nanofluid. Unprecedentedly the addition of 0.5% (w/v) carboxy methyl cellulose (CMC) and Nickel (Ni) nanoparticles has resulted in fifteen times enhancement of mass transfer coefficient.

Plant Latex as a Versatile and Sustainable Emulsifier.

Emulsions are a class of high-surface-energy materials typically stabilized by surfactants, polymers, particles, or a combination of these. There has been considerable effort to develop new emulsifiers by exploiting developments in synthetic chemistry; however, synthetic surface-active species may assist in the stabilization of a specific type of immiscible liquid-liquid systems. That is, one stabilizer does not provide a solution for all interface stabilization problems. Moreover, the synthesis of surface-active systems involves high production costs and complex synthesis routes and generates a substantial amount of chemical waste. In this work, we show that plant latex, an aqueous dispersion of colloidal-scale particles in which small as well as large bioactive species are also present, can be used as a versatile and sustainable source for interface stabilization. The constituents of the latex are found to reduce the oil-water interfacial tension due to the spontaneous adsorption of surface-active species present in the latex. The surface-active nature of latex is further exploited to obtain very stable single emulsions, double emulsions (DEs), and multiple emulsions (MEs). Our results conclusively show that plan latex is a potential versatile source for the stabilization of emulsions created by considering different types of immiscible liquid systems.

Dispersion of immiscible liquid-liquid system in a vessel agitated by a Sawtooth impeller: drop size time evolution

Mixing of immiscible liquid-liquid system is the crucial process for many branches of industry. The main purpose of this process is to increase mass transfer efficiency in processes occurring in chemical and metallurgical industry. The knowledge of drop size and surface area of drops is important for the determination of mass transfer time. The aim of this contribution is to study drop size time evolution in immiscible liquid-liquid system agitated by high-shear Sawtooth impeller in baffled cylindrical vessel. The drop size evaluation was investigated in three different regions of interest. The time evolution of drop size was described by the kinetic model proposed by Hong and Lee (1983) for each region of interest. Simultaneously, the drop size distribution (DSD) was determined and compared for each regions of interest. The time evolution of drop sizes was investigated by non-invasive measurement directly in control volume. The images of illuminated region of interest were captured by a high-speed camera. The captured images were processed by the Image Analysis method.

Effect of ultrasound on parallel flow in a microchannel

Ultrasound and microreactors are a proven combination with many complementary effects that could lead to substantial improvement in an unit operation. This combination is especially effective in heterogeneous systems where the effectivity depends on improved mass transfer. This work focuses on immiscible liquid-liquid system for the purpose of reactive extraction. Since different flow patterns can be generated in a microreactor, a majority of the work with this combination focuses on the slug flow which is the most common and effective of the flow patterns. This work focuses on parallel flow which is less common due to the stricter conditions required to generate it, but with a more consistent interfacial area in comparison to the slug flow. The qualitative and quantitative effects of using ultrasound to parallel flow is explored with a high speed camera and a model test reactive extraction process. The effect of ultrasonic and operating parameters were studied. An improvement of 2.2 to 2.3 times in yield was obtained at a frequency of 41.57 kHz, amplitude of 590 mV and net applied elec. power of 20 W for a residence time ranging from 2 to 20 s, respectively.

A pH EFFECT ON BENZOIC ACID SOLUBILIZATION AND THEIR PARTITIONING (K) IN WATER- BENZENE SOLVENTS

The solubility of substance is depends on temperature and interaction of solute-solvent with its dissociation in ionic form as ionic strength of acid at different pH, where their partitioning (K) are observed between two immiscible liquid-liquid solvents system.

A Perspective on Catalysis in the Immiscible Liquid-Liquid System

This manuscript provides a perspective on research work related to the catalysis in the immiscible liquid-liquid system. Three catalytic concepts, i.e., phase-transfer catalysis (PTC), triphase catalysis (TPC), and phase-boundary catalysis (PBC), are presented as well as their use for the design of a better catalytic system. This perspective emphasizes based on the SWO (Strengths, Weaknesses, and Opportunities) analysis of PTC, TPC, and PBC and advances concept uses for future directions of research in this area.

Modelling of immiscible liquid-liquid systems by Smoothed Particle Hydrodynamics

Immiscible fluid systems are ubiquitous in industry, medicine and nature. Understanding the phase morphologies and intraphase fluid motion is often desirable in many of these situations; for example, this will aid improved design of microfluidic platforms for the production of medicinal formulations. In this paper, we detail a Smoothed Particle Hydrodynamics (SPH) approach that facilitates this understanding. The approach includes surface tension and enforces incompressibility. The approach also allows the consideration of an arbitrary number of immiscible phases of differing viscosities and densities. The nature of the phase morphologies can be arbitrary and change in time, including break-up (which is illustrated) and coalescence. The use of different fluid constitutive models, including non-Newtonian models, is also possible. The validity of the model is demonstrated by applying it to a range of model problems with known solutions, including the Young-Laplace problem, confined droplet deformation under a linear shear field, and a droplet falling under gravity through another quiescent liquid. Results are also presented to illustrate how the SPH model can be used to elucidate the behaviour of immiscible liquid systems.

Flow transition criteria of a liquid jet into a liquid pool

To better understand the fundamental interactions between melt jet and coolant during a core-disruptive accident at a sodium-cooled fast reactor, the jet breakup and droplet formation in immiscible liquid-liquid systems were studied experimentally. Experiments using two different pairs of test fluids were carried out at isothermal conditions. The observed jet breakup behavior was classified into characteristic regimes based on the classical Ohnesorge classification in liquid-gas systems. The variation in breakup length obtained in the present liquid-liquid system was similar to that in a liquid-gas system. The droplet size distribution in each breakup regime was analyzed using image processing and droplet formation via pinch-off, satellite formation, and entrainment was observed. The measured droplet size was compared with those available from melt jet experiments. Based on the observation and analysis results, the breakup regimes were organized on a dimensionless operating diagram, with the derived correlations representing the criteria for regime boundaries of a liquid-liquid system. Finally, the experimental data were extrapolated to the expected conditions of a sodium-cooled fast reactor. From this, it was implied that most of the hydrodynamic conditions during an accident would be close to the atomization regime, in which entrainment is the dominant process for droplet formation.

Drop generation from a vibrating nozzle in an immiscible liquid-liquid system

Drop generation from an axially vibrating nozzle exhibits a transition in drop diameter when varying the vibration amplitude. Below a threshold amplitude, forcing has essentially no effect on drop size and drops form in dripping mode. Above the threshold, drop size is controlled by forcing: drops detach at resonance, i.e., when the first eigenfrequency of the growing drop coincides with the forcing frequency. We experimentally study the impact of the nozzle inner diameter, dispersed phase flow rate, interfacial tension, and dispersed phase viscosity on this transition. Drop diameter is well correlated to the mode 1 eigenfrequency of Strani and Sabetta for a drop in partial contact with a spherical bowl. We propose a transient model to describe drop dynamics until detachment. The drop is modelled as a linearly forced harmonic oscillator, with the eigenfrequency of Strani and Sabetta. Since the dispersed phase does not wet the nozzle tip, an additional damping coefficient is introduced to account for the viscous dissipation in the film of continuous phase between the drop and nozzle surface. The model adequately reproduces the effect of the different parameters on the threshold amplitude.

Recent Development in Counter-current Chromatography

Abstract Counter-current chromatography (CCC) is a quick preparative separation technique with immiscible liquid-liquid solvent systems. This paper reviews recent research progress in the instruments improvement of CCC and screening of solvent systems. Moreover, some applications and prospective about chiral resolution by CCC are discussed. Finally, the content and goal of further research in this field are also presented.

Controllable Phase Separation by Boc-Modified Lipophilic Acid as a Multifunctional Extractant

While phase separation of immiscible liquid-liquid systems has become increasingly significant in diverse areas, the irreversible nature limits their further application in controllable extraction-concentration or capture-release fields. There is a need for the development of simple, efficient and reversible methods for numerous research and industrial extraction and separation applications. We envisioned Boc-modified lipophilic acids as a simple model for such use based on the studies of the multi-phase transitions of Boc-modified supramolecular polymeric systems. Here, we demonstrate that in the presence of Boc-7-aminoheptanoic acid (Boc-7), phase separation occurs in mixtures of miscible organic solvent and water. The separation behavior was confirmed by differential colorimetric development in aqueous and organic phases using methyl orange staining assays. Component substitution experiments verified that the phase separation results from the subtle balance between the aggregation and the solvation forces of Boc-7, and is reversible by adjusting the solution pH. Owing to the intrinsic hydrophobic properties of the organic phase and the hydrogen bonding-forming ability of the carboxyl group of Boc-7, the phase separation system captures and releases Sudan Red, fluorescein, and streptavidin in a controllable manner. Consequently, a reversible and simple phase separation system can be designed as a multifunctional extractant.

A quantitative approach to assess the mixing ability of single-screw extruders for polymer extrusion

Abstract Models to predict the evolution of the morphology of immiscible liquid-liquid systems and of solid agglomerates dispersion in single-screw extruders were adapted to compute global distributive and dispersive mixing indices. Using these indices, the direct assessment of the mixing ability of a given screw or a comparison of distinct screws becomes readily available. In the case of liquid-liquid systems, the degree of distributive mixing is computed from the extent of deformation of the individual drops, whereas the degree of dispersive mixing is determined by the reduction in drop size. For solid-liquid systems, distributive mixing is quantified by a normalized Shannon entropy, whereas dispersive mixing is defined from the extent of size reduction. The effect of material properties, operating conditions, and geometry of the screw and die is investigated. Finally, the indices are used to determine (via optimization) the operating conditions and the screw geometry that maximize the mixing efficiency.

Liquid−Liquid Biphasic Synthesis of Layered Zinc Hydroxides Intercalated with Long-Chain Carboxylate Ions and Their Conversion into ZnO Nanostructures

A method for synthesizing layered zinc hydroxide compounds in high yields is developed using an immiscible liquid-liquid system in one pot. Long-chain carboxylate ions such as heptanoate, decanoate, and dodecanoate were successfully intercalated between zinc hydroxide layers in one process starting from a xylene-water system. Typically, a xylene phase dissolving the respective carboxylic acids was allowed to stand in contact with an aqueous phase dissolving zinc nitrate hexahydrate and urea. During keeping the resultant biphasic system at 80 °C, urea was thermo-hydrolyzed to supply OH(-) in the aqueous phase while the carboxylic acids were continuously transferred from the xylene phase under the distribution law. The aqueous phase was then supersaturated, and a solid phase of layered basic zinc carboxylate was precipitated as films on glass substrates through heterogeneous nucleation and subsequent two-dimensional crystal growth. Crystal structures and morphology of the films were modulated by the kind of the carboxylic acids employed. The layered basic zinc carboxylate films could be converted to nanostructured, mesoporous ZnO films by heating at 450 °C in air. The relationship between the initial solution compositions and the final solid products was systematically examined to discuss reaction mechanisms in the biphasic systems.

Estimation of the morphology development of immiscible liquid–liquid systems during single screw extrusion

AbstractA mathematical model to predict the evolution of the morphology of immiscible liquid–liquid systems in single screw extruders has been developed. The model computes the dimensions of the dispersed phase in the polymeric matrix, taking into account the stretching, break‐up, and coalescence phenomena. The corresponding routine was inserted in a process modeling software, describing the flow in a single screw extruder from hopper do die. The drop dimensions were computed along the melting and melt conveying zones. This enabled the study of the morphological evolution of a two‐phase liquid system in a single screw extruder, taking into consideration the effects of the material properties, operating conditions, and screw geometry. The limited experimental data obtained was generally in line with the theoretical predictions. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

A Phase-Field Model for the Pinchoff of Liquid-Liquid Jets

Abstract Understanding pinchoff in a liquid-liquid jet is one of the fundamental problems in the physics of fluid. Pinchoff has a wide variety of applications such as in ink-jet printers. We have numerically investigated the breakup of a forced liquid jet into drops in immiscible liquid-liquid systems with a phase-field model. In the phase-field model, the classical sharp interface between the two immiscible fluids is represented by a transition region of small but finite width. Across this width the composition of one of the two fluids changes continuously. The phase-field method can deal with topological transitions such as breakup and reconnection smoothly without ad hoc “cut and connect” or smoothing procedures. We compared the numerical results on the pinchoff of liquidliquid jets with surface tension finding good agreement with experimental data. In particular, we investigated axial velocity and vorticity structures around the jet neck before and after pinchoff.

Influence of Jet Velocity on Jet Breakup in Immiscible Liquid-Liquid Systems

The breakup of a laminar liquid jet is the underling phenomena used to generate emulsions in micro-scale devices. Jet breakup is induced by the most unstable disturbance growing on the jet surface, and linear instability analysis can be utilized to predict the resultant droplet size. Previously, instability analysis has been applied to stationary jets at intermediate Re only. This study investigates the influence of the jet velocity on the jet breakup at low Re number. The breakups of moving liquid jets were monitored using a high speed camera. The jet diameter, jet breakup length and resultant droplet sizes were strongly influenced by jet velocity. In addition to a simplified solution, a linear analysis for a moving jet was developed to determine the resultant droplet size. It was found that the full analysis is required to correctly predict the droplet size at low Re number.

Amphiphilic NaY zeolite particles loaded with niobic acid: Materials with applications for catalysis in immiscible liquid-liquid system

The catalytic potential of catalysts for acid-catalyzed reactions has been demonstrated by NaY zeolite loaded with alkylsilane-covered niobic acid in the liquid phase hydration of 1,2-epoxyoctane with water. The catalytic activity of the catalysts was correlated to the amphiphilic character of the solid catalyst particles.

A Microreactor for the Nitration of Benzene and Toluene

Narrow channel microreactors have been evaluated for the reaction of immiscible liquid-liquid systems. In order to stimulate rapid interphase mixing and mass transfer, alternating slugs of organic and aqueous phases were generated at a "T" piece and flowed down an etched channel in a glass substrate. The detailed flow behavior was recorded photographically. Finally, some benzene and toluene nitration experiments were performed in stainless steel and PTFE capillary tubing in order to explore the industrial potential of microreactors for chemical production.

Jet pinch-off and drop formation in immiscible liquid-liquid systems

The behavior of glycerin–water jets flowing into immiscible ambients of Dow Corning 200 fluid was investigated using laser induced fluorescence (LIF). Undistorted images were obtained by matching the index of refraction of the fluids. A sinusoidal perturbation was superposed on the flow to phase lock the drop formation. The forcing frequency dramatically affected the size, spacing, and number of drops that formed within a forcing cycle and the angle between drops and the jet interface just before pinch-off. Two fluid combinations were studied with similar density ratios, but viscosity ratios differing by a factor of 20. The viscosity ratio affected the jet stability as well as pinch-off angles and drop size.

Rise Height for Negatively Buoyant Fountains and Depth of Penetration for Negatively Buoyant Jets Impinging an Interface

A vertical jet or fountain, whose velocity is opposite to the direction of its buoyant force, reverses direction after reaching a maximum penetration depth. This penetration depth is measured from the jet exit or, if present, the location of the undisturbed interface. This paper shows that the penetration depth is only a function of a Richardson number divided by a jet spreading factor. If no interface is present, the spreading factor is one; otherwise the spreading factor is only a function of distance between the jet exit and the interface. As long as the jet is fully turbulent, the penetration depth is independent of Reynolds and Weber numbers. These trends are applicable to a broad range of fluid systems including air jets impacting liquids as well as miscible and immiscible liquid-liquid systems with only slight density differences. [S0098-2202(00)00304-7]