Studies on the applicability of artificial neural network (ANN) in emulsion liquid membranes

An artificial neural network (ANN) model of emulsion liquid membrane (ELM) process is proposed in the present study which is able to predict solute concentration in feed during extraction operation and ultimate % extraction at different initial solute concentration in feed phase, internal reagent concentration, treat ratio, volume fraction of internal aqueous phase in emulsion and time. Because of the complexity in generalization of the phenomenon of ELM process by any mathematical model, the neural network proves to be a very promising method for the purpose of process simulation. The network uses the back-propagation algorithm (BPA) for evaluating the connection strengths representing the correlations between inputs (initial solute concentration in feed phase, internal reagent concentration, treat ratio, volume fraction of internal aqueous phase in emulsion and time) and outputs (solute concentration in feed during extraction operation and % extraction). The network employed in the present study uses five input nodes corresponding to the operating variables and two output nodes corresponding to the measurement of the performance of the network (solute concentration in feed during extraction and % extraction). Batch experiments are performed for separation of nickel(II) from aqueous sulphate solution of initial concentration in the 200–100 mg/l ranges. The network employed in the present study uses two hidden layers of optimum number of nodes being thirty and twenty. A leaning rate of 0.3 and momentum factor of 0.4 is used. The model predicted results in good agreement with the experimental data and the average deviations for all the cases are found to be well within ±10%.     

Mathematical modeling of silver extraction by an emulsion liquid membrane process

A general physical model of a typical batch extraction system employing an emulsion liquid membrane process for the extraction of silver has been developed. The model takes into account the extraction reaction between the silver ion and the carrier molecules at the external interface, the diffusion of the complex in the membrane phase, the stripping reaction at the internal interface and the reaction of silver ion with the reagent, HCL, in the internal phase to yield silver chloride incapable of permeating through the membrane phase. In addition, the leakage of the internal aqueous phase to the external aqueous phase due to membrane breakage has been incorporated in this model. The batch extraction of silver using D2EHPA as a carrier has been carried out under various experimental conditions. The experimental data can be well explained by the present model.     

Studies on transport mechanism of Cr(VI) extraction from an acidic solution using liquid surfactant membranes

A mathematical model for analysing the extraction of Cr(VI) from aqueous acidic solution by emulsion liquid membrane using Aliquat 336 as extractant and NaOH as stripping agent has been presented. The existing models developed so far do not account for the existence of different forms of Cr(VI) ions in the aqueous phase depending on pH conditions. Accordingly, in the present model, reaction equilibrium has been considered instead of distribution coefficient to represent realistically the transport mechanism for this type of system through liquid surfactant membrane. Unlike other models, liquid–liquid equilibrium of sodium hydroxide-chloride of Aliquat 336 has also been considered. The carrier thus exists in the membrane phase in hydroxide and chloride forms and extraction of hexavalent chromium from the external phase proceeds by the two carriers. The validity of the model has been checked from comparison of the simulated curves and experimental data using chemical reaction equilibrium constant and D_eff/R² as fitting parameters.     

Extraction of Arsenic(V) from Water Using Emulsion Liquid Membrane

In this article, the extraction of arsenic(V) from water by means of emulsion liquid membrane is investigated. The influence of operating factors such as stirring speed, concentration of sulfuric acid in the external aqueous phase, concentration of sodium sulfate in internal stripping phase, and concentration of carrier in the membrane phase on the extraction efficiency are investigated and their optimum values, which provide the maximum recovery of arsenic, are determined. Taguchi experimental design is used in order to reduce the number of experiments. The optimum amounts for the extraction of arsenic from water, based on the results, are: stirring speed, 500 rpm; concentration of sulfuric acid in the feed, 1.5 g mol/lit; concentration of reagent in internal phase, 1.5 g mol/lit; and concentration of carrier in 3 ml kerosene which is added to the membrane phase, 0.1 g mol/lit.     

Mathematical modeling of penicillin G extraction in an emulsion liquid membrane system containing only a surfactant in the membrane phase

An extraction experiment of penicillin G was performed in an emulsion liquid membrane system in which only ECA 4360J exists in the organic membrane phase without a predominant carrier, Amberlite LA-2, used in our previous works and it functions as a carrier as well as a surfactant. A permeation model for the present system has been developed as a primary study to examine the transport mechanism of penicillin G in the previous batch and continuous systems with two carriers of Amberlite LA-2 and ECA 4360J. The model takes into account the mass transfer in the external aqueous film, the extraction reaction between penicillin G and ECA 4360J at the external interface, the diffusion of penicillin G in the emulsion phase, the stripping reaction at the internal interface and the pH change of internal aqueous solution containing Na₂CO₃ with penicillin G transported into the internal phase. The experimental data were well fitted with the present model. Also, an expression for the reaction of penicillin G with ECA 4360J was obtained through a series of equilibrium measurements in liquid–liquid extraction system.     

Facilitated transport through liquid surfactant membrane: Analysis of breakage model

A mathematical model for analyzing the experimental data of extraction of weak acid from aqueous solution by liquid surfactant membrane (LSM) using a strong base as internal reagent present in excess in a batch system has been presented. The leakage of internal phase due to membrane breakage is also discussed in the mathematical treatment. The model while considering a reaction front to exist within the emulsion globule assumes reaction equilibrium between the solute and internal reagent in the external continuous phase. The proposed model predicts successfully the experimental results of extraction of a weak acid by a strong base in a batch separation system as presented in the literature. The model is also capable of predicting excellently the experimental pH versus time data in case of the above system.     

Emulsion liquid membranes: Role of internal droplet size distribution on toluene/n-heptane separation

Using oil/water/oil-type emulsion liquid membranes, batch wise extraction experiments are carried out to separate toluene from a mixture of toluene and n-heptane. In the separation process using emulsion liquid membranes, the internal phase polydispersity affects mass transport of a solute because under steady operating conditions, internal droplet size and size distribution are proportional to the interfacial area. The present study aims to assess the polydispersity character of the internal droplets of emulsion globules. In this paper, the important variables affecting dispersed drop sizes as well as internal droplets mean diameter and size distribution of the emulsion globule, including impeller speed during emulsification, surfactant concentration, volume ratio of surfactant solution, carrier concentration and composition of feed phase are systematically investigated.     

Liquid membrane extraction of Cephalosporin-C from fermentation broth

The extraction of Cephalosporin-C (CPC) from dilute fermentation broth of Cephalosporium acremonium was studied in a bulk liquid membrane as well as in an emulsion liquid membrane system. Aliquat-336 was used as the extracting agent to provide facilitated transport of CPC via liquid–liquid ion exchange mechanism. By maintaining an appropriate pH gradient in the feed and receiving phases, facilitated uphill transport could be achieved in the bulk liquid membrane system. The culture broth contains CPC and deacetyl CPC (DCPC) which are structurally almost similar, but CPC is more hydrophobic in nature. Selective separation of CPC could be achieved in a suitably formulated liquid membrane system. A simple mass transfer model predicts the permeation rate in the bulk liquid membrane. The permeation process in an emulsion liquid membrane appears to be controlled by the aqueous boundary layer resistance and diffusion in the emulsion globule. This is perhaps the first demonstration of the liquid membrane as an effective technique for selective extraction of CPC from fermentation broth of Cephalosporium acremonium.     

Thioether-mediated copper transport through liquid membranes with the aid of redox reaction

A thioether-mediated copper transport with the aid of redox reaction was studied in a polymer-supported liquid membrane and in a liquid surfactant membrane. A photochemical generation of the redox potential led to a photo-assisted copper separation and concentration system. Tetradentate thioethers 1 and 2 (L) selectively extracted copper ion into organic solution in the presence of a reducing agent, and served as a copper-selective carrier in a liquid membrane system. In the polymer-supported organic liquid membrane system, the thioether was dissolved in the membrane phase which separated the two aqueous solutions of different redox potentials. The copper ion was extracted into the membrane phase by formation of the [Cu^IL]⁺ ? X^? type complex on the reducing solution interface and permeated through the membrane toward the oxidizing solution interface, where the complex was decomposed to release the copper(II) species into the oxidizing aqueous solution. The nature of the system was studied in detail under various operational conditions (redox agents, pairing anion X^?, coexisting metals, etc.) and compared with that of the previously reported Bathocuproine-mediated system. The transport system was extended to the water-in-oil-in-water emulsion system (liquid surfactant membrane), and the selective concentration of copper ion from dilute external aqueous solutions into inner stripping solutions was achieved. Photo-induced redox reactions, triethanolamine—acriflavine—methyl viologen—hv and glucose—titanium oxide—hv, were successfully coupled to the systems, leading to a photo-assisted copper transport in the polymer-supported liquid membrane as well as in the liquid surfactant membrane. Tentative explanations were given on the nature of the membrane transport reactions.     

环烷酸类载体液膜体系对金属离子传输机理的研究

本文先在大块液膜体系中以环已烷甲酸为载体,通过正交设计,系统地研究了各种因素对希土离子输送作用的影响规律。比较了相同条件下RE~(3+)(希土)同Na~+,NH_4~+、Ca~(2+)和Fe~(3+)等离子的输送作用。发现在适当条件下,无皂化的羧酸载体对RE~(3+)离子具有良好的输送效果,同时证实,羧酸输送RE~(3+)离子是通过三个H~+离子与一个RE~(3+)离子的交换,而当载体皂化时,皂化的载体直接与接收相H~+离子发生交换,从而降低了羧酸对RE~(3+)离子的输送和分离效果。 在大块液膜研究的基础上,建立了一个以无皂化的环烷酸为载体的乳状液膜体系,从模拟离子矿的硫酸铵浸出液中萃取希土,通过正交试验确定了最优的液膜萃取条件,希土萃取率达96％以上,富集度30～40倍。     

液膜分离富集、测定痕量钼

用乳状液膜体系对钼进行富集。该体系包括载体 ( 5,8-二乙基 - 7-羟基十二烷 - 6-单肟 ,简称LIX63)、表面活性剂 (N1 1 3C)、溶剂(煤油 )以及内相 ( 0 .1 5mol/LNaOH溶液 )。研究了乳状液膜的稳定性、温度、钼的浓度、外相的HNO3溶液浓度及乳水比等因素对分离富集钼的影响。实验表明 ,在适宜的条件下 ,钼的迁移率可达 99.5%～1 0 0 .2 %。该法已应用于富集、测定纯钨和钢铁中的痕量钼 ,结果相当满意     

Concentration of amino acids by a liquid emulsion membrane with a cationic extractant

The concentration of -phenylalanine in a liquid emulsion membrane system was studied using a cation complexing agent, di-2-ethylhexyl phosphoric acid (D2EHPA), as a carrier. The membrane formulation, the pH in the internal phase of the acid concentration in the external phase were optimized with respect to concentration performance and membrane stability. It was found that a liquid emulsion membrane obtained by demulsification of the emulsion by an electrostatic coalescer could be reused. Based on the laboratory tests, a continuous multistage process for the concentration of amino acids was proposed (with the development of a commercial process in mind) and its technical feasibility was discussed.     

Emulsion liquid membrane extraction of zinc by a hollow-fiber contactor

Emulsion liquid membranes (ELMs) can contribute to process intensification of zinc extraction, by significantly reducing the solvent and carrier requirements in comparison with conventional solvent extraction. Di(2-ethylhexyl)phosphoric acid (D2EHPA) was used as a highly selective carrier for the transport of zinc ions through the emulsified liquid membrane. The hollow-fiber extractor appears to offer significant advantages over conventional liquid–liquid contactors for this separation because emulsion leakage and swell are practically eliminated even when treating high concentration feeds. Various hydrodynamic and chemical parameters, such as variation in feed pH; zinc concentration in feed; variation in concentrations of D2EHPA; variation in feed/emulsion volume ratios and variation in feed and emulsion flow rates, were investigated. The content of sulfuric acid as an internal did not show in the studied range any significant influence on zinc extraction through the ELM, although a minimum hydrogen ion concentration is suggested in the internal aqueous solution to ensure acidity gradient between both aqueous phases to promote the permeation of zinc ions toward the internal phase. The experimental mass-transfer coefficients have shown a stronger dependence on hydrodynamic conditions in both the external feed phase and emulsion among the parameters studied. For emulsion flow rate, mass-transfer coefficient increased from 16.3 × 10⁻⁶ m/s at 200 ml/min to 31.2 × 10⁻⁶ m/s at 640 ml/min. Significant increasing in mass-transfer coefficient observed with increasing aqueous flow rate from 9.7 × 10⁻⁶ m/s at 170 ml/min to 37.2 × 10⁻⁶ m/s at 740 ml/min. The overall mass-transfer coefficient increases from 12 × 10⁻⁶ m/s at 2% D2EHPA to 28 × 10⁻⁶ m/s at 8% D2EHPA. This means that this process is chemically controlled and the interfacial resistance has a more significant role in the extraction of zinc by emulsion liquid membrane through hollow-fiber contactor. From the results obtained, it seems that the diffusion processes in aqueous feed phase and the membrane phase have the same importance as the chemical process.     

Extraction of Priority Pollutant 4-Nitrophenol from Water by Emulsion Liquid Membrane: Emulsion Stability,Effect of Operational Conditions and Membrane Reuse

This work aims to the extraction of the priority pollutant 4-nitrophenol (4-NP) from water by emulsion liquid membrane (ELM). Liquid membrane consists of a diluent (hexane) and a surfactant (Span 80). Sodium carbonate solution was used as internal aqueous phase. Effects of important experimental conditions governing the stability of the W/O emulsion were investigated. Influence of operating parameters that affects the permeation of 4-NP such as surfactant concentration, emulsification time, sulfuric acid concentration in external phase, acid type in external phase, internal phase concentration, type of internal phase, stirring speed, volume ratio of internal phase to membrane phase, treatment ratio, 4-NP initial concentration, and diluent type was examined. This study also evaluated the effect of Na₂CO₃ concentration in the internal aqueous phase on the stripping of 4-NP. Additionally, the reuse of the recovered membrane was studied. Under most favorable conditions, practically all the 4-NP and aniline (AN) molecules present in the feed phase were extracted. The recovery of the membrane phase was total and the extraction of 4-NP was not decreased. The ELM treatment process represents a very interesting advanced separation process for the removal of 4-NP and AN from aqueous solutions.     

Inclusion extraction of alkali metals by emulsion liquid membranes bearing nano-baskets

Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclusion-facilitated emulsion liquid membrane process. The novelty and significance of this study is application of nano-baskets of calixarene in the selective and efficient separation of alkali metals, as both carrier and surfactant. For this aim, four derivatives of p-tert-calix[4]arene bearing different sulfonamide moieties were synthesized and their inclusion-extraction parameters were optimized. Maximum extraction was achieved using calixarene scaffold 03 (3.45 × 10^?2 M) as carrier/demulsifier, commercial kerosene as diluent in membrane, sulphonic acid (0.2 M) and ammonium carbonate (0.4 M) as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed (300 rpm), and initial solute concentration (100 mg/L). The selectivity of membrane over more than ten interfering cations was examined and the results reveled that under the optimized operating conditions, the extraction percent of alkali metals was 98–99 %.     

Removal of Mercury by Emulsion Liquid Membranes: Studies on Emulsion Stability and Scale Up

Emulsion liquid membranes (ELM) have received significant attention in the separation of various metal ions from industrial wastewater. Still efforts are needed to get the desired level of stability to overcome the hindrance in the application of ELM at industrial scale. In this paper, the effects of various parameters such as emulsification speed, concentration of cosurfactant, surfactant, carrier and impeller speed during extraction on the stability of an emulsion liquid membrane are studied. Dispersion destabilization of w/o emulsion is checked by Turbiscan. Drop size distribution and photomicrographs of the emulsions are also analyzed to evaluate stability of the emulsion. Instability of emulsion liquid membrane during extraction process is measured in terms of membrane breakage. A stable emulsion is used for the extraction of mercury from aqueous solution in small scale as well as in large scale.     

乳状液膜法提取L—谷氨酸的研究

乳状液膜法提取Ｌ－谷氨酸的研究徐占林（四平师范学院化学系四平１３６０００）严忠张河哲（东北师范大学化学系长春１３００２４）关键词Ｌ－谷氨酸乳状液膜载体萃取中图分类号Ｏ６２３．７３６氨基酸作为重要的生化产品，广泛应用于食品、饲料、医药、化工等许多领域，...     

Extraction of Cr (VI) by pickering emulsion liquid membrane using amphiphilic silica nanowires (ASNWs) as a surfactant

Pickering emulsion is the replacement of surfactants with solid, often nano-sized particles. The particle-stabilized emulsions have good thermodynamic and kinetic stability. Pickering emulsion liquid membrane (PELM) was prepared using mahua oil as a diluent, aliquat 336 (Trioctyl methylammonium chloride) as a carrier and amphiphilic silica nanowires (ASNWs) (10–40?ml ethanol addition) as a surfactant. Sodium hydroxide (NaOH) was used as stripping phase in the concentration range from 0.1 to 0.5?M for the extraction of hexavalent chromium [Cr (VI)] from aqueous solution. The variety of edible and non-edible oils was investigated for the stability of water in oil emulsion. Factors that influence silica-stabilized Pickering emulsions are pH, agitation speed, stripping phase concentration, the volume ratio of membrane to stripping phase (M/S), initial feed concentration, treat ratio(feed to emulsion volume ratio) and surfactant concentration for better PELM stability. And also, the extraction efficiency of Cr (VI) was investigated using aliquat as a carrier. The physicochemical properties of ASNWs were studied using Scanning Electron Microscopy (SEM), Fourier Transforms Infrared Spectroscopy (FTIR) and Dynamic Light Scattering (DLS) techniques. At an optimum condition, 99.69% of Cr (VI) removal from aqueous solution was obtained.     

Synchronized extraction and purification of L-lactic acid from fermentation broth by emulsion liquid membrane technique

This study aims to investigate the recovery of L-lactic acid from fermentation broth by an emulsion liquid membrane (ELM), made up of sunflower oil as the diluent, Sorbitan monooleate (Span 80) as the surfactant, Aliquat 336 as the carrier, and sodium hydroxide (NaOH) solution as the internal aqueous phase. Particularly, the ELM process was properly set up, through the identification of the optimal ELM operating parameters on the final extraction efficiency of L-lactic acid, including Span 80 concentration, NaOH concentration, Aliquat 336 concentration, stirring speed, phase ratio, and treatment ratio. The obtained results showed that the extraction efficiency of L-lactic acid reached up to 99% under the following optimal conditions: 10 minutes after contact time, 4% w/w Span 80, 3% w/w Aliquat 336, 0.1?N solution of NaOH, stirring speed of 300?rpm, phase ratio 1, and treatment ratio 0.25. A stable system without considerable emulsion swelling and breakage was monitored using a dynamic light scattering (DLS) apparatus for the selected optimal ELM operating parameters.     

Uranyi ion transport through tri-n-octylamine-xylene based supported liquid membranes

Tri-n-octylamine (TOA) dissolved in xylene has been used as carrier, constituting liquid membrane supported in Celgard 2400 polypropylene microporous film for the transport of uranyl ions against their concentration gradient from aqueous acid solutions to an alkaline aqueous phase. Effect of sttrring rate, nitric acid concentration and TOA concentration in the organic membrane phase, on the flux of uranyl ions through the membrane has been studied. Viscosity and density data have been obtained to estimate diffusion coefficients and hence the permeability coefficients to compare the same with experimental values, using distribution coefficient data, measured from solvent extraction experiments and available in the literature. Analysis of the flux data has been performed to study the stoichiometry of the chemical reaction involved in complex formation reaction. The results have been compared with simple liquid-liquid extraction data.