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.     

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，...     

Carrier-facilitated liquid membrane extraction of penicillin G from aqueous streams

Kinetics and mechanism for the carrier-facilitated transport of penicillin G from aqueous solutions through a supported liquid membrane containing Amberlite LA-2 were investigated. The strip phase was either phosphate buffer or sodium carbonate solution. Experiments were performed as a function of the pH, the concentrations of penicillin G in the feed phase and of amine in the membrane phase. A transport model was proposed considering aqueous film diffusion, interfacial chemical reaction, and membrane diffusion. The calculated rates were found to agree with the measured ones (average standard error, 12%). Under the conditions investigated (feed pH 5.02–7.83, penicillin G concentration 10–500 mol/m³, amine concentration 50–1000 mol/m³), the present transport process was shown to be governed by combined interfacial chemical reaction and membrane diffusion.     

Effect of volume ratio of internal aqueous phase to organic membrane phase (w/o ratio) of water-in-oil emulsion on penicillin G extraction by emulsion liquid membrane

The batch extraction of penicillin G from a model media was studied so as to obtain the optimal w/o ratio in an emulsion liquid membrane (ELM) system with the help of our previous works. First of all, the effects of organic solvents or surfactants in membrane phase on apparent degree of its extraction at various w/o ratios were investigated. The organic solvents and surfactants were kerosene/n-butyl acetate and Span 80/PARABAR 9551, respectively. The optimal composition between two surfactants for the highest apparent degree of extraction was obtained at each w/o ratio.With the optimal surfactant composition at each w/o ratio, citrate buffer solutions of three different concentrations having about pH 4.8 were selected as the external aqueous phase. The mass of Na₂CO₃ in the internal phase was kept constant for every w/o ratio in order to investigate the effects of w/o ratio on the degree of extraction under the same trapping mass of Na₂CO₃ for penicillin G. The highest possible concentration of Na₂CO₃ in the internal phase was chosen using balance equations and equilibrium expressions. In consequence, the highest actual degree of extraction of 98.2% and the lowest percentage of swelling of 36.0 were obtained in the specific ELM system with 0.41 M citrate buffer solution, 0.175 M Na₂CO₃ and w/o ratio of 1/1.     

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.     

Studies on emulsion liquid membrane extraction of cephalexin

An experimental study on batch extraction of cephalexin using an emulsion liquid membrane system has been reported. The effects of surfactant, carrier and solute concentrations, phase volume ratio, stirring speed, and counterion concentration on the extraction rate were examined. Surfactant, carrier and diluent used were Span-80, Aliquat-336 and n-heptane–kerosene (1:1), respectively. Under the optimised experimental conditions, emulsion swelling was found to be marginal. By maintaining an appropriate pH gradient in the feed and receiving aqueous phase, facilitated transport could be realised. Selective separation of cephalexin from a mixture of 7-aminodeacetoxy cephalosporanic acid (7-ADCA) could be demonstrated in the emulsion liquid membrane system. A mathematical model based on mass transfer across aqueous boundary layer, interfacial chemical reaction and diffusion in the emulsion globule provides a reasonable fit of the experimental solute concentration versus time profiles in the emulsion liquid membrane system.     

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.     

水溶性聚合物和两亲聚合物19．磺化液体聚丁二烯──种新型液膜用表面活性剂

一种新的聚工二烯型表面活性剂ＬＹＦ经液体聚了二烯磺化方法制备而得，并应用于液膜分离研究之中。发现无论内水相是酸性还是碱性，由该表面活性剂制得的Ｗ／Ｏ型乳状液在稳定性、溶胀率和破乳诸方面均具有令人满意的综合性能。为深入了解液膜的稳定性，我们测定了处于两种水相间的双分子膜的强度。发现由ＬＹＦ所形成的双分子膜具有最大的膜强值，优于聚异丁烯型的表面活性剂ＥＣＡ４３６０和ＥＭ３０１．     

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.     

Uranium extraction enhancement form phosphoric acid by emulsion liquid membrane

This work is mainly concerned with the uranium extraction from phosphoric acid commercially produced by Abu Zaabal Fertilizers and Chemical Co., Egypt. This target would realize a dual purpose where the phosphate ore is considered as an alternative source of uranium besides eliminating its environmental contamination. The applied procedures are that of the new technology of emulsion liquid membrane. Authors have indeed pointed out that the variables explored still leave open to question the roles of stripping at the internal interface as well as the bulk transfer of uranium in the internal phase. For this purpose, two reducing agents are studied as additives to two organic solvent systems; namely the organophosphorous synergistic mixture of D2EHPA/TOPO as well as the tridodecyl amine. The relevant factors have first been optimized upon synthetic uraniferous phosphoric acid solution followed by the application upon the commercial acid after purification. These factors include the concentration of solvent system and the used emulsifier, acid concentration of the external and internal phases besides the nature and concentration of the reductant added to the internal phase. In addition, the permeation time as well as the oxidation state of the external phase was studied. All these factors have indeed been studied under different mixing speeds ranging from 300 up to 1,000 rpm. Ascorbic acid concentration, 1 % as an additive to the internal phosphoric acid phase (40 % P₂O₅) resulted in 95 % uranium extraction efficiency at the lower speed of 600 rpm.     

Simplified model for extraction of rare-earth ions using emulsion liquid membrane

By considering the resistances of rare-earth ions in both the external and membrane phases, the interfacial reaction and the membrane breakage, a mathematical model for the extraction of rare-earth ions by batch emulsion liquid membrane process is established. Further, two simplified mass transfer equations are also derived from the proposed model in each of the specified cases. The validity of both the model and the resulting equations are tested by batch extraction of Sm³⁺ with emulsion liquid membrane containing di-2-ethylhexyl phosphoric acid as a carrier in kerosene. The experimental results show that both the proposed model and the resulting equations can simulate mass transfer process satisfactorily.     

Development of radioligands for the dopamine transporter

The extraction of Penicillin G (Pen G) and its conversion to 6-aminopenicillin acid (6-APA) and phenylacetic acid (PAA) was performed by means of Penicillin G Amidase immobilised in the emulsion liquid membranes. Using various surfactants as emulsifiers and an appropriate carrier it is possible to obtain different extraction rates of Pen G as well as back transfer rates of the hydrolysis products. The surfactants with polyoxyethylene chain facilitate the back transfer through the membrane phase, whereas the more hydrophobic surfactants, e.g., Paranox 100, tend to accumulate Pen G hydrolysis products in the internal aqueous phase.     

Extraction of cadmium from aqueous solutions by emulsion liquid membrane (ELM) using three different carriers dissolved in a 70:30 ratio of sunflower oil to kerosene

This study explores the use of novel green emulation liquid membranes (GELMs) for the simultaneous extraction and stripping of Cd (II) from aqueous solutions. A solute is transported through the membrane due to the presence of the carrier and then concentrated in the internal phase. Soybean, sunflower, corn, and canola oils were used to form green substitutes to petroleum-based organic diluents for use as GELMs. Bis-(2-ethylhexyl) phosphate (D2EHPA), tri-butyl- phosphate (TBP), and trioctylamine (TOA) were the extractants, span 80 was the emulsifier, and HCl or H₂SO₄ was used as the stripping agent. The best conditions for maximum extraction efficiency (98.68%), stripping efficiency (97.14%), and lowest membrane breakage (0.9%) were achieved using a mixture of sunflower oil and kerosene in the ratio of 70:30. The other optimum values of the variables were: 2% (v/v) Span 80, 10 min emulsification time, 12700 rpm emulsification speed, 400 rpm of agitation speed, 5% (v/v) D2EHPA, an external phase pH was 3.5, an internal phase of 0.25 M HCl, and 5:1 of the treat ratio (external phase to emulsion) at 10 min contact time. The synthesized membrane was reused eight times, with approximately the same efficiency and no significant breakage during the first seven cycles.     

Biomimetic Synthesis of CdSe Quantum Dots through Emulsion Liquid Membrane System of Gas-Liquid Transport

The cadmium selenide quantum dots (QD) have been synthesized by template-control in an emulsion fiquid membrane system. The system consisted of kerosene as solvent, L152 (dialkylene succinimide) as surfactant,N7301 (trialiphatic amine, R3N, R=C8-C10) as carrier, 0.1mol/L CdCl2 solution as internal-aqueous phase and H2Se gas as external phase. Additive organic template agent in internal-aqueous phase was necessary to form CdSe QD. The influence of the nature of template and its concentration on sizes of the formed CdSe QD has also been studied. Transmission electron microscopy showed that the sizes of the products could be controlled down to 3-4nm. X-ray diffraction analysis revealed that the crystals had cubic structure. The formation process and the optical properties of CdSe QD have also been presented.     

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.     

Einfluss Organischer Lösungsmittel auf die Extraktion von Thorium(IV) und Uran(VI) mit Substituierten Sekundären,Tertiären und Quartären Ammoniumnitraten aus Salpetersauren Lösungen

The influence of methanol on the distribution of thorium(IV) and uranium(VI) between aqueous solutions of nitric acid and solutions of Amberlite LA-2, trilaurylamine and Aliquat-336-nitrate has been investigated. The amount of acid in the organic phase increases with increasing concentration of nitric acid and methanol in the aqueous phase. The concentration of acid in the organic phase can be calculated by a given formula for Amberlite LA-2. The distribution of methanol is discussed. The distribution of thorium(IV) and uranium(VI) changes, when methanol is added. This is explained by the shift of the equilibrium of the metal complex and by the enhanced extraction of acid.     

铜在乳状液膜体系中的迁移行为

近年来膜分离技术在环境治理方面得到广泛应用。本文研究了铜在span80-TBP（磷酸三丁酯）-煤油-NH3液膜分离体系中的迁移行为。用TBP作为载体,在溶液中迁移时,在外相与膜相界面上形成中性络合物后穿过膜相,在膜相与内相界面上络合物再与NH3反应,生成铜氨络离子,释放出来的TBP又返回膜相。     

A study on a two-component liquid membrane system

A novel two-component liquid membrane system in which one of the components, polyethylene glycol, acts as both carrier and surfactant, is described. The composition and the stability of the two-component liquid membrane system are discussed in terms of surfactant concentration, base concentration in the internal phase, acidity of the external phase, the concentration of the counter-anion SCN^? in the cation extraction, etc. The extraction efficiency and the permeation mechanism of the system are compared with that of conventional three-component liquid membranes. Obviously, the nature of the system is quite different from three-component liquid membranes and conventional solvent extraction, although the system of solvent extraction also contains two components.     

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.     

The extraction of Zn(II), Cd(II) and Pb(II) from hydrochloric acid media by amberlite LA-2 hydrochloride dissolved in 1,2-dichloroethane

The extraction of HC1 by the secondary amine (B), known as Amberlite LA-2, dissolved in 1,2-dichloroethane and the aggregation of BHC1 have been studied by using a two-phase potentiometric titration technique. The experimental data, treated by a general minimizing program, indicate dimerization: 2 BHClright harpoon over left harpoon(BHCl)(2). The equilibrium constant of this reaction was calculated. The extraction of ZnCl(2), CdCl(2) and PbCl(2) from 0.2,0.5, 1.0 and 2.0M HCl, and 1MNaCl by Amberlite LA-2 hydrochloride (BHCl), dissolved in 1,2-dichloroethane, has been studied. The complexes (BHCl)(2)ZnCl(2), (BHCl)(2)CdCl(2) and (BHCl)(2)PbCl(2) were found to exist, irrespective of the composition of the aqueous phase. The formation constant of the first was calculated.