Mechanistic study of cobalt,nickel and copper transfer across a supported liquid membrane

The mechanism of cobalt, copper and nickel transport through supported liquid membranes containing di(2-ethylhexyl)phosphoric acid as a mobile carrier has been studied. An equation describing the permeation rate has been derived, taking into account stagnant layer aqueous diffusion, interfacial resistance due to solvatation reaction and liquid membrane diffusion as simultaneous controlling factors. The validity of this model is evaluated with experimental data of mass transfer coefficient measured employing a permeation cell. For these ions it was found that at low stirring conditions the stagnant layer resistance mainly controlled the processes, but it is controlled by diffusion of the ion complex through the supported liquid membrane when the stagnant layer resistance is negligible.     

Theoretical Analysis of Copper-Ion Extraction through Hollow Fiber Supported Liquid Membranes

Abstract

An understanding of the extraction of metal ions through hollow fiber supported liquid membranes is important for the design of such systems. In this paper, copper-ion extraction through hollow fiber supported liquid membranes containing D2EHPA as a carrier agent is analyzed. Both a rigorous model and a simple model with varied permeation coefficients for the system are proposed. The once-through mode is first modeled and the parametric effects on the extraction rate are discussed. The recycling mode is then modeled. A comparison between the rigorous model and the simple model with varied/constant permeation coefficients is made. From the models it is found that the permeation coefficient is a function of copper ion concentration.     

THE COMPETITIVE PERMEATION OF COBALT AND NICKEL WITH SUPPORTED LIQUID MEMBRANES

In this paper, the competitive permeation of cobalt and nickel from nitrate solutions through supported liquid membranes was studied, in which contained 2-ethylhexyIphosphonic acid mono-2-cthylhexyl ester (HEHEHP) dissolved in kerosene as a mobile carrier. The permeation rate equations were derived taking into account the aqueous film diffusion of metal ions towards and out of the membrane and the membrane diffusion of HEHEHP and its metal complexes. The mass transfer coefficients of metal ions and metal-HEHEHP complexes were also determined using the permeation cell. It was found that the calculated permeation rates were in good agreement with the measured ones.     

乳化液膜萃取乳酸稀溶液过程中的渗透溶胀及模拟

根据膜相中载体萃取的机理,指出载体在萃取溶质后形成的络合物具有一定的亲水性．采用气相色谱法,分别对含有表面活性剂和载体的膜相在与乳酸溶液接触后的溶水率进行了测定,结果发现其溶水率远高于与无溶质的外相水接触后的膜相溶水率．所以渗透溶胀进人内相的水除表面活性剂分子结合的迁移外还有载体-溶质络合物结合水．从而提出了实际萃取过程中乳化液膜渗透溶胀的反应-溶解-扩散机理,并提出了相应的数学模型,经与实验数据比较,结果吻合较好．     

PC-88A为载体的大块液膜体系Cu(II)传输动力学

采用以2-乙基己基膦酸-2-乙基己基单酯(PC-88A)为载体、CHCl3为膜溶剂的大块液膜分离体系,研究了搅拌速度、载体浓度、体系温度对铜离子迁移的影响. 获得了不同反应温度下的表观反应速率常数,萃取与反萃取表观反应活化能分别为41.97和8.59 kJ/mol. 铜离子的迁移过程可用2个串联的准一级不可逆过程描述,萃取过程化学反应为控速步骤,反萃取过程扩散为控速步骤.     

A Reaction Flux Model for Extraction of Cu(II) with LIX84I in HFSLM

Hollow fiber supported liquid membrane (HFSLM) is a favorable method to extract both valuable compounds and heavy metal pollutants such as chromium, copper, and nickel at a very low concentration. In this work, the extraction of Cu(II) by LIX84I dissolved in kerosene was theoretically and experimentally investigated. A model to estimate the percentage of extraction of copper ions from synthetic water considering the effect of reaction flux in membrane phase of the HFSLM system was studied. H₂SO₄ solution was used as the stripping solution. The facilitated transport mechanism of the chemical reaction at the feed-membrane interface was taken into account in the model equations. The percentage of copper ion extraction was plotted against its initial concentration in feed and also feed flow rate. Subsequently, the separation time and separation cycle were determined in accordance with the simulated values of copper ion concentration and the feed flow rate from the model. The modeled results were in good agreement with the experimental data at the average percentage of deviation about 2%.     

Performance of hollow fiber supported liquid membrane on the extraction of mercury(II) ions

The extraction and recovery or stripping of mercury ions from chloride media using microporous hydrophobic hollow fiber supported liquid membranes (HFSLM) has been studied. Tri-n-octylamine (TOA) dissolved in kerosene was used as an extractant. Sodium hydroxide was used as a stripping solution. The transport system was studied as a function of several variables: the concentration of hydrochloric acid in the feed solution, the concentration of TOA in the liquid membrane, the concentration of sodium hydroxide in the stripping solution, the concentration of mercury ions in the feed solution and the flow rates of both feed and stripping solutions. The results indicated that the maximum percentages of the extraction and recovery of mercury ions of 100% and 97% were achieved at the concentration of hydrochloric acid in the feed solution of 0.1 mol/l, the concentration of TOA at 3% v/v, the concentration of sodium hydroxide at 0.5 mol/l and the flow rates of the feed and stripping solutions of 100 ml/min. However, the concentration of mercury ions from 1–100 ppm in the feed solution had no effect on the percentages of extraction and recovery of mercury ions. Thus, these results have identified that the hollow fiber supported liquid membrane process has high efficiency on both the extraction and recovery of mercury (II) ions. Moreover, the mass transfer coefficients of the aqueous phase (k _i ) and membrane or organic phase (k _m ) were calculated. The mass transfer coefficients of the aqueous phase and organic phase are 0.42 and 1.67 cm/s, respectively. The mass transfer coefficient of the organic phase is higher than that of the aqueous phase. Therefore, the mass transfer controlling step is the diffusion of the mercury ions through the film layer between the feed solution and the liquid membrane.     

Coupled transport of copper through different commercial supports containing LIX 984 as carrier

The coupled transport of copper(II) ions through a supported liquid membrane containing LIX 984 as the mobile carrier dissolved in kerosene has been studied. Many commercial membrane supports were investigated at different stirrer speeds in a permeation cell. An equation describing the permeation rate has been derived, taking into account stagnant layer aqueous diffusion and liquid membrane diffusion. By means of this treatment the copper overall transfer resistance and the experimental determination of the effective porosity factor (ε/τ), for each support have been performed. The Accurel^® 2E-PP membrane showed a relatively high value of ε/τ (0·91), which makes this membrane an adequate support when the transport properties of the supported liquid membrane are concerned. © 1998 SCI     

Separation of Cobalt and Nickel by Liquid Surfactant Membranes Containing a Synthesized Cationic Surfactant

ABSTRACT

Separation of cobalt(II) and nickel(II) by using a hydroxyoxime extractant has been investigated both in liquid-liquid extraction and in a liquid surfactant membrane(LSM) system. In the liquid-liquid equilibrium extraction studies, hydroxyoximes showed significant extractability for nickel ions, although LIX 84 was found to have exceptional chelating affinity for nickel ions. In the LSM system functionalized by hydroxyoxime, the cobalt ions were efficiently separated from nickel ions as a result of slower permeation of nickel chelates across the emulsion membrane. More complete cobalt recovery was achieved in the LSMs dosed with LIX 860 than when the same carrier was applied to the liquid-liquid extraction system. Furthermore, cobalt permeation rate was enhanced threefold when a quaternary ammonium type of cationic surfactant was used as an emulsifier due to carrier interaction with surfactant at the reaction interface. The permeation mechanism of ions in LSMs was elucidated by an interfacial reaction model which took into account the adsorption of the carrier and surfactant at the reaction interface.     

Separation of Zinc Ions from an Acidic Mine Drainage using a Stirred Transfer Cell–Type Emulsion Liquid Membrane Contactor

Abstract

This is a report on the separation and recovery of zinc ions from an acidic mine drainage using a stirred transfer cell‐type emulsion liquid membrane contactor. Di(2‐ethylhexyl) phosphoric acid was used as a highly selective carrier for the transport of zinc ions through the emulsified liquid membrane. A study was made of the effect on the extraction extent and initial extraction rate of the following variables: pH and initial metal concentration of the feed phase, carrier content in the organic solution, a stripping agent concentration in the receiving phase, and stirring speed in the transfer cell. The content of sulfuric acid as a stripping agent did not show in the studied range any significant influence on metal permeation through the SLM, although a minimum hydrogen ion concentration of 100 g/L is suggested in the internal aqueous solution to ensure an acidity gradient between both aqueous phases to promote the permeation of metal ions toward the strip liquor. Results show that using a pH of 4.0 in the feed acid solution, a concentration of 3% w/w_o of phosphoric carrier in the organic phase and a H₂SO₄ content of 100 g/L in the strip liquor, the extent and rate of extraction through the liquid membrane can be highly favored, pointing to the potential of this method for extracting heavy metals from many kinds of dilute aqueous solutions.     

Rate and mechanism of divalent metal transport through supported liquid membrane containing di(2-ethylhexyl) phosphoric acid as a mobile carrier

The rate and mechanism of copper, cobalt, nickel and zinc transport through a supported liquid membrane containing di(2-ethylhexyl) phosphoric acid as a mobile carrier were studied, respectively. The permeation rate equations have been derived taking into account aqueous film diffusion, interfacial chemical reaction and membrane diffusion as simultaneous controlling steps. The possible rate-controlling steps were estimated by comparing the relative values of the three successive resistances. The measured permeation rates of zinc agreed well with the proposed mechanism in this study.     

KINETICS OF PHENOL EXTRACTION FROM AQUEOUS PHASE BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

The kinetics of the extraction of phenol from the aqueous phase by sulfuric acid salts of trioctylamine (TOA salts) in kerosene and the stripping of phenol from the organic phase by sodium hydroxide solution were studied using a constant interfacial area cell. Measurements of the extraction and stripping rates were made by measuring the time-dependent phenol concentrations in the aqueous phase. It is found that the extraction rate of phenol is strongly dependent on the initial concentration of phenol in the aqueous phase and on the initial concentration of TOA salts in the organic solvent. However, the effect of the total sulfate concentration and the acidic concentration on the extraction rate are not significant. The stripping rate is only a function of the initial concentration of phenol in the TOA salt-organic phase. By analyzing the experimental data, it was recognized that the extraction of phenol occurs at the interface, rather than in the bulk of the solution. The diffusion resistance, rather than the resistance of chemical reaction, is the rate-controlling step for the phenol extraction. Based on the experimental data, simple expressions of the extraction rate and stripping rate of phenol were obtained.     

Extraction of Copper With Liquid Surfactant Membranes

Abstract

Studies of the extraction of copper with liquid surfactant membranes containing a mobile carrier were conducted in a stirred transfer cell. It was found that: (1) the resistance of the diffusion step in liquid surfactant membranes is negligible compared with that of the diffusion step accompanied with chelating complex formation in the outer aqueous solution, (2) the initial rate of copper extraction varied inversely as the 0.5 power of hydrogen-ion concentration in the low-pH range, but in the high-pH range was not affected by hydrogen-ion concentration, (3) the initial rate of copper extraction was proportional to the concentration of benzoylacetone, which is the mobile carrier in the membranes, in the low-pH range, but the rate was scarcely affected by benzoylacetone concentration in the high pH and benzoylacetone concentration ranges. These results are consistent with a model of liquid surfactant membranes which is presented.     

Kinetic Studies of Extraction and Stripping of Copper with Dibenzoylmethane

Abstract

Kinetic studies of the extraction of copper with dibenzoylmethane and the stripping of copper were carried out in a stirred transfer cell, along with a study of the extraction equilibrium of copper with the extractant at 303 K. The extraction and stripping rates were analyzed by a model of the interfacial reaction between the extractant and the adsorbed 1:1 copper chelate complex accompanied by the mass transfer steps of the species. Furthermore, the extraction rate was simulated by using the equilibrium and reaction rate constants obtained from the analysis.     

Recovery of Copper Ions from Wastewater by Hollow Fiber Supported Emulsion Liquid Membrane

Recovery of copper ions from wastewater using a hollow fiber supported emulsion liquid membrane (HFSELM) was studied with LIX984N as carrier, kerosene as diluents, and sulfuric acid solution as strippi...     

New liquid membrane technology for simultaneous extraction and stripping of copper(II) from wastewater

In this paper, a new liquid membrane technique, hollow fiber renewal liquid membrane (HFRLM), is presented, which is based on the surface renewal theory, and integrates the advantages of fiber membrane extraction, liquid film permeation and other liquid membrane processes. The results from the system of CuSO₄+D2EHPA in kerosene+HCl show that the HFRLM process is very stable. The liquid membrane is renewed constantly during the process, the direct contact of organic droplets and aqueous phase provides large mass transfer area. These effects can significantly reduce the mass transfer resistance in the lumen side. Then the mixture of feed phase and organic phase flowing through the lumen side gives a higher mass transfer rate than that of stripping phase and organic phase, because the aqueous layer diffusion of feed phase is the rate-controlling step. The overall mass transfer coefficient increases with increasing flow rates and D2EHPA concentration in the organic phase, and with decreasing initial copper concentration in the feed phase. The overall mass transfer coefficient also increases with increasing pH in the feed phase, and reaches a maximum value at pH of 4.44, then decreases. Also, there is a favorable w/o volume ratio of 20:1 to 30:1 for this process. Compared with hollow fiber supported liquid membrane and hollow fiber membrane extraction processes, HFRLM process has a high mass transfer rate. Mathematical model for the HFRLM process based on the surface renewal theory is developed. The calculated results are in good agreement with experimental results under the conditions studied.     

Analysis of Transport Rate of Zinc Extraction through Liquid Surfactant Membrane

Abstract

Analysis of the transport rate of a metal ion through a liquid surfactant membrane is important for understanding an extraction system. A facilitated transport model for zinc extraction through a liquid surfactant membrane is proposed for the analysis of the transport rate. Based on the model, the transport rates, including the interfacial reaction rates and the diffusion rate of the zinc ion, are analyzed. From an analysis of the model, it is shown that the reactions at both interfaces are not in equilibrium before extraction is complete. It is also shown that the transport rates are not equal value in the early stage of a run. Parametric effects on the transport rates are also illustrated.     

Flüssigmembran-Technik – Übersicht über Phänomene,Transportmechanismen und Modellbildungen

Liquid membrane technology – A survey of associated phenomena, transport mechanisms, and models. Liquid membrane permeation is the name given to a simultaneous extraction/stripping process. A summary of related phenomena, mass transfer, and models is presented. A new model has been developed to describe mass transfer in liquid membranes, in which the spherical droplets serve as reaction centres. An account of present applications demonstrates the limitations of liquid membrane processes.     

Auslegungskriterien für die Extraktion mit chemischer Reaktion und Flüssigmembran-Permeation

Design criteria for extraction with chemical reaction and liquid membrane permeation. Design criteria for extraction and liquid membrane permeation are discussed and related to these classical extraction columns. Well known models, like the diffusion and the forward mixing model, are used to describe the concentration profile in a column. Mass transfer models for a single globule, like the two-layer and the shrinking core model, are incorporated. The complex chemical interactions on an interface are formulated. A final discussion considers the relevance of the model parameters and their influence on mass transfer.