Facilitated Transport of Zinc Chloride through Hollow Fiber Supported Liquid Membrane. Part 2. Membrane Stability

Abstract

The stability of a hollow fiber supported liquid membrane of tri-n-octylamine diluted in n-dodecane with 2-ethylhexyl alcohol was examined for the facilitated transport of zinc chloride. The liquid membrane was unstable when the feed and the strip aqueous solutions were not saturated with the organic phase used as the liquid membrane. This was found to be due to the dissolution of relatively soluble 2-ethylhexyl alcohol to the aqueous phases. When both aqueous phases were presaturated with the organic phase used, a rather constant flux could be maintained for a long time by the reimpregnation of the organic phase approximately once a day. The continuous impregnation of the organic phase to the support membrane drastically increased the stability of the liquid membrane, even without presaturation of the two aqueous phases with the organic phase     

Facilitated Transport of Zinc Chloride through Hollow Fiber Supported Liquid Membrane. Part 3. Module Operation

Abstract

The third paper of this series of three papers on the facilitated transport of zinc chloride through a hollow fiber supported liquid membrane of tri-n-octylamine diluted in n-dodecane with 2-ethylhexyl alcohol deals with module operation. The Type A module, in which 300 polyethylene fibers were simply bundled, revealed that only a fraction of the total surface was effective. The Type B module, with a sheet of glass fiber cloth as a spacer and a cross-flow arrangement of the outside strip solution, showed the same performance as with single fiber operation. The continuous impregnation discussed for a single fiber operation in the second paper was demonstrated to be effective by a Type C module     

Transport studies of iodine through liquid membrane system

Transport of iodine by a charge-transfer mechanism through a bulk organic liquid membrane system containing calixarene based on donor-type carriers was studied. It was found that the transport of iodine is facilitated by n-donor carriers depending on the pH of the source phase. The color of iodine solutions on the source side turned from brown to colorless. The passage of iodine through the organic bulk liquid membrane was governed by donor-acceptor interaction between n-donor atoms in the carrier and σ-acceptor (iodine atoms) and by the diffusion of an n–σ-type charge-transfer complex in the membrane followed to release by the Lewis acid-base interaction in the aqueous phase. The transport by the new carrier arises both from the different extraction equilibrium constants between the aqueous phase and donor–acceptor interaction with iodine and the carrier in the organic phase. © 1996 John Wiley & Sons, Inc.     

Influence of Membrane Solvent on Strontium Transport from Reprocessing Concentrate Solutions through Flat-Sheet-Supported Liquid Membranes

Abstract

The influence of membrane solvents on strontium transport from nuclear fuel reprocessing concentrate solutions to demineralized water through a flat-sheet-supported liquid membrane has been studied using dicyclohexano-18-crown-6 as the extractant and Celgard 2500 as the solid support. Even though the highest values of the distribution coefficients of strontium were obtained with nitrated compounds as membrane solvents, strontium permeabilities were determined only when a membrane solvent was used for which stable SLMs were obtained. Among the latter, the use of 4-nonylphenol as a phase modifier is not satisfactory for long-term strontium transport experiments due to its reactivity with the nitric acid of the aqueous feed solution. We achieved a good correlation between strontium permeability and two parameters of the membrane diffusion coefficient (molecular weight and viscosity of the membrane solvent) for aromatic solvents modified with isotridecanol or 1-decanol. The best results were obtained with n-hexylbenzene (0.7 mol·L^?1 isotridecanol) which should lead to a high strontium decontamination by hollow-fiber-supported liquid membranes. The transport of nitric acid and nonradioactive cations through the membrane was not greatly influenced by the membrane solvent used.     

Transport of Iron and Cobalt Complex Ions through Liquid Membrane Mediated by Methyltrioctylammonium Ion with the Aid of Redox Reaction

Abstract

A new type of carrier-mediated metal transport through liquid membrane is presented. The system involves redox reactions rather than acid-base reactions which have often been utilized in metal transport systems. Iron ion was selectively transported and concentrated through the membrane via a chloride complex by use of a lipophilic quaternary ammonium ion, methyltrioctylammonium (MTOA, Q⁺), as a carrier. The two aqueous solutions of different redox potentials were separated by a polymer-supported liquid membrane in which MTOA · chloride (Q⁺·CI^?) was dissolved as the carrier. Iron(III) ion in hydrochloric acid media formed a FeCl₄ ^? type complex which was readily extracted to the organic membrane phase as an ion-pair complex Q⁺·FeCl₄ ^?. On contact with a reducing agent on the other side of the membrane, iron(III) was reduced to iron(II) and liberated into aqueous solution; the chloride complexes of iron(II) are too hydrophilic to stay in the membrane phase. On the other hand, cobalt ion was transported via nitrilotriacetic acid (NTA) complex by MTOA carrier in a similar manner to the iron transport. The nature of the transport reactions was studied under various operational conditions (redox agents, carrier and ligand concentration, pH, coexisting metals, etc.). The extension of these transport reactions to a water-in-oil-in-water type emulsion system as well as to a photoassisted transport system was studied.     

Modeling of Amine-Facilitated Liquid Membrane Transport of Binary Organic Acids

ABSTRACT

The transport rates of lactic and citric acids from binary solutions across supported liquid membranes containing tri-n-ocytylamine are measured. A mass transfer model is proposed which considers aqueous film diffusion, interfacial chemical reaction, and membrane diffusion. It is shown that the difference between the measured and modeled rates was more significant at high total acid and amine concentrations. This could be partly due to the ignorance of mutual interactions between the acids in the aqueous phase and the complexes in the membrane phase in this model (chemical effect), and to limited validity of “fixed” transport properties over a rather wide concentration range (mechanical effect).     

Transport of Eu3+ through a Bis(2-ethylhexyl)-phosphoric Acid,n-Dodecane Solid Supported Liquid Membrane

Abstract

The coupled transport of Eu³⁺ and H⁺ ions through a solid supported liquid membrane consisting of a porous polypropylene film immobilizing an HDEHP solution in n-dodecane has been studied as a function of the membrane area, stirring speed of the aqueous solutions, membrane composition, and acidity of the feed solution. The experimental results are in agreement with predictions derived from a theoretical permeability coefficient equation which assumes that membrane diffusion and aqueous film diffusion are the only rate-controlling factors.     

Transport of Chromium(VI) through a Supported Liquid Membrane Containing Tri-n-octylphosphine Oxide

ABSTRACT

In this study the transport of chromium(VI) from aqueous solutions of pH 2–4 through a supported liquid membrane (SLM) with tri-n-octylphosphine oxide (TOPO) dissolved in kerosene as a mobile carrier was investigated. The transport flux of Cr(VI) increased with an increase in the concentrations of Cr(VI) in the feed phase and of TOPO in the membrane phase, but with a decrease in pH of the feed phase. Considering the equilibria of various Cr(VI) species in the aqueous phase and of the Cr(VI)—TOPO complexes formed in the membrane phase, a permeation model including the aqueous film diffusion of HCrO₄ ^? and Cr₂O₇ ^2? toward the membrane, the interfacial chemical reaction between them and TOPO, and the membrane diffusion of the Cr(VI)—TOPO complexes (H₂CrO₄(TOPO) and H₂Cr₂O₇(TOPO)₃) was proposed to describe the transport of Cr(VI) through the SLM. By best fitting the transport flux equations of Cr(VI) with the experimental data using the Rosenbrock method, the apparent mass-transfer coefficients of HCrO₄ ^? and Cr₂O_7^. across the aqueous film, and those of H₂CrO₄(TOPO) and H₂Cr₂O₇(TOPO)₃ across the membrane phase, were obtained. This work helps to clarify the transport mechanism of Cr(VI) through an SLM.     

Coupled transport of Pb2+ through tri‐n‐octylamine‐xylene‐polypropylene supported liquid membranes

Transport of Pb²⁺ was carried from acidic solution into alkaline stripping phase through tri‐n‐octylamine‐xylene‐polypropylene supported liquid membrane. The transport of Pb²⁺ through the membrane was studied by varying the concentration of Pb²⁺ and HNO₃ in feed solution, NaOH concentration in strip solution and TOA concentration in membrane phase. The flux data obtained has been used to study the stoichiometry of complex Pb(NO₃)_n+2(HNR₃)_n. The supported liquid membrane (SLM) has been found stable for 10 runs with 24 h between each run. This SLM has been used effectively to extract lead ions along with chromium, copper and zinc ions from aqueous acidic leached solution of paint and industrial effluents. © 2012 Canadian Society for Chemical Engineering     

Facilitated Transport of Gold through a Membrane via Complexation to Thiourea-Based Reagents

Abstract

The facilitated transport of Au(III) from hydrochloric acid solutions through double solid supported liquid membranes (SSLMs) is reported. The organic phase consisted of a chloroform solution of thiourea-based extraction reagents, dodecyl-thiourea (DTH) or nonylthiourea (NTH), physically absorbed onto microporous polypropylene films, Celgard 2500 or Celgard 2400 (Celanese Plastic Inc.). A cell composed of three compartments, including a reservoir of organic solution, with double SSLM was used in this study. Aqueous solutions of thiourea, KSCN, or Na₂S₂O₃ were used for removing Au(III) from the membrane phase. The permeability coefficient, P, of the SSLM was determined from the slope of Iog[Au]/[Au]_o or log A/A_o vs time plot. The influences of the stirring rate in aqueous feed and organic solutions, of the stripping reagents and their concentration, of the carrier concentration, and of the concentration of HCl in the aqueous feed on the permeability coefficient were determined. A model describing the transport mechanism consisting of diffusion through a feed aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion through the membranes is reported. The study also demonstrates the suitability of the liquid membrane technique to use reagents with low solubility in organic solutions for the permeation of Au³⁺ without problem of solid-phase formation.

     

Highly Efficient Liquid Membrane Transport of Dyes Using Calix[4]arene-Linked Triphenylene Dimers as Carriers

The extraction of dyes from aqueous phase to organic phase using calix[4]arene-linked triphenylene dimers (1a and 1b) with large π-cavity as extractants were examined. 1a and 1b showed outstanding extraction percentage for four common dyes [Orange G sodium salt (OG), Brilliant ponceau (BP), Methyl Green (MG), and Xylenol Orange disodium salt (XO)]. The highest extraction percentage of 1a was 95% for MG. Moreover, the abilities of liquid membrane transport of 1a and 1b for dyes were studied. The influences of pH value, concentration, solvent, stirring speed, and the temperature on liquid membrane transport was investigated to optimize the transport condition. The results of liquid membrane transport suggested 1a and 1b were excellent carriers for tested dyes with high fluxes. The high concentration in the source phase or membrane phase, CH₂Cl₂, high stirring speed, and low temperature were favorable for the efficiency of liquid membrane transport. The high extraction percentages and outstanding liquid membrane transport abilities indicated that 1a and 1b possessed excellent complexation for dyes based on the π-π stacking action between dyes and triphenylene units.     

Highly Efficient and Selective Transport of Au(III) through a Bulk Liquid Membrane using Potassium-dicyclohexyl-18-crown-6 as Carrier

Abstract

The facilitated transport of Au(III) through a chloroform bulk liquid membrane containing potassium-dicyclohexyl-18-crown-6 as a selective ion carrier was designed. Au(III) as [AuBr₄]^?, quantitatively transported across the liquid membrane. In the receiving phase, L-cysteine acts as a specific stripping agent. The amount of Au(III) transported through the liquid membrane after 120 minutes was (96.2±1.3)%. The type of halide and its concentration, pH of source and receiving phase and also the type of stripping agents were optimized. The selectivity and efficiency of gold(III) transport from aqueous solutions containing various metal ions were investigated. The presence of EDTA in the source phase diminished drastically the competitive effect of interfering metals ion.     

Transport of Hg2+ Ions across a Supported Liquid Membrane Containing Calix[4]arene Nitrile Derivatives as a Specific Ion Carrrier

Abstract

The transport behavior of Hg²⁺ from aqueous solution through a flat‐sheet‐supported liquid membrane (SLM) has been investigated by using of calix[4]arene derivatives (1 and 2) as carriers and Celgrad 2400 and 2500 as the solid support. The effect of solvent type and anions such as chloride and nitrate ions on the transport of Hg²⁺ was examined. Danesi mass transfer model was used to calculate the permeability coefficients for each parameter studied. The highest values of permeability were obtained with 2‐nitrophenyl ethyl ether (NPOE) solvent and the influence was found to be in the order, NPOE>chloroform>xylene. The transport efficiency on the supported liquid membrane was dependent on the type of carrier, its characteristics, and the type of the solvent.     

Highly Copper(II) Ion‐Selective Transport Through Liquid Membrane Containing N,N′‐bis(salicylidene)‐1,2‐phenyldiamine

Abstract

N,N′‐bis(salicylidene)‐1,2‐phenyldiamine was synthesized for examining their ability to extract and transport Cu²⁺ through a liquid membrane. By using hydrazine sulfate and potassium thiocyanate as reducing agent and acceptor respectively in the receiving phase at the optimum pH of 1.5, the amount of copper transported across the liquid membrane after 3.5 hours was 96%. The selectivity and efficiency of copper transport from aqueous solution containing various metal ions were investigated.     

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.     

Separation of Ethyl Esters of Eicosapentaenoic Acid and Docosahexaenoic Acid by Circulating Liquid Membranes Using Silver Nitrate as a Carrier. Uphill Transport by Use of Temperature and Solvent Dependencies of Distribution Ratio

Abstract

Experiments on the separation of ethyl ester of eicosapentaenoic acid (EPA-Et) and that of docosahexaenoic acid (DHA-Et) contained in ethyl ester of bonito oil (bonito oil-Et) were performed using circulating liquid membranes (CIRLMs) containing sliver nitrate as a carrier. In this liquid membrane system an aqueous silver nitrate solution was circulated between a stirred vessel containing an organic solution of bonito oil-Et and another stirred vessel containing a receiving organic solvent. Using the CIRLM, two types of uphill facilitated transport of EPA-Et and DHA-Et in bonito oil-Et were demonstrated. The first type utilizes the distribution ratio of EPA-Et and DHA-Et, defined as the ratio of the concentration in the aqueous phase to that in the organic phase at equilibrium, which is remarkably dependent on the temperature, and the second uphill transport was based on the fact that the distribution ratio is considerably dependent on the solvent of the organic phase. A model of permeation through the circulating liquid membrane was proposed to explain the experimental results.     

Studies on Carbonate Ion Transport through Supported Liquid Membrane Using Primene JMT and Tributyl Phosphate

Abstract

A supported liquid membrane system consisting of source, receiving and membrane phases, in which mixed extractants were used in the membrane phase, was explored for the carbonate ion transport from source to receiving through membrane phase. Primary amine Primene JMT and TBP were used as extractants (carriers) in liquid membrane phase. Different experimental variables such as concentration of carbonate ion, carriers, alkali and hydrogen peroxide, stirring speed, etc have been investigated. Primary amine Primene JMT and TBP mixed carriers show the synergistic effect for the transport of carbonate ions through supported liquid membrane system. The stability of the supported liquid membrane system has been explored for 50 h. The pre-concentration of carbonate ions from dilute solutions were also demonstrated. The effect of different alkalis on the permeability coefficient of transport of carbonate ions through supported liquid membrane system has been investigated. The primary amine in combination with TBP shows more effective for the transport of carbonate ions through supported liquid membrane system in comparison with that of secondary and tertiary amines.     

Liquid Membrane Transport of Hg(II) by an Azocalix[4]arene Derivative

Abstract

A kinetic study of Hg(II) transport from an aqueous donor solution into an aqueous acceptor solution through a liquid membrane containing 25,26,27–tribenzoyloxy‐28‐hydroxy‐5,11,17,23‐tetra‐(4‐n‐butylphenylazo)calix[4]arene 1 as a carrier was studied. The kinetic parameters (k ₁, k ₂, R _m ^max, t _max, J _d ^max, J _a ^max) for the transport were investigated in terms of the effect of temperature, the stirring rate, the carrier concentration, and the type of solvent. The kinetics of transport was analyzed in the formalism of two consecutive irreversible first‐order reactions. The membrane entrance rate, and exit rate constants were increased with increasing of temperature stirring rate, and carrier concentration. The membrane entrance rate and exit rate constants depended on the type of solvent and was found to be in order of CH₂Cl₂> CHCl₃> CCl₄. The activation energy values are calculated as 30.67±2.64 and 57.33±4.90 kj mol^?1 for extraction and reextraction, respectively. The values of calculated activation energy indicate that the process is diffusionally controlled by species.     

Bathocuproine-Mediated Copper Transport through Liquid Membrane Driven by Redox Potential

Abstract

A new type of carrier-mediated copper transport system driven by redox potential was studied. The two aqueous solutions of different redox potentials were separated by a polymer-supported organic liquid membrane in which Bathocuproine (L) was dissolved as a “carrier”. Copper(II) was reduced in the reducing phase to form [Cu¹L₂]⁺·X^? type complex at the membrane interface and extracted. The copper complex diffused to the other side of the membrane and decomposed to form the copper(II) species in the oxidizing phase, leaving the carrier in the membrane phase. The nature of the system under various operational conditions (pH, redox agents, pairing anions X^?, coexisting metals, etc.) was studied and compared with the metal transport system which can take place without the intervention of redox reaction. An extension of these transport reactions to water-in-oil-in-water type emulsion system was studied.     

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.