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Liquid Membrane (liquid + membrane)
Kinds of Liquid Membrane Selected AbstractsIntegrated Microanalytical System Coupling Permeation Liquid Membrane and Voltammetry for Trace Metal Speciation.ELECTROANALYSIS, Issue 10 2004Optimization, Technical Description Abstract A new minicell coupling the liquid-liquid extraction technique called permeation liquid membrane (PLM) with an integrated Ir-based Hg-plated microelectrode array for voltammetric detection has been developed for the speciation of heavy metals in natural waters. Lead and cadmium have been used as model compounds. The PLM consists of a carrier (0.1,M 22DD+0.1,M lauric acid) dissolved in 1,:,1 mixture of toluene/phenylhexane held in the small pores (30,nm) of a hydrophobic polypropylene membrane (Celgard 2500). One side of this membrane is in contact with a flowing source solution, containing the metal ions of interest. An acceptor or strip solution (pyrophosphate) is placed on the other side of the PLM with the microelectrode array placed at 480,,m of the PLM. The analyte is transported by the carrier from the source solution to the strip solution. The originality of the new minicell is that accumulation in the strip solution is voltammetrically followed by the integrated microelectrode array in real time, and at low concentration level, using square-wave anodic stripping voltammetry (SWASV). In order to protect the Hg microelectrodes from the adsorption of the hydrophobic carrier, the microelectrodes are embedded in a thin gel layer (280,,m) of 1.5% LGL agarose gel containing 10% of hydrophobic silica particles C18. The choice of optimum conditions is discussed in details in this article. Due to the very small effective strip volume of the new cell (less than 1,,L), high enrichment factor can be obtained (e.g., 330 for Pb) after 2,hours of accumulation. No deaeration of the solutions is required for SWASV measurements. Detection limits under these conditions are 2,pM and 75,pM for Pb and Cd, respectively, using a voltammetric deposition time of 5,min. In addition, no fouling effects were observed with natural water samples. [source] Advances in the Study of Ion Transfer at Liquid Membranes with Two Polarized Interfaces by Square Wave VoltammetryELECTROANALYSIS, Issue 14 2010A. Molina Abstract A general analytical expression has been deduced for the I/E response of the square wave voltammetry corresponding to ion transfer processes in systems with two liquid/liquid polarized interfaces. This expression has been evaluated through the experimental study of a series of quaternary ammonium cations and metal chloro complex anions. We have found that systems with two liquid/liquid polarizable interfaces present the striking advantage that the difference between peak potentials of square wave voltammograms of cations and anions with similar standard ion transfer potential is much greater than in systems with a single polarizable one. [source] Quantitative Removal of Mercury(II) from Water Through Bulk Liquid Membranes by Lipophilic PolyaminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2006Nicoletta Spreti Abstract Transport of mercury(II) and copper(II) ions through bulk liquid membranes has been studied, the former because of its toxicity and wide distribution in the environment, the latter for comparative purposes. The abilities of two carriers, the known N,N, -bis[2-(hexadecylamino)ethyl]- N,N, -bis(hydroxyethyl)ethylenediamine (bis-HE16ED) and the new N,N,-bis(p -octyloxybenzyl)-3,6-dioxaoctane-1,8-diamine (bis- pODODA), to complex and transport the selected metal ions are reported. Bis-HE16ED is a good carrier for Cu2+ ions, but the high stability of the carrier/Hg2+ ion complex in the membrane results in a lack of its transport. On the other hand, the new carrier displays a very high efficiency in Hg2+ ion transport, effecting quantitative transfer of the metal ion into the receiving phase within 24 h, despite its chelating region being only slightly different from that in bis-HE16ED. The ability of bis- pODODA to transport 100,% of Hg2+ efficiently in consecutive cycles is also reported. This result provides a basis for future development of a decontamination process based on a carrier-mediated transport system. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A New Carrier for Selective Removal of Heavy Metal Ions from Aqueous Solutions through Bulk Liquid MembranesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2004Nicoletta Spreti Abstract The carrier-mediated transport of heavy metal ions through bulk liquid membranes has been examined: toxic Hg2+, Cd2+ and Pb2+ ions were studied, along with Cu2+ ions for comparative purposes. The ability of a new carrier, 2,2,-bis(p -octyloxybenzyl)diethylenetriamine (bis- pODET), to complex and transport all the selected metal ions is reported. Differing affinities of the carrier for the different metal ions and the different experimental conditions required for their release into the receiving phase allowed the selective separation of equimolar binary mixtures. For Hg2+/Cd2+ and Hg2+/Pb2+ mixtures, two different separation methods were performed, while the inefficacy of the separation of Cd2+/Pb2+ and Hg2+/Cu2+ mixtures was for two different reasons: (i) the carrier is able to extract the metal ions with similar levels of ability, and (ii) the carrier metal ion complexes require the same acidity of the receiving phase to release the metal ions. The capability of the carrier to transport Hg2+ efficiently in consecutive cycles is also reported: over 90% of the metal ions were transferred into the receiving phase for three consecutive processes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Carrier-Mediated Transport of Toxic Heavy Metal Ions in Bulk Liquid MembranesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2004Lucia Brinchi Abstract Transport through a dichloromethane liquid membrane has been studied to investigate the ability of 1,1,7,7-tetraethyl-4-tetradecyldiethylenetriamine (TE14DT), previously tested for the transport of copper, to act as a carrier for toxic heavy metal ions such as Cd2+, Pb2+ and Hg2+. The carrier displayed a remarkable capability to extract all the metal ions from the source to the organic phases but only cadmium was efficiently transported across the membrane. The experimental conditions optimised for the transport of copper are inadequate for lead and mercury. In fact, the inefficacy of their transport could be due, as regards lead, to the slow diffusion of the complex through the membrane, while mercury remained in the organic phase because of the high stability of the mercury-carrier complex. Selectivity tests using binary mixtures of the metal ions showed TE14DT's capability to transport copper or cadmium also in the presence of lead in the source phase. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] An overview of the mathematical modelling of liquid membrane separation processes in hollow fibre contactorsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2009E Bringas Abstract Liquid membranes have traditionally been employed for liquid/liquid mass transfer and have found applications in industrial, biomedical and analytical fields as well as in hydrometallurgical processes, wastewater treatment and remediation of polluted groundwater. However, in spite of the known advantages of liquid membranes, there are few examples of industrial application. The development of reliable mathematical models and design parameters (mass transport coefficients and equilibrium or kinetic parameters associated with the interfacial reactions) is a necessary step for design, cost estimation, process optimisation and scale-up. This work reports an overview of the different approaches that have been proposed in the literature to the mathematical modelling of liquid membrane separation processes in hollow fibre contactors providing, at the same time, a useful guideline to characterise the mass transport phenomena and a tool for the optimal design and intensification of separation processes. Copyright © 2009 Society of Chemical Industry [source] Integrated Microanalytical System Coupling Permeation Liquid Membrane and Voltammetry for Trace Metal Speciation.ELECTROANALYSIS, Issue 10 2004Optimization, Technical Description Abstract A new minicell coupling the liquid-liquid extraction technique called permeation liquid membrane (PLM) with an integrated Ir-based Hg-plated microelectrode array for voltammetric detection has been developed for the speciation of heavy metals in natural waters. Lead and cadmium have been used as model compounds. The PLM consists of a carrier (0.1,M 22DD+0.1,M lauric acid) dissolved in 1,:,1 mixture of toluene/phenylhexane held in the small pores (30,nm) of a hydrophobic polypropylene membrane (Celgard 2500). One side of this membrane is in contact with a flowing source solution, containing the metal ions of interest. An acceptor or strip solution (pyrophosphate) is placed on the other side of the PLM with the microelectrode array placed at 480,,m of the PLM. The analyte is transported by the carrier from the source solution to the strip solution. The originality of the new minicell is that accumulation in the strip solution is voltammetrically followed by the integrated microelectrode array in real time, and at low concentration level, using square-wave anodic stripping voltammetry (SWASV). In order to protect the Hg microelectrodes from the adsorption of the hydrophobic carrier, the microelectrodes are embedded in a thin gel layer (280,,m) of 1.5% LGL agarose gel containing 10% of hydrophobic silica particles C18. The choice of optimum conditions is discussed in details in this article. Due to the very small effective strip volume of the new cell (less than 1,,L), high enrichment factor can be obtained (e.g., 330 for Pb) after 2,hours of accumulation. No deaeration of the solutions is required for SWASV measurements. Detection limits under these conditions are 2,pM and 75,pM for Pb and Cd, respectively, using a voltammetric deposition time of 5,min. In addition, no fouling effects were observed with natural water samples. [source] Voltammetric Elucidation of Ion Transfer Through an Extremely Thin MembraneELECTROANALYSIS, Issue 9 2004Nobuyuki Ichieda Abstract Digital simulation of the cyclic voltammogram for the ion transfer through a liquid membrane of thickness from 1,mm to 10,nm was performed. The magnitude of current and the shape of the voltammogram simulated for extremely thin membrane (10,nm thick) were similar to those observed experimentally with a bilayer lipid membrane, BLM, of about 10,nm in thick, when the diffusion coefficient of an ion in the BLM was assumed to be extraordinary small (10,13 to 10,14,cm2 s,1). [source] Combined use of supported liquid membrane and solid-phase extraction to enhance selectivity and sensitivity in capillary electrophoresis for the determination of ochratoxin A in wineELECTROPHORESIS, Issue 7 2008Sara Almeda Abstract This paper proposes a novel strategy to enhance selectivity and sensitivity in CE, using supported liquid membrane (SLM) and off-line SPE simultaneously. The determination of ochratoxin A (OA) in wine has been used to demonstrate the potential of this methodology. In the SLM step, the donor phase (either a 20,mL volume of a standard solution at pH,1 or a wine sample at pH,8) was placed in a vial, where a micromembrane extraction unit accommodating the acceptor phase (1,mL water, pH,11) in its lumen was immersed. The SLM was constructed by impregnating a porous Fluoropore Teflon (PTFE) membrane with a water-immiscible organic solvent (octanol). In the off-line SPE step, the nonpolar sorbent (C-18, 4,mg) selectively retained the target ochratoxin, enabling small volumes of acceptor phase (1,mL) to be introduced. The captured analytes were eluted in a small volume of methanol (0.1,mL). This procedure resulted in sample cleanup and concentration enhancement. The method was evaluated for accuracy and precision, and its RSD found to be 5%. The LODs for OA in the standard solutions and wine samples were 0.5 and 30,,g/L, respectively. The results obtained demonstrate that SLM combined with off-line is a good alternative to the use of immunoaffinity columns prior to CE analysis. [source] New supported liquid membrane-capillary electrophoresis in-line arrangement for direct selective analysis of complex samplesELECTROPHORESIS, Issue 15 2006Leonor Nozal Abstract An in-line coupling of a micro-membrane extraction unit, based on supported liquid membrane, with commercially available capillary electrophoresis equipment is described. A main characteristic of this micro-membrane device, made from a simple Eppendorf tube, is that it permits the application of voltage in the acceptor solution to be applied during the extraction process. This has been shown as an alternative to enhance sensitivity, as the analytical signal achieved by applying 10,kV for 20,min was similar to that obtained without the application of voltage and with extraction time of 60,min. In addition, the design has been made permitting both in-line hydrodynamic and electrokinetic sample introduction into the electrophoretic capillary. The analytical potential of the proposed system has been demonstrated by the direct determination of nitroimidazoles from pig liver tissue. The high efficiency of the proposed system allowed the extraction and the determination of the analytes to be performed from a simple tissue homogenate obtained in water. The precision of the analysis of spiked samples, expressed in terms of relative standard deviation, was better than 4.8%. [source] Carrier-Mediated Transport of Toxic Heavy Metal Ions in Bulk Liquid MembranesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2004Lucia Brinchi Abstract Transport through a dichloromethane liquid membrane has been studied to investigate the ability of 1,1,7,7-tetraethyl-4-tetradecyldiethylenetriamine (TE14DT), previously tested for the transport of copper, to act as a carrier for toxic heavy metal ions such as Cd2+, Pb2+ and Hg2+. The carrier displayed a remarkable capability to extract all the metal ions from the source to the organic phases but only cadmium was efficiently transported across the membrane. The experimental conditions optimised for the transport of copper are inadequate for lead and mercury. In fact, the inefficacy of their transport could be due, as regards lead, to the slow diffusion of the complex through the membrane, while mercury remained in the organic phase because of the high stability of the mercury-carrier complex. Selectivity tests using binary mixtures of the metal ions showed TE14DT's capability to transport copper or cadmium also in the presence of lead in the source phase. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and metal transport ability of a new series of thiamacrocycles containing thiol and disulfide groups inside the ringHETEROATOM CHEMISTRY, Issue 4 2001Tatsuya Nabeshima Synthetic methods for thiamacrocycles containing two thiol groups or a disulfide linkage and their abilities to effect single heavy-metal-ion transport across a liquid membrane were examined. High Ag+ selectivity was accomplished by the thiol or disulfide hosts, although all the corresponding crown ether analogs bearing a disulfide group showed no Ag+ selectivity. The difference of the transport preferences among the thiacrown ethers prepared here is considered to be reflected by the position and the number of the sulfur atoms ligating to Ag+ and the cavity size of the hosts. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:276,281, 2001 [source] Liquid membrane technology: fundamentals and review of its applicationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2010M. F. San Román Abstract OVERVIEW: During the past two decades, liquid membrane technology has grown into an accepted unit operation for a wide variety of separations. The increase in the use of this technology owing to strict environmental regulations and legislation together with the wider acceptance of this technology in preference to conventional separation processes has led to a spectacular advance in membrane development, module configurations, applications, etc. IMPACT: Liquid membrane technology makes it possible to attain high selectivity as well as efficient use of energy and material relative to many other separation systems. However, in spite of the known advantages of liquid membranes, there are very few examples of industrial applications because of the problems associated with the stability of the liquid membrane. APPLICATIONS: Liquid membrane technology has found applications in the fields of chemical and pharmaceutical technology, biotechnology, food processing and environmental engineering. On the other hand, its use in other fields, such as in the case of hydrogen separation, the recovery of aroma compounds from fruits, the application of ionic liquids in the membrane formulation, etc., is increasing rapidly. Copyright © 2009 Society of Chemical Industry [source] Cobalt removal from waste-water by means of supported liquid membranesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2009Kim Verbeken Abstract BACKGROUND: Supported liquid membranes (SLM) are an alternative technique to remove and recover metals from diluted process solutions and waste-water. In the present work, the removal of Co(II) from a synthetic CoSO4 solution containing initial amounts of cobalt(II) in the range 100,200 ppm (0.1,0.2 g dm,3) has been studied on a pilot scale. By performing batch equilibrium experiments, the optimal settings, i.e. the composition of the organic phase, the pH of the feed, the type and concentration of the stripping agent were determined. RESULTS: It is shown that the equilibrium characteristics of a synergistic extractant mixture containing di-2-ethyl-hexylphosphoric acid (D2EHPA) and 5-dodecylsalicylaldoxime (LIX 860-I) are superior to D2EHPA. Both hydrochloric acid and sulfuric acid have been evaluated as stripping solutions in liquid,liquid extraction tests and as the receiving phase in a SLM configuration. Although equilibrium tests showed no difference in stripping characteristics between both chemicals, it was observed that in a SLM configuration the stability of the system when hydrochloric acid is used is poor. With a commercially available SLM module (Liqui-Cel Extra-Flow 4 × 28) having a surface area of 19 m2, a steady Co(II) flux of 0.140 gm,2h,1 has been obtained at influent concentrations of cobalt between 100 and 200 ppm with 3 mol dm,3 sulfuric acid as stripping phase. CONCLUSIONS: The results obtained show that a supported liquid membrane containing a synergistic mixture of LIX 860-I and D2EHPA gives the possibility of recovering cobalt from dilute solutions. Copyright © 2008 Society of Chemical Industry [source] Influence of temperature on mass transfer in an incomplete trapping supported liquid membrane extraction of triazole fungicidesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2009Luke Chimuka Abstract The influence of temperature in a supported liquid membrane (SLM) extraction of triazole fungicides was investigated. The mass transfer parameters such as diffusion coefficient, flux and apparent viscosity were determined at temperatures ranging from 5 to 40°C. Increase in temperature led to an increase in diffusion coefficient and flux with a flowing acceptor solution. The apparent viscosity also decreased with an increase in temperature. However, the increase in mass transfer parameters did not result in an overall increase in extraction efficiency with a stagnant or circulation acceptor phase. Stripping of the analytes from the membrane into the acceptor phase as well as the configuration of the extraction unit could have limited the influence of temperature on mass transfer. The partition coefficient of analytes from the acceptor solution to the membrane, KA, was found to be much higher than that from the donor solution to the membrane KD, thus triazole compounds preferred to remain in the membrane even with an increased extraction temperature. [source] Hydrophobicity-aided potentiometric detection of catecholamines, beta-agonists, and beta-blockers in a mixed-solvent capillary electrophoresis systemJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2009Grzegorz Bazylak Abstract A series of cationic drug-like substances with distinct basicity, hydrogen-bonding ability, and hydrophobicity, including three catecholamines, two beta-agonists, and thirteen beta-blockers, was successfully detected in a capillary electrophoresis system using an end-capillary coupled potentiometric sensor consisting of a PVC-based liquid membrane deposited directly on a 100 ,m diameter copper rod. The electrophoretic separation was performed on a 72 cm×75 ,m id uncoated fused-silica capillary with an acidic background electrolyte containing phosphoric acid in a water,acetonitrile mixture, pH* 2.8. Samples were injected electrokinetically at 5.0 kV for 10 s and a running voltage of 19.5 kV was applied. Excluding the bufuralol/practolol pair, baseline separation of all substances was achieved in the developed CE system within 9 minutes. A linear relationship (R2 0.8752) between the sensitivity of the applied potentiometric detector and the parameter log P characterising the hydrophobicity of the analytes was demonstrated. The best observable limits of detection (LODs) were obtained for the highly hydrophobic substances, i. e. bufuralol (8.10×10,8 M injected concentration, S/N = 3), propranolol, alprenolol, and clenbuterol (ca. 1.10×10,7 M). In the case of hydrophilic catecholamines and carbuterol their LODs with potentiometric detection were lowered by a factor of almost one thousand, reaching a value of 6.6×10,5 M. [source] Hollow-fibre supported liquid membrane extraction for determination of fluoxetine and norfluoxetine concentration at ultra trace level in sewage samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15 2007Saioa Zorita Abstract In this study, a method was developed for determining the concentration of the pharmaceutical fluoxetine and its metabolite, norfluoxetine, in sewage water samples. Sample preparation was performed by hollow-fibre supported liquid membrane (HF-SLM) extraction with final analysis using liquid chromatography with UV detection. Several parameters were studied including type of organic solvent, sample and acceptor pH, and salt and humic acid content. The optimised method allowed determination of the analyte at the ng/L level in sewage water. A linear plot gave a correlation coefficient better than 0.991 for both analytes and resulted in limits of detection in sewage water of 11 and 12 ng/L, for fluoxetine and norfluoxetine, respectively. The enrichment factor was over 1700 for both analytes in sewage water. The repeatability and reproducibility were better than 8% and 17%, respectively. The developed methodology was used to study daily variations of fluoxetine and norfluoxetine in municipal sewage streams. Norfluoxetine has been detected for the first time in sewage water and a preliminary analysis gave average concentrations of 150 and 225 ng/L for norfluoxetine and fluoxetine, respectively. [source] Supported liquid membranes in hollow fiber liquid-phase microextraction (LPME) , Practical considerations in the three-phase modeJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2007Kari Folde Bårdstu Abstract In this work, three-phase liquid-phase microextraction (LPME) based on a supported liquid membrane (SLM) sustained in the wall of a hollow fiber was investigated with special focus on optimization of the experimental procedures in terms of recovery and repeatability. Recovery data for doxepin, amitriptyline, clomipramine, and mianserin were in the range of 67.8,79.8%. Within-day repeatability data for the four basic drugs were in the range of 4.1,7.7%. No single factor was found to be responsible for these variations, and the variability was caused by several factors related to the LPME extractions as well as to the final HPLC determination. Although the volume of the SLM varied within 0.4,3.1% RSD depending on the preparation procedure, and the volume of the acceptor solution varied within 4.8% RSD, both recoveries and repeatability were found to be relative insensitive to these variations. Thus, the handling of microliters of liquid in LPME was not a very critical factor, and the preparation of the SLM was accomplished in several different ways with comparable performance. Reuse of hollow fibers was found to suffer from matrix effects due to built-up of analytes in the SLM, whereas washing of the hollow fibers in acetone was beneficial in terms of recovery, especially for the extraction of the most hydrophobic substances. Several of the organic solvents used in the literature as SLM suffered from poor long-term stability, but silicone oil AR 20 (polyphenyl-methylsiloxane), 2-nitrophenyl octyl ether (NPOE), and dodecyl acetate (DDA) all extracted with unaltered performance even after 60 days of storage at room temperature. [source] Simultaneous extraction and concentration of penicillin G by hollow fiber renewal liquid membraneBIOTECHNOLOGY PROGRESS, Issue 2 2009Zhongqi Ren Abstract In this article, hollow fiber renewal liquid membrane (HFRLM) technique was used for recovery of penicillin G from aqueous solution. The organic solution of 7 vol % di-n-octylamine (DOA) + 30 vol % iso-octanol + kerosene was used as liquid membrane phase, and Na2CO3 aqueous solution was used as stripping phase. Experiments were performed as a function of carrier concentration in the organic phase, organic/aqueous volume ratio, pH, and initial penicillin G concentration in the feed phase, pH in the stripping phase, flow rates, etc. The results showed that the HFRLM process was stable and could carry out simultaneous extraction and concentration of penicillin G from aqueous solutions. As a carrier facilitated transport process, the addition of DOA in organic phase could greatly enhance the mass transfer rate; and there was a favorable organic/aqueous volume ratio of 1:20 to 1:30 for this system. The mass transfer flux and overall mass transfer coefficient increased with decreasing pH in the feed phase and increasing pH in the stripping phase, because of variation of the mass transfer driving force caused by pH gradient and distribution equilibrium. The flow rate of the shell side had significant influence on the mass transfer performance, whereas the effect of flow rate of lumen side on the mass transfer performance was slight because of the mass transfer intensification of renewal effect in the lumen side. The results indicated that the HFRLM process was a promising method for the recovery of penicillin G from aqueous solutions. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Assembly synthesis of sheet-like calcite array and stable-vaterite by supported liquid membraneCHINESE JOURNAL OF CHEMISTRY, Issue 10 2004Dong-Mei Sun Abstract Sheet-like calcite array and stable vaterite were synthesized by bio-mimetic supported liquid membrane system under different reaction conditions. Both of the FTIR spectra of products showed narrower peak at 1418 cm,1 than that of bulk CaCO3, and that of vaterite has a split in this peak. [source] Electric field-enhanced transport across phase boundaries and membranes and its potential use in sample pretreatment for bioanalysisELECTROPHORESIS, Issue 5 2010Pavel Kubá Abstract Separation techniques, such as electrodialysis, electroextraction, electro-membrane extraction and extraction across phase interfaces, are reviewed and discussed as methods for sample cleanup and preconcentration. This survey clearly shows that electromigration of ionic species across phase interfaces, especially across supported liquid membranes, may be very selective and is strongly dependent on the chemical composition of these interfaces. Thus, electric field-enhanced transport across chemically tailored liquid membranes may open new perspectives in preparative analytical chemistry. This review offers comprehensive survey of related literature and discussion of the topic, which may stimulate interest of experts and practitioners in bioanalysis. [source] Quantitative Removal of Mercury(II) from Water Through Bulk Liquid Membranes by Lipophilic PolyaminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2006Nicoletta Spreti Abstract Transport of mercury(II) and copper(II) ions through bulk liquid membranes has been studied, the former because of its toxicity and wide distribution in the environment, the latter for comparative purposes. The abilities of two carriers, the known N,N, -bis[2-(hexadecylamino)ethyl]- N,N, -bis(hydroxyethyl)ethylenediamine (bis-HE16ED) and the new N,N,-bis(p -octyloxybenzyl)-3,6-dioxaoctane-1,8-diamine (bis- pODODA), to complex and transport the selected metal ions are reported. Bis-HE16ED is a good carrier for Cu2+ ions, but the high stability of the carrier/Hg2+ ion complex in the membrane results in a lack of its transport. On the other hand, the new carrier displays a very high efficiency in Hg2+ ion transport, effecting quantitative transfer of the metal ion into the receiving phase within 24 h, despite its chelating region being only slightly different from that in bis-HE16ED. The ability of bis- pODODA to transport 100,% of Hg2+ efficiently in consecutive cycles is also reported. This result provides a basis for future development of a decontamination process based on a carrier-mediated transport system. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A New Carrier for Selective Removal of Heavy Metal Ions from Aqueous Solutions through Bulk Liquid MembranesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2004Nicoletta Spreti Abstract The carrier-mediated transport of heavy metal ions through bulk liquid membranes has been examined: toxic Hg2+, Cd2+ and Pb2+ ions were studied, along with Cu2+ ions for comparative purposes. The ability of a new carrier, 2,2,-bis(p -octyloxybenzyl)diethylenetriamine (bis- pODET), to complex and transport all the selected metal ions is reported. Differing affinities of the carrier for the different metal ions and the different experimental conditions required for their release into the receiving phase allowed the selective separation of equimolar binary mixtures. For Hg2+/Cd2+ and Hg2+/Pb2+ mixtures, two different separation methods were performed, while the inefficacy of the separation of Cd2+/Pb2+ and Hg2+/Cu2+ mixtures was for two different reasons: (i) the carrier is able to extract the metal ions with similar levels of ability, and (ii) the carrier metal ion complexes require the same acidity of the receiving phase to release the metal ions. The capability of the carrier to transport Hg2+ efficiently in consecutive cycles is also reported: over 90% of the metal ions were transferred into the receiving phase for three consecutive processes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Liquid membrane technology: fundamentals and review of its applicationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2010M. F. San Román Abstract OVERVIEW: During the past two decades, liquid membrane technology has grown into an accepted unit operation for a wide variety of separations. The increase in the use of this technology owing to strict environmental regulations and legislation together with the wider acceptance of this technology in preference to conventional separation processes has led to a spectacular advance in membrane development, module configurations, applications, etc. IMPACT: Liquid membrane technology makes it possible to attain high selectivity as well as efficient use of energy and material relative to many other separation systems. However, in spite of the known advantages of liquid membranes, there are very few examples of industrial applications because of the problems associated with the stability of the liquid membrane. APPLICATIONS: Liquid membrane technology has found applications in the fields of chemical and pharmaceutical technology, biotechnology, food processing and environmental engineering. On the other hand, its use in other fields, such as in the case of hydrogen separation, the recovery of aroma compounds from fruits, the application of ionic liquids in the membrane formulation, etc., is increasing rapidly. Copyright © 2009 Society of Chemical Industry [source] An overview of the mathematical modelling of liquid membrane separation processes in hollow fibre contactorsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2009E Bringas Abstract Liquid membranes have traditionally been employed for liquid/liquid mass transfer and have found applications in industrial, biomedical and analytical fields as well as in hydrometallurgical processes, wastewater treatment and remediation of polluted groundwater. However, in spite of the known advantages of liquid membranes, there are few examples of industrial application. The development of reliable mathematical models and design parameters (mass transport coefficients and equilibrium or kinetic parameters associated with the interfacial reactions) is a necessary step for design, cost estimation, process optimisation and scale-up. This work reports an overview of the different approaches that have been proposed in the literature to the mathematical modelling of liquid membrane separation processes in hollow fibre contactors providing, at the same time, a useful guideline to characterise the mass transport phenomena and a tool for the optimal design and intensification of separation processes. Copyright © 2009 Society of Chemical Industry [source] Cobalt removal from waste-water by means of supported liquid membranesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2009Kim Verbeken Abstract BACKGROUND: Supported liquid membranes (SLM) are an alternative technique to remove and recover metals from diluted process solutions and waste-water. In the present work, the removal of Co(II) from a synthetic CoSO4 solution containing initial amounts of cobalt(II) in the range 100,200 ppm (0.1,0.2 g dm,3) has been studied on a pilot scale. By performing batch equilibrium experiments, the optimal settings, i.e. the composition of the organic phase, the pH of the feed, the type and concentration of the stripping agent were determined. RESULTS: It is shown that the equilibrium characteristics of a synergistic extractant mixture containing di-2-ethyl-hexylphosphoric acid (D2EHPA) and 5-dodecylsalicylaldoxime (LIX 860-I) are superior to D2EHPA. Both hydrochloric acid and sulfuric acid have been evaluated as stripping solutions in liquid,liquid extraction tests and as the receiving phase in a SLM configuration. Although equilibrium tests showed no difference in stripping characteristics between both chemicals, it was observed that in a SLM configuration the stability of the system when hydrochloric acid is used is poor. With a commercially available SLM module (Liqui-Cel Extra-Flow 4 × 28) having a surface area of 19 m2, a steady Co(II) flux of 0.140 gm,2h,1 has been obtained at influent concentrations of cobalt between 100 and 200 ppm with 3 mol dm,3 sulfuric acid as stripping phase. CONCLUSIONS: The results obtained show that a supported liquid membrane containing a synergistic mixture of LIX 860-I and D2EHPA gives the possibility of recovering cobalt from dilute solutions. Copyright © 2008 Society of Chemical Industry [source] Potential of combining of liquid membranes and molecularly imprinted polymers in extraction of 17,-estradiol from aqueous samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 11 2009Olga Nemulenzi Abstract The potential of combination of liquid membranes (microporous membrane liquid,liquid extraction) and molecularly imprinted polymers (MIPs) was performed using 17,-estradiol (E2) as model compound. The model compound was extracted from aqueous sample through a hydrophobic porous membrane that was impregnated with hexane/ethyl acetate (3:2), which also formed part of the acceptor phase. In the acceptor phase, the compound was bound onto MIP particles that were also part of the organic phase. The potential of such combination was optimised for the type and amount of MIP particles in the organic acceptor phase, the extraction time, and the type of organic acceptor solvent. Ultrasound assisted binding of E2 onto MIP particles was also investigated. MIPs prepared by precipitation polymerization were found to be superior to those prepared by bulk polymerization. Increase in the extraction time and the amount of MIP particles in the acceptor phase led to more E2 binding onto the MIP particles. Hexane/ethyl acetate (3:2) as an organic acceptor was found to give higher E2 binding onto MIP particles compared to toluene, diethyl ether, and hexane. Ultrasound was furthermore found to increase the binding of E2 onto MIP particles. The selectivity of the technique was demonstrated by extracting wastewater and where clean chromatograms were obtained compared to liquid membrane extractions (SLMs) alone. [source] Supported liquid membranes in hollow fiber liquid-phase microextraction (LPME) , Practical considerations in the three-phase modeJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2007Kari Folde Bårdstu Abstract In this work, three-phase liquid-phase microextraction (LPME) based on a supported liquid membrane (SLM) sustained in the wall of a hollow fiber was investigated with special focus on optimization of the experimental procedures in terms of recovery and repeatability. Recovery data for doxepin, amitriptyline, clomipramine, and mianserin were in the range of 67.8,79.8%. Within-day repeatability data for the four basic drugs were in the range of 4.1,7.7%. No single factor was found to be responsible for these variations, and the variability was caused by several factors related to the LPME extractions as well as to the final HPLC determination. Although the volume of the SLM varied within 0.4,3.1% RSD depending on the preparation procedure, and the volume of the acceptor solution varied within 4.8% RSD, both recoveries and repeatability were found to be relative insensitive to these variations. Thus, the handling of microliters of liquid in LPME was not a very critical factor, and the preparation of the SLM was accomplished in several different ways with comparable performance. Reuse of hollow fibers was found to suffer from matrix effects due to built-up of analytes in the SLM, whereas washing of the hollow fibers in acetone was beneficial in terms of recovery, especially for the extraction of the most hydrophobic substances. Several of the organic solvents used in the literature as SLM suffered from poor long-term stability, but silicone oil AR 20 (polyphenyl-methylsiloxane), 2-nitrophenyl octyl ether (NPOE), and dodecyl acetate (DDA) all extracted with unaltered performance even after 60 days of storage at room temperature. [source] Regimes of Multiple Emulsions of W1/O/W2 and O1/W/O2 Type in the Continuous Couette-Taylor Flow ContactorCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2010E. Dluska Abstract The flow regimes of multiple emulsions in the continuous Couette-Taylor flow (CTF) contactor and characterization of the dispersion state are reported. The proposed method of multiple emulsion preparation is a one-step procedure on the contrary to the classical two-step procedure. The effect of operating parameters in the CTF contactor on multiple emulsion appearance, structure (drop size and packing), and rheological behavior is discussed. The key factors affecting multiple emulsion preparation in the CTF apparatus were the phases ratio, the rotational flow, and an annular gap width. The influence of an axial flow was more significant in the range of small rotational rates. The operating conditions were optimized to find the best characteristic multiple emulsions (largest interfacial area). The paper presents the same exemplary data of using W1/O/W2 emulsions as emulsion liquid membranes (ELMs) in the extraction process and O1/W/O2 for control active agent (drug) release. [source] | |||||||||||||