Liquid Membrane Technology Research Articles

Recovery of nickel ions by supported liquid membrane (SLM) extraction

Heavy metal ions very often appear in high concentrations in all kind of effluents giving rise to hazards of pollution because of their high toxicities and wide environmental spreading. This paper deals with the recovery of nickel ions from effluents resulting from the metal finishing industry. In the first stage, commercial extractants were screened by means of conventional extractions. Combining organophosphoric or organophosphinic acids with oximes lead to enhanced Ni(II) extraction. The influence of the type of extractant was investigated as well as other critical parameters such as concentration and pH of the feed. In the second stage, the most promising combinations were tested with the supported liquid membrane (SLM) technology in a lab-scale environment. Those experiments can be divided into two classes when the membrane type is considered: experimental work with flat sheet membranes (Celgard 2400: 0.0062 m 2) and with hollow fiber modules (Celgard: 0.4–1.7 m 2). A mixture of LIX 860-I and Cyanex 302 was most successful for the selected operation characteristics, especially for the plating industry. Permeations were calculated for various concentrations of extractant and experimental runs were undertaken with real effluents. At the end, an ageing test was started to check the stability of the membrane and the evolution of the flux in function of time.

Recovery of cadmium from a zinc hydrometallurgical leachate using reactive emulsion liquid membrane technology

AbstractA new emulsion liquid membrane process using 3,5‐diisopropylsalicylic acid (DIPSA) and triisobutylphosphine sulfide (TIBPS) as carriers, and ammonium sulfide (NH4)2S as precipitant is described. The reactive nature of sulfide ions with extracted cadmium ions in the internal aqueous phase significantly increases cadmium recovery and minimizes zinc impurities. The new process is applied to the enrichment of a low concentration of cadmium ions from a solution containing a high concentration of zinc ions. Under optimum operating conditions, a single stage process produced a cadmium recovery of 98% at a cadmium sulfide content of 99.6%. The results are encouraging for potential applications in zinc hydrometallurgy for recovery of cadmium from sulfuric acid leaching solution of zinc ores. Copyright © 2004 Society of Chemical Industry

Batch extraction of gold(III) ions from aqueous solutions using emulsion liquid membrane via facilitated carrier transport

Experimental results for the batch extraction of gold(III) ions using an emulsion liquid membrane (ELM) with an internal alkaline aqueous sodium sulfite are presented. Experiments were performed using LK-80 as the biodegradable emulsifier for the first time in emulsion liquid membrane technology. The effects of various parameters, such as Au(III) concentration in the aqueous phase, concentration of carrier in the membrane phase, concentration of sodium sulfite in the internal stripping phase, pH of the external aqueous phase and the speed of agitation on the extraction rate were studied. Results showed that nearly all of the Au(III) ions in the aqueous phase were extracted in few minutes. By proper selection of the extraction conditions, almost all of the gold ions present in a concentrated feed solution were extracted within less than 25 min. A Taguchi analysis has been performed on the experimental results which determined the effects and contribution of each of the parameter on the extraction efficiency and interaction between the parameters.

Biomimetic Synthesis of Ag2CrO4 Quasi-Nanorods and Nanowires by Emulsion Liquid Membranes

Semiconductor Ag2CrO4 quasi-nanorods and nanowires have been successfully prepared through novel emulsion–liquid membrane technology. The membrane phase in this system consists of Span-80 as the surfactant, N7301 as the carrier (or free carrier), and kerosene as the solvent. The internal aqueous phase is 0.1 M AgNO3 and the external aqueous phase is 0.1 M K2Cr2O7. Under the conditions of Roi = 2.0, Rew = 0.5, [Span-80] = 6% (v/v), and room temperature, Ag2CrO4 quasi-nanorods with diameters of 180–300 nm and lengths of up to 2300 nm, or nanowires with diameters of 15–25 nm and lengths of up to 1000 nm, were obtained in the presence or absence of 5% (v/v) N7301, respectively. X-Ray diffraction and transmission electron microscopy were used to characterize the structure and morphology of the Ag2CrO4 quasi-nanorods and nanowires. In addition, the photoluminescence spectrum showed strong emissions.

Extraction and separation of nickel and cobalt by electrostatic pseudo liquid membrane

The extraction and separation of nickel and cobalt using electrostatic pseudo liquid membrane technology is the subject of this article. An electrostatic pseudo liquid membrane reactor was constructed and extraction tests were undertaken to determine the effects of various experimental variables on the extraction and separation of nickel and cobalt. At optimum conditions, devised as a result of this investigation, a nickel/cobalt ratio of 1000 in the raffinate from a synthetic feed solution containing 10 000 ppm nickel and 1000 ppm cobalt was achieved. Separation of nickel and cobalt from a pregnant leach solution was achieved in two stages.

Theoretical and Analytical Characterization of a Flow-Through Permeation Liquid Membrane with Controlled Flux for Metal Speciation Measurements

Speciation measurements with the permeation liquid membrane (PLM) technology require necessarily a good control of the flux of the analyte. In this perspective, a PLM-based multichannel flow-through cell has been designed. The first objective of this study has been to adapt the classical Levich model commonly used for electrochemical flow devices to the characteristic geometry of the PLM cell. In the latter case and contrary to the Levich model, the effects of the channel lateral walls on the flux of active species through the membrane have to be taken into account. The problem was solved by considering the existence of two parabolic Poiseuille profiles perpendicular to each other and developing along the fluid motion. The theoretical results obtained match satisfactorily with experimental data. The analytical study of this PLM system has been performed with copper(II) ions as test species and has shown that the preconcentration factor is (1) linear at least for preconcentration times of < or = 120 min, (2) reproducible on the same membrane as well as on different membranes, and (3) independent of the initial test metal ion concentration in the sample solution. The capabilities of this cell to determine metal speciation by considering lability of complexes and the flux of metal at variable flow rates of the test solution is also discussed by means of Cu(II)/sulfosalicylic complexes.

Liquid membranes and the treatment of metal-bearing wastewaters

Liquid membrane technologies are gaining a prominent role as a separation technique for the treatment of metal-contained liquid effluents. The present work describes the most important of technologies, the general mechanisms for the metal extraction and some of their applications in the separation of metals.

Heavy metals removal from wastewaters of phosphoric acid production: a comparison of hybrid liquid membrane (HLM) and aqueous hybrid liquid membrane (AHLM) technologies

Selective removal of heavy metal ions from industrial wet-process phosphoric acid (WPA) was studied, using the two liquid membrane systems: Hybrid Liquid Membrane (HLM) and Aqueous Hybrid Liquid Membrane (AHLM). Monothiophosphinic acid (Cyanex 302) in kerosene (for the HLM) and Polyvinylsulfonic acid (PVSA) aqueous solution (for the AHLM) were used as a liquid membrane (LM), separated from the feed and strip streams by neutral or cation-exchange membranes. On application of the HLM separation system, the permeation from the feed to the strip phase followed the selectivity sequence: Zn &amp;gt;&amp;gt; Cd &amp;gt; Cu with all types of membranes used. Results show that the selective separation of Cd and Zn from the WPA may be achieved by the HLM with cation-exchange membranes, using a single set-up installation at continuous processing. Copper is accumulated in the Cyanex 302, poisoning the carrier. So, this carrier and HCl as a strip solution can not be recommended for the HLM processing of WPA. Using the AHLM separation system, heavy metals such as cadmium and copper, were successfully recovered from the WPA: average fluxes (in mol/m2sec) to the strip phase were 3.7 × 10-7 and 6.7 × 10-7. Satisfactory dynamic selectivity to copper (≈16) was found. The transfer of iron and zinc species to the strip phase was below detection levels during the 144 hrs of the AHLM experiment. Contamination of the feed and strip solutions by PVSA was not observed during the 500 hrs of processing. The membranes were completely regenerable and used repeatedly. In comparison with the HLM and other liquid membrane systems, the AHLM can potentially provide many operational, economic and environmental advantages, some of them being higher transport rates, low carrier losses and low contamination of the feed and strip solutions by water-soluble polymers, long membrane lifetime, ambient temperature, low energy requirements and chemical consumption, no special requirements for membrane resistance in organic solvents, and fewer limitations on the variability of membrane pore sizes, etc.

New membrane technology for removal and recovery of chromium from waste waters

AbstractWe have developed new supported liquid membrane (SLM) technology for removal and recovery of chromium from waste waters. The technology not only removes the Cr (VI) to less than 0.05 ppm in the treated effluent allowable for discharge or recycle, but also recovers the product at a high concentration of about 20% (62.3% Na2CrO4) suitable for resale or reuse. In other words, we have achieved the goals of zero discharge and no sludge. The chromium flux in its entire range from low Cr (VI) concentrations in the feed solution to high feed concentrations, at which the carrier saturation of the facilitated transport mechanism occurs, has been in good agreement with a film model. The stability of the SLM has been ensured by strip dispersion, where the aqueous strip solution is dispersed in the organic membrane solution in a mixer. The strip dispersion formed is circulated from the mixer to the membrane module providing a constant supply of the organic solution to the membrane pores.

Developments in liquid membrane technology and membrane distillation

Euromembrane 2000 was held in Israel on 24–27 September 2000. In keeping with the conference's tradition, it brought together people working in different areas of membranology, and it covered both research & development and applications. Based entirely on abstracts of papers which were presented at the conference, this thematic round-up focuses on a number of the talks which dealt solely with developments in liquid membranes, their characteristics and properties, and membrane distillation.

Comparison of liquid membrane processes for the removal of cadmium from wet phosphoric acid

The viability of the cadmium removal from wet phosphoric acid by means of three liquid membrane processes (emulsion liquid membranes, supported liquid membranes and non-dispersive solvent extraction) has been demonstrated in previous works where the kinetics of cadmium removal were successfully studied [A.I. Alonso, A.M. Urtiaga, S. Zamacona, A. Irabien, I. Ortiz, J. Membr. Sci. 130 (1997) 193; J.A. Daoud, S.A. El-Reefy, H.F. Aly, Sep. Sci. Technol. 33 (1998) 537; T. Gallego, E.S. Pérez de Ortiz, Separation of cadmium from phosphoric acid containing Cu 2+ and Cd 2+ using surfactant liquid membranes, in: D.M. Maron, Begell (Ed.), Int. Symp. on Liquid–Liquid Two Phase Flow and Transport Phenomena, Antalya, Turkey, 3–7 November 1997, Begell House, New York, 1998, pp. 301–310]. This work has been focused on the comparison of the three liquid membrane technologies for the removal of Cd, working with cadmium initial concentrations in the range of 1.8 × 10 −4–4.45 × 10 −3 M and using Cyanex 302 as organic extractant in the concentration range 0.025–0.63 M. The comparison has been made in terms of the values of mass transfer flux. The mass transfer models and the corresponding mass transport parameters provided the system tools for the quantitative comparison. By simulation of the cadmium flux and of the evolution of the cadmium concentration with time it was concluded that the rate of Cd removal and the values of mass transfer flux under the studied conditions varied in the order NDSX > ELM > SLM.

Selective extraction of actinides by polyphosphine polyoxides through supported liquid membrane

Extraction of actinides like neptunium, plutonium and americium have been performed using polyphosphine polyoxides. Phosphorus compounds with (O)PCP(O) linkage exhibit very high liquid-liquid extraction properties. They demonstrate also quantitative and selective transport properties of some actinides by supported liquid membrane (SLM) technology.

Ion extraction using the electrostatic pseudo liquid membrane technique

Liquid membrane technology has developed rapidly since the 1940's. It has three main categories; liquid surfactant membranes (LSM); supported liquid membranes (SLM); electrostatic pseudo-liquid membranes (ESPLIM), a promising new technology. An ESPLIM system has been built and tested. It operates satisfactorily and performance data using Co and Na ions are presented.

Emulsion liquid membranes for chiral separations: Selective extraction ofrac-phenylalanine enantiomers

We describe the use of emulsion liquid membrane technology to perform chiral separations on low molecular weight species. We have reviewed liquid membrane technology in the context of existing process scale chiral separations. We illustrate the potential of this new technique by presenting our results on the selective extraction of phenylalanine enantiomers, using copper (II) N-decyl-(L)-hydroxyproline as a chiral selector in an emulsion liquid membrane configuration. This is compared with an analogous batch solvent extraction system. Initial batch enantiomeric excesses of greater than 40% were observed with the emulsion liquid membrane system compared with around 25% for the solvent extraction system. It was also noted that the system is not limited by the equilibrium capacity constraints of the solvent extraction system. We have shown that kinetic chiral liquid membrane technology offers high productivity and flexibility compared with analogous process scale chiral technologies. Recent transfer of highly specific chiral reversed-phase high-performance liquid chromatographic chemistries have shown that “one-stop” enantiomeric excesses of commercial interest (>95%) are achievable using kinetic chiral liquid membrane systems. Solvent and temperature selection strategies also have been outlined as means of increasing the enantioselectivity of existing liquid membrane extraction chemistries. Chirality 9:261–267, 1997. © 1997 Wiley-Liss, Inc.

Liquid membrane technology for the separation of racemic mixtures

Many drugs and pesticides are presently used as a racemic mixture. However, the biological activity is often concentrated in one of the two enantiomers, the other enantiomer being 50% impurity. A new process has been developed to separate enantiomeric mixtures, based on the combination of a countercurrent fractionation and liquid membrane technology. Two liquids are oppositely chiralized by the addition of the R- or the S-enantiomer of a chiral selector, respectively. These liquids are miscible and are kept separated by a non-miscible liquid contained in a porous membrane. The liquid membrane should be permeable to the enantiomers to be separated and non-permeable to the chiral selector molecules. Enantioselectivities have been determined for a broad variety of racemic drugs. Different types of hollow-fiber modules have been tested and optimization of the modules has mainly been focused on the improvement of shell-side flow distribution. To proof the feasibility of the system, experiments have been performed in a bench-scale unit, in which optical purities of 99% plus for both enantiomers have been obtained.

Synthesis of Diphosphine Dioxides for Extraction of Actinides using Supported Liquid Membranes Technology

A recurrent method for synthesis of linear and macrocyclic diphosphine dioxides has been applied to synthesize new phosphoryl ligands with P-C bonds, stable in strongly acidic aqueous solution and therefore useful for extraction and recovering of actinides from nuclear wastes. The influence of the structural parameters on their liquid-liquid extraction properties of plutonium and neptunium is studied. Plutonium and Neptunium can be removed from radioactive contaminated liquid wastes, using the supported liquid membrane technology with the more lipophilic organophosphorus extractants, which are a promising alternative to the CMPO (a carbamoylmethylphosphine), currently used for such extractions.

Kinetics of the extraction of phenylalanine and glutamic acid by ion-exchange carriers

Biological transport of amino acids is usually mediated by carrier proteins buried in biomembranes. The application of models to such transport systems has long been desired in the separation science and technology of amino acids and is an active area of research. Recently, the application of commercial metal extractants as mobile carriers in the liquid membrane technology has attracted increasing attention due to their potential capability in the field of bioseparation. In the development of such a novel separation technique, knowledge of the extraction kinetics is necessary in addition to knowledge of the extraction equilibrium. Due to their zwitterionic character, it is possible to extract amino acids with ion-exchange carriers by controlling the pH of aqueous amino acid solutions. A modified Lewis-type cell experiment was used to study the extraction kinetics of glutamic acid (system I) and phenylalanine (system II) by naphthenic acid, and that of phenylalanine by a quarternary ammonium salt, Aliquat 336 (system III). The effects of agitation, interfacial area, carrier concentration, pH, and initial concentration of amino acids on the extraction rate were discussed. A rate equation involving the mass transfer terms was derived, based on an interfacial chemical reaction mechanism. It was found that the limiting case, based on an interfacial reaction rate-determining mechanism, was in good agreement with the experimental results. The intrinsic chemical reaction is controlled by the formation of an amino acid/ carrier complex at the interface. The mechanism of extraction proposed in this study is applicable to both glutamic acid and phenylalanine in the two ionic carrier systems.

PHENOL RECOVERY WITH SLM USING “CYANEX 923”

Abstract The study of the phenol separation-concentration process with the hollow fiber supported liquid membrane technology has been performed. Mixtures of kerosene and CYANEX 923 were used as liquid membrane. The extractant CYANEX 923 is characterized by a high phenol selectivity and an extremely low solubility in the aqueous phase. The introduction of CYANEX 923 in the membrane composition decreases the extractant losses from the pores of the support. The phenol separation and simultaneous concentration process has been checked. The influences of the initial concentration of phenol in the feed solution and sodium hydroxide in the stripping phase and the membrane composition on the separation rate have been investigated in a single-pass mode. The analysis of the membrane composition influence has been performed according to the steady-state mass transfer conservation equation and the associated boundary conditions, leading to the mass transfer parameters of the process

Recovery of Nitrophenols from Aqueous Solutions by a Liquid Emulsion Membrane System

Abstract The application of liquid emulsion membrane technology to the extraction of nitrophenols from aqueous solutions is discussed. The effects of various parameters such as hydrophilic lipophilic balance of the surfactants, speed of agitation, water volume fraction in the water-in-oil emulsion, treatment ratio, and the concentration of surfactant on the extraction of p-nitrophenol are studied, and a suitable formulation for a liquid emulsion membrane is developed. The same formulation was used to extract o-nitrophenol and 2,4-dinitrophenol, and the results are compared with those of p-nitrophenol. The swelling of the emulsion during extraction is minimized by the addition of cyclohexanone to the membrane phase. The demulsification of the emulsion phase after extraction is also carried out by a chemical demulsification technique. Acetone is used for demulsification.

The investigation of osmosis in the liquid membrane technique. Influence of key parameters

Water transfer across a liquid membrane occurs during the process of the liquid membrane technique. This leads to swelling of the emulsion so that the solutes (for example, phenol and metal ions) are diluted, rendering the recycling of those substances more difficult. Osmosis can be described as a function of many parameters. For prognosis it is important to propound a mathematical model for the transport of water across a liquid membrane. Experimental results show that the main influencing parameters are concentration of interfacial active agents, pH, temperature and difference in ionic strength of the feed and the receiving phase. A proposal for modelling osmosis in liquid membrane technology is given.