Emulsion liquid membrane process

Mahdi C, Oualid H, Fatiha A, Christian P (2010) Study on ultrasonically assisted emulsification and recovery of copper(II) from wastewater using an emulsion liquid membrane process. Ultrason Sonochem 17(2) 318-325... 

A form of liquid membrane that received a great deal of attention in the 1970s and 1980s was the bubble or emulsion membrane, first developed by Li at Exxon [11-13], Figure 11.14 is a schematic illustration of an emulsion liquid membrane process, which comprises four main operations. First, fresh product solution is emulsified in the liquid organic membrane phase. This water/oil emulsion then enters a large mixer vessel, where it is again emulsified to form a water/oil/water emulsion. Metal ions in the feed solution permeate by coupled... 

Emulsion liquid membrane process can be divided into three stages 1. emulsification, 2. permeation and settling, and... 

Lee SC and Lee WK. Extraction of penicillin G from simulated media by an emulsion liquid membrane process. J Chem Tech Biotechnol 1992 55 251-261. 

Park, Y., SkeUand, A.H.P., Forney, L.J. and Kim, J.H. (2006). Removal of phenol and substituted phenols by newly developed emulsion liquid membrane process. Water Res., 40, 1763-72. 

Bayraktar, E. (2001). Response surface optimization of the separation of dl-tryptophan using an emulsion liquid membrane. Process Biochem., 37, 169-75. 

An emulsion liquid membrane process is reported in Chapter 24 by Gleason et al which rapidly reduces aqueous phase selenium concentrations to low levels within 15 minutes of contact time, while enhancing the concentration of selenium in the internal phase by more than a factor of 40. The emulsion formulation is very stable, and swelling does not significantly dilute the selenium in the internal phase. The presence of other anionic species, such as sulfate, is not a significant interference for removal of the selenium anions. 

The preparation and splitting of emulsions are the key parameters in an emulsion liquid membrane process. A very stable emulsion which avoids any loss of emulsified droplets is a prior condition for the feasibility of the process. However, the more stable the emulsion, the more difficult to split it. So both steps are dependent on each other and have to be optimized, also with regard to cost optimization. In the present work, we try to calculate the flow pattern in the two steps using CFD (computational fluid dynamics) software in order to improve the design of the two steps. 

The mass transfer of an emulsion liquid membrane process has been modeled mathematically. An analytical solution which allows prediction of concentrations of solutes in the external phase, membrane phase, and external phase-membrane interface was obtained. Experimentally, arsenic was selected as a solute in the external phase to be removed by the ELM process. Our model gives an excellent representation of the experimental data for the external concentration of the arsenic versus time. In addition, the model predicts the concentration distribution in the membrane phase at any time. Thus, the overall distribution of solutes in three phases (external, membrane and internal) at ahy time of the ELM process can be evaluated. From the model, it was found that the ELM process was characterize by two dimensionless groups. One group for the transport phenomena governs the rate of mass transfer or the Biot number. The other group includes the... 

The use of di-(p-alkylphenyl)phosphoric acids containing butyl, hexyl, octyl and nonyl alkyl groups as carriers for separations of Co(II), Cu(II), Ni(II), and Zn(II) from aqueous sulfate solutions by bulk and emulsion liquid membrane processes has been explored. The organic phase was the di-(p-alkylphenyl)phosphoric acid in kerosene widi the inclusion of Span 80 as an emulsifier for the emulsion liquid membrane systems. Both single metal ion species and competitive transport of the transition metal cations were investigated. For comparison, the transport of these metal cations by commercially available Cyanex 272 and D2EHPA as carriers was studied also. To probe the mechanism of the liquid membrane transport processes, interfacial tension measurements were conducted. Multistage emulsion liquid membrane processes for the separation of the transition metal cation mixtures have been evaluated. 

Separation of Transition Metal Cations by Multistage Emulsion Liquid Membrane Processes. In a final series of experiments, multistage emulsion liquid membrane processes were studied. Flow sheets for these process are shown in Figure 5. In the first process (Figure 5a), Cyanex 272 (2) was utilized as the carrier for separation of Co(II), Cu(II), Ni(II), and Zn(II) by competitive transport in four steps. The receiving phases from the four consecutive steps were enriched in Cu(II), Zn(II), Co(II), and Co(II), respectively. The effluent after the fourth step contained only... 

An survey of recent developments in membrane processes, involving reverse osmosis (RO), ultrafiltration (UF), microfiltration (MF), electrodialysis (ED), dialysis (D), pervaporation (Pr), gas permeation (GP), and emulsion liquid membrane (ELM), has been provided by Sirkar (1997). 

Figure 15.3 illustrates schematically the different stages of a continuous separation process using the emulsion liquid membrane. There are four main stages in the flow sheet (1) emulsification of the stripping phase... 

In this paper an overview of the developments in liquid membrane extraction of cephalosporin antibiotics has been presented. The principle of reactive extraction via the so-called liquid-liquid ion exchange extraction mechanism can be exploited to develop liquid membrane processes for extraction of cephalosporin antibiotics. The mathematical models that have been used to simulate experimental data have been discussed. Emulsion liquid membrane and supported liquid membrane could provide high extraction flux for cephalosporins, but stability problems need to be fully resolved for process application. Non-dispersive extraction in hollow fib er membrane is likely to offer an attractive alternative in this respect. The applicability of the liquid membrane process has been discussed from process engineering and design considerations. 

Demulsification with electrostatic fields appears to be the most effective and economic way for breaking of W/0 emulsion in ELM processes 190, 91]. Electrostatic coalescence is a technique widely used to separate dispersed aqueous droplets from nonconducting oils. Since this type of technique is strictly a physical process, it is most suitable for breaking emulsion liquid membranes to recover the oil membrane phase for reuse. 

Partitioning of components between two immiscible or partially miscible phases is the basis of classical solvent extraction widely used in numerous separations of industrial interest. Extraction is mostly realized in systems with dispergation of one phase into the second phase. Dispergation could be one origin of problems in many systems of interest, like entrainment of organic solvent into aqueous raffinate, formation of stable, difficult-to-separate emulsions, and so on. To solve these problems new ways of contacting of liquids have been developed. An idea to perform separations in three-phase systems with a liquid membrane is relatively new. The first papers on supported liquid membranes (SLM) appeared in 1967 [1, 2] and the first patent on emulsion liquid membrane was issued in 1968 [3], If two miscible fluids are separated by a liquid, which is immiscible with them, but enables a mass transport between the fluids, a liquid membrane (LM) is formed. A liquid membrane enables transport of components between two fluids at different rates and in this way to perform separation. When all three phases are liquid this process is called pertraction (PT). In most processes with liquids membrane contact of phases is realized without dispergation of phases. 

Pertraction (PT) can be realized through a liquid membrane, but also through a nonporous polymeric membrane that was applied also industrially [10-12]. Apart from various types of SLM and BLM emulsion liquid membranes (ELM) were also widely studied just at the beginning of liquid membrane research. For example, an emulsion of stripping solution in organic phase, stabilized by surfactant, is dispersed in the aqueous feed. The continuous phase of emulsion forms ELM. Emulsion and feed are usually contacted in mixed column or mixer-settlers as in extraction. EML were applied industrially in zinc recovery from waste solution and in several pilot-plant trials [13,14], but the complexity of the process reduced interest in this system. More information on ELM and related processes can be found in refs. [8, 13-16]. 

Draxler, J. and Marr, R. (1986) Emulsion liquid membranes part I Phenomenon and industrial application. Chemical Engineering and Processing, 20, 319. 

Solvent extraction of penicillin from fermentation broths has been well documented in the literature. Penicillin G and penicillin V can be efficiently extracted with amyl acetate or butyl acetate at pH 2.5-3.0 and at 0° to 3°C.33 Schiigerl1 systematically reviewed solvent extraction of different forms of penicillin from fermentation broths. Figure 1 shows an integrated process for the extraction of penicillin G from clarified broth of Penicillium chryso-genurn fermentation.1 Penicillin G is converted to 6-amino penicillanic acid and phenylacetic acid at pH 8 in a 10 L Kiihni extractor by penicillin G-amidase immobilized in an emulsion liquid membrane. The 6-amino penicillanic acid is subsequently converted to ampicillin at pH 6 and the enzyme is recycled. 

Ultrasound-assisted emulsification in aqueous samples is the basis for the so-called liquid membrane process (LMP). This has been used mostly for the concentration and separation of metallic elements or other species such as weak acids and bases, hydrocarbons, gas mixtures and biologically important compounds such as amino acids [61-64]. LMP has aroused much interest as an alternative to conventional LLE. An LMP involves the previous preparation of the emulsion and its addition to the aqueous liquid sample. In this way, the continuous phase acts as a membrane between both the aqueous phases viz. those constituting the droplets and the sample). The separation principle is the diffusion of the target analytes from the sample to the droplets of the dispersed phase through the continuous phase. In comparison to conventional LLE, the emulsion-based method always affords easier, faster extraction and separation of the extract — which is sometimes mandatory in order to remove interferences from the organic solvents prior to detection. The formation and destruction of o/w or w/o emulsions by sonication have proved an effective method for extracting target species. 

Emulsion liquid membranes can be effectively demulsified by high shear. A variation on this is to employ centrifugation as a first step, followed by processing in a high shear device [46]. 

Hirato T, Kishigami I, Awakura Y, and Majima H. Concentration of uranyl sulfate solution by an emulsion-type liquid membrane process. Hydrometallurgy 1991 26 19-33. 

Kitagawa, T. Nishikawa, Y. Frankenfeld, J. W. Li, N. N. "Wastewater Treatment by Liquid Membrane Process" Environ. Sci. Tech. 1977,11, pp 602-605. Thien, M. P. Hatton, T. A. Wang, D. I. C. "Liquid Emulsion Membranes and Their Applications in Biochemical Separations" In Separation, Recovery, and Purification in Biotechnology ACS Symposium Series 314, 1986, pp 67-77. 

Liquid membrane (LM) separation provides a potentially powerful technique for effecting diverse separation operations. Compared to conventional processes, emulsion liquid membrane (ELM) and liquid surfactant membrane (LSM) processes have some attractive features, for example, simple operation, high efficiency, extraction and stripping in one stage, larger interfacial area, scope of continuous operation. The ELM technique has great potential for recovery and removal of different metal ions and hydrocarbons from wastewater where conventional methods provide lower separation efficiency. 

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