Liquid membrane multiple emulsion process of separation of copper(II) from waste waters
15 Jun 2000-Colloids and Surfaces A: Physicochemical and Engineering Aspects (Elsevier)-Vol. 166, Iss: 43468, pp 7-25
TL;DR: In this article, a liquid membrane (multiple emulsion, water-inoil-in-water, W III /O II /W I ) method of separation of copper(II) from simulated waste water has been described.
Abstract: A liquid membrane (multiple emulsion, water-in-oil-in-water, W III /O II /W I ) method of separation of copper(II) from simulated waste water has been described. The effect of variation of oil membrane constituents in O II , different concentrations of sulphuric acid as strippant in the internal phase W I , pH and the object ion concentration in the raffinate W III have been studied in detail with an aim to optimize the process so that the copper(II) content in the waste water be made lower than the toxic limit (1.5 ppm, WHO.) The ion-exchange behaviour of the carriers in the membrane and the coupled counter-transport resembling a ‘Chemical pump’ have been ascertained. Interference, in the process, of some metals (ions) occurring naturally with copper, e.g. Pb(II), Cd(II), Zn(II), Co(II), Ni(II) and Mn(II) through their co-transport have been studied. The relative extents of their accompaniment have been explained from the consideration of the stability of the carrier-metal (ion) complexes and exchange reactions at the interfaces. The application of the reaction site model and involvement of a pseudo first order process have been found to be reasonably justified in the present transport method of separation of copper(II).
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TL;DR: The structure of multiple emulsion systems is in this case defined as the number of bubbles contained in each size "level" of larger bubbles.
Abstract: Multiple emulsions, in which dispersed drops contain smaller drops inside, are useful in a large number of commercial applications, including chemical synthesis and drug delivery. For many of these applications, it is critical to have control over the size and structure of multiple emulsion systems. The structure of multiple emulsion systems is in this case defined as the number of bubbles contained in each size "level" of larger bubbles.
735 citations
TL;DR: In this paper, various emulsification methods, such as mechanical agitation and ultrasound emulsion, as well as the emulsion formulation which includes composition, selection of agent, and operation parameters on emulsion stabilization were presented.
Abstract: Extraction processes using emulsion liquid membrane (ELM) have received significant attention due to their potential as an effective technique for treatment of industrial liquid wastes. However, the need to obtain desired level of stability is very important in order to overcome the obstacle of the application of ELM at industrial scale. The small droplet diameter of emulsion is a key criterion that will provide a stable emulsion and a larger mass transfer area. Two important factors related to the stability of emulsion such as method of emulsification and mechanism of emulsion breaking is discussed in detail. Various emulsification methods such as mechanical agitation and ultrasound emulsification, as well as the emulsion formulation which includes composition, selection of agent, and operation parameters on emulsion stabilization were presented. Emulsion destabilization in term of emulsion breakdown mechanisms such as coalescence, swelling and leakage was also discussed.
201 citations
TL;DR: An extensive study on removal of lead (II) from aqueous solution using an emulsion liquid membrane (ELM) technique is presented in this article, where the authors highlighted the importance of emulsion stability for maximizing the lead removal.
Abstract: An extensive study on removal of lead (II) from aqueous solution using an emulsion liquid membrane (ELM) technique is presented. The study has highlighted the importance of emulsion stability for maximizing the removal of lead (II). The ELM consists of di-(2-ethylhexyl) phosphoric acid as a carrier, commercial kerosene as organic solvent, span 80 as an emulsifying agent and sulphuric acid as stripping phase. The important factors studied which affect the ELM stability and removal of lead are emulsification time (5–30 min), emulsification speed (1000–3000 rpm); the concentrations of surfactant (2–12 % v/v), carrier (1–12 % v/v), internal phase (0.25–3 molar H2SO4) and the effect of volume ratio of the oil phase to the stripping aqueous phase (O/A) (0.3–3.5). The results showed that it is possible to remove 99–99.5% of lead after 5 min contact time by using ELM at the optimum operating conditions.
138 citations
TL;DR: In this article, an emulsified liquid membrane (ELM) was used to extract valuable or toxic metals from dilute mine solutions using an extractor based on emulsifying liquid membranes.
Abstract: This is a communication on the removal of copper(II) ions from a residual mine water using an emulsified liquid membrane (ELM). The membrane was prepared by dissolving the extractant LIX-860 (a salicylaldoxime), used as a mobile carrier, and Span-80, a surfactant, in kerosene. The ELM allowed an efficient metal transport from the feed solution towards the strip liquor, in experiments carried out in a batch-type stirred tank at 30 °C. A screening factor-type experimental statistical design was developed, which established the variables and their interrelation affecting the studied process. The experimental results and the variance analysis indicated that the statistically significant variables on copper transport through the membrane were the extractant concentration, the stirring time and the stirring speed of the double emulsion. The surfactant concentration range employed in this study adequately stabilized the membrane. However, it did not produce any positive effect on metal extraction. It was observed that the use of an excessively high content of surfactant produced lower metal transport extraction since it gave rise to a higher interfacial resistance. The experimental results reported show the potential for removal of valuable or toxic metals from dilute mine solutions using an extractor based on emulsified liquid membranes.
130 citations
Cites methods from "Liquid membrane multiple emulsion p..."
...They are double water-in-oilin-water emulsions (W/O/W) stabilized by the employment of suitable surfactant substances, as shownbyKakoi et al. (1996), Chakraborty and Datta (1996) and Chakravarti et al. (2000), among others....
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01 Jan 2010
TL;DR: In this article, the authors provide comprehensive knowledge-based information by critical analysis, classification, model description, and applications of a variety of emulsion liquid membrane (ELM) separation processes.
Abstract: Publisher Summary The objective of this chapter is to provide comprehensive knowledge-based information by critical analysis, classification, model description, and applications of a variety of emulsion liquid membrane (ELM) separation processes. It also discusses new perspectives and directions of development in these fields. Liquid membrane separations have been extensively examined for potential application in many fields such as metal recovery, gas separation, organic compound removal, pollutant removal, and bioseparations. The difficulties in the application of these processes did not consist in sophisticated equipment or installation but in the adequate choice of reagent to allow the selective extraction of solute in required quantity. The widespread use of the ELM process has been limited due to the instability of emulsion globules against fluid shear. Numerous studies have attempted to enhance the stability of ELMs. Examples include adding more surfactants into the membrane phase and increasing the membrane viscosity. However, in most reported attempts increased stability has been unfortunately accompanied by loss in extraction efficiency and rate. A unique contacting device, a Taylor-Couette column, provides a relatively low and uniform fluid shear that helps maintain the stability of emulsion without compromising the extraction efficiency of a target compound. Current research has also been directed to minimizing membrane leakage or rupture through the use of bifunctional surfactants, which act as both emulsifier and extractant, and on additives (e.g., polymer) to impact elasticity of membrane.
83 citations
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TL;DR: In this paper, a new process for separating and concentrating metals is described, based on the principle of coupled transport, which is carried out within a microporous merebrane containing within its pores an organic, water-immiscible complexing agent, acting as a shuttle, picking up metal ions on one side of the membrane, carrying them across the membrane as a complex, and preserving electrical neutrality by carrying hydrogen ions in the opposite direction.
Abstract: A new process for separating and concentrating metals is described. It is based on the principle of coupled transport. Metal ions such as copper can be “chemically pumped” across a membrane against large concentration gradients by allowing the counterfiow of a coupled ion such as hydrogen ion. The process is carried out within a microporous merebrane containing within its pores an organic, water-immiscible complexing agent. The complexing agent acts as a shuttle, picking up metal ions on one side of the membrane, carrying them across the membrane as a complex, and preserving electrical neutrality by carrying hydrogen ions in the opposite direction. Because the flows of metal and hydrogen ions are coupled, the metal ion can be “chemically pumped” from a dilute into a concentrated solution. The energy for the process derives from the flow of hydrogen ions in the opposite direction. The process could find application, for example, in the purification of dump leach liquors in the hydrometallurgical processing of low grade ores Coupled transport of cupric ion was demonstrated with a Celgard 2400/LIX 64N membrane. Under favorable conditions, copper was concentrated against a 4000-fold concentration difference, and copper was separated from iron with a separation factor greater than 1000. A pH difference of one to two units is sufficient to drive the copper through the membrane at a high rate and separate it from iron. For a given pH gradient across the membrane, the flow of metal ion initially varies linearly with the metal ion concentration gradient, but at high metal ion gradients the flow reaches a limiting value. This appears to be the result of the limited solubility of the metal complex in the organic phase. Typical transport rates are on the order of 3 μg/cm2-min or 3 lb/ft2-year. A short economic assessment based on this flux indicates that processing with coupled transport membranes should be competitive with the best current technology
151 citations
TL;DR: The literature pertaining to facilitated transport and liquid membrane separations is reviewed and summarized, especially work reported since 1977 as mentioned in this paper, and the possibility of industrial application of liquid membrane technology is mentioned and the most important experimental techniques for liquid membrane research are discussed.
Abstract: The literature pertaining to facilitated transport and liquid membrane separations is reviewed and summarized, especially work reported since 1977. Liquid membranes of all geometries are discussed, including immobilized liquid membranes and liquid surfactant or emulsion liquid membranes. Emphasis is placed on facilitated, or carrier-mediated transport in both configurations although other mechanisms such as coupled-transport and transport due to solubility differences are discussed. Mathematical modeling and analytical solutions for facilitated transport models are summarized. The possibility of industrial application of liquid membrane technology is mentioned and the most important experimental techniques for liquid membrane research are discussed. Also, directions for future research are recommended.
141 citations
TL;DR: In this paper, a liquid membrane process is developed for application to a number of industrial waste treatment problems and the results of laboratory and pilot plant studies show that liquid membranes are capable of reducing the levels of NH/sub 4//sup +/, Cr/sup 6 +/, Cu/sup 2 +/, Hg/sup 3 +/, and Cd/sup 4 +/
Abstract: A liquid membrane process is being developed for application to a number of industrial waste treatment problems. The results of laboratory and pilot plant studies show that liquid membranes are capable of reducing the levels of NH/sub 4//sup +/, Cr/sup 6 +/, Cu/sup 2 +/, Hg/sup 2 +/, and Cd/sup 2 +/ from several hundred ppM to less than 1 ppM under batch or continuous flow conditions.
126 citations
TL;DR: In this paper, a liquid membrane (MEM) method for separation of chromium(VI) from simulated waste water has been described, and the effect of the variation of the oil-membrane constituents and different types of chemical reactions at the II/I interface using aqueous solutions of various strippants (internal phase) has been studied for a critical appraisal of the efficiency of the process.
Abstract: A liquid membrane (multiple emulsion, water-in-oil-in-water (WIII/OII/WI)) method of separation of chromium(VI) from simulated waste water has been described. The effect of the variation of the oil-membrane constituents and different types of chemical reactions at the II/I interface using aqueous solutions of various strippants (internal phase) have been studied for a critical appraisal of the efficiency of the process. Among others, reductions have been found to be most effective in lowering the chromium(VI) content in waste water below the toxic limit (0.05 ppm, suggested by the World Health Organisation). The ion exchange behaviour of the carriers in the membrane and coupled countertransport have been suggested to be the main cause of chromium(VI) transport. The application of the reaction site model has been found to be reasonably justified.
126 citations