Supported liquid membranes improvement

Supported liquid membranes, consisting of an organic solution of -octyl(phenyl)-A,iV-diisobutylcarbamoylmethylpho-sphine oxide (CMPO) and tributyl-phosphate (TBP) in decalin, were capable of selective separation and concentration of actinide and lanthanide ions from aqueous nitrate feed solutions and from synthetic nuclear wastes where the strip solution is a mixture of formic acid (FA) and hydroxylammonium formate (HAF) [106,107]. TBP is added to CMPO to improve its solubility in aliphatic diluents. Although low concentration of nitric acid was initially used as the strippant solution, a gradual... 

Supported liquid membrane stability and lifetime limit the industrial application of this separation technique. Therefore, the stability of these membranes needs to be enhanced drastically. A proper choice of the operating and membrane composition factors might improve the lifetime of SLM systems. 

Saito, T. (1992). Deterioration of hquid membrane and its improvement in permeation transport of Zn(II) ion through a supported liquid membrane containing a Bath-ocuproine. Sep. Sci. Technol., 27, 1-9. 

Other techniques have been developed to improve upon SX among them of particular interest are liquid membranes with the main t)q)es of these membranes being bulk liquid membranes (BLMs), emulsion hquid membranes (ELMs) and supported liquid membranes (SLMs) (Kolev, 2005) (Fig. 10.1). While these all have advantages compared to SX systems, they have not yet achieved wide eommercial acceptance. The following paragraphs present a brief deseription of the principles utilized by BLMs, ELMs and SLMs. For more information about liquid membranes please refer also to Chapters 7 and 8 of this volume. 

In Chapter 25, Misra and Gill survey the applications of supported liquid membranes in separations of transition metal, lanthanides, and actinides from aqueous solutions. Choices of membrane material and solvent which improve the membrane stability in a SLM system are discussed. A few pilot-scale studies of SLM processes are described which show the potential for large-scale utilization in the future. 

In our laboratories, research and development studies have been conducted on the separation of uranium and various lanthanides by common extractants (carriers) and of actinides by crown ether carriers using different types of liquid membrane systems. Also our studies have been directed toward determining optimal support systems for supported liquid membranes (SLM) which may offer improved flux... 

The use of liquid membranes in analytical applications has increased in the last 20 years. As is described extensively elsewhere (Chapter 15), a liquid membrane consists of a water-immiscible organic solvent that includes a solvent extraction extractant, often with a diluent and phase modifier, impregnated in a microporous hydrophobic polymeric support and placed between two aqueous phases. One of these aqueous phases (donor phase) contains the analyte to be transported through the membrane to the second (acceptor) phase. The possibility of incorporating different specific reagents in the liquid membranes allows the separation of the analyte from the matrix to be improved and thus to achieve higher selectivity. 

In this context, facilitated transport of a specific gas molecule through modified polymeric membranes or liquid membranes containing mobile carriers can be employed to improve single bulk material (polymer) properties. Ceramic material is not traditionally employed as hquid membrane support due to their high cost, use of not aggressive compounds to be separated and mild operating conditions. 

Hemdndez-Femdndez FJ, de los Rfos AP, TomSs-Alonso F, G6mez D, Vfllora G (2009) Improvement in the separation efficiency of transesterification reaction compounds by the use of supported ionic liquid membranes based on the dicyanamide anion. Desalination 244 122-129... 

To date, many kinds of CO2 separation membranes have been reported, including polymeric membranes, composite membranes, and facilitated transport membranes. Further improvements in membrane performance depend on effective CO2 separation materials, and one candidate is ILs. It has been reported that ILs have good CO2 selectivity, suggesting that they may be a possibility for the development of new CO2 separation materials. Since ILs are liquid at room temperature, it is necessary to affix ILs to appropriate support materials. Supported IL membranes have been prepared by impregnation of commercial porous polymer films with 1-n-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf2N]) and have obtained good C02/He separation properties [40]. Recently, electrospun Nafion/polyethylene oxide (PEO)-supported IL membranes were fabricated for CO2 separation [41]. In this composite membrane, the electrospun Nafion/PEO material acted as a gutter layer for ILs and PEO was added to form clean nanofibrous... 

SLMs are perous membranes with the peres saturated with a solvent mixture. SLMs suffer significant solvent loss due to volatilization when conventional solvents are employed as supported liquid. The used of ILs as the immobilized phase within the pores of the membranes is the improving in the membrane stability and their performance do not dep>end of the water paesence (a. Scovazzo et al., 2009). Supported ionic liquid membranes (SILMs) increase the efficiency and selectivity of separation resp>ect to non-supp>orted liquid membranes because the higher area of contact IL-gases. 

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