Stability of Supported Liquid Membranes: State of the Art

Abstract

This paper presents a state of art review on the stability of supported liquid membranes (SLM). The backgrounds of SLM instability phenomena are presented, and various mechanisms for explaining these phenomena are treated in detail. Several suggestions for stability improvement are discussed.

Selective Transport of Silver Ion through a Supported Liquid Membrane Using Hexathia-18-Crown-6 as Carrier

“…Nevertheless, the stability of the SLM system proposed can be enhanced not only by increasing the hydrophobic character of the membrane solvent, but also by employing such known methods as the re-impregnation of the support, use of sandwich SLMs and gelation of the SLMs. 20 Based on the results obtained, the silver ion transported across the SLM used can be explained as follows: (1) The extraction of the charged species from feed solution into the hydrophobic membrane is accomplished by the presence of the host carrier HT18C6, ion-paired with picrate as a suitable counter anion; the resulting neutral complexed ion pair distributes preferentially into the organic membrane. (2) The ion pair thus formed diffuses across the membrane.…”

“…This is mainly due to the gradual bleeding of carrier and/or membrane solvent from the organic phase, which can have an influence on both flux and selectivity of the membrane. 20 In order to investigate the stability of the SLM proposed, a single membrane was used for several transport experiments after keeping it for varying intervals of time in water. The results are illustrated in Fig.…”

“…In recent years, the supported liquid membrane systems have received considerable attention as an alternative separation technique for metal ions from dilute solutions. [16][17][18][19][20][21][22][23] The most important advantages of SLM over solvent extractions include very low solvent hold-up, simplicity of operation and low investment and operating costs.In recent years, we have been involved in the design and preparation of bulk liquid membrane [24][25][26][27][28][29][30] and SLM systems 23 for the efficient and selective transport of some transition and heavy metal ions using different crown ether derivatives as ion carriers. In this paper, we report a new SLM system containing hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether (NPOE), immobilized in a thin polyvinyldifluoride (PVDF) film, for the transport of Ag + as a suitable ion-pair with picrate ion.…”

“…In recent years, the supported liquid membrane systems have received considerable attention as an alternative separation technique for metal ions from dilute solutions. [16][17][18][19][20][21][22][23] The most important advantages of SLM over solvent extractions include very low solvent hold-up, simplicity of operation and low investment and operating costs.…”

Understanding the influence of the ionic liquid composition and the surrounding phase nature on the stability of supported ionic liquid membranes

“…The instability of the organic liquid in the pores of the inert membrane as support reduces the period of utilization which has prevented its widespread use. [15][16][17][18][19][20][21][22][23][24] Various mechanisms have been proposed to explain the SLM instability: the loss of organic phase from the membrane through dissolution into the surrounding liquids, liquid migration due to pressure differences or osmotic pressure gradients, 20,25 and emulsion formation 26 or attrition of the organic film 21,26 due to lateral shear forces. Consequently, the SLM stability may also be affected by the chemical nature and textural properties of polymeric support, the type of organic solvent used in the studied process, the preparation method, 27,28 etc., while the time periods for observed instability varies from a few hours to several months depending on the system.…”