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

Abstract

The silver content of environmental samples is increased with the increasing use of silver compounds and silver-containing preparations in industry and in medicine. 1,2 Silver can enter the environment via industrial waters because it is often as an impurity in copper, zinc, arsenic and antimony ores. 3 It is noteworthy that recent information about the interaction of silver with essential nutrients, especially Se, Cu, vitamin E and vitamin B12, have focused attention on potentially toxic nutrients. 4,5 Thus, separation, concentration and sensitive determination of Ag + ion are of increasing interest.Liquid-liquid extraction and separation of silver in the presence of classical 6-9 and macrocyclic ligands 10-15 is frequently reported in the literature. However, a serious limitation in traditional solvent extraction processes is that a large inventory of high purity solvents (and carriers) is required, especially when processing dilute solutions. An additional concern is the disposal of the solvents used, which creates a severe environmental problem. 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 the presence of thiosulfate as a proper metal ion acceptor in the strip solution, highly selective and efficient transport of silver occurs via formation of a silver-HT18C6-picrate complexed ion pair. To the best of our knowledge, this is the first report on the use of a thia-substituted crown ether in an SLM system for the selective transport of Ag + ions. Experimental ReagentsThe crown ether derivative HT18C6 was purchased from Fluka Chemical Company and used as received. Reagent grade nitrophenyloctyl ether (NPOE, Fluka) was used as the organic membrane solvent. Silver nitrate, picric acid and the nitrate salts of all other cations used were of the highest purity available from either Merck or Fluka Chemical Companies and were used without further purification except for vacuum drying over P2O5. Doubly distilled deionized water was used throughout. ApparatusThe atomic absorption spectrophotometer used for the measurement of metal ion concentrations in the feed and stripping phases was a Shimadzu AA-760 instrument. The liquid membrane cell used for this study was fabricated from Perspex mat...

Hg2+‐Selective Membrane Potentiometric Sensor Based on a Recently Synthesized Mercapto Compound

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PNP-16-crown-6 derivatives as ion carriers for Zn(II), Cd(II) and Pb(II) transport across polymer inclusion membranes

“…Except with Hg 2+ , none of the cations used interfere with the Ag + transport. In other paper of Shamspiur et al [9], the results of selective transport of silver(I) across a SLM with hexathia-18-crown-6 as carrier were shown. The transport of silver(I) occurs almost quantitatively.…”

Highly selective transport of silver ion through a supported liquid membrane using calix[4]pyrroles as suitable ion carriers

“…In our previous works, we have transported efficiently silver ion through the bulk and supported liquid membranes using victoria blue, hexathia-18-crown-6 and some recently synthesized mixed aza-thioether crowns containing 1,10-phenanthroline sub-unit as carriers [15,17,[35][36][37].…”