Journal of Membrane Science 215 (2003) 87–93 Selective transport of silver ion through a supported liquid membrane using some mixed aza-thioether crowns containing a 1,10-phenanthroline sub-unit as specific ion carriers Mojtaba Shamsipur a,∗ , Sayed Yahya Kazemi a , Gholamhasan Azimi a , Sayed Siavash Madaeni b , Vito Lippolis c , Alessandra Garau c , Francesco Isaia c a Department of Chemistry, Razi University, Kermanshah, Iran b Department of Chemical Engineering, Razi University, Kermanshah, Iran c Dipartimento di Chimica Inorganica ed Analitica, Università di Cagliari, S.S. 554 Bivio per Sestu, 09042 Monserrato (CA), Italy Received 29 May 2002; received in revised form 12 November 2002; accepted 4 December 2002 Abstract A new supported liquid membrane (SLM) system for the selective transport of silver ion is introduced. The SLM used is a thin porous membrane impregnated with a recently synthesized mixed aza-thioether crown containing a 1,10-phenanthroline sub-unit dissolved in nitrophenyl octyl ether. In the presence of thiosulfate as a metal ion acceptor in the strip solution, the transport of silver occurs almost quantitatively after 3 h. The selectivity and efficiency of silver transport from aqueous solution containing excess amounts of Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ Co 2+ , Ni 2+ , Cu 2+ Zn 2+ , Pb 2+ , Cd 2+ and Hg 2+ ions were investigated. © 2003 Elsevier Science B.V. All rights reserved. Keywords: SLM; Silver transport; 1,10-Phenanthroline-substituted thioethers; Thiosulfate 1. Introduction During the past two decades, there has been in- creasing interest in the possible use of artificial mem- branes in specific separation procedures of biological and industrial importance [1–3]. Macrocyclic crown ethers show excellent cation selectivity when used as ion carrier in liquid membrane studies of alkali and alkaline earth cations [2–4]. In recent years, sup- ported liquid membranes (SLMs) have been used ex- tensively as alternatives to liquid–liquid extraction and other (membrane) separation techniques for the se- ∗ Corresponding author. Tel.: +98-831-723307; fax: +98-831-728439. E-mail address: mshamsipur@yahoo.com (M. Shamsipur). lective and efficient removal of ions or neutral com- pounds from dilute solution [5–13]. The advantages of SLMs over conventional solvent extraction processes include the simplicity of operation, economical uti- lization of the extractant and lack of solvent entertain- ment. The SLM technique involves the use of a thin impregnated microporous membrane separating feed and stripping solutions. The membrane is impregnated with a water-immiscible solvent containing a suitable lipophilic ligand as ion carrier. The complexing ability of ordinary crown ethers toward soft heavy metal ion is quite low [14]. This problem has been overcome by the substitution of some oxygen atoms of crown ethers by nitrogen or sulfur atoms, which results in a considerable increase in the stability of cations such as Ag + , Tl + and Hg 2+ 0376-7388/03/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0376-7388(02)00604-X