Separation and Purification Technology 16 ( 1999 ) 235–241 Highly selective and efficient membrane transport of palladium as PdCl 2- 4 ion using NH+ 4 -dibenzyldiaza-18-crown-6 as carrier Gholamreza Khayatian, Mojtaba Shamsipur * Department of Chemistry, Razi University, Kermanshah, Iran Received 4 January 1999; received in revised form 7 January 1999; accepted for publication 12 March 1999 Abstract Ammonium–dibenzyldiaza-18-crown-6 complex was used as a highly efficient carrier for the uphill transport of palladium as PdCl 2- 4 complex ion through a chloroform bulk liquid membrane. By using thiocyanate as a metal ion acceptor in the receiving phase, the amount of palladium transported across the liquid membrane after 120 min was 92.2±1.4%. The selectivity and efficiency of palladium transport from aqueous solutions containing Tl +, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd 2+, Hg2+, Fe3+ and Cr3+ were investigated. In the presence of EDTA at pH 4.7 as a suitable masking agent in the source phase, the interfering effect of Hg2+ ion was diminished drastically. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Liquid membrane; NH+ 4 -dibenzyldiaza-18-crown-6 carrier; Palladium transport; PdCl 2- 4 anion; Thiocyanate 1. Introduction In recent years, increasing interest has been focused on liquid membrane methods for the selec- Due to the widespread use of palladium in tive separation and concentration of Pd 2+ ions different areas of science and technology, especially [9–20]. These are very useful methods for assessing as an exhaust catalyst and as a catalyst in the the partitioning of metal ions into and out of organic synthetic industry [1,2] on the one hand, organic membrane phase and are of special impor- and the toxicity of Pd( II ) compounds to mammals, tance in separation science, medicine, water purifi- microflora, fish and higher plants [3,4] on the cation and metallurgy [21,22]. The liquid other, the separation, concentration and determi- membrane systems used for palladium separation nation of palladium is of increasing interest. were of bulk [9], emulsion [10–15] and supported During the past three decades, solvent extraction types [16–20]. has been widely used for the separation of platinum In recent years we have been involved in the metals [5–8]. The low hydration tendency of the design and preparation of bulk liquid membrane chloro-complex of Pd(II ) has been found to play systems containing some crown ether derivatives an important role in its extraction from acidic for selective and efficient transport of a variety of solutions by an ion exchange mechanism with transition and heavy metal ions such as Cu2+ bulky amines as suitable organic bases [8]. [23,24], Zn2+ [25,26], Hg2+ [24], Pb2+ [28,29], Cd 2+ [30] and Ag+ ions [31]. In this paper we report a new, highly efficient and selective * Corresponding author. Tel.: +98-831-94066; fax: +98-831-831618. liquid membrane system containing ammonium– 1383-5866/99/$ – see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S1383-5866(99)00015-5